ArticlePDF Available

Abstract and Figures

Staghorn coral (Acropora cervicornis) and elkhorn coral (Acropora palmata), are important reef builders in the Caribbean. In the early to middle Holocene (10000-6000 years ago), when sea temperatures were warmer than today, Acropora-dominated reefs were common along the east coast of Florida as far north as Palm Beach County. The fossil record shows that the northern limits of these two cold-sensitive species subsequently contracted to Biscayne Bay, south of Miami, apparently as a result of climatic cooling. This response of the Acropora species to climate provides a context for interpreting recent shifts in their geographic distribution. Despite recent disease-induced mass mortalities throughout the Caribbean and western Atlantic, the two species are now re-expanding their ranges northward along the Florida Peninsula and into the northern Gulf of Mexico, coincident with increasing sea temperatures. In the face of continued global warming, the northernmost limit of this range expansion will ultimately be determined by a combination of temperature and other physical constraints.
Content may be subject to copyright.
Natural populations face impending changes in the
global climate to which they will have to acclimate or
adapt, or else perish. Their responses to climate change will
have widespread species-level and community-level conse-
quences, and a number of ecologists have predicted changes
in the composition and distribution of future ecosystems
(Fields et al. 1993). The fingerprint of global climate change
can be mapped via the response of species to changes in their
physiographic environmental settings. Hundreds of species
have responded to recent warming trends by expanding
their ranges to higher latitudes, as well as by changing the
timing and duration of their flowering, breeding, migration,
and other climate-related behaviors (Parmesan and Yohe
2003; Root et al. 2003).
Most predictions about the effects of global climate
change on coral reefs have been confined to temperature-
induced coral bleaching (Hoegh-Guldberg 1999; Walther
et al. 2002), rising sea levels (Graus and Macintyre 1998),
and changing ocean chemistry (Kleypas et al. 2001).
Recent reports establish the first example of range expan-
sion of a Caribbean coral genus towards the Poles, in
response to climatic warming. First, spatially extensive
thickets of the staghorn coral, Acropora cervicornis (Figure
1), were discovered off Fort Lauderdale in Broward
County, Florida in 1998 (Vargas-Ángel et al. 2004), where
they had not been observed during the 1970s and 1980s.
More recently, colonies of the elkhorn coral, Acropora
palmata, have been observed as far north as Pompano
Beach in northern Broward County (Precht pers obs;
Figure 2). Also, elkhorn coral was seen for the first time in
2002 on reefs of the Flower Garden Banks in the northern
Gulf of Mexico (S Bernhardt pers comm). The sudden
appearance of Caribbean acroporid corals well north of
their previously known extant range is associated with
decadal-scale increases in annual sea-surface temperature
(SST) in the western Atlantic (Hoegh-Guldberg 1999;
Levitus et al. 2000; Barnett et al. 2001).
Although one cannot prove directly that the recent
expansion of acroporid corals is related to the impacts of
climate change, fossil reefs in Florida provide an opportu-
nity to examine the response of coral reefs to past global
change, especially rapid changes in SST. Well-developed
fossil Holocene reefs situated at the latitudinal extremes of
reef development are juxtaposed with depauperate (low-
diversity) living coral assemblages. The fossil reefs provide
a baseline for understanding the response of reef systems
to fluctuating climates, as well as for predicting the future
response of coral reefs to global change.
307
© The Ecological Society of America www.frontiersinecology.org
REVIEWS REVIEWS REVIEWS
Climate flickers and range shifts of reef
corals
William F Precht1and Richard B Aronson2
Staghorn coral (Acropora cervicornis) and elkhorn coral (Acropora palmata), are important reef builders in
the Caribbean. In the early to middle Holocene (10 000–6000 years ago), when sea temperatures were
warmer than today, Acropora-dominated reefs were common along the east coast of Florida as far north as
Palm Beach County. The fossil record shows that the northern limits of these two cold-sensitive species
subsequently contracted to Biscayne Bay, south of Miami, apparently as a result of climatic cooling. This
response of the Acropora species to climate provides a context for interpreting recent shifts in their geo-
graphic distribution. Despite recent disease-induced mass mortalities throughout the Caribbean and west-
ern Atlantic, the two species are now re-expanding their ranges northward along the Florida Peninsula and
into the northern Gulf of Mexico, coincident with increasing sea temperatures. In the face of continued
global warming, the northernmost limit of this range expansion will ultimately be determined by a com-
bination of temperature and other physical constraints.
Front Ecol Environ 2004; 2(6): 307–314
1Ecological Sciences Program, PBS&J, 2001 NW 107th Avenue,
Miami, FL 33172 (bprecht@pbsj.com); 2Dauphin Island Sea Lab,
101 Bienville Boulevard, Dauphin Island, AL 36528
In a nutshell:
The ranges of staghorn and elkhorn corals were more expan-
sive during the early to middle Holocene, when sea tempera-
tures in the western Atlantic were warmer than they are at pre-
sent
These two coral species are currently expanding their geo-
graphic ranges northward along the Florida Peninsula and into
the northern Gulf of Mexico
The range expansion appears to be related to warming sea tem-
peratures
The continued northward expansion of the geographic ranges
of coral species should not be accompanied by temperature-
induced extinction at lower latitudes
On the other hand, geographic shifts will not mitigate
expected ecological and economic losses resulting from the
reduced functions of tropical reef systems
Global change and coral reefs WF Precht and RB Aronson
One of the most startling aspects of the recent discovery
of flourishing northern populations of Acropora is related
to the overall poor condition of Caribbean reefs. Gardner
et al. (2003) used meta-analysis to assess the extent of
coral decline across the Caribbean since the 1970s. Their
study revealed that reefs from all sectors of the region were
badly affected. Disturbances of various kinds have been
invoked to explain the changing face of Caribbean reefs
over the past 25 years, and coral mortality, especially the
mortality of Acropora spp, has been a major driving force
in the transition (Aronson and Precht 2001). Many fac-
tors have been responsible for Acropora mortality, but
white-band disease, temperature stress, predation, and
hurricanes have all played key roles in reducing popula-
tions both locally and regionally. The
acroporids are among the most impor-
tant reef builders in the Caribbean, so
their loss has been a major reason that
Caribbean reefs have declined. In the
face of this massive mortality, the
recent range expansion of Acropora was
unexpected.
