The influence of environmental conditions on the seasonal variation of Microcystis cell density and microcystins concentration in San Francisco Estuary

Abstract

A bloom of the cyanobacteria Microcystis aeruginosa was sampled over the summer and fall in order to determine if the spatial and temporal patterns in cell density, chlorophyll a (chl a) concentration, total microcystins concentration, and percent microcystins composition varied with environmental conditions in San Francisco Estuary. It was hypothesized that the seasonal variation in Microcystis cell density and microcystin concentration was ecologically important because it could influence the transfer of toxic microcystins into the aquatic food web. Sampling for Microcystis cell density, chl a concentration, total microcystins concentration and a suite of environmental conditions was conducted biweekly at nine stations throughout the freshwater tidal and brackish water regions of the estuary between July and November 2004. Total microcystins in zooplankton and clam tissue was also sampled in August and October. Microcystis cell density, chl a concentration and total microcystins concentration varied by an order of magnitude and peaked during August and September when P B m and a B were high. Low streamflow and high water temperature were strongly correlated with the seasonal variation of Microcystis cell density, total microcystins concentration (cell) -1 and total microcystins concentration (chl a) -1 in canonical correlation analyses. Nutrient concentrations and ratios were of secondary importance in the analysis and may be of lesser importance to seasonal variation of the bloom in this nutrient rich estuary. The seasonal variation of Microcystis density and biomass was potentially important for the structure and function of the estuarine aquatic food web, because total microcystins concentration was high at the base of the food web in mesozooplankton, amphipod, clam, and worm tissue during the peak of the bloom.

Mathematical modeling of Microcystis aeruginosa growth and [D-Leu1] microcystin-LR production in culture media at different temperatures

“…The production of [D-Leu 1 ] MC-LR decreased with increasing temperature, coinciding with the findings of Gorham, 1964;Runnegar et al, 1983;van der Westhuizen and Eloff, 1985;Cood and Poon, 1988;Sivonen, 1990;Rapala et al, 1997;Lehman et al, 2008;Wang et al, 2010 andGiannuzzi et al (2016). van der Westhuizen and Eloff (1985) reported that the optimal growth conditions do not coincide with the production of toxins.…”

Seasonal dynamics of water bloom-forming Microcystis morphospecies and the associated extracellular microcystin concentrations in large, shallow, eutrophic Dianchi Lake

“…An earlier study result of Pan et al (2006) also revealed a similar result that the MC concentrations of all the samples were lower than 1 μg/L in western Fubao bay of the Dianchi Lake. Previous studies have reported that MCs in water samples were strongly correlated with environmental factors, such as TN (Graham et al, 2006), TP (Kotak et al, 2000), low stream flow and high WT (Lehman, 2008;Duong et al, 2012) and NO 3 − concentration (Mitsuhiro et al, 2007). In contrast, according to Jungmann et al (1996), MC concentration was not correlated with any measured variables in a hypereutrophic reservoir in Germany.…”

A Conceptual Model of the Aquatic Food Web of the Upper San Francisco Estuary

“…(Jacoby et al 2000;Lehman et al 2005Lehman et al , 2008 and the establishment of nuisance aquatic vegetation (largely E. densa and Eichhornia crassipes) (Brown and Michniuk 2007;Sousa et al 2009Sousa et al , 2010Yarrow et al 2009). Stands of E. densa alter the physical structure of Delta channels and support the colonization of non-native fishes such as sunfish (Centrarchidae), which are often able to outcompete or prey upon native fishes (See 2.30 Structure, below) Grimaldo et al 2004;Nobriga et al 2005;Nobriga and Feyrer 2007;Ferrari et al 2014).…”

“…Blooms can continue until they are broken up by increased flows, turbulence from wind-causing mixing-or drawdown of nutrients by the phytoplankton bloom itself. (Lehman et al 2008). Harmful algal blooms may be related to high concentrations of NH 4 (Lehman et al 2010).…”