Geometric morphometrics are a useful tool for studying morphological variation in scleractinian corals, extant and extinct. In the case of modern specimens, three-dimensional features of the calical surface can be measured. These features are rarely preserved in fossil corals, however, necessitating measurement of 2-D landmarks in transverse thin-sections of corallites. Unfortunately, 2-D and 3-D methods often yield differing answers to questions about interspecific, intraspecific and intracolonial variation. This issue is addressed in the present study by directly comparing results of 2-D and 3-D geometric morphometric analyses of identical colonies of extant members of the Montastraea "annularis" species complex. Ten colonies of each extant species in the complex (M. annularis s.s., M. faveolata and M. franksi), identified in the field during collection and verified by molecular data, were selected for analysis. Slabs of colony surfaces and transverse thin-sections from ~1 cm below the surface were cut from tops and edges of each colony. Six corallites from each slab were measured in 3-D using a Reflex microscope, and six measured in 2-D on digital images of each transverse thin-section. Both datasets were explored using geometric morphometric methods and analyzed statistically to address questions related to measurement error, intracolonial variation in corallite morphology between tops and edges of colonies, and interspecific morphological differences. The shape data were superimposed using Procrustes generalized least squares, and examined using principal components and canonical variates analyses. Shape differences implied by axes obtained from PCA and CVA were depicted as deformations using the thin-plate spline, to identify which morphological features are correlated with axes of greatest total variance (PCA) and greatest between-group variance (CVA). Goodall's F-test was used to detect significant morphological differences among species and colony positions. All of the data used in these analyses are available in the supplementary file that accompanies this thesis (see Appendix C for a description of the contents of this file). Measurement error analyses show significant differences among variances associated with replicate measurements of 2-D and 3-D landmarks. In many cases the variance is asymmetrical, and for 2D data especially, this asymmetry coincides with orientation of anatomical features. Significant shape differences between corallites from tops and edges of colonies of M. annularis and M. faveolata are found when 3-D data are used. These intracolonial differences are due in large part to height and shape of the septal margin. As a result, 2-D data are unable to find significant differences within colonies. Both datasets find significant interspecific differences, but different anatomical features are found to be responsible. Important interspecific differences for 2-D data are relative thickness of the corallite wall and lengths of septa and costae. When 3-D data are used, results are most influenced by height of primary and secondary septa above the calical surface, as well as length of septa from the corallite wall toward the columella. Patterns of relative morphological similarity among species also differ between datasets. 2-D data show closest similarity between M. annularis and M. faveolata, while M. faveolata and M. franksi are most similar when 3-D data are used. The former result is consistent with previous 2-D analyses, while the latter conclusion is without precedent. Neither is consistent with relationships inferred using molecular data.

Proefschrift Universiteit van Amsterdam. / Met lit. opg. - Met samenvatting in het Nederlands.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Ronald Henry Karlson, Dept. of Biological Sciences. Includes bibliographical references.

Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 161-182).

Thesis (M.S.)--Georgia Southern University, 2006. / "A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science" ETD. Includes bibliographical references (p. 52-57) and appendices.