Effects of temperature
Reef-building hard corals (order Scler-
actinia) are distributed along a latitudi-
nal diversity gradient, with the highest
species richness in the tropics. The ori-
gin and maintenance of this pattern,
and especially its persistence through
time, are not completely understood,
but temperature has long been consid-
ered the main controlling factor on the
distribution of these species. The opti-
mum temperature for coral growth is
about 26° to 28°C. Low-temperature tolerances are not
well defined for corals, but early experiments documented
16°C as stressful to most species and showed that exposure
to temperatures below 15°C can result in mortality (see
Shinn 1989). The present-day global distribution of coral
reefs generally coincides with the 18°C monthly mini-
mum seawater isotherm (Buddemeier et al. 2004).
Coral reefs in the Florida Keys are at the northern limit
of reef growth in the Americas. Caribbean acroporids are
especially sensitive to cold water, and sustained low tem-
peratures associated with the passage of winter cold fronts
have caused episodic mass mortalities of staghorn and
elkhorn corals in Florida and the Bahamas (Precht and
Miller in press). Rapid diminution of generic diversity
northwards along the east coast of
Florida is due primarily to cold-tempera-
ture limitations (Porter and Tougas
2001). Although the 18°C isotherm is
the approximate boundary for reef
building in the western Atlantic, the
ranges of a number of reef-building
species extend further northwards along
the east coast due to the poleward
transport of warm water, via the Florida
Current (a southern segment of the Gulf
Stream), and to the Flower Garden
Banks in the northern Gulf of Mexico,
due to the influence of the warm Loop
Current. During the recent past, Fowey
Rocks, located southeast of Miami, was
the northern extent of reef growth dom-
inated by acroporids (Shinn et al. 1989;
Figures 3 and 4). Assemblages of scler-
actinians and gorgonians (soft corals)
were found north of Fowey Rocks, off
308
www.frontiersinecology.org © The Ecological Society of America
Figure 1. Underwater photograph showing luxuriant thickets of staghorn coral
(Acropora cervicornis) recently found off Ft Lauderdale, FL. This is approximately
50 km north of the previous known extant range of Caribbean acroporids.
Figure 2. Underwater photograph of the northernmost known colony of elkhorn coral
(Acropora palmata) in the western Atlantic, located off Pompano Beach, FL.
WF Precht and RB Aronson Global change and coral reefs
Broward and Palm Beach Counties, with acroporid corals
generally being rare (staghorn coral) or absent (elkhorn
coral) (Goldberg 1973).
Corals are typically exposed during local summer-
time to temperatures near the upper limits of their
thermal tolerances (Hoegh-Guldberg 1999). Although
elevated water temperatures are clearly detrimental to
corals, the response of reef ecosystems to high temper-
ature is less clear. Unlike cold stress, there is little evi-
dence to suggest that maximum temperature currently
limits the latitudinal distribution of coral reefs
(Kleypas in press). Nevertheless, coral reefs are consid-
ered to be the ecosystems most threatened by global
warming (Hoegh-Guldberg 1999; Kleypas et al. 2001;
Walther et al. 2002).
Field and laboratory studies have shown unequivocally
that sustained, anomalously high summertime water tem-
peratures are associated with bleaching (the expulsion of
zooxanthellae by corals and other symbiotic reef organ-
isms; Figure 5). If temperatures rise above the average
maximum for a prolonged period, bleaching leads to death
in many species (Hoegh-Guldberg 1999). Bleaching is not
always fatal, however, and some episodes have been fol-
lowed by recovery of most of the affected coral colonies
(Fitt et al. 1993).
Coral bleaching in response to anomalously high sum-
mer-season temperatures has become more frequent
since the early 1980s (Hoegh-Guldberg 1999). The
widespread nature of these bleaching events over the
past two decades is correlated with increases in maxi-
mum SST (Kleypas et al. 2001). On a global scale, tem-
perature-induced bleaching is usually correlated with
inter-annual climatic fluctuations, of which the El
Niño–Southern Oscillation (ENSO) is the most impor-
tant. During the ENSO-induced global coral bleaching
of 1998, an estimated 16% of the world’s reef-building
corals died (Walther et al. 2002). These bleaching
episodes are dramatic, but they have not been tied to the
extinction of any reef-building species in the Caribbean
or elsewhere. The projected continuing increase in
bleaching episodes on coral reefs, related to ENSO
events and augmented by global warming, is likely to
decrease coral abundance in the future (Hoegh-
Guldberg 1999; Wellington et al. 2001; Aronson et al.
2002; Hughes et al. 2003; Sheppard 2003).
The catastrophic loss of coral cover on Florida’s reefs
over the past 25 years (Shinn 1989; Precht and Miller in
press) could persist for decades or longer. It is unclear
how future global climate change will interact with dis-
ease (Figure 6) and other stresses (Harvell et al. 1999;
Aronson and Precht 2001; Kleypas et al. 2001;
Knowlton 2001; Hughes et al. 2003), but it is known
that the virulence of some coral diseases increases with
rising temperature (Rosenberg and Ben-Haim 2002).
We are faced with two essential questions related to
global temperatures: (1) will the latitudinal ranges of
coral species and coral reefs expand toward the Poles?;
and (2) will corals and coral reefs be eliminated from
low-latitude tropical regions?
