DEGRAD - PDF by adelaide17madette

VIEWS: 6 PAGES: 3

									SCIENTIFIC CORRESPONDENCE

Evidence of biological degradation in sediments of Deepor Beel
Ramsar Site, Assam as inferred by degraded palynomorphs and
fungal remains
Any depositional environment like lakes,         genera of 103 families, whereas the pter-     the wetland ecosystem, where data on
wetlands, estuaries, etc. where water per-       idophytes belong to 13 species from 12        degradation of organic material by bacte-
mits accumulation of sediments derived           genera of 11 families1. The unique aquatic/   ria and fungi documented in the sedi-
from bedrock, soil and organic remains           marshy macrophytes can be distinctly          ments in other areas by earlier workers2–7,
within the drainage basin, can provide a         categorized, viz. free-floating: Salvinia     have inspired us to initiate the present
finely resolvable record of past or ongo-        oblongifolia, Eichhornia crassipes, Trapa     work.
ing environmental processes and compo-           bispinosa, Lemna minor, Ceratopsis thal-         Among various biological proxies,
nents, both natural and human-induced,           lictroides; free and submerged: Potamoge-     pollen-spores, diatoms, etc. procured from
including soil erosion, air-transported          ton pectinatus, Ceratophyllum demersum,       sediment deposits can provide an indica-
particles, solute transport and land-sliding.    Limnophila heterophylla; anchored sub-        tion of the degree and nature of impact of
In recent times there has been increasing        merged: Hydrilla verticilata, Vallisnaria     past and current events on the system.
concern over the continuing degradation          spirales; anchored and floating: Marsilea     Sediments from the study area have been
of wetlands, especially in Northeast             minuta, Nymphaea nouchali, Nelumbo            procured in a transect (N–S to E–W). Pa-
India. Considering the importance of the         nucifera, Myriophyllum indicum; emer-         lynological preparation of ten sediments
floral and faunal value of Deepor Beel           gent amphibious: Rumex nepalensis,            (silty clay to organic mud, pH alkaline)
having Ramsar site status, we made an            Polygonum orientale, Alternanthera ses-       was made using the standard procedure
attempt to generate biological baseline          siles, Hypericum japonicum, Juncus ef-        of acetolysis8. Out of ten samples, sam-
data to save the most coveted wetland            fusus, Ranunculus reptans, Hydrocotyle        ple nos 1 and 2 were procured from sub-
from havoc destruction and degradation.          javanica, Cyperus platystylis, Scirpus ar-    merged area and sample nos 3–7 from
Deepor Beel (lat. 26°03′26″–26°09′26″N           ticulatus,      Fimbristylis    scirpoides,   degraded grassland areas of the northern
and long. 90°36′39″–90°41′25″E) is situ-         Eleusine indica, Sagittaria segitifolia;      and eastern flank respectively. Sample
ated 10 km southwest of Guwahati town,           marshy and amphibious: Ammania bac-           nos 8 and 9 were procured from the vici-
Kamrup District, Assam (Figures 1 and            cifera, Commelina benghalensis, Ipo-          nity of the green belt catchment area in
2). It is the lone Ramsar Site in the state      moea aquatica, Jussiaea repens, etc.          the southern flank and sample no. 10 from
and the second of its kind in Northeast          Economically important medicinal plants       the western flank of the upland area.
India, after Loktak in Manipur. The Beel         include Rauvolfia serpentina, Vitex ne-       Minimum 250 palynomorphs per sample
has a perennial water-holding area of about      gundo, Dioscorea pentaphylla, Costus          were counted for reconstruction of pollen
10.1 km2, which extends up to 40.1 km2           sp., Holarrhena antidysenterica, Dryop-       spectra. In the pollen spectra, the assem-
during floods.                                   teris sylvestris and Datura metel. The        blage has been segregated into local ar-
   This large water body is a great food         area has not received much attention          boreal, open-land taxa, aquatic/marshy,
source and breeding ground for a variety         especially from the biological point of       highland exotics, degraded pollen-spores
of migratory birds, amphibians, reptiles,        view. The present correspondence is an        and other organic matter, whereas micro-
insects, micro and macrophytes, terres-          attempt regarding conservation and pre-       phytes such as diatoms other algae have
trial weeds, lianas and arborescent taxa         servation of the unique ecosystem             not been included in the pollen sum.
of ecological and economic importance.           through palynological interpretation, es-        The pollen spectra depict a mixed pollen
A variety of angiosperms have been               pecially in order to understand the inter-    assemblage which does not fully match
documented under 435 species from 305            play of microbiota and sedimentation in       the present vegetation around the Deepor
                                                                                               Beel (Figure 3). The relative frequency
                                                                                               of the assemblage included local arboreals
                                                                                               (9–15%) consisting of Terminalia, Meli-
                                                                                               aceae, Lagerstroemia, Salmalia and




                         Figure 1.   Location map of sampling site.                                 Figure 2.   A view of Deepor Beel.

