Notes on the Plankton observed at Plymouth during June, July, August and September, 1892

Abstract

The absence of systematic records showing the variations of the floating fauna and flora, or plankton, of the Plymouth waters is much to be regretted. My observations on the amount of animal and plant life suspended in the sea from the surface to the bottom would show that in comparison with similar observations made elsewhere, the quantity of plankton in this locality was during the past summer surprisingly small. The absence of data upon which comparisons could be based between the state of the water in this season and that obtaining in former years is all the more to be deplored because the present season has in many respects been a remarkable one. In the first place, the Plymouth mackerel fishery has so far been a complete failure; it has further been found that dog-fishes (both Scyllium and Acanthias) were not obtainable during June and July; and lastly, Aurelia aurita, which in summer is usually common, was extremely scarce in the Sound and tidal waters of Plymouth. If my Burmise that the amount of plankton was for the locality exceptionally small proves correct, then these three salient instances of scarcity of animals which are directly or indirectly dependent on the plankton for their food will suffice to show the importance of a series of more or less continuous observations on the physical and biological condition of the inshore and Channel waters. Were accurate information on these points available, it would in all probability enable us to explain, and we might even in time be able to foresee, the occurrence of so important an event as the exceptionally sporadic appearance of the mackerel in 1892.