"Swan Bay & Catchment"
Swan Bay & Catchment Swan Bay – A Bay within a Bay Swan Bay is a shallow seagrass meadow, much of which is exposed to the air at low tide. It is located immediately north of Queenscliff in Victoria and south-west of St. Leonard's on the western shores of Port Phillip Bay. Swan Bay is an important part of the Port Phillip Heads Marine National Park, a highly protected area that is like a National Park for marine environments. The Port Phillip Heads Marine National Park includes rocky reefs around Point Lonsdale and Point Nepean, the important intertidal habitats of Mud Islands and Swan Bay, the deep section of the bay at Portsea Hole, and the artificial reef structure at Popes Eye. Swan Bay is almost completely surrounded by land. Apart from two "gaps" (the channel entrances which connect it to Port Phillip Bay), it is protected from all but the strongest winds by the Bellarine hills to the north and west, by Swan Island, Sand Island and Edwards Point to the east and by a thin band of sand dunes to the south. Swan Bay is usually calm. Waves are rarely seen and currents over most of the Bay are weak. The floor of Swan Bay is a mixture of mud, sand and shell ggrit, providing ideal growing conditions for many types of seagrasses and algae. Below the mud surface, small animals and plants go about the business of survival, while above them the underwater seagrasses teem with small fish, shrimp and cuttles. At low tide, exposed mudflats provide feeding and roosting areas for birds of all shapes and sizes. As the tide rises again, fish, crabs, worms, snails, water rats and birds all converge to eat and be eaten. Around the fringing shores, saltmarsh plants eke seek out a living in the thick, airless mud. The Swan Bay Catchment Swan Bay is surrounded by low hills which drain into the bay. The area from which the water drains is called the catchment (also known as a watershed). This is an important part of the bay system as it nd has a large influence on the bay and the animals and plants that live there. Swampy grasslands behind the saltmarsh give way to grassed or cropped paddocks, many of which cradle creek beds, small swamps and bogs, and smaller drainage lines. The roadways of the catchment store most of what remains of the vegetation of the past and it is along these narrow tree corridors that some native animals can still be found. People are a prominent part of the catchment. Most live in Ocean Grove, Point Lonsdale, Queenscliff or St. Leonard's, and have changed the landscape significantly. Many people now live on small rural blocks around Wallington, or have larger properties on which they raise cattle, sheep, alpacas or horses, and grow potatoes, sunflowers, grapes, berries or grass hay. From Mount Bellarine, the highest point in the catchment, the view to Swan Bay is one of open spaces, cCriss-crossed by tree-lined roads, dotted with houses, with Swan Bay sitting like a shimmering pond at the foot of the catchment. Vital Statistics Characteristic Notes Location LAT 38.25 LONG 144.67 Bay area 3000ha at high tide Catchment area Approximately 170 km2 Mudflat area 700-1000ha at low tide Creeks 9 in total, 2 named: Yarram Creek and Five Mile Creek No. of types of fish 44 No. of types of birds 192 Numbers of migratory Over 10,000 each summer birds Highest hill in the Mt. Bellarine, 152m above sea level Catchment Rainfall Lowest average 41 mm in January, March & December Highest average 77mm, May Shipwrecks 18 have occurred around the Bay; 9 have been found Management Parks Victoria Responsibilities Department of Sustainability and Environment Department of Defence Borough of Queenscliffe Landowners Native animals 262 including fishes Introduced animals 16 Brush-tailed Phascogale Native animals presumed locally Eastern Barred Bandicoot extinct Swamp Wallaby Less than 10% of original cover Native plants 252 on surrounding shores; many more throughout catchment 205 naturalised around shoreline, Introduced plants more throughout catchment and in residential gardens History The area we now know as Swan Bay wasn't always a bay. In fact, the original people to live in the catchment, the Wathaurong, told stories about the time before the bay had water in it. The Wathaurong and their ancestors have lived on the Bellarine Peninsula for tens of thousands of years; Swan Bay is only a few thousand years old. Many different events in the recent history of planet Earth have influenced the nature of Swan Bay. Many of these have to do with the climate. In the past, it has been both hotter and colder than it is these days, and these different climatic conditions have had direct influences on today's Swan Bay. When the world cools down, the oceans change: they shrink because they are colder. (Believe it or not, the contents of a glass of water will take up less space when the water is cold than when the water is hot!) It is hard to observe this phenomenon with a small amount of water, but when the world's oceans cool down, the effect can be drastic. Water is also "taken up" by polar ice sheets which extend much further than in today's warmer times, effectively "sucking" the sea towards Antarctica and the Arctic. When the sea shrinks and the sea level drops, the coast advances further out "to sea". The sea level has dropped in our part of the world a number of times. When the world heats up, the opposite occurs - the oceans swell, water is released from polar ice and the sea level rises. This rise in sea level has also happened in our region. Swan Bay's shoreline boundaries give us some idea of some of the sea levels which our coast has experienced in the recent past. Figures 1 and 2 illustrate some likely shoreline formations in the area. The western shoreline of Swan Bay was once a shoreline of Port Phillip, before the southern dunes and most of Swan Bay's islands were formed. This shoreline would have been a high energy shoreline, much like the rocky parts of the shoreline of Lonsdale Bight. This shoreline would have been active when the sea level was higher than it is today. As the climate cooled and the seas shrank, the sea level gradually dropped; the area which was to become Swan Bay became dry. Sand dunes formed between Queenscliff and Point Lonsdale and the sand islands north of Queenscliff grew. Over thousands of years, the seas warmed again, rising to around their present height. The dry basin north of the southern sand dunes filled with water and a shallow bay was formed. We now call it Swan Bay. A Geological History of Swan Bay 150 million years ago Jurassic Australia separates from Gondwana. 26 million years ago High sea levels deposit 30 million years ago limestone, sandstone and Tertiary Molten lava from a volcanic eruption mudstone over most of the (possibly at Mount Bellarine) flows over catchment. the north-west part of the Swan Bay catchment and solidifies into basalt. 7 million years ago 1 million years ago Seas recede and creeks a n d l a n d An ice age causes the sea level to r e j u v e n a t e . Stream flows deposit drop. Shells and skeletons of marine f e r r u gi n o u s sa n d s a n d sandy clays. life are exposed to the wind, which The scarp encountered when approaching blows them around. As they break up, Pt. Lonsdale from either Geelong or Ocean they are mixed in with small stones Grove marks this old Pliocene shoreline. and together form sand. The sand is blown along and piles up into large sand dunes. Rain soaking through the sand Quaternary dissolves some of the sand and carries it downwards. This cements other sand grains together, forming dune rock. 20 thousand years ago Polar ice caps melt and seas rise again, covering dune rock. Queenscliff and Pt. 40 thousand years ago Lonsdale are left exposed as islands (see People move into area, utilizing fig. 1). molluscs, fish and aquatic plants. Less than 3 thousand years ago 3-5 thousand years ago Sea levels fall in a series of Mid-Holocene sea levels are about 6 stages. Dunes start to form along metres higher than present low tide level. coastline. Area behind dunes is now low A line of aeolianite reefs form a bar off the and swampy. Swan Island, Duck Island coast. Lagoonal shell beds are laid down and Sand Island form from sandy inside the reefs from Ocean Grove through ridges and silty material (see fig.2). Lake Victoria and including Swan Bay. (see Successive sand spits extend south fig. 1) from St. Leonard's Figure 1. Map of the Point Lonsdale - Queenscliff area, at the time of the mid-Holocene higher sea- level. Dune limestone (aeolianite) which formed in the Pleistocene Ice Age became submerged, leaving Queenscliff and Pt. Lonsdale exposed as islands with a limestone reef located offshore. Shell beds were laid down in the quieter waters of the lagoon. Figure 2. Present day shoreline. After the sea level fell, Queenscliff and Pt. Lonsdale were connected by sand dunes - what we now call "The Narrows". Wathaurong – the Original Inhabitants of Swan Bay The Wathaurong