Showing papers by "Scottish Association for Marine Science published in 2002"
TL;DR: Kongsfjorden is a glacial fjord in the Arctic (Svalbard) that is influenced by both Atlantic and Arctic water masses and harbours a mixture of boreal and Arctic flora and fauna as discussed by the authors.
Abstract: Kongsfjorden is a glacial fjord in the Arctic (Svalbard) that is influenced by both Atlantic and Arctic water masses and harbours a mixture of boreal and Arctic flora and fauna. Inputs from large tidal glaciers create steep environmental gradients in sedimentation and salinity along the length of this fjord. The glacial inputs cause reduced biomass and diversity in the benthic community in the inner fjord. Zooplankton suffers direct mortality from the glacial outflow and primary production is reduced because of limited light levels in the turbid, mixed inner waters. The magnitude of the glacial effects diminishes towards the outer fjord. Kongsfjorden is an important feeding ground for marine mammals and seabirds. Even though the fjord contains some boreal fauna, the prey consumed by upper trophic levels is mainly Arctic organisms. Marine mammals constitute the largest top-predator biomass, but seabirds have the largest energy intake and also export nutrients and energy out of the marine environment. Kongsfjorden has received a lot of research attention in the recent past. The current interest in the fjord is primarily based on the fact that Kongsfjorden is particularly suitable as a site for exploring the impacts of possible climate changes, with Atlantic water influx and melting of tidal glaciers both being linked to climate variability. The pelagic ecosystem is likely to be most sensitive to the Atlantic versus Arctic influence, whereas the benthic ecosystem is more affected by long-term changes in hydrography as well as changes in glacial runoff and sedimentation. Kongsfjorden will be an important Arctic monitoring site over the coming decades and a review of the current knowledge, and a gap analysis, are therefore warranted. Important knowledge gaps include a lack of quantitative data on production, abundance of key prey species, and the role of advection on the biological communities in the fjord.
574 citations
TL;DR: In this paper, it was shown that although estuaries are sinks for contaminants from the terrestrial environment, there is significant transport of marine material up-estuary as bed load sediment whilst fine-grained terrestrial material may be transported seawards in suspension.
Abstract: Estuaries are sites of port, industrial, urban and recreational development and also important to many forms of animal life. They often form sinks for sediment and thus for contaminants associated with the sediment which arise from anthropogenic activities in their hinterland and along their shores. These contaminants can adversely affect estuarine ecosystems and are the subject of international agreements on environmental protection. For both of these reasons, it is important to increase our knowledge of the distribution, concentration, controlling influences on, and impacts of, estuarine contamination. Evidence from around the world shows that although estuaries are sinks for contaminants from the terrestrial environment, there is significant transport of marine material up-estuary as bed load sediment whilst fine-grained terrestrial material may be transported seawards in suspension. Major movement of contaminants from estuaries onto the continental shelf probably occurs only during floods and storms and, in general, the impact on shelf seas is relatively minor and confined to the coastal zone. The chief exception to this rule is in the Far East where sediment from major Chinese rivers may be dispersed up to 300 km across the shelf.
287 citations
TL;DR: It is concluded that bacterial growth/growth inhibition can be easily and reproducibly measured from microplate cultivations with a flatbed scanner or with a microplate spectrophotometer.
195 citations
TL;DR: In this article, a UV fluorescent particle tracer was deployed to the seabed (water depth ≈30 m) and sediment samples taken on days 0, 3, 10, 17 and 30 to measure the horizontal and vertical distribution of tracer in sediments.
Abstract: To validate a resuspension model of particulate material (salmonid farm wastes), a UV fluorescent particle tracer was selected with similar settling characteristics. Tracer was introduced to the seabed (water depth ≈30 m) and sediment samples taken on days 0, 3, 10, 17 and 30 to measure the horizontal and vertical distribution of tracer in sediments. A concentric sampling grid was established at radii of 25, 50, 100, 150, 200, 400, 700 and 1, 000 m from the source on transects 30° apart. The bulk of the deployed tracer was initially concentrated in an area 25 m radius from the release point; tracer was observed to steadily decrease to zero over a period of 30 days. In a 200 m region measured from the release point in the direction of the residual current, the redeposition of tracer was low. A Lagrangian particle tracking model was validated using these observed data by varying resuspension model parameters within limits to obtain the best agreement between spatial and temporal distributions. The validated model generally gave good predictions of total mass budgets (±7% of total tracer released), particulary where tracer concentrations were high near the release point. Best fit model parameters (critical erosion shear stress=0.018 N m−2, erodibility constan=60 g m−2 d−1) are at the low end of reported parameters for coastal resuspension models. Such a low critical erosion shear stress indicates that the frequency of resuspension and deposition events for freshly deposited material is high.
