Ocean Acidification

Hannes visits Emma’s sand lance experiment in Norway

Posted on March 9, 2026March 9, 2026 by Hannes Baumann

Austevoll, the world-famous marine research station, has also been PhD student Emma Siegfried's home for the past 2 1/2 months. Emma became the first US recipient of a European Union exchange fellowship (AQUASERV program) that covered the costs of her stay and her research in Norway. The goal of her project is to rear embryos of a local sand lance species, the Lesser sandeel Ammodytes marinus, under different levels of CO2 to then compare the results to what is already known for the Northern sand lance A. dubius on the western side of the Atlantic ocean.

Emma's experiment has been a success so far, thanks in no small part to the incredible help of our Norwegian collaborators. Every one at the station has been welcoming, friendly and eager to show us the large-scale aquaculture research on cod, halibut, haddock, plaice and many other fish species that is being conducted here every day of the year.

As we gape at the impressive tanks and installations, as we chat eagerly about deepening our collaborative ties and enjoy Norwegian hospitality and nature, we feel that this may indeed be the beginning of another great chapter of sand lance science to come.

Norwegian sand lance are hatching!

Posted on February 10, 2026February 10, 2026 by Hannes Baumann

By Emma Siegfried.

Austevoll, 10 February 2026. More than two months into my research stay here in Norway, things are going pretty well. Instead of one single experiment, we actually ended up running 3 separate experiments at once because the female fish took their sweet time to get ready to spawn.

As I learned, it is quite common in the tanks here that only a few females become ready to spawn at a time, which meant that a new trial had to be started again and again.

Our first spawn was now exactly 4 weeks ago, and I'm happy to report that our first embryos in the 10˚C treatment started hatching last week! Now we’re counting the larvae that are hatching each day, taking photos of them on the day of hatch and then also taking videos of their hearts to measure heart rate.

The hatchlings are then preserved, mostly in ethanol but also in RNAlater for potential further genomic and transcriptomic analyses.

Emma arrives in Norway to start sand lance experiment

Posted on December 18, 2025December 18, 2025 by Hannes Baumann

By Emma Siegfried

16 December 2025. Hi, Emma here reporting in from the Institute of Marine Research in Storebø, Norway! After a quick stop in Amsterdam, I landed in Bergen on Saturday morning. I grabbed a quick ferry to get over to the island and settled in over the weekend in one of the on-station residences. The area is pretty rural, but the surroundings are idyllic. The islands are exactly what you would expect to see out of a movie.

Yesterday, I was able to get a tour of the station, and the facilities here are incredible. If I had to estimate it’s probably 6 or 7 times the size of Rankin lab. The facility has been doing research on the early life history stages of Cod, Haddock and Plaice on top of previous work with Lesser Sand Lance (Ammodytes marinus) larvae, and as a result has some quite large broodstock tanks.

High CO2 tolerance of Black Sea Bass embryos / larvae – just out!

Posted on June 13, 2024June 13, 2024 by Hannes Baumann

12 June 2024. We are excited to share that Environmental Biology of Fishes just published our study on the CO₂ sensitivity of Black Sea Bass early life stages! The experimental work was part of Max Zavell's PhD-research and required the development of new approaches for obtaining spawning adults, new rearing methods, and new techniques for quantifying hatchlings and feeding larvae.

In the end, our research extends earlier experimental work to show that Black Sea Bass embryos and larvae are surprisingly tolerant to even extreme pCO₂ conditions - which means that this species is likely resistant to the direct (!) effects of ocean acidification. Scientifically, this is intriguing because it points to some form of pre-adaptation that adults confer to their offspring in a manner we just don't understand yet.

Congrats, Max, to another chapter of your thesis published!

A strong showing at the 47th Larval Fish Conference!

Posted on May 18, 2024May 18, 2024 by Hannes Baumann

17 May 2024. Members of our Evolutionary Fish Ecology Lab had a blast attending this years 47th Larval Fish Conference in Huron, OH. Hannes, Emma, Max and alumnus Chris Murray (now at WHOI), went on a road trip from Connecticut to Lake Eerie to present and learn about all things larval fish. On Tuesday morning, the conference crowd enjoyed excursion or recreation options, all the while catching up with good old colleagues and making new connections and friends. A particular achievement: each of us presented research on a different fish species; while Hannes showed the first data emerging from his sabbatical research on Chilean silversides, Emma talked about baby California grunion development. Max presented a poster and two talks, the first about CO₂ effects on the onset of schooling in Atlantic silversides and a second one one Black Sea Bass overwintering dynamics. Last, Chris Murray gave a fascinating first look into gene expression data from our most recent sand lance CO₂ experiment. All around, a strong showing of our lab!

