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Email the author (Login required) Phytoplankton biomass in a Ramsar-listed coastal lagoon of the southern Gulf of Mexico during La Niña 2022 and El Niño 2023 events
Submited: 2024-02-26 18:02:33 | Published: 2024-10-30 20:32:52
DOI: https://doi.org/10.3856/vol52-issue5-fulltext-3231
Abstract
Coastal lagoons are sites recognized for their high biomass and primary productivity levels and are critical habitats for environmental changes. This study evaluated the phytoplankton biomass in the Términos Lagoon (TL), a Ramsar-listed site in the southern Gulf of Mexico, during the 2022 La Niña and 2023 El Niño events. Four systematic sampling expeditions were carried out in April and October of 2022 and 2023 to acquire high-resolution hydrographic data and collect water samples for spectrophotometric determinations of chlorophyll-a (Chl-a) as an indicator of phytoplankton biomass in 11 sites distributed along the TL, while values of the Multivariate ENSO Index (MEI) were used to identify the phase during each sampling expedition. The results showed variations, both seasonally and interannually. MEI values reflected a strong La Niña event during 2022, while in 2023, the ENSO phase moved from neutral (April) to El Niño conditions (October). Consequently, in 2023, the maximum values of the surface temperature and salinity increased by 2.9ºC and 9.2, respectively, compared to 2022. Besides, the maximum values of Chl-a decreased to 0.55 mg m-3 between 2022 and 2023. The horizontal distribution of these parameters displayed interesting gradients along the study area related to each event. Our results demonstrate the impact of La Niña and El Niño events on the hydrographic conditions and phytoplankton biomass of a region recognized for its high species richness contribute to understanding physical-biological coupling processes. This aspect remains poorly understood in the region.
