Marine pollution

Pollution of the marine environment is, in general, one of the main issues marine conservation has to deal with. It is well-known that several pollutants cause anomalies in the immuno-supressive system and in the reproduction of marine mammals – but also of humans!

It is also known that the pollutants accumulate in each level of the food chain (actually it is a “food web”): the fish that feeds on many small fish accumulates the pollutants.

Eventually, we find the highest concentrations in the top predators (marine mammals, turtles, tuna and man, of course) along with the respective impact.

Regarding the Mediterranean monk seal, back in the 80´s pollution was among the potential causes of the population´s decline. Because of the species´ rapid decline we had to act immediately.

What we have done:

At the beginning of our projects in 1985-86, we analysed samples of sea water and fish from the area at the Ithaca channel for some particularly persistent and toxic pesticides (DDT‘s etc.) and polychlorinated biphenyls (PCB’s) in collaboration with the Bavarian State Institute for Water Research (1986/1987). Levels of PCB’s and of pesticides were in general considerably lower than in other Mediterranean areas. The concentrations in some samples were so low to be described as non-detectable. This activity was carried out on a voluntary basis by both participants.

We also analysed samples from sea water, fish, seal hair and human hair from the Ithaca channel area for heavy metals in collaboration with the Helmholtz Ιnstitut München – German Research Center for Environmental Health (1990-91). Our samples covered the entire food web with top predators being the monk seal and man: we obtained seal hair during the annual moulting of the animals and human hair from fishermen and other locals who also consume a lot of fish. In this project, as also in several other activities, the cooperation of local people from Ithaca was exemplary.

Picture: samples of human hair (fishermen from Ithaca)

Analyses were made for the toxic heavy metals mercury, lead, arsenic, cadmium and zink. The resullts showed that pollution levels were very low except for mercury in seal hair and lead in some samples of human hair.

But we did not detect the sources of this contamination since the whole project was carried out on a voluntary basis and we did not have the necessary funding for further detailed research.

Picture: samples of monk seal hair (after moulting)

In 1999, we repeated the analyses for the above heavy metals at the same Institute using samples of seawater and seal hair from Zakynthos and Southern Kefalonia. Here again, the levels of pollution were very low except for mercury in seal hair. Although this time we did have adequate funding (EU programme LIFE96NAT/GR/3225), the time left until the end of the project at the end of December 1999 did not allow us to further investigate the causes of this relatively high contamination.

Based on our results it was proved that, in general, pollution levels were rather low in the region for more than a decade, at least concerning heavy metals. Thus, marine pollution could be excluded as a main cause for the monk seal´s decline, and one would have to look upon other potential parameters (also see “Mediterranean monk seal”).

And, we may say that, according to the above results, the Ionian Sea is generally one of the cleanest seas in the Mediterranean.