Physical and Biological Responses to Flow in a Tidal Freshwater Slough Complex

Frantzich, Jared; Sommer, Ted; Scheier, Brian

doi:10.15447/sfews.2018v16iss1/art3

Cited by 19 publications

(23 citation statements)

References 74 publications

(136 reference statements)

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“…The distribution of zooplankton and nekton within the channel was strongly correlated with the hydrodynamically driven habitat zones described above. The upstream zone characterized by no exchange with downstream habitats supported higher zooplankton densities, and higher densities of Cladocera, a group more abundant in low‐velocity, freshwater habitats regionally (Frantzich et al, 2018; Kimmerer et al, 2018). The downstream, high exchange zone supported the lowest densities of zooplankton, which could reflect low phytoplankton abundance observed in the study or simply the relatively low densities of zooplankton present in many nearby SFE pelagic habitats (Kimmerer et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Hydrodynamics drive pelagic communities and food web structure in a tidal environment

et al. 2020

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Hydrodynamic processes can lead to the accumulation and/or dispersal of water column constituents, including sediment, phytoplankton, and particulate detritus. Using a combination of field observations and stable isotope tracing tools, we identified how hydrodynamic processes influenced physical habitat, pelagic communities, and food web structure in a freshwater tidal system. The pelagic habitat of a terminal channel differed spatially, likely aligning with differences in hydrodynamics. Three zones that we classified by exchange with downstream habitat had distinct water quality characteristics, supported different densities of zooplankton and nekton, and exhibited disparate support from benthic and pelagic trophic pathways to pelagic consumers. Hydrodynamically driven zones and their emergent characteristics appeared sensitive to hydrology, as elevated runoff was correlated with a shift in hydrodynamic habitat and organismal distributions. The results of our study highlight the relationship between hydrodynamic processes, biological responses, and climate, and suggest that understanding the physical process can improve understanding of pelagic habitats and communities.

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Section: Discussionmentioning

confidence: 99%

Hydrodynamics drive pelagic communities and food web structure in a tidal environment

et al. 2020

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“…The relatively high abundance and growth rates of Delta Smelt in the Yolo Bypass during recent years can be attributed to a combination of at least three factors: 1) high food density, 2) high turbidity, and 3) moderate temperature. First, calanoid copepod density from 2011–2014 was consistently higher in the Yolo Bypass than in the Sacramento River [16]. Calanoid copepods, including Pseudodiaptomus forbesi are the preferred prey for Delta Smelt [34], and dominated the diet composition of fish in our study.…”

Section: Discussionmentioning

confidence: 69%

“…Lastly, while juvenile Delta Smelt can tolerate up to 27–28°C in a laboratory setting [75] and up to 25°C in the field [43], adult Delta Smelt seem to require a lower optimal temperature for long-term survival and spawning [75,76]. Future warming of the Yolo Bypass due to climate change may shorten the maturation and spawning windows of Delta Smelt in the spring and exclude the species from the region entirely in from late-spring to fall [16,56].…”

Section: Discussionmentioning

confidence: 99%

“…In coastal systems, floodplain wetlands can function as productive nursery habitats for fish exhibiting a diversity of life histories [10,11,12]. This nursery function stems from the shallow ephemeral nature of inundated floodplain wetlands, providing refuge from large predators and high densities of prey for rapid growth [8,9,13,14,15,16,17].…”

Section: Introductionmentioning

confidence: 99%

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Role of freshwater floodplain-tidal slough complex in the persistence of the endangered delta smelt

