First record of red-tide in Elba protectorate coast using Sentinel-3 and its impacts on ecosystem

Abstract

This study is the first to document an algal bloom caused by Noctiluca scintillans, which was detected using remote sensing techniques and confirmed in the field along the coast of Elba National Park. Noctiluca scintillans is a phytoplankton species that accumulate toxic ammonia that endangers various organisms, including fish, birds, mammals, and human. Therefore, monitoring red tide is essential for water pollution control and management. This study aims to evaluate the potential of the recent launch of the Ocean and Land Color Instrument (OLCI) onboard the Sentinel-3 satellite to identify chlorophyll-a (Chl-a) as a proxy for an algal bloom event and study its impacts on the ecosystem. To fulfill the aim, OLCI images were collected over the study area from the 25th of May to the 13th of June 2017. Satellite images were converted from level 1 to level 2 through radiometric and atmospheric correction, and Chl-a maps were produced from the level 3 data during product development using standard Ocean Color 4 for MERIS (OC4Me) model. The time-series analyses of the Sentinel-3 satellite images indicated that the algal blooms (Red tide) event occurred four days at the studied sites (7th to 10th of June). The current findings reveal a strong relationship between the deterioration in water quality criteria and Noctiluca scintillans cell counts (×104) /L (0.05 > P ≤ 0.01). This study strongly urges routine monitoring of the physicochemical characteristics of coastal waters and using remote sensing techniques for early rid tide detection to control the phenomenon.