Mare Nostrum

One of the reasons for our undertaking this trip was that the Mediterranean is a marine biodiversity “hot spot”, a rich ‘world’ that needs to be protected.Despite its small size, the Mediterranean Sea possesses a very impressive level of biodiversity. There are many different species here, some 10% of the world’s as yet known total. And 25% of these Mediterranean species are endemic, i.e., they only live in this zone. As a basin where numerous human civilisations emerged, the Mediterranean has nonetheless fallen victim to strong anthropic pressures (the impacts of Mankind on Nature), given that hundreds of millions of inhabitants live round its shores.

Mare Nostrum

Over the past few decades, observed on Spanish, French and Italian coastlines there has been an algae bloom, i.e., a very rapid proliferation that had never been observed before in this Sea. Related to the bloom, there have been cases of human intoxication and high mortality rates in marine invertebrates.
Following analysis and identification, we are faced here with an invasive algae of tropical origin: dino-flagellates (micro-organisms with flagella) of the Ostreoposis family This is a microscopic species that develops on a substrate (benthic), other sea-plants or sea-weed in general and in the summer time when the local water conditions are favourable. Development us such that the algae create patches visible on the water surface [NR-there is practically no tide in the Mediterranean]. As is the case for many other tropical algae, Ostreopsis is toxic: the toxins are released into the surrounding water and can take the form of gas clouds drifting over the nearby beaches.

The species is not in fact fatal for mankind but the impact of Ostreopsis on the environment does call for studies if only to better understand the mechanisms. When a species invades a given zone, it implies a change in the local eco-system, all the more striking if the invader uses toxic molecules to gain territories. This rapid development of Ostreopsis has led to a drop in water quality and in occasionally to large-scale mortality of marine organisms, such as sea-urchins and mussels. Moreover, the toxins can accumulate in the food chain.

Our trip along the Mediterranean coastline and the fact that we chose to do it in the summertime turned out perfect for us to participate in a study of these algae in collaboration with the Villefranche-sur-Mer Oceanological Observatory Laborarory (LOV) cf. [in English]. As soon as possible, we shall take samples of the substrates, for later study at the Observatory.
The samples will reveal the presence or not of Ostreopsis and will contribute to understanding the dynamic nature of propagation, e.g., will the extension continue geographically or will it be restricted to certain specific zones? Moreover, we shall photograph the substrates to see if Ostreopsis develops preferentially on certain sea-weeds rather than others. With our collection of cells, a DNA analysis will enable comparison of sources and this again will teach us more about the dynamics of the species.

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