Macrofaunal communities of a unique sedimentary environment: The Alappuzha mudbank, southwest coast of India
Author
Razaque, M. A. A.
Jaleel, A.K.U.
Ragesh, S.
Panda, N.
Arya, K. S.
Gireeshkumar, T.R.
Muraleedharan, K.R.
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Mudbanks are unique, transient coastal phenomena characterised by calm, turbid waters and high productivity, frequently reported along the southwest coast of India, especially along the Kerala coast. The Alappuzha mudbank, located away from riverine inputs, becomes active during the southwest monsoon. Previous studies on this mudbank have largely focused on primary and secondary production and fisheries, while information on other biotic components, especially benthic invertebrates that play crucial functional roles in marine ecosystems, remains limited. The present study examines seasonal variations in the macrofaunal community of the Alappuzha mudbank. Depth-stratified samples were collected from November 2021 to October 2022, covering pre-monsoon, monsoon, and post-monsoon seasons, at depths from 3 to 8 m. Macrofaunal abundance varied between 0 and 7625 ind./m2 with an average value of 510 ± 1413 ind./m2. Unlike typical coastal systems, the total macrofaunal standing stock was lowest (100 ± 118 ind./m2) during the mudbank (monsoon). The highest abundance was recorded during the post-monsoon season, with a mean value of 973 ± 2199 ind./m2. Biomass of total macrofauna followed the same trend, with monsoon months recorded the lowest values (1.8 ± 1.8 g/m2) followed by post-monsoon (3.2 ± 3.6 g/m2). Polychaetes, crustaceans, and molluscs were the dominant groups, with polychaetes accounting for 86 % of total abundance and biomass. Paraprionospio pinnata, Cossura coasta, and Lumbrineris meteorana were the dominant, stress-tolerant species. This study revealed a reduction in macrofauna during the active phase of the Alappuzha mudbank, which may be due to unconsolidated and unstable substratum, which results in minimal trophic support to the demersal fishery.
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