Effective Management of Closed Hypereutrophic Estuaries Requires Catchment-Scale Interventions

作者：Daniel A. Lemley, SJ Lamberth, Warren Manuel, Monique Nunes, Gavin M. Rishworth, Lara Van Niekerk, Janine B. Adams · 发表于：Frontiers in Marine Science · 年份：2021 · DOI：10.3389/fmars.2021.688933 · 被引用次数：27 · 研究领域：Aquatic Ecosystems and Phytoplankton Dynamics、Marine and coastal ecosystems、Marine Biology and Ecology Research

Increased nutrient loading associated with rapid population growth is the leading cause of deteriorating water quality in urbanized estuaries globally. Small estuaries are particularly sensitive to changes when connection with the marine environment is restricted, or lost, because of high water retention. The temporarily closed Hartenbos Estuary (South Africa) is an example of how such pressures can culminate in a severely degraded ecosystem. Wastewater treatment work (WWTW) discharges introduce substantial volumes of freshwater (8,000 m 3 d –1 ) and nutrient loads (38 kg DIN d –1 and 22 kg DIP d –1 ) into this estuary. This constant inflow has necessitated frequent artificial breaching (inducing alternating states) of the estuary mouth to prevent flooding of low-lying developments and, occasionally, to mitigate against extreme events such as fish kills and sewage spills. This study investigated the efficacy of artificial mouth breaching practices in eliciting responses in selected abiotic and biotic parameters. Microalgal (phytoplankton and benthic diatoms), benthic macrofauna and fish community dynamics were assessed in response to mouth state and water quality conditions using a seasonal monitoring programme. The hypereutrophic nature of the Hartenbos Estuary was highlighted by persistent high-biomass phytoplankton accumulations (>100 μg Chl- a l –1 ), extreme dissolved oxygen conditions (0.4–20.5 mg O 2 l –1 ) and the predominance of harmful algal bloom (HAB) event...