Natural densities (106 nematodes m-') of the free-living marine nematode Diplolaimella chltwoodi increased maximum rates of carbon mineralization of Gracilaria detritus by 300%; lower densities (104 m-'), by 100%. In the presence of nematodes increased mineralization was observed for 2 different particle sizes oof Gracilarja detritus, 63 to 100 and 250 to 308pm. In the absence of nematodes, there were only slight differences in mineralization rates between the 2 particle sizes. Nematodes also increased the rate of mineralization of Spartina detritus but to a lesser degree (50%). Meiofaunal nematodes can significantly affect benthic carbon flow by such an effect on the rate of detritus mineralization.

Detritus derived from marsh grass with high available caloric content was mineralized and incorporated by the polychaete Capitella capitata at a significantly higher rate than detritus from marsh grass with available caloric content more typical of naturally-occurring Spartina altemiflora. Detritus derived from vascular plant material is usually low in nitrogen content, so nitrogen enrichment via microbial activity may increase nitrogen content over time. Detritus research has emphasized the microbial role in protein enrichment. However, such detritus is also composed mostly of structural material not generally assimilable by macroconsumers. Microbial decomposition results in transformation products whose energy content is available to macroconsumers. Our results suggest that available energy and not necessarily nitrogen content, can limit the utilization of marsh grass detritus to the macroconsumer.

We monitored secondary production individual reproductive characteristics (l e reproductive penodicity female size fecundity, reproductive output) and oocyte standing crop d u n n g an oscillation cycle of a laboratory population of the opportunistic polychaete Capltella capitata type1 Biomass oscillation resulted from changes In the amount of food available per unit standlng blomass of C capitata During populatlon d e c h e reproduction and secondary producbon were reduced this conflrms that the population cycle was driven by food avallabllity Compansons of actual supplied ratlon vs theoretical estimate maintenance ratlon needed to support the populatlon suggested that the population was overshooting ~t s carrylng capacity However maxlmal populatlon biomass and denslty did not decline sharpely and were sustained over an 8 w k penod Decreases in production and reproduction rates preceding population decline are indicative of metabolic regulabon to adjust energetic requirements to available resources This observahon suggests that the population would not overshoot its carrying capacity When density was low, dally food ratlon exceeded the whole community requirements and food accumulated in the tray Unhl used, such bulld-up increases the amount of food avalable to C capitata, resulhng in an oscillating (actual) carrylng capacity above the static (theorehcal) carrylng capaclty calculated relatlve to the daily food-ration Our results suggest that the population did overshoot thls theoretical carrylng capacity but not the actual canylng capacity

Detritus derived from Spartind rlllerniflord (cordgrass), Grdcilaric, foliilera (red seaweed), and periphyton (mixed algae) was decomposed aerobically and anaerobically for various lengths of time and then fed to the polychaete Cdpilelld capilald in flow-through microcosms. Rates of detrital mineralization [CO, production), microbial respiration (0, consumption) and biomass (adenosine triphosphate and total adenylates, A,), and net incorporation by C. cdpitata varied with detrital source and length of pre-aging. Oxygen consumpt~on per unit microbial biomass (ymoles 1cgA;' d-') increased linearly with age of the detritus: periphytic algal detritus had the highest daily increase of 4 %, followed by G. foliiferd and S. dlterniflora detritus at 1 % and 0.3 % respectively. Metabolic respiratory quotient ( C 4 / O 2 ) , which varied from < 1 to about 5 0 . 1, was a function of detrital source and age; ~t indicated that anaerobic bacteria were important decomposers of detritus. Net incorpordtion rates by C. capitata, microbial biomass, and 0, consumption rates did not dlffer among G. foliifera detritus aged under oxic and anoxic conditions. Rates of CO, production, however, were up to 6 times higher for G. foliifera detritus aged anaerobically. The results suggest that a n a e r o b~c metabolism, which causes a high CO, production, could represent a sign~ficant loss of carbon from benthic food webs.

Juvenile Capitella sp. I were raised on 3 diets: a processed mixed cereal; benthic diatoms; and a green macroalgae. Accessory pigments from algal diets were translocated to developing oocytes. Worms fed mixed cereal produced eggs with no pigments; worms fed diatoms produced eggs with fucoxanthin, diadinoxanthln, diatoxanthin and pcarotene; worms fed macroalgae produced eggs with lutein, lutein cis-isomers and @-carotene. In addition to accessory pigments, chlorophylls and their breakdown products (pheaophytin and phaephorbide) and p-carotene anabolic products (canthaxanthin and echinenone) were also translocated to oocytes. The presence of intact chlorophyll a in eggs IS evidence that Capjtella sp. I can rapidly assimilate and allocate materials to reproduction. Given the importance of carotenoids in aquaculture diets, differences in oocyte carotenoid compositions may significantly alter growth and development rates of eggs produced on different food resources in field populations. In future studies, it may be possible to identify the food resources of opportunistic deposit-feeders from the biocheinical composition (fatty acids, sterols, and pigments) of their oocytes.