- Dona Paula, Goa, India.
- +91-0832- 2450327
- iiosc2020[at]nio[dot]org
| Abstract Submission No. | ABS-2022-09-0162 |
| Title of Abstract | Partitioning of economically important bivalves in a tropical estuary: significance of habitat characteristics |
| Authors | Dattesh V Desai*, Laxman Gardade, Lidita Khandeparker, A C Anil |
| Organisation | CSIR-National Institute of Oceanography |
| Address | CSIR-National Institute of Oceanography Dona Paula, Goa, India Pincode: 403004 Mobile: 9890376371 E-mail: ddattesh@nio.org |
| Country | India |
| Presentation | Oral |
| Abstract | Bivalves are benthic organisms inhabiting most of the coastal marine habitats, especially the estuarine tidal and mud flats. Due to their high stocking density and rich protein content, they form a major part of the artisanal fishery resource. In Zuari, a tropical monsoon influenced estuary along the west coast of India, bivalves Paphia malabarica inhabit the southern bank (Chicalim) and Meretrix casta inhabit the northern bank (Siridao) exhibiting distinct population partitioning. Although clam biology and their population dynamics have been addressed, the reasons for the partitioning of their population within the Zuari bay is not known and is addressed in this study. The nature of sedimentary organic matter was evaluated through analysis of various sediment parameters such as texture, organic carbon, the bacterial count, biochemical parameters and the same was also evaluated from the clam tissues. Fatty acids, which are source specific and commonly used as biomarkers were used to identify the sources of organic matter (OM) in the sediment and also in the clam diet. The abundance of P. malabarica at Chicalim and M. casta at Siridao was maximum during post monsoon (POM) season and minimum during pre-monsoon (PreM). A high content of total organic matter (TOM) and total organic carbon (TOC) was observed in the silty sediment at Chicalim as compared to sandy sediment at Siridao. The chlorophyll a content in the surface sediment at both the sites was almost similar. However, high protein (PRT) content at Chicalim suggested accumulation of OM derived from the water column phytoplankton. A higher contribution of heterotrophic bacteria to the total bacterial count (TBC) at Chicalim compared to Siridao during PreM and MON suggests their role in organic degradation. A low PRT to carbohydrate (CHO) ratio at Chicalim suggested input of degraded-detrital OM and heterotrophic nature of the ecosystem. A relatively high content of elemental (C, N & S) and biochemical composition observed at Chicalim compared to Siridao attributed to semi-enclosed nature, sediment grain size and influence of anthropogenic inputs. Although the PRT, CHO and lipids (LPD) were high in Chicalim sediment, the percentage contribution of LPD to the LOM was high at Siridao when compared to Chicalim and indicate nutritionally rich detrital input at Siridao. A degraded-detrital and aged OM, which is of low quality gets accumulated in Chicalim against the recently generated fresh OM with high nutritional value at Siridao. P. malabarica, a short necked clam is a facultative deposit feeder and M. casta is a suspension feeder. P. malabarica being a facultative deposit feeder, presence of fatty acids specific to diatoms in their tissues can be attributed to their feeding on both sediment and water column phytoplankton and their assimilation. Thus, the sediment characteristics driven by complex interplay of physical processes and the seasonal variation in the quality and quantity of food could be responsible in the distribution of these clam species. |