Samples of phytoplankton from nets towed in the surface waters off Plymouth over a period of 24 years were subjected to a correspondence analysis. There was a high species diversity throughout the year, and a strong seasonal cycle. A total of 104 species was divided into eight groups showing different seasonal and year-to-year occurrence. Over the 24 years the seasonal pattern of species changed in a fairly systematic way and there were two periods (1968–70 and 1983–85) when the changes were most marked. These patterns could be related to changes in the weather patterns, and were similar to those found by other workers in other groups of organisms and in other areas.

Details are given of the culture apparatus and methods found successful for the laboratory culture of species of Ectocarpus. In attempts to obtain uni-algal cultures of this genus several common methods were tried but only one of them, a modification of the plating technique, proved successful. Methods of washing and dilution were unsuccessful in giving bacteria-free cultures, presumably due to bacteria closely adhering to the cell walls. Ultraviolet irradiation was also unsuccessful but treatment with penicillin gave bacteria-free cultures of E. confervoides and E. secundus (Giffordia secunda).

This study of the genus Pterosperma followed on from our work on the genus Halosphaera (Parke & Adams, 1961; Parke & Hartog-Adams, 1965; Boalch & Mommaerts, 1969) since while studying the latter we found abundant pterospermatacean material. In recent books on algae the family Pterospermataceae Ostenfeld (1902) is placed in the class Chrysophyceae (Papenfuss, 1955; Bourrelly, 1957, 1968; Fott, 1959, 1971; Prescott, 1969). The family, however, rightfully belongs in the class Prasinophyceae (Parke in Parke & Dixon, 1964, 1968; Christensen, 1966) in the order Pterospermatales (Parke & Green in Parke & Dixon, 1976).

The growth and nutrition of Ectocarpus confervoides has been studied in bacteria-free cultures. Growth was estimated by dry weights determined under controlled conditions. A method for inoculation of cultures of filamentous algae is described and a table of culture media is given. Following a lag of 5–7 days there was a period of growth, which was not truly exponential, extending over a period of 35 days. Calculation of the relative growth constant for the early stages of growth indicated that the alga doubled its dry weight every 6–7 days. Cultures of Ectocarpus remained viable for over 1 year in the light and for over 100 days in the dark. In natural sea-water media the maximum growth was brought about by the addition of 0·5 mM potassium nitrate and 0·1 mM potassium phosphate. Ferric chloride had no effect on growth but additions of manganese chloride did cause some stimulation. Additions of some complex organic mixtures slightly increased growth but Ectocarpus was unable to grow on a range of organic carbon source in the dark. The optimum salinity at 20° C was somewhat higher than that of natural sea water but was apparently lower at 15° C. The optimum pH was 8·0. Light intensities between 1350 and 16,000 lux had no marked effects on the growth rate but did effect the lag, the optimum for this being 7000 lux. Temperature also had no effect on the growth rate but did effect the lag. The optimum was 15–20° C but there was growth between 10 and 25° C. A considerable range of artificial sea waters, with and without organic additions was investigated, in no case did they give a yield greater than two-thirds that in natural seawater media. These results are discussed in relation to other workers findings.

The new species Halosphaera parkeae (Prasinophyceae) is described from material collected in the western English Channel. The microscopical structure of the outer wall of the non-motile phase is described and two types of punctation are demonstrated. A general account of the cytology of the mature non-motile phase and of the motile cell is given. Electron micrographs of the scales of the motile cell are compared with those of other species of the genus where known. Buoyancy, size and reproduction are discussed and a number of new taxonomic characters emphasized. The occurence in the same areas of a second type very similar but smaller in size is recorded and the authors have named this form Halosphaera parkeae forma minuta.

Phytoplankton data collected between 1964 and 1974 at three stations in the western English Channel were analysed by the multivariate method of correspondence analysis. The data comprised counts, logarithmically transformed, of 126 taxonomic groups in 700 samples from different depths. The first three axes from the correspondence analysis explained only 17% of the total variation, but the sample positions on these axes showed a clear mean seasonal cycle, slightly different at each station. The species fell into ten groups according to their position on the axes and to their seasonal occurrence. Differences in the position on the axes of samples from different depths on the same occasion correlated well with the temperature structure of the water column. No clear long-term trends were apparent although there were obviously large differences from year to year. The results provide a mean seasonal pattern of species succession on a quantitative basis which can be used to compare counts from different areas or to identify changes in the same area.

Measurements of the ultra-violet absorption spectra between 200 and 400 mix, have been made with a spectrophotometer. At short wave-lengths natural sea water has double the absorbancy of artificial sea water. The difference in samples from shallow depths is ascribed to organic material, of which part may be the Gelbstoff of Kalle. Regional variations have been found, coastal waters having higher U.V. absorptions. A small seasonal effect with an increase in absorbancy in summer in the English Channel has been seen. In deep Atlantic water increased absorption below 235 m/x may be due to its high nitrate concentration. At longer wave-lengths absorbancies were less than in surface waters. Measurements of U.V. absorption may supplement other physical methods of characterizing water masses.

