Subtidal micro and meiobenthic community structure in the Gulf of Kachchh

Abstract

Community structure of the micro- and meiobenthos of subtidal sediment from the Gulf of Kachchh were investigated during April 2002 (premonsoon season). Sediment samples were collected from 23 stations representing the entire Gulf area. A total of 25 microbenthic and 13 meiobenthic groups were recorded. Microbenthic density ranged from 53-19590 no. 3.3 cm sup(-2) (mean = 5448 plus or minus 5220; n = 23) in top 2 cm sediment layer and was mainly dominated by benthic diatoms (e.g Coscinodiscus and Navicila spp.). The total meiobenthic population in the top 5 cm sediment layer ranged between 27 to 1664 no. 10 cm sup(-2) (mean = 440 plus or minus 474; n = 23). The major groups in meiobenthos included Nematoda, Harpacticoida, Oligochaeta, Turbellaria and Polychaeta. The vertical distribution of meiobenthos indicated that more than 52% population occurred in upper 0-2 cm sediment layers. Nematode/copepod (N/C) ratio was high at the near shore stations located in the northeast sector and was mainly due to the increased abundance of deposit feeding nematodes. The high N/C ratio (greater than 60) at the shallow coastal stations reflects on the polluted/disturbed conditions having abnormally high organic loading in that area. This study suggests that, although the sedimentary and environmental setting in Gulf of Kachchh were not conducive for meiofaunal colonization, however, the higher standing stock of microbenthos indicates that conditions were appropriate for microbenthic proliferation. Hence, it is revealed that, in the absence of metazoan meiofauna, microbenthos (partly referred to as "Secret Garden" of shallow water unvegetated marine habitat) may act as an additional source to meet the required carbon demand at higher tropical level.