Reefs At Risk

Nicholas Polunin N.Polunin at
Thu Jun 25 06:19:21 EDT 1998

Dear Colleagues

In response to messages from Les Kaufman and others, Bob Steneck just 
>However, before we all run off to conduct remedial action, it might 
>be a good idea to objectively determine the patterns of reef 
>decline. Are we faced with a decline in all species or are we 
>primarily reacting to the decline of Acroporids (due to white band 
>disease)?  Are patterns of macroalgae resulting from changes in the 
>reef's trophic structure (i.e., loss of grazers) or due to 
>eutrophication or both?  

I shall also remain unhappy with thinly-substantiated reports from 
environmentalist groups, international environmental agencies and 
NGOs as to the extent and manner of degradation of Caribbean reefs 
until I see reliable regional comparisons, and preferably 
time-series, of condition (not proxy assessments of  'threat' or 
'risk'), made and disseminated. As to mechanisms, any geographic 
patterns discerned need rigorously to be related to the sorts of 
factors involved.

Bob also wrote:
>It seems to me, understanding the patterns of coral reef condition 
>sufficiently so that plausible forcing-function processes can be 
>identified should be a priority action item for our coral reef 
>research community.  I think we do need to collectively consider 
>which reefs are at risk, but we should also identify which reefs are 
>seriously degraded and which ones are relatively pristine. With such 
>information we should be better able to apply our remedial actions

My group's particular approach has been to get an idea of the scope 
for recovery of the benthic community (based on photoquadrat 
point-sampling) when fishing is effectively excluded or fish grazing 
might otherwise be manipulated by:

(1) comparing protected and unprotected areas at 5 Caribbean sites; I 
will give a provisional view of these data at the ISRS meeting in 
Perpignan this September:

Ecological comparisons of fished and protected areas in the Caribbean

Polunin, N.V.C. & I.D. Williams, Department of Marine Sciences &
Coastal Management, University of Newcastle, Newcastle upon Tyne NE1

Concern over reef degradation in the Caribbean and the contention that
much of this is caused directly or indirectly by fishing have prompted
us to make comparisons between protected (MPAs) and unprotected areas
in Jamaica (Montego Bay), Barbados (Folkestone), Belize (Hol Chan),
the Caymans (Grand Cayman) and Cuba (Punta Frances), during the period
1997/98. We have broadly categorised the reef benthos from point
counts on underwater photographs in six principal categories
(macroalgae, turf algae, `bare' substratum, crustose coralline algae,
hard coral and other sessile invertebrates) and characterised the
large-fish assemblages of the reefs involved using underwater visual
point counts of individuals >12 cm in length in six families
(Serranidae, Lutjanidae, Balistidae, Scaridae, Acanthuridae and
Haemulidae). The data presented here are derived from replicated
sampling in 5-6 sites selected at random each from MPA and adjacent
unprotected deeper water (ca 15 m depth) reef. Some groups of large
fishes which are important fishery targets tended to be more abundant
in MPAs than on unprotected reef in all except the Caymans, but we
found no evidence that the benthos systematically differed. Since
diving tourists in a Jamaican survey indicated greater preference for
fish (abundance, variety and size, in that order) than characteristics
of the benthos when they dive, it appears that the Caribbean MPAs we
have examined are distinctive in the ways diving tourists most
appreciate. However, the evidence is also that reef degradation,
particularly the domination of macroalgae over hard corals, which has
been attributed to reduced grazing by fish as a result of intensive
fishing in localities such as on the northern coast of Jamaica, does
not stand to be readily reversed in the deep-water sites we have
investigated. Furthermore, the high abundance of macroalgae in areas
which appear at least to be devoid of nutrient and fishing effects
(the Belize and Cuban localities studied) suggests either that some
factor other than local nutrient inputs and fishing has been involved,
or that long-range effects, such as of nutrient additions through
large-scale mixing, must have been important, unless macroalgal
domination greatly predates modern developments. 

Acknowledgements. This study has been funded by the UK Department for
International Development, and has been possible by collaboration of
many colleagues. In particular we thank: Jill Williams, Maldon Miller,
Wayne Hunte, Jorge Angulo, Tim Austin and Miguel Alamilla.

(2) comparing benthic community structure among areas with 
de facto variations in the abundance of grazing fishes.

The results of both approaches will be presented formally at a 
workshop in Jamaica in July 1999. We are drawing up plans for the 
workshop now, and welcome suggestions of other input. 
Possibilities exist for part-funding of some participants, especially 
from developing countries within the Caribbean region.

Nicholas Polunin

Dept of Marine Sciences
University of Newcastle
Newcastle upon Tyne NE1 7RU
Tel +44 191 222 6675/6661
Fax +44 191 222 7891

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