Title

A new method to estimate global freshwater phytoplankton carbon fixation using satellite remote sensing: initial results

Document Type

Article

Publication Date

2-14-2021

Department

Michigan Tech Research Institute

Abstract

Freshwater phytoplankton carbon fixation is an important water quality parameter that can provide information about the health of lake ecosystems as well as their impacts on regional carbon cycling dynamics. Traditional field methods for measuring and monitoring primary production are unable to capture the necessary spatial and temporal variability at the global scale due to the sheer number and diversity of the world’s lakes. Satellite remote sensing offers a potential tool to quantify freshwater lake primary production on a global scale. A new straightforward remote sensing approach was developed to estimate global freshwater carbon fixation from satellite observable lakes using a straightforward depth-integrated model (DIM). A key component of this approach is the estimation of the light utilization index, ψ, for freshwater systems. A significant negative linear model to estimate growing season ψ as a function of latitude was developed from data acquired through an exhaustive literature review. In conjunction with a previous remote sensing generated freshwater chlorophyll-a concentration data set, the DIM was used to compute growing season carbon fixation for 80,000 freshwater lakes. While these estimates are rough and could exhibit large errors for any given lake, they provide a reasonable synoptic global estimate of freshwater carbon fixation. In general, growing season areal carbon fixation was shown to decrease with increasing latitude in both northern and southern hemispheres. Carbon fixation rates in the southern hemisphere were found to be significantly higher than in the northern hemisphere, with the African continent exhibiting the highest rates. Total daily carbon fixation (areal rate × lake area) was estimated at 1.03 teragrams of carbon per day (Tg C day−1) with approximately 71% occurring in the northern hemisphere. Total fixation was highest in North America, which was dominated by a very large number of Canadian Shield lakes. In general, total carbon fixation was well explained by total lake surface area, except in the far northern latitudes where lakes are more oligotrophic due to limited nutrient availability. This analysis resulted in a new freshwater carbon fixation product that provides new insights into the role freshwater lakes play in the global carbon budget.

Publisher's Statement

© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. Publisher’s version of record: https://doi.org/10.1080/01431161.2021.1880661

Publication Title

International Journal of Remote Sensing

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