CURRENT PROJECTS

PAST PROJECTS


CURRENT PROJECTS

MONITORING FOR change in california

In collaboration with Reef Check CA and the Monterey Bay Aquarium Research Institute (MBARI), the Kroeker lab is deploying oceanographic sensors to monitor pH, temperature, and dissolved oxygen in kelp forests from Van Damme, CA to Ensenada, Mexico. This project utilizes the bandwidth of a citizen scientist diving organization to collect high-quality and high-resolution data on oceanographic conditions along the California coast. This work hopes to provide insight into the dynamics of climate change along our coast, identify factors influencing the risk or resilience of commercially and economically important marine species, and inform future models integrating citizen science programs with academic scientists.

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Purple urchin grazing & OCEAN upwelling

With a rapidly changing climate, understanding how environmental drivers alter the balance between grazing rates and primary productivity is going to be key for conservation and management efforts. My research aims to understand the extent to which coastal upwelling may allow for recovery of kelp forest ecosystems by reducing grazing of the dominant barren forming species along the US West Coast, the purple sea urchin, Strongylocentrotus purpuratus. Using our experimental system, I will manipulate pH, Temperature, and Dissolved oxygen to simulate different intensities of upwelling. I will expose purple sea urchins to these different upwelling intensities and perform grazing assays to calculate sea urchin grazing rates. This information will be critical for the recovery of kelp forests along the US West Coast, as upwelling is predicted to increase in intensity and duration with worsening climate change. 

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Infectious disease, global change, and kelp forest ecology

Global change can alter the relationships between pathogens and their hosts, with consequences for population and ecosystem-level dynamics. We are investigating the causes and consequences of disease-related mortality in the purple sea urchin, Strongylocentrotus purpuratus, which can reach high densities and overgraze kelp forests, transforming them into low-diversity “urchin barrens.” Large epidemics can suppress urchin populations low enough to result in kelp recovery, but the circumstances under which this occurs are not well understood. Through lab experiments, field work, and long-term data analysis, we are asking how we can expect urchin populations and their diseases to respond to their altered environment, affecting the fate of kelp forest habitats in California and beyond.

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Pycnopodia & sea urchin interactions

Predator control of grazers is vital for the maintenance of healthy kelp forests. While the top-down effects of predators like sea otters on kelp has been well studied, much is unknown about the effects other key predators, such as the sunflower star, on kelp. Sunflower stars may benefit kelp through direct consumption of grazers, or indirectly, by scaring herbivores and changing their behavior in ways that reduce kelp consumption. We are studying direct and indirect effects of sunflower stars on urchins in Southeast Alaska to gain insights into the role this species may play in kelp forest restoration.

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Seagrass & aquaculture interactions

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We are working with The Nature Conservancy and Hog Island Oyster Company to design a scientifically rigorous monitoring program than can document trends in eelgrass growth, as well as eelgrass-aquaculture interactions in the Tomales Bay operations of Hog Island Oyster Company. This project allows the team to study human-eelgrass interactions, by examining the impacts of aquaculture on eelgrass cover and density, and documenting ecological shifts associated with changes in eelgrass ecosystems. Ideally, results will assist in elucidating actual versus perceived environmental effects of shellfish culture on eelgrass habitats and estuarine processes, which will aid managers in the decision-making and permitting process involving shellfish aquaculture and facilitate more sustainable aquaculture practices. This can streamline permitting for both agencies and industry, and enable each to focus efforts appropriately on conservation.  Additionally, our lab is pairing surveys with unmanned aerial vehicles (UAVs) and traditional SCUBA surveys to test the applicability of UAV surveys in monitoring the extent and density of seagrass beds.  Ultimately, we are interested in understanding whether UAV surveys can be a cost-effective monitoring methodology for government agencies and stakeholders.

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Dungeness crab & domoic acid

