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Marine Ecology Progress Series

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MEPS 651:57-69 (2020)  -  DOI:

Disturbance intensity, disturbance extent and ocean climate modulate kelp forest understory communities

Thomas Wernberg1,2,*, Marine Couraudon-Réale1, Fernando Tuya3, Mads Thomsen1,4

1UWA Oceans Institute & School of Biological Sciences, University of Western Australia, Crawley, WA 6009, Australia
2Department of Science and Environment (DSE), Roskilde University, Roskilde 4000, Denmark
3Grupo en Biodiversidad y Conservación, IU-ECOAQUA, Universidad de Las Palmas de Gran Canaria, Las Palmas 35010, Spain
4Marine Ecology Research Group and Centre for Integrative Ecology, School of Biological Sciences, University of Canterbury, Christchurch 8041, New Zealand
*Corresponding author:

ABSTRACT: Disturbances often control community structure by removing large dominant species, allowing new species to colonize. Disturbances vary in intensity and extent, and their effects on resident communities can depend on local environmental conditions. We tested the effects of disturbance intensity and extent on different functional groups of understory species in kelp forests at 4 locations along an ocean climate gradient in Western Australia. We hypothesized that, compared to intact canopies, increasing disturbance intensities (50 and 100% of kelp removal) and extents (2, 4 and 8 m diameter) would promote light-dependent competitors (turf, foliose, articulated coralline and fucoid seaweeds) at the expense of less light-dependent functional groups (invertebrates and encrusting seaweeds). We also hypothesized that these effects would be most pronounced at warmer relative to cooler locations, where metabolic and ecological rates are faster. The first hypothesis was supported; light-dependent understory groups (turfs, in particular) increased, while less light-dependent groups (crusts in particular) decreased with increasing disturbance regimes. However, the second hypothesis was not supported; even though understory communities differed between locations and turf covers were highest at the warmest location, we found no significant interactions between locations and disturbance regimes. Importantly, our results revealed that even small-scale partial canopy loss can have significant effects on kelp-associated communities. The implied community-wide, density-dependent effects have implications for the management and conservation of kelp forests, because restoration of ecological functions must also consider the density of kelp forests, not simply their presence or absence.

KEY WORDS: Disturbance · Facilitation · Ocean climate · Western Australia · Temperate reefs · Functional groups · Ecklonia radiata

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Cite this article as: Wernberg T, Couraudon-Réale M, Tuya F, Thomsen M (2020) Disturbance intensity, disturbance extent and ocean climate modulate kelp forest understory communities. Mar Ecol Prog Ser 651:57-69.

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