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Increasing Instability of a Rocky Intertidal Meta-Ecosystem

Citation

Menge, Bruce (2022), Increasing Instability of a Rocky Intertidal Meta-Ecosystem, Dryad, Dataset, https://doi.org/10.5061/dryad.cfxpnvx6j

Abstract

Climate change threatens to destabilize ecological communities, potentially moving them from persistently-occupied “basins of attraction” to different states. Increasing variation in key ecological processes can signal impending state shifts in ecosystems. In a rocky intertidal meta-ecosystem consisting of three distinct regions spread across 260 km of the Oregon coast, we show that annually cleared sites are characterized by communities that exhibit signs of increasing destabilization (loss of resilience) over the past decade despite persistent community states. In all cases, recovery rates slowed and became more variable over time. The conditions underlying these shifts appear to be external to the system, with thermal disruptions (e.g., marine heat waves, El Niño-Southern Oscillation) and shifts in ocean currents (e.g., upwelling) being the likely proximate drivers. Although this iconic ecosystem has long-appeared resistant to stress, the evidence suggests that subtle destabilization has occurred over at least the last decade.

Methods

Estimating Abundances. We initiated the experiment series in 2011 by haphazardly locating, then permanently marking five pairs of 0.5 x 0.5 m low intertidal plots. In July 2011 we photographed, then cleared one plot of each pair of all macrobiota, including macrophytes and sessile invertebrates. Adjacent uncleared reference plots were left intact. Clearances (“disturbed plots”) were allowed to recover without further intrusion for 12 months, when they were photographed and recleared. Experiments were conducted at each of two sites (separated by 0.5 to 10 km) nested within three regions or capes (separated by 61 to 197 km) along ~260 km of the central and southern Oregon coast (SI Fig. S1).

Percent cover of each species was estimated by inspecting annual plot photographs taken after one year of recovery, prior to reclearing. The 0.5 x 0.5 m quadrats were subdivided into 0.1 x 0.1 subquadrats, each consisting of 4% cover. Abundances of each taxon were estimated by eye for each subquadrat, and totals were obtained by adding across all 25 subquadrats. In the ordinations, we grouped species into functional groups (see SI Table S3 for group composition).

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Funding

National Science Foundation, Award: DEB 1050694

National Science Foundation, Award: DEB 1554702

National Science Foundation, Award: OCE 1061233

National Science Foundation, Award: OCE 1735911