In the process of calcification in the coralline algae, Clathromorphum and Corallina, the energy is derived from photosynthesis; the outer surface evolves carbon dioxide while calcium carbonate is deposited between the algal filaments. Evidence suggests that calcification may be brought about essentially by separation of acid and base followed by preferential removal of an acid component in the form of carbon dioxide.

These algae show strong oxidase, catalase and carbonic anhydrase activity, consistent with the processes postulated. The calcified algal thallus is normally reducing. Platinum electrode potentials, Eh, measured on and immediately below the outer surface of fresh and healthy Clathromorphum crust following abrasion ranged from 50 to 100 mV, some 150–370 mV negative to that of the surrounding water at the time. These potentials in the alga were most reducing after the material had been exposed to strong sunlight. Eh potentials, measured by electrodes of platinum foil attached to the outer surface of Clathromorphum in such a way as to shield it from light and from gaseous exchange from the sea water, reached values between 113 and -182 mV, or up to 480 mV negative to the Eh of the surrounding sea water.

Oxidation of crude suspensions of crushed fresh material showing reducing activity resulted in the production of base by removal of hydrogen ions. The amount of base so formed was greater when suspensions were first incubated out of contact with air for periods of up to several days, reducing conditions being enhanced by respiration of the alga alone or in conjunction with bacterial growth.

Using the mouse bioassay for paralytic shellfish poison (PSP), the distribution of toxicity among 23 dinoflagellate species was studied. Special consideration was given to red-tide-forming species and to those species previously implicated as causative organisms in paralytic shellfish poisoning. Among those investigated were ten marine species of the genus Gonyaulax, previously known to contain three toxic species. The presence of PSP was detected only in Gonyaulax species of the section Catenella. The amount of toxin varied in different species, ranging from 0.05 to 24 pg/cell. The amount of toxin per cell also varied with the phase of growth (exponential or stationary) in the New England red-tide species, G. tamarensis var. excavata Braarud.

A simple data acquisition and control system has been developed for the measurement of the spectral emission from bioluminescent animals. A programmable calculator system is used to control a monochromator and to measure, record and graphically display the results. Results from calibration sources and three animals are described with comments on the success of the technique.

A non-linear numerical model is used to derive both the maximum bottom stress and the mean stress on the shelf sea-bed around Britain, due to tidal streaming. It is shown that these two vector distributions will be important in sand transport studies. It is further expected that the results will be relevant to other benthic studies.

Towards the end of August 1978 SCUBA divers studying a rocky area in Mounts Bay noticed numbers of dead and dying fish and invertebrates in their study area. Their observations were passed on to Dr G. W. Potts (Griffiths, Dennis & Potts, see below, p. 520). Samples of the sea water, which appeared to be very rich in phytoplankton, were taken but unfortunately were too poorly fixed for the identification of naked dinoflagellates. At the same time a number of reports of‘red tides’ and ‘fish kills’ in Mounts Bay were being passed to Mrs Stella Turk of Camborne.

During the first 2 weeks of September 1978, high mortalities of intertidal populations of several ‘bait’ species, notably lugworms, were reported to the Plymouth Laboratory by anglers along the south coast of Cornwall. In the same period, abnormally high numbers of the red-band fish, Cepola rubescens, were caught in the trawls of the Laboratory's research vessels (Dr A. J. Southward, personal communication). In addition, some 20–30 specimens of another burrowing species, Amalosoma eddystonense, were taken in several trawls on the Looe Grounds; this was rather surprising since this large echiuran was thought to be rare in the Plymouth area (Dr P. E. Gibbs, personal communication).

The author also received reports indicating that the non-photosynthetic but luminescent dinoflagellate Noctiluca scintillans (Macartney) Ehrenb. was abundant in coastal areas of the western English Channel. This organism is well known for forming slicks varying in colour from orange to blood-red (Le Févre & Grail, 1970; Grail, Le FévreLehoerff & Le Févre, 1971).

Reports from anglers and divers indicated that in late August and September 1978 a substantial mortality of the bottom fauna and fish had occurred in the bays along the south coast of Cornwall, particularly in the St Austell area. It was therefore decided to carry out an investigation by diving and at the same time collect water samples from affected areas for further analysis. The following notes record the observations made during the period 19–28 September at various localities but mainly in St Austell Bay (see Fig. 1).

Since May 1977 the Penzance Branch of the British Sub-Aqua Club has carried out a routine survey, as a contribution towards the Underwater Conservation Year Programme, on the fauna and flora of a sublittoral reef situated about 300 m to the south west of the Gear Reef in Penzance Bay. The reef is situated in water of about 17 m depth and is generally surrounded by firm sand with patches of Zostera. The reef itself is about 30 m long and 17 m wide at its widest point and 8 m high with vertical faces and overhangs at its northern end. The sides slope by stages to the sand at the southern end and contain many deep fissures with a large one at the northern end widening to a cave that passes through from east to west. The reef is aligned with its longitudinal axis running north-south and provides a diverse environment for a rich fauna and flora, a considerable background knowledge of which has been gained by the survey: by late August 1978 a total of over 30 dives, each of approximately one hour's duration, had been made in this area.

There have been several reports in recent years of the mass occurrence or blooms of the dinoflagellate Gyrodinium aureolum Hulburt in northern European Waters (Ballantine & Smith, 1973; Helm et al. 1974; Pingree et al. 1975; Pingree, Holligan & Head, 1977; Tangen, 1977). Gyrodinium aureolum is probably one of the most common ‘red-tide’ dinoflagellate species in these waters and some of the blooms of G. aureolum (ranging from 100 to 20000 cells ml-1) have been followed by the mass mortality of various fish and invertebrate species (Tangen, 1977). It has been suggested that the adverse effects of G. aureolum on marine organisms are caused by (a) the production of toxins and/or (b) the oxygen depletion during darkness due to dinoflagellate respiration and decomposition of cells.

Dinoflagellate blooms occurred repeatedly along the coasts of France in 1978, and the question was raised, both in newspapers and in the report of the Inquiry Committee of the French Senate on the ‘Amoco-Cadiz’ disaster, of a possible relationship between these occurrences and the oil spilled from the tanker. This hypothesis does not, however, appear to be supported by the data regarding bloom occurrences. These are listed in Table 2, compiled from various sources. Those which concern Brittany and nearby areas, as well as the extent of coast fouled by the ‘Amoco-Cadiz’ oil, are shown in Fig. 2. It is clear from this map that some of the ‘red tide’ occurrences were quite remote from the site of the wreck at Portsall; those outside the area shown in Fig. 2 (e.g. Seine Estuary) were, of course, even more so.