The human impact in the German Bight, in the form of anthropogenic eutrophication, has been documented by a 30-year time-series measurement near the island of Helgoland. Since 1962, the Biologische Anstalt Helgoland has measured inorganic nutrients and phytoplankton abundance from daffy samples at Helgoland Roads, a position 60 km off the main source of eutrophication, the River Elbe. Since the early 'sixties, phosphate concentrations rose for about a decade, levelling off to about twice the former concentrations for another decade, and then decreasing (since 1982) as a result of phosphate-reducing measures. Nitrate concentrations, however, have only increased since 1980/81, following Elbe river flood events. In 1987, three times the former concentrations were reached. A decrease has been observed only since 1991. This different development of phosphorus and nitrogen eutrophication led to a shift of inorganic N/P-ratios in the German Bight. The phosphate increase was more pronounced in the late summer "regeneration mode" conditions, the nitrate increase in the winter months. The eutrophication is not restricted to the inner German Bight and coastal waters of a salinity of < 33, but has also occurred in more saline waters at S > 33 psu (practical salinity unit), as characteristic for the outer German Bight. In this more saline water, phosphate and nitrate maximum levels occurred three years later, compared with the average Helgoland data, which are more representative of the inner German Bight. It is suggested that suspended particulate organic matter, as a long-distance carrier of nutrients, might have caused this delayed eutrophication in the outer German Bight waters. While the human impact is obvious as to nutrient concentrations, it is less obvious in phytoplankton stock enhancement. A general increase in phytoplankton biomass (about 3-4 times) was found, but this was mainly due to unidentified nanoflagellates of unknown trophic state, and subject to methodological errors. The causal relationships of phytoplankton stocks and eutrophication are not clearly understood, as natural variability is large and hydrographical factors possibly dominate. Additional nutrient input by Elbe river floods did not always result in elevated phytoplankton stocks near Helgoland, while extended periods of vertical density stratification of the German Bight water caused large plankton blooms.

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In February/March 1983 and 1984 a survey of pelagic fish eggs was conducted in the western Baltic (Kiel Bight), employing a horizontally towed plankton net tl m ~ and 300 ~tm mesh). Maximum egg numbers in the upper meter of the S = 21 x 10 -3 salinity layer were 200-100 m -a. The most abundant eggs were cod (up to 142 eggs. 100 m-3), followed by plaice (up to 74 eggs. 100 m -3) and flounder (20 eggs. 100 m-3). A considerable percentage of embryos of all species displayed aberrant development..In 1983 18 % of cod, 22 % of flounder and 24 % of plaice eggs caught contained defective embryos; in 1984 this number was larger, ranging from 28 % in plaice over 32 % in cod to 44 % in flounder. Early developmental stages showed the highest malformation rates (up to 51% in the case of early flounder embryos). With progressive development, malformations decreased in numbers, being lowest prior to hatching. Highest rates of malformations were recorded in the Mecklenburg Bight in 1983. A second area with high incidence of malformation rates was located south and east of the island of Langeland. Several reasons, including environmental and anthropogenic factors, for the occurrence of malformed embryos in pelagic fish eggs are discussed. The potential of malformation rates in embryos of pelagic fish eggs as a tool for monitoring is considered.

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During the Bremerhaven Workshop, ichthyoplankton samples were collected with horizontal subsurface hauls at 28 stations from the inner German Bight to the Dogger Bank. Directly after being caught fish embryos were examined a l~v e for morphological developmental defects under a dissecting microscope. Investigations on chromosomal aberrations were confined to preserved blastula stages of dab and were carried out later in the laboratory. Main species sampled were dab Limanda limanda, plaice Pleuronectes platessa, sprat Sprattus sprattus and whiting Merlangius merlangus. Because of their widespread distribution and high numerical occurrence, dab embryos were best suited for the detection of regional differences in malformation frequencies. The proportion of malformations in the most sensitive early developmental stage of dab reached 32 % in the inner part of the German Bight and fell to 9 % further offshore, increasing again at the Dogger Bank to values up to 31 %. Data collection was acconlplished with a computerized data sampling/evaluation/presentation system, and results concerning the morphological differences of malformation frequencies were available directly after observation. Thus, the method as described below proved to be a suitable approach for b~ological effects mon~toring. Anaphase aberration frequencies in dab en~bryos reached a peak of 63 % in the inner part of the German Bight, whereas the lowest value (51 %) was detected far offshore at a less polluted station; aberrations on the Dogger Bank were found to be 57 %. Investigations on the chromosomal aberrations in the same material used for the determination of morphological aberrations provided an opportunity to evaluate the potential effects of contaminants at the chromosome level.