Differential Responses of Maximum Versus Median Chlorophyll-a to Air Temperature and Nutrient Loads in an Oligotrophic Lake Over 31 Years

Authors

Nicole K. Ward, Virginia Polytechnic Institute and State University
Bethel G. Steele, Institute of Ecosystem Studies
Kathleen C. Weathers, Institute of Ecosystem Studies
Kathryn L. Cottingham, Faculty of Arts and Sciences
Holly Ewing, Bates CollegeFollow
Paul C. Hanson, University of Wisconsin-Madison
Cayelan C. Carey, Virginia Polytechnic Institute and State University

Publication Title

Water Resources Research

Document Type

Article

Department or Program

Environmental Studies

Publication Date

5-2020

Keywords

climate change, land use, long term, modeling, oligotrophic lake, phytoplankton

Abstract

Globally, phytoplankton abundance is increasing in lakes as a result of climate change and land-use change. The relative importance of climate and land-use drivers has been examined primarily for mesotrophic and eutrophic lakes. However, oligotrophic lakes show different sensitivity to climate and land-use drivers than mesotrophic and eutrophic lakes, necessitating further exploration of the relative contribution of the two drivers of change to increased phytoplankton abundance. Here, we investigated how air temperature (a driver related to climate change) and nutrient load (a driver related to land-use and climate change) interact to alter water quality in oligotrophic Lake Sunapee, New Hampshire, USA. We used long-term data and the one-dimensional hydrodynamic General Lake Model (GLM) coupled with Aquatic EcoDyanmics (AED) modules to simulate water quality. Over the 31-year simulation, summer median chlorophyll-a concentration was positively associated with summer air temperature, whereas annual maximum chlorophyll-a concentration was positively associated with the previous 3 years of external phosphorus load. Scenario testing demonstrated a 2°C increase in air temperature significantly increased summer median chlorophyll-a concentration, but not annual maximum chlorophyll-a concentration. For both maximum and median chlorophyll-a concentration, doubling external nutrient loads of total nitrogen and total phosphorus at the same time, or doubling phosphorus alone, resulted in a significant increase. This study highlights the importance of aligning lake measurements with the ecosystem metrics of interest, as maximum chlorophyll-a concentration may be more uniquely sensitive to nutrient load and that typical summer chlorophyll-a concentration may increase due to warming alone.

Comments

Original version is available from the publisher at: https://doi.org/10.1029/2020WR027296

Recommended Citation

Ward, Nicole K., et al. “Differential Responses of Maximum Versus Median Chlorophyll‐a to Air Temperature and Nutrient Loads in an Oligotrophic Lake Over 31 Years.” Water Resources Research, vol. 56, no. 7, 2020.

Copyright Note

© 2020 The Authors. This is the publisher's version of this Open Access article.