LIGHT 



I 



NETPHYTOPLANKTON 

 DIATOMS 



OYSTERS 

 LIGHT & CLAMS 



i. 



NANNOPHYTOPLANKTON 

 DINOFLAGELLATES 



I 



DISSOLVED 

 INORGANIC 

 N. P. & C 





DISSOLVED 

 ORGANIC 

 &C 



T 



BENTHIC 



DECOMPOSERS 



MICROFAUNA 



NET ZOOPLANKTON 

 COPEPODS 



FISHES 



CTENOPHORES 

 & JELLYFISH 



MICROZOOPLANKTON 



ROTIFERS 



TINTINNIOS 



BACTERIA 



FUNGI 



PROTOZOA 



OYSTERS 

 & CLAMS 



OETRITUS 

 (PARTICULATE 

 ORGANIC 

 CARIONI 



T 



BENTHIC 



FILTER 



FEEDERS 



Figure 4. Conceptual model of plankton and nutrient interactions. 



Zooplankton also can be considered in two size 

 classes, the larger or net zooplankton such as cope- 

 pods, and smaller or microzooplankton such as tin- 

 tinnids and rotifers. In the upper Patuxent River, 

 zooplankton must consume detritus because plant 

 production in situ is not sufficient to support them 

 (Heinle and Flemer 1975); in the middle Bay, larger 

 zooplankton eat only about 10 percent of daily net 

 primary production (Heinle, pers. comm.). What 

 happens to the rest of the production? Figure 4 

 shows one possible microzooplankton-dissolved in- 

 organic N, P, C-nannoplankton loop whose mecha- 

 nism for consumption and rapid regeneration of nu- 

 trients in the euphotic zone would facilitate rapid 

 turnover of the plankton community, but its exis- 

 tence has not been demonstrated (Heinle, pers 

 comm.). 



Zooplankton tend to maximize living material in 

 the diet, and can eat bacteria (Heinle, pers. comm.). 

 Bacteria and protozoa can take up inorganic (as 

 well as organic) N and P, and may be competing 



with phytoplankton for nutrients (Webb, pers. 

 comm.). Bacteria and fungi can break down cellu- 

 lose and chitin, the main components of detritus 

 (Webb, pers. comm.). 



Plankton must be viewed in the context of or- 

 ganic and inorganic nutrient dynamics. Nutrients are 

 affected not only by plankton, but also by excretion 

 by larger organisms, absorption and regeneration 

 through chemical processes in sediments, regenera- 

 tion by biological processes in the euphotic zone 

 and benthos, and by physical transport. There are 

 still many questions about nutrient dynamics in the 

 Bay system, and figure 4 should be regarded as ex- 

 pressing present hypotheses. Plankton are usually 

 viewed as the starting point of a food web, but 

 they are one step in a nutrient-cycling loop that in- 

 volves the whole Bay system. 



One other aspect of plankton and nutrient dy- 

 namics involves tidal exchange of water between 

 the Atlantic Ocean and the Chesapeake Bay at the 

 Bay mouth. Studies of the tidal exchange are under 