119 citations
TL;DR: The use of shallow water by plaice represents the occupation of a niche which not only reduces predation and maximises growth, but may also greatly reduce competition for food in the earliest stages when densities are highest and competition with dabs is likely to be greatest.
Abstract: Stratified depth sampling was used to investigate the distributional changes of newly settled plaice Pleuronectes platessa and dabs Limanda limanda, and resident populations of shrimp Crangon crangon on a sandy beach. During the settlement period, the smallest newly settled plaice are found in deeper water than the larger fish that settled earlier. After settlement, plaice concentrate in water < 1 m deep and there is a positive relationship between length and depth. Later in the year the fish gradually migrate into deeper water as they grow. Dabs settle later and in deeper water than plaice. Shrimp are concentrated in deeper water early in the year but migrate onshore in the summer. The movements of plaice are considered to be related to the predation risk caused by the shrimp and other predators in deeper water and to the higher temperatures in shallow water that promote faster growth. Once a size refuge from predators has been reached, the plaice move into deeper water. Intertidal pools probably serve as refuges for the smallest sizes of plaice because predators are less numerous in pools than in the sea. The use of shallow water by plaice represents the occupation of a niche which not only reduces predation and maximises growth, but may also greatly reduce competition for food in the earliest stages when densities are highest and competition with dabs is likely to be greatest.
119 citations
TL;DR: In this paper, the authors assess the origin, transformation and mass fluxes of material through the Pomeranian Bight based on an integrated field study conducted in the period 1996-1998.
80 citations
TL;DR: In this paper, a transect from shallow (16 m) to deep (47 m) water of the SW Baltic Sea is studied in which wave and current-induced energy input to the seabed in shallow water is high with strong variability and suspended matter concentrations may double within a few hours.
77 citations
TL;DR: In this paper, shipboard experiments were conducted in the northern North Sea to assess the rate of removal of dimethylsulphide (DMS) and the production of DMSO due to both UVB and UVA/visible light.
Abstract: Shipboard experiments were conducted in the northern North Sea to assess the rate of removal of dimethylsulphide (DMS) and the rate of production of DMSO due to both UVB and UVA/visible light. Experiments were conducted using 0.2-μm filtered seawater and natural light conditions. The DMS photolysis rate constant was determined to be between 0.03 and 0.07 h−1, and initial photolysis rates were between 1.3 and 2.5 nmol dm−3 d−1. Using these rates, the in situ profiles for downward irradiance, and the DMS concentration in the water column, a photochemical turnover rate constant of between 0.1 and 0.37 d−1 was determined for the upper 20 m of the water column, with a photochemical turnover time of between 2.5 and 9.5 days. DMSO photoproduction rates were up to 1.20 nmol dm−3 d−1. Furthermore, results indicate that under UVA/visible light most of the DMS is photo-oxidised to form DMSO, whereas under UVB radiation DMS may be removed via a second photolysis pathway.
66 citations
TL;DR: Oxygen alters whole–school parameters at oxygen saturation values that can be encountered by herring in the field, indicating that oxygen availability is an important factor in the trade–offs that determine school volume.
