Role of Clams in Regulating Biogeochemical Processes of Ashtamudi Lak

Abhilash, K S

Alloycious, P S

Anilkumar, P S

Aswathy, K S

Jenni, B

Kripa, V

Mohamed, K S

Prema, D

Saji Kumar, K K

Sajikumar, K K

CMFRI Digital Repository

ROLE OF CLAMS IN REGULATING BIOGEOCHEMICAL PROCESSES OF  ASHTAMUDI LAKE *Prema, D;  K. S. Mohamed; V. Kripa;  B. Jenni; P.S. Alloycious; K. K. Sajikumar; K. S.  Aswathi;  K. S. Abhilash and P.S. Anilkumar  Central Marine Fisheries Research Institute *premadicar@gmail.com             Need for the Study Methods Analysis Results Discussion Hand dredging for  clams in Ashtamudi Lake References COMPARING ECOLOGY OF CLAM AND NON CLAM ZONES OF ASHTAMUDI LAKE As part of eco-labelling the scientifically managed clam fisheries of Ashtamudi Lake, the Central Marine Fisheries Research Institute (CMFRI) in collaboration with, World Wide Fund for Nature (WWF), in 2014, probed into the ecosystem benefits coming out of the management initiatives. Accordingly, a rapid appraisal of selected biogeochemical processes was carried out analyzing two scenarios  viz.  a) Clam bed with fishery and b) Non clam zone in Ashtamudi Lake.  Among bivalve molluscs, clams form an important resource as meat for human consumption and for shells in the cement industry. The Ashtamudi Lake Ecosystem in Kerala (southwest coast of India) is well known for its clam resources. This estuarine system between latitude 8˚45’ ‐ 9˚28’ N and  76˚28’ ‐ 77˚17’ E contributes approximately 80% of the overall clam export trade in India, providing livelihoods for at least 3,000 local people. Sorting clams Map of Ashtamudi Lake showing  clam sampling zones  Samples of water, sediment, plankton and benthos were examined using standard methods. Water quality (in terms of nutrients, particulate organic matter, particulate inorganic matter, chlorophyll, TSS, BOD etc.) and sediment quality (in terms of               organic carbon, oxidation reduction potential, available nutrients, texture etc.) were assessed using standard procedures.  Water  sampling Sediment sampling   Table1.  Selected Biological Characteristics  Scenario  Clam with fishery  No Clam     Clam (numbers) 85 - Clam weight (g) 196 - Ratio of Clam Weight to Nos. 2.3 - Diatom count, millions ml-1 3.51 3.11 Benthos (Biomass),  g m-2 48.44 95.16 Table  3.  Selected Water Characteristics Scenario Clam with fishery No Clam Optimum range  Chlorophyll a, µg l-1 21.34 18.93 17-40 Temperature, ˚C 27.5 28.4 25-32 Salinity, PSU 30 28 2 - 48 DO, , mg l-1 4.44 4.44 5 -10 TSS, mg l-1 154.1 78.1 25-200 BOD, mg l-1 0.49 0.89 <15 COD, mg l-1 19 10 <70 P O M, mg l-1 23.59 16.17   P I M, mg l-1 130.5 61.92   pH 7.5 7.6 7.0-8.7 Total ammonia – N, mg l-1 0.094 0.03 0-0.1 Nitrite – N, mg l-1 0.003 0.003 0-0.5 Nitrate – N, mg l-1 0.051 0.05 0.1-3 PO4 –P, mg l-1 0.003 0.001 <0.01 Silicate, mg l-1 1.68 0.303 > 5 Table 2 . Sediment Quality Scenario Clam with fishery No Clam Optimum range Organic carbon, % 1.77 0.9 1.5 – 2.5 Eh, mV -44 -97 > -200 Salinity, PSU 11.49 7.15 > 2.2 Ammonia – N, ppm 3.23 1.85 Together as available N, 250-750ppm Nitrite- N, ppm 0.05 0.02 Nitrate-N, ppm 0.36 0.33 Available P, ppm 77.35 60.29 > 60 pH 7.22 7.65 6.5 – 7.5 Sand, % 68.6 82.1 40 Silt, % 17.0 10.9 30 Clay, % 14.1 6.8 