How does climate change impact aquatic net community production? - A novel mesocosm

Understanding the biological processes of natural ecosystems is integral to predict their responses to anthropogenic climate change and increasingly extreme climate events. Our ability to quantify net primary production (NPP) is key to better understand community food web structure and carbon sequestration. Traditional ex situ and discrete laboratory experiments, using Winkler incubation methods, provide limitations when accounting for the complex biological processes that occur in aquatic ecosystems. Current in situ chamber approaches are limited in their physical scope. Previous experiments have measured primary productivity in flora using benthic enclosures, as well as spatially discrete geochemical changes in the water columns by using either the Eulerian or Lagrangian fluid motion models. This work shows a non-invasive two-chambered mesocosm, coupled with an equilibrator and a weather station, to accurately calculate levels of net primary production, gross primary productivity (GPP) and total respiration (R) in aquatic communities. Equilibrator data allowed us to calculate daily changes in pCO2, and their correlation with NPP, GPP, and R. A three-day deployment measured r trends that were consistent with expected diurnal natural cycles, demonstrating that our novel mesocosm is a reliable non-invasive method to measure NPP, GPP, and R in aquatic ecosystems. This tool also may provide a standardized approach to quantify marine community productivity and it can be deployed for longer periods of time to understand the trends between NPP and anthropogenic climate change. This study is part of a larger effort to explore how climate change is impacting net community production.