Abstract: The effect of progressive hypoxia on the structure and dynamics of herring (Clupea harengus) schools in laboratory conditions was investigated. The length, width and depth of schools of about 20 individuals were measured from video recordings to test the hypothesis that during hypoxia fish schools change their shape and volume. School shape (calculated as the ratios of length/depth, width/depth and length/width) did not change significantly during hypoxia. School length, width, depth, area and volume were all significantly increased at 20% oxygen saturation. Volume, area and width were more sensitive to hypoxia; volume and width were also increased at 25% and area at 30% oxygen saturation. The degree of position changing (shuffling) of individuals within the school was also analysed. Shuffling in normoxia was observed to occur largely through ‘O-turn’ manoeuvres, a 360° turn executed laterally to the school that allowed fishes in the front to move to the back. O-turn frequency during normoxia was 0.69 O-turns fish 1 min 1 but significantly decreased with hypoxia to 0.37 O-turns fish 1 min 1 at 30% oxygen saturation. Shuffling was also investigated by measuring the persistence time of individual herring in leading positions (i.e. the first half of the school). No significant changes occurred during hypoxia, indicating that the decrease in O-turn frequency does not affect shuffling rate during hypoxia, and that position shuffling in hypoxic conditions is mainly due to overtaking or falling back by individual fishes. School integrity and positional dynamics are the outcome of trade-offs among a number of biotic factors, such as food, predator defence, mating behaviour and various physical factors that may impose certain limits. Among these, our results indicate that oxygen level modulates schooling behaviour. Oxygen alters whole-school parameters at oxygen saturation values that can be encountered by herring in the field, indicating that oxygen availability is an important factor in the trade-offs that determine school volume. An increase in school volume in the wild may increase the oxygen available to each individual. However, shuffling rate is not affected by hypoxia, indicating that the internal dynamics of positioning is the result of the balance of other factors, for example related to the nutritional state of each individual fish as suggested by previous studies.
61 citations
TL;DR: The unique toxin profile of Singapore strains indicates that it is unlikely that this strain has been recently translocated from any of the populations with characterized toxin profiles, and may be a useful signature to identify the potential spread of this strain from the port of Singapore.
Abstract: We investigated the cell morphology, toxicity and toxin composition, and rDNA sequences of clonal cultures of the chain-forming dinoflagellate Gymnodinium catenatum H.W.Graham isolated from the port of Singapore. The cell morphology was consistent with most descriptions of this species except for sparsely distributed putative trichocyst pores visible on some cells under SEM. Nucleotide sequences (697 base pair) of the D1–D2 conserved regions and intervening variable domain of the large subunit rDNA were identical among isolates from Singapore and those of all other global populations examined so far (from Australia, China, Japan, Korea, New Zealand, Spain, and Uruguay), and this is consistent with the morphological conservatism of the species. Among isolates of G. catenatum that produce toxins associated with paralytic shellfish poisoning, the cellular toxicity of Singapore clones, as determined by intraperitoneal mouse bioassay (30–50 pg saxitoxin equivalents·cell−1) and immunoassay (24 ± 8 saxitoxin equivalents·cell−1) was relatively high. The mouse bioassay toxicity was comparable with that of Spanish and Philippine isolates that have undergone acid hydrolysis. However, analysis of toxin composition of Singapore clones by HPLC with fluorescence detection or HPLC-mass spectrometry/mass spectrometry revealed a unique toxin profile that was dominated by the highly potent carbamate toxins, primarily gonyautoxin (GTX) 1 and 4 with lesser amounts of GTX2, GTX3, neosaxitoxin, and saxitoxin. No N - sulfocarbamoyl, decarbamoyl, or deoxy-decarbamoyl toxins were detected. In contrast, less potent N - sulfocarbamoyl toxins dominate the toxin profiles of all other global populations examined to date (from Australia, China, Japan, New Zealand, the Philippines, Portugal, Spain, and Uruguay). The lack of genetic diversity found among broadly distributed populations of G. catenatum is consistent with the hypothesis of a relatively recent global spread of this species. Yet the unique toxin profile of Singapore strains indicates that it is unlikely that this strain has been recently translocated from any of the populations with characterized toxin profiles. In any case, the unique carbamate-dominated toxin profile may be a useful signature to identify the potential spread of this strain from the port of Singapore, one of the world's busiest.
57 citations
TL;DR: In this paper, deep-water renewal events, both observed and predicted from empirical models, in the bottomwaters of Loch Etive provide an opportunity to assess the temperature, salinity and?18O relationship.