178                                                                                    CURRENT SCIENCE, VOL. 95, NO. 2, 25 JULY 2008
                                                                                         SCIENTIFIC CORRESPONDENCE
Syzygium; open-land taxa (8–14%),             original entity almost lost, whereas in case       perforations (Figure 4 (35)). However, in
mainly comprising Eupatorium, Xanthium,       of pollen of Malvaceae (Figure 4 (31)),            the case of pollen from Salmalia and
Caryophyllaceae, Acanthaceae, Cheno-          the appendages were loosened leaving               Caryophyllaceae (Figure 4 (33 and 34)),
podiaceae and Poaceae; aquatic/marshy         circular bases only. The pollen of Meli-           thinning of both surface ornamentation
taxa (10–16%) comprising Trapa, Nym-          aceae (Figure 4 (32)) was also under bio-          and apertures occurred. Rosette form of
phoides, Polygonaceae, Jussiaea and           logical attack as evidenced by                     degradation has been found in the
Cyperus; highland exotics (16–28%)            ramification of hyphae. The Betula pol-            smooth-walled monolete fern spore (Fig-
consisting of Pinus, Betula, Alnus, Jug-      len was affected in the form of circular           ure 4 (36)), whereas disintegration of spore
lan and Quercus. Ferns were dominated
by only few species under the genera,
Davallia, Polypodium, Gleichenia, Cyat-
hea, Lycopodium and Dryopteris.
   The low profile of phytoplankton in
sediments consisting of Nostoc, Oscilla-
toria, Navicula, Nitzchia, Fragillaria and
Synedra indicates both poor water condi-
tion and preservation status of the Beel.
The present study indicated the domi-
nance of members of Deuteromycetes
and Ascomycetes in the sediments. Dip-
lodia, Nigrospora, Curvularia, Tetraploa
and Helminthosporium, the common
pathogens of grasses and cereals were
more frequent in the assemblage. De-
graded pollen-spores were encountered
in good numbers (9–16%) in the sedi-
ments. Among the degraded forms, pollen
of Malvaceae, Meliaceae, Caryophylla-
ceae, Salmalia and Betula were less en-
countered compared to ferns. The most
frequent degradational pattern found in
pollen-spores recovered from sediments
consisted of circular, rosette to branching
perforations     (wedge-shaped).       Both
smooth-walled (fern monolete and
trilete) as well as ornamented pollen
(Malvaceae, Meliaceae and Betula) are
affected by microorganisms. It is evident
that multiple degradation pattern of
penetration through the spore walls may
lead the palynomorphs to be reduced to
small remnants leaving only the pollen
shape. In extreme cases, the pollen-
spores get reduced to fragments without
any original entity, in which case the
identification of palynomorphs could be
either difficult or impossible. In our
study, the Cyathea spore (Figure 4 (38–
40)) was under massive attack, with the       Figure 4. Palynomorphs recovered from Deepor Beel sediments (all figures ×1200). 1, Fruiting
                                              body resembling Trichothyrites sp.; 2, Sporangia resembling Entophlyctis sp.; 3, Ascospores of
                                              Cookeina sp.; 4, Nigrospora sp.; 5, Unknown; 6, Helminthosporium sp.; 7 and 8, Circinoconis
                                              sp.; 9 and 10, Unknown; 11, Coniothecium glumarum type; 12 and 13, Alternaria sp.; 14 and 15,
                                              Tetraploa spp.; 16, Curvularia sp.; 17, Unknown; 18, Germinating sporangium; 19, Xylaria sp.;
                                              20, Group of conidia; 21, Meliola sp.; 22, Unknown conidiophore; 23, Unknown; 24, Macrodip-
                                              lodia sp.; 25 and 26, Stem peeling with pits; 27, Circular pits over surface of biota; 28, Piece of
                                              charcoal; 29, Sclerenchymatous tissue; 30, Epidermal peeling with stomata; 31, Pollen of Malva-
                                              ceae with loosened appendages; 32, Pollen of Meliaceae having initial wedge-shaped perfora-
                                              tions; 33, Partly degraded pollen of Salmalia sp.; 34, Partly degraded pollen of Caryophyllaceae,
                                              pore with annulus missing at places; 35, Degraded pollen of Betula with circular perforations
                                              near the aperture; 36, Monolete fern spore with rosette form of perforations on spore wall; 37,
                                              Degraded monolete fern spore having deterioration at edges; 38, Wedge-shaped perforations and
                                              thinning of aperture in Cyathea sp.; 39, Branching arrangements of wedge-shape perforations
Figure 3. Recent pollen spectra from Dee-     around the lete in Cyathea sp. and 40, Spore of Cyathea almost deteriorated with massive fungal
por Beel sediments.                           attack.

