Above Photo by Meghan Zulian. Mineral layers of a white abalone shell at 5000x magnification viewed through Scanning Electron Microscopy.
Evaluating California’s Ocean Acidification and Deoxygenation Monitoring Networks
Photo of Meghan alongside other scientists, cruise coordinators, and the captain of RV Fulmar during an Applied California Current Ecosystem Studies (ACCESS) Cruise; one of very few long-term monitoring programs along the West Coast that coordinates biological and chemical sampling.
Many coastal benthic invertebrates are vulnerable to ocean acidification and deoxygenation. To understand how marine invertebrates are impacted by changing ocean conditions in real time, we need oceanographic data that captures what they experience throughout their journey from itty bitty larvae to through adulthood. Using the Multistressor Observations of Coastal Hypoxia and Acidification (MOCHA) dataset, my research asks:
1) How do exposure and vulnerability to ocean acidification and deoxygenation in the last decade differ among six ecologically and economically important benthic invertebrates (Dungeness crab, Pink Shrimp, California Spiny Lobster, Red and Purple Urchin, California Warty Sea Cucumber) throughout their life history?
2) What monitoring gaps create high uncertainty in these calculations and in turn,
3) What additional monitoring could improve our understanding of their exposure and vulnerability to OAH?
Publications on, or related to this work
Kennedy, E.G., Hamilton, S.L., Walker, B., Kroeker, K., Sanford, E., Zulian, M., Gaylord, B., Hill, T.M. The geography of multivariate stress to California Current shellfish reveals that hotspots and refugia are robust despite high levels of uncertainty. In prep for PLOS ONE.
Zulian, M., Kennedy, E.G., Hamilton, S.L., Hill, T.M., Ricart, A.M., Grisby, G.V., Sanford, E., Delgado, M., Ward, M., 2024. Assessing benthic invertebrate vulnerability to ocean acidification and hypoxia in California: The importance of effective oceanographic monitoring networks. In revision at PLOS One.
Kennedy, E.G., Zulian, M., Hamilton, S.L., Hill, T.M., … 2024. A high-resolution synthesis dataset for multistressor analyses along the US West Coast. Earth System Science Data, 16(1), pp.219-243.
Hamilton, S.L., Kennedy, E.G., Zulian, M., Hill, T.M., … 2023. Variable exposure to multiple climate stressors across the California marine protected area network and policy implications. ICES Journal of Marine Science, 80(7), pp.1923-1935.
Influence of growth rate, and impact of climate stressors on shells of juvenile white abalone
If you can’t measure oceanographic conditions directly, you may be able to estimate exposure to stressful conditions by examining calcified structures (i.e., shell, carapace). Conditions mimicking future ocean acidification are shown to reduce shell growth, thickness, and organization of the crystal structure and even compromise the organic layers protecting shells (periostracum). However, few studies have examined the impacts of multiple stressors on shell structures. Using shells of critically endangered white abalone from mutli-stressor experiments conducted by collaborators at the captive breeding program, I ask:
1) Does the shell ultrastructure of white abalone reliably record exposure to warming temperatures and acidified conditions?
2) Do multiple stressors evoke a stronger response than individual stressors?
Before I could answer this question, I needed to conduct a baseline study on white abalone shells, as no one has previously examined their mineral layers closely and systematically. Below are some photos from those marvelous explorations.
Amidst this baseline study and conversations with the wonderful folks at the captive breeding program, I became aware they were also very curious about the influence of growth rate on white abalone shells in the absence of stressors. Currently, restoration efforts release juvenile abalone to the wild when they reach a size minima, which can happen at wildly different ages in organisms with, ergo, wildly different growth rates. As a short detour to my work, I am also asking:
2) How does growth rate influence white abalone shell structure in the absence of stressors?
This question is important for my work, as it helps me understand the influence of stressors on growth rate. It could also inform the creation of an age minima in addition to the current size cutoff for out-planting practices.
Photo of a live white ablaone (Haliotis sorensenii), a critically endangered marine snail. Photo cr: Beth Schlanker.
Photo of a juvenile white abalone shell with degraded periostracum (outer organic layer) under scanning electron microscopy.
Photo showing mineral layers of a white abalone shell. The “buildings” are aragonite platelets, and the “road” is massive arragonite, which is interspersed among platelets.
(Above) Figure showing the conceptual framework used to categorize programs.
Analyzing Institutional Supports for Community Engaged Graduate Scholarship
This generation of graduate scholars is unprecedented in the diversity of their identities, career prospects, and unwavering commitment to public engagement. In embodying practices that depart from anachronistic academic norms, this next generation of engaged graduate scholars faces appreciable challenges while navigating “institutional structures, policies, and practices that delegitimize their experiences, perspectives, and approaches” (Dobernek et al., 2017).
Thankfully, as more engaged scholars are making their way into faculty, administrative, and community practitioner positions in higher education, they are building infrastructure to support graduate students in cultivating “interdisciplinary and engaged models of scholarship that align with [scholars] values, help form their identities as scholar-advocates, and enable contributions to long-term societal change” (O’Meara 2008; Keeler et al., 2022). The relatively few publications on these programs describe the development of individual programs.
I am working on the first national synthesis of programs supporting community-engaged graduate scholars, focusing on university-wide, institutionally-supported programs with low entry barriers open to students from all disciplinary backgrounds. This work aims to provide institutions of varying resources & strengths with examples of how to balance their support for engaged graduate scholars and assesses whether current programs are likely to address known barriers faced by graduate scholars.
This work is done in collaboration with Michael Rios and Tessa Hill at the UC Davis Office of Public Scholarship and Engagement. If you think your program fits the above-mentioned criteria, and you do not see it here, and would like it to be included, please fill out this google form.
MSc Research
As photosynthetic and calcifying organisms, it is unclear how coralline algae will respond to rapid sea ice loss and acidification in the Arctic. Greater access to sunlight and carbon should benefit their growth, while low carbonate saturation, will lower growth and density of their skeletons. As the main “reef-building” organisms in high latitude environments, and a refuge for invertebrates in all life stages, it is important to understand how they are coping with the conditions.
In my Master’s research I used long-lived species of coralline algae, Clathromorphum compactum, to examine carbonate system dynamics in the Canadian Arctic Archipelago. Results of this research suggest that at sites where sea ice melts each summer, the growth-boost provided by the sunlight is outweighing acidification, at least for now. At sites where the algae are deeper, and intermittently covered by multi-year ice, they are not seeing extra sunlight, and they appear to be struggling with calcification.
Publications
Leclerc, N., Halfar, J., Porter, T.J., Black, B.A., Hetzinger., S., Zulian, M., and Tsay, A., (2022) Utility of Dendrochronology Cross-dating Methods in the Development of Arctic Coralline Red Algae Clathromorphum compactum Growth Increment Chronology for Sea Ice Cover Reconstruction. Front. Mar. Sci. 9:923088. doi: 10.3389/fmars.2022.923088
