By Kristen Jabanoski
“In terms of biogeochemistry, Long Island Sound was blank. It wasn’t really on the map of the East Coast,” Vlahos explained.
Enter the Long Island Sound Respire project, funded by a $398,000 grant from the Long Island Sound Study, which supported Vlahos and doctoral student Lauren Barrett sampling the Sound monthly from June 2019 to October 2021 to gather key information not previously collected in water quality sampling.
Their goal was to understand how oxygen moves through the Sound’s water column, along with key nutrients such as carbon and nitrogen, by sampling ten sites across the Sound aboard Connecticut Department of Energy and Environmental Protection (CT DEEP)’s research vessel John Dempsey. With funding from the Long Island Sound Study, CT DEEP has been monitoring the Sound’s water quality for New York as well as Connecticut since 1991. Long Island Sound Respire enhanced CT DEEP’s existing long term water monitoring program, and has led to several new initiatives which will provide more detailed data on nutrients and acidification in the Sound (more information).
The COVID pandemic briefly interrupted water sampling in spring 2020. Monthly research cruises came to a halt in April and May, but the value of close cooperation with CT DEEP became clear when they resumed over the summer. Although COVID protocols prevented CT DEEP from hosting scientists from other institutions aboard the Dempsey, part of the sampling continued because the CT DEEP staff scientists went out of their way to collect samples that the UConn team needed for nutrient and carbonate chemistry analysis.
Environmental analyst Matt Lyman of CT DEEP explained, “Dr. Vlahos’ Respire Project provides important information supporting CT DEEP’s commitment to protect and improve the health of Long Island Sound. While the sample collection for this project added to an already busy sampling schedule, it was certainly worth it to ensure a continuous data set over the course of the project.”
Vlahos also works closely on the project with UConn physical oceanographer and modeler Dr. Michael Whitney and UConn biological oceanographer Dr. Jamie Vaudrey. Whitney built a dynamic model for Long Island Sound, and embedded chemistry information from Vlahos’ work into that model. Vaudrey provides valuable guidance on respiration and primary productivity measurements.
Vlahos and her team confirmed and characterized a strong connection between two environmental problems often considered separately – excess nitrogen entering the Sound and coastal acidification.
Nitrogen is a nutrient that enters the Sound from many different sources, including agriculture, fertilizer, septic systems, and treated wastewater. In excess it fuels the growth of algae, which can affect water quality and human health. When the short-lived algal cells decompose, the oxygen in the water is often depleted, leading to fish kills and ecosystem damage.
While ocean acidification is a global issue caused by the ocean absorbing the extra carbon dioxide in the atmosphere from burning fossil fuels, coastal acidification can also be fueled by excess nutrients. The pH of seawater can decrease locally when algal overgrowth happens. This is because the bacteria breaking down the algal cells both use up oxygen and release carbon dioxide into the water.
Vlahos hopes to permanently add carbonate chemistry measurements to the Long Island Sound water monitoring program to better track acidification.
Major reductions in nitrogen output into Long Island Sound are a noteworthy water quality accomplishment since the introduction of Total Maximum Daily Load (TMDL) to reduce nitrogen in 2000. An estimated 50 million pounds of nitrogen are kept out of the Sound every year due to wastewater treatment plant upgrades in New York and Connecticut.
These reductions have led to improved oxygen levels in the Sound, and reduced the geographic extent of low oxygen during the summer months by more than half compared with the 1990s. This means better water quality and improved conditions for fish, other marine animals, and people.
Vlahos, who was recently elected Connecticut co-chair of the Long Island Sound Science and Technical Advisory Committee, notes that the outlook for climate change in our region means that we can’t get complacent when it comes to water quality. Even if nutrient pollution in the Sound holds steady, the warming Sound will have less capacity to hold dissolved gasses including oxygen – similar to the way a warm soda goes flat more quickly. This means that at the same level of nitrogen input, a warmer Sound will be more prone to low oxygen. Connecticut and New York will need further reductions in nitrogen just to maintain today’s water quality improvements into the future. Vlahos and Whitney published these findings in Environmental Science and Technology last year.
For the RESPIRE project, the right technology was available at just the right time. Vlahos and her research group brought in a newly-developed instrument called the Contros HydroFIA TA Analyzer to measure alkalinity, which they can also use to monitor coastal acidification. This cutting-edge instrument was tested and went on the market just a few years before the study began.
Because there was little previous data on inorganic carbon in Long Island Sound, Vlahos and her graduate students started measuring alkalinity, the more familiar pH, the partial pressure of carbon dioxide, and dissolved inorganic carbon on monthly cruises with CT DEEP. These measurements characterize total inorganic carbon, which was a critical gap in the carbon budget for the Sound.
They used these carbonate parameters to create a monthly map of a measurement called omega in Long Island Sound. Scientists use omega to track ocean and coastal acidification. Omega is the saturation state of calcium carbonate, which is important because carbonate ions are the building blocks that marine animals including shellfish use to make their shells. An omega value greater than one indicates supersaturation, whereas values less than one are a warning sign of undersaturation, a condition favoring the dissolution of calcium carbonate shells.