CURRENT SCIENCE, VOL. 95, NO. 2, 25 JULY 2008                                                                                                179
SCIENTIFIC CORRESPONDENCE
wall at both ends occurred in another         appearance of palynomorphs in the assem-      the Ramsar Site list, more multidiscipli-
monolete form (Figure 4 (37)). It is in-      blage. It is also interesting to note that    nary scientific approaches and proper
teresting to note that there was no sign of   many important economically useful            wetland management by the concerned
any degradation on vegetal parts like epi-    plant taxa, namely R. serpentina, Costus      authorities are required urgently. If not,
dermal peeling with stomata and pits,         sp., Terminalia arjuna, V. negundo, D.        the plant wealth will soon vanish from
sclerenchymatous tissue and charcoal,         pentaphylla, H. antidysenterica, D. syl-      the region.
indicating high resistance to biological      vestris and D. metel have not been en-
decay (Figure 4 (25–30)). The availability    countered in the pollen assemblage in
of decaying hyacinth, Salvinia, Ipomoea       spite of their presence in the existing       1. Gogoi, R., Ph D thesis, Gauhati University,
                                                                                               Guwahati, 2006.
and Pistia near the degraded grasslands       vegetation. However, the influence of
                                                                                            2. Rege, R. D., Ann. Appl. Biol., 1927, 14, 1–
at the edge of the Beel provides a conge-     seasonal factors for the emergence and
                                                                                               44.
nial condition for the growth of sapro-       disappearance of the aquatic and terres-      3. Barghoorn, E. S., Science, 1942, 96, 358–
phytic fungi such as Alternaria, Xylaria,     trial herbs and appearance of reproduc-          359.
etc. which supports the study. Therefore,     tive phases of tree species, and sustained    4. Sparrow, F. K., Biol. Bull., 1937, 73, 242–
the occurrence of degraded palynomorphs       monitoring of endangered wetland sites           248.
festooned with abundant fungal remains        should be studied as the flood situation is   5. Goldstein, S., Ecology, 1960, 41, 543–545.
in the sediments could be one of the vital    different each year. Despite this Ramsar      6. Graham, A., J. Paleontol., 1962, 36, 60–
reasons for degradation of certain pollen     Site, the vast northeastern alluvial plain       68.
taxa; this needs further investigation. It    with a large number of other potential        7. Elsik, C. W., Micropaleontology, 1966, 12,
                                                                                               515–518.
has also been observed that the frequency     wetlands has ample scope to execute the
                                                                                            8. Erdtman, G., An Introduction to Pollen
of degraded palynomorphs was relatively       palaeoclimatic studies in order to recon-
                                                                                               Analysis, Waltham, Mass., USA, 1943.
more in sediments of high pH (Figure 5).      struct the changing vegetation scenarios
   Thus a systematic study involving the      and contemporary climatic oscillations in
development and origin of fungal ele-         a chronological order during the past.        ACKNOWLEDGEMENTS. We thank the
ments which are the causal agent in de-       Hence, a comprehensive pollen analysis        Director, Birbal Sahni Institute of Palaeo-
structing certain pollen and spores should    of a series of sedimentary profiles from      botany, Lucknow for providing the necessary
be made, that would in turn help in ex-       the various wetland sectors could be im-      facilities and permission to publish the paper.
plaining the cause of destruction and dis-    perative to depict vegetation succession      We also thank the forest officials for help dur-
                                              with climatic variability at broader and      ing the field work.
                                              shorter intervals. These attempts can also
                                                                                            Received 24 January 2008; accepted 13 May
                                              help in the simulation of models for un-
                                                                                            2008
                                              derstanding the future course of climate
                                              in a definite time-frame. The approach is
                                              also expected to bring out the anthropo-                                     S. K. BERA1,*
                                              genic impact on natural vegetation as                                        SWATI DIXIT1
                                              well as migration and extinction of many                              S. K. BASUMATARY1
                                              important plant elements as a consequence                                    RAJIB GOGOI2
                                              of increasing over-exploitation, climatic
                                                                                            1
                                              shifts and natural catastrophe. In turn,        Birbal Sahni Institute of Palaeobotany,
                                              this information will enable us to suggest    53, University Road,
                                              appropriate measures for the conserva-        Lucknow 226 007, India
                                                                                            2
                                              tion of natural resources in wetlands.          Botanical Survey of India,
                                                 Therefore, to save the diversified life-   Shillong 793 003, India
Figure 5. Relationship between pH, fungal     forms in this fragile ecosystem which has     *For correspondence.
remains and degraded palynomorphs.            been declared as a Wildlife Sanctuary in      e-mail: Skbera_2000@yahoo.com




180                                                                                 CURRENT SCIENCE, VOL. 95, NO. 2, 25 JULY 2008

								
To top