Metal uptake by phytoplankton during a bloom in South San Francisco Bay: Implications for metal cycling in estuaries

Limnology and Oceanography
By: , and 



The 1994 spring phytoplankton bloom in South San Francisco Bay caused substantial reductions in concentrations of dissolved Cd, Ni, and Zn, but not Cu. We estimate that the equivalent of ~60% of the total annual input of Cd, Ni, and Zn from local waste‐water treatment plants is cycled through the phytoplankton in South Bay. The results suggest that processes that affect phytoplankton bloom frequency or intensity in estuaries (e.g. nutrient enrichment) may also affect metal trapping. The bloom was characterized by hydrographic surveys conducted at weekly intervals for 9 weeks. Metal samples were collected from the water column on three occasions, timed to bracket the period when the bloom was predicted. Factors that might confound observations of biological influences, such as freshwater inputs, were relatively constant during the study. Before the bloom, concentrations of dissolved Cd were 0.81 ± 0.02 nmol kg−1, Zn concentrations were 19.8 ± 1.5 nmol kg−1, Ni were 42 ± 1.4 nmol kg−1, and Cu were 37 ± 1.4 nmol kg−1. These values are elevated relative to riverine and coastal end‐members, reflecting inputs from wastewater and(or) sediments. At the height of the bloom, dissolved Zn, Cd, and Ni were reduced to 19, 50, and 75% of their prebloom concentrations, respectively. Dissolved Cu concentrations increased 20%. The mass of Cd taken up by phytoplankton was similar to the mass of Cd removed from solution if particle settling was considered, and Cd concentrations estimated in phytoplankton were higher than concentrations in suspended particulate material (SPM). Particulate concentrations of Zn and Ni during the bloom appeared to be dominated by the influence of changes in resuspension of Zn and Ni‐rich sediments.

Publication type Article
Publication Subtype Journal Article
Title Metal uptake by phytoplankton during a bloom in South San Francisco Bay: Implications for metal cycling in estuaries
Series title Limnology and Oceanography
DOI 10.4319/lo.1998.43.5.1007
Volume 43
Issue 5
Year Published 1998
Language English
Publisher Wiley
Contributing office(s) California Water Science Center, San Francisco Bay-Delta, Toxic Substances Hydrology Program, Pacific Regional Director's Office
Description 10 p.
First page 1007
Last page 1016
Country United States
State California
Other Geospatial South San Francisco Bay
Online Only (Y/N) N
Additional Online Files (Y/N) N
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