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An integrated biological effect monitoring concept has been tested in flounder (Platichthys flesus L.) from four locations with different anthropogenic impact in the German Bight. During 3 years of sampling, biomarkers at all levels of biological organisation from the molecular to the ecosystem level were applied and tested on 742 individual fish of body lengths between 18 and 25 cm. At the ecosystem level, the fish were taken as a habitat for the parasite assemblage. The hypothesis was that changes in the environment might lead to changes in the species diversity of parasites and in the infection intensity of single species, as well as between heteroxenic and monoxenic parasite species (H/M ratio). At the molecular level, activity of the CYP1A-dependent monooxygenase ethoxyresorufin O-deethylase (EROD) was used as a biomarker of exposure. At the subcellular level, the integrity of lysosomal membranes in hepatocytes was taken as an indicator of non-specific acute and chronic toxic effects. Both biomarkers are recommended by the ICES Advisory Committee on the Marine Environment for the application in biological effects monitoring programmes. In addition, neutral lipid content in the liver was used as a marker for pathologically induced fat accumulation. In the same individual fish, a new method for the measurement of macrophage aggregate activity in the liver was tested for its application and reliability in reflecting immunosuppression. Tests were accompanied by chemical analysis of standard organochlorine and heavy metal residues in flounder tissue. A total of 33 parasite species were found. As an indicator species, the mean abundance of Trichodina sp. reflected best the pollution gradient observed with highest infection intensity at the most polluted location. Species diversity was significantly higher in fish caught near the reference site and significantly lower in fish from the polluted Elbe estuary. The use of the heteroxenous/monoxenous species ratio as a marker was not useful at the locations investigated because of the dominance of heteroxenous species at all habitats. Since EROD activity and macrophage aggregate activity were dependent on sex and maturity of female flounder, only male fish were taken into consideration for the integrated evaluation of data. All biochemical and histochemical tests were able to reflect accurately the site-specific differences, as well as an observed pollution event at the end of 1995 as determined by chemical analyses. The correlation analysis revealed a connection not only between the single parasitological and biochemical parameters but also within these groups. The non-specific immune response and Trichodina infection intensity were correlated with all other parameters, leading to the assumption that these may serve as links between the lowest and the highest levels of biological organisation. The simultaneous use of metabolic and parasitological results facilitated the interpretation of the observed variations of the data and the distinction between natural ...

Rearing the eggs of cod (Gadus morbua), flounder (Pleuronectesflesus) and plaice (Pleuroneetes platessa) under combined temperature and salinity conditions. Eggs of Baltic cod (Gadus morhua L.), flounder (Pleuronectes flesus L.) and plaice (Pleuronectes pIatessa L.) have been reared under combined temperature and satinity conditions (0°-16 ° C, 7 %-42 %0 S). Combined temperature and salinity influences on embryonic development were investigated. Optimum temperatures for the rearing of cod eggs range from 4 o to 80 C, and optimmn salinities from 20%0 to 33 %0 S. Flounder eggs develop best at 4 o C and in 33 %0 S, and plaice eggs at 6 o C and in 20 %o S. Suboptimum conditions result in lower percentages of larval hatching and survival, and increased morphological anomalies such as curvature of tail and body. Low salinities (20 %o and 15 %o S) cause swollen yolk sacs which, in experiments with flounder eggs, lead to jaw deformities. Rearing at low salinity decreases speed of development. Optimum salinity varies as a function of incubation temperature and influences variations in optimum rearing temperature. Extremely low salinities (20 %0 and 15 %0 S) are tolerated best at optimum or lower temperatures. From the results of these experiments it can be concluded that bra&ish water races of these fishes are likely to exist in the Baltic Sea. EINLEITUNG UND FRAGESTELLUNG Temperatur und Salinit~it sind neben Sauerstoffgehalt und Licht die physiologisch wichtigsten Faktoren im Leben yon See-und Bra&wasserorganismen. Auf Grund zahlreicher Untersuchungen ist deutlich geworden, dai~ insbesondere Temperatur und Satini-t~it zusammen betrachtet werden miissen, wenn die Reaktion von Wasserorganismen auf Temperatur oder Salzgehalt ihrer Umwelt untersucht werden soll. Die komplexe Korrelation zwischen der biologischen Wirkung dieser beiden Faktoren wird besonders

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The complex interactions between parasites, hosts and the environment are influenced by the stability of the ecosystem. Heteroxenous parasites, with complex, multiple-host life cycles, can persist only in habitats where the full range of their required hosts are present. Conversely, in impoverished environments such as those impacted by environmental stress, monoxenous species that have simple, single-host life cycles are likely to predominate. In the present study, we analyzed the ratio between heteroxenous and monoxenous (H/M) parasites as well as parasite species richness (S H /S M ) and species diversity in rabbitfish (Siganus rivulatus) collected from several sites in the Red Sea. The rabbitfish is a Suez Canal immigrant, well established in the eastern Mediterranean, and fish were also collected from a site on the Mediterranean coast of Israel. Separate treatment of the micro-and macroparasite components of the rabbitfish parasite communities in the Red Sea suggested that macroparasites only -monogenea and gut parasites -were better indicators than the parasite community as a whole. Quantification of macroparasites is accurate, saves time and effort, produces more accurate data and better differentiates between sites. Higher H/M ratios and S H /S M ratios were found in the rabbitfish collected at the ecologically stable habitat of the coral reef compared to rabbitfish from sandy habitat or mariculture-impacted sandy habitat. The results of the study emphasized the negative impacts of cage mariculture on the environment. The rabbitfish collected near the mariculture farms supported the poorest and least diverse parasite communities of all sampled sites, with virtual depletion of heteroxenous species, and even reduction of gill monogenean infections on the hosts. When results from the Mediterranean sites were compared with those of the Red Sea, the data showed full representation of monoxenous parasites (all but one of Red Sea origin), while heteroxenous species were completely absent. We may therefore regard the Mediterranean as a simulation model for a severely environmentally deteriorated, impoverished habitat, in which all or part of the intermediate host species have been depleted, enabling survival of the monoxenous parasite species only. Parasitological investigations were supplemented by testing the activity of cytochrome P 450-dependent mono-oxygenase EROD as a measure of exposure, and lysosomal stability as a measure of toxic effect in the liver of rabbitfish. The results underline the parasitological findings, showing that fish caught at the impacted sandy beach location in the Red Sea have significantly higher EROD activity and a decreased membrane stability compared with animals from the coral reef. In comparison, EROD activity values in rabbitfish from the Mediterranean Sea were double, while lysosomal membrane stability was half that measured at the most impacted Red Sea location.