Abstract
After a local wastewater treatment plant significantly reduced phosphorus loading into a phytoplankton-dominated tributary of the Potomac River in the early 1980s, water quality and biological communities were monitored bi-weekly from April to September. After a 10-year time-lag, submerged aquatic vegetation (SAV), once abundant in this freshwater tidal embayment, returned to the area in 1993. After additional reductions in nitrogen load starting in 2000, the system switched to an SAV-dominated state in 2005. Fish abundance did not change during these distinct phase changes, but the fish community structure did. Increases in SAV provided refuge and additional spawning substrate for species with adhesive eggs such as Banded Killifish (Fundulus diaphanus), which is now the most abundant species in the embayment. Other changes observed were a decrease in the relative contribution of open water dwelling species such as White Perch (Morone americana), and an increase of visual predators such as Largemouth Bass (Micropterus salmoides). The 30-year record of data from this Potomac River tributary has revealed important long-term trends that validate the effectiveness of initiatives to reduce excess nutrient inputs, and will aid in the continued management of the watershed and point-source inputs.
Highlights
Estuarine and tidal freshwater ecosystems are often sites that receive treated wastewater, which has historically resulted in the eutrophication of many valuable habitat areas [1]
This study looks into the effects of stepwise changes in submerged aquatic vegetation (SAV) cover on the local fish community over the period of 1985–2011 that took place in Gunston Cove, Virginia, which is an embayment of the Potomac River
Decrease in point-source nutrient loading into a Potomac River tributary resulted in classic [18]
Summary
Estuarine and tidal freshwater ecosystems are often sites that receive treated wastewater, which has historically resulted in the eutrophication of many valuable habitat areas [1]. In Gunston Cove, a small tributary of the Potomac River, the changes in SAV cover were not gradual, and exhibited clear ‘tipping points’ at two times during the recovery, during which a small increase in water clarity resulted in rapid expansion of SAV [10]. These re-emerged SAV beds potentially created new habitat areas for fish at different stages of their life history [5,9].
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