Ocean Food and Global Change
My work focuses in three primary areas: (1) The development of adaptation and mitigation technologies for marine aquaculture to help businesses prepare for current and impending global change. (2) The application of aquaculture methods towards the conservation of marine biodiversity through collaborations with marine resource managers. (3) Meeting the practical needs of the marine aquaculture industry through collaborative research and extension of scientific findings. Click here for links to my publications and learn more about my ongoing projects below:
|
Global change adaptation and mitigation technologies for marine aquaculture
Red abalone growth and age sequence from a display in Fort Bragg, CA. Abalone are slow growers and very long lived with some animals reaching up to 60 years of age in the wild.
L to R: Abalone can achieve large sizes in the wild, including this animal, one of the largest ever observed collected near the California-Oregon border in 1993. Coming across a well-camouflaged green abalone (Haliotis fulgens) during a dive in the Channel Islands.
L to R: Stacked market size abalone ready for sale at TCAF, spawning red abalone in a temperature controlled room for experiments, raising newly settled red abalone in an experimental culture system that I designed and built at the Bodega Marine Lab, which simulates future ocean acidification.
|
Abalone are unique and beautiful marine snails found throughout the worlds oceans. Valued as a seafood delicacy and prized for their stunning iridescent shells, the history of abalone's role in human society is complex, dating back at least 100,000 years. Humans harvest and propagate abalone on all of the worlds inhabited continents and abalone play important roles in many cultural traditions.
The California coast is home to 7 species of abalone, each of which were previously harvested as part of both recreational and commercial fisheries in California. Sadly, through a combination of overfishing, disease and the collapse of regional kelp forest ecosystems, abalone numbers are dwindling throughout the state and these fisheries are now closed. Farm raised abalone are the only source of abalone as seafood in California. In 2015, after completing my PhD, I was hired by The Cultured Abalone Farm LLC. (TCAF) based in Santa Barbara, CA to work with the company and collaborators to study the impacts of climate change on the commercial production of California red abalone (Haliotis rufescens). While I now work for the UC Davis Coastal and Marine Sciences Institute, I actively collaborate with company GM Doug Bush and other staff at TCAF on projects investigating what successful abalone aquaculture and conservation will look like in a changing ocean.
My interdisciplinary research with the company has largely though not exclusively focused on the process of ocean acidification or “OA.” As a result of humanities carbon emissions through the burning of fossil fuels, a large-scale change in ocean chemistry is taking place as increasing concentrations of carbon dioxide are being absorbed by the oceans. OA refers to the increasing acidity, or conversely the decreasing pH of the global ocean resulting from this process. Scientists have discovered that the decreasing pH of the ocean negatively affects the growth and survival of many calcifying marine shellfish . Building on my PhD training and background in the biological impacts of OA (Swezey et al., 2017) I have been working with TCAF, The BOAR Group, Dr. Kristin Aquilino, Dr. Sara Boles, Dr. Andrew Whitehead, Dr. Laura Rogers-Bennett and PhD student Isabelle Neylan to lead research on pressing scientific topics pertaining to the biological impacts of OA on commercial abalone production, with a focus on adaption options for this stressor's acute impact on abalone's early life phases. |
Our experiments with red abalone examining the effects of both warming and acidification have shown substantial mortality and impacts to growth from both OA and temperature stress, mirroring impacts observed by growers over the last last decade. Through my work in this area, we have identified interventions that growers can make to stem these negative consequences including adult and juvenile feeding strategies, larval culture techniques and other hatchery buffering practices that may minimize impacts. Our work has also identified lineages of abalone which seem largely immune to the negative effects of these stressors. A central question raised by these findings is the extent to which adaptation and plasticity play roles in buffering abalone against global change. Wild abalone populations have experienced rapid declines throughout California in recent decades and as their numbers dwindle, concern is mounting regarding the remaining genetic variation that exists in extant populations, and whether such variation is sufficient to help both wild and captive populations persist under changing ocean conditions. Through the implementation of multi-generation culture experiments and experiments comparing the performance of different source populations under OA, my work is revealing that genetic variation does exist which could be harnessed for future breeding of climate tolerance. Components of this research were recently published in the Proceedings of the National Academy of Sciences (Swezey et al., 2020) and I am continuing to lead work in this area to develop new tools and adaptation/mitigation options for growers. I've been fortunate to receive funding for this work from NOAA, California Sea Grant and the California Ocean Protection Council and I have been invited to present this work at climate change and shellfish aquaculture meetings both domestically and internationally.
