INTRODUCTION

One of the longstanding problems in marine biology has been to determine the quantitative importance of bacteria in the regeneration of the inorganic nutrients. There probably still is no entirely satisfactory way of studying this. It is currently believed that although a variety of marine organisms may utilize soluble organic compounds, bacteria dominate this activity. Thus, a measurement of the amount of soluble organic material oxidized will give a first approximation of bacterial activity. Such an estimate may have to be revised at a later date to allow for the activity of other micro-organisms.

The four species studied (Bledius spectabilis, Heterocerus fenestratus, Dichirotrichus pubescens and Cillenus lateralis) are most commonly found in a region delimited by the anaerobic mud of the lower bank and the dense marsh bordering the drainage channels in tidal salt-marshes at Scolt Head Island, Norfolk.

Experimental submersion of the beetles in sea water was found to induce an apparent anoxic condition which was associated with a drastic reduction in oxygen consumption. On return to air there was a large increase in oxygen consumption characteristic of an appreciable oxygen debt.

The use of the physiological responses to submergence as an indicator of effective contact with water revealed that their subterranean mode of life largely prevents direct exposure of the beetles to sea water in natural conditions. A significant proportion of Heterocerus fenestratus were, however, found to be vulnerable to flooding by sea water during tidal coverage of the burrow system.

These results are considered in relation to the observations made on the behaviour and burrowing activity of the various species.

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.

The distribution of the visual pigments within the retina of the rudd, Scardinius erythrophthalmus, and dragonet, Callionymus lyra L., was studied by measuring the spectral absorbance of small areas of intact isolated retinas.

The rudd retina contains two visual pigments, VP 5O71 and VP5352. There is a progressive change in the relative proportion of these two pigments in the dorso-ventral plane, and there are no sharply defined zones each with a different pigment mixture. The proportion of the A1-based pigment (VP 5071) is greater in the dorsal part of the retina.

The maximal optical density of the pigment in the dorsal retina of the rudd was greater (about o·6) than it was in the ventral retina (about 0·3). The difference in the amount of light absorbed, however, is small compared to the intensity difference between the up-welling and downwelling light of the environment. When the relative proportion of the A1- and A2-based pigments was changed by altering the lighting conditions under which the animals were kept there was little or no change in the maximal optical density of the pigment.

In the dragonet the retina shows a clear division into a ventral pink zone (maximal optical density about 0·5) and a dorsal zone that is much paler (maximal optical density about 0·2). The relative spectral absorbance of the two regions is similar, although one is said to be a pure cone region, and the other to be dominated by rods.

The spectral absorbance curves for the intact retinas agreed well with results obtained with pigment extracts.

Observations made with the 2 m ring-trawl off Plymouth during the years 1967,1968, 1969 and 1970 indicate that the increased abundance of young fish, excluding clupeids, reported for the year 1966 has been maintained.

For the collections made in 1969 the species of clupeids, Arnoglossus, sand-eels and Callionymus have been separately identified.

The year 1969 was characterized by the high numbers of post-larvae of Phrynorhontbus norvegicus. For the first time on record a post-larva of Sargus sargus was caught. Unusual abundance of post-larvae of the bass, Dicentrarchus labrax, was recorded for May 1970.

The distribution of the larvae of four of the five species of Ammodytidae occurring in Scottish waters is examined. The two most abundant species, Ammodytes marinus Raitt and Gymnammodytes semisquamatus (Jourdain) are described in detail and their abundance recorded. A. marinus larvae were found throughout the survey area, but were most abundant in the Moray Firth and around Orkney. G. semisquamatus larvae were most abundant along the north and west coasts, although they were recorded in a few areas off the east coast of Scotland. A. lanceolatus Lesauvage larvae occurred generally in Scottish waters, although few larvae were caught. A. immaculatus Corbin larvae, which have not previously been recorded in the Scottish area, were also rare and were restricted to areas off the north and west coasts. The material was not suitable for demonstrating the distribution of larvae of A. lancea Raitt. The occurrence of larvae is related to the spawning season of each species.

The amino acid composition has been investigated in two euphausiids, Euphausia superba Dana and Meganyctiphanes norvegica (M. Sars), and one mysid, Neomysis integer Leach. Protein-bound amino acids show a very considerable degree of similarity: glutamic acid, aspartic acid, lysine, leucine and arginine are predominant in all three crustaceans, and occur in that order of importance. Together they amount to ~ 50% of the total protein hydrolysates. Concentrations of free amino acids show greater differences between the zooplankton species, but taurine, glycine and arginine are very important in all three. Lysine and ornithine occur in fair quantities in both euphausiids, and proline and alanine are moderately important in Euphausia superba and Neomysis integer.

INTRODUCTION

Much of the rocky coast of Norway is known to form a favourable habitat for Laminaria hyperborea (Gunn.) Foslie. In June and July 1965 observations of this species and its competitors were made both in an area near Espegrend (60° 16.23′ N, 5° 13.42′ E), 15 km south of Bergen, and near Tromso (69° 39.2′ N, 18° 57.6′ E) for comparison with populations round the Isle of Man.