were a clan of people who lived not only on the Bellarine Peninsula, but also throughout their extensive territory from the Werribee River to Ballarat and down into the Otways. As part of the Wathaurong's territory, the Swan Bay catchment was actively managed by them. The clan "lived lightly", moving constantly throughout their territory, collecting enough food, housing material and clothing to live well without causing damage to the land that kept them alive. Evidence of Wathaurong use of the catchment can be found in middens, mounds of shells and charcoal which represent campsites and cooking fires. The structure of some of the catchment's more natural vegetation is also evidence of Wathaurong management, as the principal management tool was fire. Using light burns (now referred to as controlled burns) in late summer, these people promoted the regeneration of many food plants. Burning patches of the catchment in this way also ensured that animals would be attracted to new growth, making them easier to hunt. The abundance of food produced by this management style allowed the Wathaurong, like all Koories, to collect enough food to last an entire day in just 3 or 4 hours. Compare this to many present-day Australians who work long hours in order to feed their families and still never seem to have enough - it would appear that the quality of life of the catchment's residents has certainly dropped since the arrival of the British. The clan consisted of a number of families, and in 1836 there were approximately 700 people in the clan. Seventeen years later, only thirty five Wathaurong had survived the organised massacres and introduced diseases of the Europeans. The elimination of traditional foods as a result of European land management styles further debilitated the clan. The technological dominance and cultural arrogance of many European settlers and their descendants - particularly of those in authority - saw almost all Koories in southern Victoria moved into missions. The closest mission to Geelong was at Birregurra. At such missions, Europeans kept Koories away from their traditional lands, disrupting cultural, management and religious traditions, which were tens of thousands of years old. European colonization of the catchment Whilst legends of Spanish pirates can still be heard around Queenscliff, the first non-indigenous people known with certainty to have visited the Bellarine Peninsula were the crew of the Investigator, a British ship captained by the voyager Matthew Flinders. Flinders landed at Indented Head on May 1st, 1802, and other members of his crew explored the southern end of Swan Bay, passing through the shifting sand spit, known to the Wathaurong as "whoorangalook', on the following day. Today, the area is known as the Cut. It was not until some years later, when St. Leopards, Point Lonsdale and Queenscliff became established settlement towns, that the European "stamp" of habitat modification and cultural dominance became evident throughout the catchment. As Melbourne and Geelong grew, the demand for fuel (wood) and wattle bark - used in the tanning process - also grew. The Bellarine Peninsula (or the Wedge Hills, as it was then known) provided both of these commodities to Melbourne for many years. The resulting landscape was probably similar to the one we can see today. Once the supplies of old sheoaks (for wood) and wattles (for bark) had dwindled, other activities began in earnest. The catchment had a flourishing wine-making industry in the early 1800s, but this succumbed to disease and all vineyards had to be burnt. The richer soils of the upper and western catchment had (and still have) orchards established, although many of these areas now produce potatoes and other annual crops. The catchment was even famous throughout the "colony" for its onions! Despite Swan Bay's shallow sand banks, small boats were able to navigate through its northern waters and a number of jetties were constructed to provide loading points for goods. Andersons Road, which used to run all the way from Geelong to the Swan Bay shore, was an important route for the transport of many products, especially wattle bark, as it had its own jetty - in the same way as Swan Bay Road does today. The catchment continues to be a resource, mainly for agricultural activities. The "Beautiful country, thickly wooded" which was described in 1803 is gone and has been replaced by a mosaic of agricultural activity. The cumulative effects of these activities have, in places, resulted in the decline of soils, loss of biodiversity and a loss of amenity. They have also enabled many people to feed their families. Many people now living in the catchment or associated with Swan Bay realise the enormous potential of the catchment to support well-managed, sustainable agriculture, which includes provision of habitat and protection of biodiversity. The past may be gone, but a sustainable future is still possible. Swan Bay Habitats Swan Bay is more than just water. It is a complex set of interactions between its physical characteristics (things like air, water, salt and mud) and its biological characteristics (such as plants, animals, algae, fungi and bacteria). The way these characteristics interact is known as ecology. Particular combinations of physical and biological characteristics result in what we call habitats - the places where things live. Different habitats seem to suit different living things. For example, pipefish (common seagrass fish) prefer seagrass habitats, perhaps because these habitats are sheltered from strong currents, provide camouflage and also support animals that pipefish can eat. What suits one pipefish will probably suit another, so there is a good chance that two pipefish will bump into each other - an important consideration if there is to be another generation of pipefish! There are many different habitats which occur throughout the catchment. They are not restricted to Swan Bay, but include habitats found on farms, in sand dunes, on roadsides and in back yards. Although it is easy for us to put habitats into neat categories, in reality they are linked. Habitats overlap. Because many animals and plants can use more than just one habitat, connections are made when animals travel from one habitat to another or when a particular plant grows over a wide area of the catchment. These connections sometimes enable living things to use slightly different habitats when, for example, one habitat is altered drastically (such as may occur in a bushfire, or when trees are cleared to build houses). The same connections also enable damaging environmental impacts to be spread from one habitat to another. Whilst the distinctions are for our convenience (ie, they do not really exist in nature), they provide a simple way of coming to basic grips with the diversity of plants, animals and systems which combine to give the catchment its unique ecology. The main habitats are: Dune Wetlands, Lakes & Ponds; Creeks; Saltmarshes; Seagrass Meadows; Intertidal Mudflats; and People-based Habitats. Habitat 1: Dune Wetlands, Lakes and Ponds Where are they? A chain of wetlands and lakes stretches from the Begola Wetlands at Ocean Grove to the south-western corner of Swan Bay. These wetlands lie between the coastal sand dunes and the ancient (pre-Ice Age) seashore at the bottom of Marcus Hill. The wetlands initially drain towards Lake Victoria. From there, water moves through a series of ponds before finally draining into Swan Bay. Other significant wetlands in the catchment occur around the northern shores of Swan Bay, where creeks flow out onto wide, shallow swamps and into small ponds before draining into Swan Bay itself. At the mouth of Yarram Creek, another "pond" is present. A series of small wetlands (only 25m2 25m2 each - almost puddle size!) also occurs at the very base of Formatted: Superscript Marcus Hill. These may be seen as you travel along the Bellarine Highway from Swan Bay to Geelong. Why are they there? The southern wetlands of the catchment lie in the "valley" which separates Marcus Hill from the Point Lonsdale-Ocean Grove sand dunes. The thick layers of shell grit underneath the wetlands are less porous than sand, so water cannot drain straight through. Over time, though, water does percolate down into the shell grit and continues to travel slowly towards Swan Bay. The diagram illustrates how the Begola Wetlands were formed. The puddles at the base of Marcus Hill also lie in a valley; the valley between the hill and a very old, low sand dune. This sand dune was being used for growing potatoes and sheep. The wetlands around Swan Bay's northern shores are there because the land is quite flat. Creeks which drain the area to the east of Mt. Bellarine and Blacks Hill flow onto these flats, creating broad swampy areas. Local people tell of the time when the swamps were far bigger than they are today and were dotted with old redgum and yellowgum trees. Today, these