Interannual variability in dissolved inorganic nutrients in northern San Francisco Bay estuary

Abstract

Nearly two decades of seasonal dissolved inorganic nutrient-salinity distributions in northern San Francisco Bay estuary illustrate interannual variations in effects of river flow (a nutrient source) and phytoplankton productivity (a nutrient sink). During winter, nutrient sources dominate the nutrient-salinity distribution patterns (nutrients are at or exceed conservative mixing concentrations). During summer, however, the sources and sinks are in close competition. In summers of wet years, the effects of increased river flow often dominate the nutrient distributions (nutrients are at or less than conservative mixing concentrations), whereas in summers of dry years, phytoplankton productivity dominates (the very dry years 197661977 were an exception for reasons not yet clearly known). Such source/sink effects also vary with chemical species. During summer the control of phytoplankton on nutrient distributions is apparently strongest for ammonium, less so for nitrate and silica, and is the least for phosphate. Furthermore, the strength of the silica sink (diatom productivity) is at a maximum at intermediate river flows. This relation, which is in agreement with other studies based on phytoplankton abundance and enumeration, is significant to the extent that diatoms are an important food source for herbivores.The balance or lack of balance between nutrient sources and sinks varies from one estuary to anotherjust as it can from one year to another within the same estuary. At one extreme, in some estuaries river flow dominates the estuarine dissolved inorganic nutrient distributions throughout most of the year. At the other extreme, phytoplankton productivity dominates. In northern San Francisco Bay, for example, the phytoplankton nutrient sink is not as strong as in less turbid estuaries. In this estuary, however, river effects, which produce or are associated with near-conservative nutrient distributions, are strong even at flows less than mean-annual flow. Thus, northern San Francisco Bay appears to be an estuary in between the two extremes and is shifted closer to one extreme or the other depending on interannual variations in river flow. Hydrobiologia 129, 37-58 (1985). 0 Dr W. Junk Publishers, Dordrecht. Printed in the Netherlands.

Dynamics of dissolved and biogenic silica in the freshwater reaches of a macrotidal estuary (The Scheldt, Belgium)

“…If all factors influencing diatom growth other than silica availability and discharge are kept constant, an optimal discharge can be found at which the highest diatom production is reached, as shown by model simulations carried out on Zone 1 during summer 2003 by . This phenomenon was also observed on an inter-annual timescale by Peterson et al (1985) in the San Francisco estuary.…”

The distribution and temporal dynamics of the estuarine macroalgal community of San Francisco Bay

“…A major question remains concerning the source of nutrients for a benthic algal bloom in San Pablo Bay. Nutrients (NO3 + NOz, NH,, and PO,) are usually depleted in summer months compared to winter (Peterson et al, 1985). However, there is a slight increase in summer NO3 + NO2 concentrations in San Pablo Bay compared to either Suisun or Central Bays.…”

Time scales of circulation and mixing processes of San Francisco Bay waters

“…In the consideration of solute and particulate distributions, one must be concerned with where the water goes (circulation), how it mixes, and what sources and sinks exist. Sources and sinks are considered elsewhere Peterson, 1979;Peterson et al, 1985). This paper establishes the foundation for the first two concerns.…”