Award: OCE-1459827

The burning of fossil fuels by humans is causing more carbon dioxide in the atmosphere to move (dissolve) into the oceans than what would happen normally. This movement of carbon alters the chemistry of the oceans through a process called ocean acidification (OA), which makes it more difficult for some marine plants to survive. However, little is known about the impacts of OA on cold-water marine ecosystems, and on the plants that live there, because of the lack of data in remote locations. In addition to this, cold-water areas are warming nearly twice as fast as the global average. Therefore, we think that the combination of OA with the fast rate of warming may stress the plants that live in the cold-water areas. Our research 1) measured how carbon dioxide is changing cold-water areas and 2) studied the impact of these changes on a marine plant (called coralline algae) that grows a hard, rock-like skeleton. We found that seawater warming and OA causes a decline in how fast this plant grows and in the strength of its skeleton. Based on our results, we propose that continued warming and OA will make it harder for this plant to grow by the end of this century. Since this plant provide habitats for many other marine plants and animals, a decline in its growth will change what organisms are found in cold-water marine communities. Our research also used the skeleton of the plant as an enviromental archive to understand how the oceans themselves have changed through the past several decades. We found that the rapidly warming Gulf of Maine is becoming too warm for the plant to survive, and it is starting to die off there. In contrast, the plant growing in the Arctic might partially benefit from the recent increases in temperature and light availability (the later due to decreases in sea ice, which in turn allows more sunlight to reach the sea floor for photosynthesis). From our results, we suggest that in cold areas like the Arctic, slightly warmer temperatures will benefit the plant while in warmer areas like Maine, temperatures may get too hot for the plant to survive. Finally, we measured the chemistry of the plant in specimens grown in aquarium tanks. We found a statistical relationship between chemical measurements in the plant skeleton and the seawater conditions (pH and temperature) in the tank. This means that we can use this relationship to backtrack past seawater temperatures and pH going as far back as 650 years. We are working to understand past changes in seawater temperature and carbon chemistry in the northwest and Atlantic Ocean. From this work, we are learning that local conditions are as important as global conditions in controlling how the environment is changing at a specific location. Through this research project, we worked with high school and undergraduate students to learn about the connections between our atmosphere, oceans, and living organisms, and how people are changing all of these things. We mentored many students, mostly women, at differing points in their career (high school, undergraduate, graduate, post-doctoral) to provide a springboard for people interested in entering and/or continuing in STEM fields. We shared the research results with a wide range of audiences through scientific and public presentations, and publications in scientific journals. Last Modified: 01/21/2020 Submitted by: Branwen Williams