swamps are rare, mainly because the creeks have been dammed higher up in the catchment, preventing the water from reaching the flat areas at the base of the catchment. Structure of Begola Wetlands. Begola Wetlands receives most of its water from the street gutters in and around Collendina. Rubbish that has been washed down stormwater drains is prevented from entering Begola Wetlands by litter traps. -Begola is the first link in the chain of wetlands that extends east from Ocean Grove to Swan Bay. BegolaIt was originally an ephemeral wetland, dry in summer and autumn and wet in winter and spring. The construction of a retaining wall at the east end has enabled the wetland to permanently hold water. Lonsdale Lakes Wildlife Reserves include Lake Victoria and other wetlands in the southern part of the catchment. Lake Victoria provides a bad weather refuge for many wader birds in the Swan Bay - Mud Islands area. What grows there? The wetlands of the catchment provide quite different habitat to other areas, and freshwater plants are important to animals and to the water quality of the ponds. Plants such as reeds, rushes and sedges grow around pond margins, with many other less conspicuous plants growing under the water and among the larger plants. Animals in the wetlands Many animals, both aquatic and terrestrial, rely on the freshwater wetlands of the catchment. These animals include frogs, Black Swans, White-faced Herons, ducks, ibises, spoonbills, Greenshanks and Japanese Snipe. These animals have all been seen in one of the catchment's smaller wetlands - the Begola Wetlands stormwater channel. This channel is not a natural feature of the catchment, as it was dug to carry stormwater away from Begola and the Collendina housing area to Lake Victoria and, eventually, Swan Bay. Over the years this earth channel became a wetland home to all of the animals listed above, some of which are rare migratory waders. It is now recognised as an important freshwater habitat and an integral part of the catchment's wildlife reserves. Other wetlands which are near remnant vegetation provide important feeding and drinking areas for animals. The wetlands at the eastern end of Andersons Road in the northern part of the catchment attract insects which are eaten by frogs and by bats at dawn and dusk. The trees around the wetland provide shelter and food for the bats, for small mammals and for birds. At least five different types of frogs have been found within the catchment's wetlands. These have included: the Growling Grass Frog, Litoria raniformis Formatted: Font: Italic the Spotted Marsh Frog, Limnodynastes tasmaniensis Formatted: Font: Italic the Striped Marsh Frog, Limnodynastes peroni Formatted: Font: Italic the Pobblebonk (Banjo) Frog, Limnodynastes dumerili and Formatted: Font: Italic the Common Froglet, Ranidella signifera. Formatted: Font: Italic Frogs are very sensitive to environmental change and pollution levels, and are in decline in many parts of the world. As they are thriving in a number of the catchment's wetlands, they are an indication that the quality of the some of the catchment's freshwater wetlands is still high. Conservation of the habitats of these frogs requires all catchment residents to be mindful of issues affecting water quality throughout the Swan Bay catchment. In 1992, local resident and naturalist, Bill Gunn, alerted the then Bellarine Rural City Council to the importance of the Begola channel to local wildlife, as there were plans to replace the earth channel with a concrete drain to simplify maintenance. Despite frogs being protected under the 1975 Wildlife Act the concreting scheme went ahead without an environmental impact study. It was a further two years before Bill's efforts saw the drain construction halt just 250 metres short of its proposed length. Links to the Swan Bay catchment The portion of the catchment extending from Begola to Swan Bay is swampy, but water flows slowly through the lakes, channels and ponds there, eventually reaching Swan Bay. The largest lake, Lake Victoria, together with two other smaller lakes, makes up the Lonsdale Lakes Wildlife Reserves.These lakes are linked by surface drainage and by underground soaks. If water moves slowly through this system, a kind of natural filtration can take place. The soil, plants and microscopic life in the water all act as filters, removing nutrients, small particles and other potentially harmful materials from the water. By the time the slow-moving water reaches Swan Bay (between Burnt Point and the Peninsula Railway), it would have passed through a great, natural filtering system. In the past, the water entering Swan Bay had been naturally filtered in this way. Recently, the level of Lake Victoria has been lowered to "dry out" low-lying urban areas in Point Lonsdale. A large channel, cut at the north eastern end of the Lake now drains Lake Victoria directly into ponds which then drain into Swan Bay. Further north, the few remaining swamps act as important filters of catchment runoff. The aquatic plants act as buffers between the catchment's freshwater runoff (which may contain excess nutrients and suspended matter) and the sensitive seagrass meadows of Swan Bay, into which the swamp waters then flow. These habitats provide the most direct routes for contaminants to enter Swan Bay and are themselves sensitive to the contaminants they may carry. Habitat 2: Saltmarshes Where are they? Saltmarsh communities - land plants and various animals that live in low energy intertidal zones - occur around the fringes of Swan Bay and its islands. Saltmarsh plants are usually herbs, low shrubs, grasses and sedges. Because different saltmarsh plants have different needs, they do not all grow in exactly the same places. Instead, these plants form "bands" or "zones" between the sea and the land, with different combinations of plants growing in different zones. The next page shows a typical cross-section of saltmarsh around Swan Bay. Why are they there? The history of saltmarshes is much more complex than most people think! Saltmarsh plants are able to survive in areas of salty, airless mud. The lower parts of the plants may be regularly covered by the salty sea and are occasionally covered by rainwater. Whilst the temperature of the soil (or mud) in which they grow usually changes slowly, the air temperature can change from almost freezing to almost scalding in a matter of a few hours. Life for saltmarsh plants is a serious thing! However, because they have particular adaptations to such hostile environments, saltmarsh plants are able to grow where few other plants can. Their key strength is their ability to tolerate salt. (Other areas of southern Australia, some far from the coast, also support saltmarsh plants, because their soils are also salty!. Some of Swan Bay's saltmarsh plants are found nowhere else in Victoria except the dry, salty Mallee country of the northwest desert.) What grows there? Beaded Glasswort, Shrubby Glasswort and Austral Seablite are saltmarsh plants which have fleshy or succulent water-storing leaves. The stored water dilutes the salt which would otherwise dry out and kill the plant. Other plants, such as the Common Boobialla, (found at the back of saltmarshes) have a waxy surface on their leaves. The wax reduces the amount of water lost through the leaves, thus preventing salt from building up too quickly. The seaward Beaded Chaffy Saw-sedge Beaded Chaffy Saw-sedge Common fringe of Glasswort, now appears on Glasswort, reappears on Boobialla, saltmarsh is Shrubby slightly higher Shrubby higher ground Sea Rush inundated at high Glasswort, ground. Shrubby Glasswort, with Tussock- and Knobby tide. Beaded Austral Glasswort, Bower Austral Seablite, grass and Club Rush Glasswort is Seablite, Spinach and low Creeping Australian Salt- occur at the found in the Seaberry growing plants Brookweed Grass. landward lower wetter Saltbush such as Creeping and Australian fringe of the areas, with Creeping Brookweed, Salt-grass are saltmarsh. Shrubby Brookweed Trailing found in this Glasswort and and Trailing Hemichroa, wetter depression. Austral Seablite Hemichroa are Southern Sea dominating the common in the Heath, Austral slightly raised lower, wetter Seablite and areas. area. Australian Salt-grass are also present. A cross-section of a saltmarsh community on the southern shores of Swan Bay Plants lose water through pores (called stomata) in their leaves. Both Creeping Brookweed and Southern Sea Heath have tiny needle- shaped leaves which effectively slow down the movement of water out of their stomata. Tussock-grass and Knobby Club Rush have leaf blades which are rolled inwards. This rolling helps protect the stomata and reduces water loss. Bower Spinach has tiny hairs on its leaves, which insulate the plant against heat, thus reducing water loss. The hairs also trap fresh water from rain or dew on leaf surfaces. Southern Sea Heath Animals in the saltmarshes Crabs, shrimps and