ANNUAL FLUCTUATIONS IN THE ABUNDANCE OF MARINE ZOÖPLANKTON

¹ From the Department of Zoölogy, Wellesley College; the Department of Biology, Harvard University; and the Woods Hole Oceanographic Institution

The abundance of the zoöplankton in the waters overlying the continental shelf between Cape Cod and Chesapeake Bay is shown to be subject to severe annual fluctuations in respect both to individual species and to the total population. Yearly variations of this sort in British waters have been attributed to mass incursions of water from outside sources; but since no great annual differences in the exchange of water masses have been found in the coastal regions treated in this study, our data strongly indicate that important fluctuations in the plankton may occur in relatively undisturbed areas. These changes in the plankton are not found to be correlated directly with gross environmental changes and therefore must be due to an indirect action of physical or biological factors.