Applying aquaculture methods for the conservation of marine biodiversity
With collaborators Dr. Dan Okamoto at Florida State University (FSU), Dr. Laura Rogers-Bennett of the California Department of Fish and Wildlife (CDFW) and Dr. Rachel Simmons of UCSB, I am co-leading recently funded research to quantify how marine heat waves impact populations of purple sea urchins as part of a NSF funded multi-campus research collaborative between BML, FSU, UCSB and the Hakai Institute of British Columbia. From 2014-2017, a historic marine heatwave enveloped regions of Northeast Pacific ocean, an event which later became known as “the warm blob.” This warm water event coincided with a substantial increase in the population of purple sea urchins (Strongylocentrotus purpuratus) along the North Coast of California and the collapse of a major urchin predator, the sunflower star (Pycnopodia helianthoides) triggered by the spread of seastar wasting disease, a virus which decimated seastars along the west coast.
|
L to R: Diver surveys an urchin barren, culturing urchins under temperature and pH treatments in experimental aquaria at the Hakai Institute (top), a ripe freshly harvested purple sea urchin cultured for commercial sale (bottom).
Newly constructed temperature controlled flow through aquaria which I led the design of with collaborators, built for ongoing experiments with purple sea urchins, abalone and other aquaculture raised species at the UC Davis Bodega Marine Laboratory.
|
|
With the main historical predator of sea urchins having been hunted to local extinction on California's North Coast in the 1800's (the Sea Otter, Enhydra lutris nereis) and sunflower stars now absent because of disease, purple sea urchin populations expanded unchecked, leading to the decimation of north coast kelp forests and a 90% reduction in kelp coverage through urchin over grazing. These events have triggered the formation of widespread "urchin barren" conditions, where normally healthy kelp forests are replaced by carpets of grazing sea urchins who devour existing kelp, impacting numerous species including abalone and rock fish that are adapted to normally plentiful kelp conditions. While many questions remain surrounding the causes and consequences of this dramatic change, our work seeks to forecast how sea urchin reproduction and survival may change under increasing ocean warming. As part of this project, I am co-leading experiments examining temperature effects on adult urchin gonadal development and larval urchin growth and development under marine heatwave conditions. Initial phases of the project were recently completed at the Hakai Institute on Vancouver Island BC, where I was a visiting scientist in 2021; a second round of experiments has recently commenced at the Bodega Marine Laboratory utilizing a new experimental mesocosm system that I designed and constructed with collaborators. With modeling expertise from Rachael Simmons and the Okamoto lab, we will use these data to parameterize predictive models, integrating marine heat wave simulations, field collected dispersal data, lab derived biological response data and ocean circulation parameters and to inform adaptive management decisions for urchin impacted regions of coastline. Additionally, with new funding from the Western Regional Aquaculture Center, together with colleagues from California Sea Grant, UC Davis, Oregon State University and Aquarange LLC., I am assessing techniques for the sustainable removal and “ranching” of purple urchins for seafood. Large scale efforts are now underway to harvest these animals from barrens and reproductively condition them for the sale as sushi grade uni, returning money from sales to support kelp restoration efforts. Tied to our research examining temperature effects on gonadal maturation, I'm investigating techniques for improving the ranching of these animals, including new diets and culture techniques to speed maturity and assist growers in this effort.
