Effects of sunscreen on Posidonia oceanica and its associated community of N2-fixing under different temperature levels

Abstract

[eng] The coasts of the Balearic Islands are subjected to touristic pressure, and this leads to the input of contaminating agents such as components of sunscreens. Studies related with impacts of these contaminants in marine ecosystems are limited and their effects on Posidonia oceanica are unknown. It is important to know their effects on P. oceanica because the sea grasses have several ecosystem services. In addition, the effects of components of sunscreens are also unknown on nitrogen(N2)-fixers associated to P. oceanica. The N2-fixers contribute to satisfying the needs of this phanerogam by converting atmospheric nitrogen into inorganic forms of nitrogen that the phanerogam can assimilate. Temperature could influence the response of marine species to these pollutants, so it is essential to study their effects in the context of climate change (increase in sea surface temperature). This study consisted in measuring and evaluating the effects of sunscreens on P. oceanica and its associated community of N2 fixers under different temperature levels by determining the response such as primary production, chlorophyll a, b, and total content, N2 fixation and alkaline phosphatase activity rates. Sunscreen favoured NPP at ambiental temperature. However, added sunscreen at elevated temperature decreased the chlorophyll a and total chlorophyll content. N2-fixation was not significantly different between treatments. Alkaline phosphatase activity was not high in treatment with added sunscreen, but it was at elevated temperature and without added sunscreen.