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Genetic diversity of symbiodinium in selected corals in the Western Indian Ocean.January 2007 (has links)
Coastal communities along the east African coastline rely on coral reefs and their associated resources for food security and income. However, increases in the frequency and severity of episodes of coral bleaching have resulted in mass coral moralities in many locations around the world including the western Indian Ocean (WIO). Reef corals obligately host dinoflagellate algal symbionts of the genus Symbiodinium. Coral bleaching is caused by the loss of these symbionts from the host, resulting from a variety of stresses, the major ones being increased seawater temperature and irradiance. The Symbiodinum genus is diverse and the distribution of symbionts is influenced by the host biology, external light environment and geographic location. Ten distinct clades of Symbiodinium have been identified. Although the Caribbean and Great Barrier Reef have been studied intensively with respect to Symbiodinium diversity in many locations in the WIO Symbiodinium diversity is unknown. The aim of this study was to determine diversity, distribution and prevalence of Symbiodinium types in corals along the east African coastline. The Symbiodinium ssrDNA region was analysed using restriction fragment length polymorphism (RFLP) in order to assess the cladal diversity of Symbiodinium. The results showed all samples analysed to belong to clade C. To gain more insight into Symbiodinium genetic diversity, the ITS region was employed to assess Symbiodinium diversity at the subcladal level. Twenty ITS types were identified. The most prevalent type was found to be subclade C1. No phylogeographic structuring was found amongst the symbiont types, however, specificity of symbiont types to coral hosts was demonstrated indicating potential susceptibility to perturbations such as increased seawater temperature. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2007.
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Community assembly in subtidal macroalgal communities: The importance of environmental gradientsMucciarelli, Valerie 28 April 2014 (has links)
As human activity along coastlines increase, degradation and destruction of coastal marine ecosystems around the globe will increase at an alarming rate. In an effort to mitigate degradation and destruction of coastal marine ecosystems, artificial reefs have been used in restoration and enhancement projects. As artificial reefs are the main method of restoring diversity to a degraded area, it is important to know the mechanisms that drive marine community assembly and diversity on those reefs. Understanding community assembly patterns of foundational species, in particular, may provide insight to community assembly patterns at higher trophic levels. Subtidal macroalgae are commonly seen as foundational species in marine environments and both deterministic and stochastic processes play a role in their assembly. Environmental gradients, which are deterministic processes, play a significant role in structuring subtidal macroalgae communities. Depth, which is negatively correlated with light, is the main driver structuring subtidal macroalgal communities, however, other gradients such as water flow, and distance to a propagule source also impact their assembly. This study sought to determine which environmental gradients play a prominent role in subtidal macroalgal community assembly. To study subtidal macroalgal community assembly, 92 artificial reef units called Reef Balls were deployed east of the Ogden Point Breakwater in Victoria, BC in June 2009. Two years passed to allow for macroalgal growth and early successional processes to occur prior to sampling the communities on thirty Reef Balls via underwater collection in July 2011. Algae were sorted by genus and dry weight was measured. To determine effects of environmental gradients on community assembly light, depth, water flow, distance to the nearest Reef Ball and distance to the breakwater were measured at each Reef Ball. A redundancy analysis revealed that depth was the most significant environmental gradient shaping algae communities and had the greatest effect on upper canopy algae. Spatial plots reveal a depth and coastline zonation of algae genera comprising the canopy. While depth was found to significantly structure algae genera found in the canopy, there was a high degree of unexplained variation in the model. This suggests that unmeasured variables such as colonization and priority effects may be driving algal community structure in the lower canopy. Differences in community structure between upper and lower canopy reveal that multiple mechanisms are responsible for shaping subtidal algal communities. Further study is required to determine the importance of stochastic colonization events and priority effects. / Graduate / 0329 / vmucciar@uvic.ca
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Community assembly in subtidal macroalgal communities: The importance of environmental gradientsMucciarelli, Valerie 28 April 2014 (has links)
