Using successional drivers to understand spatiotemporal dynamics in intertidal mudflat communities

Abstract

Elucidating factors (“drivers”) that influence succession after disturbance can explain ecological phenomena, including why communities vary spatiotemporally. To gain insight on drivers related to habitat availability, species availability, and species performance during succession, we conducted two field experiments on infaunal communities in intertidal mudflats, one on each of the Atlantic and Pacific coasts of Canada, that had disturbances of different type, size, and frequency. Related to habitat availability drivers, we observed that disturbance type and size, which differed between experiments, did not change end patterns of succession; however, disturbance frequency, directly assessed in one experiment, did. Dispersal of species from surrounding mudflat and water column (species availability) was the primary driver of succession, whereas local interactions between species after colonization (species performance drivers) did not have a detectable effect. We suggested that ample space and resources diffused competition and predation effects, and so species replacements did not occur in our systems, resulting in a lack of “traditional” successional dynamics as observed in other ecosystems. Our findings that community composition in intertidal mudflats is strongly influenced by species availability on two different coasts suggest that this driver may be key to variation in intertidal mudflat communities elsewhere.

Structuring forces of intertidal infaunal communities on the northern coast of British Columbia, Canada: assessing the relative importance of top-down, bottom-up, middle-out, and abiotic variables

“…Gerwing et al (2016) also hypothesized that priority effects (pre-emptive competition) may be a primary force structuring infaunal communities. However, we now suggest, based on our present study in combination with recent studies on recovery of the infaunal community following various disturbances (Thrush et al 2003;Gerwing et al 2017aGerwing et al , 2018aCox et al 2019;Sizmur et al 2019;Campbell et al 2019a;Gerwing et al 2022c;Norris et al 2022) that colonizers and subsequent infaunal community composition may reflect regional species pools and the variables that influence these pools. More research is required to evaluate this hypothesis.…”

“…Instead, community trajectories appeared to be strongly influenced by species availability, particularly regional species pools, and not by the order of species arrival. Following disturbance and then establishment, infaunal community structure (species composition and abundances) increased in similarity to the surrounding areas (Beukema et al 1999;Thrush et al 2003;Gerwing et al 2017a;Campbell et al 2019a;Cox et al 2019;Gerwing et al 2022c;Norris et al 2022). Regional species pools have been implicated in structuring other marine invertebrate communities (Weslawski 2003;Witman et al 2004;Somerfield et al 2009;de Juan and Hewitt 2011), and we posit that they may play a substantial role in structuring intertidal infaunal communities both on small and large scales.…”

“…However, studies of infaunal community recovery from anthropogenic and natural disturbances along the Pacific and Atlantic coasts of Canada suggest that priority effects may not be the predominant force structuring these communities (Norris et al 2022). Instead, community trajectories appeared to be strongly influenced by species availability, particularly regional species pools, and not by the order of species arrival.…”

“…Given the unique characteristics of Bay of Fundy mudflats, it is unclear whether the hypotheses of Gerwing et al (2016) can be applied to other mudflat or tidal flat communities. Moreover, field studies focused on infaunal community recovery from anthropogenic and natural disturbances along the Pacific and Atlantic coasts suggest that priority effects may not be the predominant force structuring these communities (Norris et al 2022). Instead, community trajectories may be strongly influenced by species availability, particularly regional species pools (Beukema et al 1999;Thrush et al 2003;Gerwing et al 2017a;Campbell et al 2019a;Cox et al 2019;Gerwing et al 2022c;Norris et al 2022).…”

“…Moreover, field studies focused on infaunal community recovery from anthropogenic and natural disturbances along the Pacific and Atlantic coasts suggest that priority effects may not be the predominant force structuring these communities (Norris et al 2022). Instead, community trajectories may be strongly influenced by species availability, particularly regional species pools (Beukema et al 1999;Thrush et al 2003;Gerwing et al 2017a;Campbell et al 2019a;Cox et al 2019;Gerwing et al 2022c;Norris et al 2022). As such, more work is required to better understand the suite of forces structuring infaunal communities.…”