Red algal exotics on North Sea coasts

A total of ten red seaweed species are recognized as introduced into the North Sea from other parts of the world. These areAsparagopsis armata andBonnemaisonia hamifera (Bonnemaisoniales),Grateloupia doryphora (Halymeniales),Antithamnionella spirographidis, Antithamnionella ternifolia, Anotrichium furcellatum, Dasya baillouviana, ?Dasysiphonia sp.,Polysiphonia harveyi andPolysiphonia senticulosa (Ceramiales). The oldest of these isB. hamifera, introduced prior to 1890, while the most recent,?Dasysiphonia sp., was first found in 1994 and still requires taxonomic investigation. A variety of distribution patterns is seen, with geographical ranges varying from general within the North Sea to very restricted. The diversity of introduced red algae on eastern coasts of the North Sea is much greater than in the west. The most likely explanation for this pattern is that French coasts were the initial site of introduction for many of the seaweeds, which were then distributed northwards by the residual surface currents. Their increasing success in the Netherlands has probably been promoted by the drastically changed local hydrodynamic conditions which have also permitted the recent introduction of many native European species. Of the biological features of species that may favour their success as introductions, clonal vegetative propagation, often with specialized propagules or fragmentation mechanisms, is almost ubiquitous. Low-temperature tolerances can be inferred, but data are sparse. Many of the alien red algae in the North Sea contain anti-grazing compounds such as bromophenols, which may contribute to their invasive potential by deterring grazing sufficiently to permit establishment of an inoculum.     

Incidence of Brucella species in marine mammals of the German North Sea

In this study, organ samples from 426 common seals Phoca vitulina, 298 harbour porpoises Phocoena phocoena, 34 grey seals Halichoerus grypus and 10 other marine mammals were assessed for the presence of Brucella species. Forty-seven common seals, 2 harbour porpoises and 1 grey seal were found to be positive for these bacteria. A total of 91 Brucella strains were successfully isolated, due to the fact that Brucella spp. were found in more than one organ sample in 15 animals. The primary organ in which the bacteria were present was the lung. In addition, 2 strains were isolated from lungworms (Parafilaroides spp.). Forty-nine of the isolated strains were selected for further analysis using conventional phenotyping methods. Molecular characterisation was carried out by analysing the IS711 and omp2 loci. With respect to the distribution of the IS711 loci in the genome, the 49 field isolates differed strongly from the terrestrial Brucella species and marginally from the marine Brucella reference strain NCTC12890. Based on the results of the PCR restriction fragment length polymorphism (PCR-RFLP) investigation of the omp2 locus, the majority of the Brucella field isolates were classified as B. pinnipediae, recently proposed B. pinnipedialis, possessing 1 omp2a gene and 1 omp2b gene. Two field isolates revealed the presence of 2 omp2a genes, as has been described for Brucella ovis. To our knowledge, these results confirm for the first time the presence of Brucella species in the marine mammal population of the German North Sea. These findings highlight the need for additional research on the relevance of these Brucella species for marine hosts and their environment.     

Native Parasites Adopt Introduced Bivalves of the North Sea

Introduced species may have a competitive advantage over native species due to a lack of predators or pathogens. In the North Sea region, it has been assumed that no metazoan parasites are to be found in marine introduced species. In an attempt to test this assumption, we found native parasites in the introduced bivalves Crassostrea gigas and Ensis americanus with a prevalence of 35% and 80%, respectively, dominated by the trematode Renicola roscovita. When comparing these introduced species with native bivalves from the same localities, Mytilus edulis and Cerastoderma edule, trematode intensity was always lower in the introduced species. These findings have three major implications: (1) introduced bivalves are not free of detrimental parasites which raises the question whether introduced species have an advantage over native species after invasion, (2) introduced bivalves may divert parasite burdens providing a relief for native species and (3) they may affect parasite populations by influencing the fate of infectious stages, ending either in dead end hosts, not being consumed by potential final hosts or by adding new hosts. Future studies should consider these implications to arrive at a better understanding of the interplay between native parasites and introduced hosts.     

