Drivers of Ecosystem Metabolism in an Anthropogenically Modified Delta.
- 1Environmental Fluid Mechanics Laboratory, Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 USA.
- 2San Francisco Estuary Institute, Richmond, CA 94804 USA.
- 3California Water Science Center, U.S. Geological Survey, Sacramento, CA USA.
Abstract
Estuaries are under threat globally from a wide range of stressors, with rates of ecosystem metabolism - respiration (R), gross primary production (GPP), and net ecosystem metabolism (NEM) - representing a way for resource managers to quantify their impacts. In this study, we assessed how natural and anthropogenic stressors have altered metabolism within the extensively modified Sacramento-San Joaquin Delta ("Delta") in California, USA. Metabolism was estimated using a diel open-water technique utilizing dissolved oxygen measurements from a high frequency (15 min) water quality monitoring array, and spanned 6 sites across 11 years (2014-2025). Our analyses were driven by a conceptual model of Delta carbon (C) cycling focused on 1) Invasive aquatic vegetation (IAV), 2) Phytoplankton, 3) Wastewater treatment plant (WWTP) upgrades, 4) Large-scale flow alterations, and 5) Wet vs. dry years. We found that allochthonous C fuels net heterotrophy in the outer riverine sections of the Delta, while the heavily vegetated central Delta produces autochthonous C remineralized elsewhere in the system. IAV were the dominant primary producers, with low phytoplankton production except during a historic bloom. WWTP upgrades imparted negligible changes to metabolism, with low chlorophyll a (< 5 µg L⁻¹) both before and after. Introduction of a flow barrier - a management response to drought - hydrodynamically isolated deep-water channels from nearby shallow areas, resulting in decreased metabolism indicative of changes to C transport. Contrary to past research, low rainfall years were associated with increased metabolism. This study demonstrates how multi-sensor arrays can be used to quantify ecosystem responses to major environmental stressors.Supplementary information
The online version contains supplementary material available at https://doi.org/10.1007/s12237-026-01833-z.
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BibTeX
@article{volaric2026drivers,
title = {{Drivers of Ecosystem Metabolism in an Anthropogenically Modified Delta.}},
author = {Martin P Volaric and Brian A Bergamaschi and Ariella Chelsky and David B Senn and Stephen G Monismith},
journal = {Estuaries and coasts : journal of the Estuarine Research Federation},
year = {2026},
month = oct,
doi = {10.1007/s12237-026-01833-z},
url = {https://europepmc.org/article/MED/42927030},
note = {CC BY},
}
RIS
TY - JOUR
TI - Drivers of Ecosystem Metabolism in an Anthropogenically Modified Delta.
AU - Martin P Volaric
AU - Brian A Bergamaschi
AU - Ariella Chelsky
AU - David B Senn
AU - Stephen G Monismith
PY - 2026
DA - 2026/10/23
JO - Estuaries and coasts : journal of the Estuarine Research Federation
DO - 10.1007/s12237-026-01833-z
UR - https://europepmc.org/article/MED/42927030
AB - Estuaries are under threat globally from a wide range of stressors, with rates of ecosystem metabolism - respiration (R), gross primary production (GPP), and net ecosystem metabolism (NEM) - representing a way for resource managers to quantify their impacts. In this study, we assessed how natural and anthropogenic stressors have altered metabolism within the extensively modified Sacramento-San Joaquin Delta ("Delta") in California, USA. Metabolism was estimated using a diel open-water technique utilizing dissolved oxygen measurements from a high frequency (15 min) water quality monitoring array, and spanned 6 sites across 11 years (2014-2025). Our analyses were driven by a conceptual model of Delta carbon (C) cycling focused on 1) Invasive aquatic vegetation (IAV), 2) Phytoplankton, 3) Wastewater treatment plant (WWTP) upgrades, 4) Large-scale flow alterations, and 5) Wet vs. dry years. We found that allochthonous C fuels net heterotrophy in the outer riverine sections of the Delta, while the heavily vegetated central Delta produces autochthonous C remineralized elsewhere in the system. IAV were the dominant primary producers, with low phytoplankton production except during a historic bloom. WWTP upgrades imparted negligible changes to metabolism, with low chlorophyll a (< 5 µg L⁻¹) both before and after. Introduction of a flow barrier - a management response to drought - hydrodynamically isolated deep-water channels from nearby shallow areas, resulting in decreased metabolism indicative of changes to C transport. Contrary to past research, low rainfall years were associated with increased metabolism. This study demonstrates how multi-sensor arrays can be used to quantify ecosystem responses to major environmental stressors.Supplementary information The online version contains supplementary material available at https://doi.org/10.1007/s12237-026-01833-z.
SN - 1559-2723
SN - 1559-2731
ER -