Contributions from our lab to the 47th Larval Fish Conference in Huron, OH

Baumann, H., Gallardo, A., Gallardo, C., and Urbina, M. 2024. First evidence for countergradient growth variation in the Chilean silverside Odontesthes regia. Oral presentation

Siegried, E. and Johnson, D. 2024. Eyes bigger than your stomach: developmental inaccuracy in larval California grunion. Oral presentation.

Zavell, M.D., Mouland, M., Barnum, D., Matassa, C., Schultz, E.T., and Baumann, H. 2024. Overwintering dynamics of northern stock Black Sea Bass, Centropristis striata, juveniles. Oral presentation.

Zavell, M.D., O'del, J., Mouland, M., Webb, J.F., and Baumann, H. 2024. Ontogeny of larval schooling and effects of ocean acidification in Atlantic Silversides (Menidia menidia). Oral presentation.

Murray, C.S., Jones, L., Siegfried, E., Zavell, M.D., Baumann, Z., Wiley, D., Therkildsen, N., Aluru, N., and Baumann, H. 2024. Examining the effect of ocean acidification on hatching enzyme gene expression in Northern sand lance (Ammodytes dubius). Oral presentation.

NSF awards our collaborative sand lance grant!

Posted on June 24, 2023June 24, 2023 by Hannes Baumann

24 June 2023. We are overjoyed to be able to announce today that NSF's Division of Integrative Organismal Systems has awarded our proposed research to better understand sand lance CO2 sensitivity!

With a sense of pride and humility we will take on this intriguing case, follow it down some rabbit holes, while keeping in mind the big picture. This fall, our collaborative team will begin its renewed work, now on both congeneric sandlance species (Ammodytes dubius, A. americanus).

We already have two talented PhD students recruited to the task, Lucas Jones and Emma Siegfried. With curiosity and anticipation, we look forward to the next years of eco-evolutionary research on some of the most important forage fish species on the Northwest Atlantic Shelf.

Public Award Abstract
Ocean warming and acidification are direct, predictable consequences of man-made climate change with likely vast but still insufficiently understood consequences for marine life.

So far, most tested fish species appear only mildly sensitive to ocean acidification, but sand lances are an exception. Sand lances are small, eel-like, schooling fishes of enormous importance as food for marine fish, seabirds and mammals in temperate to polar ecosystems, and recent research conclusively demonstrated that many sand lance embryos have trouble developing and hatching under predicted future ocean conditions.

This project uses modern experimental and molecular tools to understand exactly WHY sand lance embryos are so unusually sensitive and which genes and enzymes are responsible for this. Genes will also reveal whether some specific genotypes are less sensitive to warming and acidification, which can then be used to predict whether the species could evolve to be more tolerant over time.

Another important objective is to test a closely related sand lance species to find out, whether the high climate sensitivity might be of general concern in this important group of forage fishes. This project combines innovative ecological, evolutionary, and genomic research to help society anticipate looming marine ecosystem changes in the 21st century, while equipping the next generation of scientists with the needed tools and expertise to succeed in the challenges ahead.

The project also creates opportunities for high school students from underprivileged Connecticut schools to accompany the team on sand lance sampling trips to Stellwagen Bank National Marine Sanctuary.

Technical Award Abstract
Two recent studies on Northern sand lance (Ammodytes dubius), a key forage fish on offshore sand banks across the Northwest Atlantic shelf (NWA), have robustly demonstrated that predicted future CO₂ conditions induce some of the most severe reductions in embryo survival and hatching success seen yet among tested fish species. This project has four objectives for revealing the mechanisms underpinning this unusual, high CO₂-sensitivity as well as the ubiquity and genetic basis of this phenomenon.

[1] For the first time, we will rear A. dubius offspring produced from wild spawners to late larval stages at factorial CO₂ × temperature conditions to test whether sand lance larvae are as CO₂-sensitive as embryos.

[2] For the first time, we will use transcriptomic tools (RNAseq, RT-qPCR) to elucidate mechanisms causing ‘CO₂-impaired hatching’, focusing specifically on hatching enzymes, to better understand a newly discovered mortality mechanism due to high CO2 in fishes.

