Coastal eutrophication research: a new awareness

Abstract

An analysis of the contents and conclusions of the papers contained in this issue (Hydrobiologia Volume xxx) suggests that a new vision is taking shape that may correspond to an emerging new paradigm in the way we understand and manage coastal eutrophication. This new paradigm emphasizes its global dimension and the connections with other global environmental pressures, and re-evaluates the targets of remedial actions and policies. Eutrophication research must evolve toward a more integrative, ecosystem perspective which requires that it be extended to include impacts beyond primary producers and to examine possible cascading effects and feedbacks involving other components of the ecosystem. A quantitative framework that incorporates the interacting top-down and bottom-up effects in eutrophication models must be urgently developed to guide diagnostics and establish targets to mitigate coastal eutrophication. The required macroscopic view must also be extended to the managerial and policy frameworks addressing eutrophication, through the development of policies that examine activities in the environment in an integrative, rather than sectorial, manner. Recent evidence of complex responses of coastal ecosystems to nutrient reduction requires that management targets, and the policies that support them, be reconsidered to recognize the complexities of the responses of coastal ecosystems to reduced nutrient inputs, including non-linear responses and associated thresholds. While a predictive framework for the complex trajectories of coastal ecosystems subject to changes in nutrient inputs is being developed, the assessment of managerial actions should be reconsidered to focus on the consideration of the status achieved as the outcome of nutrient reduction plans against that possibly derived from a 'do nothing' scenario. A proper assessment of eutrophication and the efforts to mitigate it also requires that eutrophication be considered as a component of global change, in addressing both its causes and its consequences, and that the feedbacks between other components of global change (e.g., climate change, overfishing, altered biogeochemical cycles, etc.) be explicitly considered in designing eutrophication research and in managing the problem.

The meagre future of benthic fauna in a coastal sea—Benthic responses to recovery from eutrophication in a changing climate

“…Although recovery trajectories from eutrophication do not necessarily mirror the past changes (Duarte, ), the present results strongly suggest that the ‘biomass lost’ due to hypoxia is only a small fraction of the biomass gained in oxic areas during the past eutrophication of the Baltic Sea. However, eutrophication and associated hypoxia have changed the depth distribution and community composition of macrofauna, which has probably had major consequences throughout the ecosystem, for example on the physiological status and community composition of bottom‐feeding fish (Karlson et al, ; Pihl, ).…”

Long-Term Dynamic in Nutrients, Chlorophyll a, and Water Quality Parameters in a Coastal Lagoon During a Process of Eutrophication for Decades, a Sudden Break and a Relatively Rapid Recovery

“…Negative ecological and socioeconomic effects of eutrophication have been well known for a long time (Vollenweider, 1968;Vollenweider and Kerekes, 1981;United States Environmental Protection Agency [USEPA], 2001;Bricker et al, 2003;Smith, 2003;Jessen et al, 2015), and the concern for their consequences is increasing (Ménesguen and Lacroix, 2018). Moreover, recovery from an eutrophication process is usually difficult and long, and trajectories of impacted ecosystems tend not to be directly reversible, failing to return to the reference status even upon nutrient reduction (Duarte et al, 2008(Duarte et al, , 2013Duarte, 2009;Carstensen et al, 2011;McCrackin et al, 2016). In the Mar Menor, the process of eutrophication has shown three well-defined phases of very different duration that we have been able to observe and characterize (Figure 10).…”

Getting the measure of eutrophication in the Baltic Sea: towards improved assessment principles and methods

“…Often the functional relations are complicated, including issues like thresholds, regime shifts and climate change Duarte 2009). The implications for management are currently being understood and interpreted.…”