An account has been given (Harris, 1972b) of the distribution of interstitial harpacticoid copepods on an intertidal transect at Whitsand Bay, E. Cornwall. The present work describes seasonal changes observed in the copepod species populations over a period of 2 years, from May 1968 to May 1970. Changes in population density and vertical distribution are described, and the relationship between these changes and the physical environment are discussed. A full account of the reproductive activity and lifecycles of the copepod species will be given later (Harris, 1972d). The only detailed accounts of seasonal cycles of individual intertidal harpacticoids are those of Lasker, Wells & Mclntyre (1970) for the sand-dwelling benthic copepod Asellopsis intermedia (T. Scott) and of Barnett (1968, 1970) for two species of Platychelipus Brady on an intertidal mudflat.

The interstitial meiofauna was investigated on an exposed sand beach at Whitsand Bay, Cornwall. An intertidal transect of eight stations was sampled regularly over a period of 2 years from May 1968 to May 1970. Quantitative core samples were taken to a depth of 50 cm. Nematodes were the dominant group on the beach, forming about 50% of the meiofauna. Harpacticoid copepods were second in overall abundance. Hydrozoa, turbellaria, gastrotrichs and tardigrades were also present.

On the SOND Cruise of R.R.S. 'Discovery' in 1965 a day and a night series of horizontal hauls were made with a modified Indian Ocean Standard Net (N113 H) fitted with a catch dividing bucket (C.D.B.). The hauls were of 1 h duration, made at approximately 50 m depth intervals from 960 to 40 m, at a position off Fuerteventura in the Canary Islands. This paper is one of a series by various authors on the vertical distributions of the animal groups sampled (Angel, 1969; Clarke, 1969 a; Baker, 1970; Badcock, 1970; Foxton, 1970a, b). Details of the cruise and of the hydrology of the area are given by Currie, Boden & Kampa (1969), and Foxton (1969) gave details of the sampling methods.

Twelve strains of psychrophilic, marine pseudomonads which grew readily on nitrate or a mixture ofamino acids, were tested for their content of the enzymes glutamine 2-oxoglutarate amino transferase (GOGAT) and glutamic dehydrogenase (GDH). All strains contained GOGAT activity when grown on nitrate and GDH when grown on amino acids. In all strains tested the synthesis of GOGAT was repressed by growth on amino acids and derepressed by growth on nitrate.

This paper is the second of four dealing with the calanoid copepods taken with a modified Indian Ocean Standard Net (N113H) on the R.R.S. 'Discovery' SOND cruise of 1965. Details of the cruise are given by Currie, Boden & Kampa (1969), and the sampling methods used in the N113H series are described by Foxton (1969) and by Angel (1969).

Information on the reproduction of interstitial harpacticoid copepods is mainly restricted to occasional references in the taxonomic literature to the presence of ovigerous females in collections. C. G. Rao (1967) provides the only account of the life-history of an exclusively interstitial species. The only detailed field study of seasonal reproductive cycles of harpacticoid copepods are of two species of Platychelipus Brady on a mudflat (Barnett, 1970), and of a sand-dwelling benthic copepod, Asellopsis intermedia (T. Scott) (Lasker, Wells & Mclntyre, 1970).

Seasonal changes in cold-tolerance of Balanusbalanoides are correlated with the seasonal changes in free glycerol level in the body parts of adult barnacles and with the degree of unsaturation (iodine number) of the body lipids. Glycerol levels and iodine values were highest in the winter when the barnacles were most cold-tolerant and lowest in the summer when they were least tolerant. There was no correlation between the seasonal changes in cold-tolerance and seasonal changes in free amino acid level or triglyceride: total lipid ratio.

Under laboratory conditions barnacles kept without food at 5 °C over the summer to winter period became cold-tolerant and had high, winter levels of glycerol and high iodine values. Winter barnacles kept at shore temperatures and fed Anemia nauplii until mid-summer lost their cold-tolerance and had low, summer levels of glycerol and low iodine values. In contrast, winter barnacles kept for the same period without food at 5 °C remained cold-tolerant and had high glycerol levels and high iodine values.

The maximum level of free glycerol in the winter corresponded to a concentration in the body tissues of 1 ·06 mM. This is 1000—fold lower than the concentration of glycerol in the pupal haemolymph of glycerol-forming insects and is far below the level necessary to promote general supercooling of the body water. Itis suggested that the mechanism of cold-tolerance in B. balanoides is one oftolerance to freezing, or frost resistance, rather than avoiding ice formation.

