Some Notes on the Plankton of the Thames Estuary

Abstract

THE precise limits of the estuary of the River Thames are not easy to define. The Thames Conservancy's eastern limit (Crowstone to Yantlet) is generally acknowledged as forming the end of the river itself, although, geographically and physically, the head of Sea Reach makes a more satisfactory boundary. The western limit, however, is the subject of some controversy. The jurisdiction of the Port of London Authority extends to the meridian of Havengore Creek and for Custom's purposes the Estuary extends to a line drawn from Reculver Towers on the Kent coast to a point just below Clacton-on-Sea on the Essex side. A glance at the chart of the area in question (Fig. 1) will show that the typical estuarine sandbanks continue some miles farther eastward. For this reason, doubtless, Captain Tizard, R.N. in his Hydrographical Surveys in the Triton, 1882-9, gives the eastern boundary as being a line from the North Foreland, Kent, to Harwich, Essex, via the Kentish Knock Lightvessel (Fig. 2). The Company of Free Fishermen of the River of Thames', and indeed all ruling bodies of that river since Norman times, also gave the aforementioned line as the limit of their jurisdiction and for the purposes of this paper that limit will be assumed. The Second Ice Age, it is generally agreed, was responsible for the present peculiar formation of the Estuary. The north-east trend apparently results from the course of the river, when, with the Rhine, it flowed (supposedly) through what is now the North Sea. The supposition is that with the rapid