Field work

Surveying ocean acidification on the Northwest Atlantic shelf

By Ewaldo Leitao.

In August of 2022, Prof. Samantha Siedlecki and Prof. Craig Tobias, along with students Halle Berger and Alex Frenzel, went on the East Coast Ocean Acidification Cruise (ECOA-3). The cruise was led by scientists at the University of New Hampshire, joined through transdisciplinary partnerships with other universities, aboard the NOAA Ship Ronald H. Brown. The UConn Avery Point members joined the cruise to investigate the contribution of sediments to carbon chemistry and how that ultimately impacts ocean acidification.

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“Core team” on the deck of NOAA Ship Ronald H. Brown with multi-core sampler. Left to right: Halle Berger, Samantha Siedlecki, Craig Tobias, Alex Frenzel

Sam, Craig, Halle and Alex were the sediment coring team. The cores go all the way down to the bottom of the ocean and collect both the upper part of the sediment and the layer of water above it. This way, it is possible to understand chemical reactions in this zone between the sediments and the water above it. “The idea here is to understand how sediments control the chemistry of bottom water. There are sediment reactions that could help buffer acidity. But it's unclear how sediments talk to the water above it or how that communication might change in the future” says Craig. You can learn more on the Facebook page of research vessel Ronald H. Brown.

These measurements are valuable information because they are not only timestamps of what is happening at the moment of collection. Increasing the number of observations and fine-tuning the measurements of these chemical processes in bottom waters helps the research of modelers, like Sam. Models are important to test our understanding of ocean processes. We need more measurements like this to more accurately predict marine climate change. Part of Sam’s work is to use this information into regional ocean models to better constrain the role of sediments in the chemistry of the ocean.

Graduate student Halle uses modeling to understand how ocean acidification and warming impacts marine animals like Atlantic sea scallops. “I learned a lot about how all the different carbonate system parameters are measured, and it was great to meet other students and scientists working on ocean acidification. We got to see some whales and dolphins, amazing sunsets and starry nights, and ate a lot of delicious food. My favorite memory was at one station where all the multi-corer brought up was a single hermit crab (no sediment at all). We named him Fred.”, said Halle.

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Sediment sample with overlying seawater and a white brittle star attached to the side of the tube

Alex-Frenzel-grabbing-a-core-on-the-deck-of-ship
Alex Frenzel (left) and Halle Berger (right) collecting a subsample of the core on the deck

This was the third ECOA survey, which only happens every four years. The cruise starts in Newport, RI, travels to Portland, ME and then continues on to Nova Scotia. Traveling the Gulf of Maine, Georges Bank, Long Island Sound, Mid-Atlantic Bight, Chesapeake Bay, and the South Atlantic Bight. Each of these regions has their own physical processes that affect ocean acidification in each region, such as the Gulf of Maine receiving cold waters from the northern Labrador current and freshwater from rivers. In each of these regions, ocean acidification will likely have different effects. In the South Atlantic Bight, coral reefs, soft bottom corals, and therefore fish abundance may decline with ocean acidification. To better understand and accurately predict the impact of ocean acidification in different ecosystems, it is important to continuously do these measurements in order to understand how processes are changing over time in such dynamic environments.

Shell recycling will help restore oysters in Long Island Sound

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On 6 October, Research Professor Z.Baumann surveys the wild oyster reef at Morris Creek, CT

By Elaina Hancock.

7 November 2022. An unexpected find of a healthy, well-established oyster reef tucked away in a shoreline park inspired UConn Marine Science researcher Zofia Baumann to study ways to help these vital ecosystem engineers make a comeback.

Oyster habitats were largely destroyed by development, over-harvesting, and pollution, but in Long Island Sound, their numbers might be on the rise. Baumann and others hope to help restore Connecticut’s oyster populations.