As human activity along coastlines increase, degradation and destruction of coastal marine ecosystems around the globe will increase at an alarming rate. In an effort to mitigate degradation and destruction of coastal marine ecosystems, artificial reefs have been used in restoration and enhancement projects. As artificial reefs are the main method of restoring diversity to a degraded area, it is important to know the mechanisms that drive marine community assembly and diversity on those reefs. Understanding community assembly patterns of foundational species, in particular, may provide insight to community assembly patterns at higher trophic levels. Subtidal macroalgae are commonly seen as foundational species in marine environments and both deterministic and stochastic processes play a role in their assembly. Environmental gradients, which are deterministic processes, play a significant role in structuring subtidal macroalgae communities. Depth, which is negatively correlated with light, is the main driver structuring subtidal macroalgal communities, however, other gradients such as water flow, and distance to a propagule source also impact their assembly. This study sought to determine which environmental gradients play a prominent role in subtidal macroalgal community assembly. To study subtidal macroalgal community assembly, 92 artificial reef units called Reef Balls were deployed east of the Ogden Point Breakwater in Victoria, BC in June 2009. Two years passed to allow for macroalgal growth and early successional processes to occur prior to sampling the communities on thirty Reef Balls via underwater collection in July 2011. Algae were sorted by genus and dry weight was measured. To determine effects of environmental gradients on community assembly light, depth, water flow, distance to the nearest Reef Ball and distance to the breakwater were measured at each Reef Ball. A redundancy analysis revealed that depth was the most significant environmental gradient shaping algae communities and had the greatest effect on upper canopy algae. Spatial plots reveal a depth and coastline zonation of algae genera comprising the canopy. While depth was found to significantly structure algae genera found in the canopy, there was a high degree of unexplained variation in the model. This suggests that unmeasured variables such as colonization and priority effects may be driving algal community structure in the lower canopy. Differences in community structure between upper and lower canopy reveal that multiple mechanisms are responsible for shaping subtidal algal communities. Further study is required to determine the importance of stochastic colonization events and priority effects. / Graduate / 0329 / vmucciar@uvic.ca
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The effects of eutrophication on clionid (Porifera) communities in Barbados, West IndiesHolmes, Katherine E. (Katherine Elizabeth) January 1996 (has links)
Samples of Porites porites rubble were collected from across three fringing reefs which lie along a eutrophication gradient in Barbados, West Indies. The coral skeleton fragments were examined for clionid sponges. Data collected from the reef crest and fore reef zones and from across the range of distances and depths were pooled for each reef to compare indices of sponge abundance along the eutrophication gradient. Significant differences between the reefs were found for the proportion of rubble invaded (ANCOVA, p = 0.004), number of invasions per sample (ANCOVA, p = 0.002), and number of species per sample (ANCOVA, p = 0.018) but not for total surface area of sponge invasions per sample (ANCOVA, p = 0.064). All the indices demonstrated an increase with increasing eutrophication level. Clionids were found in nearly twice as many of the pieces collected from the most eutrophic site (41%) as from the least eutrophic (24%). Since clionids may be the principal bioeroders of coral reefs, an increase in their abundance due to excessive pollution likely results in greater bioerosion of affected reefs. The mean abundance of Type 3 corals was found to be positively related to the frequency of boring sponge invasion, suggesting that increased bioeroision may be partly responsible for community shifts toward Type 3 corals in polluted waters. One new variety and three new species of boring sponges of the genus Cliona were found. A new variety of C. amplicavata Rutzler is described, Cliona species 2 of MacGeachy is redescribed and Cliona species 4 and Cliona species 5 are described for the first time. Cliona species 5 may become an important bioeroder in Barbados and other Caribbean islands since it flourishes under high eutrophic conditions which are beginning to plague West Indian reefs. (Abstract shortened by UMI.)
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Reproduction and recruitment in the bluehead wrasse Thalassoma bifasciatum in BarbadosHunt von Herbing, Ione January 1988 (has links)
No description available.