309
© The Ecological Society of America www.frontiersinecology.org
Figure 3. Map of Florida showing the present-day distribution
of the reef tract and the northern limit of acroporid corals
(green), the relict Holocene reef tract dominated by acroporid
corals (orange), and the location of recently discovered thickets
of acroporid corals (star).
Figure 4. Patterns of generic diversity of scleractinian corals in
the Caribbean. Rapid faunal diminution along the east coast of
Florida is due to cold temperature limitations. The area in yellow
represents the known distribution of Caribbean acroporids.
Modified from Porter and Tougas (2001).
Global change and coral reefs WF Precht and RB Aronson
The present
Recent studies of marine and coastal systems at middle
and high latitudes have suggested biogeographical shifts,
with increased numbers of warm-water species and
decreased numbers of cold-water species (Weinberg et al.
2002). Few studies have documented such changes in the
tropics, and we know very little about the response of the
extant biota at lower latitudes in the marine realm.
Predicted increases in tropical temperatures (Buddemeier
et al. 2004) will probably have dramatic effects on the
structure and function of these ecosystems and their ser-
vices (Walther et al. 2002), including the introduction,
spread, and dominance of exotic species, and the possible
extinction of native species (McLaughlin et al. 2002;
Stachowicz et al. 2002).
There is mounting evidence that coral species are
responding to recent patterns of increased SSTs by
expanding their latitudinal ranges. One example is the
recent range expansion in the Caribbean and Gulf of
Mexico of Tubastrea coccinea, the first Indo–Pacific coral
species known to have been introduced to the western
Atlantic (Fenner 2001). In Florida, numerous thickets of
staghorn coral, some up to 700 m2in area, are now estab-
lished north of their previously known range. Detailed
studies documenting the composition, structure, and
reproductive viability of these populations have been con-
ducted in seven of these thickets (Vargas-Ángel et al.
2004). Elkhorn coral has also been observed colonizing
shallow reef areas north of extant populations. The two
Acropora species have expanded more than 50 km north-
ward in just the last few decades.
Many factors could be causing the
recent change in distribution of acro-
porid corals, including competition
with macroalgae, changes in habitat
quality, short-term population vari-
ability, indirect interspecific interac-
tions, and variations in reproductive
and recruitment success. Abiotic
parameters influencing their distrib-
ution could include changes in tur-
bidity and water quality, the magni-
tude and frequency of ENSO events,
variations in local and regional
hydro-meteorological forcing pat-
terns, changes in the direction and
intensity of the northward-flowing
Florida Current, and changing pat-
terns in the frequency and duration
of upwelling. Although it is likely
that many of these processes are
occurring and interacting with one
another, the most obvious explana-
tion for the recent range expansion
of acroporids is climatic warming.
We draw this inference based on the
following observations:
(1) The geographic distribution of reef-building corals
along the east coast of Florida is, in general, strongly
correlated with temperature
(2) Acropora spp are temperature-sensitive, and episodes
of mass mortality in Florida have been linked to cold-
water outbreaks
(3) The recent range expansion of the acroporids coin-
cides with a known period of climatic warming and
measured increases in SSTs
(4) The range expansion coincides with a period of ther-
mal stress (bleaching) of reef-building corals world-
wide
(5) The range expansion in Florida coincides with the
discovery of elkhorn coral at the Flower Garden
Banks in the northern Gulf of Mexico
(6) The range expansion coincides with similar range
shifts in Indo-Pacific coral species
(7) The present-day range expansion of western Atlantic
acroporids resembles a change in the geographic distri-
bution of acroporid-dominated reef systems during a
millennial-scale climate flicker thousands of years ago.
The past
Florida’s biogeographic precedent for today’s range
expansion correlates with a period of global warming ear-
lier in the Holocene epoch. This historical example
(Lighty et al. 1978) can be used as an analogue to model
the future response of the Florida reef tract to high-ampli-
tude climate flickers and global warming, even though
310
www.frontiersinecology.org © The Ecological Society of America
Figure 5. Colony of completely bleached elkhorn coral during a severe coral bleaching
event in 1998. Global coral bleaching episodes have been linked to elevated sea surface
temperatures. Photo taken at Looe Key, FL, in August 1998.
WF Precht and RB Aronson Global change and coral reefs
the climatic mechanisms producing the
earlier warm period were different from
those operating at present. SSTs in the
subtropical western Atlantic increased
from 14 000 years before present (ybp)
to the beginning of the Holocene,
about 10 000 ybp; these were higher
than today’s SSTs during the early to
middle Holocene, 10 000 to 6000 ybp;
and declined to modern values in the
late Holocene, 6000 ybp to present
(Balsam 1981; Ruddiman and Mix
1991). This millennial-scale tempera-
ture pattern was probably caused by a
reorganization of North Atlantic circu-
lation similar to Dansgaard-Oeschger
cycles (Kerr 1996). Through the
Quaternary, Dansgaard-Oeschger cycles
have occurred every few thousand years
and have been characterized by abrupt
jumps in temperature.
Relict, submerged, early to middle Holocene reefs are
found throughout southeast Florida (Toscano and
Macintyre 2003; Figure 7). Warmer conditions during this
period apparently permitted a more northerly distribution
of acroporid-dominated reefs (Figure 3). As temperatures
cooled after the middle Holocene, the northern limit of
the Florida reef tract moved south to its current position.
In the early to middle Holocene, Acropora-dominated
reefs up to 10 m thick were well developed as far north as
Palm Beach County (Lighty et al. 1978), indicating that
conditions along the platform margin were more con-
ducive than today to the growth of acroporid corals and
the deposition of acroporid-dominated
reef framework (Figure 8). We inter-
pret the more northerly distribution of
Acropora as a reflection of northward
excursions of warm water related to a
unique conjunction of factors. First,
lower sea levels during this time placed
the active shelf-margin reef system in
closer proximity to the warmer waters
of the Florida Current. Second, the
period from about 9000–5000 ybp
corresponds to the warmest interval of
the Holocene, the Mid-Holocene
Warm (Kerwin et al. 1999) or
Altithermal (Buddemeier et al. 2004).