Oysters build habitats where many species flourish, they improve water quality and make shorelines more resilient to erosion, but they need old shells to start building on. The site that became the focus of the project is one where oyster shells were deposited. Unfortunately, there is a shortage of shells in Connecticut and addressing this problem is the primary goal.

The project brings together members of the community, shellfish farmers, and regulators, as Baumann says, this effort relies on the community, otherwise, it will not work.

The Arctic is not so Boron!

Professor Penny Vlahos investigates what happens with the ocean chemistry at the marginal ice zones in her recent publication

By Ewaldo Leitao.

The Arctic Ocean is undergoing rapid changes due to climate change. Increasing temperatures result in decreasing sea-ice extent, constant decreasing and thinning of permanent sea-ice caps. Some projections even show a completely ice-free Summer by 2050!

Another consequence of climate change is ocean acidification due to increasing atmospheric CO2. That leads to the decrease in water pH and changes in carbon chemistry dynamics. The Arctic may be a small ocean (3% of total oceans area) but it has an important contribution to carbon uptake (10%). Therefore, it is necessary to understand the impact of these changes across the oceans, including the Arctic, in order to be prepared for it.

Some chemical elements, such as boron, contribute to the ocean’s capacity to resist changes in pH, that is ocean’s alkalinity. Boron, in combination with salinity, has been used as a universal rule in the open ocean (boron to salinity ratio) in order to understand the contribution of boron to alkalinity, and therefore ocean carbon chemistry. But how does that change in the less saline areas, such as the marginal ice zones of the Arctic?

In the recent paper published in Nature Communications, Prof. Penny Vlahos and graduate student Lauren Barrett observed that, when measured in low salinity areas (marginal ice zones), the boron to salinity ratio deviates from the expected in open oceans. In a cruise that took place in May of 2021 (you can read more about the cruise here), researchers were surprised to find significant deviations in the boron to salinity ratios in ice and brine samples. Lower water temperature and lower salinity alters the exchange between boric acid and borate, which is used to determine the contribution of boron to sea water alkalinity (capacity of water to resist changes in pH and acidification), driving this deviation of the boron to salinity ratio compared to open ocean waters.

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Prof. Penny Vlahos (right) with graduate students Lauren Barrett (left) and Emma Shipley (middle) on board the RV Sikuliaq

Boron-concentration
Stations sampled on the RV Sikuliaq between May 20th to June 14th, 2021.

The unique microenvironment of the marginal ice zones creates a very dynamic system. As seawater freezes, salts are rejected, but there is still a liquid region between ice crystals, called brine channels. These channels allow boron to undergo inorganic changes that may result in the variations observed in some of the samples, increasing the variability of boron to salinity ratio observed in these Arctic areas.

Prior to boarding the research vessel, researchers had to quarantine for two weeks. But this was a valuable time to Lauren Barrett. “Over quarantine I spent a lot of time reading about the various uncertainties that other authors encountered in accurately and precisely constraining the carbonate system in this highly heterogeneous environment. The boron to salinity ratios that we present here warn against applying universal ratios constrained in the open ocean to marginal ice zones and ice environments.” says Lauren.

Penny Vlahos Arctic
Lauren making a snowman at one of the stations that was ice covered, with the RV Sikuliaq on the back.

Lauren also shared a little bit about her experience: “I am very grateful for the opportunity to work with our international coauthors. The collaborative and interdisciplinary nature of marine science is one of my favorite aspects of working in this field. This research cruise was a great experience both personally and professionally, and I continue to be grateful to work in a field where cruising and getting to see polar bears is all in a day's work.”

The Arctic is an important sink of carbon and yet highly susceptible to climate change. Therefore, understanding detailed information of this system, instead of applying universal ratios, is necessary in order to better understand the carbon chemistry of the Arctic and be prepared for the consequences of climate change.


Vlahos, P., Lee, K., Lee, CH., Barrett, L, and Juranek, L. (2022) Non-conservative nature of boron in Arctic marginal ice zones. Nature Communications Earth & Environment 3, 214