Triglycerides and phospholipids are the main lipid components in B. balanoides.

Planktomya henseni Simroth 1896 is a pelagic bivalve widely distributed throughout the warm-temperate and tropical North and South Atlantic Ocean. It is also known from a single collection in the tropical Pacific Ocean. The geographical distribution of Planktomya is probably circumtropical.

This paper is the third of four dealing with the calanoid copepods taken with a modified Indian Ocean Standard Net (N113H) on the R.R.S. 'Discovery' SOND cruise of 1965. Details of the cruise are given by Currie, Boden & Kampa (1969) and the sampling methods used in the N113 H series are described by Foxton (1969) and by Angel (1969).

An investigation into the natural regime of coastal suspended solids before discharge of potash mining waste is described. Regular samples of suspended material were taken over the period September 1968 to August 1970. Statistical analyses showed significant differences in suspended solid values between the months and between inshore and offshore sampling stations. There was no significant difference between sampling points along the coast. The inshore suspended solid values were low from May to September. At other months and at the offshore stations there was a gradual change from summer (low) to winter (high) values and vice versa.

Sea temperature, sea state, tidal range and river flow correlated significantly with suspended solid values. It is suggested that wave action, tidal currents and river flow control most of the variation in load of suspended matter off the N. Yorkshire coast. The significant negative correlation between temperature and suspended solid values is not regarded as a causal relationship. Low temperatures are associated with high wave activity and high river flow rates; factors which are more likely to have a causal relationship with suspended solid loads than temperature. Thus, suspended matter variations off the Yorkshire coast are probably determined by physical rather than biological temperature-dependent processes.

From multiple linear regression analyses, sea state, tidal range and river flow were found to account for 64·1% of the variation of the inshore suspended solid values and 52·4% of the variation of offshore values. Using the multiple regression equations as mathematical models it was possible to derive accurate predictions of the natural suspended solid load.

The rate of water filtration by bivalves has long excited interest, but it has in practice proved difficult to measure in conditions where the animal is relatively free from constraint. Its estimation is important from a number of aspects: feeding studies; as an indicator of the animal's reaction to its environment; and for predicting the flow of water required for the culture of economically important species. The work reported in this paper started as part of the general programme on shellfish culture in progress at this laboratory. During the development of a suitable method for studying the water requirements it became clear that one factor, water current, had a more important influence than has been generally recognized.

The component fatty-acid patterns of the triglycerides, phospholipids and, in some instances, sterol esters of a number of aquatic molluscs have been determined. The species examined include several of marine origin (Chlamys opercularis, Crepidula fornicata, Mytilus edulis, Neptunea antiqua, Patella vulgata and Pecten maximus) and one of freshwater origin (Anodonta sp.). The marine species contained considerable proportions of highly unsaturated acids of the C and C series (eg. 20:5 and 22:5) which are characteristic of the lipids of most aquatic plants and animals. In general, the relative percentages of 18:1,20:1 and 20:4 (5,8,11,14) were greater in the lipids of the marine gastro-pods than in those of the pelecypods. The differences between the fatty-acid distributions of the Anodonta sp. and marine members of the pelecypoda are analogous to those existing between other freshwater and marine animals. Studies were made of the seasonal variations in the relative proportions and fatty-acid compositions of the triglycerides and phospholipids in P. vulgata. The relative proportions of 20:4 (5,8,11,14) and 20:5 in the triglycerides rose abruptly from minimum values in January to maximum values in March and thereafter declined slowly. These changes were mainly compensated by inverse variations in the proportions of saturated and oleic acids. In contrast to the triglycerides there appears to be no significant seasonal differences in the fatty acid patterns of the phospholipids.

A study has been made of the seasonal variations in the component acids of the lipid fractions of Balanus balanoides. The relative proportions of the polyenoic acids in the triglycerides drop sharply during the winter. They reach a minimum in the early spring and then gradually rise to a maximum in the late autumn. These changes are largely balanced by increases in the saturated acids, principally 16:0 and 18 :o.1 During the winter there is a marked decrease in the triglyceride to phospholipid ratio as the depot fats are mobilised as food reserves. The proportions of the polyethenoid acids in the phospholipids decline slowly during the winter and spring and attain their minimum in June-July. This fall is mainly counterbalanced by increases in the amounts of saturated acids, principally 14:0 and 16:0. It seems likely that the observed decreases in the polyenoic acids are brought about by selective utilization of these compounds as reserves during the winter when food is scarce and depot lipid has been depleted.

