11th ICRS Abstract book - Nova Southeastern University

24.1076
Herbivore Effects On Coral And Algal Population Dynamics
Sarah DAVIES* 1 , Peter VIZE 1
1 Biological Sciences, University of Calgary, Calgary, AB, Canada
Regime shifts from coral to algal dominated communities have been well documented
and herbivores have been shown to participate in these ecological shifts in community
structure. Throughout the Caribbean, coral degradation is increasing and algal dominated
communities are becoming more common. Competition and overgrowth by algal species
appear to negatively affect coral recruitment success. Several preliminary studies indicate
that increasing herbivore density facilitates an increase in coral growth.
Our project aims to test the effects of herbivores on recruitment and survival of
scleractinian corals at the Flower Garden Banks National Marine Sanctuary (FGBNMS),
Gulf of Mexico. A controlled environment has been constructed on a sand patch at a
depth of 23 m. It consists of a galvanized steel platform measuring 6 x 6 m. Nine large
fiberglass bins have been attached to this platform, each of which contains one of three
herbivore treatments (Diadema antillarum, Cerithium litteratum, no herbivores).
Artificial tiles are used as settlement substrates within each bin and high-resolution
photography will monitor long-term recruitment and survival patterns of all settling
organisms.
Coral recruitment fluctuations can have profound repercussions on the management of
corals reefs. Low recruitment rates being observed on Caribbean reefs will likely result in
slow reef recovery after natural or anthropogenic disturbances. Promoting recruitment
has been suggested as a solution to reduce the long-term decline of coral communities
and gaining baseline knowledge about coral population maintenance is essential to reef
longevity.
24.1077
Effect Of Herbivore Exclusion On The Survivorship Of Hatchery Reared Acropora
Tenuis Spats
Maria Vanessa BARIA* 1 , James GUEST 2 , Porfirio ALIÑO 1 , Andrew HEYWARD 3
1 The Marine Science Institute, University of the Philippines, Quezon City, Philippines,
2 School of Biology, Newcastle University, NE1 7RU, United Kingdom, 3 Australian
Institute of Marine Science, Crawley, Australia
Post-settlement mortality is one of the critical stages in the life a coral, however little is
known about the effect of herbivory on post-settlement survivorship of coral spat.
Herbivorous fish may affect coral spat survival in two ways, mortality may increase if
small spat are grazed accidentally or mortality may be reduced if herbivores prevent spat
being overgrown or killed by macroalgae and other benthic biota. This study was
conducted to understand the mechanisms affecting the survival of one-month old coral
spats of Acropora tenuis specifically the influence of grazers and algal density at two
depths, 4 and 9 m. Larvae of A. tenuis were reared in the hatchery facility at Bolinao
Marine Laboratory in north-western Philippines as part of work to develop low cost coral
larval rearing for reef restoration. Settled spat were placed on the reef approximately 40
days after settlement in three treatments, caged, open sided cage and no cage. Although
the density of turf algae was higher in the cage treatment, survivorship of coral spats was
significantly lower in the uncaged set-ups at both shallow and deep sites after 3 months
(4.72 and 10.5% respectively). Higher survivorship was observed in cages at 9 than 4 m
deep (33% and 17% respectively). It is likely that accidental grazing of algae on the
uncaged settlement plates contributed the to lower survivorship, although shading may
also have played a role. Further research is needed to see if survivorship in cages
decreases at a later stage due to overgrowth by other biota and whether survivorship is
enhanced if spat are settled on substrata with rough surfaces (to provide possible refuge
from grazers). The results of this study are relevant to reef restoration studies that aim to
use larval rearing and outplanting of coral spat.
Poster Mini-Symposium 24: Reef Restoration
24.1078
Considerations For Experimental Transplantations Of Diadema Antillarum
Aaron ADAMS* 1 , Erich BARTELS 2 , Robert MILLER 3 , John EBERSOLE 4 , Cory WALTER 2 ,
Ken LEBER 5
1 Mote Marine Laboratory, Pineland, FL, 2 Mote Marine Laboratory, Summerland, FL,
3 University of California Santa Barbara, Santa Barbara, CA, 4 University of Massachusetts
Boston, Boston, MA, 5 Mote Marine Laboratory, Sarasota, FL
Diadema antillarum experienced a Caribbean-wide mass mortality in 1983-84. Recent localized
recovery has been documented throughout the Caribbean, with reduced algal cover and
increased coral recruitment. However, even within locations, Diadema density is extremely
patchy. The combination of patchy distribution, potential for recovery, and Diadema’s
importance as a key herbivore, has prompted some to recommend Diadema transplantation as a
potential reef restoration tool. Recent experiments, however, suggest caution must be used
when considering transplantation as a viable method for Diadema stock enhancement and/or
restoration.
Recent research in the Caribbean showed positive density-dependence whereby juvenile
Diadema survival was greater in areas of high adult densities. This approach was expanded in
the upper Florida Keys, where a grid of 30, 1m2 live-rock reefs was constructed on open sand
bottom. Two transplant experiments showed similar results. In experiment 1, reefs were stocked
with 0, 1, and 4 adult urchins to reflect estimated post-die-off, present, and pre-die-off densities
in the upper Florida Keys, and 0 or 3 juveniles. Loss of transplanted Diadema was 100% when
the reefs were surveyed 100 days later. In the second experiment, 3 (20 reefs) or 4 (9 reefs) (one
reef received no urchins) adult Diadema were transplanted to each reef, and reefs were
monitored routinely over an 137 day period. Initial loss of urchins was gradual, with loss rate
increasing after 27 days (abundance declined by 37%). By 137d, loss was 92%. Since
juveniles generally do not migrate, their loss was likely due to predation. Loss of adults may
have been due to combined emigration and predation (evidence of predation was observed in
experiment 2). Relatively high natural mortality rates, lack of retention of transplanted
individuals in other research, and the high loss during these experiments indicates additional
research is needed before transplantation is used as a restoration tool.
24.1079
The Effectiveness of Macroalgal Reduction and Diadema antillarum Addition in
Maintaining Algal Turfs and Facilitating Coral Recovery
David BURDICK* 1
1 Guam Coastal Management Program, Hagatna, Guam
The effectiveness of macroalgal reduction and Diadema antillarum addition in maintaining
algal turfs and facilitating coral recovery was investigated between June 2002 and July 2003.
Two treatments, one involving the manual reduction of macroalgae (A), and the second
involving macroalgal reduction followed by the addition of D. antillarum (B), were each
performed on a set of three replicate patch reefs (4-8m2) off the island of Eleuthera, The
Bahamas. Macroalgal cover was reduced to