The effects of nutrient additions and zooplankton excretion products upon carbon fixation rates in the phytoplankton present at Station L 4 in the English Channel during the summer and autumn of 1979 have been studied. Nitrate, ammonium, urea, phosphate, glucose-6-phosphate and the excretion products when added individually all caused photosynthesis to be stimulated, and the result of the simultaneous addition of nitrate and phosphate indicated that their effects were additive. Germanic acid, which inhibits photosynthesis mainly in diatoms, removed the stimulatory effect of the nitrogen supplements, indicating that they were utilized mostly by the diatoms; the higher fixation rates caused by the phosphate enrichments were, however, decreased by the same proportion as the unenriched controls when germanic acid was present, suggesting that the whole of the phytoplankton population was phosphorus-limited. This was supported by the finding that glucose-6-phosphate stimulated carbon fixation in all of the phytoplankton.

The excretion products, even at concentrations likely to be produced in the sea, stimulated carbon fixation, and it has been calculated that zooplankton-regenerated nitrogen and phosphorus compounds could supply the amounts needed to maintain primary production during the summer period.

Nutrient additions and zooplankton excretion products had little effect upon carbon fixation in the autumn samples, presumably because the higher nutrient levels then present in the water exceeded the requirements of the phytoplankton.

It has been concluded that the predominance of the sub-10 μ microflagellates in the summertime is probably due to their ability to utilize more efficiently than the other types of phytoplankton the low levels of nutrients which become available due to regeneration.

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.

In a search for phytoplanktonic algae which may condition water masses by excreted metabolites monocultures of 29 species of diatoms and flagellates, also of one sedentary alga, were tested with developing eggs and larvae of two species of sea-urchin and of a polychaete. Results indicated that about half of the algal species examined, using both unfiltered cultures and filtrates from them, probably do not produce metabolites affecting development of the three animal species employed in this work. Others were harmful or favourable to them in various ways. One flagellate species in particular, Olisthodiscus luteus N. Carter was of outstanding interest, with effects on larvae varying from toxic to favourable according to culture density and amount of dilution with normal sea water. Ancillary experiments eliminated the possibility that excessively high or low pH could be responsible for observed effects, while others showed that in a semi-toxic environment crowding of eggs and larvae can be beneficial but not in non-toxic media. In the main experimental search for possible effects of metabolites, eggs and larvae were never crowded.

A numerical model is used to derive both the S2 and M3 tides for the shelf seas around the British Isles. The M2 tide was run with the S2 tide in the presence of quadratic friction. It was found that quadratic friction marginally overdamps the S2 tide. A further approximate representation of the S2 tide was obtained from a model in which the quadratic friction term was replaced by a linear frictional coefficient in a tensor form based upon the M2 tidal currents derived from the spring-neap simulation. These simulations form the basis for interpreting the M2/S2 ratios and phase differences that occur on the north-west European shelf.

A numerical model is used to derive the N2 tide around the British Isles. The model can derive any semidiurnal astronomical constituent in about 5 tidal cycles to > 90% accuracy. This simulation demonstrates the importance of quadratic friction and frequency in determining the relative positions of the N2, M2 and S2 amphidromes.

An energy budget has been assembled for a population of the limpet Patella vulgata inhabiting the mid-tide level of a moderately sheltered shore in the Isle of Man. The average biomass during the two year study was 346 kJ m−2, and the energy budget in kJ m−2 year−1:

Juveniles of Patella spp. in Britain are shown to be easier to classify than adults, on shell morphology alone, because of a species-specific difference in number and arrangement of the post-larval mantle tentacles. The limpets can thus be clearly divided into three distinct spp.: P. vulgata Linn., 1758, P. aspera Roding, 1798, and P. depressa Pennant, 1777, which confirms recent evidence from gel-electrophoreric studies. As the limpet grows, this initial difference gives rise to many of the variables of shell shape and colour upon which adult identification is based. In the process, it can be influenced by environmental factors to the extent of producing confusing phenotypes such as those hitherto supposed to be hybrid or genetically transitional forms. The characters described suggest that, contrary to current opinion, P. aspera and P. depressa are related more closely to each other than to P. vulgata; they may also have some bearing on the species' success and distribution in the British Isles.

When exposed to water of low salinity specimens of Mytilus edulis L. keep their shell valves tightly closed; they do not gape periodically to test the external medium. Exchange of salts and water between the mantle cavity and the environment is thus minimized. Rising salinities are registered by diffusion of salts to the tentaculate portion of the inhalent siphon and not to any other portion of the mantle edge or to any more deeply located structures.

