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An UMU article published in the Journal of Experimental Biology evaluates the effects of the combination of salinity and desiccation as stress factors in two species of aquatic beetles.
The main novelty of this study is that it investigates the combined effects of two stress factors (salinity and desiccation) simultaneously, intensified as a consequence of climate change.
Specifically, they are two beetles typical of ramblas and saline streams of the Iberian southeast: Enochrus jesusarribasi (Hydrophilidae) and Nebrioporus baeticus (Dytiscidae).
Also, the studied environments are unique, and are threatened by human activities and aridification associated with climate change.
This will mean an increase in the temporality and salinity of water in many of our rivers and wetlands.
To this end, Susana Pallarés, a graduate in Environmental Sciences and a doctor from the University of Murcia, the main author of the study, explains the methodology applied: "Individuals of the two species were exposed in the laboratory at high salinity to measure a series of physiological responses (survival, water loss and ionic concentration of internal fluids) during a post-drying exposure, and in another set of experiments the opposite sequence was made, exposure first to desiccation and then to salinity. "
The response found in the first case is known as 'crossed tolerance': exposure to stress, salinity, favors resistance to other stress, desiccation.
On the other hand, when the first stress factor is desiccation, tolerance to salinity decreases.
In other words, the answers depend on the order of exposure to the factors, showing that the combined effects of several stress factors are much more complex than their isolated effects. The species studied are able to tolerate very high salinities since they have very efficient physiological mechanisms for excrete salts and conserve water, which can be beneficial when they are subsequently exposed to moderate desiccation.
On the other hand, the desiccation is a much more extreme stress for these aquatic organisms, which entails a loss of water and an increase in the ionic concentration of the internal fluids very fast.
This can impede the correct functioning of the ionic regulation mechanisms, explaining the response found when individuals are first exposed to desiccation and then to salinity.
The environmentalist emphasizes that since the effects of climate change on Mediterranean continental aquatic ecosystems will be precisely an increase in aridity and salinity, it is essential to know the response mechanisms against these factors to predict the impact of climate change on biodiversity. aquatic
In addition, this "multi-stress" approach is necessary to detect "responses that are difficult to predict when evaluating a single factor, because they are not additive effects, but synergistic or antagonistic," clarifies the researcher. The study has been carried out by the members of the Aquatic Ecology research group: Susana Pallarés, María Botella-Cruz, Paula Arribas, Andrés Millán and Josefa Velasco. Full article: Pallarés, S., Botella-Cruz, M., Arribas, P., Millán, A. & Velasco, J. Aquatic insects in a multistress environment: cross-tolerance to salinity and desiccation.
Journal of Experimental Biology, 220: 1277-1286.
Source: Universidad de Murcia
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