BIBLIOS

Document type
Journal articles

Document subtype
Full paper

Title
The effects of grazing on the distribution and composition of low-shore algal communities on the central coast of Portugal and on the southern coast of Britain

Participants in the publication
Diana Boaventura (Author)
IMAR - Instituto do Mar / Laboratório Marítimo da Guia
Matthew Alexander (Author)
University of Southampton
Paolo Della Santina (Author)
University of Southampton
Nicholas D Smith (Author)
University of Southampton
Pedro Ré (Author)
DZA - Faculdade de Ciências, Universidade de Lisboa
IMAR - Instituto do Mar / Laboratório Marítimo da Guia
Luís Cancela da Fonseca (Author)
INSTITUTO DE INVESTIGAÇÃO DAS PESCAS E DO MAR
IMAR - Instituto do Mar / Laboratório Marítimo da Guia
Stephen J Hawkins (Author)
University of Southampton

Summary
A red algal turf is often found just below the barnacle/limpet zone of many European shores, especially on steep shores of moderate exposure. The hypothesis that grazing by limpets determines the upper limit of distribution of this red algal turf was tested on moderately exposed shores in Portugal and Britain. We also aimed to assess whether the grazing effect is modified at various spatial scales. Grazers were excluded by fences, with half-fenced and unfenced controls. Exclusion plots were rapidly colonised by green ephemeral algae in the months immediately after the beginning of the experiment (summer); these algae were later replaced by perennial algae. The percentage cover of turf-forming macroalgae showed a significant increase at both locations. The upper limit of distribution extended more than 50 cm on most of the shores studied. In contrast, control and half fenced plots remained devoid of algae. After 2 years, ungrazed plots were mainly colonised by a red algal turf (e.g. Caulacanthus ustulatus, Gelidium spp., Laurencia pinnatifida) in Portugal, while canopy cover (Fucus serratus and Himanthalia elongata) dominated in Britain in marked contrast to the grazed plots. Physical factors acting at both local and geographical scales may explain these differences. However, although physical factors probably have an important influence on the identity, size and abundance of sublittoral fringe macroalgae, grazers play a major role in directly setting their upper limits. The effect of grazing by limpets was not consistent for all of the morphological algal groups and spatial scales considered in the present study. The effect of grazing on the cover of turf algae varied between Portugal and Britain (location scale), while effects on ephemeral and canopy algal cover varied at the shore scale within location.


Where published
Journal of Experimental Marine Biology and Ecology

Publication Identifiers
ISSN - 0022-0981

Publisher
Elsevier BV



Document Identifiers
DOI - https://doi.org/10.1016/s0022-0981(01)00372-0
URL - http://dx.doi.org/10.1016/s0022-0981(01)00372-0

Keywords
Grazing Macroalgae Upper limits Distribution patterns Intertidal Rocky shores