Showing papers in "Advances in Marine Biology in 1999"

The Assessment of Marine Pollution - Bioassays with Bivalve Embryos and Larvae

Abstract: Tens of thousands of synthetic substances are in existence today and hundreds of new compounds are being introduced every year. Because of the complexity of the physico-chemical interactions between pollutants and the marine environment, the potential toxicity of contaminants can be assessed adequately only by means of bioassays with living organisms. From a practical point of view, a bioassay needs to be sensitive and scientifically valid, yield rapid results at moderate cost, and the organism in question must be readily available. Ecotoxicological bioassays with bivalve embryos and larvae fulfil these criteria better than most other tests. They have increasingly come into use during the past three decades and are now commonly employed to ascertain the biological effects of pure chemicals, as well as to determine the quality of effluents, coastal waters and sediments sampled in the field. There do not appear to be very great differences between bivalve species with regard to larval sensitivity to toxicants. The principal species for bioassays are oysters (Crassostrea gigas and C. virginica), and mussels (Mytilus edulis and M. galloprovincialis). Bioassays are conducted with gametes and larvae of ail ages: sperm and unfertilized eggs, embryos, young D-larvae, intermediate umboned larvae, and pediveligers towards the end ofthe pelagic period. Embryos are usually the most sensitive stage. Recent advances now also permit bioassays on metamorphosing pediveligers, a method particularly suited to investigate the effects of adsorbate-contaminated surfaces. There are various criteria for the assessment oftoxic effects, including embryogenesis success (abnormalities), larval growth, mortality, physiology (e.g. feeding or swimming activity), and metamorphosis success. Chronic toxicity studies may be carried out over periods ofseveral weeks, but larval rearing in the laboratory requires considerable effort (e.g. cultivation of algal food). The method of choice for investigations of acute toxicity and for routine monitoring studies is the embryo bioassay because it is very sensitive, relatively simple, and produces results within 24 or 48 hours. The data obtained by different investigators are often difficult to compare, however, because of differences in methodology. There is no firmly established procedure, and further simplification and standardization of techniques is required. In bioassays with a single pollutant, the effective toxic concentration may span several orders of magnitude, depending on bioassay procedures, larval stage and choice of response. Tributyl-tin (TBT) is the most toxic compound ever bioassayed with bivalve larvae, with effective concentrations (EC50) as low as a few nanograms per litre (i.e. 10−3 ppb). Heavy metals (particularly mercury, silver and copper) are next in order of toxicity, with EC50 values between a few micrograms per litre (ppb) and several hundred ppb. Chlorine and some organochlorine pesticides may also have EC50 values of less than 100 ppb, while detergents and petroleum products are generally less toxic

Growth Performance and Mortality in Aquatic Macrobenthic Invertebrates

Abstract: Growth performance and mortality are two topics related closely to population dynamics of benthic macroinvertebrates. A new measure of overall growth performance for benthic invertebrate populations, the index ψ = log(maximum body mass/maximum age) is introduced. This index makes growth of populations and species comparable and is likely to be a species-specific feature. Differences in the index ψ among taxa and living modes as well as the relationship between growth performance and exploitation by man are analysed and discussed. Section 4 on mortality analyses the relationships between mortality and productivity in benthic invertebrate populations. An empirical model to estimate the natural mortality rate M of benthic populations from maximum body mass, maximum age and water temperature is constructed.

The biochemical ecology of marine fishes

Abstract: Introduction. Adaptations of Fish. Strategies of Adaptation. Molecular and Metabolic Aspects of Life Cycles. The Metabolic Basis of Productivity and the Balance of Substance and Energy. Indicators of Fish Condition. Intraspecific and Interspecific Differentiation of Fish. Conclusions. Acknowledgments. References. Appendix. Index. Cumulative Index of Titles. Cumulative Index of Authors.

Population Structure and Dynamics of Walleye Pollock, Theragra chalcogramma

Abstract: The population biology of walleye pollock, Theragra chalcogramma, is described including its life history, population dynamics, genetic structure and metapopulation structure. Walleye pollock is an important species in the ecosystems of the subarctic Pacific Ocean, and is one of the world’s largest fisheries. The population dynamics of pollock is driven by recruitment, which is associated with environmental variability. Management of pollock stocks is based on harvests from large geographic regions. However, lumping stocks within these regions may be adverse to conservation and management goals. Historical genetic studies of pollock have produced some conflicting results and comprehensive genetic studies are needed. A summary view of genetic structure in walleye pollock to date suggests a pattern of geographic stock structure, with varying levels of gene flow between major regions. Phenotypic differences between stocks, elemental composition of otoliths and parasite studies indicate restricted mixing of juveniles and adults. Genetic differences appear between broad regions, but resolution between adjacent stocks, especially within the eastern Bering Sea, is currently lacking. Recent studies indicate genetic differentiation among pollock in the Gulf of Alaska and Bering Sea, possibly resulting from reduced gene flow owing to larval retention mechanisms or strong natal homing. The global population of pollock does not fit into a strict metapopulation framework, but some neighbouring populations may be considered as metapopulations. Whether there is either density-driven migration of strong recruitment cohorts, or population sinks, is controversial and more information is needed. Stock mixing problems can be best addressed by means of high resolution genetic techniques in conjunction with tagging and the use of natural environmental markers.

Population Genetics of Bathyal and Abyssal Organisms

Abstract: Publisher Summary Bathyal and abyssal environments are characterized by relatively stable physical parameters, especially temperature, salinity, oxygen concentration, and hydrostatic pressure. Exceptions to this stable environment are found within hydrothermal vent fields, hydrocarbon seeps, groundwater seeps, subduction seeps, and oxygen-minimum zones (OMZs). Organisms may also exhibit enzymatic, metabolic, and morphological adaptation to conditions of low oxygen concentrations and/or the presence of high concentrations of naturally occurring toxic compounds. At present, there are no data on the effects of such adverse environmental factors on the genetics of deep-sea species. Biochemical techniques have been used in the majority of genetic studies on deep-sea species and populations. These techniques have the disadvantage that they require fresh tissue for enzyme extraction but the advantage that enzyme loci are functional proteins and can demonstrate environmentally driven selection. Molecular genetic techniques have the disadvantage that they are expensive and generally require a long period of optimization for a particular study. However, these techniques can utilize tissues preserved in alcohol or buffering solutions, which is a major consideration when deep-sea cruises are of long duration and in remote locations. Biochemical and molecular genetic techniques can be applied at different systematic levels of genetic separation, but molecular techniques have a broader spectrum of application. Analysis of the relationship between genetic identity and systematic separation for deep-sea taxa demonstrate that levels of genetic identity between conspecific, congeneric, and confamilial populations are broadly similar between deep-sea organisms and those from other habitats. These data imply that speciation may occur at a similar rate in the deep sea in comparison to that in other environments, and that approximate times of evolutionary divergence for species and genera are three million and 25 million years, respectively.