From observations in the aquarium and by a morphological study of the feeding tentacles it is concluded that Leptopentacta elongata is not, as is commonly supposed, a mucus suspension feeder, but feeds on deposited material by mechanical entrapment with the aid of sticky papillae on the tentacle buds.

Previous work has indicated that, although in possession of numerous supposedly osmoregulatory structures, Branchiostoma lanceolatum from the English Channel is unable to regulate its body weight in diluted sea water. In vitro measurements of the rate of flagella activity in those organs similarly indicates no increase under hypo-osmotic stress. There is however quite a sharp threshold around 18‰, below which flagella activity ceases quite abruptly. A similar situation obtains with the gill cilia although the animal can remain alive at these salinities for a period of several weeks.

The life-cycle of the harpacticoid copepod Tisbe furcata (Baird, 1837) at 18 C was studied quantitatively. Stage durations were determined by two different methods, using synchronous cohorts. Combined nauplius stages last for 80·4 h; the successive copepodite stages take 23·0, 23·2, 28·0 (♀) to 23·2 (♂), 33·4 (♀) to 24·2 (♂) and 48·8 (♀) to 34·7 (♂) h, respectively. Females develop more slowly but more synchronously than males. Age-specific survival and fertility rates were used to calculate the stable stage distribution in an exponentially growing population. From life-table data the following demographic parameters were computed: intrinsic rate of natural increase rm = 0·233 day−1; net reproductive rate Ro = 94; minimum generation time Tmin = 14·9 days; parameters related to ‘generation time’: T = 19·5 days, = 16·4 days, Tc = 25·4 days.

Analyses of the ampharetid polychaete Melinna palmata have shown that this species consistently contains a high concentration of copper. The related species Melinna cristata also has a high copper content but Ampharete acutifrons and Amphicteis gunneri have low copper contents. M. palmata usually contains copper in concentrations in excess of 600 μg/g (dry weight) and often above 1100 μg/g; much of this copper is embodied in the branchiae which have concentrations of 0·4–1·2% copper and, although these organs account for only 3–4% of the dry body weight, their copper content represents 30–40% of the total body burden. X-ray microanalysis shows the copper in the branchiae to be concentrated in special epidermal cells. The function of the copper in these cells does not appear to be associated with detoxication, luminescence or an antifouling mechanism but feeding trials have shown the branchiae of Melinna palmata, but not of Ampharete acutifrons, to be distasteful to certain small fish. Thus it is thought the copper may reduce the palatability of the tissues and is accumulated by Melinna palmata as a chemical defence against predation.

The hepatic photophores of species of Sergestes (organs of Pesta) contain fluorescent paracrystalline platelets which are the sources of the luminescence. The cells containing these crystals are contiguous with cells filled with lipid droplets which act as a diffuse reflector. The optical properties of the organ as a whole derive from the different arrangement of the various regions in the mosaic of individual tubules. The hepatic photophores of Parapandalus, Thalassocaris and Chlorotocoides have a similar anatomical position but differ considerably in structure. They do not contain paracrystalline material and they have a diffuse reflector, probably not composed of lipid, which is separated from the tubules that make up the photocytes. The organs in Thalassocaris and Chlorotocoides are very similar in structure. Luminescence in the photophores of all four genera is probably intracellular.

An apparatus has been developed which allows the complete replacement of interstitial water in sediments without disturbance. In principle, it can be adapted to handle sand or mud, different solutions, and different volumes of sediment. The apparatus was tested with 0·05% (wt/vol.) eosin in sea water. After replacement of the interstitial water, the eosin was evenly distributed throughout the sediment. Interstitial water in samples of sediment was replaced by sulphide solutions in sea water, at a range of concentrations. The responses of Corophium volutator to these sediments was tested in choice and non-choice experiments. In the choice experiments, animals avoided burrowing in sediments containing sulphide at concentrations greater than about 5·8 × 10−5M. In the non-choice experiments, animals were progressively inhibited from burrowing when the sediment sulphide concentration was greater than about 5·8 × 10−4M. No mortality occurred during the experiments.

Coxal plates 1–5 of Epimeria cornigera form a closely interlocking series keyed by the head such that ventral flexion of the peraeon is severely curtailed. The clamp formed by coxae 4 and 5 is interpreted as an adaptation facilitating copulation in a species with feeble gnathopods and non-prehensile antennae. The morphology of the posterior three pairs of peraeopods can also be regarded as an adaptation for gripping the female. Other possible functions (e.g. predator deterrence and feeding grip) of coxal structures are also examined.

