Researching how stress factors affect the synthesis of fatty acids in aquatic species
Cristina G. Pedraz/DICYT A group of scientists from the Marine and Environmental Science Centre (MARE), a joint centre of six Portuguese universities including that of Coimbra, and of the Marine and Environmental Studies Centre (Centro de Estudios Ambientales y Marinos, CESAM) of the University of Aveiro are researching the effect of stress factors (both environmental and anthropogenic) on the biochemical processes of aquatic species throughout the food chain. This allows the extrapolation of the impact on the food chains and on the food quality of some species. Some of these species have a high economic value as they are used for human food.
As is pointed out by one of the researchers, Ana Marta Gonçalves, global change is largely due to man's activities and may affect aquatic communities and therefore the ecosystems and resources they contain.
“In recent decades there has been an intense exploration of agricultural land, mainly in the countries of the Mediterranean region, which has given rise to an excessive use of fertilisers and pesticides that have adverse effects on the aquatic systems in the surrounding areas and their biological communities”, the researcher explains. In some cases the use of these products exceeds the limits established by the European Union, which leads to the application of surveillance programmes such as that implemented on the estuary of the River Mondego (in the Figueira da Foz area in Portugal).
“This estuary system, together with other coastal systems near agricultural areas, is subjected to the waste from the surrounding areas, which could endanger aquatic communities. It is therefore important to find out the effects of these stress factors not only on the parameters of the population of the species (for example reproduction, the number of descendants, and the growth stage) but also on metabolism, for instance in the synthesis of fatty acids (FA), which are very sensitive to pollution and environmental factors”, she adds.
Ana Marta Gonçalves points out that there are several groups of fatty acids, including the so-called essential fatty acids (EFA) such as the omega-3 and omega-6 fatty acids present in fish, which are mainly obtained through human food (some organisms are capable of synthesising them, albeit in very low quantities, with the energy used in this production not being compensated). They are essential in the prevention and treatment of certain diseases, such as some types of cancer, cardiovascular diseases, and autoimmune diseases. “It is therefore essential to understand how stress factors affect these organisms at the base of the food chain, as their impact can be observed throughout the chain and in the last instance human beings are also affected”, she emphasises.
Differences in the synthesis of fatty acids
The research group of the MARE and CESAM centres is studying various species from different trophic levels: microalgae, macrophytes, zooplankton, benthos, and both saltwater and freshwater fish so as to understand how the synthesis of fatty acids is affected throughout the food chain and whether there are differences between the reactions of saltwater and freshwater species.
Work has been going on for several years on these species from different trophic levels, exposing them to stress conditions (both natural and anthropogenic) with either a single stress factor or a combination. “The development of the experimental design of any experiment of this kind requires a great deal of time and also the acclimatisation of these species to laboratory conditions”, she points out.
The results obtained to date “are very interesting because they reveal that the species studied show a significant reduction in their fatty acid profiles in the presence of certain stress factors, owing to which they are less nutritious than the organisms we use as a control”. Moreover, some species “manage to recover within certain limits and to return to their initial state after being exposed to stress factors”, the researcher explains.
Climatic change, a factor to be taken into account
The stress factors that may condition the synthesis of fatty acids in the food chain of these aquatic species include climatic change. According to the scientist of the MARE and the CESAM, “fatty acid molecules are very sensitive to pollution and environmental factors. A reduction in the synthesis of fatty acids (in particular of essential fatty acids) may trigger changes in the profile or only in the abundance of fatty acids to make the species less nutritious. On the other hand, it is known that bodies also reduce their metabolic functions to lower their demand for energy when they are subjected to stress”.
Nevertheless, there is still time to mitigate the effects of climatic change in these aquatic species, but in order to do so we need “the support of the government and of society itself to minimise the anthropogenic actions that largely cause global change” and also “the establishing of new limits for the use of pollutants that do not interfere with the metabolic synthesis of organisms and therefore with their nutritional value”. For this reason, one of the next steps in this line of research will be the establishing of extreme parameters as from toxicological models.
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|Neves, M., Castro, B. B., Vidal, T., Vieira, R., Marques, J. C., Coutinho, J. A. P., Gonçalves, F., Gonçalves, A. M. M. (2015). “Biochemical and populational responses of an aquatic bioindicator species, Daphnia longispina, to a commercial formulation of a herbicide (Primextra® Gold TZ) and its active ingredient (S-metolachlor)”. Ecological Indicators. (DOI: 10.1016/j.ecolind.2015.01.031)|