[3] Modern genomic approaches (low-coverage whole genome sequencing; allele frequency shifts, relatedness analyses) will reveal whether high CO₂-sensitivity has a genetic basis in sand lance and could therefore evolve.

[4] And for the first time, we will extend CO₂ × temperature experiments to a congener, the American sand lance (A. americanus), which provides an important scientific contrast between nearshore vs. offshore species CO2-sensitivities and will yield critical insights whether high CO₂-sensitivity is a wider concern within the sand lance family.

Feeling the pulse of Mumford Cove

Posted on March 23, 2023March 23, 2023 by Hannes Baumann

23 March 2023. For almost 8 years now, the Evolutionary Fish Ecology Lab has conducted research in nearby Mumford Cove, a small, eelgrass covered embayment on eastern Long Island Sound. Using a set of battery-powered probes we have continuously measured temperature, pH, oxygen, salinity, and depth in 30 min intervals in the Cove - almost 120,000 times. This ongoing effort is not funded by any grant or institution; instead, it has been sustained over all these years by the firm belief in the prescient, if undervalued societal service of monitoring, an activity without short-term reward but important long-term benefits in understanding how ecosystems change on short and long time-scales. To commemorate the effort, we simply thought that it is time to show you some data, some pictures, and draw some early, cautious conclusions about the very interesting case of Mumford Cove. Have a look!

John and Hannes travel to Bermuda to install a new CO2 system

Posted on May 29, 2022June 11, 2022 by Hannes Baumann

29 May 2022. When in a few months researchers and students at the Bermuda Institute of Ocean Science (BIOS) begin using their new outdoor mesocosm facility, they can now manipulate and control the CO₂ levels in as many of 9 flow-through basins. The important new capacity of the system will allow realistic ocean warming and acidification experiments and has been the product of a wonderful collaboration between BIOS researcher Dr. Yvonne Sawall and our UConn Marine Sciences team consisting of John Hamilton and Hannes Baumann.

The newly developed system shares some of the design ideas with ALFiRiS, the factorial rearing system we developed and used over the past years at UConn's Rankin Seawater Lab. For example, we again developed and installed a central pH measurement hub that sequentially collects water samples via pumps from each of 12 independent basins, which is advantageous, because it only relies on a single, high-end pH sensor, therefore making measurements always comparable. Similarly, we are using LabView software (National Instruments) to switch pumps on and off and log, display, and graph the pH conditions in real time for researchers to have confidence in their chosen environmental parameters.

While most of the planning and design work was done remotely via frequent online meetings, Hannes and John worked with Yvonne during the past week at the BIOS station on installing and testing the systems major components. Working mostly out in the open under a warm and clear Bermudan sky was a particular treat of this assignment. Big shout-out, too, to facilities manager Kevin Hollis for his tireless onsite help!

Despite setbacks in form of supply chain delays and an unfortunate last moment COVID infection preventing team member Lucas Jones from traveling to Bermuda, soon the new outdoor mesocosm facility at BIOS will become operational and allow new and advanced kinds of experimental research on global change biology.

Hannes gives DMS Friday seminar on sand lance ecology

Posted on March 4, 2022March 4, 2022 by Hannes Baumann

4 March 2022. Hannes was the invited speaker at today's Friday seminar of the Department of Marine Sciences. His talk gave an overview of the research highlights of our multi-disciplinary and multi-institutional efforts to better understand basic ecological facts, population connectivity & structure, and the unusually high CO₂-sensitivity of sand lance embryos. The remotely given presentation was attended by 62 people, some of which listened in from as far away as Norway!

The talk was recorded and can be accessed via the public link below.

Baumann, H. 2022. The unusual ecology & climate sensitivity of sand lance, a key forage fish on the Northwest-Atlantic shelf. UConn Marine Sciences Friday seminar. Online. 4 March 2022.

The unusual ecology and climate sensitivity of sand lance, a key forage fish on the Northwest-Atlantic Shelf

