Interactions between herbivorous fish guilds and their influence on algal succession on a coastal coral reef

Herbivory is an important mechanism affecting algal succession, particularly on coral reefs where the relationship between algae and corals is largely controlled by herbivores. However, different functional groups of herbivores may have contrasting effects on succession, which may explain different...

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Bibliographic Details
Published in:Journal of experimental marine biology and ecology 2011-03, Vol.399 (1), p.60-67
Main Authors: Ceccarelli, D.M., Jones, G.P., McCook, L.J.
Format: Article
Language:English
Subjects:
Agnatha. Pisces
Algal farming
Amphiroa
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
cages
Caging experiment
coral reefs
corals
ecological succession
fish
Fundamental and applied biological sciences. Psychology
grazing intensity
herbivores
Herbivory
Inshore reefs
macroalgae
Marine
monitoring
overfishing
Polysiphonia
Sargassum
Sea water ecosystems
Synecology
Territorial damselfish
Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
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Summary:Herbivory is an important mechanism affecting algal succession, particularly on coral reefs where the relationship between algae and corals is largely controlled by herbivores. However, different functional groups of herbivores may have contrasting effects on succession, which may explain different trajectories of coral reef recovery after disturbance. Here, the effects of different herbivore groups (roving herbivores = foragers and territorial damselfish = farmers) were isolated by a multi-factorial experiment carried out on a coastal coral reef with high macroalgal cover, high farmer densities and relatively low forager abundance. The effects of foragers and farmers were distinguished by monitoring algal succession on settlement tiles placed inside and outside exclusion cages, with orthogonal treatments established inside and outside damselfish territories (with appropriate cage controls). Within 12 months, algal assemblages on ungrazed tiles inside exclusion cages proceeded rapidly from fine filamentous turfs, to corticated algae, to tough erect (e.g. Amphiroa spp.) and foliose (e.g. Peyssonnellidae) calcified algae. Farmers had a dramatic impact on succession, essentially arresting the development of the algal community at a point where it was dominated by palatable filamentous algae of the genus Polysiphonia. Fleshy macroalgae such as Sargassum spp. were excluded from farmer territories. In contrast, foragers did not suppress fleshy macroalgae, but rather, appeared to decelerate succession and promote a relatively diverse assemblage. In contrast to forager-dominated reefs, farmer territories did not appear to function solely as forager exclusion areas or promote algal diversity as a result of intermediate grazing pressure. The relatively strong effects of farmers observed here may represent a future scenario for coral reefs that are increasingly subject to overfishing of large grazing fishes. ► Succession in ungrazed treatments rapidly proceeds to tough calcified algal groups. ► Farmers arrest succession to a dominance of preferred species, suppressing fleshy macroalgae. ► Foragers at low densities decelerate succession, allowing higher algal diversity.
ISSN:0022-0981
1879-1697
DOI:10.1016/j.jembe.2011.01.019