Over the last decade, landings from California’s Dungeness crab fishery have totaled nearly 15 million pounds annually (CDFW, 2023). That’s an estimated 7.5 million adult male crabs brought to port and sold every year just in California! While Dungeness crab landings have been high throughout the state over the last decade, there exist burgeoning conservation and management concerns surrounding the health and long-term sustainability of this fishery stemming from anthropogenic changes in climate. For example, in 2015, the fishery experienced prolonged and costly delays associated with the onset of massive Pseudo-nitzschia harmful algal bloom (HAB), the extent and severity of which was unprecedented. Psuedo-nitzschia is genus of diatom (phytoplankton) found worldwide, with some strains capable of producing domoic acid (DA) under the “right” conditions. DA is a potent neurotoxin that can be harmful to marine vertebrates and humans when consumed in moderately high doses. While DA is typically screened for by managers with the California Department of Fish and Wildlife, several questions regarding the crab’s uptake and retention of DA remain unanswered, inhibiting our ability to plan for future HABs in the region. Thus, to help ready California’s Dungeness crab fishery for the climate changes that lie ahead, we seek answer the following research question: how long, and to what extent, do adult Dungeness crabs store domoic acid in their tissues under various temperature and oxygen regimes? To answer this question, we will conduct a large multiple-stressors experiment in the lab, manipulating live crabs’ exposure to “hot” (toxic) food under various controlled temperature and oxygen conditions.

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Temperate kelp forest community dynamics

Ocean change is anticipated to have significant impacts on the the interactions between consumers and their prey. Anticipated future ocean conditions are not only being hotter or more acidic but also shifting independently, to create novel combinations of ocean conditions never before experienced by ocean denizens. This will likely impact producers and consumers differently and influence consumer-resource interactions. To forecast these changes the Kroeker Lab is conducting field studies and laboratory experiments using the high-latitude kelp forests of Sitka Sound Alaska as a study system.

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WEST COAST HOTSPOTS & vulnerable species

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In order to provide West Coast managers and decision-makers with targeted analyses for management of the oceanographic and ecosystem vulnerabilities associated with ocean acidification, the KroekerLab is initiating an integrated analysis to identify the geospatial patterns of OA and interacting environmental stressors along the U.S. Pacific coastline. This work will consider where culturally, commercially, and ecologically valuable species are most vulnerable to overlapping environmental stressors, including OA, hypoxia and temperature stress. We also will work experimentally to determine the interactive effects of OA, dissolved oxygen, and temperature on Dungeness crab, which is an extraordinarily valuable commercial species on the West Coast and an organism of great interest to decision makers. 

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PAST PROJECTS

Global change & trophic interactions

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Global change can produce striking shifts in marine communities and ecosystems, yet our understanding of the mechanisms underlying these shifts is limited. Species interactions have the potential to mediate climate-driven changes in communities, and trophic interactions may be especially influential given their potentially cascading effects on community structure. By conducting a meta-analysis, the Kroeker lab is quantifying the individual and combined effects of ocean acidification and warming on predator-prey and herbivore-resource interactions. We are also characterizing the remaining variance in response among underlying studies according to the taxonomic groups and life-history stages of organisms examined, as well as key components of experimental design. Overall, this work will evaluate the generality and robustness of our current predictions of the emergent effects of global change on trophic interactions.

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Global change & kelp forest grazer energetics

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The balance between energetic gains (consumption) and energetic costs (metabolism) mediate the flow of energy through trophic levels and are crucial to maintaining ecosystem function. Therefore, a mismatch between the scaling of consumption and metabolism due to global change stressors could impact ecosystem stability. We are utilizing laboratory mesocosm experiments and field assays to assess the impacts of pH and temperature on consumption and metabolism of key kelp forest invertebrate grazers. Some of these grazing species, such as sea urchins, are known to play important roles in structuring kelp forest ecosystems and therefore changes to energetics could have cascading effects on reefs.

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Upwelling, Ocean acidification, and Foraging Behavior

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Recent research has found that the exposure of fish (and some invertebrates) to near-future ocean pH levels can result in changes in behavior such as larval homing, boldness, and response to predator and alarm cues through impaired cognitive function. However, the majority of this work has been conducted on tropical damselfish species and is limited to measuring the response of a species at the physiological or organismal level. Using mesocosm studies and behavioral assays, we are investigating the effect of low pH on a temperate surfperch species, Embiotoca jacksoni. We are exploring how effects of low pH on cognitive function and behavior may scale up to community-level changes in ecosystems by monitoring changes in ecologically important behaviors like foraging, which may impact predator-prey interactions. Additionally, coastal ecosystems can experience naturally variable pH due to oceanographic processes like upwelling, and we are investigating the role this natural variability may play in mediating the effects of future acidification.