Abstract: The sea lochs (fjords) of north-west Scotland are located in a region of Europe particularly well situated to monitor changes in westerly air streams. The moisture transported in these air streams has a profound effect on regional precipitation, freshwater run-off and, in turn, sea loch circulation. The gentle slope of the regional salinity:?18O mixing-line, defined as 0.18 ‰ per salinity unit, suggests that the temperature: ?18O relationship may be readily resolved in these coastal waters. Deep-water renewal events, both observed and predicted from empirical models, in the bottom-waters of Loch Etive provide an opportunity to assess the temperature, salinity and ?18O relationship. Predicted changes in ?18Ocalcite as a function of changing salinity (?S) and changing temperature (?T) during deep-water renewal events suggest that >80% fall above analytical detection limits. The theoretical likelihood of recording such renewal events in the “palaeoclimate” record appears to be promising, but temperature and salinity change during renewal events may have either sign. Scottish fjords, because of the relatively small impact which salinity has on ?18Owater, may provide useful study sites in palaeoclimate research, particularly where palaeotemperature is the primary record of interest.
TL;DR: A high-resolution seismic and gravity coring survey has been conducted on inner and part of outer Loch Etive, a 30 km long, 150 m deep sea loch on the west coast of Scotland as discussed by the authors.
TL;DR: Krill appears to be capable of adapting to both changing thermal and trophic conditions, especially when nutrition is a limiting factor in physiological processes.
Abstract: Adaptive processes linked to overall metabolism were studied in terms of oxygen consumption and ammonia excretion in each of three self-contained krill populations along a climatic gradient. In the Danish Kattegat, krill were exposed to temperatures which ranged from 4°C to 16°C between seasons and a vertical temperature gradient of up to 10°C during summer. In the Scottish Clyde Sea, water temperatures varied less between seasons and the vertical temperature gradient in summer was only 3°C. Temperatures in the Ligurian Sea, off Nice, were relatively constant around 12–13°C throughout the year, with a thin surface layer (20–30 m) of warm water developing during summer. The trophic conditions were rich in the Kattegat and, particularly, in the Clyde, but comparatively poor in the Ligurian Sea. Oxygen consumption increased exponentially with increasing experimental temperature, which ranged from 4°C to 16°C. Overall respiration rates were between 19.9 and 89.9 µmol O2 g–1 dry wt h–1. Krill from the Kattegat, the Clyde Sea, and the Ligurian Sea all exhibited approximately the same level of oxygen consumption (30–35 µmol O2 g–1 dry wt h–1) when incubated at the ambient temperatures found in their respective environments (9°C, 5°C, and 12°C). This indicates that krill adjust their overall metabolic rates to the prevailing thermal conditions. The exception to this were the respiration rates of Ligurian krill from winter/spring, which were about twice as high as the rates from summer krill despite the fact that the thermal conditions were the same. This effect appears to result from enhanced somatic activity during a short period of increased food availability and reproduction. Accordingly, krill appears to be capable of adapting to both changing thermal and trophic conditions, especially when nutrition is a limiting factor in physiological processes.
TL;DR: Comparison between the macrostructures of illicia and Sagittae indicated that a translucent zone is formed in the illicia of most 0-group by autumn but not in sagittae, suggesting that earlier estimates of small size at age may have arisen from incorrect interpretation of the time of first translucent zone formation in illicia.
Abstract: Microincrements in the lapilli otoliths of Lophius piscatorius L. were used to validate the age of fish <27 cm TL collected in spring and autumn. Contrary to published estimates of size at age based on illicia by Dupouy et al. (1986) and Duarte et al. (1997), these small specimens were found to be either 0- or 1-group. Comparison between the macrostructures of illicia and sagittae indicated that a translucent zone is formed in the illicia of most 0-group by autumn but not in sagittae. Hence, earlier estimates of small size at age may have arisen from incorrect interpretation of the time of first translucent zone formation in illicia. In addition to enabling age validation, microstructure provided a means of distinguishing between the translucent material that forms false rings and annuli. Annuli appeared as a sequence of gradually declining increment widths whereas false rings were characterized by an abrupt check in otolith formation followed by increments similar in width to adjacent opaque material. The implications of these findings to age reading and interpretation are discussed. 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd.
