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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Escaping The Heat: Range Shifts Of Reef Coral Taxa In Coastal Western Australia
Benjamin GREENSTEIN* 1 , John PANDOLFI 2
1 Geology, Cornell College, Mount Vernon, IA, 2 Centre for Marine Studies and
Department of Earth Sciences, University of Queensland, Brisbane, Australia
One of the most critical challenges facing ecologists today is to understand the changing
geographic distribution of species in response to current and predicted global warming.
Coastal Western Australia is a natural laboratory in which to assess the effect of climate
change on reef coral communities over a temporal scale unavailable to studies conducted
solely on modern communities. Reef corals composing Late Pleistocene reef assemblages
exposed at five localities along the west Australian coast were censused and the results
compared to coral occurrence data published for the modern reefs offshore of each
locality. The resulting comparative data set comprises modern and Late Pleistocene reef
coral communities occurring over approximately 12 o of latitude. This gradient includes
the zone of overlap between the modern Dampierian and Flindersian Provinces.
Modern reef coral communities show a pronounced gradient in coral composition over
the latitudinal range encompassed by the study, while the gradient in community
composition is not as strong for Pleistocene communities. Tropical-adapted taxa
contracted their ranges north since Late Pleistocene time, emplacing two biogeographic
provinces in a region in which a single province had existed previously.
Beta diversity values for adjacent communities also reflect this change. Modern reefs
show a distinct peak in beta diversity in the middle of the region; the peak is not matched
by Pleistocene reefs. Beta diversity is correlated with distance only for comparisons
between modern reefs in the north and the fossil assemblages, further supporting change
in distribution of the biogeographic provinces in the study area. Coral taxa present in
modern communities clearly expanded and contracted their geographic ranges in
response to climate change. Those taxa that distinguish Pleistocene from modern reefs
are predicted to migrate south in response to future climate change, and potentially persist
in “temperature refugia” as tropical reef communities farther north decline.
2-10
Ecological Dynamics Of Pleistocene Reefs During Sea-Level Lowstand
John PANDOLFI* 1 , Danika TAGER 2 , Jody WEBSTER 3 , Don POTTS 4 , Willem
RENEMA 5 , Juan-Carlos BRAGA 6
1 Cente for Marine Studies and School of Physical Sciences, University of Queensland, St.
Lucia, Australia, 2 Centre for Marine Studies, University of Queensland, St. Lucia,
Australia, 3 School of Earth and Environmental Sciences, James Cook University,
Townsville, Australia, 4 Earth & Marine Sciences, University of California, Santa Cruz,
Santa Cruz, CA, 5 Nationaal Natuur Historisch Museum, Leiden, Netherlands,
6 Estratigrafia y Paleontologia, Universidad de Granada, Granada, Spain
Reef ecosystems built during sea level rise have shown remarkable persistence in coral
community structure but little is known of the ecological characteristics of reef
communities during periods of low sea stands or sea level falls. We sampled the relative
species abundance of coral, coralline algae and foraminifera communities from eight
submerged carbonate reefs in the Huon Gulf, Papua New Guinea, that formed during sea
level fall and lowstand over the past ~416 ky. We found that dissimilarity in coral species
composition increased significantly with time on these reefs. However, neither coral
diversity nor the taxonomic composition of foraminifera and coralline algae assemblages
vary significantly over time. The taxonomic composition of coral communities from
lowstand reefs was significantly different from that of highstand reefs previously reported
from the nearby Huon Peninsula. We interpret the community composition and temporal
dynamics of lowstand reefs as a result of shifting energy regimes in the Huon Gulf, and
differences among low and highstand reefs as a result of variation between the Huon Gulf
and Huon Peninsula environments. Regardless of these trends our study represents the
first glimpse into the ecological dynamics of coral reefs during low sea level stands when
habitable reef area was much less than present day. One major issue associated with
present climate change is a possible order of magnitude reduction in coral reef habitat as
low latitude reefs succumb to mortality events associated with temperature-induced
bleaching events. Reduced areal extent of Pleistocene coral reefs during sea level
lowstand may provide an analogue for such a future scenario.
