Rutger Rosenberg

Eutrophication—The future marine coastal nuisance?

Abstract Increased inputs of nutrients to marine coastal areas over the last decades have created a basis for eutrophication of the waters surrounding Sweden. In combination with relatively low water exchange in these vertically stratified and almost non-tidal waters, local and regional effects of increased macro-algal biomass, and decreased oxygen concentrations in bottom water leading to mortalities of benthic animals and decreased fish catches have at times been observed. The effects were first noted in the Baltic, but are now obvious also in Swedish and Danish coastal areas in the Kattegat and the Belt Sea. Similar symptoms have recently also been recorded off the Danish North Sea coast. Other shallow coastal and shelf areas, where stratification occurs, can be regarded as potentially eutrophic risk areas.

Bioresuspension and biodeposition: a review

Abstract The present literature on biologically mediated fluxes from the benthic nepheloid layer (BNL) across the sediment-water interface into the sediment and vice versa is reviewed. The processes involved are categorised according to direct bioresuspension and biodeposition, i.e. direct interception of the animal with particles, and those effects, which are indirectly created by benthic organisms, e.g., changes of physical properties in the sediments, constructions like tubes and pits and the corresponding changes in hydrodynamic conditions. It is concluded that benthic organisms significantly increase the flux of particles across the interface and that the physically created fluxes are easily modified by a factor of 2 and more.

Eutrophication and Contaminants in Aquatic Ecosystems

Abstract Eutrophication and persistent pollutants are two of the main environmental problems in European marine and freshwater ecosystems. As they tend to co-occur, interactive processes between eutrophication and contaminants are suggested, that may lead to environmental effects that cannot be predicted from each process alone. In order to predict the consequences of remedial measures (changing the input of organic matter, nutrients and contaminants) it is important to understand mechanisms that alter the bioavailability and fate of contaminants. The environmental risks will depend on the speciation of contaminants and their association to media and matter and by that means affect exposure. Furthermore, the risks will depend on the mobility of the substances and their pathways in food chains. In 1995, the Swedish Environmental Protection Agency initiated a 5-year research program Interactions between EUtrophication and CONtaminants (EUCON). A background document was prepared listing a number of relevant questions and hypotheses. On the basis of this document a program was launched, addressing the problems related to the interaction between eutrophication and contaminants (persistent organic compounds and trace metals) in the marine environment, with focus on the Baltic Sea, and in lakes. This paper summarizes the state-of-the-art, hypotheses and highlights from the research program with emphasis on the implications and applications of the results.

Negative oxygen trends in Swedish coastal bottom waters

Abstract Temporal trends in annual minimum oxygen concentrations in the bottom water of 14 marine coastal areas have been investigated from the early 1950s or 1960s up to 1984. At twelve stations a significant declining trend could be demonstrated, but at three of these that trend could have been caused by increased recordings over time. The likely reason for the decline is suggested to be increased large scale eutrophication.

Nutrient Enrichment Drives Gulf of Mexico Hypoxia

During most summers over the past 30 years, bottom dissolved oxygen across a large area of the Louisiana and upper Texas continental shelf declined to concentrations too low (hypoxia) for most fish and large invertebrate animals to survive. This area is one of the best known “dead zones” proliferating around the world [Diaz and Rosenberg, 2008]. During July 2008, hypoxic bottom waters extended across 20,720 square kilometers (Figure 1), but they were probably even more extensive because winds from Hurricane Dolly mixed the waters off Texas before the survey could be completed.

Spatial dispersion of an estuarine benthic faunal community

Abstract By means of a box-sampler 20 moderately undisturbed sediment samples were obtained, which were subsampled on board the ship. The fauna in the upper 0–5 cm of the sediments was compared to that in the 5–10 cm layer; almost all species collected in both strata were found in the upper 0–5 cm. About 64% of the individuals and 74% of the biomass were restricted to this upper layer. A sample area of 0.5 m2 (depth 0–10 cm) was found to be sufficient to make a quantitative evaluation of the benthic community. The horizontal dispersion of the macrobenthic community was studied using the variance/mean ratio and its dependence on sample size is discussed. The abundant species occurred in patches larger than 0.06 m2 and high densities were correlated with aggregation.

