Jolliffe, Alistair S. (1997) Ecological role of herbivory on coral reefs of the Saudi Arabian Gulf coast. PhD thesis, University of Warwick.

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Abstract

This study examined the ecological role of herbivory on coral reefs of the Saudi Arabian Gulf coast.
Herbivory is a ubiquitous process and important in regulating benthic marine communities. Three reef
sites were studied over a 12-month period; one on an inshore fringing reef (1.5 m depth), and two on
the fringing reef surrounding an offshore island (3 m and 11 m depth). The inshore site experienced
greatest extremes in temperature, salinity and sedimentation.
The ecological role of herbivory was determined from algal settlement plates and their selective
exclusion from herbivores. The inshore site was naturally dominated by filamentous algae, while both
offshore sites supported a higher proportion of crustose forms. Location (i. e. distance from shore)
appeared to be more important than seasonality in determining the structure and composition of the
epilithic algal community. At the inshore site herbivorous fish (dominated by Siganus spp. ) imposed a
uniform, wide-ranging grazing pressure of intermediate intensity. Herbivorous echinoids (Echinometra
mathaei) imposed an intensive but localised grazing pressure. At the shallow offshore site, only
herbivorous fish (dominated by Scarus sp. ) appeared responsible for grazing impacts, which were also
intensive. At the deep offshore site both herbivorous fish (dominated by Pomacentrus spp. ) and
echinoids (Diademo setosum) were responsible for limiting algal growth, although other factors (e. g.
light penetration) may also inhibit algal productivity at this site. An experiment assessing the effects of
extreme perturbations (i. e. removal of the algal community), showed that seasonal life-history strongly
affected generic succession and rate of re-colonisation. Perturbation effects were temporary and did not
precipitate permanent alternative stable communities.
An important secondary effect of herbivory is bioerosion. The mean erosion rate by E. mathaei was
comparable to rates recorded elsewhere. Behavioural studies revealed that burrow defence and fidelity
were positively correlated with burrow complexity, and that the frequency of agonistic behaviour was
low. Foraging range was negatively correlated with burrow complexity. In addition, the risk of
mortality by finfish predators at the inshore site was estimated to be very low.
The study has shown that Saudi Arabian Gulf reef communities may be particularly vulnerable to the
depletion of herbivores, for example by overfishing. Management plans should therefore safeguard the
herbivorous community, in order to maintain natural bioerosion rates and other reef processes.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QH Natural history
Library of Congress Subject Headings (LCSH):	Coral reef ecology -- Persian Gulf Coast (Persian Gulf States), Algae, Herbivores
Official Date:	April 1997
Dates:	Date Event April 1997 Submitted
Institution:	University of Warwick
Theses Department:	Department of Biological Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Price, Andrew, 1950-
Extent:	xvii, 329 p.
Language:	eng

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