Multi-decadal, seasonal, and spatial variation of calanoid copepod body size in Delaware Bay
Date
2018
Authors
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Publisher
University of Delaware
Abstract
Size affects feeding, growth, and metabolism in all organisms, and in ectotherms, size is affected by environmental factors. The thermal plasticity of body size in ectothermic species is known as the temperature-size rule (TSR), which states that warmer temperatures lead to a decrease in generation time, resulting in overall smaller size at maturity. I investigate temperature and size variation of dominant copepod species in the Delaware Bay over multiple decades by comparing my results to historical data from the 1930’s (Deevey 1960) to assess whether the relationship has changed in response to long term warming. Results for Acartia tonsa and Centropages hamatus indicate a decrease in the strength of temperature size relationships over time, resulting in less body size variation in Delaware Bay under current conditions. I also analyze the effects of temperature and food on adult female copepod body size in the current study. While in situ temperature is the only significant predictor of seasonal variation in A. tonsa and C. hamatus adult body size, chlorophyll effects spatial body size variation of A. tonsa throughout Delaware Bay in August 2016, when bay wide temperatures are more constant. Based on the results of this study and predictions for future temperature and chlorophyll conditions in Delaware Bay, calanoid copepod body size is expected to continue to decrease unless a lower size limit is reached.