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News article13 October 2017

Assessing the causes of coastal eutrophication

© Fotolia, Author: Alexey Stiop

Eutrophication and its detrimental effects on coastal ecosystems is one of the biggest issues in many regions of the world. Human activities and climatic change are the most important drivers of eutrophication, leading to harmful algal blooms and the proliferation of hypoxic conditions in many coastal ecosystems.

Europe and its regional seas are no exception. Evidence of eutrophication is found in many regions of its different basins, from the Baltic to the Black Seas. Rivers are among the most important drivers of eutrophication, as they influence coastal ecosystem dynamics through freshwater flow and the transport of nutrients and organic matter. Hence, it is fundamentally important to understand how the freshwater-marine link works in order to establish appropriate measures to maintain (or recover) the good environmental status (GES)* of European marine ecosystems.

In a recently published article, JRC scientists used the Marine Modelling Framework (MMF) to assess the causes of observed productivity patterns in different regions of the northern Mediterranean coast, where phytoplankton blooms and hypoxic conditions could hamper achieving the GES. By performing a series of simulations covering the past 50 years (from 1960 to 2010) using different river conditions (manipulating the level of inorganic nutrients in the freshwater) it was possible to establish the causes of the algal blooms and oxygen deficit in the different regions.

For the Adriatic Sea, phosphate levels in the main rivers (mainly the Po) seem to be the major drivers of pelagic primary production and the development of hypoxic zones, while for the Aegean Sea it seems that the nitrate concentration in the rivers is the most relevant parameter. On the contrary, for the Gulf of Lion, nutrient levels in the rivers’ waters do not significantly impact the coastal marine ecosystems properties, as the oceanographic process drives most of the upper water fertilization and, hence, primary production.

What this work shows is that the measures to be taken in order to minimize the consequences of eutrophication in marine ecosystems are region-specific, and that the MMF developed at the JRC could help stakeholders and policymakers define and prioritize programmes of measures.

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Publication date
13 October 2017