Donald S. McLusky

The effect of salmon farming on the benthos of a Scottish sea loch

Abstract The effects of waste from a salmon farm on the benthos of a fjordic sea loch on the western coast of Scotland have been studied. Within 3 m of the floating cages the sediment was highly reducing, and dissolved oxygen content of the water overlying the sediment ranged from 35 to 75% saturation. At ⩾ 15 m from the cages the sediment was oxygenated, and the dissolved oxygen content of the water overlying the sediment was 50–85% saturation. Sedimentary redox potential and dissolved oxygen content of bottom water showed a seasonal variation. The benthic fauna showed marked changes in species number, species diversity, faunal abundance, and biomass in the region of the fish farm, with four zones of effect identified. Directly beneath, and up to the edge of the cages, there was an azoic zone. A highly enriched zone, dominated by Capitella capitata (Fabricius) and Scolelepis fuliginosa (Claparede), occurred from the edge of the cages out to as 8 m. A slightly enriched ″transitional ″ zone occurred at ⩽ 25 m, and a “clean” zone at distances > 25 m. This study showed that salmon farming had similar effects on the benthos as other forms of organic enrichment, but the effects were limited to a small area in the immediate vicinity of the cages

Some Effects of Salinity on the Survival, Moulting, and Growth of Corophium Volutator [Amphipoda]

An experimental study of the effects of salinity on the mud-dwelling amphipod, Corophium volutator (Pallas), indicates that, if supplied with mud, it will survive the salinity range of 2.50 % 0 , and without mud the range 7.5-47–5 % 0 . Moulting occurred in salinities of 2.6–46 % 0 , but most frequently in the range 5–20 % 0 . Growth occurred at a maximum rate in 15.4 % 0 , and only slightly slower at 4.4 and 30.6 % 0 ; but below 4.4 % 0 the growth rate was progressively reduced. Freezing point studies show C, volutator to be a hyperosmotic regulator, having a tissue tolerance range of 13–50 % 0 . The importance of a supply of mud, and the significance of hyperosmotic regulation are briefly discussed. INTRODUCTION The amphipod Corophium volutator (Pallas) is an inhabitant of littoral muds, the populations often reaching high densities. It has been most commonly reported from shores of estuaries, although Zenkevitch (1963) has stated that it may also occur in muds submerged to a depth of 10 m. Segerstrale (1959) has summarized the data available on the occurrence and distribution of C. volutator . Since that date, work has been done on substrate selection (Meadows 1964a–c), on burrowing behaviour (Meadows & Reid, 1966) and on rhythmical swimming activity under tidal control (Morgan, 1965). Many authors (Nicol, 1935; Thamdrup, 1935; Beanland, 1940; Spooner & Moore, 1940; Rees, 1940; Goodhart, 1941; Stopford, 1951; Rullier, 1959; Gee, 1961) have described the substrate in which C. volutator occurs. They have agreed that C. volutator is found in mud or muddy sand, containing approximately 37 % silt or clay.

Variations in the intertidal and subtidal macrofauna and sediments along a salinity gradient in the upper forth estuary

The intertidal and subtidal soft-sediment macrofauna of the upper Forth estuary, eastern Scotland, UK has been examined. The intertidal fauna was sampled in 1977, and again in 1988/89, at up to twelve stations along the salinity gradient. The subtidal fauna was sampled in 1982 and in 1988/89 at up to 15 stations. The stations span the region of the freshwater-seawater interface, and area of the turbidity maximum. Large spatial and temporal variations in macrofaunal abundance and species composition were observed. Sites at the head of the estuary with low salinity were dominated by oligochaetes, but more saline areas were characterised by a depauparate estuarine fauna. The area has historically received large quantities of organic waste both from sewage and industrial discharges which supported very high abundances of oligochaetes of up to 500,000 m−2 in the upper reaches of the estuary. Reductions in the organic inflow to the area since the early-1980s have begun to cause reductions in oligochaete populations and also allowed the further penetration intertidally of non-oligochaete species into the upper and middle reaches of the estuary. No comparable upstream penetration by the non-oligochaete subtidal fauna has been observed, possibly on account of the greater sediment instability in the estuarys main channel.

Marine and estuarine gradients — An overview

The Proceedings of the ECSA 21 symposium on Marine and Estuarine Gradients are reviewed. It is emphasised that this is probably the first time that a full set of papers on the tidal freshwater sections of estuaries has appeared. There is however some ambiguity in the terminology applied to such waters, and a more consistent terminology is proposed. In particular the estuary is defined as reaching upstream as far as the tidal limit, irrespective of salinity.A wide variety of gradients within estuaries and coastal waters are considered, but it is apparent that the crucial spatial gradients are based on salinity, oxygen and turbidity, and that many other gradients are co-variables with these parameters. Temperature is also important for temporal gradients.

