Macroalgae transplant to detect the occurrence of anthropogenic nutrients in seawater of highly tourist beaches in Mediterranean islands

Abstract

In the Mediterranean region, islands are among the most important tourist destinations, being sites of considerable naturalistic, historical and cultural importance. This is highly beneficial for local economies, but may also represent a threat for the environment, especially during the peak season (i.e. summer). Indeed, the sharp demographic increase concentrated in a relatively short period may negatively affect the quality of coastal marine systems and the provision of ecosystem services, producing in turn negative feedbacks on tourism industry. Nevertheless, the assessment of the environmental impact of tourism on coastal seawater has been seldom addressed. Here, we show the results of the biomonitoring approach adopted in the tourist Island of Rhodes (Greece), in the context of the Interreg Med BLUEISLANDS project. The study involved short-term macroalgae transplantation and incubation, and, through the analysis of nitrogen stable isotopes, provided a time-integrated picture of the occurrence of anthropogenic nutrients, which are indicators of water quality and might be missed by routine water quality monitoring programs. Main findings ruled out a marked input of anthropogenic nutrients potentially threatening the functioning of coastal ecosystems and highlighted overall good environmental conditions. In addition, this approach provided spatial data useful to produce GIS maps, useful tools that may help the decisional process of policy-makers, for adopting management practices to mitigate the environmental impact and foster sustainable tourism.