Phytoplankton fuels Delta food web

California Agriculture
By: , and 

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Abstract

Populations of certain fishes and invertebrates in the Sacramento-San Joaquin Delta have declined in abundance in recent decades and there is evidence that food supply is partly responsible. While many sources of organic matter in the Delta could be supporting fish populations indirectly through the food web (including aquatic vegetation and decaying organic matter from agricultural drainage), a careful accounting shows that phytoplankton is the dominant food source. Phytoplankton, communities of microscopic free-floating algae, are the most important food source on a Delta-wide scale when both food quantity and quality are taken into account. These microscopic algae have declined since the late 1960s. Fertilizer and pesticide runoff do not appear to be playing a direct role in long-term phytoplankton changes; rather, species invasions, increasing water transparency and fluctuations in water transport are responsible. Although the potential toxicity of herbicides and pesticides to plank- ton in the Delta is well documented, the ecological significance remains speculative. Nutrient inputs from agricultural runoff at current levels, in combination with increasing transparency, could result in harmful algal blooms. 

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Phytoplankton fuels Delta food web
Series title California Agriculture
DOI 10.3733/ca.v057n04p104
Volume 57
Issue 4
Year Published 2003
Language English
Publisher University of California Division of Agriculture and Natural Resources
Contributing office(s) Toxic Substances Hydrology Program, San Francisco Bay-Delta
Description 6 p.
First page 104
Last page 109
Country United States
State California
City San Francisco
Other Geospatial Sacramento–San Joaquin River Delta
Online Only (Y/N) N
Additional Online Files (Y/N) N