Impact of temperature and species interaction on filamentous cyanobacteria may be more important than salinity and increased pCO2 levels

A future business-as-usual scenario (A1FI) was tested on two bloom-forming cyanobacteria of the Baltic Proper, Nodularia spumigena and Aphanizomenon sp., growing separately and together. The projected scenario was tested in two laboratory experiments where (a) interactive effects of increased temperature and decreased salinity and (b) interactive effects of increased temperature and elevated levels of pCO2 were tested. Increased temperature, from 12 to 16 °C, had a positive effect on the biovolume and photosynthetic activity (F v/F m) of both species. Compared when growing separately, the biovolume of each species was lower when grown together. Decreased salinity, from 7 to 4, and elevated levels of pCO2, from 380 to 960 ppm, had no effect on the biovolume, but on F v/F m of N. spumigena with higher F v/F m in salinity 7. Our results suggest that the projected A1FI scenario might be beneficial for the two species dominating the extensive summer blooms in the Baltic Proper. However, our results further stress the importance of studying interactions between species.

Migration forms of hydrocarbons in waters and bottom sediments of the Gulf of Riga

It is found that hydrocarbons are constantly accumulated on the main geochemical barriers: water-atmosphere, river-sea, water-suspended matter, and water-bottom sediment interfaces. Degree of hydrocarbon accumulation reaches 13.5-17.6 in the surface microlayer and exceeds 1000 in bottom sediments. Hydrocarbon composition changes in this process. Local pollutant loads result in accumulation of polycyclic aromatic hydrocarbons by bottom sediments and benzo(a)pyrene concentration sometimes exceeds MPC. Content of hydrocarbon migratory forms is calculated.