30 TABLE OF DISCUSSION Scenario  Clam with fishery  No Clam Probable reason Diatoms  More    More nutrient release Chlorophyll ≈1.13 times     More nutrient release Water temp ≈Same     TSS ≈2 times     May be due to clam fishing Water salinity ≈Same     DO ≈Same     BOD   ≈2 times   Less bio-oxidation in non clam region COD ≈1.9 times   More oxidation due to clam bioturbation Water pH ≈Same     Ammonia-N (water) ≈3 times    From clam faeces Nitrite-N (water) ≈Same     Nitrate-N (water) ≈Same     PO4- P (water) ≈3 times     From  clam faeces Silicate in water ≈5.6 times     From clam faeces Particulate organic matter ≈1.5 times    From  clam faeces Particulate inorganic matter ≈2 times    From  clam faeces Sediment organic carbon ≈2 times      From  clam faeces Sediment salinity ≈1.6 times      More nutrient release Ammoniacal  N (sediment) ≈1.8 times   From  clam faeces Nitrite N in sediment ≈2.5 times     From  clam faeces Nitrate in sediment ≈1.09  times      More oxidation due to clam bioturbation Oxidation –Reduction Potential in sediment ≈2.2 times more oxidative   More oxidation due to clam bioturbation Available  P in sediment ≈1.3 times    More oxidation due to clam bioturbation Sediment pH ≈Same     Sand in sediment ≈1.2 times less     From  clam faeces Silt in sediment ≈2 times      From clam faeces Clay in sediment ≈1.6 times      From clam faeces Summary In clam bed with fishery, oxidation reduction potential of surface sediment was twice due to bioturbation of clams and the amount of nutrients released to water was thrice, compared to the non clam zone. Beneficial effects on bio-geo-chemical are indicated in the presence of clam with fishery. The environmental quality indicators remained well within permissible levels in clam bed with fishery, improving the ecosystem processes simultaneously. Sustainable maintenance of clam beds with optimum fishery is necessary for the general ecological health of the Ashtamudi Lake. Mohamed, K S ;Venkatesan, V ; Kripa, V; Prema, D ; Joseph, M; Alloycious, P S; Jenni, B ; Valsala, K K ;  Saji Kumar, K K ; Ragesh, N ;Bose, J and Mohan, Anjana. 2013. Fishery Management Plan for Ashtamudi Lake Clam Resources അഷ്ടമുടിക്കായലിലല കക്ക സമ്പത്ത് ഒരു പരിപാലന പദ്ധതി. CMFRI Special Publication (114). pp. 1-48.  Prema, D ;Kripa, V ;Mohamed, K S ;Venkatesan, V ;Valsala, K K ; Joseph M; Alloycious, P S; Jenni, B; Anilkumar, P S ;Mohan A ; Bose J; Saji Kumar, K K and Ragesh, N. 2014. भारत के दक्षिण-पशिचम तट के अष्टमुडी झीऱ में अवसाद और पानी की गुणता के पररवेि में सीपी संस्तरों का ननर्ाारण. वविषे प्रकािन सं. 115 जऱीय पाररतंत्र का टटकाऊपन An appraisal of Sustainability of Aquatic Ecosystems (115). pp. 133-138.  Dame, Richard. F. 2012 . Ecology of Marine Bivalves : An Ecosystem Approach. Second edition. CRC Press. London. P. 271. Acknowledgements The authors are grateful to the Director, CMFRI for  providing facilities for the study. The work was  carried out with financial support from M/s GIZ, India (German International Cooperation). 

Role of Clams in Regulating Biogeochemical Processes of Ashtamudi Lake

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Role of Clams in Regulating Biogeochemical Processes of Ashtamudi Lake

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