TL;DR: Correlation analysis showed that variation in annual winter seawater temperature could act as an indicator of interannual variation in abundance of some of the dominant species utilizing rocky subtidal habitats.
Abstract: Fish assemblages on two inshore rocky subtidal sites on the west coast of Scotland, were studied using diver visual surveys on a monthly basis between September 1995 and December 1999. A total of 17 689 fishes and 26 species were recorded from the two sites, Saulmore Point (056°27' N; 005°24' W) near Oban and Davy's Rock (055°46' N; 004°53' W) on the Isle of Great Cumbrae. The gobiid Thorogobius eppiphiatus, dominated the Saulmore Point site; six fish species accounted for >93% of total abundance at that site. At Davy's Rock four species contributed at least 93% of total fish abundance, and the dominant species was the labrid Ctenolabrus rupestris. Total abundance of the dominant species displayed a clear seasonal trend, and this was significantly related to recorded daily average seawater temperature. A maximum abundance of 4.9 fishes m -2 was recorded in November 1998 at Davy's Rock and 2.5 fishes m -2 at Saulmore Point in October 1998. Multivariate analysis indicated a degree of variation in assemblage structure between winter and summer at both sites. A number of species showed some degree of interannual variation, in particular the gobiid Gobiusculus flavescens whose abundance increased by over 300 times over a 5 month period in 1998. Correlation analysis showed that variation in annual winter seawater temperature could act as an indicator of interannual variation in abundance of some of the dominant species utilizing rocky subtidal habitats.
TL;DR: In this article, the downward flux of sedimenting material represents a sink for particulate dimethylsulphoniopropionate (DMSP) and investigate the fate of this DMSP within the sediment material.
Abstract: Work was conducted to establish if the downward flux of sedimenting material represents a sink for particulate dimethylsulphoniopropionate (DMSP) and to investigate the fate of this DMSP within the sedimenting material. Four sediment traps were successfully deployed for a maximum of 24 h in the northern North Sea between the 5th June and the 1st July 1999. After recovery, samples were taken immediately and analysed for levels of dimethylsulphide (DMS), dimethylsulphoxide (DMSO) and DMSP. Any remaining trap material was incubated in the dark at in situ seawater temperature for a maximum of 120 h. Results from the sediment traps showed that only 1% of the DMSP standing stock was lost daily due to sedimentation. However, results from the incubation experiment demonstrated not only that the downward flux of DMSP is underestimated due to its degradation within the trap material, with between 30% and 47% of the DMSP being lost over 48 h, but also that up to 21% of the DMSP lost may be converted to DMSO. These results clearly demonstrate that DMSO is generated within sedimenting material.
TL;DR: The Loch Linnhe Artificial Reef as discussed by the authors is a large-scale reef complex being constructed on the west coast of Scotland and intended for research purposes, and it was the first artificial reef application to be successful under the new guidelines and therefore has particular relevance to any reef development occurring within Europe and, more generically, worldwide.
Abstract: In the UK, artificial reefs are sometimes perceived by the public as an excuse for dumping of waste materials. This negative perception, combined with the increased role (and statutory requirement) for public consultation in the granting of licences, means that artificial reef projects are greatly assisted by a structured approach to planning and consultation early in the developmental process. At present, a statutory framework governing reef construction within Europe has not been agreed, but new guidelines were issued in 1998 under the auspices of the Oslo Paris Commission. The Loch Linnhe Artificial Reef is a large-scale reef complex being constructed on the west coast of Scotland and intended for research purposes. It was the first artificial reef application to be successful under the new guidelines and therefore has particular relevance to any reef development occurring within Europe and, more generically, worldwide. The licensing process was assisted by open dialogue with a range of user groups and local bodies. Early and constructive consultation within a formal management structure impressed local government and licensing agencies, facilitated informed debate, and greatly enhanced the public's understanding of complex issues related to artificial reef construction. The whole process was considered by many as being beneficial in obtaining the final permission for deployment. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.
TL;DR: In this article, a collection of otoliths was exchanged among the participating laboratories in Portugal, Scotland, and Spain and a workshop was held to discuss the results of the intercalibration exercises.
