October is packed with ways to get outside, lend a hand and help Long Island Sound. And apparently, October beach cleanup season is also onesie season. Celebrate Halloween with a cleanup at West Meadow Beach on Long Island – costumes, aquatic alter egos, and suspiciously elaborate animal suits (furry, perhaps?) are welcome.
And if Halloween isn’t enough, we’re sneaking one November event onto the list. Mystic Aquarium and CT NERR are hosting a Mermaid Beach Cleanup at Bluff Point State Park. Grab an ocean-themed or winter onesie and clean the coast alongside a very special mermaid guest. Yes, really.
Read the newsletter to find an event near you:
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The life cycle of the American eel (Anguilla rostrata) is as complicated as its journey from the Sargasso Sea to Long Island Sound. American eels hatch as tiny, leaf-shaped larvae in the Sargasso Sea, a unique region in the North Atlantic Ocean bounded by four major ocean currents.
The first phase of their lives includes a journey thousands of miles long to the Atlantic coast. To get there, the larval eels quite literally go with the flow, drifting on ocean currents for nearly a year. Those that are picked up by the Gulf Stream are swept along the eastern seaboard of North America and may eventually be funneled into Long Island Sound.
When they reach the continental shelf off the Atlantic coast, the eels undergo their first metamorphosis, becoming tiny, transparent “glass eels.” Once they arrive at coastal rivers and streams, it’s time to go against the flow. The young eels begin swimming upstream toward fresh water, developing pigment and darkening into elvers.
A note about fish handling: Fish shown out of the water were collected and handled by trained staff under appropriate scientific collection permits. Fish were handled using practices designed to minimize stress.
As they swim farther upstream in search of freshwater habitat, they gradually mature into yellow eels. They remain in the yellow eel stage for 10 to 30 years before undergoing their final transformation into silver eels. Their eyes, nose, and fins grow, skin thickens, and their digestive systems begin to shut down as they prepare for the long, grueling trip back to the Sargasso Sea.
Swimming upstream isn’t the only way these fish go against the flow. Their unusual migratory behavior also challenges the norm. Most migratory fish are anadromous, meaning they spend most of their lives in salt water and travel to fresh water to spawn. American eels are catadromous and do the opposite: they spend much of their lives in fresh or brackish water before migrating back to the salty ocean to spawn. In fact, they are the only catadromous fish in North America.
Home to the famous Bermuda Triangle, the Sargasso Sea holds another secret: exactly where and when American eels spawn. Despite decades of research, no one has ever observed American eels spawning in the wild. Scientists know they breed there because their smallest, youngest larvae have been found in the region. Only recently have satellite tags attached to eels provided direct evidence that adults make it back to the Sargasso Sea.
American eels that win the ocean-current lottery and end up in Long Island Sound become an integral part of the ecosystem.
Once here, they fill roles as both consumers and prey. As consumers, they are opportunistic eaters – scavenging for dead fish and other animals while also hunting small crustaceans, fish, and insects. They are also an important food source for predators, including birds and larger fish such as striped bass.
American eels are also an important indicator of ecosystem connectivity. Because they begin their lives in the ocean and migrate upstream into fresh water, their presence, or absence, in upstream areas can serve as a report card on whether rivers and streams remain connected. Dams and other barriers can make that journey difficult or impossible, while fish passage projects and barrier removals can reopen habitat that eels and other migratory species depend on.
Assessed as Endangered on the International Union for Conservation of Nature (IUCN) Red List, the American eel’s future depends in part on the health and connectivity of the freshwater systems where it spends much of its life.Protecting water quality, restoring habitat, and reconnecting rivers and streams can help give American eels the healthy waterways they need to complete their life’s journey spent going with the flow, against the flow, and sometimes, against the odds.
Hurricane Erin passed hundreds of miles offshore of the Long Island Sound region in the summer of 2025 without making landfall. Along the coast, Erin announced its presence with unusually high surf and large waves, delighting beachgoers more accustomed to the Sound’s generally calm waters.
Beneath the surface, however, Erin was creating a different kind of disturbance.
As powerful winds and waves churned the water, the storm disrupted the Sound’s normally layered water, often described as a “water column,” mixing oxygen-rich surface waters into deeper waters. While the waves subsided within a few days, the storm’s effects below the surface lingered much longer, helping bring an early end to hypoxic conditions during what became a historic year for improved water quality in Long Island Sound.
A success story that’s still evolving
Erin offered scientists a rare opportunity to observe one piece of a much larger puzzle: why hypoxia still varies from year to year despite improvements in water quality.
Over the past several decades, nitrogen loading to the Sound has been drastically reduced by upgrading wastewater treatment plants and implementing other pollution reduction measures. Those efforts are considered one of the biggest successes in water quality improvement for the Sound. The size and duration of the Sound’s hypoxic zone have declined significantly, with the maximum extent dropping to a historic low of only 18 square miles in 2025. The hypoxia forecast for 2026 predicts another year of limited hypoxia, potentially even less than last year.
