Derivation of Red Tide Index and Density Using Geostationary Ocean Color Imager (GOCI) Data

Abstract

Red tide causes significant damage to marine resources such as aquaculture and fisheries in coastal regions. Such red tide events occur globally, across latitudes and ocean ecoregions. Satellite observations can be an effective tool for tracking and investigating red tides and have great potential for informing strategies to minimize their impacts on coastal fisheries. However, previous satellite-based red tide detection algorithms have been mostly conducted over short time scales and within relatively small areas, and have shown significant differences from actual field data, highlighting a need for new, more accurate algorithms to be developed. In this study, we present the newly developed normalized red tide index (NRTI). The NRTI uses Geostationary Ocean Color Imager (GOCI) data to detect red tides by observing in situ spectral characteristics of red tides and sea water using spectroradiometer in the coastal region of Korean Peninsula during severe red tide events. The bimodality of peaks in spectral reflectance with respect to wavelengths has become the basis for developing NRTI, by multiplying the heights of both spectral peaks. Based on the high correlation between the NRTI and the red tide density, we propose an estimation formulation to calculate the red tide density using GOCI data. The formulation and methodology of NRTI and density estimation in this study is anticipated to be applicable to other ocean color satellite data and other regions around the world, thereby increasing capacity to quantify and track red tides at large spatial scales and in real time.

A Systematic Review of the Application of GOCI to Water Quality Monitoring of Inland and Coastal Waters

“…Also, an improved Red Tide Index (RI) was established by [67] using normalized 𝐿 𝑟𝑐 (𝜆) data at 443, 490, and 555 nm to monitor red tide changes dynamically in East Lake. Additionally, [104] proposed a newly developed normalized red tide index (NRTI) (calculated with Equations ( 1)-( 4)), utilizing a spectroradiometer to observe the spectral characteristics of red tides and seawater in real-time.…”

A Systematic Review of the Application of the Geostationary Ocean Color Imager to the Water Quality Monitoring of Inland and Coastal Waters

“…Also, an improved red tide index (RI) was established by Lou [67] using normalized L rc (λ) data at 443, 490, and 555 nm to monitor red tide changes dynamically in the East Lake. Additionally, Lee [104] proposed a newly developed normalized red tide index (NRTI) (calculated with Equations (1)-( 4)), utilizing a spectroradiometer to observe the spectral characteristics of red tides and seawater in real-time.…”

Harmful algal blooms

“…One of the earliest red tide monitoring systems was set up in Japan in 1971 where HAB monitoring is conducted by local governments to look at cell densities and spatial extent and used to develop a "red tide index" (Sakamoto et al, 2020). The red tide monitoring has more recently been focused onto sites where shing activities are most intensive, and the GOCI stationary satellite is also used to increase the temporal resolution of monitoring (Lee et al, 2021). Following the rst PST incidents in 2012, Tasmania invested in training and certication for farmers to perform PST ELISA tests at their farms, where positive tests require conrmation with a laboratory test (Trainer et al, 2020).…”