sand lance

“Just keep swimming: challenges in PhD research”

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The ole adage holds true for DMS graduate student Emma Siegfried’s first experiments on a new species of sand lance

 

By Samantha Rush and Hannes Baumann

In 1984, the late Alphonse Smigielski and colleagues published a research paper that showed how American sand lance (Ammodytes americanus) could be successfully spawned and reared in the laboratory. Now, DMS PhD student Emma Siegfried is working to continue experimental research on this species, finding that revisiting the 40 year old study is not without challenges.

Sand lances are so called forage fish, meaning that their role in the ecosystem is to eat tiny planktonic organisms while being important food themselves for higher trophic animals such as other fish, seabirds, and marine mammals. Despite their importance, there is insufficient information about how this species will cope to climate change, particularly during the most sensitive larval and embryo stages. To fill this knowledge gap, Emma’s work focuses on exploring how increasing water temperatures and carbon dioxide (CO2) levels affect sand lance embryos and larvae.

Previous research conducted in Prof. Hannes Baumann’s Evolutionary Fish Ecology lab discovered that embryos of the closely related Northern sand lance (Ammodytes dubius) are extremely sensitive to elevated CO2 levels, as they are projected to occur in future oceans. However, whether American sand lance are equally CO2 sensitive is not known.

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On October 2nd 2024, Emma Siegfried looks at the beach seine stretched across the sand at low tide in Wells Harbor

American sand lance collected in Wells, ME, are being transported in a cooler to the Rankin lab at UConn Avery Point

Emma’s thesis research began in 2024 by first trying to find a reliable and easy to access location, where the species could be found and collected. In the harbor of the Wells National Estuarine Research Reserve in Wells, Maine, she found what she needed, because her fish occurred in high numbers there and could be sampled at low tide easily via beach seine. Now Emma’s goal was to catch the fish as close as possible prior to their spawning season, which in the case of sand lance starts with the beginning of winter.

In late August and early October 2024, Emma and her lab mates successfully collected sand lance and transported them live to the Rankin Seawater at Avery Point. There, however, sand lance proved challenging to care for, as they prefer spending days to weeks burrowed in sand (hence their name), making it difficult to monitor their health and development. Subsequent sampling efforts in November and early December brought a new set back, because the previously accessible population in Wells Harbor had evidently moved into slightly deeper waters and thereby out of reach for the beach seine. Unfazed, Emma proceeded to rear the fish she already had in the lab, hoping that they would ripen and eventually produce embryos for a CO2-sensitivity experiment.

At first, this looked like another failure. Sand lance use the declining temperature as a cue to ripen, but the waters of eastern Long Island Sound that flow through the Rankin lab remained unseasonably warm well into December. Eventually, however, on 23 December 2024, water temperatures crossed the critical 7°C threshold, and 3 days later, Emma and her lab mates indeed succeeded in strip-spawning a few ripened up females! The fertilized embryos were then placed in the Automatic Larval Fish Rearing System (ALFiRiS) that allows computer-controlled exposure of organisms to different temperature and CO2 conditions.

On 26 December 2024, Hannes Baumann, Emma Siegfried, and Lucas Jones lift a bowl of sand out of the big circle tank to look for buried sand lance.

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25 days old embryos of American sand lance developing slowly at 8 degrees celsius

Unfortunately, more experimental setbacks followed. Less than 1% of the embryos actually developed to hatch, the CO2-induced acidification did not produce the desired target pH levels, and a system malfunction remained undetected long enough to raise water temperatures to unnatural levels. Emma remains positive, however, and looks at her trials and tribulations as well as the preliminary data as a valuable exercise in gathering experience with this new, non-model species.

“Even though it didn’t go the way we expected, [we] still learned a lot.” she says.

She added that science is by definition challenging, but she is eager to apply what she has learned and move forward. More generally, her thesis research aims to answer the question whether CO2-sensitivity is a shared trait among sand lance species. To that end, she is applying for a grant to collaborate with researchers in Bergen, Norway who have experience with another, closely related sand lance species (Lesser sand eel, Ammodytes marinus). She hopes to secure funding to travel and conduct research there from December 2025 through March 2026.

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Under Ocean Acidification, Embryos of a Key Forage Fish Struggle to Hatch

A potential ripple effect from carbon in the atmosphere could have severe impacts throughout the ocean ecosystem

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This photo shows sand lance embryos that have and have not hatched. Sand lance have trouble hatching at future ocean CO2 levels (photo courtesy of Emma Cross).