While these long-term improvements have clearly reduced the overall extent of hypoxia, scientists have also observed substantial differences from one year to the next. Some summers experience more severe hypoxia than others, even when nitrogen inputs are relatively similar.
Researchers do, however, understand the fundamental processes that lead to hypoxia.
Nitrogen entering the Sound fuels the growth of micro algae. When those algae die, they sink to the bottom where bacteria decompose them, consuming oxygen in the process.
In the summer, the surface and bottom waters of Long Island Sound separate into layers, a process called stratification. Fresh water from rivers remains near the surface while saltier, denser water settles near the bottom. In between is a transitional zone called a pycnocline. Additionally, heat from the sun causes surface waters to warm, decreasing its density relative to the deeper waters which receive less solar radiation.
Because the top and bottom layers don’t mix easily, oxygen-rich surface water can’t readily replenish the oxygen being consumed near the bottom.
That’s when hypoxia develops.
Scientists have identified several factors in addition to nutrient loading that contribute to year-to-year variability, including waves, wind, and temperature, but the relative importance of these factors combined with nutrient loading remains an active area of research.
That’s where a new tool, called the Wirewalker, comes in.
Watching the whole water column
Long Island Sound is already one of the most closely monitored estuaries in the country. Scientists with the Connecticut Department of Energy and Environmental Protection (CT DEEP) and the Interstate Environmental Commission (IEC) regularly sample water quality at stations across the Sound, collecting vertical profiles of the water column for many parameters. A network of LISICOS buoys adds continuous monitoring at two or three fixed depths.
In the summer of 2025, researchers added a new tool, one that supplemented these existing monitoring efforts by continuously traveling up and down through the water column, providing a detailed look at how conditions change with depth and over time.
Funded through the Long Island Sound Research Grant Program, UConn scientists Cara Manning, Leonel Romero, and Samantha Siedlecki deployed a Del Mar Wirewalker, an autonomous water quality profiling system that continuously moves up and down in the water column. Traveling at a speed of up to about 20 meters per minute, the round trip between the surface and bottom can take as little as two minutes.
Instead of collecting data at just three points in the water column or for just one day at time, the Wirewalker measures the entire vertical profile at 300 different depths for the duration of its deployment.
Imagine trying to understand a layer cake by sticking three toothpicks into it: one near the top, one in the middle, and one near the bottom. You’d know there were different layers, but not exactly where one ended and the next began. The Wirewalker slices through the entire cake over and over again, revealing every layer in between.
By profiling the entire water column hundreds of times each day, scientists can find the location of the boundary between surface and bottom waters and watch stratification form, weaken, and break down in remarkable detail.
“If you have measurements at three depths, you can see if there’s a gradient between the surface and the bottom, but you can’t necessarily resolve exactly where stratification is,” explained Manning. “You know the surface is different than the bottom, but you don’t know how thin is that really high oxygen layer of the surface. [With the Wirewalker] we’re able to see the stratification breakdown more. And so, using this combination of high-resolution measurements of oxygen, but also things like currents and turbulence, we get a better understanding of the physical drivers as well as biological.”
Connecting physics and biology
The Wirewalker was deployed from June to September during the summer of 2025 in the western Sound between two of the LISICOS monitoring buoys. During this time, the Wirewalker completed nearly 300 profiles each day, recording changes in temperature, salinity, oxygen, chlorophyll, particles, and turbulence throughout the water column.
For the first time in Long Island Sound, scientists could simultaneously observe physical forces – wind, waves, and mixing – and oxygen distribution at very high vertical resolution throughout the water column.
That provided valuable data during two summer mixing events.
One event in late June was followed by an increase in dissolved oxygen near the bottom. Wirewalker was able to capture the mixing event, and the data showed increased oxygen near the bottom but not a full breakdown of the stratification.
Then came Hurricane Erin.
Although the storm never made landfall, its winds and waves completely disrupted the seasonal stratification, mixing oxygen-rich surface water throughout the water column and producing a strong reoxygenation event in late August.
The timing is what makes this event particularly interesting. Scientists monitor both the maximum extent of hypoxia and how long low-oxygen conditions persist in the Sound each season. Although the maximum extent of hypoxia was already declining when the hurricane passed through, no hypoxic conditions were detected at any sampling stations after Erin. The storm appears to have played a role in ending the season’s hypoxic conditions. As Manning explained, “this storm event in late August dramatically increased bottom water oxygen throughout Long Island Sound by mixing the full water column. If not for this event, then stratified conditions with low-oxygen bottom waters would have likely persisted in western Long Island Sound into September.”