small molluscs that live permanently in saltmarshes have adaptations that enable them to survive changing conditions. Other a ni ma l s m o v e i n a n d out of the sa lt ma r s h a c c or d i n g t o the tide cycles. At high tide, small fish feed and shelter in the saltmarsh fringe. At low tide waders such as White -faced herons move in to feed on invertebrates. Many tiny, colourful spiders live among saltmarsh plants. Skipper butterflies u s e C h a f f y S a w - s e d g e f o r t h e i r caterpillars. Grass Skinks shelter and f o r a g e a m o n g t u s s o c k - g r a s s e s , feeding during the day on insects and spiders. The rare and endangered Orange-bellied Parrot, which migrates from its breeding grounds in Tasmania each winter, feeds on the fruits of Beaded and Shrubby Glasswort. Chaffy Saw-sedge Links to the Swan Bay catchment Saltmarshes, fringing almost the entire Swan Bay shoreline, are important functional components of catchment ecology. From a "catchment down" perspective, they are the sites of filtration and biological treatment of many substances carried into them, either rapidly by creeks or gradually by surface water or ground water movement. From a "bay up" perspective, they act as an important factory, trapping drifting algae, seagrass and other matter from Swan Bay and converting it into living plant matter which is used by intertidal and terrestrial animals. In these ways, saltmarshes are an important interface between sea and land - acting as a selective filter which allows materials and energy to flow freely up into the catchment, while at the same time restricting the travel of materials back into the sea. As part of the catchment's mosaic of vegetation and habitat types, saltmarshes are an important storehouse of biological diversity, not only for the variety of rare plants which form the basis of the saltmarshes, but also for the accompanying marine, intertidal and terrestrial animals which rely on saltmarshes as their link between land and sea. Habitat 3: Seagrass meadows Where are they? Swan Bay's seagrass meadows used to cover the entire floor of the Bay. Whilst seasonal conditions (including the effects of swans) have always affected the actual area covered by seagrass, dramatic decreases in seagrass cover have been observed in recent years. Why are they there? Seagrasses are a group of land plants which have developed the ability to survive in the sea. Different types of seagrasses cope best with different conditions, so it is not surprising to find that Swan Bay's seagrasses are those which cope best with low energy environments. Other seagrasses may be found on high energy coasts such as around The Rip, but they are not found in Swan Bay. The relatively calm conditions, the sediment structure and the climatic conditions of the area provide the ideal growing place for the handful of different seagrasses found in Swan Bay. Even within the Bay, different microhabitats suit different seagrasses. What grows there? The deeper channels are the preferred growing place of the Tasman Grass Wrack Heterozostera Formatted: Font: Italic tasmanica whilst the shallow areas and intertidal mudflats support the shorter eelgrass Zostera Formatted: Font: Italic muelleri. The protected western shallows of the Bay, near McDonald's Jetty, appear to provide just the right conditions for yet another seagrass, the Paddle Wrack Halophila ovalis. In addition to the Formatted: Font: Italic seagrasses mentioned above, many other plants grow as part of the seagrass meadow community. Animals in the seagrass meadows Seagrass meadows are slowly being recognised for their importance as breeding, feeding and shelter sites for a large variety of marine life. Over 250 different types of living things, other than plants, can be found breeding, feeding or sheltering in Swan Bay's seagrass meadows. Some animals, such as pipefish, pygmy squid and flatworms, may spend their entire life in the seagrass of Swan Bay. Others, such the King George Whiting, travel long distances as tiny larvae to the shelter and food provided by Swan Bay's seagrasses. When they are older, the whiting may venture out into other habitats, but seagrass is an essential part of their life cycles. Larger animals - rays, for example, may spend some of their time out in Port Phillip, but use Swan Bay's seagrass meadows as their high tide feeding grounds. Those people keen enough to spend some time knee-deep in Swan Bay invariably come away overawed by the sheer amount of life which can be found amongst the seagrass. Shrimps, pill bugs, sand hoppers, squid, hardyheads, flounder and many types of snails and worms are commonly found in the one patch of seagrass - a truly remarkable amount of life packed into a small space. A Sand Hopper or Amphipod – a common Swan Bay seagrass animal Links to the Swan Bay catchment - and elsewhere... As Swan Bay's seagrass meadows are at the bottom of the catchment, the links are generally one-way; that is, catchment activities affect the seagrass but the seagrass has little effect on the catchment. For this reason, seagrass meadows are perhaps the habitats which are most open to damage from other sources. The experience of Westernport, where the vast majority of seagrass meadows disappeared over a matter of a few years as a result of inappropriate and unthinking land management, has shown that there is a direct link between the health of land and sea. The degraded condition of much of the catchment should therefore be of concern to anyone with an interest in Swan Bay. Although it has a rapid rate of growth, if damaged or removed, seagrass takes many years to recover. But who is (and should be) interested in Swan Bay? Apart from a few people who like to watch birds every now and then and a few others who spend their time studying the bay's invertebrate population, who else should be interested? Well, for starters anyone who... eats fish, squid and other marine life catches fish, squid or other marine life for fun or food catches fish, squid or other marine life for a living snorkels or dives in and around Port Phillip Bay... Why? Because Swan Bay's seagrass meadows are Port Phillip's largest seagrass meadows and seagrass meadows are homes to fish. King George Whiting is one fish which relies on seagrass - and a fish which many people rely on for food, fun and to make a living. Without seagrass, this fish will disappear from Port Phillip. Wider links The importance of Swan Bay's seagrass meadows does not stop with their links to fish and fishing. Swan Bay's seagrass also: supplies nutrients to plants and animals in the saltmarsh keeps Swan Bay's water clean provides food for Black Swans. Black Swans use seagrass roots as a direct food source. They have special grinding plates in their bills which crush seagrass roots. Ppartially digested seagrass passes out in swan faeces and is Formatted: Bullets and Numbering eaten by worms, sand hoppers and cunji (sea-squirts) provides an important, indirect source of food to many other animals. Few other herbivores feed directly on seagrass, but feed instead on epiphytic algae, or phytoplankton in the water. Decaying seagrass is broken down by bacteria to form detritus, a plentiful food supply for worms, snails and sand hoppers. These in turn are eaten by fish, crabs and birds maintains the structure of the intertidal mudbanks provides essential feeding areas for migratory wader birds. Even this short list shows that the importance of seagrass in Swan Bay cannot be overstated. Habitat 4: Intertidal mudflats Swan Bay's gently sloping muddy shores and "banks" in the middle of the Bay which are exposed at low tide are called mudflats. Bare, silty mud is not an easy place for plants to grow, but Swan Bay's seagrasses have managed to get a hold on the mudflats. The seagrass provides a home for other plants and animals. Together they form a mudflat community. Where are they? Swan Bay's intertidal mudflats are the most extensive in Port Phillip. On a low tide they may occupy over 70% of Swan Bay's area. The mudflats are scattered throughout most of Swan Bay, including some sections of the Bay's shoreline. Why are they there? The offshore mudflats are arranged in roughly parallel, sweeping curves. These curves, although changed over time as a result of tidal flows, give us an idea of the arrangement of the low sand dunes which existed in Swan Bay before it was flooded by the sea. The channels which run between these mudflats may be thought of as the swales between these flooded dunes. What grows there? The intertidal mudflats support the seagrass Zostera muelleri, a slow-growing seagrass which is able to tolerate the extremes of temperature and salinity it experiences in this habitat. Animals in the intertidal mudflats To most people, birds are the obvious users of this habitat. Whilst this is true, there are also large numbers of other creatures which call the mudflats home. Within the mudflats, a variety of microhabitats