11th ICRS Abstract book - Nova Southeastern University

12.417
Atypical Coral Skeletal Morphologies Under Non-Optimal Growth Conditions:
Caribbean Examples From Lagoon Reefs With High Sedimentation And Turbidity
Iain MACDONALD* 1,2
1 Qatargas, Doha, Qatar, 2 Environmental and Geographical Sciences, Manchester
Metropolitan University, Manchester, United Kingdom
This study describes unusual coral colony morphologies and skeletal adaptations that are
exhibited in response to conditions of high sedimentation and turbidity. The areas
investigated were Columbus Park reef and Red Buoy Patch reef, which are located within
Discovery Bay, north Jamaica, and which are characterised by conditions of high
turbidity and moderate to high rates of sedimentation and sediment accumulation. At
these sites, framework development decreases with depth, and the sediments exhibit a
progressively higher proportion of material in the mud size fraction. Coral morphological
responses to these conditions included 1) the occurrence of platy corals and / or closelytiered
platy growth morphologies of corals (cf. the “show shoe effect”; Thayer, 1975), 2)
skeletal evidence from Siderastrea siderea and Montastraea annularis of extreme polyp
tissue retraction and subsequent rejuvenation (cf. the “phoenix effect”; Krupp et al.,
1992) followed by full colony morphology regeneration (cf. the “pancake stack”
morphology; Hillis and Bythell, 1998), and 3) skeletal evidence from Agaricia lamarcki
for rapid, colony wide, vertical “catch-up” growth that reduces colony weight to volume
ratios, and which may facilitate coral growth in order to catch-up or surmount local
sediment accumulation. A few examples comparable to Thayer’s (1974) “ice-berg effect”
were also noted. These observed morphological responses to turbid and high
sedimentation environments may help answer the paradox of coral survival within such
apparently inhospitable nearshore environments. Furthermore these skeletal
morphologies have significant potential to be preserved in the fossil record and thus have
application to the detailed interpretation of palaeoenvironmental conditions and life
histories at the individual coral colony level providing potential criteria for interpreting
coral growth strategies within fossil coral-rich sequences.
12.417A
Variation in Bleaching Susceptibility Among Color Morphs in The Reef-Building
Coral acropora Millepora, Great Barrier Reef (Gbr)
Allison S PALEY* 1,2 , Caroline V PALMER 2,3 , Line K BAY 2 , Bette L WILLIS 1,2 ,
Madeleine JH VAN OPPEN 4
1 School of Marine and Tropical Biology, James Cook University, Townsville, Australia,
2 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville,
Australia, 3 School of Biology, University of Newcastle, Newcastle Upon Tyne, United
Kingdom, 4 Australian Institute of Marine Science, Townsville, Australia
Color polymorphisms, a common feature among reef-building corals, are primarily
determined by the relative abundances of a suite of green fluorescent proteins (GFPs). In
addition to their roles in coloration, GFPs may also modify internal light environments
and play roles in reducing oxidative stress, yet little is known about the variation in
bleaching sensitivity among coral color morphs. Historical data indicate that the relative
abundance of three color morphs of Acropora millepora have changed on the GBR
concomitantly with an increase in sea surface temperatures and bleaching frequency
highlighting the potential role of color in bleaching sensitivity. To determine the
relationships among color morph variation, relative GFP levels and bleaching sensitivity
we investigated the distribution and abundance of color morphs of the common coral A.
millepora among seasons and sites in the central GBR, and the relative fluorescence of
the three known pigments (cyan, green and red). We then examined the response of the
three color morphs of this species during natural and experimental bleaching events.
Relative abundances of color morphs were significantly different, and although some
colonies appeared to change color among seasons, the green morph had consistently
lower abundance across all sites, at all times. Relative fluorescence of the three
fluorescent proteins associated with A. millepora varied significantly among color
morphs. Bleaching sensitivity was variable among colonies but not color morphs during
a mild natural bleaching event, suggesting that color does not influence thermal tolerance.
Because of the apparent influence of microhabitat on natural bleaching, variation in color
morph sensitivity was further tested in a controlled bleaching experiment. These findings
are relevant in understanding potential changes in coral populations if bleaching becomes
more prevalent in the future.
Poster Mini-Symposium 12: Reef Resilience
367