Although tropical temperatures
remained relatively stable through the
middle Holocene, within 1.0–1.5°C of
present values (Arz et al. 2001), paleo-
temperatures reconstructed from the
extratropical North Atlantic indicate
SSTs 2–3°C warmer than at present
(Balsam 1981; Ruddiman and Mix
1991). Climate simulations suggest
that North Atlantic SSTs at 6000 ybp were as much as
4°C warmer than today (Kerwin et al. 1999). Evidence
from both terrestrial and coastal habitats shows that
warming during this millennial-scale, high-amplitude cli-
mate flicker caused many species from a variety of ecosys-
tems to expand their ranges northwards (COHMAP
1988; Delcourt and Delcourt 1991; Dahlgren et al. 2000).
The climate flicker during the middle Holocene also
correlates with maximal coral diversity at the northern-
most position of coral reefs in the Pacific. The world’s
highest latitude Pacific coral reef is currently in Tateyama,
Japan (33.5°N). Veron’s (1992) study of a mid-Holocene
311
© The Ecological Society of America www.frontiersinecology.org
Figure 7. Idealized cross-section showing three shore-parallel relict reef ridges off
Broward County, FL. The lower ridge was described by Lighty et al. (1978) at
Hillsborough Inlet and the middle ridge by Precht et al. (2000) at Dania Beach.
Radiocarbon dates of recovered elkhorn coral revealed substantial early- to middle-
Holocene reef development off the east coast of Florida, extending north to Palm Beach
County. Figure modified from originals in Lighty et al. (1978) and Toscano and
Macintyre (2003).
Figure 6. White-band disease and resultant “branch-to-tip” mortality pattern
observed on a colony of elkhorn coral at Carysfort Reef, FL. Photo taken in 1999.
Global change and coral reefs WF Precht and RB Aronson
fossil reef at Tateyama showed that even a brief period of
warming of only 2°C doubled species richness from 35 to
72 species at the latitudinal extreme of extant corals. At
the southernmost living reef in the Pacific Ocean, Lord
Howe Island in Australia (31.3°S), evidence indicates
that reefs were better developed in the early to middle
Holocene than today, suggesting similar responses of
corals to fluctuating SSTs.
Another paleoecological example is found in the
Pleistocene reef community at Rottnest Island off
Western Australia (32°S). The living reef at this locality
has some 25 species of zooxanthellate corals. Most are at
the southern limit of their range, with Acropora spp being
rare (Marsh 1992); however, during the last major inter-
glacial (about 125 000 ybp), when the water was a few
degrees warmer, major reefs were formed by both staghorn
and tabular Acropora spp (Szabo 1979). These paleoeco-
logical examples of species replacements and range expan-
sions, especially those concerning acroporids, emphasize
the varied responses of coral species and their ability to
reconstitute reef communities in the face of rapid environ-
mental change not related to human modification of the
seascape. Understanding the response of reef organisms to
warm climates of the past, regardless of the underlying
causes, will help us predict the future of coral reefs in a
warming world.
The future
The modeled range of global temperature increase is
1.4–5.8°C for the period 1990–2100 (Buddemeier et al.
2004). However, these models predict an SST warming of
only 1–3°C in the tropics during the same period.
Relative conservatism of tropical temperatures and
greater warming of extratropical areas are likely to result
from feedbacks in the ocean–atmos-
phere system, which prevents SSTs
from exceeding 32°C (Kleypas in
press). General circulation models
indicate that tropical heating, espe-
cially near the equator, increases latent
heat flux away from the tropics. The
predicted difference in temperature
rise between the tropics and extratrop-
ical areas is remarkably similar to those
recorded through the glacial–inter-
glacial cycles of the Quaternary Period
(the last 1.8 million years; CLIMAP
1984).
The National Research Council
(1988) recommended that studies doc-
umenting population, community, and
ecosystem responses to rapid environ-
mental changes of the Quaternary be
used to provide insight into the rates
and directions of future biotic change.
Specifically, such paleoecologic studies
allow us to evaluate biotic response to environmental
changes of magnitudes that are beyond recent values but
within the range of projected global change. Although
fossil assemblages from a number of ecosystems have no
analogues in modern communities (Roy et al. 1996), mod-
ern reef communities closely resemble fossil reef assem-
blages (Pandolfi and Jackson 1997).
It has been argued that tropical coral assemblages
exhibit stability and persistence through Quaternary time
and therefore constitute the most important database for
studying abrupt change in modern reefs (Pandolfi and
Jackson 1997). A key aspect of this argument is that
warmer temperatures during the last major interglacial
period were not associated with contraction of the south-
ern range of the acroporids or the demise of reef systems in
the tropics. Based on these results, and because SSTs in
global climate models generally do not exceed 32°C in the
Caribbean, it is unlikely that future global warming will
lead to the catastrophic collapse of reef systems, the extir-
pation of acroporid corals, or the contraction of their
southern range in the tropical Caribbean, as some have
predicted (eg Hoegh-Guldberg 1999; Reaser et al. 2000).
Reefs living under non-optimal conditions in more ther-
mally reactive areas, including those in Florida, the Gulf
of Mexico, and Bermuda, are more likely to show changes
in species richness and diversity with climatic warming
(Precht and Miller in press).
At the latitudinal extremes of Caribbean reef systems,
an increase in SST of only 1–2°C should encourage tem-
perature-sensitive corals such as the acroporids to expand
their ranges. Reyes Bonilla and Cruz Piñón (2002) made a
similar prediction for warming seas along the Pacific coast
of Mexico, suggesting that coral species richness will
increase the most at subtropical latitudes. Along the east-
ern Pacific, as many as eight coral species have recently
312
www.frontiersinecology.org © The Ecological Society of America
Figure 8. Underwater photograph of excavated in situ colony of elkhorn coral from a
Holocene-age relict reef off Ft Lauderdale, FL. Colony in photo was radiocarbon-
dated to 6980 calendar years before present.
