Publications

DMS Kayla Mladinich shows that bivalves can reject microplastics

8 November 2022. DMS is happy to share the latest publication by PhD student Kayla Mladinich, showing the surprising but good news that blue mussels and oysters appear not to ingest all microplastic particles floating in the water.

By Kayla Mladinich.

Oysters and mussels are filter feeders that draw particles in from the surrounding water to be eaten. These animals can select which particles are eaten or rejected depending on factors such as particle size and surface properties. This study was performed to determine what kinds of microplastics will be consumed or rejected by oysters and mussels. Both species rejected larger microplastics more than smaller microplastics and did not differentiate between different types of plastic polymers. The results suggest that oysters and mussels will not ingest all microplastics that they are exposed to in the natural environment!



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Kayla changing water and replenishing food for the animals.

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An oyster being exposed to microplastics in the laboratory. Microplastics are gently pipetted over the inhalant aperture (where oysters draw particles in) which allows the oysters to choose between drawing the particles in or not (Photo: Kayla Mladinich).

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Mladinich et al. ES&T (2022) Graphical abstract

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


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

MEPS-sandlance
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.”


DMS researchers contribute to study on copepod climate adaptation

One of the most difficult challenges facing scientists is predicting how organisms will respond to rapid global change. A collaboration between oceanographers at the University of Connecticut and evolutionary biologists at the University of Vermont is looking into how copepods (tiny crustaceans that rival insects as the most abundant animals on the planet) adapt to ocean warming and acidification. This requires understanding the underlying genomic mechanisms that allow these animals to adapt, and the constraints to adaptation. This study by Reid Brennan and collaborators is a lucid example of this approach, identifying sets of genes that are linked to copepod adaptation to stressful new environments, and showing that the ability of these animals to respond to changing conditions is challenged after prolonged adaptation. Therefore, there are limits to adaptation that can constrain the resilience of animal populations to environmental stress.



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DMS faculty contributes textbook chapter on Fish Ecology

3rd March 2022. DMS faculty Hannes Baumann contributed a chapter to the new textbook Marine Biology: a functional approach to the oceans & their organisms (Taylor & Francis), which has just been published. The chapter is based on Baumann's long-running class "Ecology of Fishes" (MARN4018/5018), touching on a large variety topics including fish evolution, zoogeography, metabolism, growth, reproduction & basic concepts of fisheries science. The book is geared towards advanced undergraduate and graduate students, stimulating interest while encouraging readers to seek out further in-depth sources.



"With about 28,000 known species, fishes make up more than half of all known vertebrates (Helfman et al. 2009). Over the course of their long evolutionary history they radiated in every conceivable aquatic habitat, from the open ocean and deep-sea trenches to shelf seas, estuaries and lakes, to rivers and the smallest streams and ponds. They are found in subzero Antarctic waters, altitudes of over 4,000 m and even acidic desert springs of > 40°C (Moyle and Cech 2004). The fascinating adaptations to these habitats have produced a mind-bending diversity of form and function, a difference in size that spans more than three magnitudes (0.01 – 18 m), and a profusion of reproductive strategies. Apart from their diversity and unique evolutionary history, fishes are of intense scientific interest for economic reasons, because they comprise the nutritional foundation for a large part of humanity (Costanza et al. 1997) and their exploitation over time has led to thriving – and warring – civilizations. Today, the impetus of sustainable fish management at a time of rapid ecological re-organization due to man-made climate change has made the study of fish ecology and fish stock productivity as urgent and important as ever."


Fig01--systematics
Fig.1: Origin, evolution, and systematics of fishes. A – Origin hypothesis. Early during chordate evolution, sessile arm feeders (pterobranchs) gave rise to gill feeders. In one line, free-swimming filter-feeding larvae lost their sessile stage and evolved into the first, gill-feeding vertebrates (redrawn after Romer and Parsons 1977). B – Evolution and relative abundance of major fish lines through time. Most of today’s fish groups originated in the Devonian; ray-finned fishes became the dominant fish group during the Meso- and Cenozoic (numbers refer to million year ago, Mya). C – Abridged overview of Actinopterygii systematics showing select major orders (-formes) and Perciform families (-idae) sorted top to bottom from ancestral to most derived groups. Most fishes are Teleosts, and within those, most belong to the Euteleosts. Acanthopterygii evolved fin spines; the most species-rich vertebrate order are the Perciformes (after Moyle and Cech 2004).

Ann Bucklin organizes special issue in the ICES Journal of Marine Science

Patterns of Biodiversity of Marine Zooplankton Based on Molecular Analysis is the latest themed set of articles from​ ICES Journal of Marine Science. (See https://academic.oup.com/icesjms/issue/78/9#1302581-6403476 ). This collection showcases the ongoing refinement of molecular approaches for analysis of zooplankton diversity.

ICES (International Council for the Exploration of the Sea) commissioned a cartoon by Bas Köhler and announced the publication (see: https://www.ices.dk/news-and-events/news-archive/news/Pages/TSZooplankton.aspx).

The motivators for the special issue are members of the SCOR WG157 MetaZooGene (see: https://metazoogene.org/ ), chaired by Ann Bucklin, who also authored the introductory paper, New insights into biodiversity, biogeography, ecology, and evolution of marine zooplankton based on molecular approaches (see https://doi.org/10.1093/icesjms/fsab198) with co-authors, Katja T.C.A. Peijnenburg (NL), Ksenia Kosobokova (RU), and Ryuji J. Machida (TW).