A dredge equipped with a gate which may be opened by a diver-monitor when it is passing over bottom selected for study and closed elsewhere is described. A meter wheel which activates an electric switch, connected with a battery and counter in the boat, is in contact with the bottom when the gate is open and raised from the bottom when it is closed. This permits the taking of sampling units of uniform predetermined size. Field trials demonstrated that the dredge efficiently captured all categories of animals large enough to be retained by its meshes.

The difficulty of obtaining unbiased, representative samples of single populations is compounded by the complexities of aggregates of populations, such as biotic communities, and even more by discontinuities in the dispersion of the constituent species and the habitats in which they live. The probability of taking such unbiased, representative samples of marine communities decreases with the depth of water from which they are obtained. Sampling confidence at a level which may be taken for granted in terrestrial habitats is possible only in the littoral and shallow sublittoral. And this is true only if the investigator is able to assure himself that each sampling unit is excised only from the kind of habitat whose biota he wishes to study. He may achieve this specificity in sampling benthos, for example, by using grabs and discarding material brought up from bottom types not under investigation. Another approach is to engage in a comprehensive, preliminary, systematic exploration so that when he samples for parametric estimates he can place his grab exactly where he knows that the desired habitat exists.

In a previous paper (Harris, 1972) the meiofauna of an exposed sand beach at Whitsand Bay, Cornwall, was described in relation to the physical environment. During this study special emphasis was placed on the harpacticoid copepods, of which 13 species were recorded on the beach. In the present paper the horizontal and vertical zonation of the copepod species on the beach is described. An account of seasonal changes in the copepod population will be given in a subsequent paper.

Culture studies on the morphology, development and, in some cases, on the life-histories of green shell-boring algae, have shown that in Britain there are at least six species which could be confused under the name Gomontia polyrhiza Born, et Flah. Of these six species it has been possible to identify only four, namely Eugomontia sacculata and Entocladia perforans and Codiolum stages in the life-histories of Codiolum polyrhizum and Monostroma grevillei. The possibility that there are as yet unidentified life-histories involving more shell-boring Codiolum stages has been suggested.

The biology of the bass in British and Irish waters has not been studied in the same detail as the biology of commercially important species, such as gadoids, flatfishes, mackerel and herring.

The rations removed by adult and stage V Calanus helgolandicus (Claus) feeding on large cells of the diatom Biddulphia sinensis Grev. were measured using an apparatus especially designed to keep the plant cells in suspension and estimated to reach a maximum of 1800 cells/animal/day at a food concentrationof 11,300 cells/1. A continual flow method was used to study feeding at very low algal concentrations and it was found that the animals still captured Biddulphia at a food level of only 270 cells/1.

The animals in the feeding experiments were used at a very low population density (6 copepods/1350 ml.) and the maximum value found for the volume of sea water swept clear – 700 ml./animal/day - was unusually high.

The maximum daily rations consumed by each animal were also high, being equivalent to 47–5 % of the body nitrogen and 46–4 % of the body phosphorus. The number of faecal pellets released by the animals increased with the size of ration captured, but the percentage of the ration lost as faecal pellets was fairly constant. In terms of dietary nitrogen the average value was 65–9% and that for dietary phosphorus 59·6%.

The percentage of the daily ration of nitrogen excreted in soluble form was 266% and that of phosphorus 41–2%, these values being significantly higher than those found using unfed animals. Nearly 90 % of the nitrogen excreted by the animals, whether feeding or unfed, was in the form of ammonia. The amounts of excreted ammonia and total soluble phosphorus increased significantly when the animals fed; but the small quantities of nitrogen released in forms other than ammonia did not change.

In spite of the increasing interest in the ecology of interstitial meiofauna (Fenchel, Jansson & Thun, 1967; Gray & Rieger, 1971;Jansson, 1968; Renaud-Debyser, 1963; Renaud-Debyser & Salvat, 1963; Schmidt, 1968,1969) little is known about the seasonal changes that occur in interstitial populations. A number of seasonal studies have been made of groups within the meiofauna–for example, tardigrades (Pollock, 1970) and nematodes (Skoolmun & Gerlach, 1971). However, Schmidt (1968, 1969) provides the only information for a total meiofauna population based on regular sampling over a complete year's cycle.

The vertical and horizontal distribution on the shore and the distribution between the host shell species, is described for a number of species of green shell-boring algae. A list is given of the records made in Britain for shell-boring Codiolum stages and for Entocladia perforans. An account is given of the sequence in which shell-boring algae attack Spirorbis worm tubes in the Isle of Man.