EFFECTS OF MANIPULATION OF FOOD-SUPPLY ON ESTUARINE MEIOBENTHOS

A comparative mesocosm experiment was carried out to determine the eff ects of natural foods of different quality and quantity on the structu re of natural meiobenthic communities collected in undisturbed sedimen t from the polluted Westerschelde and the comparatively undisturbed Gi ronde estuaries. Nematode communities are more diverse and species ric h in the latter estuary. The organic matter or foods used were phytopl ankton, green alga, salt marsh plant detritus and leaf litter detritus which were added at three dose rates including a high dose. There was no change in community structure in response to the treatments in eit her of the estuarine meiobenthic communities. Analysis of all the resu lts from this experiment indicate that the food quantity manipulations had almost no effect on the deposit feeding meiofauna. It may be that the reserves of organic matter within the sediment were sufficient to satisfy their dietary requirements for the duration of the experiment . The abundance of diatom/epigrowth feeding nematodes which were initi ally dominant in the Gironde, declined substantially suggesting that t hey may have been food limited since diatoms were not among the source s of organic matter added to the mesocosm. There was no specific respo nse to the five different types of organic matter added to the mesocos m.