Kelp, reef & climate change ecology network (KRACCEN)
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.
Detecting 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.
WEST COAST HOTSPOTS & vulnerable species
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.
Global change & trophic interactions
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.
Global change & kelp forest grazer energetics
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.
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.
Upwelling, Ocean acidification, and Foraging Behavior
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.
Seagrass effects on estuarine acidification
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.
Local Adaptation and Evolutionary Rescue
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.
High-latitude MACROALGAE iN LOW-PH WATERS
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 are using 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.
Acidification & pinto Abalone
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.
The interaction of HERRING Roe and its habitat in future spawning conditions
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.
PArtitioning effects of climate change stressors in intertidal ecosystems
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.