WF Precht and RB Aronson Global change and coral reefs
been identified north of their previously known ranges
(H Reyes Bonilla pers comm), while at Lord Howe
Island in Australia the arrival of six species has been
observed within the past decade (JEN Veron pers
comm). In addition to temperature, however, other fac-
tors including light, carbonate saturation state, pollu-
tion, and disease influence reef development
(Buddemeier et al. 2004). Increases in extreme weather
and climate events will also probably occur in the
future, especially at middle to high latitudes (Easterling
et al. 2000). Associated habitat loss due to these multi-
ple stressors will further complicate our ability to pro-
ject geographic distributions of species and communi-
ties under future climates (Pyke 2004). We cannot
predict how these controls will interact, meaning that
further climate change could cause the latitudinal
ranges of coral reefs to expand, remain stable, or even
contract (Kleypas in press). Furthermore, the north-
ward expansion of Caribbean reefs will be limited by
the shift from a carbonate-dominated to a siliciclastic-
dominated sedimentary regime, as well as by increasing
nutrient concentrations, as one moves north along the
east coast of the Florida Peninsula, further confounding
future predictions.
The staghorn coral thickets off Fort Lauderdale present
an interesting case. Are these remnant populations, or are
they the recent product of a chance recruitment event?
Do they represent a temporary range expansion that is
likely to be obliterated by the passage of the next sub-
freezing cold front, disease outbreak, or hurricane? Are
they an indicator of global climate change? These possibil-
ities are not mutually exclusive, but only through genetic
analysis of populations and long-term monitoring will we
be able to answer such questions definitively.
The fossil record of coral reefs is helping us predict the
impacts of future climatic warming. Although it is likely
that reef-building corals will expand their ranges to higher
latitudes in response to global warming, geographic shifts
of marginal reefs will not mitigate the expected ecological
and economic losses due to localized coral mortality and
reduced function in tropical reef systems. Understanding
the causal links between climate change and the dynamics
of reefs and other ecosystems will continue to be a chal-
lenge in the face of natural variability, uncertainties inher-
ent in predictive models, and the complex impacts of
human activity all over the planet.
Acknowledgements
We thank Dick Dodge, Peter Glynn, Joanie Kleypas, Ian
Macintyre, Steven Miller, Hector Reyes Bonilla,
Bernhard Riegl, Martha Robbart, James Thomas, Maggie
Toscano, Bernardo Vargas-Ángel, and Charlie Veron for
advice and discussion. Ian Macintyre provided funds for
radiocarbon dating the samples described in Figure 6.
Beta Analytic, Inc. of Miami performed the 14C dating.
Sarah Bernhardt discovered Acropora palmata at the
Flower Garden Banks in the northwestern Gulf of
Mexico. Funding for this work was provided by the US
Department of the Interior’s Minerals Management
Service (contract GM-02-04 to WFP) and the US
National Science Foundation (grant EAR-9902192 to
RBA). This is Contribution No. 355 from the Dauphin
Island Sea Lab.
References
Aronson RB and Precht WF. 2001. White-band disease and the
changing face of Caribbean coral reefs. Hydrobiologia 460:
25–38.
Aronson RB, Precht WF, Toscano MA, and Koltes KH. 2002. The
1998 bleaching event and its aftermath on a coral reef in
Belize. Mar Biol 141: 435–47.
Arz HW, Gerhardt S, Pätzold J, and Röhl U. 2001. Millennial-scale
changes of surface- and deep-water flow in the western tropical
Atlantic linked to Northern Hemisphere high-latitude climate
during the Holocene. Geology 29: 239–42.
Balsam W. 1981. Late Quaternary sedimentation in the western
North Atlantic: stratigraphy and paleoceanography.
Palaeogeogr Palaeoclimatol Palaeoecol 35: 215–40.
Barnett TP, Pierce DW, and Schnur R. 2001. Detection of anthro-
pogenic climate change in the world’s oceans. Science 292:
270–74.
Buddemeier RW, Kleypas JA, and Aronson RB. 2004. Coral reefs
and global climate change: potential contributions of climate
change to stresses on coral reef ecosystems. Arlington,VA: Pew
Center on Global Climate Change.
CLIMAP Project Members. 1984. The last interglacial ocean. Quat
Res 21: 123–224.
COHMAP Members. 1988. Climatic changes of the last 18,000
years: observations and model simulations. Science 241:
1043–52.
Dahlgren TG, Weinberg JR, and Halanych KM. 2000.
Phylogeography of the ocean quahog (Artica islandica): influ-
ences of paleoclimate on genetic diversity and species range.
Mar Biol 137: 487–95.
Delcourt HR and Delcourt PA. 1991. Quaternary ecology – a pale-
oecological perspective. London, UK: Chapman and Hall.
Easterling DR, Meehl GA, Parmesan C, et al. 2000. Climate
extremes: observations, modeling, and impacts. Science 289:
2068–74.
Fenner D. 2001. Biogeography of three Caribbean corals
(Scleractinia) and the invasion of Tubastraea coccinea into the
Gulf of Mexico. Bull Mar Sci 69: 1175–89.
Fields PA, Graham JB, Rosenblatt RH, and Somero GN. 1993.
Effects of expected global climate change on marine faunas.
Trends Ecol Evol 8: 361–67
Fitt WK, Spero HJ, Halas J, et al. 1993. Recovery of the coral
Montastrea annularis in the Florida Keys after the 1987
Caribbean “bleaching event”. Coral Reefs 12: 57–64.
Gardner TA, Côté IM, Gill JA, et al. 2003. Long-term region-wide
declines in Caribbean corals. Science 301: 958–60.