Effects of eutrophication on contaminant cycling in marine benthic systems

Abstract Effects of inputs of organic matter were studied on bioavailability and cycling of hydrophobic organic contaminants (HOCs) in benthic ecosystems of the Baltic and Kattegat Seas. In laboratory experiments, effects of microalgae additions were studied on the bioaccumulation of HOCs (PCBs and PAHs) by the blue mussel Mytilus edulis, the brittle star Amphiura filiformis, and the polychaete Nereis diversicolor. Contrary to the equilibrium partitioning theory, bioaccumulation was proportional to the concentrations of algae and organic carbon. This was attributed to the high nutritional quality of the algal organic carbon and suggests that feeding rather than equilibrium partitioning governed bioaccumulation in these species. In the field, annual mass fluxes of PCBs in blue mussels and in brittle stars were estimated, as well as contaminant transfer to higher trophic levels. Our results suggest that: i) Eutrophication processes may contribute to increase HOC accumulation in benthic species. ii) Temporal variation in the quantity and quality of organic carbon needs to be considered when assessing contamination of benthic systems. iii) Macrofaunal feeding activities are important for the benthic-pelagic coupling of HOCs. iv) Bioturbation enhances the release of HOCs from sediment to overlying water.

Stress Tolerance of Ecosystems

It is conventionally argued that a stable ecosystem, namely one with high species-diversity and high constancy in physical parameters, is less sensitive to additional stress than a system with varying physical parameters and low species-diversity. By this logic, the Baltic would be more susceptible to additional stress, such as that of pollution, than the North Sea. Examples of irreparable damage to some of the most stable ecosystems in the world, such as coral reefs and tropical rain-forests, suggest, on the contrary, that these systems are more vulnerable than low-diversity ecosystems, such as a brackish-water zone in the mouth of a river or a coniferous forest in a temperate region. Studies of stress tolerance in estuaries showed that the species already living under stress, such as that of reduced and changing salinities, were more tolerant to pollution than species in a less fluctuating environment. This adaptability to environmental changes seems to be characteristic of ecosystems with a low degree of individual specialization and high genetic diversity (i.e. a large number of alleles). Following this conclusion, we question the underlying assumptions in the statement that for example the Baltic Sea, which can be regarded as a large estuary, is an area particularly susceptible to stress; purely marine ecosystems are probably more sensitive. Ecosystem stress-tolerance should be made a top priority in ecological research; this is a necessity inter alia for future localization of industries, in order to minimize their effects on the environment.

Degradability of some chlorinated aliphatic hydrocarbons in sea water and sterilized water

Abstract The degradability of the substances chloroform, 1.1.2-trichloroethane, 1.1.2-trichloroethene and 1.1.2.2-tetrachloroethene was investigated in sea water and sterilized fresh water. Four different systems were used: (1) daylight, open system; (2) daylight, closed system; (3) darkness, closed system; (4) darkness, 2 atm closed system. The analytical procedure is described The disappearance of the substances was greatest in the aquaria indicating that the substances can escape because of their vapour pressure. In the other systems the decrease within eight days was less than 40%. It is suggested that the closed flask system is to be preferred to other systems.

Biological effects and physical properties in the marine environment of aliphatic chlorinated by-products from vinyl chloride production

Abstract A mixture of short-chained aliphatic hydrocarbons, the so called EDC-tar, is formed as a byproduct from vinyl chloride production in quantities of approx. 75,000 tons annum −1 in Northern Europe. Most of this is dumped into the sea. In 1970, concentrations of EDC-tar from the North Sea were reported to be as high as 10 per cent of that causing acute toxic effects on marine organisms (J ensen et al., 1970). This work was undertaken to find out the behaviour of some components of the EDC-tar in the marine environment. Dumped into the sea, EDC-tar has a tendency to disperse and to adhere to particles. Acute toxicity of these ClC components, evaluated by LC50 48 h tests, was found to be approx. 2·5–9 ppm for some marine animals. Accumulation factors of between 10 and 3 × 10 3 were estimated for animals presented to EDC-contaminated sea water. Accumulation in cod fed with EDC-contaminated shrimp was higher in liver than in muscle. Excretion was rapid when feeding was discontinued, and the biological half-lives of the ClC compounds were found to be a few weeks. Sublethal EDC-concentrations were found to bring about disorders in growth in the polychaete Ophryotrocha labronica and to reduce swimming ability in the barnacle Balanus balanoides . In Allium cepa , c-mitotic effects of EDC-tar were observed.