Prey 2017 Blackbox Project

[Shinyoung Gedris]

Anintensive research program in the U.S. and Canada is studying why so few salmon in the Salish Sea are returning home to spawn. They are uncovering a complex web of problems involving predators, prey and other factors that put salmon at risk as they migrate to the ocean. We begin a four-part series on the Salish Sea Marine Survival Project, including new findings presented at the 2018 Salish Sea Ecosystem Conference last spring in Seattle.

Even in good years, when large numbers of salmon would leave the streams, there was always a great deal of uncertainty about how many would make it back home. Mystery surrounded what the fish were doing out in the saltwater. Were they starving or were they thriving?

Studies by more than 200 scientists on both sides of the border have revealed a tangled food web involving a multitude of predators and prey surrounding their primary species of study: Chinook and coho salmon and steelhead trout. To survive, these salmonids must not only become capable predators, but they must also remain vigilant to avoid larger predators trying to eat them.

The percentage of young Chinook and coho salmon that survive to become spawning adults varies from one stream to another. In general, their survival rates in Puget Sound have declined dramatically over the past 35 years.

The Salish Sea Marine Survival Project, coordinated by Long Live the Kings in the U.S., has helped identify many threats to the survival of Puget Sound Chinook, coho and steelhead. Each species has its unique life history and thereby faces its own set of problems. Smaller groups of salmon, such as populations within a species, often share similar problems. But, since no two estuaries are alike, Chinook in one estuary may face different threats from Chinook in another estuary.

Meanwhile, for the most part, chum, pink and sockeye salmon have not undergone such dramatic declines. The reasons are tied to ecological processes that ripple through the food web, according to scientists, but exact differences have not been identified.

All of these issues are being studied by researchers in both the U.S. and Canada. In April, more than 30 researchers involved in the Salish Sea Marine Survival Project presented their findings during the three-day Salish Sea Ecosystem Conference in Seattle.

More than 80 studies have been launched, with more than 20 scientific articles published in peer-reviewed journals. Partners include some 60 federal, state, tribal, nonprofit, academic and private entities. In Canada, the project is coordinated by the Pacific Salmon Foundation, a nonprofit group headed by President and CEO Brian Riddell.

Most of the studies support the notion that the greatest mortality for salmon and steelhead occurs after the fish leave the streams but before they depart from the inland waters of the Salish Sea. That does not discount the importance of freshwater streams, where the fish hatch and spend at least the early part of their lives. Some will spend a year or more in freshwater before heading out to sea.

Whenever they enter saltwater, the condition and fitness they have achieved in freshwater no doubt plays an important role in their long-term survival, according to Beauchamp and others. The second challenge comes during the transition to the open waters of Puget Sound, followed by the ongoing challenge of finding food and avoiding predators in the open ocean.

Studies by Greg Ruggerone of Natural Resources Consultants in Seattle and other researchers have raised the prospect that the North Pacific Ocean, where many of the fish end up, may be at or near carrying capacity for some species of salmon, with potential adverse effects on others.

With ocean conditions favoring pink, chum and sockeye, the number of wild salmon of those species is higher than at any time since the early 1940s. Many of those salmon are coming back to near-pristine streams in Alaska and northern British Columbia, Ruggerone said. Together with near-record numbers of hatchery fish, all those salmon could be exhausting the available food supply, he said.

Chinook salmon from the Salish Sea are believed to swim along the continental shelf with some reaching Alaskan waters, but nobody has studied how much effect large numbers of pink salmon are having on the survival of Puget Sound Chinook, Ruggerone said.

Streams are an important conduit for carbon transport to downstream environments and the atmosphere. Drivers, magnitude, and variability of carbon dioxide (CO2) emissions from streams are well understood. However, streams also emit significant amounts of methane, a greenhouse gas 28 times more potent than CO2. Yet, the magnitude, drivers and temporal variation of methane is not understood. Using measurements of gas concentration and gas evasion to the atmosphere, we captured temporal variation in gas flux to the atmosphere. Gas data combined with other environmental information, we identified key drivers of gas evasion. We found that CO2 emissions are significantly higher at night while methane emissions do not statistically differ from those during the day. Dissolved oxygen concentrations and groundwater sources were identified as drivers of both gases. These results highlight the need for further exploration of drivers of greenhouse gas fluxes from aquatic ecosystems, especially methane.

