Date of Degree

2-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Earth & Environmental Sciences

Advisor(s)

Gillian M. Stewart

Subject Categories

Ecology and Evolutionary Biology | Environmental Sciences

Keywords

Climatology, Copepods, Estuaries, Plankton

Abstract

In coastal ecosystems with decades of eutrophication and other anthropogenic stressors, the impact of climate change on planktonic communities can be difficult to detect. A time-series of monthly surface water temperatures in the Central Basin of Long Island Sound (LIS) from the late 1940s until 2012 indicates a warming rate of 0.03°C per year, with recent summer temperatures increasing most consistently. During this warming trend, the proportion of chlorophyll produced by smaller phytoplankton and flagellates appears to be higher during warmer summer and fall months, enabling an increase in annual chlorophyll despite static nutrient levels. The phenology of phytoplankton and zooplankton abundance also appears to have shifted.

Relative to the 1950s, winter and spring chlorophyll blooms are reduced, summer and fall zooplankton size has decreased, the proportion of small zooplankton has increased, and summer zooplankton abundance is reduced. These changes have occurred despite a lack of evidence for increasing gelatinous zooplankton abundance, which has been suggested as a causal mechanism for reduced summer copepod abundance and enhanced summer/fall phytoplankton abundance in other systems that have experienced long-term warming. These changes confirm general predictions for the direct impacts of climate change on aquatic communities, but also highlight the important of indirect impacts due to altered trophic dynamics.

 
 

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