Evaluation of primary production in Lake Erie by multiple proxies

Abstract

Direct measurements of rates of primary production in Lake Erie are few and uncertainties surround rate measurements based on radiocarbon and the light-dark bottle incubation methods. For these reasons, we conducted a series of simultaneous primary productivity measurements in Lake Erie in July and August of 2003, based on incubation with [14C]-NaHCO3, the light-dark bottle method, and incubation with (18)O enriched water. Significant differences in the rates of primary production obtained by incubations with [(18)O]-H2O (0.19-34.60 mmol-O2 m(-3) h(-1)), [14C]-NaHCO3 (0.03-90.50 mmol-C m(-3) h(-1)), and light-dark bottles (0.06-60.78 mmol-O2 m(-3) h(-1)) were evident in six out of nine comparisons. Within the epilimnion, [(18)O]-H2O rates of primary production were significantly different from rates based on [14C]-NaHCO3 and light-dark bottles in all four comparisons and lower rates were obtained in three out of four comparisons. Eutrophic conditions in Sandusky Bay, Lake Erie were evident from the high primary production rates of 20.50-34.60 mmol-O2 m(-3) h(-1) ([(18)O]-H2O), 34.39-90.50 mmol-C m(-3) h(-1) ([14C]-NaHCO3), and 46.66-60.78 mmol-O2 m(-3) h(-1) (light-dark bottle). The photosynthetic quotient (PQ), or ratio of O2 production to CO2 consumption during photosynthesis, averaged 0.64+/-0.33 and 1.93+/-1.93, respectively, based on a comparison of [(18)O]-H2O to [14C]-NaHCO3 rates or light-dark bottle to [14C]-NaHCO3 production rates, respectively, demonstrating that photosynthesis in Lake Erie communities primarily follows expected stochiometric trends. The average of the ratio of production rates based on incubation with [(18)O]-H2O relative to those obtained by the light-dark incubation method was 0.66+/-0.33, indicating a tendency for the [(18)O]-H2O method to provide slightly lower estimates of production in Lake Erie. Lower estimates of primary production based on [(18)O]-H2O incubation relative to the other two approaches is most likely a consequence of consumption of labeled O2 within the cell or dilution of label by the release of O2 from supersaturated cells. This latter effect may be particularly characteristic of eutrophic environments.

Effects of biological and physical factors on seasonal oxygen dynamics in a stratified, eutrophic coastal ecosystem

“…8). In agreement with our results, high contributions of benthic respiration (52% to 77%) in association with bottom hypoxia have been observed in eutrophic Lake Erie during summer stratification (Ostrom et al 2005). A subsequent study of Lake Erie reported that benthic respiration became more important as summer progressed (Wang et al 2008), increasing from 33% in early summer to 53% in late summer.…”

“…Oxygen that is respired within bottom sediments (hereafter referred to as benthic respiration) has a small fractionation effect, ranging from 0% to 23% (Brandes and Devol 1997). A substantial contribution of benthic respiration would significantly reduce the net fractionation factor in bottom waters (Ostrom et al 2005;Wang et al 2008). By applying this stable isotope technique to the Louisiana continental shelf, Quiñ ones-Rivera et al.…”

Short-term variation of triple oxygen isotopes and gross oxygen production in the Sagami Bay, central Japan

“…Several investigators (Bender et al 1987;Kiddon et al 1995;Bender et al 1999Bender et al , 2000 found higher production by 18 O incubation than 14 C by a factor of two. On the contrary, recently Ostrom et al (2005) found that primary production by 18 O incubation is significantly lower than 14 C and LD bottle incubations in the eutrophic and mesotrophic environment and attributed due to consumption of labeled O 2 within cells or evolution of extraneous O 2 . In order to alleviate these problems, Luz and Barkan (2000) applied variations in ratios of all three stable O 2 isotopes to estimate changes in global GOP.…”

Nitrogen cycling in Sandusky Bay, Lake Erie: oscillations between strong and weak export and implications for harmful algal blooms

“…This system is hypereutrophic (Ostrom et al, 2005), with the cyanobacterium Planktothrix dominating phytoplankton biomass from May to October and N-fixing phytoplankton making up a small portion of the biomass (Davis et al, 2015). Sandusky Bay experiences large fluctuations in NO − 3 concentrations and dissolved N : P ratios throughout the summer (Davis et al, 2015;Conroy et al, 2017), suggesting that the dynamic N cycling may influence cHAB formation in this system.…”