Toxicity of fatty acid 18:5n3 from Gymnodinium cf. mikimotoi: II. Intracellular pH and K+ uptake in isolated trout hepatocytes.

Effects of octadecapentaenoic acid 18:5n3 and other related polyunsaturated fatty acids present in gymnodinium cf. mikimotoi were tested in isolated trout hepatocytes. These exotoxins decreased intracellular pH followed by a slow recovery to initial value and alkalinization of acidic compartments, suggesting an inhibition of vacuolar H(+)-ATPases. Moreover, addition of 18:5n3 to the extracellular medium induced a decrease of K+ uptake into hepatocytes as a result of Na,K-ATPase inhibition. However, high concentrations (10(-5)-10(-3) M) are necessary to induce these effects.

Toxicity of fatty acid 18:5n3 from Gymnodinium cf. mikimotoi: I. Morphological and biochemical aspects on Dicentrarchus labrax gills and intestine.

We present evidence for the toxic effects of fatty acid 18:5n3 (octadecapentaenoic acid) in the gills and intestine of the sea bass Dicentrarchus labrax. Light microscopic observation of gills showed strong mucus production and alteration of ionocytes. The Mg- and Na,K-ATPase activities were inhibited, with IC50 values of 10(-3) and 1.6 x 10(-4) M, respectively. Results are discussed in relation to osmoregulation.

Haemolytic glycoglycerolipids from Gymnodinium species.

Glycoglycerolipids derived from microalgae can be a source of biologically active substances including toxins. Such glycolipids were analysed in two isolates of toxic marine dinoflagellates from European waters. The lipids of Gymnodinium mikimotoi contained 17% of monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG), while in Gymnodinium sp. the proportion was 35%. MGDG and DGDG from both species were haemolytic. The major unsaturated fatty acid in both algal glycolipids was 18:5 omega 3.

[Evolution of hydrocarbons and bacterial activity in the marine sediments contaminated by crude oil overflow and treated]. / Evolution des hydrocarbures et de l'activité bactérienne dans des sédiments marins contaminés par un déversement de pétrole brut et traité.

The fate of an experimental oil pollution of intertidal sediments in a sheltered beach of North Brittany (France) has been investigated over a 16-month period. Chemical treatments were applied to two of the three contaminated plots by pre-mixing oil respectively with dispersant and biodegrading agents. The physico-chemical and bacteriological characteristics of the polluted areas were followed with the purpose of identifying the limiting parameters for oil microbial degradation and the effect of treatment. The concentration of hydrocarbons in the oiled sediments did not change significantly during the experimental period. Spectrofluorimetric and chromatographic data showed that the main evolution of oil concerns the degradation of n-alkanes and the removal of light aromatics. Biodegradation of hydrocarbons occurred at a measurable rate only during the warm seasons (average temperature 18 +/- 2 degrees C) causing after sixteen months the disappearance of more than 80% of the n-alkanes fraction independently of the pollution sediment level and the chemical treatment of the experimental plots. However, the biodegradation of n-alkanes proceeded during the first months, at different rates, inversely depending on oil content in the collected samples. The main limiting factor is dissolved oxygen according to the fact that spilled oil was located at 3-5 cm depth in a poorly oxygenated zone characterized by low redox potential. Nutrients were not a limiting factor probably due to domestic and agricultural inputs in this area. A marked bacterial growth was observed two weeks after the oil spill with a relative increase in hydrocarbon degrading bacteria with respect to total heterotrophs. Degradation rates, based on C14 n-hexadecane experiments, seem to follow the same way than specific bacterial counts (plate technique). Specific bacteria are always high at the end of our 16 months' field experimentation. In the laboratory as well as in the field experiments, the same behaviour of untreated and chemically treated oil was observed in partially anaerobic sediment.