Scientists are careful not to attribute that outcome to Hurricane Erin alone.
Any wind or storm events occur against a backdrop of nutrient loading, seasonal warming, and changing weather patterns. Rather than one storm determining the outcome, the evidence suggests that the sequence and timing of weather events throughout the summer helped shape how hypoxia developed.
From one summer to better predictions
The Wirewalker isn’t expected to become part of Long Island Sound’s permanent monitoring network. Deploying and maintaining the instrument requires regular boat trips, cleaning, and significant time to process the enormous amount of data it collects.
But the 2025 observations will contribute more than just a season’s worth of data.
“These observations will help us better understand the physical processes that shape oxygen conditions in Long Island Sound and improve the computer models used to simulate and predict those conditions,” said Leonel Romero.
The 2025 data will be used to improve a new model of physical processes in Long Island Sound that was built using the Regional Ocean Modeling System (ROMS). The new model simulates the physical, biological, and chemical processes that influence water quality in Long Island Sound. It will help scientists better understand how nutrient pollution, weather, and climate interact to shape conditions throughout the Sound. The Wirewalker’s detailed observations will allow scientists to compare the model’s predictions with what actually happened in the water.
Did the model capture the strength of the mixing?
Did it predict when stratification broke down?
Did it reproduce the changes in oxygen observed after storms?
Those comparisons help researchers improve the model, so it more accurately represents how Long Island Sound functions. Once refined, the model can help scientists predict how nutrient loading and other conditions expected in the future may affect water quality. This can help managers set new nitrogen reduction targets.
A clearer picture
The story of hypoxia isn’t simply about nutrient pollution. It isn’t simply about storms or wind, or rain. It’s about the interaction between the factors and when they happen.
Nutrients set the stage by creating the conditions for low oxygen to develop. Weather can shape how those conditions evolve, sometimes allowing hypoxia to intensify and other times interrupting the process through mixing.
By combining traditional monitoring, continuous buoy observations, intensive field studies like the Wirewalker, and increasingly sophisticated computer models, scientists are assembling a clearer picture of how Long Island Sound breathes through the summer. And with each new observation, they’re moving closer to answering one of the Sound’s most important questions: not just whether hypoxia will form, but why one summer can look so different from the next.
August is a great time to get outside, connect with your community, and take action for Long Island Sound. This month, we’re highlighting volunteer opportunities across the watershed, along with a special celebration of an important milestone in the Sound’s history. Read the Volunteer Newsletter: August 2026 to opportunities near you.
The Long Island Sound Partnership, with New York Sea Grant and Connecticut Sea Grant, will host a series of free community events this August to celebrate Long Island Sound and connect people with the places, wildlife, and communities that make the Sound special. Following the success of last year’s inaugural events, the Long Island Sound Celebration Days will return with activities in Connecticut, New York City, and Long Island.
The events are held each August in recognition of the foundation of the Long Island Sound Partnership. On August 15, 1985, the US Environmental Protection Agency and the states of Connecticut and New York came together to tour areas of the Sound aboard a research vessel and announce funding to study pollution and water quality challenges facing the estuary. That effort helped launch the collaborative work that continues today through the Long Island Sound Partnership.
Each Celebration Day will feature opportunities for visitors of all ages to explore the Sound through hands-on activities, guided experiences, science, and stories about this important estuary. All events are free and open to the public, though some activities may require advance registration.
Connecticut: Sherwood Island State Park, Westport, CT — August 14, 10am – 2pmDiscover Long Island Sound through guided hikes, hands-on science activities, arts and crafts, casting practice, giveaways, and more. Visitors will learn about the habitats and wildlife of the Sound while enjoying a day along the coast. Events will be held at the East Beach. No registration required.
Contact Maggie Cozens with questions or for more details at margaret.cozens@uconn.edu.
Long Island: Oyster Bay, NY — August 15, 10am – 2pmExplore Long Island Sound from the water with boat trips, kayaking, fishing, hands-on science activities, arts and crafts, and more. Activities will highlight the many ways people can enjoy and help protect the Sound. Check-in in front of the Waterfront Center, 1 West End Ave., Oyster Bay, NY. Free parking at Beekman Beach. Register here.
Contact Jimena Perez-Viscasillas at jbp255@cornell.edu for more information.
New York City: Randall’s Island, NY — August 22, 10:30am – 12:30pmJoin a guided boat tour of Long Island Sound featuring five stops along the way. Participants will hear stories about the history, biology, and importance of the Sound while experiencing this unique coastal ecosystem. Meet at Ferry Dock, Harlem River Pathway, New York, NY. Space is limited and registration is required. Register here.
Celebrate our country’s 250th birthday by getting out in nature and helping protect our beautiful Sound! There are beach cleanups, citizen science activities, and so much more coming up this July. Read the Volunteer Newsletter: July 2026 to opportunities near you.
