Contrasting biogeochemistry of six trace metals during the rise and decay of a spring phytoplankton bloom in San Francisco Bay

Abstract

The spring 2003 phytoplankton bloom in South San Francisco Bay (South Bay) affected the cycling of Mn, Co, Zn, Ni, and Pb, but not Cu. We followed this diatom bloom for 2 months, capturing a peak in chlorophyll a (Chl a) of .150 mg L 21 and then an increase in dissolved organic carbon of .400 mmol L 21 as phytoplankton decomposed. To determine how the stages of the bloom affected metal concentrations, we used principal component analysis to reduce our 15 water chemistry variables into a bloom factor, a sorbent factor, and a decay factor. Increasing values of the bloom factor, which was a composite of dissolved oxygen, Chl a, and other variables, significantly accounted for reductions in dissolved Mn, Ni, and Pb. We attributed those declines to microbial oxidation, phytoplankton uptake, and sorption onto phytoplankton, respectively. In contrast, dissolved Cu concentrations were not explained by either the bloom or decay factors, consistent with previous studies showing its strong organic complexation and limited bioavailability in South Bay. The decay factor significantly accounted for increases in dissolved Mn, Co, Zn, and Pb. Decomposing bloom material presumably caused suboxic conditions in surface sediments, resulting in release of metals to overlying waters during reductive dissolution of Mn and Fe (hydr)oxides. These alterations in metal cycling during a nutrient-enriched bloom were evidence of eutrophication. Annually, phytoplankton productivity has the potential to affect metal retention in the estuary; in 2003, 75% of Ni discharged into lower South Bay by wastewater treatment plants was cycled through phytoplankton.

Diurnal variations of trace metals and heterotrophic bacterioplankton concentration in a small boreal lake of the White Sea basin

“…For copper, even during the bloom, this element behaves independently on biological and hydrochemical parameters (Luengen et al, 2007). Independence of Cu concentration (unlike Zn) from that of chlorophyll and biogenic components has been also reported for England lakes during the diatom bloom period (Reynolds and Hamilton-Taylor, 1992).…”

“…The variation of Zn concentration in the surface water of lake Vilno is almost an order of magnitude higher than that of the Chl a. The independence of Zn on pH and other macroscopic parameters of solution variations is at first glance surprising because Zn uptake by phytoplankton is strongly pH-dependent (Ge´labert et al, 2006;Tripathi et al, 2009) and Zn concentration during the bloom often follows that of the Chl a (Luengen et al, 2007). Moreover, the pH is known to be the governing factor of metal adsorption on the surface of photosynthetic microorganisms such as diatoms or cyanobacteria (Ge´labert et al, 2007;Pokrovsky et al, 2008aPokrovsky et al, , 2008b.…”

“…However the diurnal patterns of trace metal concentration remain poorly investigated. In contrast, diurnal variations of trace elements were extensively studied on marine and coastal systems (Luengen et al, 2007) and in rivers (Brick and Moore, 1996;Jones et al, 2004;Gammons et al, 2005aGammons et al, , 2005b. In the latter, these variations are known to be induced by change in environmental conditions such as temperature and biological activity and are strongly controlled by adsorption processes (e.g., Nimick et al, 2005;Parker et al, 2007).…”

Quantification of phosphorus in single cells using synchrotron X-ray fluorescence

“…As a result, P can serve as a useful proxy for total cell biomass in studies of cell elemental composition (e.g. Brand, 1991;Luengen et al, 2007), and P can be used to identify the location of the nucleus in microprobe studies (Paunesku et al, 2006). The availability of P often limits the growth of phytoplankton in freshwater systems (Schindler, 1977;Elser et al, 1990), as well as in some marine systems (Mills et al, 2004).…”

Impact of heterotrophic bacterium Pseudomonas aureofaciens on the release of major and trace elements from podzol soil into aqueous solution

“…For Cu, on the other hand, the complexes are too strong and, thus, not biodegradable under our experimental conditions. Indifferent behavior of Cu with regard to microbial activity is fairly well known in natural aquatic systems (Luengen et al, 2007;Reynolds and Hamilton-Taylor, 1992;Pokrovsky and Shirokova, 2013) and laboratory experiments (Shirokova et al, 2015). The high correlation coefficient between Cu and DOC concentrations in abiotic experiments suggests that Cu is associated with dissolved organic ligands, facilitating its release from bacteria-free soil into the solution.…”