The Influence of Canopy Cover on the Ecological Function of A Key Autogenic Ecosystem Engineer

Jacqueline B Pocklington,Tim D O’Hara,Michael J Keough,Alecia Bellgrove

doi:10.3390/d11050079

Jacqueline B Pocklington, Tim D O’Hara + Show 2 more

Open Access

https://doi.org/10.3390/d11050079

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Abstract

Intertidal fucoid algae can function as ecosystem engineers across temperate marine regions. In this investigation, we assessed the function of the alga dominating rocky reefs in temperate Australia and New Zealand, Hormosira banksii. Invertebrate and algal species assemblages were examined within areas of full H. banksii canopy, areas where it was naturally patchy or absent (within its potential range on the shore) and areas where the intact canopy was experimentally disturbed. Differences in species assemblages were detected between areas with natural variation in H. banksii cover (full, patchy, negligible), with defined species associated with areas of full cover. Differences were also detected between experimentally manipulated and naturally patchy areas of canopy cover. Species assemblages altered in response to canopy manipulations and did not recover even twelve months after initial sampling. Both light intensity and temperature were buffered by full canopies compared to patchy canopies and exposed rock. This study allows us to predict the consequences to the intertidal community due to the loss of canopy cover, which may result from a range of disturbances such as trampling, storm damage, sand burial and prolonged exposure to extreme temperature, and further allow for improved management of this key autogenic ecosystem engineer.

Highlights

Canopy-forming seaweeds can function as autogenic ecosystem engineers on rocky seashores, providing a suitable habitat for species that would otherwise be excluded or only occur in low abundance [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
We show that manipulative experiments alone cannot demonstrate that H. banksii is an autogenic ecosystem engineer and habitat provider on Victorian rocky shores
This study investigated the relationship between H. banksii and co-occurring species using mensurative surveys examining natural patterns and experimental manipulations at multiple sites, to determine whether the amount of canopy cover influences the autogenic ecosystem engineering function of H. banksii on Victorian rocky shores

Summary

Introduction

Canopy-forming seaweeds can function as autogenic ecosystem engineers on rocky seashores, providing a suitable habitat for species that would otherwise be excluded or only occur in low abundance [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. What hasn’t been examined in full is whether the fucoid intertidal alga Hormosira banksii functions as an ecosystem engineer under varying densities in the absence of disturbance. Is it dependent on spatial dominance, or can it function as part of a mosaic of habitat density and type? Throughout its range, the fucoid Hormosira banksii is the dominant canopy-forming species on intertidal rocky shores, and unlike studies of fucoids in the northern hemisphere, it has no functional. Victoria, Australia area in Reference and Point. Roadknight, Australia are both very large (see control area [29])

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