Development of a tool for assessing eutrophication status using satellite Chl-a
Among water quality parameters related to eutrophication, chlorophyll-a concentration (Chl-a), a proxy for phytoplankton biomass, is a useful indicator [1]. However, methodologies on the use of Chl-a are still under discussion. As Chl-a can be observed from ocean color satellite sensors, many studies affirmed the temporal and spatial advantages of remote sensing for monitoring and assessing coastal zone water quality [2, 3]. On the other hand, few studies have used both the level and the trend of remotely sensed Chl-a concentration (satellite Chl-a) for assessment of eutrophication [4] (Terauchi et al., 2014). Terauchi et al., [4] demonstrated the usefulness of applying both the level and trend of satellite Chl-a in the assessment of eutrophication in Toyama Bay, Japan, and proposed a methodology to classify marine water into six eutrophication statuses: Low-Decreasing (LD), Low-No trend (LN), Low-Increasing (LI), High-Decreasing (HD), High-No trend (HN) and High-Increasing (HI). This classification is also applied to the eutrophication assessment of the NOWPAP region [5].
In 2018, CEARAC developed the NOWPAP Eutrophication Assessment Tool (NEAT) using only satellite Chl-a, which is one of the three parameters in the screening procedure of the revised NOWPAP Common Procedure [6, 7]. NEAT preliminarily assesses the eutrophication status of the NOWPAP region using time-series data that is tuned to regional characteristics through the comparison and verification of satellite and in-situ data. The coastal eutrophication potential (CEP) in the NOWPAP region, the results of the assessment using this tool, can be found on the CEARAC Web-GIS with the six color-coded classifications as shown in the bar graph below.
In 2021, an international research team comprising Dr. Elígio de Raús Maúre and Dr. Genki Terauchi, researchers of NPEC, Prof. Joji Ishizaka, Institute for Space-Earth Environmental Research (ISEE), Nagoya University and Dr. Nicholas Clinton and Michael DeWitt, two Google LLC members, developed an online tool called “Global Eutrophication Watch” that enables global-scale eutrophication assessment using satellite Chl-a data. The tool can preliminarily identify areas in the world’s oceans that are eutrophic or oligotrophic, or that are likely to become eutrophic (or oligotrophic) [8]. The tool is available in English and NOWPAP languages.
Currently, NPEC is developing regional and national indicators to track progress towards the UN Sustainable Development Goal (SDG) 14.1.1(a): Index of Coastal Eutrophication, using our Global Eutrophication Watch.
References
[1] Harding, LW. Jr. and Perry, ES., “Long-term increase of phytoplankton biomass in Chesapeake Bay,” Mar Ecol Prog Ser 157, 39–52(1997).
[2] Kitsiou, D. and Karydis, M., “Coastal marine eutrophication assessment: A review on data analysis,” Environment International 37(4), 778 – 801 (2011).
[3] Klemas, V., “Remote Sensing Techniques for Studying Coastal Ecosystems: An Overview,” Journal of Coastal Research, 2 – 17 (2011).
[4] Terauchi, G., Tsujimoto, R., Ishizaka, J., and Nakata, H. “Preliminary assessment of eutrophication by remotely sensed chlorophyll-a in Toyama Bay, the Sea of Japan” Journal of Oceanography, 70, 175 – 184 (2014).
[5] Terauchi G, Maure, E R, Yu Z, Wu Zaixing, Lee C, Kachur V, and Ishizaka J “Assessment of eutrophication using remotely sensed chlorophyll-a in the Northwest Pacific region”, Proc. of SPIE, 10778, Remote Sensing of the Open and Coastal Ocean and Inland Waters, 107780H; doi: 10.1117/12.2324641 (2018).
[6] NOWPAP CEARAC , “Procedures for assessment of eutrophication status including evaluation of land-based sources of nutrients for the NOWPAP region” , (the NOWPAP Common Procedure 2013 Revised Edition)
[7] NOWPAP CEARAC, “Procedures for assessment of eutrophication status including evaluation of land-based sources of nutrients for the NOWPAP region “, (the NOWPAP Common Procedure 2015 Revised Edition)
[8] Elígio de Raús Maúre, Genki Terauchi, Joji Ishizaka, Nicholas Clinton & Michael DeWitt “Globally consistent assessment of coastal eutrophication” Nature Communications volume 12, Article number: 6142(2021)