is used by animals, each of which has a different tolerance to local conditions. At low tide many types of crabs, marine snails and worms hide among the seagrass, burrow in the mud or shelter beneath rocks to protect themselves from predators and the drying effects of sun and wind. Dead seagrass, which washes up along the muddy shores or is stranded on mudflats within the Bay, provides shelter and moist conditions for tiny sandhoppers, crabs and marine snails. A low tide may reveal some of these animals, although most will be securely hidden in the mud or under seagrass. Intertidal snails may be seen grazing on the algae which covers seagrass leaves, and of course there will be birds feeding on the smaller animals. An intertidal mudflat food web The diagram below describes a simple mudflat food web. Tides, seasons and the migratory patterns of birds are some of the factors that affect the food sources available at any given time in a mudflat. A simple mudflat food web Habitat 5: People Habitats! Where are they? Although it retains a few small areas which could be described as "near-natural", much of the catchment has been heavily modified from the condition it was in prior to the British occupation. "Habitat modification" occurs when an important habitat component - such as a type of plant, or rocks, or soil structure - is altered. As much of the catchment is severely degraded from a habitat point of view (ie. many keystone resources have been removed), it is not surprising that some plants and animals which used to be common are now rare or locally extinct. But this doesn't mean that the catchment is a wasteland - in fact, far from it. There is still a catchment ecology, although it has changed drastically in a short time. Today's habitats are a mixture of old and new, bits & pieces - all combining to give an unique "flavour" to the area. These new habitats are all around us. Some examples are: paddocks backyards vineyards unburnt bush blocks farm dams roadsides drains and channels. Why are they there? These new habitats have all been created as a result of people. Most have been created for purposes other than habitat, but a number of animals and plants (both native and introduced) have taken advantage of them. One example is the common paddock. Whilst some paddocks in the northern catchment have displaced animals such as skinks, small mammals such as the tuan, many birds (including emus) and others, they have allowed magpies to flourish. Magpies, which prefer open grasslands with only a few trees dotted around the landscape, have undoubtedly increased their numbers considerably since land clearing began and paddocks became common in the catchment. Kookaburras, which require old trees for nesting and native grasses to house their food, have on the other hand declined considerably. If a particular habitat component is critical to the survival of an animal or plant, it is called a "keystone resource". When keystone resources are degraded, displaced or removed from habitats, then the animals and plants which rely on that resource become extinct in that area. What grows there? The plants of "people habitats" are as varied as the people who create them. Backyard habitats undoubtedly contain the highest diversity of plants, as they include plants which originated all over the world. Whilst some of these are notorious weeds which spread into other habitats, others act as important keystone resources for native animals. For example, the Spiny-cheeked Honey-eater feeds on the nectar of plants such as the Serrated Banksia, Kangaroo Paw, Pyramid Tree and honeysuckle. None of these plants grew in the catchment prior to the arrival of the British in Australia, but now they all form important habitat for these native animals. Food is not the only thing provided by plants to native animals. Simple things such as somewhere to perch, or roost, are often overlooked as being important, but such things as fence posts and the notorious furze bush are important keystone resources for birds of prey and finches! Even a backyard vegetable garden, or fruit trees, or a farm hedge, can be of great importance to the survival of native animals in the catchment. Whilst the enormous drop in variety and distribution of indigenous plants and animals which has occurred is shameful, the great variety of introduced plants has in some way lessened the impact on a number of local animals. New habitats are still far from ideal, but they are certainly better than a complete absence of trees and other plants altogether. Animals in other habitats If time and area permits, animals are extremely resourceful and are usually quick to take advantage of alternative food sources. Like the local plants, many local animals have become extinct as a direct result of the northern hemisphere style of land management which has been used in the catchment. Others, like the magpie and the raven seem to have benefited. Others, including birds of prey, small mammals (although most of these are gone), reptiles, frogs and any animals requiring scrubby undergrowth or hollow-bearing trees, continue to struggle for survival. Perhaps not surprisingly, most "people habitats" are dominated by introduced animals which successfully compete with native animals for food and shelter. Links to the Swan Bay catchment The nature of new habitats - created by people - generally means that people continue to maintain those habitats in a particular condition. For example, a short lawn is only short because it is repeatedly mown. Any such activity can be thought of as a management activity, because people are managing the land (or a particular habitat "feature", such as a building, or a car, or a garden) in a particular way to produce a particular thing - in this case, using a lawnmower to keep the grass short. Many management activities have little or no detrimental effects on the Swan Bay catchment. Mowing the lawn, for example, could hardly be described as a potential impact. However other management activities associated with these new habitats do have potential impacts, some of which could be quite serious. Some examples might be: Habitat Feature Action Potential Lawn Apply fertiliser Excess fertiliser may reach Swan Bay Vegetable Garden Apply insecticide Non-target species may be killed; toxins may accumulate in body tissues of native animals. Grazed stream bank Remove noxious furze bushes Reduces available habitat for rabbits, birds, foxes and other animals; expose soils to erosion. Roadside Slashing long grass prior to the Prevents native grasses from setting seed, summer fire period limiting potential for habitat expansion. Car Washing on the road or where Nutrients and detergents can enter the Bay water can drain into the gutter. directly, affecting plant and animal life. Potato paddock Ploughing across contours Loss of topsoil into watercourses reaching Swan Bay Swan Bay today Part of our heritage... Whilst Swan Bay is important to many people who live in and around the catchment, its importance has also been recognised at wider levels within the Australian and international community. Swan Bay, its mudflats, foreshore and islands, Edwards Point, Swan Island and Sand Island are listed on the Register of the National Estate for their heritage significance. The Register, maintained by the Australian Heritage Commission, highlights places of "aesthetic, historic, scientific, social or cultural significance which should be preserved for future generations as well as for the present community". This listing is a public recognition by the Australian community that Swan Bay is an area which is of national significance. Day-to-day protection Swan Bay forms an important part of the Port Phillip Heads Marine National Park which is managed by Parks Victoria on behalf of the people of Victoria. This is a highly protected area in which all marine life, both plants and animals, and cultural relics are protected. No activities that harm habitats or species are allowed within the Marine National Park. This includes collection of materials or extractive activities such as fishing (commercial and recreational) or mining. Port Phillip Heads Marine National Park is one of 24 highly protected areas along Victoria’s coast. More information about the Swan Bay and the Port Phillip Heads Marine National Park can be found on the Parks Victoria website at www.parkweb.vic.gov.au . Ramsar Convention on wetlands The Swan Bay section of the Port Phillip Heads Marine National Park is internationally recognised and is listed in the Ramsar Convention on Wetlands of International Significance. The Ramsar Convention was established in 1971 out of concern for the world's natural wetlands, which are disappearing at an alarming rate. The city of Ramsar, in Iran, hosted the important meeting at which Australia became a signatory to the Convention, agreeing to designate wetlands of international significance. Swan Bay was designated as a Wetland of