MAP Technical Reports Series No. 106 UNEP

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phytoplankton extracts it has been possible to demonstrate the absence of biotoxins with acute
ichthyotoxic effects during the "green tide" produced by Gymnodinium corii along the coast of
Emilia-Romagna during 1976 (Viviani, 1977a). Water with blooms of Prorocentrum micans
(Viviani, 1977a) and of Gonyaulax polyedra (Viviani et al., 1985) has also been demonstrated
to be non-toxic.
Haemolysis test
The first studies on haemolytic and cytotoxic effect of ichthyotoxins and the analysis
of toxic components are those of Israeli research workers (Shilo, 1967). It has been shown that
the relationship between the different toxic activities can vary with different growth conditions of
the Prymnesium parvum and that some of the haemolytic activity can be selectively removed
from the phytoflagellate preparations by absorption on erythrocytes. Particularly interesting is the
differential inactivation of the various toxic activities by alkalis and light. Although alkali rapidly
inactivates the haemolysin which acts at 35EC, a haemolysin active at 8EC is only mildly
affected (Shilo, 1967).
Polyunsaturated C 18 and C 20 fatty acids analysis
In the Mediterranean sea, instances of fish kill due to glycolipids and unsaturated fatty
acids of phytoplancton origin have not yet been described. Previous research did however show
that in the Adriatic there are phytoplankton which synthesize the fatty acid C 18:4 which,
according to present knowledge has ichthyotoxic and haemolytic properties. Indeed, in the
stomach contents of Clupea sprattus the presence of this fatty acid was demonstrated in the
field of research on the relationship between fatty acids contained in diatoms and dinoflagellates,
and their presence in the tissues of plankton-feeding fish in the Adriatic sea (Viviani et al., 1968).
When discoloured water, red tide or mucilaginous aggregates occur in a health and
environmental monitoring programme for the presence of ichthyotoxic substances it is
necessary to analyze by gas-chromatographic methods the fatty acids of total lipids not only in
marine waters, but also in mussels and in the stomach contents and tissues of plankton-feeding
fish.
Significant levels of the polyunsaturated fatty acids C 18:4, C 18:5, C 20:5 could be the
first screen before haemolysis tests, chromatographic and mass spectral data.
6.2 Damage to communities and the ecosystem by harmful algal blooms
The dystrophic effects which occur in the Mediterranean after eutrophication are
generally caused by oxygen deficiencies in the bottom waters. A detailed description of the
cases reported is given in chapter 5, but it is worth drawing attention to the North Adriatic, where
the regular occurrence of widespread, persistent oxygen shortages has led to profound
modifications in the benthic communities and ecosystem.
These modifications have been highlighted by research carried out in the Gulf of Trieste
(Stachowitsch, 1984) and in the North-West Adriatic off the coast of Emilia-Romagna (Crema
et al., 1991; Rinaldi et al., 1993).
Laboratory research into the effects of oxygen deficiency has been performed using
bivalves typical of the Northern Adriatic (De Zwaan et al., 1992).