Effect of continuous nutrient enrichment on microalgae colonizing hard substrates

In order to understand the effect of changing nutrient conditions on benthic microalgae on hard substrates, in-situ experiments with artificial substrates were conducted in Kiel Fjord, Western Baltic Sea. As an extension of previous investigations, we used artificial substrates without silicate and thus were able to supply nutrient media with different Si:N ratios to porous substrates, from where they trickled out continuously. The biofilm developing on these substrates showed a significant increase in biovolume due to N + P enrichment, while Si alone had only minor effects. The stoichiometric composition of the biomass indicated nitrogen limitation during most of the year. The C:N ratios were lowered by the N + P addition. The algae were dominated by diatoms in most cases, but rhodophytes and chlorophytes also became important. The nutrient treatment affected the taxonomic composition mostly at the species level. The significance of the results with regard to coastal eutrophication is discussed

The role of interactions between Prorocentrum minimum and Heterosigma akashiwo in bloom formation

We examined the growth and interactions between the bloom-forming flagellates Prorocentrum minimum and Heterosigma akashiwo using bi-algal culture experiments. When both species were inoculated at high cell densities, growth of H. akashiwo was inhibited by P. minimum. In other combinations of inoculation densities, the species first reaching the stationary phase substantially suppressed maximum cell densities of the other species, but the growth inhibition effect of P. minimum was stronger than that of H. akashiwo. We used a mathematical model to simulate growth and interactions of P. minimum and H. akashiwo in bi-algal cultures. The model indicated that P. minimum always out-competed H. akashiwo over time. Additional experiments showed that crude extracts from P. minimum and H. akashiwo cultures did not affect the growth of either species, but both strongly inhibited the growth of the bloom-forming diatom Skeletonema costatum. Further experiments showed that it was unlikely that reactive oxygen species produced by H. akashiwo were responsible for the inhibition of P. minimum growth

Vertical distribution of summer phytoplankton in the western Black Sea during 1991-1995 with respect to some environmental factors

The present paper deals with the vertical distribution of summer phytoplankton in different layers (SHL, TCL and Ca) at selected subregions of the western Black Sea. A comparison between the north-western, western and southern Black Sea is also presented. A special statistical software package was used to display the core species along the vertical axis and to select environmental variables explaining the community distribution. Despite the subregional differences the results reveal that about 50% of the total biomass was maintained in the SHL, about 40% in the TCL and from 10% to 20% in the CIL depending on the position and depth of each layer. The environmental factors, especially nutrients have more important implications for algal species composition and abundance in the SHL, while for the deep flora the formation of CIL waters and the mechanisms of biological control may be the more significant processes

Progress in Understanding Harmful Algal Blooms: Paradigm Shifts and New Technologies for Research,Monitoring, and Management

The public health, tourism, fisheries, and ecosystem impacts from harmful algal blooms (HABs) have all increased over the past few decades. This has led to heightened scientific and regulatory attention, and the development of many new technologies and approaches for research and management. This, in turn, is leading to significant paradigm shifts with regard to, e.g.,our interpretation of the phytoplankton species concept (strain variation), the dogma of their apparent cosmopolitanism, the role of bacteria and zooplankton grazing in HABs, and our approaches to investigating the ecological and genetic basis for the production of toxins and allelochemicals. Increasingly,eutrophication and climate change are viewed andmanaged as multifactorial environmental stressors that will further challenge managers of coastal resources and those responsible for protecting human health. Here we review HABscience with an eye toward new concepts and approaches,emphasizing, where possible, the unexpected yet promising new directions that research has taken in this diverse field

Physical, Chemical, and Biological Data Sets of the TU Black Sea Data Base: Description and Evaluation

The data set of the TU Black Sea Data Base consists of the individual cruise data sets of the Data Contributing Partner Institutions and of several 'external' cruises which data are freely accessible (available) from other sources (databases). Basically, the paper constitutes a brief description of the data of the TU Black Sea Data Base (physical, biogeochemical and biological), and covers the issues of data quality and coverage as well as of sampling techniques and methods of samples treatment