Local Environmental Habitat Templates and Hydroperiod Contingency Jointly Shape Benthic Macroinvertebrate Dynamics in Tropical Choked Coastal Lagoons

Abstract Coastal lagoons are highly dynamic transitional ecosystems in which benthic macroinvertebrate communities are shaped by spatial and temporal environmental filters. However, the relative importance of lagoon-specific conditions versus temporal variation remains poorly resolved, particularly in the tropics. Here, we investigated benthic macroinvertebrate assemblages in three neighboring choked coastal lagoons in southeastern Brazil over 23 consecutive months. We tested whether the local environment at the lagoon sites or temporal variability primarily structured richness, abundance, and community composition. We recorded 30,221 individuals across 14 taxa. Abiotic and biotic structure differed strongly among sites, with persistent environmental differences among the sampled sites representing the dominant axis of variation. Sedimentary characteristics and salinity were the main environmental predictors associated with community composition. Temporal variation was significant mainly at the hydroperiod-within-year scale, whereas month-level effects were weak or inconsistent. The polyhaline and hypertrophic site (Piratininga Lagoon) exhibited the lowest richness and abundance, pronounced temporal collapses, and dominance by tolerant and opportunistic taxa, patterns associated with recurrent dystrophic events. In contrast, the oligo/mesohaline and mesotrophic sites supported the highest abundances, but communities were strongly dominated by a few taxa (Maricá) or displayed intermediate compositional and temporal patterns (Jaconé). Our results indicate that coastal lagoons should not be interpreted as temporally fluctuating versions of the same ecosystem, but rather as ecologically distinct systems locally shaped by persistent environmental templates onto which temporal variability is superimposed. These findings highlight the importance of integrating hierarchical spatial and temporal approaches when assessing benthic dynamics in tropical coastal lagoons and reinforce the need for local conservation and monitoring strategies.