The population dynamics of the mysid crustacean Praunus flexuosus have been studied at Ardmaddy Bay, Loch Etive. A salinity tolerance range of 2–33‰ has been demonstrated, over which the body tissues experience the range 11–28‰. Comparison is made between the osmoregulatory capacity of Praunus flexuosus and the closely related Neomysis integer.

Observations on the fine structure of two clones of zoids derived from Phaeocystis pouchetii s.l. are presented, with special reference to the scales, pyrenoids and haptonema, in which both clones agree. An unexplained difference between them in the form of a threadlike deposit external to the scales in one clone only is described in a preliminary way. The most remarkable feature encountered is the presence of some unexplained bulbous inclusions distorting the tip of the haptonema but perhaps also present in a less extreme form in other types recently examined alive. The interpretation of these findings is discussed.

INTRODUCTION

It has been known for a long time that the soft tissues of molluscs contain relatively high concentrations of certain trace elements—mainly transition metals (see, for example, Vinogradov, 1953; Bowen, 1966). However, with the exception of the work by Brooks & Rumsby (1965) on the occurrence of 12 elements in 3 New Zealand bivalves, most of the investigations have concerned the distribution of only one or two elements. This has prevented a study being made of possible interelement correlations. The present work was carried out in an endeavour to determine the usual levels of several minor elements in a variety of molluscs from the Irish Sea and to seek evidence for such correlations.

The ctenostomatous ectoproct Triticella koreni (G.O. Sars) occurs mainly on Calocaris macandreae (Bell) and Nephrops norvegicus (L.) but also on other Crustacea including Upogebia deltaura (Leach), Goneplax rhomboides (L.), etc. (Eggleston, 1969). Off Northumberland T. koreni occurs mainly on C. macandreae. C. macandreae moults from September to December (Buchanan, 1963).

In order to investigate how the ectoproct copes with this annual substrate loss collections of C. macandreae made in all months were examined. Some of the material was provided by Dr J. B. Buchanan; all came from mud bottoms 40 fathoms deep east of Blyth and was collected between 1961 and 1963. Ten random C. macandreae were taken from each month's collection. One periopod on each Calocaris was selected by the use of random numbers. The number of T. koreni zooids, the number of developing zooids, the number of oviparous zooids and the number of free eggs in each oviparous zooid on each selected limb were counted.

The data recorded from the ten limbs from each collection examined are shown in Table 1.

T. koreni zooids are hermaphrodite. The gonads and free spermatozoa and eggs can be seen through the translucent body wall. Spermatozoa and eggs rarely occur in quantity in the same zooid. Some zooids are so packed with sperm as to appear opaque; up to thirty-one eggs were seen in other zooids. The egg is small and unpigmented; the larva is unknown.

From November to June T. koreni colonies grow rapidly and have a high proportion of developing zooids. From July to October growth slows and reproductive activity increases.

A saline pond known as the ‘Salts Hole’ at Holkham on the north coast of Norfolk is situated between the pine-covered sand-hills and the fields that have been reclaimed for agriculture from pre-existing salt-marshes. It has a salinity of about 75% of that of sea water and supports a peculiar relict marine fauna. Except for the rare occurrence of flooding for a short period, as in the great storm of 1953, the pond has probably been cut off from the sea for about 250 years. It presents three problems: how it got its fauna and flora; how its marine character is maintained; and how the pond originated geographically. The fauna and flora, as described, show the pond as a refuge where various marine and brackish species have managed to maintain themselves and co-exist in water outside their normal and differing ranges of salinity. The main character of the pond is kept remarkably constant with respect to salinity, alkalinity, temperature and oxygenation. The pond is a study in ‘natural engineering’, constituting a natural marine aquarium with natural controls. It is fed near the level of high-water neap tide by continuous flow from a salt spring of very constant salinity supplied from water contained in the extensive coastal sands. Its only apparent artificial feature is the outlet controlled by a dam through a culvert into a ditch that conveys its water through the fields to the sea at Wells nearly two miles away. Search in the muniment room at Holkham Hall brought to light maps dating back to Elizabethan days which show the history of the Salts Hole.

INTRODUCTION

A long-term ecological study is being carried out in the Ythan Estuary in north-eastern Scotland. An understanding of the hydrology of the estuary is a prerequisite for future studies into energy relationships in lower trophic levels of the food web. Much of current research into the estuarine environment is concerned with large coastal-plain systems where physical and chemical characteristics are so different from those of shallow estuaries, such as the Ythan, that comparisons of environmental data are untenable. The present investigation reports information collected between October 1966 and September 1968 on major environmental factors and their effect on the distribution of nutrients and detritus in the ecosystem. Results of a concomitant study of algal productivity in a mudflat of the estuary are reported in Leach (1970).