Some effects of salinity on the distribution and abundance of Corophium volutator in the Ythan estuary

A study of the effects of salinity on the distribution and abundance of the amphipod Corophium volutator (Pallas) on the estuary of the River Ythan, Aberdeenshire, indicates that 2‰ is a critical minimum salinity controlling its distribution. In areas with salinities between 2 and 5‰ C. volutator was present, but in reduced numbers. Breeding occurred only in salinities greater than 7·5‰. In areas with salinity greater than 5‰, the distribution and abundance of C. volutator were controlled by the nature of the substrate; however, in areas with suitable substrates, but where the salinity was below 5‰, the effects of salinity override the effects of the substrate. The annual life-cycle is discussed. The results of this study are compared with those of a recent experimental study.

The effect of temperature on the oxygen consumption and filtration rate of Chlamys (Aequipecten) opercularis (L.) (Bivalvia)

Abstract The oxygen consumption and filtration rate of the queen scallop, Chlamys (Aequipecten) opercularis has been studied simultaneously in animals of a wide size range, maintained at four different temperatures (5, 10, 15, 20°C) for known periods of acclimation of up to 7 weeks. The oxygen consumption was found to be markedly affected by temperature and the time of acclimation. The filtration rate was found to be affected by temperature, and the time of acclimation (at 5°C only), but to a lesser extent than oxygen consumption. Consequently the ratio of 1. filtered/ml O2 consumed was found to vary with temperature and perhaps acclimation time, and it is suggested that the relationship between oxygen consumption and filtration rate is not a fixed relationship.

The toxicity of chromium, nickel and zinc: effects of salinity and temperature, and the osmoregulatory consequences in the mysid Praunus flexuosus

Abstract The effect of salinity (4.5–27ℵ) and temperature (5 and 15°C) on the acute toxicity of chromium, nickel and zinc to the mysid crustacean Praunus flexuosus (Muller) has been investigated, at time intervals up to 300 h. Increased metal concentration led to reduced median survival time. Increased temperature, and salinities above or below the isosmotic point, led to reduced median survival times at a given metal concentration and reduced median lethal concentrations of metals. The effect of salinity on metal toxicity has been clearly linked to disruption of the normal pattern of hyper/hypoosmoregulation. The death of animals in chromium or zinc solutions may be related to a progressive decrease in the ability of the animals to osmoregulate, with the rate of osmotic decline related to the median survival time, or the loss of osmoregulatory ability may be a secondary effect of metal poisoning and dying. Nickel was found to be less toxic than either chromium or zinc and to have less effect on osmoregulation.

Effect of salinity acclimation on osmoregulation in Crangon crangon and Praunus flexuosus

Abstract The effect of acclimation to low or high salinity on the osmoregulatory abilities of Crangon crangon L. (Crustacea, Natantia) from two habitats (Aberdour, Scotland and Oresund, Denmark) and Praunus flexuosus (Muller) (Crustacea, Mysidacea) from Oresund, Denmark has been investigated. The effect of salinity acclimation on the salinity tolerance of Crangon was also examined. Animals acclimated for a long time to low salinity in the laboratory, or from low salinity habitats, were found to have enhanced hyperosmotic regulation when exposed to low salinities. Animals acclimated for a long time to high salinity in the laboratory, or from a high salinity habitat, were found to have enhanced hypo-osmotic regulation when exposed to high salinities. Acclimation to low salinity also extended the survival time in low salinities, and high salinity acclimation extended the survival time in high salinities. It is shown that the difference in the osmoregulatory abilities of populations from different habitats ar...

The fresh waters of Scotland: a national resource of international significance.

DEFINING, CLASSIFYING AND EVALUATING THE RESOURCE: History of Freshwater Science Running Waters Standing Water USING THE RESOURCE: Water Supply Tourism and Recreation PRESSURES ON THE RESOURCES: Eutrophication Acidification, River Flow Regulation INTEGRATING CONSERVATION AND DEVELOPMENT: Pollution Control Planning Nature Conservation.

The oxygen consumption of Corophium volutator in relation to salinity

Abstract 1. 1. The oxygen consumption of Corophium volutator, a mud-dwelling euryhaline amphipod, has been measured using microvolumetric respirometers. 2. 2. Comparison was made of animals of the same size, at the same level of activity, at 10°C, acclimitized to salinities 1, 10, 20 and 30%. 3. 3. No significant differences were found in oxygen consumption, between animals in different salinities. 4. 4. In all salinities a logarithmic relationship was noted between oxygen consumption and dry weight. 5. 5. These findings, in conjunction with previous findings, are discussed in relation to the energy requirements of osmoregulation, with particular regard to the conservation of energy by the production of hypo-osmotic urine, the suggested uptake of ions from food, and the possibility of a shift in the energy requirements of different metabolic processes under osmotic stress, perhaps from growth into osmoregulation.