NUMBER TWENTY NINE - OCTOBER 1998

Box 1: the birth of the refuge concept

Sometimes, routine observations on particular lakes can provide important clues in the development of the theory of a subject. In the early 1980s, a research assistant, Mark Timms and I noticed big differences in summer in two linked basins of one of the Norfolk Broads. Hoveton Great Broad, fed by water from the waste-water effluent-rich River Bure, had a main basin and a smaller basin, called Hudsons Bay, connected with it and also directly with the river (see map). The main basin was turbid and had only a few clumps of water lilies left from a near complete coverage with plants in the 1960s. Hudsons Bay, in contrast had retained (we do not know why) thick stands of lilies and there was only a small area of open water. In summer this water was extremely clear, but the clarity disappeared when the lilies died back in late summer and phytoplankton populations then developed. Mark was instructed to stay up all night and to take regular samples, which showed that large numbers of zooplankters appeared in the open water of Hudsons Bay. These emerged from large populations present by day in the lily beds and these observations were among the first from which the concept of zooplankton refuges was born.