Impact of multiple disturbances and stress on the temporal trajectories and resilience of benthic intertidal communities

Abstract

Coastal ecosystems face severe environmental change and anthropogenic pressures that affect both the structure and functioning of communities. Understanding the response and resilience of communities that face multiple simultaneous disturbances and stresses becomes essential. We observed the recovery of a rocky intertidal subarctic macrobenthic community dominated by a macroalgal canopy (Fucus spp.), a habitat-forming species, over a period of 14 months. Using 0.25-m 2 plots, we ran an in situ onepulse experiment (removal of all materials to bare rock and then burning of the surface) followed by a full orthogonal factorial design of three press-type disturbances or stresses: grazer reduction, canopy removal, and nutrient enrichment. We evaluated the single and interactive effects of the three disturbances and stresses on species diversity and abundance structure. Of all the main effects, canopy removal has the most severe impact, resulting in decreased biomass, richness, and diversity, as well as an altered community structure. Canopy-removed plots had fewer invertebrates and more ephemeral algae; beyond this, however, there was minimal effect from grazer reduction and nutrient enrichment acting individually. We categorized the interaction types of all significant interaction effects: Canopy removal had a dominant effect over grazer reduction on richness, and it also dominated over nutrient enrichment on diversity and evenness. Nutrient enrichment and canopy removal had a negative synergistic interaction effect on richness at the end of the experiment. Without stressors, 11 months were required to achieve full recovery. The three stressors affected recovery time differently, depending on the identity and the number of stressors. Three stressors generally increased the time of recovery or even prevented recovery from being fully attained. Moreover, community structure and composition of plots subjected to the triple-stressor treatment had not fully recovered by the end of the study. Our results suggest that multiple stressors may interact on community indices and structure and that their interaction cannot be predicted from the outcome of single stressor studies. The inclusion of multiple disturbances and stresses in field experiments provides a better understanding of the mechanisms that shape community structure and their functioning following various forms of disturbance.

Multiple stressors and disturbance effects on eelgrass and epifaunal macroinvertebrate assemblage structure

“…Most of our treatments did not affect species richness, confirming that complementary metrics (e.g. diversity-related indices, univariate and multivariate data, see Cimon & Cusson 2018) are required to document the effects of stressors on community stability.…”

The Subhabitat Dependence of Biogeographic Pattern

“…Identifying the abiotic and biotic drivers of those alongshore changes necessarily remained beyond this study's reach. To address that goal, it would be necessary to have location-specific information on, for example, nutrient concentration (Kraufvelin et al, 2006;Vinueza et al, 2014), influences of upwelling and surf zone on planktonic food supply and larval transport (Schiel, 2004;Menge and Menge, 2013;Shanks and Morgan, 2018), benthic disturbance (Cimon and Cusson, 2018), and interspecific interactions (Menge, 1995;Harley, 2011). However, the Nova Scotia coast lags behind other coasts of the world on such details.…”

Multiple Driver Impacts on Rocky Intertidal Systems: The Need for an Integrated Approach

“…The outcome of multiple-driver scenarios cannot be predicted by single-driver experiments alone due to the complexity of potential interacting effects among drivers and their physicochemical dynamics (Przeslawski et al, 2015;Gunderson et al, 2016;Boyd et al, 2018;Cimon and Cusson, 2018). Such interactions can be synergistic or antagonistic (Piggott et al, 2015; see Box 2 for a detailed description).…”

“…Studies about the impact of multiple drivers on the resilience of rocky shore communities are rare. In a recent study, Cimon and Cusson (2018) applied a full factorial experimental design to test the effect of an initial short-term driver (pulse disturbance) and three following constant drivers (press disturbances) on a benthic intertidal community. Comparing grazer reduction, canopy removal and nutrient enrichment, they found synergistic effects when driver combinations included nutrient enrichment.…”

“…Comparing grazer reduction, canopy removal and nutrient enrichment, they found synergistic effects when driver combinations included nutrient enrichment. As single driver, canopy removal had the most pronounced effect on composition and function, resulting in a changed community structure (Cimon and Cusson, 2018). They found that recovery was never achieved after introducing those three drivers.…”