Synergistic Effect of Multi-Sensor Data on the Detection of Margalefidinium polykrikoides in the South Sea of Korea

Abstract

Since 1995, Margalefidinium polykrikoides blooms have occurred frequently in the waters around the Korean peninsula. In the South Sea of Korea (SSK), large-scale M. polykrikoides blooms form offshore and are often transported to the coast, where they gradually accumulate. The objective of this study was to investigate the synergistic effect of multi-sensor data for identifying M. polykrikoides blooms in the SSK from July 2018 to August 2018. We found that the Spectral Shape values calculated from in situ spectra and M. polykrikoides cell abundances in the SSK were highly correlated. Comparing red tide spectra from near-coincident multi-sensor data, remote-sensing reflectance (Rrs) spectra were similar to the spectra of in situ measurements from blue to green wavelengths. Rrs true-color composite images and Spectral Shape images of each sensor showed a clear pattern of M. polykrikoides patches, although there were some limitations for detecting red tide patches in coastal areas. We confirmed the complementarity of red tide data extracted from each sensor using an integrated red tide map. Statistical assessment showed that the sensitivity of red tide detection increased when multi-sensor data were used rather than single-sensor data. These results provide useful information for the application of multi-sensor for red tide detection.

Quantification of Margalefidinium polykrikoides Blooms along the South Coast of Korea Using Airborne Hyperspectral Imagery

“…Red tide patches vary significantly within a few meters and tend to move with ocean currents or winds. Shin et al [29] confirmed that red tide patches moved slightly northward between two satellite images obtained within 1 h. Thus, the difference between the sampling time used to estimate in situ cell abundances and HSI acquisition time can reduce verification accuracy. In particular, because M. polykrikoides is characterized by vertical migration, the difference in sampling time can be an important factor affecting performance.…”

“…Figure 1 shows in situ sampling locations used for the field survey and the flight lines of the hyperspectral images. Red, green, and blue dots indicate the sampling locations of the field surveys conducted on 7-8 August 2018 [29], 30-31 August 2019, and 25-26 September 2019, respectively. Black boxes show the flight routes used to acquire HSI at the time of the field surveys.…”

“…Table 1 summarizes information such as the dates and station numbers of field surveys and airborne monitoring. We conducted four field surveys, in 2019, and used additional data by Shin et al [29]. Overall, a total of 49 pairs of in situ spectra and M. polykrikoides cell abundances were obtained.…”

“…The second index is the SS index, which was developed by Tomlinson et al [13]. The SS index utilizes the spectral shape around 490 nm, which is useful for detecting M. polykrikoides and K. brevis [5,20,21,25,29]. Here, it employs the SeaWiFS wavelengths of 443, 490, and 510 nm.…”

Special Issue on Selected Papers from the “International Symposium on Remote Sensing 2018”

“…Shin et al [14], in their paper entitled "Synergistic Effect of Multi-Sensor Data on the Detection of Margalefidinium polykrikoides in the South Sea of Korea", performed a feasibility test to detect Margalefidinium polykrikoides blooms by identifying a possible synergistic effect of multi-sensor data. Their results showed that the detection performance of Margalefidinium polykrikoides blooms increased when multi-sensor data were used.…”