Goldberg WM. 1973. The ecology of the coral–octocoral commu-
nities off the southeast Florida coast: geomorphology, species
composition, and zonation. Bull Mar Sci 23: 465–87.
Graus RR and Macintyre IG. 1998. Global warming and the future
of Caribbean coral reefs. Carb Evap 13: 43–47.
Harvell CD, Kim K, Burkholder JM, et al. 1999. Emerging marine
diseases – climate links and anthropogenic factors. Science 285:
1505–10.
Hoegh-Guldberg O. 1999. Climate change, coral bleaching and
the future of the world’s coral reefs. Mar Freshwat Res 50:
839–66.
Hughes TP, Baird AH, Bellwood DR, et al. 2003. Climate change,
313
© The Ecological Society of America www.frontiersinecology.org
Global change and coral reefs WF Precht and RB Aronson
human impacts, and the resilience of coral reefs. Science 301:
929–33.
Kerr RA. 1996. Millennial climate oscillation spied. Science 271:
146–47.
Kerwin M, Overpeck JT, Webb RS, et al. 1999. The role of oceanic
forcing in mid-Holocene Northern Hemisphere climatic
change. Paleoceanography 14: 200–10.
Kleypas JA. Constraints on predicting coral reef response to cli-
mate change. In: Aronson RB (Ed). Geological approaches to
coral reef ecology. New York: Springer-Verlag. In press.
Kleypas JA, Buddemeier RW, and Gattuso J-P. 2001. The future of
coral reefs in an age of global change. Geol Rundsch 90:
426–37.
Knowlton N. 2001. The future of coral reefs. Proc Natl Acad Sci
USA 98: 5419–25.
Levitus S, Antonov JI, Boyer TP, and Stephens C. 2000. Warming
of the world ocean. Science 287: 2225–28.
Lighty RG, Macintyre IG, and Stuckenrath R. 1978. Submerged
early Holocene barrier reef south-east Florida shelf. Nature
276: 59–60.
Marsh LM. 1992. The occurrence and growth of Acropora in extra-
tropical waters off Perth, Western Australia. Guam: Proc 7th
Intl Coral Reef Symp 2: 1233–38.
McLaughlin JF, Hellmann JJ, Boggs CL, and Ehrlich PR. 2002.
Climate change hastens population extinctions. Proc Natl Acad
Sci USA 99: 6070–74.
National Research Council. 1988. Toward an understanding of
global change. Washington, DC: National Academy Press.
Pandolfi JM and Jackson JBC. 1997. The maintenance of diversity
on coral reefs: examples from the fossil record. Panama: Proc
8th Intl Coral Reef Symp 1: 397–404.
Parmesan C and Yohe G. 2003. A globally coherent fingerprint of
climate change impacts across natural systems. Nature 421:
37–42.
Porter JW and Tougas JI. 2001. Reef ecosystems: threats to their
biodiversity. In: Encyclopedia of biodiversity. New York:
Academic Press 5: 73–95.
Precht WF, Macintyre IG, Dodge RE, et al. 2000. Backstepping of
Holocene reefs along Florida’s east coast. Bali: Abstracts 9th Intl
Coral Reef Symp. p 321.
Precht WF and Miller SL. Ecological shifts along the Florida reef
tract: the past as a key to the future. In: Aronson RB (Ed).
Geological approaches to coral reef ecology. New York:
Springer-Verlag. In press.
Pyke CR. 2004. Habitat loss confounds climate change impacts.
Front Ecol Environ 2: 178–82.
Reaser JK, Pomerance R, and Thomas PO. 2000. Coral bleaching
and global climate change: scientific findings and policy rec-
ommendations. Conserv Biol 14: 1500–11.
Reyes Bonilla H and Cruz Piñón G. 2002. Influence of temperature
and nutrients on species richness of deep-water corals from the
western coast of the Americas. Hydrobiologia 471: 35–41.
Root TL, Price JT, Hall KR, et al. 2003. Fingerprints of global
warming on wild animals and plants. Nature 421: 57–60.
Rosenberg E and Ben-Haim Y. 2002. Microbial diseases of corals
and global warming. Env Microbiol 4: 318–26.
Roy K, Valentine JW, Jablonski D, and Kidwell SM. 1996. Scales of
climatic variability and time averaging in Pleistocene biotas:
implications for ecology and evolution. Trends Ecol Evol 11:
458–63.
Ruddiman WF and Mix AC. 1991. The north and equatorial
Atlantic at 9000 and 6000 yr B.P. In: HE Wright Jr, JE
Kutzbach, T Webb III, et al. (Eds). Global climates since the
last glacial maximum. Minneapolis: University of Minnesota
Press. p 94–124.
Sheppard CRC. 2003. Predicted recurrences of mass coral mortal-
ity in the Indian Ocean. Nature 425: 294–97.
Shinn EA. 1989. What is really killing the corals? Sea Frontiers 35:
72–81.
Shinn EA, Lidz BH, Kindinger JL, Hudson JH, and Halley RB.
1989. Reefs of Florida and the Dry Tortugas. Field Trip
Guidebook T176. Washington, DC: American Geophysical
Union.
Stachowicz JL, Terwin JR, Whitlatch RB, and Osman RW. 2002.
Linking climate change and biological invasions: ocean warm-
ing facilitates nonindigenous species invasions. Proc Natl Acad
Sci USA 99: 15497–500.
Szabo BJ. 1979. Uranium-series age of coral reef growth on
Rottnest Island, Western Australia. Mar Geol 29: M11–M15.
Toscano MA and Macintyre IG. 2003. Corrected western Atlantic
sea-level curve for the last 11,000 years based on calibrated 14C
dates from Acropora palmata and mangrove intertidal peat.
Coral Reefs 22: 257–70.
Vargas-Ángel B, Thomas JD, and Hoke SM. 2003. High-latitude
Acropora cervicornis thickets off Fort Lauderdale, Florida, USA.
