Table 4. — U.S. institutions, investigators, and projects in Controlled Ecosystem Pollution Experiment 



Institutions 



Investigators 



Projects 



University of Alaska, 

 Marine Science Institute 

 University of California at San Diego, 

 Institute of Marine Resources 



University of Georgia, 



Skidaway Institute of Oceanography 



J. J. Goering and 

 A. Hattori 



J. R. Beers 



W.H.Thomas 



F. Azam 



D. W. Menzel 



H. L Windom 



University of Miami, Rosenstiel School of M. R. Reeve 



Marine and Atmospheric Science 



Woods Hole Oceanographic Institution G. W. Grice 



Nitrogen and Silicon Regeneration in Controlled 



Aquatic Ecosystems 



The Role of Microzooplankton in an Environmental 



Effects Program 



Effects of Pollutants on Marine- Phytoplankton 



Role of Bacteria in Polluted Marine Ecosystems 



Integrated Field Studies and Operations 



Heavy Metal Variations in Natural and Polluted 



Ecosystems 



The Role of Zooplankton in an Environmental 



Effects Program 



Zooplankton Population Assessment 



experiments, on the other hand, showed that after 50 days, 

 depletion of the toxicant in the water column or a change in its 

 chemical form permitted a bloom of diatoms that was much 

 higher than in controls. As the zooplankton population had not 

 had time to recover from its initial decline following mercury 

 addition, it is probable that reduced grazing pressure was the 

 cause of the diatom bloom. These results show that there is 

 little likelihood that laboratory experiments can predict anything 

 but very short-term consequences even for phytoplankton. 



The concentrations of mercury and copper at which effects 

 did not differ from the control and those at which major popu- 

 lation changes (mortality) occurred were for all practical pur- 

 poses so close (between 1 and 5 ,/xg/l in both cases) that it is 

 unlikely that subtle or chronic effects can be detected at the 

 population level. This statement is strongly qualified to apply 

 only to the time scale studied (80 days in this case) and directly 

 contradicts laboratory results that indicate that mercury was 

 three to six times more toxic to zooplankton than copper. 



The sequence of events in phytoplankton and microzooplank- 

 ton succession produced by the imposition of a pollutant stress 

 do not appear to differ from those that occur over much longer 

 periods of time in Saanich Inlet in response to natural changes 

 in environmental conditions (light, nutrients, etc.). Any change 

 in the biological, chemical, or physical characteristics of an en- 

 vironment obviously elicits responses from the biological com- 

 munity. Most commonly, such changes cause shifts in species 

 diversity. The natural sequence manifests itself first at the pri- 

 mary producer level following a reduction of nutrient levels in 

 the water column. These changes force the succession of phyto- 

 plankton populations from relatively large centric diatoms to 

 small phytoplankton (< 10 ^m). This course of events is in- 

 duced either by pollutant stress (copper, mercury, and oil), re- 

 duced vertical mixing in the CEPEX enclosures, or increased 

 vertical turbulence (where phytoplankton are mixed below the 

 compensation depth), when high nutrient concentrations are 

 present (winter) or when nutrients are depleted (summer). 



In addition to the above generalizations derived from exam- 

 ining the interactions of biological communities, CEPEX ex- 



periments provide valuable information on the biologically 

 mediated behavior of trace elements. As expected, the residence 

 time of copper in water was greater than mercury, because mer- 

 cury more readily adsorbs to particulate matter. Mercury was 

 removed from solution exponentially with time, and rates of 

 removal were a direct function of the rate of production. 

 More than 90 percent of the total mercury was associated 

 with organic matter with a molecular weight > 10,000, and 

 its toxicity was mediated by the same organic matter. Direct 

 adsorptive uptake of mercury was rapid, and the primary 

 mode of accumulation was by zooplankton and probably 

 fish. Uptake from food was less important. The rate of 

 depuration of accumulated mercury was slow. No evidence was 

 found for biomagnification in the food chain, and no methylated 

 mercury was found in the fish. 



In another experiment, a mixture of trace metals (arsenic, 

 antimony, chromium, copper, cadmium, lead, mercury, nickel, 

 selenium, and zinc) was added to the enclosures. The concen- 

 tration of each element was adjusted to values typical of many 

 East Coast estuaries, but higher than those found in Saanich 

 Inlet. Tintinnid populations disappeared, and the biomass of at 

 least one species of larger zooplankton was reduced as was the 

 growth of young salmon. The rate of removal of the elements 

 from solution were in the order of zinc, mercury, lead, copper, 

 cadmium, nickel, and arsenic. Other element concentrations 

 before and at the conclusion of the experiment remain to be 

 analyzed. Copper, lead, and mercury were highly enriched in 

 samples containing surface active organic matter isolated by 

 flotation techniques. The presence of these surface active organo- 

 metallic complexes is to some extent affected by biological 

 events. 



Further efforts in CEPEX will be directed primarily to test 

 the hypothesis that the effects of stress on biological communi- 

 ties, whatever their cause, follow a common sequence of events. 



Volume 27 of the Bulletin of Marine Science and Volume 3 

 of Marine Science Communications are devoted entirely to 

 CEPEX papers. Other papers describing the effects of mercury 

 will appear in Volume 4 of Marine Science Communications. 



18 



