Travis G. Gerwing, Alyssa M. Allen Gerwing, David Drolet, Myriam A. Barbeau, Diana J. Hamilton
Northeastern Naturalist 22 (m12), 1-44, (1 October 2015) https://doi.org/10.1656/045.022.m1201
We examined biotic and abiotic variables on the expansive intertidal mudflats of the upper Bay of Fundy, Canada, at 8 geographically separate sites over 2 years (2009–2011). Invertebrate density, surface density of primary producers (mainly diatoms, measured as chlorophyll-a concentration), shorebird- and fish-foraging activity, and sediment properties varied considerably through time and space. Dissimilarity in the invertebrate community between consecutive sampling rounds was lower during peaks in density and richness (June–August) than during periods of low density and richness (December–March). All but one site located within Chignecto Bay (one arm of the upper Bay of Fundy) had similar invertebrate communities; sites within the Minas Basin (the other arm of the upper Bay) had more distinct communities compared to Chignecto Bay mudflats. The amphipod Corophium volutator, Copepoda, Ostracoda, and the polychaetes Phyllodocidae and Spionidae were usually main contributors to observed community differences over space and time. Although our sites are all silt-dominated mudflats, mean particle size, sediment penetrability, and depth to the apparent redox discontinuity potential (aRDP, a measure of sediment-oxygen content) were usually main contributors to site differences in sediment conditions. However, when we pooled samples over sites and sampling rounds, percent water content and percent organic-matter content accounted for the majority of the variation in sediment properties, likely reflecting within-site patchiness. Such quantification of spatiotemporal patterns in biotic and abiotic variables is an essential first step in the development of predictive models or the design of manipulative experiments to investigate ecological relationships.