Coral Reefs 22: 465–74.
Veron JEN. 1992. Environmental control of Holocene changes to
the world’s most northern hermatypic coral outcrop. Pac Sci 46:
405–25.
Walther G-R, Post E, Convey P, et al. 2002. Ecological responses to
recent climate change. Nature 416: 389–95.
Weinberg JR, Dahlgren TG, and Halanych KM. 2002. Influence of
rising sea temperature on commercial bivalve species of the U.
S. Atlantic coast. Amer Fish Soc Symp 32: 131–40.
Wellington GM, Glynn PW, Strong AE, et al. 2001. Crisis on coral
reefs linked to climate change. Eos 82: 1,5.
314
www.frontiersinecology.org © The Ecological Society of America
... In the western Atlantic, threatened Acropora spp. have also been observed well north of their historical ranges off southeast Florida 16,17 and at the Flower Garden Banks in the northern Gulf of Mexico 18 . These observations suggest that subtropical regions may provide critical 'refuges' for tropical reef-building coral assemblages in the face of ongoing climate warming [18][19][20] . ...
... They also provide a valuable pre-anthropogenic baseline that can be used to evaluate the state and longterm stability of modern coral reef ecosystems, allowing resource managers to prioritize specific areas for restoration and protection 7,10,21 . This application is especially useful in determining the potential of higher latitude reef sites to serve as climate refuges, particularly where analogous range expansions occurred in the geological past 15,17,23,32 . Reconstructions of past coral range expansions from the fossil record not only inform where future expansions might occur, but also provide the necessary framework for determining whether recent range expansions are likely to persist in subtropical or temperate regions threatened by climate and environmental change. ...
... Paleoecological records of subtropical reef development in southeast Florida are crucial for evaluating the present and future biogeographical response of coral populations to climate change 5,17 . However, previous studies of Holocene reef development in the region have focused primarily on A. palmata 23,37-39 , thereby limiting our understanding of broader coral community dynamics. ...
Article
Full-text available
As thermal stress and disease outbreaks decimate coral reefs throughout the tropics, there is growing evidence that higher latitude marine environments may provide crucial refuges for many at-risk, temperature-sensitive coral species. However, our understanding of how coral populations expand into new areas and sustain themselves over time is constrained by the limited scope of modern observations. Here, we provide geological insights into coral range expansions by reconstructing the composition of a Late Holocene-aged subfossil coral death assemblage on the southeast Florida reef tract and comparing it to modern reefs throughout the region. Our findings show that the Late Holocene coral assemblages were dominated by now critically endangered Acropora species between ~3500 and 1800 years before present, mirroring classic zonation patterns characteristic of healthy pre-1970s Caribbean reefs. In contrast, the modern reefs off southeast Florida are becoming increasingly dominated by stress-tolerant species like Porites astreoides and Siderastrea siderea despite modest expansions of Acropora cervicornis over the past several decades. Our results suggest that ongoing anthropogenic stressors, not present during the Late Holocene, are likely limiting the ability of modern higher latitude reefs in Florida to function as long-term climate refugia.
... Other middle-and high-latitude studies have shown similar patterns of increased numbers of warm-water species and decreased numbers of cold-water species [94][95][96] . With the frequency of warm winters increasing, the possibility grows for typically tropical populations of certain reef fish species to become established in subtropical locations year-round 97 . ...
... The outcomes of this study provide a statistically derived spatially defined baseline of reef fish assemblages for evaluating the effects of future demographic and structural changes. Tropical species' poleward range expansion along the nFRT have occurred in the historical past 61 and have been suggested for contemporary corals 96 , but thus far, contemporary range expansions for fish or corals have not been documented. If warm sea surface temperatures move northward as predicted, opportunities will increase for tropical species to survive in historically subtropical locales, and a poleward shift in the center of biomass of tropical species could occur 21,94,95,111 . ...
Article
Full-text available
The Anthropocene rise in global temperatures is facilitating the expansion of tropical species into historically non-native subtropical locales, including coral reef fish. This redistribution of species, known as tropicalization, has serious consequences for economic development, livelihoods, food security, human health, and culture. Measuring the tropicalization of subtropical reef fish assemblages is difficult due to expansive species ranges, temporal distribution shifts with the movement of isotherms, and many dynamic density-dependent factors affecting occurrence and density. Therefore, in locales where tropical and subtropical species co-occur, detecting tropicalization changes relies on regional analyses of the relative densities and occurrence of species. This study provides a baseline for monitoring reef fish tropicalization by utilizing extensive monitoring data from a pivotal location in southeast Florida along a known transition between tropical and subtropical ecotones to define regional reef fish assemblages and use benthic habitat maps to spatially represent their zoogeography. Assemblages varied significantly by ecoregion, habitat depth, habitat type, and topographic relief. Generally, the southern assemblages had higher occurrences and densities of tropical species, whereas the northern assemblages had a higher occurrence and density of subtropical species. A total of 108 species were exclusive to regions south of the Bahamas Fracture Zone (BFZ) (South Palm Beach, Deerfield, Broward-Miami) and 35 were exclusive to the north (North Palm Beach, Martin), supporting the BFZ as a pivotal location that affects the coastal biogeographic extent of tropical marine species in eastern North America. Future tropicalization of reef fish assemblages are expected to be evident in temporal deviance of percent occurrence and/or relative species densities between baseline assemblages, where the poleward expansion of tropical species is expected to show the homogenization of assemblage regions as adjacent regions become more similar or the regional boundaries expand poleward. Ecoregions, habitat depth, habitat type, and relief should be incorporated into the stratification and analyses of reef fish surveys to statistically determine assemblage differences across the seascape, including those from tropicalization.
