http://pubs.acs.org/doi/full/10.1021/es202351y
Jacob Carstensen,*,† María Sanchez-Camacho,‡ Carlos M. Duarte,‡,§ Dorte Krause-Jensen,† and Nuria Marba‡
†Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
‡Department of Global Change Research, IMEDEA (CSIC-UIB), Instituto Mediterraneo de Estudios Avanzados, Miquel Marques 21,
07190 Esporles (Illes Balears), Spain
§The UWA Oceans Institute, University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia
ABSTRACT: Empirical relationships between phytoplankton biomass and nutrient concentrations established across a wide range of different ecosystems constitute fundamental quantitative tools for predicting effects of nutrient management plans. Nutrient management plans based on such relationships, mostly established over trends of increasing rather than decreasing nutrient concentrations, assume full reversibility of coastal eutrophication. Monitoring data from 28 ecosystems located in four well-studied regions were analyzed to study the generality of chlorophyll a versus nutrient relationships and their
applicability for ecosystem management. We demonstrate significant differences across regions as well as between specific coastal ecosystems within regions in the response of chlorophyll a to changing nitrogen concentrations. We also show that the chlorophyll a versus nitrogen relationships over time constitute convoluted trajectories rather than simple unique relationships. The ratio of
chlorophyll a to total nitrogen almost doubled over the last 3040 years across all regions. The uniformity of these trends, or shifting baselines, suggest they may result from large-scale changes, possibly associated with global climate change and increasing human stress on coastal ecosystems. Ecosystem management must, therefore, develop adaptation strategies to face shifting baselines and maintain ecosystem services at a sustainable level rather than striving to restore an ecosystem state of the past.