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THE ESSEX NATURALIST
The Marine Fauna of the Blackwater Estuary and
Adjacent Waters, Essex
By D. S. Davis*
(Central Electricity Research Laboratories, Leatherhead)
Studies carried out on the Blackwater Estuary in connection with the
possible biological effects of Bradwell Power Station have provided
records of a wide variety of marine animals. The species identified are
listed with those recorded by previous workers and evidence given for
progressive natural changes in the fauna.
In 1959 biologists of the Central Electricity Research Labora-
tories and Ministry of Agriculture, Fisheries and Food began
investigations to observe the possible biological effects which might
arise from the operation of Bradwell Nuclear Power Station.
These investigations have continued up to the present time giving
the first major assessment of the fauna of the Blackwater Estuary
that has yet been made. Collections of biological material were
made from the many habitats within the Blackwater and Colne
as well as from immediate offshore areas, and a comparison has
been made with the few published records of collections made
previously.
A list of the marine algae has already been published
(Milligan, 1966) and so this paper will deal solely with the habitats
of the Blackwater and the fauna.
The area covered by the investigation includes the whole of
the tidal Blackwater, the shores of Mersea Island, the mouth of the
Colne, offshore to the Spitway and South to the North Buxey
Beacon. Most of the records come from that part of the Black-
water immediately above and below Bradwell Power Station as
this is of particular interest to the present investigation.
Fig. 1 shows the area involved, with the localities mentioned
in the Fauna List marked, and Fig. 2 shows the area of more
detailed study, with sampling stations numbered.
A GENERAL DESCRIPTION OF THE AREA
It is not intended to give here an account of the physical
conditions of the Blackwater but) certain basic characteristics
should be mentioned. The Blackwater is an inlet of the sea in
which truly estuarine conditions prevail only above Osea Island.
*Present address: Department of Biology, Dalhousie University, Halifax,
N.S., Canada.