Climate Change Impacts on San Francisco Estuary Aquatic Ecosystems: A Review

Herbold, Bruce; Bush, Eva; Castillo, Gonzalo; Colombano, Denise D.; Hartman, Rosemary; Lehman, Peggy W.; Mahardja, Brian; Sommer, Ted

doi:10.15447/sfews.2022v20iss2art1

Cited by 10 publications

(12 citation statements)

References 123 publications

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“…Trends over the 39‐year data sets revealed substantial interannual variation in both Flow and SST (Figure 1b). As expected of a system influenced by California's Mediterranean hydroclimate, the Flow time series encompassed multiple consecutive dry years (e.g., 1987–1992, 2012–2016); however, earlier in the time series, these droughts were interspersed with multiple consecutive wet years (e.g., 1982–1984; 1995–1999), and were later punctuated by singular, extreme wet years (e.g., 2006, 2011, 2017) (Herbold et al, 2022). Typical of Eastern Pacific Ocean climate oscillations, the SST time series encompassed cool and warm phases.…”

Section: Resultsmentioning

confidence: 99%

Four decades of climatic fluctuations and fish recruitment stability across a marine‐freshwater gradient

Colombano

Carlson

Hobbs

et al. 2022

Global Change Biology

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Investigating the effects of climatic variability on biological diversity, productivity, and stability is key to understanding possible futures for ecosystems under accelerating climate change. A critical question for estuarine ecosystems is, how does climatic variability influence juvenile recruitment of different fish species and life histories that use estuaries as nurseries? Here we examined spatiotemporal abundance trends and environmental responses of 18 fish species that frequently spend the juvenile stage rearing in the San Francisco Estuary, CA, USA. First, we constructed multivariate autoregressive state‐space models using age‐0 fish abundance, freshwater flow (flow), and sea surface temperature data (SST) collected over four decades. Next, we calculated coefficients of variation (CV) to assess portfolio effects (1) within and among species, life histories (anadromous, marine opportunist, or estuarine dependent), and the whole community; and (2) within and among regions of the estuary. We found that species abundances varied over space and time (increasing, decreasing, or dynamically stable); and in 83% of cases, in response to environmental conditions (wet/dry, cool/warm periods). Anadromous species responded strongly to flow in the upper estuary, marine opportunist species responded to flow and/or SST in the lower estuary, and estuarine dependent species had diverse responses across the estuary. Overall, the whole community when considered across the entire estuary had the lowest CV, and life histories and species provided strong biological insurance to the portfolio (2.4‐ to 3.5‐fold increases in stability, respectively). Spatial insurance also increased stability, although to a lesser extent (up to 1.6‐fold increases). Our study advances the notion that fish recruitment stability in estuaries is controlled by biocomplexity—life history diversity and spatiotemporal variation in the environment. However, intensified drought and marine heatwaves may increase the risk of multiple consecutive recruitment failures by synchronizing species dynamics and trajectories via Moran effects, potentially diminishing estuarine nursery function.

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Section: Resultsmentioning

confidence: 99%

Four decades of climatic fluctuations and fish recruitment stability across a marine‐freshwater gradient

Colombano

Carlson

Hobbs

et al. 2022

Global Change Biology

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“…Water infrastructure and habitat restoration tools may allow managers to mitigate climate change impacts in the SF Estuary (see Herbold et al, 2022). However, uncertainties remain about the extent to which these actions could ameliorate warming and food scarcity and, as a result, also warrant further study.…”

Section: Discussionmentioning

confidence: 99%

“…Like most estuaries around the world, the SF Estuary is changing rapidly (Herbold et al, 2022). Regional climate change impacts are expected to amplify hydrologic extremes (Swain et al, 2018) against a backdrop of seasonal, annual, and decadal oceanic and atmospheric variability (Cloern et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

