Operational MERIS-based NIR-red algorithms for estimating chlorophyll-a concentrations in coastal waters — The Azov Sea case study

Abstract

a b s t r a c tWe present here results that strongly support the use of MERIS-based NIR-red algorithms as standard tools for estimating chlorophyll-a (chl-a) concentration in turbid productive waters. The study was carried out as one of the steps in testing the potential of the universal applicability of previously developed NIR-red algorithms, which were earlier calibrated using a limited set of MERIS imagery and in situ data from the Azov Sea and the Taganrog Bay, Russia, and data that were synthetically generated using a radiative transfer model. We used an extensive set of MERIS imagery and in situ data collected over a period of three years in the Azov Sea and the Taganrog Bay for this validation task. We found that the two-band and three-band NIR-red algorithms gave consistently highly accurate estimates of chl-a concentration, with a mean absolute error of 4.32 mg m − 3 and 4.71 mg m − 3 , respectively, and a root mean square error as low as 5.92 mg m − 3 , for data with chl-a concentrations ranging from 1.09 mg m − 3 to 107.82 mg m − 3 . This obviates the need for case-specific reparameterization of the algorithms, as long as the specific absorption coefficient of phytoplankton in the water does not change drastically, and presents a strong case for the use of NIR-red algorithms as standard algorithms that can be routinely applied for near-real-time quantitative monitoring of chl-a concentration in the Azov Sea and the Taganrog Bay, and potentially elsewhere, which will be a real boon to ecologists, natural resource managers and environmental decision-makers. (W.J. Moses), agitelson2@unl.edu (A.A. Gitelson), berdnikov@ssc-ras.ru (S. Berdnikov), saprygin@ssc-ras.ru (V. Saprygin), povazhny@mmbi.krinc.ru (V. Povazhnyi).

Water residence time affecting phytoplankton blooms: study case in Ibitinga Reservoir (São Paulo, Brazil) using Landsat/TM images

“…The band ratio TM4/TM3, which includes the Chlorophyll absorption peak in 670 nm and a spectral reflectance peak (fluorescence and phytoplankton cell backscattering) in 700 nm, provided the best performance for mapping chlorophyll-a in eutrophic aquatic systems (Moses et al, 2012;Duan et al, 2007;Zimba and Gitelson, 2006). Novo et al (2013) used in situ Bidirectional Reflectance Factor (BRF) data acquired at Ibitinga reservoir to simulate Landsat/TM spectral bands (TM_sim bands).…”

Monitoring of the 2011 Super Algal Bloom in Indian River Lagoon, FL, USA, Using MERIS

“…The NDCI uses 665 and 708 nm and operates similarly to the Normalized Difference Vegetative Index (NDVI) binding higher and lower index values between −1 and 1 and reducing seasonal variability and sun angle influences. A comparison of the NDCI effectiveness in Case 2 waters of the Chesapeake and Delaware Bays found NDCI was the most effective model, followed by Moses et al [25] and then by Dall'Olmo and Gitelson [23] (Table 1). In a further effort to test the effectiveness of these algorithms for estuarine algal bloom mapping, we chose Moses et al [25] and NDCI [21] to calibrate and validate Chl a in the Indian River Lagoon (IRL), FL a shallow estuary in which severe algal blooms have occurred in recent years Table 1.…”

“…A comparison of the NDCI effectiveness in Case 2 waters of the Chesapeake and Delaware Bays found NDCI was the most effective model, followed by Moses et al [25] and then by Dall'Olmo and Gitelson [23] (Table 1). In a further effort to test the effectiveness of these algorithms for estuarine algal bloom mapping, we chose Moses et al [25] and NDCI [21] to calibrate and validate Chl a in the Indian River Lagoon (IRL), FL a shallow estuary in which severe algal blooms have occurred in recent years Table 1. Comparison of MERIS Chl a estimation algorithms (Adapted from Mishra and Mishra [21]).…”

“…Their primary assumption with this model assumes that TSS affects all three bands equally. Moses et al [24,25] (Referred to as Moses in this paper) proposed returning to a two band ratio between 665 and 708 nm, due to the high rates of variability in three spectral points models. Mishra and Mishra [21] built the two band Normalized Difference Chlorophyll Index (NDCI) in an effort to improve models proposed by Moses et al [25].…”

“…Moses et al [24,25] (Referred to as Moses in this paper) proposed returning to a two band ratio between 665 and 708 nm, due to the high rates of variability in three spectral points models. Mishra and Mishra [21] built the two band Normalized Difference Chlorophyll Index (NDCI) in an effort to improve models proposed by Moses et al [25]. The NDCI uses 665 and 708 nm and operates similarly to the Normalized Difference Vegetative Index (NDVI) binding higher and lower index values between −1 and 1 and reducing seasonal variability and sun angle influences.…”