Three species of Photis Krayer are recorded from British and Irish waters. P. pollex Walker is re-established as a distinct species, synonymous with P. macrocoxa Shoemaker which becomes a junior synonym. A key to the British and Irish species is given, together with figures and descriptions of P. pollex and P. reinhardi. P. tenuicornis which is doubtfully recorded from these waters is also figured.

Parathemisto gaudichaudi was collected off the south coast of Northumberland during 1970–2, and the moulting and growth of laboratory-maintained individuals observed. The moulting behaviour is similar to that described for other amphipods, but individuals remain attached to medusae during moulting. The minimum body size at maturity, the time from hatching to maturity and the length of the intermoult period are shown to be temperature dependent. The analysis of growth-factor data resolves growth into a rapid juvenile phase and a slower adult phase. The development of secondary sex characters is related to developmental stages of the gonads.

Macrobenthic infauna was sampled in Mevagissey Bay, off the south coast of Cornwall, England, when the bay was receiving fine-grained mineral waste from the china clay industry at a rate of about 450000 tons per annum. Quintuplicate 0·1 m2 grab samples, washed on a 0·5 mm mesh, were taken on 15 occasions over two years at a station about 1 km from the outfall and at a water depth of 13 m. The fauna had a range of density of 755–2144 individuals/0–5 m2 and in composition resembled a partially impoverished Echinocardium cordatum/Amphiurafiliformis community. Population densities of Goniada maculata (Polychaeta), Cingula semicostata (Gastropoda), Nucula turgida, Mysella bidentata, Venus striatula and Tellina fabula (Bivalvia) showed no clear trends during the two years' sampling. Magelona filiformis (Polychaeta), Abra alba and Phaxas pellucidus (Bivalvia), Acrocnida brachiata and Amphiura filiformis (Ophiuroidea) declined in abundance, whereas the densities of Nephtys hombergi (Polychaeta) and Labidoplax digitata (Holothurioidea) increased. L. digitata became the commonest species, with a peak density of 708 individuals/0·5 m2. A month after sampling began the rate of waste discharged was reduced from 700000 tons per annum, but this did not appear to improve conditions for the benthic community. Total faunal density remained relatively stable but species diversity declined. It is argued that the suspended solid concentration was unlikely to have adversely affected the predominantly deposit-feeding community, but that persistent sediment instability continued to be a source of stress. Nevertheless, the observed major changes of community structure were similar to natural fluctuations of coastal soft-bottom populations resulting from species interactions and differences of larval success.

Details of the gross cellular changes taking place in the gonadial tissues and coelom of Ficopomatus during the annual reproductive cycle are presented. There is no true gonad in either sex; instead, germ cell precursors are produced by divisions of a germinal epithelium associated with the ring blood vessels in the intersegmental septa.

Segments producing gametes do not all develop simultaneously; the posterior segments are generally at a more advanced stage of sexual maturity. The later stages in gamete development take place free in the coelom, where nourishment is supplied presumably by the mobilization of materials formerly stored in tissues surrounding the gut.

Spawning commences in June and continues through to October, with peak activity coinciding with the period of high water temperature in August and early September. The adult population comprises males, females, and protandrous hermaphrodites which in the male phase become sexually mature in advance of the rest of the population, and as females later on. These transitional individuals are thought to contribute a negligible amount to the effective reproductive output in those populations living where there is marked temporal constraint on the period of reproduction.

The different reproductive capacities of temperate and tropical Ficopomatus are considered.

In conjunction with a tagging experiment on Callista chione (L.) in 1976, a small number of the large bivalve Arctica islandica (L.) (Family Arcticidae) were also tagged in a similar manner with plastic discs cemented on to the shell with fast-setting cyanoacrylate adhesive. Arctica is less common in Whitsand Bay than Callista but extends into deeper water, 50–60m. Holme (1953) suggested that the species is long-lived and produced spat infrequently. A few young Arctica have been taken in Whitsand Bay (length 29–37 mm) and also, more commonly, specimens of 80–100 mm. In 1976 five Arctica were tagged and relaid, three of these were recovered in 1977 and one in 1978. Three more were tagged in 1978 and searched for without success in 1979. The recovered specimens did not appear to have moved at all. The results of shell length measurements, though meagre, indicated that growth was very slow. For a shell of 82 mm length the increase was 1–5 mm in a year. For a shell of 101 mm there was no increment after two years. For a shell of 102 mm the annual increment was probably 0-1 mm. In this instance it seems likely that the original length should have been 102–3 mm instead of 103–2 which was recorded. For a shell of 108 mm an increment of 0–3 mm was found after 12 months. From these results the average increment of shells over 100 mm length is likely to be of the order of 0-1 mm per year.