Recovery of deep-sea meiofauna after artificial disturbance in the Central Indian Basin
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Colonization of deep-sea (5000–5500m depths) metazoan meiofaunal assemblage (in terms of abundance and community structure) was investigated in the Central Indian Ocean Basin (CIOB), immediately after and also 44 months after a benthic disturbance experiment. The abundance of nematodes, which normally dominate the deep-sea meiofauna, was reduced (by 50%; p is less than 0.001) in postdisturbance. The density of meiofauna was generally low during the monitoring phase and varied moderately inside and outside the test area (experimental site). The density values ranged from 8 and 52 no. 10 cm sup(-2) (mean: 23.5 plus or minus 12.2 SD; n=12) in the impacted area. There was steady buildup in nematode population in the test area between the experiment and the monitoring observations 44 months later, as compared to other metazoan density. Meiofauna were vertically recorded down to the 30–35-cm sediment layer during the monitoring. Although, the bulk of meiofauna (80%) occurred in the top 20 cm sediment layer of the reference area, only 16% of the fauna was observed above 0–2 cm. On the contrary, >30% metazoan population occurred in the 0–2 cm section in the test area. Bringing up nutrients from subsurface and depositing this organically rich material on the sediment surface, could have acted as a stimulating factor for meiofaunal recovery as most of the meiofauna feed on bacteria and dead organic material (DOM). This experimental study suggests that, whereas commercial mining of the deep-sea mineral resources may affect deep-sea benthic communities immediately after the impact, the availability of food due to turn over (similar to plowing) of sediments may help recolonization on a temporal scale.
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