Abstract: To facilitate intercalibration of the age readings of black scabbardfish, Aphanopus carbo, a collection of otoliths was exchanged among the participating laboratories in Portugal, Scotland, and Spain and a workshop was held to discuss the results. The age precision was significantly improved by the intercalibration exercises but remained relatively low. The indirect validation methods applied showed that the growth increments used for age determination were consistent. However, some discrepancies were found between otoliths from different areas, probably due to the complex spatial distribution of the species and the differing length structure, depending on the area and the method of fishing. Interpretation criteria were defined pending more definitive validation studies.
TL;DR: In this article, the concentrations of dissolved and particulate manganese and iron and of dissolved oxygen in the water column have been measured as a function of depth in the upper basin of Loch Etive, over a 17 month period.
Abstract: The concentrations of dissolved and particulate manganese and iron and of dissolved oxygen in the water column have been measured as a function of depth in the upper basin of Loch Etive, over a 17 month period. For most of this period the bottom water was isolated, which caused low dissolved oxygen concentrations within the water column and concomitant high levels of manganese. The highest concentrations of manganese were close to the bottom. During the study period an overturn event occurred which caused complete mixing of the water column, and flushing of the low oxygen, high manganese deep water.
By using published rate constants for the oxidation of Mn2+ and by assuming steady state, we estimate that the oxidation of dissolved Mn2+ (and by implication the return of solid phase manganese to the sediment) occurred at the rate of 2·2–5·4 mmole m−2 d−1, on an areal basis during the period of isolation. Mn2+ efflux experiments gave values of 0·44 and 0·81 mmole m−2 d−1.
TL;DR: Cutaneous taste buds occurred on the head and fins in five species of juvenile gadoid fishes from the west of Scotland, but there were significant differences in their density between regions on the fish and between species for individual regions.
Abstract: Cutaneous taste buds occurred on the head and fins in five species of juvenile gadoid fishes from the west of Scotland, but there were significant differences in their density between regions on the fish and between species for individual regions. The highest taste bud densities were recorded on the edge of the anterior naris flap, the barbel, pelvic fin rays, snout tip and upper lip. Cod Gadus morhua and poor cod Trisopterus minutus had significantly higher taste bud densities on the first two pelvic fin rays than the other species. This appears to correspond with their more benthic lifestyle, in which the pelvic fins are frequently trailed over the sea bed when searching for prey.
TL;DR: Overall the study has revealed significant differences in the abundance, biomass and quantitative importance of different taxonomic categories of nanoflagellates in offshore waters of differing physico-chemical character north and south of the Polar Front.
TL;DR: A multidisciplinary cruise to the northern North Sea was undertaken during June 1999 to carry out a Lagrangian study of an Emiliania huxleyi bloom as discussed by the authors.
Abstract: A multidisciplinary cruise to the northern North Sea was undertaken during June 1999 to carry out a Lagrangian study of an Emiliania huxleyi bloom. During this experiment, the naturally occurring radionuclide, 234 Th, was measured in the water column to estimate particle fluxes and resulting residence times. Simple steady state modelling of changes in 234 Th activity suggests an increase in scavenging efficiency over an 8 day period. The steady state 234 Th flux ranges from 357 to a maximum of 1390 dpm m −2 d −1 on the 25th June 1999, with a corresponding particulate organic carbon (POC) flux from 9.5–48 mmol C m −2 d −1 , estimated from POC/ 234 Th ratios on filtered particulate material. Scavenging of the 234 Th by the bloom occurs immediately. The maximum POC fluxes follow the peak in primary production and the maximum coccolithophore cell abundance within a few days. The 234 Th and POC fluxes illustrate the rapid response of export with biological activity.
TL;DR: The survivorship and growth rates of juvenile, hatchery rearedPsammechinus miliaris (Gmelin) were observed for seaurchins fed different diets, and maintained at varying stocking densities and locations, although survivorship in all treatments and in both first and secondgenerations was exceptionally high.
