These data have been collected as part of a cooperative project between the U.S. Geological Survey (USGS) and the U.S Environmental Protection Agency. This project began in 2016 and consisted of a mesocosm experiment quantifying short term responses by a transplanted natural diatom dominant algae community exposed to gradients of nitrogen, phosphorous, and a mixture of both nitrogen and phosphorus. The data consist of water quality parameters such as temperature and pH as well as aqueous nutrient concentrations and algae responses, including chlorophyll a concentrations, algae dry mass, algae ash-free dry mass, and intra-cellular phosphorus and nitrogen in algae. Algae growth rates were estimated from these data and are meant to be used with water-quality models; the results of this investigation can be found in the manuscript associated with this data release (Schmidt and others 2019).