From the start of 2022 Mark Woombs, Jean Wilson and myself have been sampling plankton every fortnight from the river Wyre estuary at Knott End. The intention of this study is to refresh our understanding of plankton diversity and dynamics in the Bay area, and contribute to studies on the health of the River Wyre. Phytoplankton – microscopic marine plants – are the base of the marine food web, and contribute approximately 50% of the oxygen we breathe, whilst quietly sequestering atmospheric carbon dioxide. Zooplankton are (generally microscopic) animals that convert phytoplankton biomass into food that is accessible to the rest of the animals in the world’s oceans.

In estuarine systems there is never really a shortage of plant neutrients. As a consequence there is the opportunity for phytoplankton to be present in high numbers from early spring, as light levels and surface water temperatures rise, through to late autumn, when grazing combined with lowered growth rates (due to reduced light and temperature) finally cut the poulations back.

This does not mean, however, that the same phytoplankton species dominate our samples throughout the year. In fact, our study to date has revealed a dynamic interplay between phytoplankton species, with different species commming to dominate the total population in succession. The most likely cause of the species population collapses is disease, rather than grazing, though we only have direct evidence for this in one of our phytoplankton families, the Coscinodiscus, where the appearance of the fungal disease Lagenisma coscinodisci in late May coincided with a decline in the numbers, particularly of C. wailesii, which had been the dominant member of the Coscinodiscus to that point.

Plankton species taken during the sampling program were used to illustrate our talk to the Royal Society of Biology on 21st May, but we will have a more complete picture of plankton activity in the Wyre at the end of the year, and hope to present this work in more detail then.

Barry Kaye, Lancashire MCS