I am a biogeochemist, which means I use the techniques and principles from chemistry to study coastal ecosystems. It also means that I collaborate with many other scientists who have knowledge and expertise in marine biology, marine ecology, sensor development, and physical oceanography. I use many tools to conduct my research, ranging from small boats and SCUBA equipment to laboratory equipment for seawater analysis to numerical models run on computers. Keep reading to learn a bit more about my recent research projects.
You can also find me on Google Scholar where you can see an up-to-date list of publications and citation metrics.
Coral reefs are some of the world's most beautiful and productive marine environments. They harbor ~25% of marine biodiversity and support coastal communities by providing storm protection, food security, economic opportunities through fishing and tourism, and by providing cultural and aesthetic value. Yet coral reefs are under threat from rising sea surface temperatures and ocean acidification brought on by climate change. Local stressors, such as overfishing, nutrient pollution, and habitat destruction, are also threatening reefs.
I study the interactions between the chemistry, biology, and physics on coral reefs to better understand how coral reefs are changing and how to protect them in the future. As a biogeochemist, I take a systems-level view, focusing on ecosystem metabolism on coral reefs (net photosynthesis and net calcification) because these rates are diagnostic of ecosystem-scale, instead of organismal, processes. I have led projects on Palmyra Atoll and American Samoa with Rob Dunbar to measure ecosystem metabolism and understand its controlling factors in relatively undisturbed settings. I have collaborated with Rebecca Albright, Ken Caldeira, and Yui Takeshita to study the effects of ocean acidification on coral reef calcification on an unconfined, natural coral reef (papers forthcoming).
I have also worked with Justin Rogers and Stephen Monismith to study the physical oceanography of coral reefs. The water motion (currents, waves, tides) on coral reefs, called the hydrodynamics, sets the backdrop for the myriad biological and chemical interactions to occur. Another way to think about this is that the hydrodynamics set the "stage" across which the "actors" (coral reef organisms) allow the "play" (ecosystem metabolism and biogeochemical fluxes) to unfold.
I use biogeochemistry to study kelp forests as well as coral reefs. In conjunction with Kerry Nickols, Steve Litvin, Paul Leary, Tom Bell, and others, I led a year-long study which documented biogeochemical variability in a central California kelp forest. This was the first study to document long-term carbonate chemistry dynamics in a central California kelp forest. We found highly variable biogeochemical conditions within different portions of the kelp forest, separated by only a few hundred meters, and investigated the combination of physical oceanographic and biological factors that gave rise to the observed variability. We considered what this means for monitoring these critical coastal ecosystems in the future. We plan to expand this study to investigate the diel cycle of the same central California kelp forest in forthcoming papers.
I am also interested in kelp forest carbon cycling. Much remains to be known about the fate of kelp-derived blue carbon. Beach wrack, or kelp deposited onto the beach during storm events, plays a largely unknown role in kelp forest carbon cycling. In the coming years, I plan to conduct respiration chamber studies to quantify the role of kelp beach wrack respiration as a loss pathway in the kelp carbon cycle.
Coastal ecosystems face many demands and pressures. Locally, nutrient pollution, overfishing, and habitat destruction are fundamentally changing coastal ecosystems and degrading their ability to provide critical services to coastal communities. Globally, rising sea surface temperatures and ocean acidification are threatening coastal ecosystem resilience. Together, this combination of local and global factors makes a very potent, and dangerous, mix of stresses on coastal ecosystems. I am passionate about translating the science of coastal ecosystems into solutions to sustainably manage, protect, and restore these ecosystems. Solutions-based science will be a major thrust of my research in the future. Here are some complementary projects that illustrate my interest in solutions-based science for the coastal ocean.
I am interested in exploring whether strategic bubble releases can alleviate nighttime acidification in coastal ecosystems. My modeling results suggest that bubbling can be 1-2 orders of magnitude more effective at ventilating coastal ecosystems than are natural processes alone. Future field studies will build on the modeling results to test this hypothesis in real-world coastal ecosystems.
Seagrass meadows have gained increasing attention in the last several years as a possible solution to mitigate coastal acidification. Yet much remains unknown about the potential for seagrass meadows to act as localized buffers, capable of changing their local chemistry and creating more favorable conditions for calcifying organisms such as coral and oysters.
In the fall of 2016, I joined a west coast working group led by the Bodgea Ocean Acidification Research group at Bodega Marine Laboratory to investigate the feasibility of using seagrass meadows as local acidification buffers. Together, we built computer models to simulate the feedbacks between seagrass ecosystem metabolism and overlying water chemistry in order to better quantify the range of possible buffer effects expected in seagrass meadows. We used computer simulations to quantify how much we expect seagrasses to buffer against ocean acidification and understand the factors which lead to more or less buffering. We hope that this work will help ecosystem managers make more informed decisions about expected acidification buffering by seagrasses. This work is currently under review for publication.
Low oxygen concentrations, or hypoxia, in coastal ecosystems can have detrimental or lethal effects for most marine organisms, including fish kills. Most efforts to combat hypoxia focus on controlling nutrient inputs to coastal ecosystems since these nutrients inputs are responsible for the eutrophication that drives hypoxia. While reductions in nutrient inputs are the ultimate goal for coastal hypoxia management, nutrient reductions are often too difficult and slow. In these situations, direct hypoxia mitigation may be a useful tool to aid in coastal management.
Artificial downwelling is a technique to pump surface water to depth. This approach has significant potential to mitigate hypoxia in coastal marine and aquatic ecosystems by forcing oxygen-rich surface waters to depth where they can replenish oxygen-depleted bottom waters. Our current understanding of artificial downwelling is still largely conceptual, with little understanding of the biogeochemical and physical factors that will determine its efficacy. I have completed some numerical modeling that indicates that artificial downwelling is more energy-efficient than traditional aeration techniques and am planning field studies to commence in spring 2018 to test the effectiveness of artificial downwelling at alleviating hypoxic conditions. Stay tuned for exciting progress on this project!
I have been several "blue water" (or open ocean) research experiences in addition to my coastal ecosystems research. In 2013, I was involved in the TRACERS (TRacing the fate of Algal Carbon Export in the Ross Sea) program to study the role of the Ross Sea in the global carbon cycle. From 2009-2011, I was involved with the Oceanic Flux Program time series to characterize the fate of marine sediment in the Sargasso Sea.