Using Daphnia Ephippia Pigmentation and Size to Determine Past Trophic Levels of Twin Ponds, Vermont.

The ephippia of the zooplankton, Daphnia, were analyzed from a mesotrophic pond in Brookfield, Vermont to study the pond’s past productivity. Understanding Twin Pond’s productivity allows for a look into the past and the ability to understand how human impact and climate change have shifted. This research was conducted from a short sediment core that extends a productivity record previously analyzed from a Holocene-length core which ended just after European settlement. Changes in ephippia abundance, size, and pigmentation from 1500-1780 AD are due to a rise in nutrient input following European settlement and deforestation. This period was followed by a decrease in abundance in the mid-1800s due to farm abandonment. From the 1900’s to present, ephippia abundance decreased with the exception of a small increase likely caused by deforestation during the 1938 hurricane. The pigmentation and size of ephippia shared some correlation before 1800 but became decoupled and suggested that Daphnia populations stopped responding to fish predation. By 1900, ephippia were the smallest and darkest of the record. The recent changes in ephippia abundance, size, and pigmentation may be due to a decrease in Daphnia food quality and changes in the predator and prey cycle related to increasing temperatures.