Spatial and temporal patterns of nekton communities in different subhabitats of Maritime Canadian salt marshes

Salt marshes are composed of a mosaic of subhabitats including intertidal creeks, the marsh platform, and salt pools. During tidal inundation, these subhabitats function together to provide habitat to nekton (fish and crustaceans). We determined nekton community compositions and spatiotemporal scales of variation between two biophysical regions with contrasting tidal regimes in Maritime Canada, on a seasonal basis (April‒November) in 2022‒2023. Bay of Fundy salt marshes with their megatides have higher marsh platform elevations and lower inundation times, compared to Northumberland Strait salt marshes with their microtides. The nekton community was speciose with a distinct composition between regions (accounting for up to ~40% of the variation) mostly reflecting different dominating species (Fundulus heteroclitus, Microgadus tomcod, sticklebacks, and Crangon septemspinosa) and varied seasonally (accounting for ~20% of the variation) reflecting transient and resident strategies. Subhabitat (in a separate presence-absence PERMANOVA) also accounted for a large portion of the compositional variation (~30%). Notably, creek and platform nekton communities differed regionally, while salt pool communities were more similar. Identifying community structure in salt marsh subhabitats across seasons enhances the understanding of nekton habitat function of this ecosystem in Maritime Canada.