The relationship between field distributions and feeding behavior of a marine harpacticoid copepod, Pseudobradya sp

This study examined the relationship between the microscale distributions of the harpacticoid copepod, Pseudobradya sp. on an intertidal mudflat and the feeding behavior of these copepods, as observed in the laboratory.; The distribution of the copepods was analyzed in two 5 x 10 matrices of cores (area = 272 cm{dollar}sp2{dollar}) taken on two separate dates. Spatial autocorrelation analysis indicated that the copepods were aggregated in dense patches of greater than one cm{dollar}sp2{dollar} in area, superimposed on less dense patches of about nine cm{dollar}sp2{dollar}.; The primary food of this species was determined through measurement of the copepods' absorption efficiency on benthic microalgae and bacteria. Using a dual radiolabelling technique with {dollar}sp{lcub}14{rcub}{dollar}C and {dollar}sp{lcub}51{rcub}{dollar}Cr, absorption efficiency on algae was found to range, on average, from 40% to 85%. Absorption efficiencies and carbon absorption rates increased with increasing algal concentration in the offered food. Average absorption of bacteria was within the range seen for algae, about 71%. Given the smaller amount of bacterial biomass in a volume of sediment, however, the carbon absorption rate of the copepods on this food source was extremely low. It was concluded that Pseudobradya sp. is deriving most of its carbon from benthic microalgae.; In order to determine if an aggregated food source could result in an aggregated distribution of Pseudobradya sp., the behavior of the copepods in response to sediment patches containing food of varying quantity and quality was observed. Pseudobradya sp. spent significantly greater total time and time feeding in sediment patches (area = 1.27 cm{dollar}sp2{dollar}) which were 18-20x enriched in benthic algae compared to the alternate choice. Sediment which was passed through the gut of the deposit-feeding gastropod, Hydrobia truncata, contained 50% less microalgae than undigested sediment but there was no significant difference in the total time or time feeding by Pseudobradya sp. between these two sediment types. There was no significant difference in total time or time feeding by Pseudobradya sp. between fresh sediment and fresh sediment to which algal exopolymer had been added, either. It was concluded that Pseudobradya sp. can behave to maintain itself within a patch of sediment of at least 1.27 cm{dollar}sp2{dollar} if the difference in algal concentrations between that sediment and the surrounding material is somewhere between two and 18x higher.