By Elaina Hancock. Reposted from UConn Today, 7 April 2022

When carbon is emitted into the atmosphere, about a quarter of it is absorbed by the earth’s oceans. As the oceans serve as a massive ‘sink’ for carbon, there are changes to the water’s pH – a measure of how acidic or basic water is. As oceans absorb carbon, their water becomes more acidic, a process called ocean acidification (OA). For years, researchers have worked to understand what effect this could have on marine life.

While most research so far shows that fish are fairly resilient to OA, new research from UConn, the University of Washington, the National Oceanic and Atmospheric Administration (NOAA), and Southern Connecticut State University, shows that an important forage fish for the Northwest Atlantic called sand lance is very sensitive to OA, and that this could have considerable ecosystem impacts by 2100. The team’s findings have just been published in Marine Ecology Progress Series 687.

Sand lance spawn in the winter months in offshore environments that tend to have stable, low levels of CO2, explains UConn Department of Marine Sciences researcher and lead author Hannes Baumann.

“Marine organisms are not living in a uniform ocean,” Baumann says. “In near shore environments, large CO2 fluctuations between day and night and between seasons are the norm, and the fish and other organisms are adapted to this variability. When we stumbled upon sand lances we suspected they are different. We thought that a fish that lives in a more open-ocean offshore environment might be more sensitive than the near-shore fish because there’s just much less variability.”

The project was a collaboration with physical oceanographers, including Assistant Professor of Marine Sciences Samantha Siedlecki and Michael Alexander from NOAA’s Physical Sciences Laboratory in Boulder, Colorado, who modeled CO2 levels in 2050 and 2100 for a specific part of the Gulf of Maine where sand lance spawn. Then Baumann and his team reared sand lance embryos in the lab under experimentally higher CO2 levels matching the projected levels.

There are instances of direct fish mortality as result of elevated CO2, but they are rare, says Baumann. However, sand lance embryos proved to be exceptionally sensitive, and fewer embryos hatched under future oceanic CO2 conditions. The researchers repeated the experiments three more times to avoid jumping to conclusions but each time they observed the same result.

“We found that embryo survival-to-hatch decreased sharply with increasing CO2 levels in the water, concluding that this is one of the most CO2-sensitive fish species studied thus far,” Baumann says.

Sand lances are surely one of the most important forage fish here on the Northwest Atlantic shelf… The humpback whales, sharks, tuna, cod, shearwaters, terns — you name it — they are all relying on sand lance.

With this interdisciplinary approach combining model forecasts and serial experimentation the researchers arrived at a picture that is much more specific.

“We consequently applied principles of serial experimentation, which is a most timely and important topic in ocean acidification research right now,” Baumann says. “Because our findings are backed up by repeated independent evidence, they are more robust than many published ocean acidification studies to date.”

In addition to preventing many sand lance embryos from developing normally, the researchers document a second negative, and novel, response to elevated CO2. Higher CO2 levels appear to make it harder for embryos to hatch.

Baumann explains the lowered pH likely renders enzymes needed for successful hatching less effective, leaving the embryos unable to break through their eggshell (chorion) to hatch.

The results show that by 2100, due to acidification, sand lance hatching success could be reduced to 71% of today’s levels. Since sand lance are such a critical component of the food web of the Northwest Atlantic, this marked decrease in sand lance would have profound impacts throughout the ecosystem.

“Sand lances are surely one of the most important forage fish here on the Northwest Atlantic shelf,” Baumann says. “Their range spans from the Mid Atlantic Bight all the way to Greenland. Where we studied them, on Stellwagen Bank, they are called the backbone of the ecosystem. The humpback whales, sharks, tuna, cod, shearwaters, terns — you name it — they are all relying on sand lance, and if sand lance productivity goes down, we will see ripple effects to all these higher trophic animals. Even though we humans don’t fish for sand lance, we need to take care of the species because it has such a huge effect on everything else.”

Baumann says this study supports the hypothesis that offshore, high latitude marine organisms like the sand lance may be among the most vulnerable to OA. As a result, these organisms and food webs will likely be impacted first and soon, and we must act now.

Previous research has focused on opportunistically chosen species when testing their sensitivity for ocean acidification, says Baumann, but this should change.

“We need strategic thinking about what species we are testing next, because we cannot test every marine fish species, that’s an impossible task. We should concentrate on fish species that are likely the most vulnerable, and therefore the ones that are probably being affected first and this research makes a compelling argument that those are the fish species at higher latitudes and in more offshore than nearshore environments.”