I am trained as 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. Now I combine all of these tools to design solutions to protect marine environments. 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.
Most (~2/3s) of my research focuses on developing solutions to meet the demands and pressures coastal ecosystems now face. At a local scale, 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, ocean acidification, and sea level rise are creating a potent cocktail of threats to coastal ecosystem resilience. Together, this combination of local and global factors makes for a dangerous mix of stresses on coastal ecosystems. I apply the knowledge I gained from years of studying how coastal ecosystems function into designing solutions to sustainably manage, protect, and restore these ecosystems. Most of my research is currently focused on engineering ecosystems to avoid the dangers of ocean acidification and hypoxia (low oxygen). But I get really excited about all sorts of new solutions-oriented ideas and perspectives, so if you have an idea to discuss, get in touch!
I am interested in exploring whether air bubbles (yes, you read that correctly) can alleviate nighttime acidification in coastal ecosystems. My modeling results suggest that bubbling air can be 1-2 orders of magnitude more effective at ventilating dissolved carbon dioxide from seawater 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 am working with colleagues Clara Garcia-Sanchez and Ken Caldeira to develop models that allow us to understand the potential and limits of artificial downwelling. I am planning a field experiment in the summer of 2018 to investigate its potential in a real aquatic ecosystem. Stay tuned for exciting progress on this project!
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 design solutions 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. I have also started to explore how new isotopic tracers may help us identify the role of different members of the coral reef community in contributing to ecosystem metabolism.
Finally, I have ongoing collaboration with physical oceanographic colleagues 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. Studying kelp forests along the California coast provides me with cold water analogs to tropical coral reefs and helps build my comparative understanding of the similarities and differences across coastal ecosystems. 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 studying the fate of kelp carbon, both for its potential in providing local acidification buffering as well as its potential to sequester carbon from the atmosphere. Much work remains to close the gaps in our knowledge about kelp-derived carbon. For instance, beach wrack, or kelp deposited onto the beach during storm events, plays a largely unknown role in kelp blue carbon loss. Constraining this loss pathway, along with other critical kelp carbon pathways, such as deep ocean deposition, will be critical to understanding the role of kelp forests in local, regional, and possibly even global carbon cycling.
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.