Genotoxic potential of marine sediments from the North Sea

The alkaline comet assay is a method for detecting DNA strand breaks and alkali labile sites in individual cells. An in vitro system was used to investigate the genotoxic potential of complex mixtures such as organic extracts of marine sediments. DNA damage was induced in leukocytes isolated from carp (Cyprius carpio) by exposure to organic sediment extracts from the North Sea or hydrogen peroxide as positive control, respectively. The minimum concentration for significant effects ranged from 1 to 40 mg sediment dry weight per milliliter assay volume. The sensitivity of the method was enhanced by using the DNA repair inhibitor, 1-beta-D-arabinofuranosylcytosine (ara C). From the results, it can be suggested that total organic carbon (TOC) as well as the different compositions of contaminants present in the sediment extracts may contribute to the genotoxic effects observed. The comet assay can be applied successfully as an in vitro bioassay for investigations on genotoxicity of marine sediment extracts.     

The marine distribution of the Gannet Sula bassana in the North Sea

The overall pattern of counts made at sea reflects the well-known seasonal movements of Gannets. During the breeding season, fishing trips rarely exceed 150 km from colony and most are below one-third of that distance.     

Clonal Diversity in Introduced Populations of An Asian Sea Anemone in North America

Previous reports hypothesized that introduced populations of the Asian sea anemone Diadumene lineata (Verill, 1870 (Presented 1869) Communications of the Essex Institution 6: 51–104), which reproduces by fission, are often monoclonal or to be composed of few clones. To test this hypothesis, sea anemones were collected from thirteen sites in three non-native regions and one native region: Chesapeake Bay, New England, central California, and Japan. The internal transcribed spacer (ITS) region separating nuclear ribosomal RNA genes was amplified from each individual using PCR and surveyed for DNA sequence variation using single strand conformational polymorphism analysis (SSCP). Fifty-six distinct electrophoretic banding patterns were found in 268 anemones, and each pattern was considered a different genotype. The number of genotypes in a population ranged from one to thirteen. Only one sample (York River, Chesapeake Bay, n = 10) was monoclonal, although six populations were dominated (>50%) by single genotype. Only four genotypes were found in more than one population, and these were confined to single regions. Walker Creek, California was sampled in 1995 and 1997 and no genotypes were found in both years, suggesting rapid shifts in genotype frequency. We conclude that multiple genotypes of D. lineata have invaded North America and that the primary importance of clonal growth for introduced populations is the production of colonizing propagules.     

Microscopic species make the diversity: a checklist of marine flora and fauna around the Island of Sylt in the North Sea

Based on the past 150 years of research and ongoing time-series observations we give a comprehensive overview of marine species composition around the island of Sylt in the eastern North Sea. A total of 2758 species is listed according to the categories microplankton (591 species), zooplankton (137), nekton (118), benthic microflora (158), benthic macroflora (125), benthic micro-and meiofauna (1204), benthic macrofauna (509), birds and mammals (91), and neobiota (39). Plants account for a third of the species, most (85%) of them are microscopic Chromista. Among animals, 60% of the species are micro- and meiofauna though this faunal component is still insufficiently known. These figures are similar to records from the southern North Sea and therefore may by typical for temperate climate sedimentary coastal areas. A comparison with the total of marine species suggests that the small benthic fauna may be severely understudied over most of the world. Analysis of global change depends on sound baseline data and species inventories like this can assist in the detection of biodiversity changes. They emphasise rare species and the full range of local habitats while time-series measurements usually rely on a few selected habitats and biotic components to generate a very general picture of the state of an ecosystem.     

An annotated checklist of North Sea cartilaginous fish species

A checklist is compiled of all cartilaginous fishes (sharks, skates, rays and rat-fishes) which were so far recorded from the North Sea, along with their English common names. The objective of the study was to provide background information in light of the rapidly changing species diversity with overfishing and climate change as the main cause of changes in their status, thereby providing a reference tool for comparative purposes. This was also undertaken because usually the literature provides general information on the biology and covers the entire geographic range of a species but is not concerned with the status in a particular area. Presently the list contains 57 species, including 37 sharks, 19 species of skates and rays and 1 rat-fish species (also frequently called rabbit-fish or chimaera). Annotations were made for a number of selected species, as to their historical distribution and the present status.     

Free-living marine nematodes from the Southern Bight of the North Sea II. Notes on species of the Trefusiidae Gerlach, 1966

Three species of the Trefusiidae Gerlach, 1966 are described from the Southern Bight of the North Sea. Trefusia litoralis (Allgén, 1932) is redescribed and information is given on the intraspecific variation. Trefusia curvispiculosa sp.nov. is characterized by its typically curved spicular apparatus, up to now not found in other Trefusia species. Rhabdocoma riemanni Jayasree & Warwick, 1977 is synonymized with Rhabdocoma americana Cobb, 1920 and that species is redescribed.     

