Experimental Studies of the Survival of Zooplankton: Short Term Effects of High Population Densities in an Artificial Environment

摘要

Net samples of live zooplankton were collected from Fishers Island Sound in mid December 1984 for the purpose of determining the mortality due to net capture and the short-term effect on organism survival of high population densities in an artificial environment. The contents of two series of five net tows each were placed in two separate insulated coolers containing 30 liters each of filtered sample-site water. The resultant concentrations in the two containers were equivalent to 7.2 x 1,000,000 and 15.65 x 1,000,000 of live organisms per m3 , respectively. Counts of living and deal individuals in sub-samples withdrawn periodically from container 1 and 2 revealed mean mortality rates of 24 and 18 percent, respectively, over the first 8 hours after capture with an overall mean mortality of 21 percent. Twenty-six hours after capture overall mortality averaged 58 percent and after 47 hours all organisms were dead. Net mortality, which was estimated from counts made at 2.5 and 3 hours after capture averaged 17 percent in each container. During the course of experiments it became clear that tidal currents can markedly influence the volume of water filtered by each new tow as well as the total content of zooplanktonic organisms.