structure of estuarine systems. No interference was anticipated or 

 evident in these carbon uptake studies since we used relatively 

 "inert" Si02 particles (see App.). Nevertheless, future work should 

 research the effects of these factors in addition to the effect of 

 light attenuation on productivity of phytoplankton species, groups of 

 species, and natural populations. 



II. EFFECTS OF SUSPENDED SEDIMENTS ON FEEDING ACTIVITY OF 

 THE COPEPODS EURYTEMORA AFFINIS AND ACARTIA TONSA 



1. Introduction . 



Suspension feeding estuarine organisms are exposed to high sus- 

 pended sediment concentrations at times. Mechanical or abrasive 

 action of suspended particles causes gill clogging, impairment of 

 respiratory and excretory functioning, and reduced feeding effective- 

 ness. In strongly agitated water a substantial part of the suspended 

 materials consists of fine sand, silt, and clay-sized particles which 

 have been resuspended from the bottom. Considerable quantities of 

 these inorganic (mineral) solids can enter the gut of filter-feeding 

 aquatic organisms with particulate food. 



This section presents results of studies on the interference of 

 suspended mineral solids and resuspended natural sediments with the 

 feeding activity of the calanoid copepods Eurytemora affinis and 

 Aaartia tonsa (typical Chesapeake Bay zooplankton) . 



2o Materials and Methods . 



a. Zooplankton Cultures . Cultures of E. affinis and A, tonsa 

 were made available for this project by Dr. Don Heinle and Mr. Joseph 

 Ustach, Chesapeake Biological Laboratory, Solomons, Maryland. Cul- 

 tures were held in a constant temperature incubator at 20° Celsius 

 under constant cool white fluorescent illumination (0.8 x IQ** ergs 

 cm"^ sec"-"-] in Erlenmeyer flasks (2-liter capacity) containing 2 

 liters of Patuxent River water (salinity range 5.5 to 7.5 parts per 

 thousand) which was filtered previously through sintered Whatman GFC 

 glass fiber-filter pads. 



The zooplankters initially were fed a mixed diet of the motile 

 chrysophyte M. lutheri and the bacillariophyte Phaeodaotylim 

 trioomutum. Cell concentrations of these phytoplankters were main- 

 tained within a range of 5 x lo"^ to 1 x 10 cells ml"'^ in the 

 zooplankton cultures. Erratic feeding rates during initial feeding 

 experiments coupled with the "blooming" tendency of the P. 

 trioomutum in the zooplankton cultures caused the diet of these 

 cultures to be limited to M. lutherij especially during the days pre- 

 ceding a feeding rate experiment. 



Every third or fourth day, one-third to one-half of the water in 