Biological consequences of marine pollution with special reference to the North Sea fisheries

Summary 1. A case of copper pollution on the Dutch coast is used to demonstrate that waste disposal in inshore waters can easily lead to damage to the living resources of the sea, since dilution is under such conditions a much slower process than is usually assumed.2. Pollution by domestic sewage, its direct hazards for human health, and its contaminating effect on shellfish, is discussed. Next to these direct and indirect health hazards, discharge of domestic waste may lead to eutrophication, which in its turn can contribute to the development of plankton blooms producing truly poisonous metabolites. Some examples of eutrophication of the marine environment are given.3. Of the industrial waste, examples are given which clearly demonstrate how dangerous discharge of heavy metals and pesticides can be, also in the marine environment. Possible effects of petrochemical waste products and of synthetic detergents and soaps are discussed.4. Radio-active waste disposal in sea is more carefully studied and monitored than disposal of other types of waste.5. The increasing quantity and variety of industrial waste is a reason for serious concern. Careful discrimination between the many products is advocated and discharge far offshore is advised for certain categories of pollutants. Pesticides and other very dangerous products should never be admitted in the shallow sea areas, so important as nursery grounds for the fishery resources.

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Biologische Konsequenzen der Meerwasserverschmutzung unter besonderer Berücksichtigung der Nordseefischerei

Kurzfassung Obwohl das Gesamtvolumen der Ozeane erheblich größer ist als der Süßwasservorrat der Welt, so kann doch das hemmungslose Einbringen von Haus- und Industrieabwässern in das Meer zu schädlichen Folgen für den Bestand der Meeresflora und -fauna führen. Besonders anfällig sind die Küstengewässer, da diese oft die Ernährungsgrundlage für viele Nutzfische bieten und zudem dort Austern und Miesmuscheln gezüchtet werden. Aus wirtschaftlichen Gründen erfolgt andererseits das Verklappen von Abfall und Unrat vorzugsweise dicht unter der Küste. Schädliche Wirkungen können erfolgen durch Bakterien- und Virusinfektionen, durch biologische Akkumulation von Schwermetallen und von Schädlingsbekämpfungsmitteln (unter ihnen besonders chlorhaltige Kohlenwasserstoffe), durch petrochemische Produkte, wodurch übler Geschmack bei Fischen und Muscheln hervorgerufen wird, und durch eine allgemeine Eutrophierung, die zu einer Vermehrung von unerwünschtem Plankton führen kann.

     

Bioactivity of marine organisms: part X--screening of some marine fauna from the Indian coasts

Methanolic and chloroform-methanol extracts of 25 identified species of marine fauna have been screened for a wide range of biological activities. Of these, 2 extracts exhibited diuretic activity, while antibacterial, antiviral, oxytocic and spasmolytic activities, were observed in 1 extract each.     

Bioactivity of marine organisms: Part IX--screening of some marine flora from the Indian coasts

Alcoholic extracts of 48 identified species of marine flora were screened for a wide range of biological activities. Of these, 3 extracts showed diuretic activity while 2 extracts showed hypotensive effect.     

Modelling marine ecosystem response to climate change and trawling in the North Sea

The marine ecosystem response to climate change and demersal trawling was investigated using the coupled hydrodynamic-biogeochemical water column model GOTM-ERSEM-BFM for three contrasting sites in the North Sea. Climate change forcing was derived from the HadRM3-PPE-UK regional climate model for the UK for the period 1950–2100 using historical emissions and a medium emissions scenario (SRESA1B). Effects of demersal trawling were implemented as an additional mortality on benthic fauna, and changes in the benthic–pelagic nutrient and carbon fluxes. The main impacts of climate change were (i) a temperature-driven increase in pelagic metabolic rates and nutrient cycling, (ii) an increase in primary production fuelled by recycled nutrients, (iii) a decrease in benthic biomass due to increased benthic metabolic rates and decreased food supply as a result of the increased pelagic cycling, and (iv) a decrease in near-bed oxygen concentrations. The main impacts of trawling were (i) reduced benthic biomass due to the increased mortality, and (ii) the increased benthic–pelagic nutrient fluxes, with these effects counteracting each other, and relatively small changes in other variables. One important consequence was a large decrease in the de-nitrification flux predicted at the two summer-stratified sites because less benthic nitrate was available. The effects of trawling scaled linearly with fishing effort, with greatest sensitivity to fishing in summer compared to fishing in winter. The impacts of climate change and trawling were additive, suggesting little or no non-linear interactions between these disturbances.     