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Changes in coral community structure in Barbados : effects of eutrophication and reduced grazing pressureAllard, Patrick, 1968- January 1993 (has links)
Multivariate ordination techniques were used to characterize the direction and magnitude of coral community changes on west coast reefs in Barbados between 1982 and 1992, and to relate these changes to coastal eutrophication and variation in Diadema antillarum densities (grazing pressure). D. antillarum densities were substantially lower in 1992 than in 1982, reflecting the 1983 mass mortality event. Reductions in urchin density were greater on less eutrophic reefs than eutrophic reefs. Cover by macrophytic algae increased, cover by crustose coralline algae decreased, and the number of coral species decreased between 1982 and 1992. With the notable exception of the most eutrophic reef, coral cover decreased over the 10 year period. Changes in algal cover across reefs between 1982 and 1992 were strongly correlated with decreases in D. antillarum densities, and were therefore typically greater on less eutrophic reefs, indicating that reduced grazing pressure has more strongly influenced algal cover changes than prevailing eutrophication levels. Coral species composition changed at all sites between 1982 and 1992, and except at the most eutrophic site, the direction of change was directly related to reduced D. antillarum densities and associated algal cover changes. Temporal change at the most eutrophic site was best explained by the prevailing high level of eutrophication, and resulted primarily from a substantial increase in the cover of one species, Porites porites. The decrease in coral cover that occurred on most of the study reefs in the face of the increasing cover by macrophytic algae was typically accompanied by an increase in the relative abundance of Type 1 (high recruitment, high natural juvenile mortality) to Type 2 (low recruitment, low natural juvenile mortality) corals.
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Spatial and Temporal Dynamics of Andros Coral Communities: Long-Term Assessments and the Development of Improved Community Evaluation ToolsGintert, Brooke E 14 December 2011 (has links)
Understanding recent decades of coral community change has been hindered by a shortage of long-term monitoring and a lack of tools that provide a lasting record of benthic reef communities. To increase our understanding of Caribbean coral reef dynamics, this dissertation research developed and used innovative technologies involving landscape mosaic images and 3D reef models, to analyze a novel 40 year dataset of coral community health from Andros Island, Bahamas. Historical data from Andros Island (1968-2000) were provided as part of a Cooperative Research and Development Agreement (CRADA) between the University of Miami and the Naval Undersea Warfare Center Division Newport. Long-term monitoring at Andros Island revealed that reef decline was a-typical over recent decades. Coral mortality and disease increased significantly between 1970 and 2000, whereas macroalgal cover did not. To complement studies of coral mortality and disease, the resilience and resistance of individual coral species at Andros were measured from 1972 to 2008. Of the 24 species studied, only three (Siderastrea siderea, Montastraea cavernosa, and Porites astreoides) were resistant to recent disturbance histories, whereas Porites porites was resilient. Further studies using 3D models explored relationships between coral population dynamics and spatial patterns of coral species. Results indicated that the arrangement of dominant coral species and the processes of recruitment, growth, and mortality were non-random over time. In summary, the application of mosaic images and 3D reef models to a previously un-published long-term coral health dataset led to improved understanding of factors controlling past reef communities.
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Evaluation of nearshore coral reef condition and identification of indicators in the main Hawaiian islandsRodgers, Kuʻulei S January 2005 (has links)
Missing leaves: 170. / Mode of access: World Wide Web. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 190-203). / Electronic reproduction. / Also available by subscription via World Wide Web / xvi, 203 leaves, bound ill. (chiefly col.), col. maps 29 cm
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The Effect of Temperature and Light on the Stable Isotopic Compostition of Reef Coral SkeletonsWeil, Sandra M. 05 1900 (has links)
The reef corals Pocillopora damicornis and Montipora verrucosa were
cultured under various controlled temperatures and light conditions at
Ulupau Head Microcosm facility. The skeletal carbonate deposited under
different experimental regimes was analyzed for 13C and 18O. Coral skeletal
013C values varied with light dose and correlated with changes in
zooxanthellar pigment. The o13C value of skeletal aragonite seems to be
controlled by oxidation of photosynthetically produced organic matter.