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Seagrass effects on estuarine acidification

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Recent work has focused on the impacts of ocean acidification on a variety of organisms, and efforts are now shifting to define strategies for coping with the issue. Seagrass ecosystems have been highlighted as important “OA refugia” for their potential to buffer acidified waters. Our research focuses on identifying the conditions under which seagrasses can serve to mitigate acidification in estuaries. In collaboration with local stakeholders, we are doing a series of deployments of high-resolution sensors (pH, temperature, salinity, dissolved oxygen) and ecological monitoring in estuaries across California. Our efforts will link and compare carbonate-system dynamics at whole-estuary scales to dynamics at the scales of individual seagrass meadows. We are also actively collaborating with other seagrass researchers in Oregon and Washington to enable comparisons at broad geographic scales from a variety of estuaries.

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Local Adaptation and Evolutionary Rescue

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Using kelp perch as a model species, we are investigating the extent to which local adaptation to the mosaic of conditions along the Pacific Coast may provide populations with resilience in the face of global change. Local adaptation maintains genetic diversity at the species level, and this genetic diversity may translate into diversity in organismal response to climate stressors. Due to the so-called "portfolio effect" greater response diversity can increase the probability of adaptive evolutionary rescue in a species. In collaboration with the Bernardi Lab, we are using cutting edge analysis of next-generation sequencing data and controlled laboratory experiments to investigate the extent of local adaptation in this widespread species and identify potential pathways of adaptation to varying environmental conditions.

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High-latitude MACROALGAE iN LOW-PH WATERS

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The macroalgal communities which constitute temperate kelp forests are powerhouses of primary production, providing food and habitat for commercially important invertebrates and fish. The responses of both calcifying and non-calcifying macroalgae to global change stressors may thus have major bottom-up consequences for high-latitude reef ecosystem function and resilience. We used field studies and laboratory experiments to investigate the growth, physiology, chemical defenses and nutritional content of temperate macroalgae species in Southeast Alaska under current seasonal conditions as well as future projections of ocean acidification and warming.

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Acidification & pinto Abalone

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Southeast Alaska is the northernmost range for a variety of important grazer species, including pinto abalone. We are exploring how pinto abalone respond to seasonal changes in carbonate chemistry, as well as how their grazing behavior may change in future ocean conditions. Through analysis of abalone physiology and the nutritional content of key algal species, we hope to gain insight into how ocean acidification could affect northern abalone through their interaction with the algae they consume.

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The interaction of HERRING Roe and its habitat in future spawning conditions

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Our ability to predict the effects of climate change on vulnerable life stages of marine species requires a thorough understanding of the drivers of environmental heterogeneity and the identification of potential refuge habitats. During their spring spawn in the Gulf of Alaska, Pacific herring deposit adhesive eggs on a variety of marine algae and seagrasses, where the fertilized roe develop until hatch. We are using manipulative mesocosm systems to test whether these photosynthesizing substrates, which can modify the carbonate chemistry of their immediate environments relative to bulk seawater conditions, can mitigate the effects of elevated pCO2 and temperature on embryonic development and condition.

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PArtitioning effects of climate change stressors in intertidal ecosystems

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To uncover links and feedbacks between climate change, biodiversity loss, and the functioning of coastal ecosystems, the Kroeker Lab is collaborating with researchers at UC Irvine and San Jose State University to conduct in situ manipulations of pCO2 and temperature in high-latitude rocky shore habitats. This multi-year intertidal experiment uses novel, field tested techniques to quantify temporal dynamics of biotic and abiotic tidepool characteristics, the main and interactive effects of multiple stressors, and the degree to which alterations in ecosystem processes are due to direct (climate-mediated) versus indirect (biodiversity-mediated) effects of climate change. 

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Kelp, reef & climate change ecology network (KRACCEN)

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The Kroeker lab is examining the seasonal dynamics of benthic assemblages across the range of Macrocystis kelp forest ecosystems in North America - from Baja California to Southeast Alaska. By measuring the key environmental conditions, including temperature, ocean chemistry, nutrients and light, as well as ecological rates, such as primary productivity and consumption, at a variety of locations, our research aims to tease apart the relationships between multiple environmental drivers and ecological processes. This research is providing insight into the underpinnings of kelp forest ecosystem dynamics and the functional consequences of accelerating environmental changes. Beyond modeling the drivers of ecosystem dynamics in the field, we are also investigating how the diverse, multi-species assemblages of each field location respond to manipulative laboratory experiments (e.g., exposure to future ocean acidification scenarios). This design allows an exciting examination of the ecosystem dynamics at the leading edge of range shifts, where ocean acidification is likely to limit the temperature-driven expansion of many species. The spatially-extensive KRACCEN network will provide crucial insights into the linkages and feedbacks among multiple environmental drivers on ecosystem function in giant kelp forests throughout their range.

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