International Significance in 1983. Swan Bay forms a part of the Port Phillip Bay (Western Shoreline) and Bellarine Peninsula Ramsar Site along with many other wetlands in the City of Great Geelong and other areas. Other parts o f the this Ramsar Site include: Mud Islands; Lake Connewarre and Reedy Lake; Point Wilson to Limeburners Bay; Avalon Airfield; The Spit; and Skeleton Creek to Point Cook. These areas are managed on a day to day basis by a range of organisations including the City of Greater Geelong, Parks Victoria, and the Department of Sustainability and Environment (DSE). Migratory birds agreements Migratory waders travel to Swan Bay from breeding and feeding grounds in Japan, China, Korea, Siberia and Alaska. Their habitats in Japan, China, Korea and Australia are protected by the Japan- Australia Migratory Birds Agreement (JAMBA), the China-Australia Migratory Birds Agreement (CAMBA), and the Korea-Australia Migratory Birds Agreement (KAMBA). These agreements recognise that certain species of birds migrate between these countries and that some are endangered in one or another country. Part of the agreement is that each of these countries will conserve the necessary habitats of these well-travelled birds. The Swan Bay / Fujimae-Higata Web Cam project is based on these agreements and provides a way for the City of Greater Geelong and the City of Nagoya to demonstrate working together with their partners in protecting migratory bird species and the habitats that support them Making the links As we have seen, Swan Bay does not exist as an isolated community of plants and animals. Most communities are locally interconnected, many are regionally interconnected - and some are internationally interconnected! Local connections can be illustrated by the Swan Bay catchment. Swan Bay could be thought of as the big puddle at the bottom of the hill. Whenever it rains on the surrounding land, water will eventually makes its way down into Swan Bay carrying with it various materials from soils to dissolved substances. The animals and plants that live in Swan Bay are therefore affected by what happens on the surrounding land. Regional connections are reflected in the shared ecologies of Swan Bay, Port Phillip Bay and Bass Strait. Swan Bay forms a part of the ecosystem that makes up the rest of Port Phillip Bay and Bass Strait. Every time the tide goes in or out water and the various living things that are found within it are transported into or out of the Bay. For some animals like King George Whiting the importance of Swan Bay as a nursery habitat (the place where baby fish can grow up safely) extends right along the Victorian coast and even into South Australia. Global connections are made by the visiting migratory birds which have made Swan Bay famous. As Swan Bay is a feeding area for birds that migrate from as far away as China, Japan, Korea, and Siberia, there are important connections between our own shores and those in these very distant parts of the world. When considering threatening processes and impacts which have the potential to cause changes within Swan Bay, an understanding of these types of connections will highlight the importance of protection of habitats and essential processes within the Swan Bay and catchment ecosystem. Threats to the Health of Swan Bay A number of activities have the potential to threaten the future health of Swan Bay. Some of these have been occurring for many years; others may be quite recent. The resulting impacts are often gradual and cumulative, rather than direct. Some of the most common activities and threats to the Bay are described briefly in this section. 1. Sedimentation Sedimentation is the process whereby small particles settle onto the bottom of the Bay. Over very long periods of time the build up of sediments has brought Swan Bay into existence, so sediments are not intrinsically "bad" for the Bay. Sediments have also affected the shape and depth of the Bay. Sediments can be divided into groups based on their origins: Group 1: Terrigenous Sediments These are sediments that result from non-living materials (such as rocks and soils), washed or blown down from the surrounding hills and towns, that accumulate on the bottom of the Bay. In Swan Bay, much of this material is soil washed from farmland and urban areas. Where there is little protective vegetation, the soil is easily shifted by the action of water running over the surface. The removal of plants from streamsides and catchment drainage lines was one of the first steps which led to the recent sedimentation of the Bay. Where streamside vegetation has been removed the rate of soil loss increased markedly. Large amounts of soil were washed downstream towards Swan Bay. This phenomenon continues today and is particularly noticeable after heavy rain when the whole of the Bay becomes highly turbid from soil carried down Yarram Creek. As materials wash into the Bay, heavy sand grains settle out first. Finer materials such as clays may take several days and many tide cycles before they accumulate on the bottom of the Bay or travel out into Port Phillip. The southern end of the Bay has become noticeably shallower since early Europeans used to fish at the entrance to Yarram Creek which ". . . abounds with bream . . ." This quote is taken from a book published in 1876 called `Queenscliff! How to See It'. Today it is difficult to imagine any fish managing to survive in the shallow mouth of Yarram Creek. A second source of terrigenous sediments is the movement of materials into Swan Bay with the tide. Suspended sand and other material in Port Phillip may have been washed into Port Phillip Bay from its own catchment or may have been washed down the Barwon River and then carried into Port Phillip. The build up of sand near the opening of the creek in Queenscliff is a good example of how much of this type of sediment is available in Port Phillip. The impact of increased sediments on the plant and animal communities in Swan Bay have not been extensively studied. In other parts of Australia however, increased sediments have been blamed for the loss of large areas of seagrasses, algal communities, and coral reefs. These losses occur when sediments cover the photosynthetic parts of producers (plants and some bacteria) allowing less light to reach them. Light is also blocked by turbid (cloudy) water. On the other side of the world, another bay is also seriously threatened by sediments from its catchment. Author Tom Horton has written of the Chesapeake Bay on the eastern seaboard of the United States, "Sediment (in streams) pollutes by smothering fish eggs, by tearing at the fragile gills of just born fish, and by covering the gravel bottoms that are prime habitats for fish spawning and for aquatic insects. Further downriver it may cover oyster beds. Sediment also clouds the water cutting off sunlight needed to grow the submerged grass that is critical habitat in streams and the bay." (Turning the Tide, 1990). While the location is different, the effects of increasing sediment in Swan Bay's water are likely to be much the same. Recently observed changes in Swan Bay indicate that seagrasses are in decline and it has been suggested that increased sedimentation may be one factor that is causing this decline. Group 2: Biogenous sediments The shallow waters of Swan Bay provide ideal habitat for a wide range of living things that build hard shells as a part of their bodies. These include many types of snails, bivalves (such as mussels), and crustaceans such as crabs and shrimps. When these animals die their shells slowly break down and add to the materials accumulated on the bottom of the Bay. In the past, enormous numbers of these animals (bivalves in particular) slowly created the extensive shell deposits which are now extracted commercially in the lower areas of Point Lonsdale. The continued natural production of shells is also gradually filling the Bay with new materials, this being most observable in the less tide and wave affected southern and northern ends of the Bay, where many types of bivalves grow in soft sediments. 2. Seagrass Dieback The community of plants and animals living in Swan Bay is dependant on seagrass both as a source of food and as habitat. Seagrass leaves are an ideal place for many simple plants - like algae - to settle and grow. Algae that are growing on the surface of the seagrass leaves are called epiphytic algae. In the Bay, small herbivorous snails feed directly on these epiphytic algae and in turn keep the leaves of the seagrass from being completely smothered by the algae. This allows the seagrass to keep using sunlight to make its own food and thus stay alive. Too much epiphytic algae would block the leaves from the sunlight and cause the seagrasses to die. Too little would leave many animals without food. Over the past few years there has been an increase in epiphytic algae in some parts of Swan Bay. This has caused the seagrasses to die off. More recently many areas of Swan Bay have been covered by a floating mass of larger, reddish-brown algae. This has had more widespread effects, and some types of seagrass which were previously common have now been completely smothered and are rare in Swan Bay. Generally, algal growth is encouraged where there are high levels of nutrients like phosphorus and nitrogen in the water. 