Recovery of lakes and coastal marine ecosystems from eutrophication: A global meta‐analysis

Abstract

In order to inform policies aimed at reducing nutrient emissions to surface waters, it is essential to understand how aquatic ecosystems respond to eutrophication management. Using data from 89 studies worldwide, we examined responses to the reduction or cessation of anthropogenic nutrient inputs relative to baseline conditions. Baseline conditions were pre-disturbance conditions, undisturbed reference sites, restoration targets, or experimental controls. We estimated recovery completeness (% baseline conditions reached) and recovery rate (annual % change relative to baseline conditions) for plant and animal abundance and diversity and for ecosystem functions. Categories were considered fully recovered if the 95% confidence interval (CI) of recovery completeness overlapped 100% and partially recovered if the CI did not overlap either 100% or zero. Cessation of nutrient inputs did not result in more complete or faster recovery than partial nutrient reductions, due likely to insufficient passage of time, nutrients from other sources, or shifting baselines. Together, lakes and coastal marine areas achieved 34% (616% CI) and 24% (615% CI) of baseline conditions decades after the cessation or partial reduction of nutrients, respectively. One third of individual response variables showed no change or worsened conditions, suggesting that achieving baseline conditions may not be possible in all cases. Implied recovery times after cessation of nutrient inputs varied widely, from < 1 yr to nearly a century, depending on response. Our results suggest that long-term monitoring is needed to better understand recovery timescales and trajectories and that policy measures must consider the potential for slow and partial recovery.

Nutrients, eutrophication and harmful algal blooms along the freshwater to marine continuum

“…In their review of 89 control efforts McCrackin et al () did not find any significant differences in success from efforts to control P, N, or N + P, but variability was high, and few management programs have attempted to control N alone. Nevertheless, dual N and P control is beginning to be implemented with some success, either in experimental situations, or in entire systems (Baker et al, ; Elmgren & Larsson, ; McCrackin et al, ; Shatwell & Köhler, ). Agencies in the U.S. and Europe are drafting regulations to enforce dual nutrient control (EPA, ; Ferreira et al, ).…”

Fewer blue lakes and more murky lakes across the continental U.S.: Implications for planktonic food webs

“…Resistance to recovery may be related to ongoing internal loading of phosphorus from lake sediments caused by anoxic conditions in the hypolimnion. The latter is often exacerbated by lake greening and browning (Solomon et al 2015;Williamson et al 2015;McCrackin et al 2017).…”

Unexpected stasis in a changing world: Lake nutrient and chlorophyll trends since 1990

“…Climate change is likely to exacerbate eutrophication of surface waters (Moss et al, 2011). Even when nutrient sources are partially or completely removed, recovery of lakes after nutrient reductions is highly variable and can take years to decades (McCrackin, Jones, Jones, & Moreno-Mateos, 2017), highlighting the importance of long-term efforts that monitor water quality. In the Midwest and Northeast United States, lakes are facing drivers acting to both improve and degrade water quality, and as such, have remained relatively unchanged in the last 20 years in regards to nutrients and chlorophyll.…”