Land Uses Simplified Index (LUSI): Determining Land Pressures and Their Link With Coastal Eutrophication

18 pages, 4 figures, 7 tables, supplementary material https://doi.org/10.3389/fmars.2019.00018

Human activities on land result in the high-level production of nutrients. When these nutrients reach coastal waters, they could drive the eutrophication process. Here we present the Land Uses Simplified Index (LUSI), an easy-to-use tool for assessing continental pressures on coastal waters. This assessment is done by indirectly estimating continental nutrient loads and concentrations, and their influence on coastal waters. LUSI is based on systematic information describing both the land uses that influence coastal waters by providing nutrient-rich freshwater inflows (urban, industrial, agricultural, and riverine) and the coastline morphology, which can modify this influence, as it determines the degree of coastal water confinement and therefore the likelihood that these inflows will be diluted. A low LUSI value indicates that coastal waters are not or only slightly influenced by continental pressures and/or that these pressures are diluted. On the contrary, a high LUSI value indicates that coastal waters are strongly influenced by continental pressures and/or that these pressures are not diluted. LUSI fulfills a methodological gap, as a simple method to assess coastal pressures when there is a lack of information. Furthermore, it fulfills the requirement of the Water Framework Directive for a true pressure assessment (i.e., not confounded with impact), which for coastal waters imply using pressure data from land. An additional and important feature of LUSI is that it allows the establishment of pressure-impact relationships with impact indicators, such as those related to the Biological Quality Elements of the above Directive. For example, a relationship based on LUSI, as a proxy of pressure, and on the chlorophyll-a concentration, as a proxy of phytoplanktonic biomass and, thus, of the eutrophication impact. By providing insights into the land uses that trigger eutrophication in coastal waters, LUSI aids in the design of measures aimed at remediating anthropogenic damage caused to the environment

This study used data collected within the National Catalan Water Monitoring Program funded by contract CTN0802809 between the Catalan Water Agency (ACA) and the Marine Science Institute (ICM-CSIC). This research is a contribution to the GRADIENTS project (Estructura fina de los gradientes costeros a lo largo de la costa Mediterranea), funded by the Spanish National Program (CTM2012-39476-C02-02) and the DEVOTES project (Development of innovative tools for understanding marine biodiversity, and assessing good environmental status), funded by the European Union's Seventh Framework Programme for research, technological development, and demonstration under grant agreement number 308392

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