A new species of Fauveliopsidae (Annelida) from the North Sea

A new species of the genus Laubieriopsis Petersen, 2000 is described based on 28 specimens collected in the north-east part of the North Sea. It is characterized by fixed number of chaetigers (22), paired genital papillae, bidentate neurochaeta of chaetigers 1-4, the absence of acicular chaetae on chaetigers 5-21 and, on the last chaetiger, one acicular and three capillary chaetae enlarged and directed backward. The present study brings the number of known species of Laubieriopsis to five and the number of Northeast Atlantic species of this genus to two.     

Fish disease as a monitor for marine pollution: the case of the North Sea

Summary The use of fish diseases to monitor marine pollution is reviewed and evaluated, with particular reference to the North Sea and associated waters. Criteria for epidemiological surveys are outlined, an international overview of research is given, and recent studies in the North Sea area are described and evaluated.The basic approach is to identify spatial and temporal patterns of disease prevalence, which can be related to pollution. A major obstacle is to distinguish effects of pollution from those of other variables, especially as most diseases appear to have a multifactorial aetiology. Field studies can be evaluated against a number of criteria: these include the accuracy and precision of prevalence estimates, the extent to which possible causal factors other than pollution are taken into account, and whether or not exposure of the study population to pollution is measured directly.A distinction can be made between intensive, thorough studies, which frequently use a histopathological approach, and the more extensive surveys of large numbers of fish for grossly observable lesions. Broadly speaking, North American research has emphasized the former approach, and research in the North Sea the latter. Nevertheless, although the most comprehensive evidence for a causal relationship between disease and pollution has been gathered in North America, there are also good examples from the North Sea area, particularly in local areas with distinct sources of pollution. The data from wider-ranging surveys are more ambiguous: while some provide circumstantial evidence for a role of pollution, the apparent complexity of disease aetiology and the limitations of the epidemiological approach may prevent any clear demonstration of pollution as a cause over wide geographical areas. Extensive surveys are nevertheless useful for detecting long-term trends in disease prevalence and hot-spots of anomalously high prevalence, and for examining the relationship between disease and a complex of environmental variables.For the future, greater emphasis should be placed on the recording of liver lesions, on the measurement of exposure to pollution, and on experimental work.     

Protected areas in the North Sea: An absolute need for future marine research

There are many signals that different human activities affect the marine ecosystem on local and sometimes regional scales. There is evidence that in the Dutch sector of the North Sea at least 25 species have decreased tremendously in numbers or have totally disappeared. But what has caused their disappearance: fisheries, pollution, eutrophication, climatic changes, or a combination of causes? On the Dutch Continental Shelf, the fisheries are now so intensive that every square metre is trawled, on an average, once to twice a year. Furthermore, it has been shown that trawling causes direct damage to the marine ecosystem. This indicates that the “natural” North Sea ecosystem we are studying is already a heavily influenced system. And what is the value of data on the diversity and production of benthic animals, if the research area has been raked by beamtrawl gear an unknown amount of times before sampling? To be able to study the natural trends in the marine ecosystem, or to answer the question which human activity has most influenced the ecosystem, there is an absolute and immediate need for protected areas to be established. The size of the protected areas must be determined by the behaviour of that species characteristic for the area. In such areas, where fisheries and local pollution would be forbidden or very limited, scientific research into the species composition and age distribution of different populations should be carried out and trends should be established.     

Hitch-hiking on floating marine debris: macrobenthic species in the Western Mediterranean Sea

Marine litter has been defined as solid materials of human origin discarded at sea, or reaching the sea through waterways. The effect of marine debris on wildlife, tourism and human health is well documented and there is considerable scientific literature about plastic litter in the sea and over the seabed, mostly highlighting the possible impact on marine mammals and tourism. Dispersal of marine and terrestrial organisms on floating objects has biogeographical and ecological interest. For some species, extension of their geographical range is more likely to be related to transport of mature individuals on floating rafts than to the active or passive dispersal of reproductive propagules. Variability and variety of rafting materials has increased dramatically in recent years and marine litter has been used widely as a raft by ‘hitch-hiking’ species. This paper reports on the benthic invertebrates living on marine debris transported by wind and surface currents over the western Mediterranean Sea. Plastics accounted for the major item of debris because of poor degradability, however glass, cans, fishing nets and polyurethane containers, were also found. Macro-benthos living on raft material comprised mainly molluscs, polychaetes and bryozoans. Large fish were found commonly below large plastic bags. Estimations of the distances that may be covered by hitch-hiking species and the contribution of rafting to the theoretical dispersal of species is provided.