Functionally significant relationships between coral skeletal o18O
values and temperature have been determined. The temperature coefficients
of the o18O values (-4.20) are the same as the first order coefficient
in the equilibrium paleotemperature equation, but the o18O
values have species-specific offsets from equilibrium. These offsets
may be attributed to the activity of the coral's zooxanthellae. Based
upon the results of this study a model of coral skeletal isotopic incorporation
is presented. / Typescript. Thesis (M. S.)--University of Hawaii at Manoa, 1979. Bibliography: leaves 94-102.
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Distribution, Recruitment and Development of the Borer Community in Dead Coral on Shallow Hawaiian ReefsWhite, Janet K. F. 12 1900 (has links)
Twenty-seven species of known or suspected coral skeletal
borers were identified from shallow Hawaiian reefs. In
comnarison to inventories of the borer communities collected
from other tropical areas Hawaiian corals had an abundance
of polychaetous annelids, fewer species of sipunculans,and
acrothoracican barnacles, and far fewer boring sponges.
Polychaetes were responsible for the majority of the
bioerosion of dead coral in Kaneohe Bay, Oahu.
Comparisons of living and dead sections of coral colonies
indicated that the borer community was more diverse and
abundant in areas of the skeletons lacking living tissue.
Skeletal densities of three common coral species with branching
growth form were found to influence the abundance of coral
borers. The least dense skeletons had greater population
densities of borers. It is suggested that these three species
of corals can coexist in close proximity due, in part, to the
development of varying abilities to withstand invasion by
skeletal borers.
In order to determine rates, si te preference and seasona.li.ty
of settlement a series of settlement plates were cut from coral
and placed in the field at ten sites in Kaneohe Bay, Oahu.
Extrapolating from the surface area of the settlement plates,
mean recruitment rates of coral borers were found to be
10,000 - 50,000 individuals m-2 month-1. The recruitment
rates and species composition of epibiotic and borer faunas
settling; on the dead coral plates differed dramatically between
areas in Kaneohe Bay due to the effects of differences in
physical and biological factors caused by sewage and slltation.
The larvae of coral borers generally lacked clear
seasonal settlement periods, suggesting that one or more
mechanisms (e.g. continuous reproduction, long pelagic phase,
etc.) functioned to assure the presence of larvae throughout
the year. The ultimate cause for the development of such a
strategy may be that the time and location of the production of
suitable settlement sites on the reef surface is. unpredictable.
Some of the larvae of both epibiotic and borer species exhibited
settlement selectivity with respect to the position of the
settlement surface. This finding indicates that the distribution
of borers in coral skeletons might be due, in part, to active
selection by the laryae for particular conditions.
Development of the epibiotic and borer communities of dead
coral was monitored using sequentially collected blocks cut
from the coral Porites lobata. The abundance and species
composition of these communities were found to differ between
sites in Kaneohe Bay because of several biological and physical
factors. In the south bay increased food supplies (in the
form of plankton and plankton-derived detrital material).
due to sewage enrichment, support extensive populations of
filter and deposit-feeding invertebrates including coral
borers. Sewage diversion did not appear to have had any
dramatic effect on these communities by the end of the study
period. In the north bay, where food availability is lower,
fewer borers and epibiotic organisms were collected.
The effects of fish grazing are considered to be another
important factor determining the species composition and
abundance of the coral borer community. Grazing fish were
rare in south Kaneohe Bay during the study period, which may
help to explain the abundance of sessile epifaunal species.
In the north bay fish grazing is extensive and contributes
to the growth of encrusting coralline algae on the test blocks
and the benthos.
Based on the results of the long term block study it was
found that in Hawaii sessile filter-feeding invertebrates do
not exclude coral borers from the substratum or inhibit their
growth. In south Kaneohe Bay, where conditions caused
increased abundances and growth rates of filter and depositfeeding
invertebrates, bioerosion rates were accelerated.
Encrusting coralline algae, which flourish on reefs exposed to
fish grazing (eg. north Kaneohe Bay), inhibit settlement of
borers and grow over burrow apertures, thus reducing the
population of borers within the dead coral. Bioerosion rates
of exposed, coralline algal covered, dead coral substrata
are very low on pristine shallow Hawaiian reefs. / Bibliography: leaves 181-192.
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