Phytoplankton phenology patterns derived from MODIS-Aqua chlorophyll-a products in the Argentine shelf from 38° S to 43° S.

CARLA CELLERI; PAULA D. PRATOLONGO; MAXIMILIANO ARENA; ANA L. DELGADO

Las Palmas, Gran Canaria

Congreso; VIII International Symposium on Marine Sciences 2022 (ISMS).; 2022

Phytoplankton phenology is of critical importance in ocean dynamics as highertrophic levels are sustained by primary producers. In the Argentine ContinentalShelf, (Southwestern Atlantic Ocean), the combined origin and varying properties of watermasses generates a heterogeneous distribution of phytoplankton productivity. Basedon 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 usinga time series (2003-2016) of monthly mean Chlorophyll-a values derived from 4-km 8-days composites of MODIS-Aqua Chlorophyll-a products, and phytoplanktonphenology patterns were characterized in terms of bloom maximum (mg m-3), bloomduration (days), bloom integral (mg m-3 per season) and bloom start date. Values arepresented as mean ± standard deviation. Within ER, 2 areas were identified: the centralER, where season started in March and bloom duration was 192±47 days; and the ER-MStransition, 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 intermediatemaximum and low integral values (9±2 mg m-3 and 58±16 mg m-3 respectively); the MSfront, with higher maximum and integral values (13±2 mg m-3 and 93±18 mg m-3respectively); and the outer MS, where the main difference was the longer bloom durationcompared to the inner-central MS and MS front (105±29, 73±20 and 75±10 daysrespectively). Finally, the OS-SB zone was divided into the inner OS-SB, with highermaximum (13±2 mg m-3) and integral (119±28 mg m-3) values, and the outer OS-SBwhere values were lower (7±4 mg m-3 and 63±38 mg m-3 respectively). This studyprovides a finer regionalization for the study area, based on