Abstract.The effect of different levels of organic enrichment on benthic productivity was studied over a 16‐week period in trays of sediment placed in a fertilized seawater pond. Primary and secondary planktonic production were also monitored. The exploitation of these sources of food by juvenile sole and their growth and survival over an 8‐week period were assessed.The colonization of the sediments showed a marked succession. Nematodes were numerically the most abundant group and reached a peak after about 8 weeks. This was followed by a peak in the abundance of epibenthic copepods after 11 weeks. The maximum numbers of poiychaetes and larger Crustacea (mainly amphipods) occurred at the end of the trial (15 weeks). The high‐organic sediment supported fewer polychaetes and copepods than either the low‐ or medium‐organic sediments. The species composition of the benthos varied both with the level of organic enrichment and with time. Peaks of zooplankton concentrations of 23 to 25 organisms/l occurred during the spring and late summer. There was some evidence of an inverse relationship between zooplankton abundance and standing crop of algae, as indicated by chlorophyll a concentrations.Harpacticoid copepods were the dominant food item consumed by small (21‐50mm total length) sole. Polychaetes, amphipods and Crangon spp. were exploited by large (61‐90mm total length) sole to a much greater extent, though harpacticoid copepods were also commonly taken.The percentage increase in length of the juvenile sole at low‐, medium‐ and high‐organic levels was 108, 146 and 152 respectively. Survival, however, was highest (100%) on the untreated sediment and lowest (57%) at the m