Seasonal pattern of autothropic biomass and productivity in a microbially-dominated biosedimentary ecosystem from a temperate estuary

Abstract

Environmental factors such as nutrient availability, tidal cycles, salinity shifts, and solar radiation influence photo-autotrophic microbes in coastal sediments. The paradigm for temperate regions states that seasonal variations further shape microbial communities, often leading to peaks in primary production during warmer months and declines in winter. While this pattern has been well-documented in Northern Hemisphere estuaries, less is known about its applicability to temperate ecosystems in the Southwest Atlantic. This study examines seasonal changes in microphytobenthic composition, biomass, and CO₂ fluxes in two tidal flats colonized by epibenthic microbial mats within the Bahía Blanca Estuary, Argentina. A net capture of CO₂ was observed during Austral fall, with the highest accumulation of standing carbon stocks occurring in winter. These findings challenge traditional assumptions about seasonal productivity in microbial biosedimentary systems, suggesting that temperate estuaries with similar biological communities may exhibit regionally distinct dynamics. Understanding these localized processes is crucial for assessing the role of microbially-dominated ecosystems in carbon cycling and their potential as CO₂ sinks in the context of climate change mitigation.