3. Loss of Useable Farmland Farmland is only as good as its topsoil, but one of the consequences of the removal of much of the native vegetation within the Swan Bay catchment has been the increase in the rate at which soil is lost from the catchment. Well developed vegetation and a well-developed "litter layer" of leaves and twigs slows down the movement of water across the ground surface, allows water to re-enter the ground, reduces runoff, and protects soils from winds. Soil which is left open to the effects of rain and wind through vegetation clearing, cultivation, .or over grazing has the potential to be carried away and end up in Swan Bay or beyond. Water flowing down the catchment picks up speed on bare soils, resulting in increased risk of water erosion on open soils. Today, very little remains of streamside vegetation in the catchment. Creek banks are mostly bare or are sown with shallow-rooted pasture. Many creek banks are grazed by sheep and cattle -animals which contribute to erosion by the action of their hard hooves. Heavy rainfall can then dislodge and carry away unprotected soil from creek banks. Soil loss from creek banks has in some locations led to the formation of large erosion gullies. Such gullies, in addition to being evidence of the amount of soil which has been lost to Swan Bay, are also graphic reminders of the amount of soil which is now no longer available for farming throughout the catchment. In some cases these gullies are so deep that they represent a real management problem to farmers in getting themselves, machinery, and stock from one side of the gully to the other. Loss of topsoil within the catchment through wind erosion is also significant. Where soils are exposed, strong winds can and do remove tonnes of soils which eventually make their way to the Bay. This impacts on the economic viability of farming in the Swan Bay catchment through degradation of farmland and loss of productivity. As topsoils also contain most of the nutrients available for plant growth, the loss of topsoil means that additional fertilisers may then be needed provide for the needs of growing crops. Additional nutrients, if not applied carefully and in appropriate locations, can result in increased nutrient runoff which can also affect the Bay. An additional problem which is evident in some parts of the catchment is soil salinity. Salt affected soils are reducing the ability of farmers to use the land for grazing or cropping. This increase in soil salinity is almost certainly linked to the removal of trees from the hillsides. Old trees have well developed root systems, which penetrate deep into the soil. Much of the water taken up by trees comes from such depths. With trees mostly gone from the catchment, the underground water table has risen, bringing dissolved salts with it. Salt affected soils do not support most plants, so there is a danger that these areas will become bare and erode, leaving even more unusable farmland in the catchment. 4. Stormwater, Litter, and Nutrients Every stormwater drain in the catchment is linked, either directly or indirectly, to Swan Bay. What happens to rain after it rains? Have you ever thought about the journey of a raindrop after it hits the ground or the roof of a house? The rain that hits the land around Swan Bay eventually makes its way down through the catchment to the big puddle at the bottom of the hill - Swan Bay. After leaving your roof, or the road, water flows into large drains that run below the roads. These drains are called stormwater drains. These carry the water down the catchment and into the Bay. Along the way to the Bay the rain drop joins with others. They collect a variety of materials including soils, oil, grease and litter. The rainwater also collects many dissolved materials that we cannot see - nutrients (plant foods), dissolved metals, bacteria, and pesticides. What was once clean water is now a cocktail which will eventually flow into Swan Bay. In towns the runoff from the land is usually much greater than the runoff from bushland or farms. This is because hard surfaces like roofs, bitumen streets, and concrete pathways do not absorb any water. When it rains, virtually all of the water that hits these surfaces is carried down into the stormwater drains, usually at a fast rate. When water moves quickly it can pick up large quantities of bigger materials such as litter and soil. These are then carried through the stormwater system into the Bay. Plastics and other items of litter may take a long time to breakdown in the Bay. They also have the potential to trap animals or be eaten by them. Soil which is washed down stormwater drains covers seagrass just as effectively as soil which washes down creeks. Apart from the solid materials carried to the Bay by water, many of the dissolved materials have the potential to affect Swan Bay. Some of the materials that can come from urban areas include: ammonia based cleaners and car waxes paints and thinners detergents with phosphates insecticides and herbicides oil, petrol, and brake fluid bleaches and drain cleaners lawn fertilisers and chemicals toilet cleaners and septic tank overflows dog and other animal wastes. Some of these materials are significant sources of nutrients entering the Bay. Nutrients are simple materials that are important for the growth of plants (including marine plants). They dissolve in water. Typical nutrients include nitrates and phosphates, substances which are found in lawn, vegetable and paddock fertilisers, in some detergents, and in animal wastes, including human sewage. Other chemicals entering the Bay from the catchment may become bound up in the sediments on the bottom of the Bay and eventually make their way into food chains. Oils and grease can coat living things making it difficult for them to get oxygen. Unfortunately, little is known about the effects of these materials on seagrasses or the animals and plants that live in seagrass communities. Whilst nutrients in water are natural - indeed, they are essential for living things - large amounts of nutrients entering the Bay have the potential to stimulate the rapid growth of the Bay's naturally occurring algae. Because the algae can grow more rapidly than seagrasses, they can smother the seagrasses and, in a similar manner to sediments, block sunlight from reaching the leaves of the seagrasses. If the levels of nutrients entering the Bay are very high, the level of algal growth can also be significant. The sheer amount of algae, now growing, spreading and dying as part of its normal life cycle, uses up much of the dissolved oxygen in the water when it decomposes. For most animals in the water, this is the oxygen which they previously used to breathe! Crabs, worms, molluscs, fish and other animals can then die from a lack of oxygen. This process of oxygen removal by decomposing plants and animals is called eutrophication. Eutrophication is a major problem in many bays around the world. Fortunately so far this has not occurred on a large scale in Swan Bay, although localised examples are common. 5. Farming Nutrients In order to promote the growth of healthy crops and pastures it is common practice in Australian agriculture to apply artificial, soluble fertilisers to soils. Most Australian soils are low in minerals like phosphorus and nitrogen and, through adding them as fertilisers, the growing crop and pasture plants are able to absorb what they need from the dissolved materials in the soil. The plants grown on most farms did not evolve in Australia and need high levels of certain nutrients in order to grow well. Most native plants are well adapted to low nutrient levels and do not require much in the way of nutrients for good growth. One of the ecological drawbacks of using most artificial fertilisers is that they are highly soluble in water. While this might be useful initially in getting the nutrients to the plants roots, it also results in much of the applied fertiliser being washed away from the crop and pasture plants, and into creeks, streams, and eventually into the Bay. Because of the slow tidal exchange within the Bay these nutrient levels may increase over time. Where excessive amounts of nutrients get into water they encourage the growth of algae. These grow rapidly and can soon cover all other plants that might be growing in the water, including seagrasses, preventing them from being able to get sufficient amounts of sunlight. This may kill the seagrass. In large quantities excess nutrients can cause eutrophication. Through the use of more efficient methods of applying fertilisers, the use of less soluble forms of fertilisers and more organic materials, improved streamside management and drainage line revegetation, we may see a time when most of the applied nutrients would remain on the farm where they do the most good, not in the water where they can do the most harm. Agricultural nutrients are not just a problem in Swan Bay. The State of the Marine Environment Report (1995) indicates that right along the entire eastern coast of Australia excessive amounts of nutrients are entering coastal ecosystems. From the tropical reefs to our temperate mudflats, nutrient pollution is our biggest coastal pollution problem. 