Scleractinia (stony corals) are powerful tools in the field of paleoceanography, allowing researchers to reconstruct past ocean conditions based on variations in coral geochemistry. As corals regularly accrete their aragonite skeletons they preserve a history of climate on regional to global scales. Often able to provide centuries long continuous records of climate, an individual coral colony can provide insight into significant environmental perturbations. If preservation permits, fossil corals can be used to evaluate climate thousands of years in the past. Researchers use paleoclimate proxies, which are indirect geochemical fingerprints of environmental conditions, to create paleoclimate time series. Paleoclimate proxies are prevalent throught the literature and while many are well constrained by years to decades of use, individual conditions unique to study sites and timescale prevent the use of blanket assumptions regarding their interpretation. In this dissertation I illustrate the varied ways that the same or similar coral-based climate proxies can be used to reconstruct past ocean conditions. Part I (Ch. 2, 3) presents two studies based along of the Pacific Coast of Panamá to examine the influence of the seasonal migration of the Intertropical Convergence Zone (ITCZ). I analyzed a long-term coral δ18O time series from a living massive Porites colony to address low-frequency variation overprinted by the wet-dry seasonality. The coral record uncovered a clear decadal (~11 year) cycle in coral δ18O-inferred precipitation. I propose this mode is related to basin-wide processes, specifically a component of the Pacific Decadal Oscillation, which describes large-scale patterns in sea surface temperature (SST) and precipitation influencing marine ecosystems. In Chapter 2, I supplement the coral δ18O record with a coral Ba/Ca time series from a different coral colony. Coral Ba/Ca can be used as a proxy for river discharge (Q), although this practice is relatively new. Our coral record outlined seasonal variation in river Q and can also be used to identify past El Niño events and prolonged periods of drought. Uncovering a geochemical indicator of El Niño in this region is particularly powerful since conditions become warm and dry, which negate each other in coral δ18O rendering the proxy unable to consistently identify these climate events. This chapter furthers the community’s understanding of the many ways that trace metals can be used in paleoceanographic research, specifically to constrain local hydroclimate. In Part II (Ch. 4, 5) I present two studies in the Great Barrier Reef (GBR) based on coral δ18O and Sr/Ca records from modern and fossil Isopora, a coral species that is nearly completely absent from the paleoceanographic literature. Although this suite of climate proxies is similar to those used in Part I, in Part II the GBR corals provide a history of sea surface temperature rather than hydroclimate, which is due to prevailing local environmental conditions over a given timescale. In Chapter 4 I developed the first modern Sr/Ca- and δ18O-Sea Surface Temprature (SST) calibration using Isopora, which approaches those calculated for the commonly used Porites corals. Using Isopora in Pacific-based paleoceanographic research allows us to analyze coral records from reefs that might not be dominated by Porites. In Chapter 5 I applied the new Isopora Sr/Ca- and δ18O-SST calibrations to fossil corals recovered during Integrated Ocean Discovery Program (IODP) 25. The fossil corals date beyond the Last Glacial Maximum (LGM, ~20 kyr BP) to 25 kyr BP. In the Pacific SST change since the LGM is better constrained for more equatorial locations so our fossil samples from the GBR extend the geographic network of LGM-aged coral-based climate proxies. I measured ~5-7°C of cooling in the GBR at the LGM compared to today. The SST change through the LGM deglaciation provides valuable understanding of reef resilience and future risk of or adaptability to climate change. Each chapter in this dissertation uses similar strategies but provides a unique perspective on past climate change in the tropical Pacific. This dissertation identifies the many ways that coral proxies can be utilized with specific examples of the ways in which interpretation can vary. It is necessary to consider the environmental specifics of a given region before blindly interpreting paleo-proxy data. Furthermore, coral-based proxy records are supremely powerful tools in exploring and uncovering past climate histories of a given region. Coral-records can supplement and extend the limited instrumental record with centuries to millenia long information on SST and hydroclimate. These data can improve climate models, further our knowledge of coral reef growth, and deepen our understanding of regional hydroclimate, which are all vital to our understanding of global climate.

published_or_final_version / Zoology / Master / Master of Philosophy

The origin of marine biodiversity in the Indo-Pacific is poorly known. Faunal turnover in scleractinian reef corals has been hypothesised over the Miocene-Pliocene boundary (~5 Ma), in the Malay Archipelago. However, there is little information available on origination and extinction events in reef corals during the same period for the broader Indo-Pacific region. This is important because many species probably had a wider distribution than previously thought, and many more genera than has previously been estimated were probably present in the Indo-Pacific during the Neogene. Here I begin to fill the gap in our knowledge by reporting on the taxonomic composition and diversity of Neogene reef coral communities sampled from Indonesia (Salayar), Papua New Guinea (New Britain), and Fiji (Vanua Balavu). Sampling locations were chosen on their reported age, fossil content and preservation quality. Ages were refined using foraminiferal assemblages and Strontium 87/86 isotope ages of samples collected at the sampling locations. This dual approach confirms a middle Miocene to early Pleistocene age range for the collection. I described 155 species of reef forming corals collected across an Indo-Pacific longitudinal gradient. Twenty-two constitute new, extinct species from the genera Alveopora, Astreopora, Caulastrea, Cyphastrea, Echinopora, Euphyllia, Galaxea, Leptoria, Leptoseris, Madracis, Montipora, Platygyra, Symphyllia and Turbinaria. A further 42 taxa could not be assigned to species level due to poor preservation, but may well be additional new, extinct species. I uncovered a general pattern of coral turnover across the Indo-Pacific by investigating the degree to which coral communities (using both presence/absence and relative abundance of both coral species and genera) varied with water depth, time and geographical distribution. Coral communities were found to vary with global sea level and time. Thus global changes in sea level through time potentially drove extinction and origination in Indo-Pacific Neogene corals. Inverse Lyellian analysis indicates that of species present in the Miocene in New Britain, a mean of 41.8% are now extinct, possibly resulting from restricted flow of oceanic currents in that region. Indonesia (mean = 9.4%); and Fiji (mean = 6.6%) both had significantly lower proportions of extinct species. However, there is a decline in the number of extinct species found at any location from the middle Miocene (mean = 23.2%) to the early Pleistocene (mean = 1.8%). This study supports previously proposed models of an early Pliocene turnover event in Scleractinia in the Indo-Pacific.

Thesis (M. Phil.)--University of Hong Kong, 1985.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 274-304).