You could drive the Sound’s 100-mile length in about two hours, but tracing all 971 miles of shoreline would be like driving from the Bronx to Jacksonville, Florida.
More shoreline means more habitat. The places where the coastline bends inward – bays, harbors, coves, and inlets – are known as embayments. These typically shallow, nearshore areas are partly sheltered from the open waters of Long Island Sound and provide calm conditions that are especially important for fish and other aquatic life.
Protected waters serve as nurseries for juvenile fish and invertebrates and provide food and shelter for species ranging from menhaden and winter flounder to horseshoe crabs, coastal birds, and migratory waterfowl. Together, embayments support a rich mosaic of habitats, including tidal rivers, eelgrass meadows, salt marshes, and shellfish reefs.
The same features that provide refuge for wildlife also benefit people. Embayments help absorb floodwaters, buffer coastal communities from storms, and filter pollutants before they reach the open Sound.
These sheltered waters are also places where people connect with Long Island Sound. Hundreds of embayments create opportunities for beaches, ports, marinas, shellfishing grounds, paddling routes, and other recreational activities. Some of the region’s most popular destinations – including Mystic Harbor and New Haven Harbor in Connecticut and Oyster Bay and Huntington Bay in New York – are embayments of Long Island Sound.
From wildlife nurseries to working waterfronts, these winding shores are one reason why Long Island Sound supports such a remarkable diversity of life and ways for people to enjoy and benefit from the estuary.
Here are some web links to help you explore coastal Long Island Sound:
The 971 miles of Long Island Sound shoreline does not include the additional coastlines of its islands, which add even more places where land and water meet.
CONNECTICUT AND NEW YORK (May 20, 2026)—The Long Island Sound Partnership has released its 2026 forecast for hypoxia in Long Island Sound, projecting another year of relatively limited levels of low-oxygen conditions in the Sound’s bottom waters.
Hypoxia, in Long Island Sound defined as dissolved oxygen levels below 3 milligrams per Liter, is expected to affect a maximum of 15 square miles during the peak summer period. The highest extent is likely to occur around August 2, with a projected range between 8 and 23 square miles.
If realized, the 2026 forecast would represent a modest improvement over 2025 conditions, when hypoxia covered approximately 18 square miles at its peak, the smallest extent recorded since monitoring began in 1987.
“This year’s hypoxia forecast shows Long Island Sound’s water quality is on the right track and that the years-long trend of improvement will continue, building on last year’s historic progress,” said EPA Region 2 Administrator Michael Martucci. “Better oxygen levels mean a healthier Sound, and a healthy Sound benefits people and drives local economies all along its shores.”
“We are seeing improvements in the health of Long Island Sound over time, and these forecasts help us track how the Sound is responding to our ongoing joint efforts,” said EPA New England Regional Administrator Mark Sanborn. “Together with our partners, we are continuing to make progress in improving the health of the Sound and the economies and communities that rely on it.”
The 2026 forecasted hypoxic area is 89 percent smaller than the average extent observed between 1993 and 2009, reflecting long-term reductions in nitrogen loading to the Sound. Excess nitrogen fuels the growth of algae, and oxygen in the water is consumed as the algae die and decompose. Over the past several decades, improvements to wastewater treatment facilities and septic systems have reduced nitrogen loading to Long Island Sound by 65 percent compared to the baseline established in 2000, helping decrease the severity and extent of hypoxia.
Despite this progress, hypoxia levels can vary significantly from year to year, with observed conditions often fluctuating by as much as plus or minus 50 percent of the predicted extent based on environmental conditions.
“Year to year variation is expected when it comes to hypoxia in Long Island Sound,” said James Ammerman, environmental analysist with NEIWPCC and Long Island Sound Partnership Science Coordinator. “While reducing nitrogen is key, and something we can directly manage, other factors such as water temperature, rainfall, wind, and storm activity can also influence how hypoxia develops each year. Even with that variability, long-term trends show how the Sound is getting healthier, and reducing nutrient inputs remains the most effective way to lower the risk of more severe hypoxia over time.”
A key question for 2026 is whether hypoxia will be as limited as it was in 2025. Based on long-term observations and model results, scientists who worked on the forecast suggest conditions could be similar or even slightly improved this year. However, after several years of declining hypoxia, a modest rebound toward slightly more hypoxia is also possible.
The 2025 Year in Review highlights key projects and accomplishments from the Long Island Sound Partnership. This issue celebrates the Partnership’s 40th anniversary, introduces a new Comprehensive Conservation and Management Plan, and showcases progress across its four core goals.
Spring is in full swing, and May brings even more ways to get outside and support Long Island Sound. Read the Volunteer Newsletter: May 2026 to find upcoming volunteer and citizen science opportunities near you, including featured events celebrating Long Island Sound Day.
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