Benthic macrofauna responses to consecutive freeze and flood events across habitats in a subtropical, low-inflow estuary

Low-inflow estuaries in subtropical regions experience intermittent acute rainfall and infrequent extreme cold events. In February 2021, Baffin Bay, TX, USA, was exposed to freezing temperatures for approximately seven days, followed by a freshwater flooding event three months later. We examined the response of benthic macrofauna to these successive freeze and flood disturbances. Within the bay, a unique and diverse benthic macrofauna community inhabits biogenic serpulid reef habitat, while surrounding soft sediments support far fewer organisms. Soft-sediment benthic macrofauna demonstrated minimal changes in abundance, biomass, richness, and diversity, remaining within historical ranges. In contrast, serpulid reef benthic macrofauna had lower biomass and richness after the freeze and increased abundance and richness after flooding, often outside historic records. Despite these fluctuations, reef macrofauna consistently had higher abundance, biomass, richness, and diversity than soft-sediment communities, and exhibited more stable community composition relative to historical variability. These findings highlight the importance of structurally complex habitats in supporting benthic community stability with increasing climate variability. • Benthic macrofauna responses to consecutive freeze and flood events were evaluated in a subtropical, low-inflow estuary. • The 2021 freeze reduced serpulid reef fauna richness and biomass but caused minimal change in soft-sediment communities. • Freshwater flooding increased benthic macrofauna abundance and biomass, particularly in soft-sediment habitats. • Soft sediment fauna were resistant to change, while serpulid reef communities were resilient and stable in composition.