We hypothesized that well-mixed soil would harbor less rich communities and demonstrate homogenizing processes. Findings supported our hypotheses, with a > 20% decrease in soil bacterial richness in well-mixed soil, and increasingly self-similar communities structured by homogenizing selection and dispersal. Our results imply that the vast microbial diversity in soil may be underpinned by the unmixed and spatially heterogeneous nature of soil. We will also take a preliminary look at the effects of disturbance via soil mixing in the context of agricultural tillage in southern WI and the invasive Amynthas spp. (jumping worm) activity at the UW Arboretum. By better understanding the importance of spatial heterogeneity and physical disturbance for soil microbial communities, we may better extrapolate how anthropogenic disturbances, such as climate change or land use change, may affect broad soil functions.

Throughout western North America, anomalously short fire-return intervals (FRI) are becoming more common, reducing postfire tree establishment and eroding forest resilience. However, potential effects on understory plant communities, the most diverse floral stratum in temperate forests, remain less well understood. In Greater Yellowstone, forests adapted to historical FRI of 100-300yrs have recently reburned at

To elucidate the effects of short- (125yr) interval fire, we quantified plant community composition in 31 paired 0.25-ha plots across a range of FRI, time since fire (TSF), and climatic conditions. In each plot, percent cover by species was measured in 25 0.25-m2 quadrats and plot richness determined. Paired t-tests were used to quantify differences in species and functional group cover. Pairwise compositional differences were assessed using dissimilarity indices, and multiple regression was used to explain dissimilarity over environmental and climatic variables.

Predator-prey coupling can result in oscillations of predator-prey abundances. Strong predator-prey coupling can trigger entire ecosystem trophic cascades where the shifts in predator and prey abundances has a rippling impact on lower trophic levels. Here, we investigated how the body condition (body weight relative to body length) of a strongly coupled predator and prey changes as their respective population densities shifted due to cascading interactions.

We found that predator and prey body condition was strongly influenced by their respective population densities, which signifies strong population density dependence. Further, we found predator and prey body conditions were inversely related, which highlights strong predator-prey coupling. We further note that in cases where coupled predator-prey have inverse body condition relationships, we can use historical length/weight data to illuminate past ecological conditions. Here, we were able to suggest whether the food web was historically three or four-tiered based on historical predator body condition. Overall, this study highlights strong predator-prey coupling as indicated by inverse body condition, and highlights the application of synthesizing long-term trends in body condition.

Grassland habitat restoration is critical for preventing continued loss of plant diversity. As we enter the United Nations Decade on Restoration, restoration ecologists are actively monitoring restoration outcomes so that we can understand the mechanisms responsible for failure or success. However, there is no scientific consensus on how to determine if restoration efforts are successful or which metrics best measure outcomes. This leads us to a clear question: how do we define and measure restoration success? To answer this, we used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) review process to summarize how restoration outcomes are measured. In our review, we ask the following questions:

We identified >500 peer-reviewed articles discussing outcomes of grassland restoration worldwide. Target organisms ranged widely from soil microbes to plants to songbirds, which, when paired with more than 100 ecological metrics led to 600 unique metrics for reporting restoration outcomes. Quantitative metrics, including plant diversity and abundance, were the most common while metrics with an assigned value, such as floristic quality index and coefficient of conservatism, were infrequent. Which metric is appropriate often depends on the amount of degradation and the restoration goals. It is essential to set intentional goals when restoring grassland ecosystems and to continue refining the most appropriate metrics to use when assessing restoration success.

Initial results show a relatively high (57%) and geographically widespread infection rate of Spiroplasma throughout the Nebria ingens species complex. Both host and microbe populations show a similar trend of gradual genetic divergence across geographical space, but Spiroplasma appears to have longer dispersal distance. Also, findings show Spiroplasma in sympatric species of Nebria at different altitudes. Our ongoing research utilizes population genomic variation of both species, including the beetle mitochondrial DNA, to identify inheritance patterns and assess the beneficial or detrimental ecological role of Spiroplasma in this insect host.

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