Electron budgets for the hypolimnion of a recovering urban lake, 1989‐2004: Response to changes in organic carbon deposition and availability of electron acceptors

Abstract

Hypolimnetic electron budgets were developed for sulfate-rich, eutrophic Onondaga Lake, New York, for the summer stratification periods of 16 years (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) to describe seasonal, long-term, and interannual changes in hypolimnetic metabolism. A mass balance approach was applied to the hypolimnion to estimate the consumption of electron acceptors (e.g., O 2 , NO { 3 ) and production of reduced by-products (e.g., H 2 S, CH 4 ) associated with the decomposition of organic matter. The stoichiometry of the associated redox reactions supported calculation of electron transfer in the hypolimnion and partitioning of the contributions of various metabolic pathways. In 12 of the 16 study years SO 2{ 4 reduction was the most important decomposition pathway, accounting for an average of 44% of the electron transfer in the hypolimnion. Aerobic decomposition (28%), methanogenesis (19%), and denitrification (9%) were also quantitatively important mineralization processes. The relative importance of the various decomposition pathways to overall hypolimnetic metabolism varied widely in response to an abrupt decrease in organic carbon deposition in 1987, incomplete spring turnover in 1993, and improved nitrification treatment at a contributing wastewater treatment facility in 2004. Changes in the importance of the different decomposition pathways were generally consistent with the thermodynamic constraints that regulate the spatial and temporal patterns of redox processes in aquatic sediments. On average, the discrepancy between observed dissolved inorganic carbon accumulation and that calculated from the four redox pathways was 14%; potential causes for this discrepancy include storage of reduced forms of particulate organic carbon and metabolic byproducts in the sediment.

Implications of redox processes for the rehabilitation of an urban lake, Onondaga Lake, New York

“…5b) and accumulations of the three metabolic byproducts (Fig. 5c-e) have also proceeded at approximately linear rates within the anoxic hypolimnion (Matthews et al 2008). The much higher initial pool sizes of NO 3 − in April 2004 (Fig.…”

“…Transport pathways include small-scale vertical mixing during summer stratification (Matthews et al 2008), or entrainment during the fall mixing interval (Matthews and Effler 2006b). The oxygen demand of accumulations of Fe 2+ and Mn 2+ is relatively minor in highly reducing hypolimnia, particularly where concentrations are limited by high concentrations of sulfide species (∑S 2− = H 2 S + HS − + S 2− ) (Effler 1996).…”

“…The long-term monitoring program that supported this analysis has been described previously in several related retrospective analyses (Effler 1996, 2008, Matthews and Effler 2006a, 2006b. Detailed descriptions of laboratory methods and data analyses are provided in those contributions.…”

“…The selected years depict substantial differences in certain conditions that reflect changes in anthropogenic drivers. The pool sizes were calculated from vertical profiles of each constituent and hypsographic data for the lake (Effler 1996), adopting 10.5 m as the upper bound of the hypolimnion (Matthews and Effler 2006a, 2006b, Matthews et al 2008, and normalizing by the area of this layer. A nearly linear decrease in the hypolimnetic mass of DO was observed in Onondaga Lake ( Fig.…”

Partitioning phosphorus concentrations and loads in tributaries of a recovering urban lake

“…Increased inputs of domestic and industrial wastes accompanied development of the watershed and led to degradation and loss of uses, including the cold-water fishery (late 1800s; Tango and Ringler 1996). Manifestations of severe cultural eutrophication included: (1) high concentrations of phytoplankton biomass, with occurrences of blooms of nuisance cyanobacteria (Matthews et al 2001); (2) low water clarity (Effler et al 2008b); (3) rapid seasonal loss of dissolved oxygen (DO) from the hypolimnion (Matthews and Effler 2006b); (4) accumulation of reduced by-products of anaerobic metabolism (Matthews et al 2008); and (5) severe depletion of DO in the upper waters during fall mixing associated with oxidation of the reduced constituents (Matthews and Effler 2006a).…”