Abstract: The survivorship and growth rates of juvenile, hatchery rearedPsammechinus miliaris (Gmelin) were observed for seaurchins fed different diets, and maintained at varying stocking densities andlocations (tank or sea-based). In addition survivorship and growth of secondgeneration hatchery stock was also recorded. Somatic growth rates of juvenileurchins (initial test diameter 6.5 mm SD 1.26) were measured over9months. A high lipid, high protein diet supported higher somatic growth ofurchins in this size range. Higher stocking densities (4 individualsl−1 as opposed to 2 individuals l−1)adversely affected growth as did location (sea-based urchins being smaller thantank based) although survivorship in all treatments and in both first andsecondgenerations was exceptionally high. Further research is required to designdietspromoting somatic rather than gonadal growth in urchins below market size.
TL;DR: In this paper, marine geophysical and sediment core data demonstrate the influence of ambient bottom currents on deposition in this area, and reveal two styles of contourite sedimentation: deposition of glauconite-rich sandy contourites in exposed areas of the Falkland Plateau and Falkland Trough, where vigorous ACC bottom currents control sedimentation, and deposition of biogenic sandy contours, muddy contours and hemipelagites, and muddy diatom ooze, in the form of two elongate sediment drifts, which have developed in the presence of
Abstract: The Falkland Trough is a west-east bathymetric deep that separates the Falkland Plateau from the North Scotia Ridge in the western South Atlantic. It lies in the path of Circumpolar Deep Water flowing within the Antarctic Circumpolar Current (ACC), and Weddell Sea Deep Water flowing beneath the ACC east of Shag Rocks passage. Marine geophysical and sediment core data demonstrate the influence of ambient bottom currents on deposition in this area, and reveal two styles of contourite sedimentation: (1) deposition of glauconite-rich sandy contourites in exposed areas of the Falkland Plateau and Falkland Trough, where vigorous ACC bottom currents control sedimentation, and (2) deposition of biogenic sandy contourites, muddy contourites and hemipelagites (western Falkland Trough), and muddy diatom ooze (eastern Falkland Trough), in the form of two elongate sediment drifts, which have developed in the presence of more sluggish bottom currents. The drift sediments contain a depositional record of bottom current flow through the glacial cycle (southern-origin bottom water flow in the east, and probably ACC flow in the west); analyses of core data from the western Falkland Trough suggest a reduction in bottom current strength during the Last Glacial Maximum at present depths of > 2500 m below sea level.
TL;DR: In this article, a bottom trawl with lights attached to the headline of a trawl during a series of tows at 1000m depth in the Rockall Trough (north-east Atlantic).
Abstract: Lights were attached to the headline of a bottom trawl during a series of tows at 1000 m depth in the Rockall Trough (north-east Atlantic). There was no significant difference in the overall numerical abundance of demersal fish between the trawl catches with light and the controls with no light. A principal components analysis based on the total fish catch between the experimental and the control stations showed no segregation. At the individual species level significant differences in catch rate were found for eight species. These are discussed in relation to the small amount of available information on the visual systems of deep-sea demersal fish and their diet.
TL;DR: In this article, the chemical stability of the proposed concrete and base granite material was tested, under conditions designed to maximize metal flux, and showed significant but very low leaching of iron, strontium, barium, rubidium, manganese, and uranium.
Abstract: The cost of construction materials is a major factor determining the economic viability of artificial reefs. The use of by-products is one method of reducing costs, but often, to comply with licensing conditions, chemical and physical stability have to be demonstrated before such materials may be employed. Granite quarrying produces a range of low-value by-products, including an aqueous granite powder suspension. When mixed with other by-products and consolidated using 5% (w/w) cement and 5% (w/w) coal fly-ash, this substance was used to produce concrete blocks with a compressive strength of approximately 14 N mm −2 after a standard 90-day curing period. The blocks exceeded the strength requirement of commercial building blocks (British Standard 6073) by five times, were cheaper to produce compared with standard construction-grade blocks, and permitted a range of design options to be considered through the inclusion of voids. The chemical stability of the proposed concrete and base granite material was tested, under conditions designed to maximize metal flux, and showed significant but very low leaching of iron, strontium, barium, rubidium, manganese, and uranium. Metal leaching was not necessarily in proportion to the metal concentration in the base material. Quarry by-products can be used in the manufacture of blocks that are physically robust and environmentally safe with a concomitant reduction in production costs. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.