No matter how you look at these small, slender-bodied fishes that at times live buried in sediment or emerge as dense pelagic schools, northern sand lance (Ammodytes dubius) easily awe even the most hard-to-impress scientist or naturalist. Their unusual behavior, patchy occurrence, and reproductive timing are paralleled by their extraordinary importance as forage fish that sustain well-known hotspots of iconic predators (cod, tuna, sharks, seabirds, whales) all across the Northwest Atlantic shelf. And yet, despite their recognized role as the ‘backbone’ of many shelf ecosystems, we still don’t understand many basic aspects of sand lance ecology, population structure and their vulnerability to manmade climate change. Over the past years, our lab has been working alongside other US and Canadian research groups on multiple sand lance projects that have produced stunning new insights into these enigmatic fish. This seminar will outline some of the highlights. We discovered that the seasonal growth of these fish relies heavily on the lipid-rich copepod Calanus finmarchicus and showed that after a dormancy period in summer they spawn on Stellwagen Bank for just a brief period at the end of fall. To resolve questions of connectivity between sand lance areas, we performed large-scale Lagrangian drift simulations that suggested areas of high, low and negligible retention of sand lance offspring and showed overlaps with planned offshore wind lease areas. A large collaborative effort succeeded in obtaining specimens from across the entire distributional range (Greenland to Mid-Atlantic Bight), and subsequent whole genome sequencing newly revealed a stark genomic differentiation between northern and southern population clusters. Last, we performed multiple years of rearing experiments on embryos that consistently showed an unusual sensitivity of sand lance to future, high CO₂ oceans. When coupled with regional, end-of-century pCO₂ projections we estimate that rising CO₂ levels alone could reduce sand lance hatching success to 71% in 2100 relative to today. Warming, acidification, and habitat exploitation therefore emerge as key factors lining up against the future productivity of this forage fish, which is so critically important across Northwest-Atlantic shelf ecosystems.

Video: A November day on Stellwagen Bank

ICES Journal of Marine Science publishes long-term fecundity study!

Posted on November 4, 2021November 4, 2021 by Hannes Baumann

2 November 2021. We are happy report that the ICES Journal of Marine Science just published the last major experimental paper on Atlantic silverside CO₂-sensitivity from our lab. Callie Concannon and co-authors report on two complementary, long-term rearing trials in 2015/16 and 2018/19, where silverside juveniles or newly fertilized embryos were reared under contrasting temperature and CO₂ conditions to maturity. This revealed negative effects of high CO₂ conditions on female fecundity, but only at the warm, not the cold temperature treatments (Fig. below). Our study and its data are novel, because they were generated by the first whole-life CO₂ rearing experiment of a fish and are the first empirical fecundity effects shown for a broadcast-spawning fish species.

The paper is also special to us, because its publication marks the erstwhile conclusion of our yearlong, NSF-funded efforts (OCE#1536165) to understand the CO₂ sensitivity and its mechanisms in this important forage fish and long-standing model in fish ecology and evolution. The project ran from 2015 - 2020, produced 15 publications, 2 book chapters, and over 40 presentations, while furthering the careers of a post-doc, a PhD student, 5 Master students and over 10 undergraduates.

Evolutionary Fish Ecology

Ocean Acidification

Hannes visits Emma’s sand lance experiment in Norway

Norwegian sand lance are hatching!

Emma arrives in Norway to start sand lance experiment

High CO2 tolerance of Black Sea Bass embryos / larvae – just out!

A strong showing at the 47th Larval Fish Conference!

Contributions from our lab to the 47th Larval Fish Conference in Huron, OH

NSF awards our collaborative sand lance grant!

NSF-ORCC (Organismal Response to Climate Change): Collaborative Research: Mechanisms underpinning the unusual, high CO₂ sensitivity of sand lances, key forage fishes on the Northwest Atlantic Shelf (#2307813, 2023-2026, $1,050,000)

Feeling the pulse of Mumford Cove

John and Hannes travel to Bermuda to install a new CO2 system

A first test of our flow cell

Hannes gives DMS Friday seminar on sand lance ecology

The unusual ecology and climate sensitivity of sand lance, a key forage fish on the Northwest-Atlantic Shelf

Video: A November day on Stellwagen Bank

ICES Journal of Marine Science publishes long-term fecundity study!

Contributions from our lab to the 47th Larval Fish Conference in Huron, OH

NSF-ORCC (Organismal Response to Climate Change): Collaborative Research: Mechanisms underpinning the unusual, high CO2 sensitivity of sand lances, key forage fishes on the Northwest Atlantic Shelf (#2307813, 2023-2026, $1,050,000)

A first test of our flow cell

The unusual ecology and climate sensitivity of sand lance, a key forage fish on the Northwest-Atlantic Shelf

Video: A November day on Stellwagen Bank

NSF-ORCC (Organismal Response to Climate Change): Collaborative Research: Mechanisms underpinning the unusual, high CO₂ sensitivity of sand lances, key forage fishes on the Northwest Atlantic Shelf (#2307813, 2023-2026, $1,050,000)