On 11 August 1976 an observant yachtsman noted an unfamiliar alga between Misery Point and Warren Point at the mouth of the River Yealm. Suspecting that it might be ‘Japweed’ he collected a piece and took it to Mr B. W. P. Sparrow of the International Marine Coatings Laboratory who contacted the Marine Biological Association, where Dr Boalch confirmed that it was a part of a fertile plant of Sargassum muticum, the first to be recorded from the Plymouth area (see Fig. 1).

The intertidal zonation of the dominant algal species in Beer Bay, south-east Devon, was examined in relation to substratum by means of plane-table maps and transects. The dominance of Ulva lactuca on colonies of the reef-building worms Sabellaria alveolata was noted, but the distributions of Fucus vesiculosus, F. serratus, Gigartina stellata and Enteromorpha spp. showed no correlation with substratum.

The original descriptions of species of the genus Ptychodiscus are discussed. Recent material is examined both alive and preserved. It is concluded that the only valid species is Ptychodiscus noctiluca Stein. Ptychodiscus carinatus Kofoid, P. inflatus Pavillard and Diplocystis antarctica Cleve are all synonymous with this species.

In 1930, Colman (1933) made a study of the zonation of common intertidal animals and plants on Blackstone or Church Reef, Wembury. Four lines were marked out across the reef, and three of these, which radiated from his so-called ‘Central Rock’, were resurveyed during the summer and autumn of 1973. Besides the authors, help was given in the 1973 survey by Mr P. G. Corbin, Dr P. E. Gibbs, Dr P. K. Probert, Dr A. J. Southward, Mr R. L. Barrett and Mr T. J. Perry. Mr G. A. W. Battin was responsible for surveying and levelling, and Mr D. Nicholson for the photography.

In 1959 and 1960 eight surveys were made in an area about 54 x 83 km in the English Channel immediately south of Plymouth (Armstrong & Butler, 1962b). Measurements of temperature and salinity and of phosphate and silicate concentrations showed a good deal of variation from place to place so that it would be difficult to accept results from any one station as typical of the area. The density distributions suggested a general eastward movement in the winter and, in summer, a movement of surface water offshore from the English coast, with a corresponding onshore movement of deeper water.

The original descriptions of these two species are discussed and the material mentioned in Smith's description is examined. Discrepancies between Smith's description of Coscinodiscus concinnus and the present interpretation of this species are pointed out. Ways of typifying the two species so as to preserve current usage and still fulfil the requirement of the International Code of Botanical Nomenclature are given. Lectotypes for the two species are designated. Diagnostic characters distinguishing the two species in the living state as well as the cleaned valves are given.

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).

Scientific data from the last 100 years are combined with primary and secondary historical information on the fisheries to summarize changes in the relative abundance of pilchards and herrings in the south-west in the last 400 years. The fluctuations in the two species are compared with recorded and inferred annual mean temperatures over the period. Pilchards are more abundant and extend farther to the east when the climate is warmer, as from 1590 to 1640 and from 1930 to 1960. In cooler times, as in the second half of the seventeenth century, herrings are more abundant while the pilchard fishery occurs later in the year and is restricted to west Cornwall. Lesser changes in the relative abundance of the two species and the timing of the fishery along the south coast of Devon and Cornwall in the intervening periods between these extremes accord fairly well with smaller fluctuations in climate. It is presumed that in addition to direct effects on reproduction and behaviour, changes in climate can indirectly influence the relative competitive advantage of the species through alterations in the associated ecosystem.

Over a period of 10 years, 1964–74, primary production has been measured at three stations across the western English Channel using the 14C method. Results for carbon fixation, cell counts and mean seasonal production are illustrated. Statistical analyses show that, at two of the three stations, carbon fixation in 1966 was significantly greater than expected and that annual production differs significantly at each of the stations. The variations observed are discussed in relation to other changes recorded in the area during the same period. A deck incubator used for simulated in situ14C experiments is illustrated.

Three surveys were made in 1963 and five in 1964 in the area of the English Channel between the English and French coasts and between 3° 40' W and 5°10' W. This area had been surveyed in 1961 and 1962. Temperature and salinity were determined at o, to and 50 m and phosphate silicate and nitrate at 10 and 50 m. The results are presented graphically. Temperature and salinity were compared with Lumby's 25–year averages. The year 1963 started with unusually low temperatures and salinities higher than average. Temperature remained low in the spring, but salinity decreased. The year 1964 started with temperatures and salinities above normal, but during the rest of the year values were close to average. Nitrate in January 1964 was higher than in January 1963. Analyses of suspended matter at 12m were made for carbon, nitrogen and phosphorus on most surveys, and mean values for the whole area are given. Suspended carbon was 67 /ig C/l. in January 1963 and 51 /*g C/l. in January 1964, a significant difference. Increases in sus-pended carbon, nitrogen and phosphorus were found in spring and summer 1964.