6. Saltmarsh dieback Saltmarshes extend over much of the shoreline of Swan Bay. In many areas these saltmarshes remain in good condition although there are also many areas where they have been cleared for mining of shellgrit, agriculture, housing and urban development, or harbour developments. The importance of the remaining saltmarshes in Swan Bay are heightened by the loss of similar areas around most of the remainder of Port Phillip Bay's shoreline. Between Point Lonsdale and Melbourne there has been a 75 - 80% reduction in saltmarsh area since Europeans arrived in Victoria. These areas contain a diversity of plants and animals not found in other habitats. Saltmarshes are also significant because they are amongst the few areas able to provide food for the highly endangered Orange-bellied Parrot. These birds feed on the Beaded and Shrubby Glassworts that grow in the saltmarshes around Swan Bay during their annual winter migration from Tasmania. Some of the threats to remaining saltmarshes include: Grazing: some of the areas on the southern and western side of the Bay have fence lines that extend into the saltmarshes. In the past, grazing of the saltmarshes was common practice, particularly during summer when less food was available on pastures. The impact of this has been the loss of some native species and the establishment and spread of exotic (non-native) species -including a number of environmental weeds. Trampling: saltmarsh habitats are very sensitive to trampling and in areas where people and their pets walk there can be significant losses. Environmental weeds: Numbers of exotic plants have become well established in some of the Swan Bay's fringing saltmarshes. Coast Barb-grass is widespread in areas that have been affected by grazing; it has the potential to dominate large areas of saltmarsh. Pampas Grass has become established in saltmarsh near Edwards Point and in the grassland at Swan Bay's southwestern shore. Of even greater potential to change the saltmarsh habitat is the exotic Marsh Grass, also know as "Spartina". Whilst this grass has not yet been found in the catchment, it has been found in nearby Lake Connewarre and the Barwon River estuary, as well as a number of other places in Victoria where it was originally introduced to plant in mudflats. This aggressive plant completely replaces all other saltmarsh plant species and would invade many of the mudflats within the Bay itself if it arrived here. Urban development: Some areas of saltmarsh have been drained and subdivided for housing, particularly on the southern edge of Swan Bay. This, combined with mining of shell grit in this area, has significantly reduced the area of saltmarsh remaining. The impact of increased stormwater and nutrient flow through this area is not yet known. On the edge of Sand Island there has actually been a slight increase in the area covered by saltmarsh. Sediments have been dredged from the Cut in Queenscliff (to keep the entrance clear for boats) and disposed of onto Sand Island. Where these dredge "spoils" have settled, a lagoon fringed with saltmarsh has developed. This area has become a significant feeding area for many birds. Swan Bay and the wider picture So far in this kit we have looked at Swan Bay and its catchment as a series of linked habitats. We understand a little about each habitat, less about the way each one works, and even less about the impact that a change in one habitat has on the other habitats within the catchment. Unfortunately, most of our understanding has come from observing the direct effects of environmental degradation, instead of observing the natural function of the catchment. Strangely enough, we may know more about the links between Swan Bay and other natural systems than we know about the links within the catchment. Two examples - migratory birds and edible fish - highlight these links and show just how important Swan Bay and its catchment are on a global scale. If your brain is really tuned in, you will also be able to appreciate the links between these two examples! Many of the birds which reside in Swan Bay do so only for a certain period each year. Black Swans seem to spend the summer and autumn months here, after which most of them return to inland waters. Immediately we can see that there is a link, made by the swans, between Swan Bay and our inland freshwater lakes. Other birds come from further away. Many of the wader birds fly in each year from Japan, China, Siberia, Korea or, in the case of the migratory shearwaters, from northern Alaska. The Double-banded Plover flies between Swan Bay and New Zealand. All these birds are the links between Swan Bay and the beaches, lakes and forests on the other side of the world! Birds are not the only animals to make a long journey to Swan Bay. The highly prized King George Whiting takes up to four months to travel hundreds of kilometres through southern seas before reaching Swan Bay. Perhaps the most remarkable aspect of its travels is that it does all this when it is so small it can hardly be seen! Once the tiny fish reaches Swan Bay's seagrass, it settles down to the business of eating, growing and surviving. Those whiting that do survive may then move out of Swan Bay into Port Phillip when they are older -and it is these fish which end up on the dinner plates of so many people in Victoria. From these two examples alone, it is easy to see why Swan Bay is considered to be a kind of natural "meeting place". Where else would a Korean bird and a South Australian fish get together? Of course, the meeting may involve the bird eating the fish, but this shows us why such a natural meeting place is vitally important to ecosystems the whole world over. Working backwards (ie. up into the catchment), we can see how an everyday activity like ploughing a paddock, washing a car, or fertilising a rose bush has the potential to affect animals on the other side of the world. If soil is lost from the paddock into a creek (which drains into the Bay) and this kills seagrass, where is the habitat for the whiting? When the excess nutrients from garden fertilisers and washing detergents stimulate algal growth, in turn killing seagrass, where is the habitat for the whiting? What happens to the whiting when it reaches Swan Bay? If there are less whiting, how much food is there for the migratory birds? This is not to say that ploughing a paddock or washing a car is an irresponsible act, but there are certainly some methods which are better than others. And there are many other everyday activities going on in the catchment's towns that have equal potential to affect global systems. Whiting are not the only fish needing healthy seagrass for survival. Many other fish, sharks, snails, shrimps and crabs all rely on Swan Bay's seagrass meadows. In fact, Swan Bay's seagrass meadows are Port Phillip's largest fish nursery. Swan Bay and its catchment are important closer to home, as well as internationally. As more land in Australia is cleared for roads, farms, and housing, the value and importance of the remaining vegetation increases. Although it has one of the lowest retention rates of indigenous vegetation in Australia, the Swan Bay catchment does contain many plants which are also rare in other parts of south-eastern Australia. The catchment is therefore an important link in the overall conservation of many types of plants and the animals which depend on them. The precautionary principle warns us that changing something which we do not understand is not a very wise thing to do. An analogy often used to explain the precautionary principle is that of a clock. All the parts work well together, but if we want to change the way the clock works (maybe to make it tick faster!), we should first have an understanding of exactly how it works! If we start fiddling with the workings of the clock, but don't know what we are fiddling with, the chances are that the clock will never work again. Fortunately for us, so far the Swan Bay catchment is working like a clock that can cope with a fair amount of fiddling. It has certainly had a few parts removed; others have been re-designed and bent out of their original shape, and new parts that don't belong have been added - but, remarkably, it still ticks. The question is "for how long?" Nothing is more uncertain.