Implications of rapid climate change on lake algal ecology in Acadia National Park, U.S.A.: A case study on Seal Cove Pond

Fowler, Rachel; Warner, Kate; Gawley, William; Saros, Jasmine

From the abstract: "Recent work has shown that average water clarity of lakes in Acadia has been decreasing since 1995. This decline corresponds to an increase in dissolved organic carbon (DOC) concentrations across the same set of lakes. It is believed that rapid changes in climate conditions and patterns of atmospheric deposition have resulted in these shifts in DOC and subsequent declines in water clarity. In particular, extreme precipitation events are sometimes correlated with elevated lake water DOC concentrations. Changing phytoplankton community structure may be a consequence of these fluctuations in DOC from extreme precipitation events. We analyzed a sediment core from Seal Cove Pond to create historical algal pigment and diatom reconstructions, and evaluated modern responses of phytoplankton community structure to storm events in Seal Cove Pond. From the 1990s to present, many algal pigments increased in the lake sediment record, while some declined. Shifts in pigments within algal groups may indicate that certain taxa have gained competitive advantages with changing environmental conditions that mediate light, nutrient availability, and water temperature. The diatom record shows that Discostella stelligera, an indicator of lake thermal structure, has increased since the beginning of the record in 1880. The highest relative abundance occurred in recent decades, which may reflect observed trends in increasing water temperature and DOC. In water samples from 2016, phytoplankton responded differently to precipitation events in the spring and fall, with increasing total algal biovolume after spring storms and decreasing total algal biovolume after fall storms. Phytoplankton community structure also differed between spring and fall. Certain phyla, such as chrysophytes, may have a competitive advantage over other phyla with increased storminess. It is our goal that these results will be useful for informing resource management plans for lakes and ponds in Acadia National Park."