PHYTOPLANKTON PHENOLOGY PATTERNS DERIVED FROM MODIS-AQUA CHLOROPHYLL-A PRODUCTS IN THE ARGENTINE SHELF FROM 38° S TO 43° S

CELLERI, CARLA; PRATOLONGO, PAULA D.; ARENA, MAXIMILIANO; DELGADO, ANA LAURA

Simposio; VIII International Symposium on Marine Sciences 2022 (ISMS); 2022

Phytoplankton phenology is of critical importance in ocean dynamics as higher trophic levels are sustained by primary producers. In the Argentine Continental Shelf, (Southwestern Atlantic Ocean), the combined origin and varying properties of water masses generates a heterogeneous distribution of phytoplankton productivity. Based on water properties, 3 broad areas have been described: the inner-shelf (El Rincón, ER), the mid-shelf (MS), and the outer-shelf – shelf-break area (OS-SB) between 38° and 43° S. In this work, the areas were further divided by means of unsupervised classification using a time series (2003-2016) of monthly mean Chlorophyll-a values derived from 4-km 8-days composites of MODIS-Aqua Chlorophyll-a products, and phytoplankton phenology patterns were characterized in terms of bloom maximum (mg m-3), bloom duration (days), bloom integral (mg m-3 per season) and bloom start date. Values are presented as mean ± standard deviation. Within ER, 2 areas were identified: the central ER, where season started in March and bloom duration was 192±47 days; and the ER-MS transition, where bloom started later (July) and showed a shorter season (131±40 days). Over the MS, 3 areas were identified. The inner-central MS, showing an intermediate maximum and low integral values (9±2 mg m-3 and 58±16 mg m-3 respectively); the MS front, with higher maximum and integral values (13±2 mg m-3 and 93±18 mg m-3 respectively); and the outer MS, where the main difference was the longer bloom duration compared to the inner-central MS and MS front (105±29, 73±20 and 75±10 days respectively). Finally, the OS-SB zone was divided into the inner OS-SB, with higher maximum (13±2 mg m-3) and integral (119±28 mg m-3) values, and the outer OS-SB where values were lower (7±4 mg m-3 and 63±38 mg m-3 respectively). This study provides a finer regionalization for the study area, based on phytoplankton patterns, setting the basis for future assessments of phytoplankton phenology drivers.