Is the invasion of Prorocentrum minimum (Dinophyceae) related to the nitrogen enrichment of the Baltic Sea?

The abundance of the invasive, bloom-forming dinoflagellate Prorocentrum minimum (Pavillard) Schiller and triangular, oval, and oval-round cell shapes were examined relative to salinity, temperature, and nutrient concentrations at the selected sites in the Baltic Sea. Based on the multiple regression and multivariate statistical analysis, all cell shapes of P. minimum had highly similar distribution relative to these environmental parameters as well as chlorophyll-a, nitrite + nitrate, ammonium, total nitrogen, phosphate, total phosphorus, and silicate. The species was related positively to total nitrogen, and negatively to salinity, temperature, nitrite + nitrate, and silicate:total nitrogen ratio. The results suggest that P. minimum could well adapt to low salinity and temperature and occurred particularly in coastal waters, rich in total nitrogen relative to silicate or other inorganic nutrients. These results indicate that the recent invasion of P. minimum into the Baltic Sea could have been enhanced by the DON enrichment. The results also support the suggestion that P. minimum is one morphospecies with no distinct subtaxa.     

Effects of environmental factors on the phytoplankton community in the Gulf of Finland – unattended high frequency measurements and multivariate analyses

We studied life history and secondary production of Cheumatopsyche spp. (Trichoptera: Hydropsychidae) in StroublesCreek, a 3rd order stream near Blacksburg, Virginia to compare lifehistories and production dynamics in two reaches with differentland-uses. The upstream reach was influenced by agriculturalactivities and more annual degree-days accumulated in this sectionof the stream. The downstream reach was surrounded by forest,received less thermal input than the upstream reach, and showedlittle evidence of human disturbance. Differences between the twosites included a shift in dominant taxa and changes in voltinismand production of hydropsychids. Cheumatopsyche pettiti(Banks) was dominant at the upstream site, while C. pettitiand Cheumatopsyche oxa Ross were both abundant downstream.Cheumatopsyche larvae and other aquatic insects had higherdensities at the forested downstream site. C. pettiti wasbivoltine at the upstream site, but C. pettiti and C. oxa were partially bivoltine downstream, with a small summergeneration overlapping with continuous emergence of overwinteringlarvae. Cheumatopsyche production at the two sites inStroubles Creek was higher than in forested, low-order streams ofNorth America, but similar to some values obtained at streams inagricultural areas and large rivers. Production was higher at thedownstream site, but the superior bivoltinism at the upstream sitecounterbalanced, to some extent, the increase in larval densitythat caused higher production downstream. The adjustment in lifehistory and production dynamics, in the two reaches, showed theecological plasticity of Cheumatopsyche and the importance ofhydropsychids in the energy flow of moderately disturbedstreams.