L to R: BML Scientist Dr. Kristin Aquilino and myself examining juvenile white abalone being raised for restoration at BML, adult white abalone at the Cabrillo Marine Aquarium in Long Beach CA, a stopping point where adult animals born at BML reside before being released back into the wild.
|
In collaboration with PhD student Evan Tjerdeema, Dr. Kristin Aquilino, Dr. Eric Sanford and Dr. Jim Moore of BML, I am studying the impacts of climate-disease interactions on the success of captive production and wild outplanting of white abalone (Haliotis sorenseni) under changing ocean conditions (Tjeerdema, Swezey et al., in prep). White abalone are a critically endangered abalone species endemic to Southern California with an active restoration program focused on producing animals for wild re-introduction based at BML.
|
Our research, focused on disease virulence under changing ocean conditions has identified that ocean acidification and warming act synergistically to impact this species, increasing mortality and vulnerability to withering foot syndrome, a bacterial pathogen of major concern in abalone aquaculture and conservation. Importantly, we've also observed variation in white abalone responses to these stressors, giving hope that wild white abalone may harbor variation enabling them to adapt to warming and acidifying conditions in southern California once they leave BML for re-introduction if disease transmission is unavoidable. Our work seeks to further optimize techniques for the culture of these animals in captivity and identify optimal out planting habitat for white abalone under NOAA’s recovery program for this ESA listed species.
Research to meet the practical needs of industry
I am currently leading California Sea Grant funded research to pioneer new seaweed propagation techniques in collaboration with Intertidal Seaweed Co., a private commercial seaweed harvest business based in Northern California. In partnership with the company, I have successfully piloted new vegetative propagation techniques for California Nori (Pyropia sp.) which avoids dependence on the intensive culture of Pyropia’s minute sexual life history phase. Culturing this phase is problematic in California due to the cost of labor in the state and the relative paucity of large sea water facilities needed for mass seed production. Promising initial results from this research (which is ongoing in 2022) hint at the feasibility of an alternative production model based on vegetative tank-based culture. |
L to R: Collecting wild Nori from the field in Bodega Bay CA, seeding culture rope to initiate growth trials.
|
Top to Bottom: Formulated abalone feed from Australia, giant California sea cucumber (Parastichopus californicus) feeding on detritus.
|
Persistent shortages of wild kelp along the California coast resulting from the historic marine heatwave of 2014-2017 represent a major threat to abalone aquaculture’s economic viability in the USA. Commercial kelp harvests have traditionally served as the essential feed source and backbone of abalone aquacultures profitability in California and ongoing collapses of this resource are challenging both the commercial and conservation aquaculture of abalone species on the west coast. In 2023, in partnership with the Kashia Band of Pomo Indians, researchers at California Sea Grant and the UC Davis Department of Food Science and Technology, I am launching new work supported by NOAA Fisheries to test the utility of formulated feeds composed of milled and dried grape pomace meal, derived from California winery waste for use as a kelp-alternative in adult abalone production. Building on promising pilot results, our experimental diets will maximize the use of agricultural residues and test non-animal ingredient alternatives for the fish meal inputs traditionally found in abalone formulated feeds manufactured abroad. We will also pilot the experimental co-culture of abalone with native California sea cumbers (Parastichopus californicus), a widely popular seafood in Asian cuisine. There is growing interest in the commercial application of sea cucumbers as nutrient recyclers and processors of particulate waste in multitrophic aquaculture. Established co-culture systems utilizing abalone and sea cucumbers have been successfully implemented in land-based abalone aquaculture systems in Asia but not in the USA. As such, developing domestic sea cucumber production integrated with abalone aquaculture holds significant commercial potential. The development of sustainable formulated feeds and integrated multitrophic aquaculture systems are both critical frontiers in contemporary aquaculture research and I am excited to explore these areas in my continuing research. |
Publications:
Boles, S.E., Swezey, D.S., Aquilino, K.M., Stott, H.K., Rogers-Bennett, L., Bush, D., Sanford, E.D., Whitehead, A. Ocean acidification and settlement diet differentially affects two populations of red abalone (Haliotis rufescens). In review at Global Change Biology.
Neylan, I.P., Swezey, D.S., Boles, S.E. , Gross, J.A., Sih, A. and Stachowicz, J.J. Within and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival. In review at Global Change Biology.