Disentangling abiotic and biotic controls of age‐0 Pacific herring population stability across the San Francisco Estuary

et al. 2023

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Pacific herring (Clupea pallasii) is an ecologically and commercially valuable forage fish in the North Pacific Ocean. However, knowledge gaps exist around the abiotic and biotic drivers behind its variable population dynamics—as well as on the ability of the species to show spatially structured trends that stabilize population portfolios in the face of environmental change. Here we examined how historical hydroclimatic variability in the San Francisco Estuary (California) has driven age‐0 Pacific herring population dynamics over 35 years. First, we used wavelet analyses to examine spatiotemporal variation and synchrony in the environment, focusing on two key variables: salinity and temperature. Next, we fitted multivariate autoregressive state‐space models to environmental and abundance time series to test for spatial structure and to parse out abiotic (salinity and temperature) from biotic influences (spawning and density dependence). Finally, we examined the stabilizing effects of spatially asynchronous population fluctuations (i.e., portfolio effects) across the estuary. Our results showed that temperature, but not salinity, fluctuated synchronously across regions on seasonal and decadal timescales. The top‐ranked model showed strong evidence of regional population structure and regional variation in population responses to the environment. As expected, age‐0 herring were generally associated with cooler, saltier conditions in spring. Density dependence was strong in all regions, suggesting that local factors influencing rearing conditions limited juvenile population growth across the estuary. Additionally, age‐0 abundance fluctuations were on average 15% more stable across the estuary than in individual regions, demonstrating that portfolio effects arising from population asynchrony have helped to stabilize recruitment across the estuary over the past four decades. We contend that ecosystem‐based fishery management strategies to restore eelgrass and tidal marsh rearing habitats could increase the carrying capacity of the estuary, further stabilizing the herring population and reducing the risk of fishery closures.

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“…Snowpack loss over the Great Basin and changing synoptic circulations suggests increasing chances of hot and fire-favoring fall and winter season Santa Ana winds [24,72], which bring forth numerous negative economic and health impacts on large populations [73,74]. Additional reductions in streamflow from major rivers once flowing into the Sacramento-San Joaquin River Delta, particularly during the dry and extended warm season (June-September; [75]) will exacerbate the existing suite of widespread problems arising due to changes in ecosystem health, water quality, water availability and electricity generation [11,76,77].…”

Section: Discussionmentioning

confidence: 99%

“…Loss of snowpack alters the mountain hydrology many societies and ecosystems have long relied upon. Warming-induced snow loss changes the timing, quantity, and quality of water resources provided by headwater regions to downstream communities [1,2,10,11] and reduces seasonal drought prediction skill [12]. A modern analog of an increasingly snow-free and drought-prone future is unfolding in real-time in the southwestern United States, a global hotspot of freshwater vulnerability [13].…”

Section: Introductionmentioning

confidence: 99%

Decline in Seasonal Snow During a Projected 20-Year Dry Spell

Hatchett¹,

Rhoades²,

McEvoy³

2022

Preprint

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Snowpack loss in midlatitude mountains is ubiquitously projected by Earth system models, though the magnitudes, persistence and time horizons of decline vary. Using daily downscaled hydroclimate and snow projections we examine changes in snow seasonality across the U.S. Pacific Southwest region during a simulated severe 20-year dry spell in the 21st century (2051–2070) developed as part of the 4th California Climate Change Assessment to provide a "stress test" for water resources. Across California’s mountains, substantial declines (30–100% loss) in median peak annual snow water equivalent accompany changes in snow seasonality throughout the region compared to the historic period. We find 80% of historic seasonal snowpacks transition to ephemeral conditions. Subsetting empirical-statistical wildfire projections for California by snow seasonality transition regions indicates a two-to-four-fold increase in burned area, consistent with recent observations of high elevation wildfires following extended drought conditions. By analyzing six of the major California snow-fed river systems we demonstrate snowpack reductions and seasonality transitions result in concomitant declines in annual runoff (47-58% of historic values). The negative impacts to statewide water supply reliability by the projected dry spell will likely be magnified by changes in snowpack seasonality and increased wildfire activity.

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Climate Change Impacts on San Francisco Estuary Aquatic Ecosystems: A Review

Cited by 10 publications

References 123 publications

Four decades of climatic fluctuations and fish recruitment stability across a marine‐freshwater gradient

Four decades of climatic fluctuations and fish recruitment stability across a marine‐freshwater gradient

Disentangling abiotic and biotic controls of age‐0 Pacific herring population stability across the San Francisco Estuary

Decline in Seasonal Snow During a Projected 20-Year Dry Spell

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