Marine biogeography

							UKZN School of Environmental sciences, ENVS120 - Biospheric processes



L7: Marine
biogeography




Marine species have
fewer barriers to moving
around than terrestrial
species do.
                                “Dispersal unlimited” (almost!)
         Marine distributions
• According to ecosystem type
• Predominantly tropical systems: mangroves,
  coral reefs, sandy beaches
• Predominantly temperate/cold systems: salt
  marshes, rocky shores
• Deep water and open water systems: across
  climates
• Within ecosystems, varying with things such as:
  temperature, depth, salinity, productivity
              Major ecosystems

Coastal systems: rocky shores, sandy beaches,
coral reefs, mangroves, salt marshes

                                       Open water systems,
                                       such as floating
                                       communities (“blue
                                       community”),
                                       sargassum etc.




                                  Bottom systems, such as
                                  hydrothermal vents (black
                                  smokers), cold seeps
The open sea: relatively few species
Often blue in colour
Most primary producers microscopic
But also sargassum seaweed
                                                                  Hydrothermal vent
                                                                  (“black smoker”)

Sea bottom
with no
special
geological
features




                                                             Cold
                                                             seep


The mid-ocean ridge system with well known deep-water hydrothermal vent (ellipses) and cold seep
(oblongs) regions. Vents: 1, Mid-Atlantic Ridge; 2, East Pacific Rise; 3, Galapagos Rift; 4, NE Pacific; 5 and
6, W Pacific back-arc spreading centres; 7, Central Indian Ridge. Cold seeps: 1, Gulf of Mexico; 2, NW
Africa; 3, Laurentian Fan; 4, Barbados accretionary prism; 5, Monterey Bay; 6, Oregon subduction zone; 7,
Sagami bay
                            Coral reefs




Extremely species-diverse (most species crustaceans,
corals, molluscs, fish)
Reef-forming organisms: corals, sponges etc
Main primary producers: algae living inside corals‟
bodies
                                        Coral reefs

Distributed along tropical coasts with limited sedimentation
Sensitive when sedimentation increases (e.g. erosion in river
flowing into the sea nearby)
               kelp




                                              barnacles




Life on ROCKY SHORES strongly affected by
tides                                         limpets
Species-rich, most species molluscs (many
snails, few bivalves), crustaceans
On west coasts associated kelp forests (SA,
Chile, California)
                            Sandy beaches


                            Species-poor
                bivalves
                            Many species small, inside the sand
                            Molluscs (many bivalves, few snails)




                           Sand crabs               Ghost crabs
Bullia snails
Salt marshes
Dominated by salt-resistant
herbs
Mostly in estuaries, lagoons
  Mangroves




                                             Fiddler crabs




mudskippers
              The most thorough combination of
              marine and terrestrial
              Mangrove trees have special
              breathing roots („pneumatophores‟)
              and are tolerant to both daily
              flooding and salinity.
Productivity in the sea                         (illustrated as chlorophyll)




High in cold regions (in the Arctic, Antarctic, on west
coasts), low in some warm regions, mostly where
there are coral reefs.
          Sea surface temperature
The main factor determining distributions inn marine species; two clear
cold bands, two temperate, one tropical. But the tropical one is
separated into Atlantic and Indo-Pacific. This barrier was cut with the
Panama Canal
Marine distributions
Temperate: generally disjunct –
northern and southern
                           Tropical distributions: more likely disjunct between
                           Atlantic and Indo-Pacific




Indo-Pacific: butterfly fish                              Atlantic: the eel (A. anguilla)
Cosmopolitan: most often in large animals,
             in the open water




                      Killer whale
 Marine regions: in five to eight latitudinal bands
(tropical, temperate, cold; sometimes also subtropical, subpolar; for
                         both hemispeheres)
    “Large marine ecosystems”




Useful for conservation, for assessing regional biodiversity, human impact