2-11
Spatial and Temporal Variations in Pleistocene Coral Assemblages in the South and
Central Ryukyu Islands
Marc HUMBLET* 1 , Yasufumi IRYU 1
1 Institute of Geology and Paleontology, Tohoku University, Sendai, Japan
In order to study spatial and temporal variations in Pleistocene coral assemblages in the South
and Central Ryukyus, taxonomic composition and morphology of corals were investigated
using the quadrat method in Irabu-jima (South Ryukyus), Okinawa-jima (southern Central
Ryukyus), and Kikai-jima (northern Central Ryukyus). Cluster analysis was conducted to
identify groups of taxa which tend to co-occur (coral associations) and groups of quadrats with
similar taxonomic compositions. We recorded 40 genera and 84 species in Irabu-jima, 35
genera and 72 species in Okinawa-jima, 33 genera and 65 species in Kikai-jima. The cluster
analysis produced 4 coral associations in Irabu-jima, 6 in Okinawa-jima and 4 in Kikai-jima.
Some of these associations contain taxa indicating a specific depth range, while others,
composed exclusively of cosmopolitan taxa, do not point to any particular reef zone. The
analysis of taxonomic similarities among quadrats resulted in the segregation of 2 groups of
quadrats in Irabu-jima, 5 in Okinawa-jima and 4 in Kikai-jima. In the cluster diagrams, the
segregation of coral assemblages indicative of a same reef zone into distinctive groups or single
branches reflects within-reef-zone variability. Upper reef-slope assemblages display a high
spatial variability in taxonomic and morphological compositions over several meters to several
kilometers. Conversely, middle to lower reef-slope assemblages display a low variability in
taxonomic and morphological composition over meters to tens of meters. Temporal changes in
Pleistocene coral assemblages within several-meter-thick sections of coral limestone reflect
various types of coral successions. Transitions from one reef zone to another are likely due to
sea-level fluctuations. Small-scale abiotic and/or biotic disturbances may result in successions
of distinctive coral assemblages with overlapping depth ranges reflecting within-reef-zone
variability.
2-12
Reef Building At High Latitudes (34° N, Japan)
Hiroya YAMANO* 1 , Kaoru SUGIHARA 2 , Tsuyoshi WATANABE 3 , Michiyo
SHIMAMURA 4 , Kiseong HYEONG 4
1 Center for Global Environmental Research, National Institute for Environmental Studies,
Tsukuba, Japan, 2 Fukuoka University, Fukuoka, Japan, 3 Hokkaido University, Sapporo, Japan,
4 Korea Ocean Research & Development Institute, Ansan, Korea, Republic of
At Iki Island, Japan (33° 48' N), the world's highest-latitude coral-reef formation has been
observed (Yamano et al., 2001, Coral Reefs, 20, 9-12). Following the discovery at Iki Island,
we set up an international project funded by JSPS and KOSEF under the Japan-Korea Basic
Scientific Cooperation Program in order to examine high-latitude corals around Japan and
Korea. In the project, another reef-like mound structure over 5-m thickness was found at
Tsushima Island, ca. 40 km north of Iki Island. We took two cores from the structure, which
indicated that the inside of the mound was dominated by corals and mud. Similar as the coral
reef at Iki Island, faviid corals, also dominant in modern coral community at Tsushima Island,
were observed most frequently and abundantly throughout the cores. These characteristics are
significantly different from those at tropical reefs that are dominated by acroporid corals. It is
the highest latitude reef-like mound structure formed over a few thousands of years. We
describe the distribution, timing of the formation and the growth rate of the mound in
combination with those of the coral reef at Iki Island. We also discuss the significance of reef
building at high latitudes in terms of geological reef evolution.
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