Global Chlorophyll Concentration Distribution and Effects on Bottom Reflectance of Coral Reefs

• Published in: Oceans (Basel, Switzerland) Vol. 5; no. 2; pp. 210 - 226
• Main Authors: Bonelli, Ana G., Martin, Paulina, Noel, Phillip, Asner, Gregory P.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.06.2024
• Subjects: Algae; Biodiversity; bottom reflectance; Chlorophyll; chlorophyll-a; Chlorophylls; Clouds; Coral reefs; Ecosystem services; Marine ecosystems; Marine invertebrates; Monitoring systems; ocean color; Oceans; Reflectance; Remote sensing; Satellite imagery; Water; Water column; water column correction; Water depth
• ISSN: 2673-1924; 2673-1924
• DOI: 10.3390/oceans5020013

Despite the limited coverage of coral reefs in the world’s oceans, they play a crucial role in global marine biodiversity and providing essential ecosystem services. This study explores the influence of chlorophyll-a (Chl-a) concentration in the water column on the estimation of bottom reflectance (rb) in coral reefs monitored by the Allen Coral Atlas coral reef monitoring system, using satellite imagery from a Sentinel-2 MSI sensor. We conducted a comprehensive analysis, considering Chl-a global distribution and variability, and its combined effect with water column depth over rb calculation. Our results demonstrated that the impact of Chl-a on rb estimation becomes significant when the water column depth exceeds 3 m. While suggesting the optionality of using regional Chl-a values, our study highlights potential overestimations of Chl-a in optically complex environments, such as along the Brazilian coast. This research contributes to refining coral reef monitoring systems and underscores the importance of accurate Chl-a assessments for robust environmental evaluations.