Meiofauna-mangrove interaction: A pilot study from a tropical mangrove habitat

Abstract

We studied meiofauna in the sediments and on the surface of roots of four mangrove vegetation types in Chorao island, Goa, Central West coast of India. A total of 14 taxa were recorded from the mangrove roots while 12 taxa from the sediments. Nematodes dominate in the sediment of all vegetation and the density ranged from 71.2-76.3%. Like sediments, nematodes also dominated the mangrove roots and their contribution was in the range 48.5-61.6% followed by harpacticoids (30.9-36.9%). However, compared to sediments, their density was quite low per 10 cm sup (-2). The total meiofaunal densities in the sediments of four mangrove vegetation types are less: 519.5 +/- 343.12 ind.10 cm sup (-2) in Sonneratia, 343.5 +/- 283.13 ind.10 cm sup (-2) for Rhizophora , 208.08 +/- 68.21 ind.10 cm sup (-2) for Avicennia and 166.16 +/- 66.44 ind.10 cm sup (-2) in Bruguiera. Among different vegetation, roots of Sonneratia had the largest density(31.45 +/- 19.29 ind.10 cm sup (-2)), followed by Bruguiera (22.81 +/- 18.04 ind.10 cm sup (-2)), Avicennia (11.55 +/- 7.92 ind.10 cm sup (-2)), with the lowest in Rhizophora (10.66 +/- 5.89 ind.10 cm sup (-2)). A significant variation was detected (P < 0.01)in the meiofaunal density of the four mangrove vegetation types. A vertical profile of meiofauna in each vegetation suggested that the upper 5 cm of mangrove sediment contains > 90% of the total meiofauna. The vertical variation of meiofaunal density was also strongly significant (P < 0.001). However, from the Rhizophora sediments, nematodes were found to live below the Redox Potential Discontinuity (RPD) layer which is considered a hostile biotope. Future studies should consider these thiobiotic species (below the RPD layer), which are generally neglected. Investigation of their taxonomy, ecological interactions and physiological mechanisms for adaptation will provide a better insight about the role of the RPD layer and in what way they are different from the oxybiotic species (above the RPD layer). Studies pertaining to sedimentary characteristics of different vegetations will deepen our knowledge on meiofauna-mangrove interaction.