Okamoto, D.K., Spindel, N.B., Collicutt, B., Mustermann, M.J., Karelitz, S., Gimenez I., Rolheiser, K., Cronmiller, E., Foss, E., Mahara, N., Swezey, D.S., Ferraro, R., Rogers-Bennett, L., and Schroeter, S. Thermal suppression of gametogenesis explains historical collapses in larval recruitment. In review at Communications Biology.
Swezey, D.S., Boles, S.E., Aquilino, K.M., Stott, H.K., Bush, D., Whitehead, A., Rogers-Bennett, L., Hill, T.M. and Sanford, E. (2020). Evolved differences in energy metabolism and growth dictate the impacts of ocean acidification on abalone aquaculture. Proceedings of the National Academy of Sciences of the USA, 117(42), 26513-26519.
Swezey, D.S., Bean, J.R., Ninokawa, A.T., Hill, T.M., Gaylord, B. and Sanford, E. (2017). Interactive effects of temperature, food and skeletal mineralogy mediate biological responses to ocean acidification in a widely distributed bryozoan. Proceedings of the Royal Society B: Biological Sciences 284.
Swezey, D.S., Bean, J.R., Hill, T.M., Gaylord, B., Ninokawa, A.T. and Sanford, E. (2017). Plastic responses of bryozoans to ocean acidification. The Journal of Experimental Biology. doi: 10.1242/jeb.163436
Wetzel, W., Lacher, I., Swezey, D.S, Moffitt, S., and Manning, D. (2012). Analysis reveals potential rangeland impacts if Williamson Act eliminated. California Agriculture 66(4), 131-136. Feature Cover Article. *Authorship order randomly selected; all authors contributed equally.
Sanford, E. and D.S. Swezey. (2008). Response of predatory snails to a novel prey following the geographic range expansion of an intertidal barnacle. Journal of Experimental Marine Biology and Ecology 354: 220–230.
Boles, S.E., Swezey, D.S., Aquilino, K.M., Stott, H.K., Rogers-Bennett, L., Bush, D., Sanford, E.D., Whitehead, A. Ocean acidification and settlement diet differentially affects two populations of red abalone (Haliotis rufescens). In review at Global Change Biology.
Neylan, I.P., Swezey, D.S., Boles, S.E. , Gross, J.A., Sih, A. and Stachowicz, J.J. Within and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival. In review at Global Change Biology.
Okamoto, D.K., Spindel, N.B., Collicutt, B., Mustermann, M.J., Karelitz, S., Gimenez I., Rolheiser, K., Cronmiller, E., Foss, E., Mahara, N., Swezey, D.S., Ferraro, R., Rogers-Bennett, L., and Schroeter, S. Thermal suppression of gametogenesis explains historical collapses in larval recruitment. In review at Communications Biology.
Swezey, D.S., Boles, S.E., Aquilino, K.M., Stott, H.K., Bush, D., Whitehead, A., Rogers-Bennett, L., Hill, T.M. and Sanford, E. (2020). Evolved differences in energy metabolism and growth dictate the impacts of ocean acidification on abalone aquaculture. Proceedings of the National Academy of Sciences of the USA, 117(42), 26513-26519.
Swezey, D.S., Bean, J.R., Ninokawa, A.T., Hill, T.M., Gaylord, B. and Sanford, E. (2017). Interactive effects of temperature, food and skeletal mineralogy mediate biological responses to ocean acidification in a widely distributed bryozoan. Proceedings of the Royal Society B: Biological Sciences 284.
Swezey, D.S., Bean, J.R., Hill, T.M., Gaylord, B., Ninokawa, A.T. and Sanford, E. (2017). Plastic responses of bryozoans to ocean acidification. The Journal of Experimental Biology. doi: 10.1242/jeb.163436
Wetzel, W., Lacher, I., Swezey, D.S, Moffitt, S., and Manning, D. (2012). Analysis reveals potential rangeland impacts if Williamson Act eliminated. California Agriculture 66(4), 131-136. Feature Cover Article. *Authorship order randomly selected; all authors contributed equally.
Sanford, E. and D.S. Swezey. (2008). Response of predatory snails to a novel prey following the geographic range expansion of an intertidal barnacle. Journal of Experimental Marine Biology and Ecology 354: 220–230.