INTRODUCTION

The caesium radionuclides, caesium-137 and caesium-134, are important constituents of aqueous radioactive effluents discharged to the environment of the United Kingdom from fuel re-processing plants and nuclear power stations (Howells, 1966; Mitchell, Harvey & Smith, 1968; Harvey, Baker & Mitchell, 1969). Their accumulation by marine fishes has been the subject of several previous studies, beginning with that of Chipman (1959) who noted that caesium-137 was accumulated in the flesh of the killifish (Fundulus heteroclitus) and that accumulation continued even after a period of 72 days. Similarly, Hiyama & Shimizu (1964) showed that the muscle of the common goby (Acanthobus flaviamus) continued to accumulate caesium-134 from sea water after periods of 30 days. Baptist & Price (1962) have examined the whole body uptake of caesium, by absorption from sea water, in two marine species, the flounder (Paralichthys dentatus) and the Atlantic croaker (Micropogon undulatus), and they also investigated the accumulation, tissue distribution and excretion of caesium-137 in the croaker, the little tuna (Euthynnus alleteratus) and the bluefish (Pomatomus saltatoux), following oral administration of single doses. These authors concluded that the heart, liver and spleen of the croaker absorbed caesium-137 from sea water at a faster rate than the muscle, and that orally administered caesium-137 was rapidly absorbed from the digestive tract. Tissue distributions were similar in the croaker, bluefish and tuna. The retention of caesium-137 in croaker tissue was described as a multiple rate process. In later experiments Hiyama & Shimizu (1969) compared turnover rates in various organs and tissues following uptake from sea water and from single injection experiments, and obtained good agreement between the values from the two methods.

Assimilation efficiency (percentage of nutrients absorbed) from diets compounded from dry food meals was investigated using the prawns Palaemon serratus Pennant and Pandalus platyceros Brandt. An indirect ratio method using chromic oxide (Cr2O3) as an inert reference material in the diet was employed, but the method was complicated by the prawns' habit of regurgitating part of the indigestible food remains after a meal. Thus quantitative collection of both faeces and the regurgitated, unassimilated food fraction was necessary.

INTRODUCTION

Studies on the physical hydrography of the Irish Sea, based mainly on temperature and salinity observations, have been made by Bowden (1955) and Lee (1960). The current systems in various parts of the Irish Sea have been investigated by Bowden & Sharaf El Din (1966), Harvey (1968), Ramster & Hill (1969) and Hill & Ramster (1971). Various smaller-scale physical observations made by other workers have been listed by the above authors.

There are not as many references in the literature to the distribution of nutrient salts in the Irish Sea. Jones & Haq (1963) measured phosphate in Liverpool Bay as part of an investigation into the distribution of the alga Phaeocystis. Slinn & Offlow (1968) have made regular routine measurements of phosphate, nitrate and silicate over a number of years off Port Erin, Isle of Man. Ewins & Spencer (1967) measured phosphate, organic phosphorus, nitrate and silicate in the Menai Straits, and Liss (1969) surveyed the distribution of silicate in the western Irish Sea.

During recent years the Fisheries Laboratory at Lowestoft has investigated the distribution and ecology of plankton and larval plaice in the Irish Sea, and a supporting programme of both physical and chemical hydrographic observations has been made in the area. Ramster & Hill (1969) and Hill & Ramster (1971) have summarized the results of the Lowestoft current measurements. The present paper describes an investigation into the distribution of temperature, salinity, phosphate, nitrate and silicate. The occurrence of Phaeocystis is also reported as an extension of the earlier work by Jones & Haq (1963).

INTRODUCTION

Ecological studies of Eider Somateria mollisima, Shelduck Tadorna tadorna, Redshank Tringa totanus [Aves], and Flounder Platichythys flesus [Osteichthys], in the estuary of the River Ythan, Aberdeenshire, have entailed investigations of their food requirements, and there is evidence to suggest that Hydrobia ulvae [Gastopoda], as a numerous food item common to all, may in some instances have influenced their breeding success and numbers in some years. In order to get an index of abundance of Hydrobia, the Ythan population has been sampled four times a year since May 1963. The full results of this sampling programme are being published separately. At the same time data on the annual cycle of Hydrobia were collected from one area (transect number 3, Fig. 1), on the assumption that breeding onset and intensity would be the same in other parts of the estuary in any one year.

The accumulation of radionuclides by I-group plaice, Pleuronectes platessa L., in the vicinity of the pipe-line of the UKAEA plant at Windscale, Irish Sea, has been studied over a 7–month period. The principal isotope found in the flesh was 137Cs, although 144Ce, 106Ru, and 95Zr/95Nb were also present in the gut contents. The 137Cs flesh levels were examined in conjunction with the fluctuations of this nuclide in sea water, sediment and the gut contents. Of the three major dietary components found throughout the sampling period the calculated intake of 137Cs from food appeared to fluctuate most closely with the Nephtys fraction of the diet, despite its relatively low 137Cs content.