The team discovered that a large swath of central Long Island Sound has an omega value below one, which is considered corrosive to shellfish and other calcifying animals, during July and August. This low omega area mirrors the low oxygen zone during the summer. As a result, Vlahos suggests that omega values could be used in the future to set new Total Maximum Daily Loads for the Sound, rather than relying exclusively on nitrogen values to set these limits.
What can concerned coastal and inland residents do to protect water quality gains in the warming Sound? Vlahos suggests reducing your household’s contribution to nutrient runoff by using less fertilizer for lawns and gardens, along with replacing septic systems with new nitrogen removal systems. In addition to reducing household nitrogen input, communities can support shellfish restoration initiatives, as filter-feeding shellfish take up significant amounts of nitrogen from the Sound through the algae they eat.
While the Respire project aims to understand the chemistry of the Sound as a whole, Vlahos’ recently-funded Alkalinity in Long Island Sound Embayments (ALISE) project aims to understand the carbonate chemistry of the embayment areas where most shellfish aquaculture is located. These areas could be particularly at risk from coastal acidification; while water quality issues tend to be diluted in the main part of the Sound, they may be exacerbated in the more closed off embayments. Her long term goal is to create omega maps for coastal Connecticut and New York, which would allow shellfish growers to choose where to farm wisely.
“The embayment program will help the shellfish industry know which areas are good for growing shellfish, which are more vulnerable to acidification, and why,” Vlahos explained.
“Estuaries tend to have larger variations in carbonate chemistry, and yet most ocean acidification data comes from the open ocean,” said Dr. Vlahos.
Vlahos and her graduate students have also been conducting research in the Arctic under a project funded by the National Science Foundation to learn about the changing water chemistry of ice melt zones, seasonal pools of freshwater that now freeze and thaw annually. The importance of understanding these areas is growing: as the permanent ice cap melts in a warming Arctic, in just a few decades summers may be ice-free. This could change the role of the Arctic in carbon sequestration, further affecting the global climate.
After a two week pre-cruise COVID isolation period in Alaska, the team collected water samples aboard the R/V Sikuliaq from the Bering sea to the Chukchi Sea between May 20 to June 14, 2021. At several sampling stations on the ice, polar bear activity was a concern and spotters on the bridge of the ship watched keenly to ensure they didn’t get too close to the researchers.
Although the Arctic Ocean is more than 5,000 miles from Long Island Sound, it is similar to the Sound in one important way. It’s an area where open ocean measurements don’t cut it in terms of understanding the chemistry, because unique local dynamics are at play.
The Arctic research will continue this spring, but thus far the team has discovered that there are differences in carbonate chemistry and productivity, or the amount and diversity of life that those areas can support, compared with the open ocean.
“In the Arctic, the train has left the station. We can’t reverse the changes we’re seeing, but we can inform global climate models to make them more accurate,” Dr. Vlahos reflected, “However, in Long Island Sound, we have a chance to inform coastal residents and actually act to reduce our nutrient output, which makes a difference.”
Kristen Jabanoski is a science communicator who writes frequently about fisheries, aquaculture, and environmental research on Long Island Sound.
Monthly nutrient water quality surveys are conducted throughout the year to document processes relevant to hypoxia and nutrient dynamics. This proposal will add coastal acidification parameters (Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC)) to the current monitoring program. This project will develop and maintain a long-term coastal acidification monitoring program in the off-shore waters of Long Island Sound at a subset of stations currently monitored by CT DEEP to better understand future impacts in relation to eutrophication, hypoxia, and climate change. Carbonate chemistry samples will be analyzed by the Environmental Chemistry & Geochemistry Lab of Dr. Penny Vlahos in the Department of Marine Sciences at the University of Connecticut. (back to top)
In 2022-2023, the Interstate Environmental Commission will incorporate additional monitoring and sampling to assess coastal acidification in the western Long Island Sound, enabling a more comprehensive assessment of both the extent of hypoxia and the variation of water quality parameters relevant to hypoxia throughout Long Island Sound. (back to top)
USGS will establish and lead a long-term monitoring network to provide data for calculating aragonite saturation and increase spatial and temporal coverage for embayment monitoring across Long Island Sound. (back to top)
Save the Sound will leverage the network of community science monitoring groups in the Unified Water Study for this monitoring effort, which will enable widespread LIS embayment coverage to complement the monitoring being considered for the open waters and other portions of the Sound. This will add coastal acidification parameters—Total Alkalinity (TA), pH, Dissolved Organic Carbon (DOC), and Dissolved Inorganic Carbon (DIC)—to the Unified Water Study for the 2023 monitoring season. It will also fund creation of meaningful and relatable communications on the importance of coastal acidification monitoring to laypeople around the Sound. (back to top)
The LISICOS buoy array has included pH and pCO2 sensors in the western Sound since 2018 and these data have shown that pH can change from 8 to 7.2 over the summer (May to September) but changes of 0.2 are possible in a single day. To properly interpret the results of ship sampling surveys, we will purchase a pair of sensors to measure pH and pCO2 at 15-minute intervals at mid-depth (~65 feet) in central LIS by mounting them on the mooring cable of the Central Long Island Sound buoy. The deployments will be integrated into NOAA-funded buoy deployments. In addition to the open-access data record, the final deliverable will be a data report and recommendations on how to sustain a long-term monitoring program. (back to top)