Tessa Hill Wants to Save the Bivalves

The UC Davis oceanographer reconstructs ancient climate and studies the present impacts of global warming in an attempt to stave off environmental damage.

By Catherine Offord | July 1, 2016

© NAT AND CODY GANTZGrowing up on the Pacific coast, Tessa Hill developed a fascination with the sea and its wildlife. In the late ’90s, eager to see another part of the country—and another ocean—she moved to Eckerd College in Saint Petersburg, Florida, to study marine science. There, she became interested in the relationship between oceans and environmental change. “I wanted to learn more about the Earth’s climate system,” she says. “How it operated in the past, and how we might be modifying that system today.”

In 1999, Hill moved back west for a PhD at the University of California, Santa Barbara, where she worked with paleoceanographer James Kennett to document the contribution of ocean sources of methane to climate change throughout Earth’s history. “She’s very capable of choosing questions of major significance,” Kennett says of Hill, adding that on the methane project, “she just jumped right in.” During her dissertation work, Hill discovered that methane gas leaves a signature in the fossilized shells of Foraminifera—amoeboid protists found in marine sediments—that can be used to track changes in methane levels in the world’s oceans through time.1

Graduating in 2004, she moved to the University of California, Davis, to investigate more-current climate trends. “I was interested in asking questions about modern impacts on the ocean,” she says. “I think it’s hard to be a climate scientist studying Earth’s natural climate system and not start to wonder how we are impacting things.”

As a postdoc in the lab of biogeochemist Howie Spero, Hill measured shorter-term changes in oceanic environments via deep-sea corals, which show tree ring–like annual growth patterns. “Her research program was extremely successful,” Spero says, noting that it wasn’t long before UC Davis offered her a faculty position. Since then, he adds, “she’s really been the glue, so to speak, that’s held a lot of the research together at the frontier between earth science and biology.”

That research has been carried out on UC Davis’s campus and 100 miles west at the university’s Bodega Marine Laboratory, where Hill’s group reconstructs paleoclimates and assesses the effect of current and expected geochemical changes in the ocean on ecologically and commercially important members of marine communities.

In 2011, for example, her group showed that mussels grown in the lab in seawater containing CO2 levels predicted for 2100 made thinner, more fragile shells.2 And earlier this year, she and her colleagues found that when algae and seagrasses living in tidal pools switch off oxygen-producing photosynthesis for the night, the pools become corrosive to shell-growing animals, indicating that coastal creatures could become early victims of ocean acidification.3 Importantly, Hill says, “we’re starting to connect the dots between what we see in the lab and what we see in the real world.”

Beyond her academic research, Hill has also been recognized for her outreach work—she was named a public engagement fellow by the Leshner Leadership Institute at the American Association for the Advancement of Science in December—and collaborates not only with other scientists but with policy makers and aquaculture industrialists. In May, she visited the White House to receive a Presidential Early Career Award for Scientists and Engineers (PECASE) in recognition of innovative research and commitment to community service.

“I don’t really want to be in the business of documenting decline,” Hill explains. “Rather, I would like to do good science that can be used by people to make better decisions.” 


  1. T.M. Hill et al., “Foraminifera as indicators of methane-rich environments: A study of modern methane seeps in Santa Barbara Channel, California,” Mar Micropaleontol, 49:123-38, 2003. (Cited 80 times)
  2. B. Gaylord et al., “Functional impacts of ocean acidification in an ecologically critical foundation species,” J Exp Biol, 214:2586-94, 2011. (Cited 115 times)
  3. L. Kwiatkowski et al., “Nighttime dissolution in a temperate coastal ocean ecosystem increases under acidification,” Sci Rep, 6:22984, 2016. (Cited 2 times)

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Avatar of: JonRichfield


Posts: 139

July 27, 2016

I (completely sincerely) applaud the quality of Tessa Hill's work and her success, and agree that the field of study is of radical importance. Nor do I suggest that Tessa is misrepresenting any of its implications, nor yet suggest that I know of any substantial objections to her findings, nor those of her co-workers.

However, there have been many reports from other sources (journalistic in particular, though some purported to be quoting research work directly) in which the inferences presented were of effectlively linear (or worse) extrapolations from moderate or implausible effects of existing conditions. The implications of these inferences, if they were to prove simply and accurately predictive, certainly would be serious, even disastrous. (No surviving reefs, no surviving shelled molluscs etc to paraphrase them a bit unkindly.) Again I must stress in context that I do not attribute anything of the type to Tessa et al, and do not ask her to defend anything of the type.)


There are many ranges of species of many types to which such studies are relevant, and many physiological variables that could affect the outcomes. The changes in pH and temperature for example, would be gradual in general. In the past there have been many such changes, some of them comparatively abrupt, some local. By and large, speaking simplistically, most effects seem to have been modest and temporary, rather than large-scale extinctions. (Of course, I am not speaking of gross pollution etc, but ocean-wide, or hemispheric atmopheric influences of eg CO2 and temperature changes.) 


It seems to me that in such circumstances one would expect effective and relatively rapid selection for adaption to such environmental changes where they begin to exert reproductive challenges; better control of pH or erosion of shell material in response to CO2, or better retention of endosymbionts in the face of rising temperatures for example.

Accordingly, what I would like to see would not be, not so much the effects of physiological challenges in the lab, nor the effects on the organisms demonstrated to be those worst affected in the wild (corroded shells, vulnerability to predation, respiratory problems, bleached corals etc) but studies on the affected populations (largely in the wild) that pay particular attention to those lines that are least affected by pH levels, temperatures, and sundry pollutants.

Plainly, any concerns about the future of our marine ecologies should address the capacity of the populations to survive or to recover from adverse effects, rather than the severity of the selection pressures on lines that succumb; the survivors rather than the failures are the ones on which our oceans' future depends. Any actions we might take, whether reactive or proactive, should reflect available evidence concerning the medium-term capacity of populations to resist such physiological genetic challenges.

Incidentally, I am not speaking of such examples as the Labrador cod banks, in which criminal over-fishing changed the ecology drastically for years at least, if not permanently (I have not been keeping track) and where the new conditions were allegedly acceptable to some parties because other types of fishing (crabs etc) became more profitable. What I have in mind is where the ecology survives with essentially little change, because of the genetic resilience of the populations.

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