Meiobenthos of the discovery Bay Lagoon, Jamaica, with an emphasis on nematodes.

Abstract

Sediment granulometry, microphytobenthos and meiobenthos were investigated at five habitats (white and grey sands, backreef border, shallow and deep thalassinid ghost shrimp mounds) within the western lagoon at Discovery Bay, Jamaica. Habitats were ordinated into discrete stations based on sediment granulometry. Microphytobenthic chlorophyll-a ranged between 9.5- and 151.7 mg m-2 and was consistently highest at the grey sand habitat over three sampling occasions, but did not differ between the remaining habitats. It is suggested that the high microphytobenthic biomass in grey sands was related to upwelling of nutrient rich water from the nearby main bay, and the release and excretion of nutrients from sediments and burrowing heart urchins, respectively. Meiofauna abundance ranged from 284- to 5344 individuals 10 cm-2 and showed spatial differences depending on taxon. Of 22 higher taxa recorded, nematodes dominated followed by copepods, together accounting for ~80 % of all individuals. Both taxa were most abundant in grey sands, suggesting a response, either directly or indirectly, to the high microphyte biomass. Significant withinhabitat spatial variability in both meio- and microphytobenthos was found, causes of which are discussed. Nematode feeding groups varied between habitats. Fine white sands and both thalassinid mound habitats were dominated by non-selective deposit feeders. Slender and plump nematode morphotypes were found, yet the plump morphotype was largely absent from coarse sands subjected to high wave swash at the backreef border habitat. Here, nematode lengths were significantly higher than at other habitats. Nematode biomass spectra differed significantly between habitats, with a shift in peak biomass values towards larger size classes in the disturbed sediments. It is suggested that 3 longer and larger nematodes represent an adaptation to sediment disturbance, helping to prevent being displaced from the benthos by hydrodynamic forces and bioturbation.