Marine heatwaves have altered ecosystems globally, including changing community composition and facilitating the spread of invasive species. In south Puget Sound, Washington (USA), non-native Pacific oysters (Magallana gigas) have been farmed extensively for almost a century and grown in enhancement sites, however, they have only recently recruited in the wild. This study explores how the appearance of Pacific oysters was related to spatially (eight sites) and temporally (decade) warmer summer water temperatures in south Puget Sound and compares oyster persistence across five sites where recruitment occurred. The largest recruitment event from 2012-2020 was in the summer of 2015, in the middle of the east Pacific Blob marine heatwave which led to warm water temperatures off the west coast of North America. Throughout the study period, the number of oyster recruits each year was positively correlated with warmer water temperatures. Oyster population densities differed across the five sites where recruitment occurred and generally declined after 2015, but showed no site by year interactions, which is consistent with spatially-variable recruitment and similar post-recrutiment survival. Mean oyster shell heights also differed among sites, which could reflect different growth trajectories or recreational harvest patterns. This study supports the claim that warming sea surface temperatures may interact with species introductions to change modern biogeography. 

As the Anthropocene progresses, environmental stressors are becoming more noticeable in their impacts on aquatic ecosystems and the organisms that inhabit them. One such organism of environmental and ecological importance is the Pacific oyster, C. gigas. Under climate change, molluscan shells are likely to become weaker due to lowered calcium carbonate availability which may lead to increased mortalities. In Washington state, C. gigas provides 3200 jobs annually and lowers nitrogenous waste concentrations. Our focus in this work was to determine if temperature and pH would affect shell strength in C. gigas as climate change continues to affect their environment. We used C. gigas samples that grew in Puget Sound, Washington, over the summer months. Samples were tested for maximum load of pressure shells could withstand and correlating that to thickness to determine strength. We found that temperature and pH were not correlated to shell strength. We observed that the shell strength of C. gigas taken from Puget Sound did not depend on temperature or pH changes. Previous molluscan shell strength experiments in other settings and locations show contradictory results, but there is little evidence pertaining specifically to C. gigas. These experiments are typically conducted in laboratory settings as well, not in field settings like ours. Going forward, this concept should be reconsidered to confidently identify what the Anthropocene has in store for C. gigas.

This global change study examines the multiple-stressor impacts of heat and plastic leachates on a symbiotic clonal cnidarian, the aggregating anemone, Anthopleura elegantissima. Marine heatwaves and ocean plastics are two forms of anthropogenic pollution that are increasing and predicted to rise in future ocean conditions. In Puget Sound, intertidal marine organisms are most at risk of exposure to these combined stressors. In summer, low tides at noon leave intertidal organisms in stagnant warming water or fully exposed to desiccation. Marine heatwaves, like the one that occurred in June 2021, caused water temperatures to spike along Puget Sound coasts. Concurrently, road run-off and sewage likely expose intertidal organisms to higher concentrations of plastic leachates. Leachates are derived from machine-washed polyester clothing microplastics, polyvinyl chloride sewage pipes, and non-source point pollution that is swept through watersheds toward the coasts. Plastic pollution in the form of leachates is understudied in coastal ecosystems, compared to thermal stress. Plastic-derived leachates are the complex cocktail of chemicals that leach from plastics into the environment and are considered pollutants of emerging concern. We do not fully understand the impacts they have on the physiology of marine organisms, and even fewer studies address their impacts in the context of marine heatwaves. We will test physiological and photophysiological responses of aggregating anemones to thermal stress and plastic leachates, separately and combined. We will develop respirometry and light response curves for each of the treatment conditions and a control. We hypothesize that the cnidarian host will show increased metabolic activity indicating stress under both types of pollution, and that photosynthetic efficiency in the algal symbiont will increase with leachate exposure. We hope to use the results of this study to better understand how anemones and other cnidarians like corals are affected by the threats of plastic pollution and global warming.

Changing climate has resulted in cascading consequences to processes within the natural world, influencing physical, chemical, and biological components of our ecosystems. To properly prepare for changes within these natural systems and mitigate impacts, it is important that we understand underlying mechanisms that are being influenced by this change. One such mechanism that has a known correlation with warming temperatures—a factor of our shifting climate—is increased metabolism of cold blooded organisms. As their metabolism increases, they must consume additional food to offset the increased energy demands. To investigate this issue, I worked with the University of Washington’s Applied Ecology Lab and the National Oceanic and Atmospheric Administration’s (NOAA) Northeast Fisheries Science Center to examine whether predation by predatory fishes in the Northwest Atlantic has increased over the past 50 years. Specifically, I examined diet information for 17 commercially important fish species from 1973-2021, enabling us to capture any shifts over time. To determine if the observed changes were related to environmental conditions, I tested various climate indices as possible forcing factors. Additionally, I examined changes in the body condition of these fishes. To do so, I fit time series models to the data to estimate annual changes in consumption and body condition, and determine the degree to which the climate indices were correlated with these changes. I further hypothesized that the life history, habitat, and range of the given species may also be related to shifts in diets. These results will help inform us about potential “winners and losers” with respect to climate change within the Northwest Atlantic ecosystem, enabling management agencies to target groups that are negatively impacted by these environmental trends. Additionally, our analyses can provide insight on potential shifts in ecosystem dynamics that we would expect to see in relation to future climate change.

The recent decline in the body size of sockeye salmon (Oncorhynchus nerka) returning to Bristol Bay, Alaska has been associated with increased competition within the marine environment as these populations have increased in abundance. As an anadromous species, different populations of sockeye salmon return to freshwater environments, occupying streams of varying sizes to which they have evolved habitat-specific adaptations to local habitat conditions. In particular, fish spawning in small streams are substantially smaller than ecotypes that spawn in the deep water of rivers and lakes where sexual selection promotes large body sizes. We hypothesized that density-dependent marine growth in sockeye salmon would be most intense for large-bodied spawning ecotypes, compared to small-bodied populations where there is less evolutionary pressure to achieve large body size. Using general linear mixed-effects models, I compared the effect of run size on growth rates in sockeye salmon from a range of streams of different sizes. My preliminary results suggest that ecotypes spawning in large water bodies (stream mouth >5m wide, rivers, and beach spawners) show stronger density-dependent marine growth than ecotypes spawning in small streams (stream mouth <5m wide). These results demonstrate that evolutionary selection for spawning success as adults affects the development programs of juvenile salmon while in the ocean.

One outcome of strong intraspecific interactions is the top-down regulation of juveniles by older individuals in a population, resulting in cohort dominance. Due to their distinct spawning patterns and high variability in juvenile recruitment, many species of fish experience these interactions. Arctic char (Salvelinus alpinus) is a commercially and ecologically important species native to Alaska whose intraspecific interactions are only vaguely understood. The goal of this study was to assess the evidence for suppression of recruitment by older individuals that both compete with and cannibalize younger individuals in a population. I used Arctic char fork length data from Little Togiak River, Alaska, between 1972-2023 to construct annual size distributions. I conducted a wavelet analysis for periodicity to determine whether there was distinct cyclicity in the size distribution of individuals in the population, as would be expected by a population regulated by a dominant cohort. The analysis suggests periods of 10-15 years, the natural life span of Arctic char, where a new cohort arises from a successful recruitment event and suppresses subsequent generations through competition and cannibalism. Improving the understanding of top-down intraspecific regulation in Arctic char can help inform fisheries policy and provide additional insight into Alaskan ecosystem functions.