01 Jan 2002
TL;DR: In this article, the authors present a synthesis of the present knowledge of the spatial and temporal variation of slope communities, which is used to provide a scientific basis for the environmental management of the continental slopes of Europe.
Abstract: The ocean margins contain a great variety of habitats and biological communities. Recent discoveries, such as deep-water coral reefs, show that these communities are poorly described and understood. However, observations have already indicated that benthic communities on ocean margins show high levels of spatial and temporal variation at all scales. The European continental margin is increasingly exploited for both biological resources (fisheries) and non-biological resources (oil, gas, minerals). Environmental management of the exploitation of continental margins requires an understanding of natural levels of variation inherent in biological communities that are potentially impacted by such activities. This paper presents a synthesis of the present knowledge of the spatial and temporal variation of slope communities. Priorities for future research and its technological development are discussed. The aim of this research is to provide a scientific basis for the environmental management of the continental slopes of Europe.
TL;DR: In this paper, the authors measured current speed and direction at three marine cage farms in Greece and one in Mediterranean Spain and found that current speeds were around 10% of the wind speed in the residual flow direction.
Abstract: Measurements of current speed and direction were made at three marine cage farms in Greece and one in Mediterranean Spain. At two sites where contemporaneous wind measurements were made, current velocity was correlated with wind velocity. It appears that for each of the sites in Greece, at the time of measurement, the wind was the most important driver of water movements. However, at the Spanish site, current speeds were around 10% of the wind speed in the residual flow direction, indicating that the wind was not the only driver of water movements. Mean current speed ranged from 1.2 to 9.1 cm/s, therefore being within the typical range of mean current speeds experienced at tidal North Atlantic fish culture sites. Mediterranean sites differ from Atlantic sites in terms of temperature and salinity but may possess broadly similar surface flow regimens despite lacking macro-tidal forcing.
01 Jan 2002
TL;DR: In this article, the authors used molecular genetic tools to predict benthic biology with a high enough resolution to provide useful precision for specific areas, such as areas of seafloor fluid seepage or canyons.
Abstract: Deep water environments along the continental margin show mainly depth-related, but also significant along-slope, patterns in the composition, biomass and diversity of the benthic biota. Superimposed on this broad-scale pattern, local-scale habitat variability, including nature of the sediment, hydrodynamics and topography, can also be detected. However, along-slope variability is poorly understood, because only a relatively small number of sites have as yet been investigated and because sampling effort is generally sparse and poorly replicated. We are unable to predict benthic biology with a high enough resolution to provide useful precision for specific areas. Furthermore, the benthic biology associated with highly localised conditions, such as areas of seafloor fluid seepage or canyons, remains largely unknown, while knowledge of patterns in smaller benthic size classes is less well developed than for larger size classes. Progress in knowledge of benthic biodiversity on the continental margin is severely constrained by present taxonomic deficiency, with an increasingly large imbalance between available taxonomic capability and the extraordinarily rich, yet significantly undescribed, biodiversity. There is an urgent need for the application of molecular genetic tools to problems of understanding vertical and horizontal ranges of organisms. Little is presently known, even though studies of morphological variability have been applied to some groups of animals. Understanding of relevant processes operating both at (1) ecological time scales in maintaining high local-scale species richness, and at (2) historical time scales influencing speciation, needs to be developed before meaningful assessments of long-term anthropogenic impacts can be made. Yet, such impacts, particularly those from presently unregulated deep-sea trawling for non-quota fish stocks along the European continental margin may have already changed the ecosystem from its previously pristine state. Deep-sea trawling causes a direct physical impact, which is known already to have damaged slow-growing cold-water corals in some areas. Deep-sea fishing also may have an effect on the background ecosystem, including the benthos, as a result of return to the sea of biomass discarded from the catch. Although care needs to be taken in interpreting the outcome of specific anthropogenic impacts, knowledge of (1) likely sensitivities of species and (2) overall ecosystem resilience, will be informed by studies of responses to natural disturbance.