Functional diversity of benthic macrofauna during and after an el niño event in a subtropical estuary.

Bioturbation promoted by benthic macrofauna impacts the biogeochemical processes in the sediment and water column, being an important process in estuaries, which are depositional ecosystems of high ecological importance. Functional diversity provides clear connections between biota and environmental variables, enabling researchers to comprehend the structure and functioning of ecosystems. The functional approach is still an emerging field of studies for estuaries, especially in the context of weather events such as the ENSO – El Niño. We investigated the functional diversity on a sandflat in the Patos Lagoon Estuary, regarding the bioturbation related traits of the benthic macrofauna, during and following the 2002/2003 El Niño event. Our study evidenced that the decrease in salinity caused by the high precipitation during the El Niño was the most influential factor affecting the functional diversity of the macrofauna. This led to assemblages with less potential for bioturbation, decreased stability, and higher prevalence of opportunistic traits. We also found that despite using bioturbation related traits for our analysis, the proportions of sand, silt, and clay in the sediment were not the main drivers of changes in the functional indices or trait composition, presenting less influence than the seasonal variation of temperature. [Display omitted] • Changes in salinity due to the El Niño were the most influential environmental factor affecting the functional diversity. • Although the traits studied related to bioturbation, sediment composition had a minor influence over functional diversity. • Sediment reworking and irrigation, with different taxa as the most influential, both varied similarly due to the ENSO. [ABSTRACT FROM AUTHOR]