Data validation for SDG Indicator 14.1.1a Index of coastal eutrophication in Latin America ; Report from Argentina

HERNANDO, M.; DOGLIOTTI, A.; DÍAZ JARAMILLO, M.; GONZALEZ, M.; LOMOVASKY, B.; MOREIRA, D.

2022-11-07/2023-01-17

Biológica

Sanidad ambiental-Preserv.de rec.hidricos

This technical document reports the activities and preliminary results obtained during a field campaign conducted by Argentina under the project Data validation for SDG Indicator 14.1.1a Index of coastal eutrophication in Latin America. Data were collected from four sampling sites in the south coast of the Rio de la Plata (RDP), Buenos Aires, Argentina on november 16th 2022. Sampling sites included riverine areas differing in their distance to drinking water intake sources (St01, St03 and St04) and one off-shore area at 7.5 km from coast (St02). The maximum phytoplankton biomass was observed at St04 (Bernal, City), followed by St03 (Quilmes city), with average total Chl values of 50 µg L-1, being Skeletonema sp the dominant diatom species followed in abundance by Thalassiosira sp, Cyclotella sp. and Aulacoseira sp. St02 (off-shore area) showed the lower phytoplankton biomass (in average 5 µg L-1), also dominated by Skeletonema  sp in the diatom group. However, at this offshore station located far from St03 (with high phytoplankton biomass), the dominant group were small coccoid phytoflagellates with an average of 60% of relative abundance in the phytoplankton assemblage. Also at St03 and St04 both potentially toxic cyanobacteria Microcystis sp. and Planktothric sp. were observed. The high phytoplankton biomass observed at St04 and St03 and changes in the specific composition on phytoplankton assemblages may be due to stream freshwater inputs to RDP that crosses Quilmes and Bernal cities. This stream carries a large concentration of under-treated sewage waters. In addition, phytoplankton blooms observed in this report, were coincident with high temperature conditions and high pH values, which increased with depth until a maximum at 1.5 m under the euphotic zone conditions. The Shannon-Wiener biodiversity index using microalgae ranged from 1 to 3 in all sampling sites. However, a slight decrease was observed at 1.5 m depth. Conversely, phytoplankton biomass collected at subsurface waters (1.5 m depth) was higher compared to surface waters (0.5 m depth). The evaluation of different atmospheric correction showed a better performance of algorithms that use the SWIR bands (like ACOLITE-DSF and S3 standard L2 product), given the high amount of sediments, while general atmospheric failure is found when standard L2 that uses NIR bands are tested, like VIIRS standard Level 2.