Dynamic regionalization of the Panama Bight, Eastern Tropical Pacific, using remote sensing data

Abstract

ABSTRACT This study establishes the dynamic biogeographic regions (DBGRs) of the Panama Bight (PB) based on remote-sensing reflectance (Rrs412 and Rrs488) of the MODIS-Aqua sensor and the sea-surface temperature (SST) and the concentration of chlorophyll a (Chl-a) derived from the same sensor. Monthly images with a spatial resolution of 4 km from the MODIS-Aqua sensor were used for July 2002–July 2020. To define the DBGR, the first standardized empirical orthogonal function (SEOF1) was calculated. Due to the low spatial variability in the PB, the number of DBGRs found with the analysis of the SST and Chl-a was lower than that found in the analysis of the Rrs. Therefore, the DBGRs of the PB were delineated based only on the study of the Rrs. The PB was divided into 11 DBGRs belonging to two provinces: oceanic and coastal. Five of the DBGRs were coastal, the others oceanic, including a transition one. The coastal regions were characterized by the highest averages of Chl-a and high SST. On the other hand, the regions located northeast of the PB (Panama Gulf, PB-transition, and Choco) were characterized by an average SST greater than 28°C and an average Chl-a between 0.8 and 1.0 mg·m−3. The DBGRs located further west (west and PB-west) showed an average SST greater than 28°C and the lowest concentrations of Chl-a. The DBGRs PB-east and PB-central, presented average SSTs of 26.7–27.1°C and average Chl-a concentrations lower than 0.5 mg·m−3. The south Ecuador DBGR presented the lowest average SST (<25 °C) and average Chl-a of 0.50 mg·m−3. Our approach allowed us to generate a dynamic regionalization of the PB, which most of the year has small SST and Chl-a gradients, making this an alternative to the homogeneous areas generated from the thermohaline structure.