Mahardja¹,

Hobbs

Ikemiyagi³

et al. 2019

PLoS ONE

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Seasonal floodplain wetland is one of the most variable and diverse habitats found in coastal ecosystems, yet it is also one of the most highly altered by humans. The Yolo Bypass, the primary floodplain of the Sacramento River in California’s Central Valley, USA, has been shown to provide various benefits to native fishes when inundated. However, the Yolo Bypass exists as a tidal dead-end slough during dry periods and its value to native fishes has been less studied in this state. During the recent drought (2012–2016), we found higher abundance of the endangered Delta Smelt (Hypomesus transpacificus), than the previous 14 years of fish monitoring within the Yolo Bypass. Meanwhile, Delta Smelt abundance elsewhere in the estuary was at record lows during this time. To determine the value of the Yolo Bypass as a nursery habitat for Delta Smelt, we compared growth, hatch dates, and diets of juvenile Delta Smelt collected within the Yolo Bypass with fish collected among other putative nursery habitats in the San Francisco Estuary between 2010 and 2016. Our results indicated that when compared to other areas of the estuary, fish in the Yolo Bypass spawned earlier, and offspring experienced both higher quality feeding conditions and growth rates. The occurrence of healthy juvenile Delta Smelt in the Yolo Bypass suggested that the region may have acted as a refuge for the species during the drought years of 2012–2016. However, our results also demonstrated that no single region provided the best rearing habitat for juvenile Delta Smelt. It will likely require a mosaic of habitats that incorporates floodplain-tidal sloughs in order to promote the resilience of this declining estuarine fish species.

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“…Drift invertebrates are often a more substantial part of the food web in natural flood events in Yolo Bypass (Sommer et al 2001a(Sommer et al , 2001b(Sommer et al , 2004Benigno and Sommer 2009). Nonetheless, zooplankton densities can be relatively high in Yolo Bypass (as compared to the Sacramento River) during dry seasons and drought years (Frantzich et al 2018;Goertler et al 2018). The specific reasons for these differences include longer residence time and shallower depths in the Yolo Bypass than in adjacent perennial river channels (Sommer et al 2004).…”

Section: Flooded Farm Fields Support High Biological Productivitymentioning

confidence: 99%

Farm to Fish: Lessons from a Multi-Year Study on Agricultural Floodplain Habitat

Sommer¹,

Schreier²,

Conrad

et al. 2020

SFEWS

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Large areas of California’s historic floodplain have been separated from adjacent river channels by levee construction, allowing the development of an extensive agricultural industry. Based on successful partnerships between agriculture and conservation groups to support migrating waterfowl, we examined whether seasonally flooded rice fields could be modified to provide off-channel rearing habitat for juvenile Chinook Salmon Oncorhynchus tshawytscha. During winter and spring of 2012-2017, we conducted a series of experiments in Yolo Bypass and other regions of California’s Central Valley using hatchery Chinook Salmon as a surrogate for wild Chinook Salmon, the management target for our project. Overall, we found that seasonally flooded fields are highly productive, resulting in significantly higher levels of zooplankton and high Chinook Salmon growth rates as compared to the adjacent Sacramento River. We found similar results for multiple geographical areas in the Central Valley, and in different cover types, such as non-rice crops and fallow areas. Although field substrate type did not detectably affect fish growth and survival, connectivity with upstream and downstream areas appeared to drive fish occupancy, because rearing young salmon were generally attracted to inflow in the fields, and not all of the fish successfully emigrated off the fields without efficient drainage. In general, we faced numerous logistic and environmental challenges to complete our research. For example, periodic unmanaged floods in the Yolo Bypass made it difficult to schedule and complete experiments. During severe drought conditions, we found that managed agricultural habitats produced low and variable salmon survival results, likely because of periodically high temperatures and concentrated avian predation. In addition, our project required substantial landowner time and effort to install and maintain experimental fields. Recent and future infrastructure improvements in Yolo Bypass could substantially improve options for experimental work and broaden efforts to enhance salmon habitat.

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Physical and Biological Responses to Flow in a Tidal Freshwater Slough Complex

Cited by 19 publications

References 74 publications

Hydrodynamics drive pelagic communities and food web structure in a tidal environment

Hydrodynamics drive pelagic communities and food web structure in a tidal environment

Role of freshwater floodplain-tidal slough complex in the persistence of the endangered delta smelt

Farm to Fish: Lessons from a Multi-Year Study on Agricultural Floodplain Habitat

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