Ecology of Duck Pond, Wellfleet, Massachusetts with special reference to the vertical distribution of the zooplankton

Originally issued as Reference No. 58-43, series later renamed WHOI- .

During the summers of 1956 and 1957 an investigation was made ofcertain ecological relations involving light in Duck Pond, Wellfleet,Massachusetts, because of the unusually high clarity of the water. Themaximum transparency observed (extinction coefficient, k = 0.11) was fargreater than most ponds and about equal to that in the slope waterbeyond the continental shelf off the Atlantic coast. The illuminationreaching the bottom of the pond at 18 m was 11% of the surface light andmade possible a thick growth of Sphagnum at that depth. Phytoplanktonwas scarce and consisted mostly of minute forms. The zooplankton, whichranged in abundance up to 78 organisms per liter, consisted almostentirely of one species of copepod, Diaptomus minutus Lillj. Quantitativesampling of this population by means of a pump at a series of depths andat various hours of the day revealed a partial migration of this speciesfrom near the bottom to the surface at sunset on one occasion, but nolarge fraction of the population carried out a vertical migration on 4other sunset periods or 2 sunrise periods subsequently studied. Oncertain of these occasions, however, there was a slight but detectib1emovement of the animals toward the surface at sunset followed by aredistribution to deeper levels. At sunrise the animals showed a tendencyto move at first toward the surface and then away from it, althoughon one occasion the population remained quite evenly distributed at alllevels. It is pointed out that because of the high transparency thosezooplankters living in the pond are able to withstand high illuminationat all depths. Relations between the extreme water clarity and the activitiesof the zooplankton, as well as other unusual features of the pondare discussed.

Work supported by funds from theNational Science Foundationunder Grant No. 3838