Estuaries are highly appropriate systems for evaluating contamination. They are areas of accumulation of sediments and, effectively, numerous contaminants are found associated with these sedimentary particles. For a comprehensive evaluation, it is important to undertake studies on the effects of the contaminants in the environment; the toxicity trials enabling the quantification of such effects. These trials involve exposing organisms to sediments suspected of being contaminated, in order to quantify any biological response from the organism in relation to its toxicity.
As a researcher at Azti-Tecnalia technological centre, Iratxe Menchaca undertook biotrials with sea urchins (Paracentrotus lividus) at their embryonic stages. This involved quantifying what percentage of larvae suffer abnormal growth after being exposed to the sediments under study, and undertaken as a measure complementary to other trials, with the goal of obtaining a comprehensive evaluation of contamination. Ms Menchaca's PhD, defended at the University of the Basque Country (UPV/EHU), shows precisely that the embryogenesis of the sea urchins is a useful toxicological indicator. The work is entitled Development and application of tools for the evaluation of the quality of the marine environment of the Basque Country: biotrials with Paracentrotus lividus and Corophium spp.
Studies of the river Oiartzun
In her thesis Ms Menchaca records a case study undertaken at the estuary of the river Oiartzun (in the Basque province of Gipuzkoa) in which, amongst other things, the mentioned embryonic biotrials on sea urchins were undertaken. The study showed that the interior zone of the estuary showed greater concentrations of contaminants, as well as a higher degree of alteration of benthos (the organisms living on the seabed), a greater risk of affecting the environment and high toxicity. This toxicity is linked, concretely, with the content of organic material and ammonium and with PAHs (polycyclical aromatic hydrocarbons) found in the zone.
Based on these results, the researcher concluded that the embryonic biotrials on sea urchins are a sensitive and useful tool for the evaluation of the environmental impact of human activity in the marine environment.
Availability of gametes
Another aspect analysed by Ms Menchaca was the availability of sea urchin gametes along the Basque coast, to which end two populations were studied; one in Donostia-San Sebastián and the other in Zumaia, further west along the Basque Riviera. The sea urchins in both populations showed a single spawning event at the end of winter or the beginning of spring. The Donostia-San Sebastián population proved suitable for the supply of gametes throughout the year (albeit with seasonal differences in their availability), but that of Zumaia showed greater limitations.
In the periods when sexually developed sea urchins are scarce in their natural environment, the process can be accelerated in the laboratory and gametes obtained out of their natural period. The results obtained in this thesis point to commencing their introduction on finalising the period of natural spawning; the best results having been obtained 60 days after finishing the reproductive cycle.
In her thesis, Ms Menchaca also studied the possibility of using and/or cultivating certain marine amphipods in the laboratory with the goal of not having to depend on the natural population and as a complement to the trials with the sea urchins, concretely with Corophium multisetosum and Corophium urdaibaiense. While pointing out that it was necessary to undertake more experiments with both species in order to optimise their production, Ms Menchaca has shown that it is possible to maintain and cultivate these amphipods in the laboratory over months. Taking into account the differences between both as regards their habitats, Ms Menchaca concluded that C. multisetosum is the more suitable of the two for evaluating confined zones, as are ports and certain irrigation channels.
About the author of the thesis
Ms Iratxe Menchaca Cortazar (Bilbao, 1981) is a graduate and doctor in Biological Sciences. She undertook her PhD thesis under the direction of Javier Franco San Sebastián and Joxe Mikel Garmendia Etxandi, both researchers at Azti-Tecnalia, and she defended it in the Department of Zoology and Animal Cell Biology at the Science and Technology Faculty of the UPV/EHU. She carried out her research at Azti-Tecnalia, but also spent time at the University of Vigo (Galicia). Ms Menchaca is currently a researcher at the Marine Research Unit at Azti-Tecnalia.
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