The objectives of this study were to determine rDNA sequences of the most common Dinophysis species in Scandinavian waters and to resolve their phylogenetic relationships within the genus and to other dinoflagellates. A third aim was to examine the intraspecific variation in D. acuminata and D. norvegica, because these two species are highly variable in both morphology and toxicity. We obtained nucleotide sequences of coding (small subunit [SSU], partial large subunit [LSU], 5.8S) and noncoding (internal transcribed spacer [ITS]1, ITS2) parts of the rRNA operon by PCR amplification of one or two Dinophysis cells isolated from natural water samples. The three photosynthetic species D. acuminata, D. acuta, and D. norvegica differed in only 5 to 8 of 1802 base pairs (bp) within the SSU rRNA gene. The nonphotosynthetic D. rotundata (synonym Phalacroma rotundatum[Claparède et Lachmann] Kofoid et Michener), however, differed in approximately 55 bp compared with the three photosynthetic species. In the D1 and D2 domains of LSU rDNA, the phototrophic species differed among themselves by 3 to 12 of 733 bp, whereas they differed from D. rotundata by more than 100 bp. This supports the distinction between Dinophysis and Phalacroma. In the phylogenetic analyses based on SSU rDNA, all Dinophysis species were grouped into a common clade in which D. rotundata diverged first. The results indicate an early divergence of Dinophysis within the Dinophyta. The LSU phylogenetic analyses, including 4 new and 11 Dinophysis sequences from EMBL, identified two major clades within the phototrophic species. Little or no intraspecific genetic variation was found in the ITS1–ITS2 region of single cells of D. norvegica and D. acuminata from Norway, but the delineation between these two species was not always clear.

No abstract

Every year since 1927 oxygen concentration, temperature, and salinity have been measured at 3 1 stations along the Norwegian Skagerrak coast during the latter half of September. At all analyzed depths (10 m, 30 m, and bottom water) there have been significant decreases in oxygen saturation all along the coast. In some inner coastal areas, this has led to oxygen deficiency. At intermediate depths (10 and 30 m), there is no trend in oxygen saturation until the middle of the 196Os, after which an almost linear decrease is observed until the 1990s. An explanation for the decreased oxygen saturation in the intermediate layer is increased heterotrophic activity relative to primary productivity. In the bottom water, on the other hand, oxygen saturation did not change until the beginning of the 1970s when it decreased rapidly to a significantly lower level within a few years and then stabilized at this low level after the middle of the 1970s. The higher oxygen consumption in the bottom water may be due to increased sedimentation of phytoplankton and phytodetritus as a result of greater phytoplankton biomass and, in particular, to less grazing by herbivores. No corresponding changes in meteorological or hydrographical variables were found; we therefore conclude that the decreasing oxygen concentrations are most likely caused by increased nutrient load of the coastal waters. The present evidence suggests that the decrease in bottom-water oxygen is due to structural changes in the pelagic community.

A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques -nine classical microscopic-based and eight molecular methods -were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect cells at the lowest concentration tested, 100 cells L À1 , but the variance was high for methods using small volumes, such as counting chambers and slides. In general, the precision and reproducibility of the investigated methods increased with increased target cell concentration. Particularly molecular methods were exceptions in that their relative standard deviation did not vary with target cell concentration. Only two of the microscopic methods and three of the molecular methods had a significant linear relationship between their cell count estimates and the A. fundyense concentration in experiment 2, where the objective was to discriminate that species from a morphologically similar and genetically closely related species. None of the investigated methods were affected by the addition of a natural plankton community background matrix in experiment 3. The results of this study are discussed in the context of previous intercomparisons and the difficulties in defining the absolute, true target cell concentration. #

No abstract