Nutrients and Phytoplankton in a Shallow, Hypereutrophic Urban Lake: Prospects for Restoration

Abstract

University Lake, a shallow, artificial, urban lake adjacent to the campus of Louisiana State University, has a long history of water quality problems, including algal blooms, fish kills, and high concentrations of fecal indicator bacteria. Periodic dredging of the lake is necessary to prevent its return to swampland. This study was undertaken to elucidate the roles of allochthonous versus autochthonous nutrients as causes of water quality problems in the lake, with the expectation that this information would help identify strategies for lake restoration. Photosynthetic rates and concentrations of inorganic nutrients and phytoplankton pigments were measured over a period of one year. More than 90% of the chlorophyll a (chl a) in the lake was accounted for by Chlorophyceae, Cyanophyceae, and Bacillariophyceae. Concentrations of chl a, which averaged 75 µg L −1 , fluctuated weekly during dry weather by as much as a factor of four. Phytoplankton growth rates were about 30% higher 1-2 days after rain events than after periods of dry weather, the implication being that allochthonous nutrient loading has a significant effect on the dynamics of the phytoplankton community in the lake. Therefore, dredging of sediments will likely produce no long-term improvement in water quality. More than 100 storm drains currently discharge into the lake, and diversion of those drains may be the most cost-effective strategy for effecting a long-term improvement in water quality.

Active DNRA and denitrification in oxic hypereutrophic waters

“…Since the conditions found in the studied lagoon (e.g. chlorophyll a concentrations) are similar to those found in other hypereutrophic systems ( Bigham et al, 2009 ;Norris and Laws 2017 ;Paerl et al, 2011 ;Xing et al, 2005 ), we argue that our findings of active DNRA in oxic waters are relevant for a large number of aquatic systems worldwide. Enhanced water column DNRA might lower the capacity for these ecosystems to provide services such as water filtration, carbon sequestration, and fish supplies.…”

“…Furthermore, our measured chlorophyll a values are in the same range as those reported for other hypereutrophic waters in, e.g. Asia ( Paerl et al, 2011 ;Xing et al, 2005 ) and North America ( Bigham et al, 2009 ;Norris and Laws 2017 ). Thus, our findings of active NO 3 − reduction in oxic waters are relevant for a large number of aquatic systems worldwide.…”

Spatio-temporal Assessment of Phytoplankton and Physicochemical Parameters of Dangana Lake, Lapai, Niger State Nigeria

“…Phytoplankton Assemblage of Dangana Lake Plankton abundance and distribution are affected by seasonal changes of both physical and chemical parameters as well as microplant life in aquatic environments [31]. Changes in plankton population in the lake could be distributed to various species having t different nourishment in temperature, pH, Do, BODs and nutrients [32].…”

Dynamic Interception Effect of Internal and External Nitrogen and Phosphorus Migration of Ecological Ditches

“…Relevant research indicates that the nutrient exchange is very strong between the N and P in interstitial water and the overlying water of river and lake wetlands [4,5]. Therefore, even though external N and P contents may be under control, eutrophication in farmland drainage ditches continues to occur [6]. This is mainly caused by the continuous release of N and P in the sediment, which is termed endogenous release, for which inhibiting the release of endogenous N and P to the bottom of farmland ditches is important for reducing agricultural non-point-source pollution [7].…”