11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 2: Biotic Response to Ancient Environmental Change in Indo-Pacific Coral Reefs
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Differential response of Southeast Asian and Caribbean reef ecosystems to global
environmental change during the Oligocene/Miocene Transition
Kenneth JOHNSON* 1
1 Palaeontology Department, Natural History Museum London, London, United Kingdom
The paleoceanographic record contains several intervals during the Cenozoic in which
apparently rapid global change in the open ocean also had effects on tropical coastal
marine ecosystems. One example is the Oligocene/Miocene transition (OMT) that
occurred approximately 25-20 Ma. This interval is associated with the termination of a
Late Oligocene warm interval by a 'snap' glaciation and development of a stable globallycooler
climate phase during the Early Miocene. These changes are contemporaneous with
the initial constriction of deep water connections across the Indonesian Throughflow as
Australia collided with Eurasia. A database of specimen-based occurrences of reef corals
was assembled from both new and existing collections to document the history of coral
diversity and the regional extent of reef development in the Caribbean and Southeast Asia
during the OMT. All specimens were examined to verify taxonomic identifications and
collections were placed within a consistent stratigraphic framework. During the Late
Oligocene there was widespread reef building by a moderately diverse biota in the
Caribbean. Both diversity and the extent of reef building had crashed by the Early
Miocene in response to increased regional surface productivity. In contrast, there was
little reef building and low diversity of reef builders in the Late Oligocene of SE Asia.
Instead both reef-building and reef-coral diversity in the region increased during the
OMT. Therefore, the effects of global change caused a decline in reef-coral diversity and
reef-building in the Caribbean but an increase in reef building and radiation of reef-corals
in Southeast Asia. The fact that regional biotic responses were out of phase in Southeast
Asia and the Caribbean indicates that the ecological signal of global environmental
change is modulated by local to regional-scale biotic and oceanographic history.
2-6
Indo-Pacific Coral Growth Forms Through The Miocene To The Pliocene
Kate BROMFIELD* 1 , John PANDOLFI 1
1 University of Queensland, Brisbane, Australia
One of the most intriguing questions for the evolution of the modern Indo-Pacific coral
reef fauna is the antiquity of modern branching-dominated coral assemblages. The
Miocene (21-6 Ma) of the Indo-Pacific is a period of pronounced first occurrences of reef
coral species, and a complete reorganisation of coral communities has been proposed;
from a Miocene fauna dominated by massive growth forms, to reef domination by corals
with branching morphologies in the Pliocene. Many genera of modern reef corals (order
Scleractinia), are thought to date from the early Pliocene (5.6-3.2 Ma), around 5.3 Ma.
This study tested the Miocene/Pliocene growth form transition hypothesis from uplifted
reefs at three sites along a longitudinal gradient: Vanua Balavu (16.9-6.7 Ma) in Fiji;
New Britain (14.8-12.3 Ma) in Papua New Guinea; and Selayar (5.8-1.4 Ma) in
Indonesia.
The collection includes 121 coral species, fifteen of which are new, though now extinct.
The highest percentage (25%) of newly recorded, extinct species occurred in the late
Pliocene (5.8-3.4 Ma) reef deposits of Selayar. Newly described extinct species from the
Miocene deposits of Fiji and Papua New Guinea averages 6%. The data shows no
significant change in either the relative abundance or the presence versus absence of
growth forms among the three sites and times. Miocene assemblages contained 27%
abundance of branching individuals and the Pliocene contained 23%. This challenges the
premise that reefs underwent a transition from those dominated by massive forms to
those dominated by branching forms during this period. However, our study corroborates
the previously proposed model of an origination event in reefal corals in the early
Pliocene.
2-7
Biodiversity And Biogeography Of Mollusca During The Cenozoic: A Database Approach
To The Assessment Of Spatial Patterns And Their Relationship To Global Environmental
Change
Austin HENDY* 1
1 Geology and Geophysics, Yale University, New Haven, CT
A focal point in the Phanerozoic trajectory of global biodiversity has been its apparent rapid
increase since the end-Cretaceous extinction. The interval stimulates additional interest through
the availability of chronologically well-constrained information on changing global
paleoenvironments. This knowledge aids understanding of how the Cenozoic diversification of
marine invertebrate faunas was influenced by developing global paleogeography, major tectonic
shifts, and related climatic transitions.
An extensive dataset (http://paleodb.org) of fossil molluscan occurrences permits analysis of
how spatial components of global biodiversity vary through the Cenozoic, specifically how
faunas are partitioned biogeographically and how these biogeographic units relate to one
another. On a global scale, sampling-standardized diversity appears to have increased at most
only 50% over the course of the Eocene-Pleistocene, showing small drops during the Early
Oligocene and a slight decline since the Middle Miocene. Nevertheless, there is remarkable
stage-to-stage independence in the shape of diversity curves at the regional scale, reflecting
both regionally distinct environmental controls and variable data quality, related to reduced
sample size. A multivariate analysis of global biogeography reveals that provinciality has
increased only slightly during this interval, peaking in the Plio-Pleistocene, although this
patterns is strongly influence by spatial sampling intensity. A strengthening latitudinal gradient
of diversity is observed through the Neogene, reflecting an increased in not only tropical
diversity but also a decline in the richness of faunas from temperate and polar latitudes.
Fluctuations in regional endemism and biogeographic similarity between regions appear related
to the opening and closing of major oceanic gateways. Nevertheless some aspects of global and
regional diversity patterns reflect Cenozoic-scale climatic transitions, expressed by an Early
Oligocene decline. The influence of deteriorating global climate through the Neogene appears
to be offset by a steepening latitudinal diversity gradient and an associated increased late
Neogene provinciality.
2-8
Molluscan Biodiversity in Shallow Carbonate Platforms (Indonesia)
Frank WESSELINGH* 1
1 Geology, Naturalis, Leiden, Netherlands
A pilot study into the spatial distribution of mollusc taxa in the shallow carbonate platform, the
Spermonde Archipelago (Sulawesi, Indonesia) is presented. The very high species numbers and
the unresolved taxonomical status of the far majority of these mollusc species should cripple
such a documentation. However, by using taxa groups with an as low as possible taxonomic
rank, very clear distribution patterns and associations are found. This study shows that
molluscan associations probably are a very good tool for study of communities, facies and
biodiversity in ancient carbonate platform settings as well.
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