... Globally, coral reefs provide livelihoods for over one billion people, with this number increasing as the global population grows (Cinner 2014). Global warming and habitat degradation can, however, induce multi-species shifts across communities (Feary et al. 2014), reorganising reef community compositions (Kumagai et al. 2018;Precht and Aronson 2004;Vergés et al. 2019), and potentially their functions (Perry and Álvarez-Filip 2018; Vergés et al. 2014). Community reorganisation and species shifts can result in species extinctions and further community degradation (Agostini et al. 2021;Beger et al. 2014). ...
Article
Full-text available
Global warming causes functional shifts and reorganisation in marine communities through range shifts to high-latitude reefs and cnidarian bleaching mortality in the tropics. Such changes threaten the integrity and structure of marine communities, especially as foundational and associated species are reduced or lost. However, comparatively little is known about the extent of range shifts and their ecological consequences for the overlooked components of marine ecosystems, such as octocorals and zoantharians (O + Z) on shallow coral reefs. As these groups play a crucial part in building complexity and sustaining life in reef communities, functional shifts in these taxa may cascade through the entire ecosystem, but these processes have not been quantified. Here, we examined the environmental drivers and functional consequences of spatial variation in octocoral and zoantharian communities across 27 sites in southern Japan, spanning from tropical to warm-temperate waters. We collated a trait database for 42 entities (species, genus, and family level identifications) of octocorals and zoantharians and calculated functional diversity and functional richness to measure functional compositional change. We identified five functional groups according to their trait similarities and identified how their abundances respond to changing environmental factors with general additive models (GAMs). We found functional shifts among octocorals and zoantharians across the tropical to temperate thermal gradient, with the abundances of two functional groups best explained by gradients in minimum sea surface temperature. Non-linear relationships between the functional groups and thermal gradients imply a more intricate relationship than expected, suggesting other non-temperature-based drivers, e.g., nitrogen or pH levels might also play an important role. Only functional group richness and species richness showed significant correlations with latitude, whilst functional diversity and functional richness did not. Our results indicate that octocoral and zoantharian communities and functionality potentially undergo shifts with clear community compositional changes, influenced by climate change across environmental gradients. However, the taxonomy and identification of these taxa remain difficult, and information on functional traits is often sparse or not species-specific, indicating a clear need for further basic zoological and ecological work on octocorals and zoantharians.
... This is particularly true within tropical regions, where temperature can more easily exceed the organisms' tolerance thresholds as they are already closer to their upper thermal limit, often resulting in higher species declines at lower latitudes (Pinsky et al., 2019;Stuart-Smith et al., 2015). Species with high tropical affinity able to expand or shift their distribution towards climatically suitable areas in response to changing climate could have higher survival rates and persistence over time (Greenstein & Pandolfi, 2008;Precht & Aronson, 2004). ...
Article
Full-text available
Aim Predicting and acting on the future of ecosystems requires understanding species distribution shifts due to climate change. We investigated which corals are more likely to shift their distribution in the Southwestern Atlantic under a warming scenario. Location Southwestern Atlantic (SWA; 1° N–28° S). Methods We used spatial distribution models with a Bayesian approach to predict the current and future (2050 and 2100) coral occurrence probabilities of 12 zooxanthellate corals and hydrocorals under an intermediate scenario of increasing greenhouse gas emissions (RCP6.0) projected by the Intergovernmental Panel on Climate Change (IPCC). Results We found a decline in the occurrence probabilities of all 12 taxa within the tropics (1° N–20° S) and an increase towards subtropical sites (20–28° S) as early as 2050. The most significant declines are projected to occur between 9° S and 20° S, a region that currently hosts the richest reef complex in the South Atlantic, the Abrolhos bank. The imminent loss of suitable habitat in the tropics mostly threatens the Brazilian endemics and range restricted corals Mussismilia braziliensis and Mussismilia harttii, while more widely distributed taxa such as Siderastrea spp., Millepora spp. and Porites spp. are expected to expand their ranges southwards. Main Conclusions The projected declines in the tropical region are likely to reduce structural complexity causing biodiversity loss. The overall increase in occurrence probabilities in subtropical areas indicates tropicalisation of SWA reefs, which may benefit species already established in these areas and potentially enrich coral assemblages through the range expansion of taxa that currently do not occur in the region. These findings emphasise the need to support ecological corridors that could aid coral migration towards more suitable habitats under climate change.
... Also, coral populations through genetic adaptations may be able to cope with the rapid changes in the temperature of oceans . Also, they may relocate to new areas to avoid changing conditions and it has been evident through studies where new coral reef species have been reported at high latitudes (Greenstein & Pandolfi, 2008;Precht & Aronson, 2004;Yamano et al., 2011). ...
Article
Full-text available
Humans have relied on oceans since time immemorial and have exploited them for natural resources and recreational activities. With the advancement of technologies, rapid population growth and land-use change, the dependability on marine ecosystems has increased tremendously. Anthropogenic activities are causing increased global temperatures, altered weather conditions, melting glaciers, rising sea levels, acidification etc. The biological processes of marine ecosystems are getting affected indirectly or directly from the molecular level to rock pools to ocean basins, thus impacting overall ecosystem services. Out of various disturbances being caused by humans, global warming has been one of the most threatening factors with other anthropogenic inputs such as nutrient enrichment, sewage and microplastics, thereby causing significant changes in the symbiotic relationship between algae and corals. The coral associations with algae, macroalgae and other groups play a very important role in the functioning of ocean ecosystems and are very sensitive to anthropogenic inputs. The symbiotic association of algae with corals results in enriched biodiversity as well as it maintains the biogeochemistry of oceans and open coastal areas. The review outlines the importance of algal associations towards the maintenance of coral reefs, along with discussing the ecological services offered by them. One of the sections also discusses the impact of anthropogenic activities on the association between corals and algae. Also, the potential adaptive response of corals to the changing climatic conditions, and conservation strategies for the conservation of coral ecosystems to ensure a sustainable environment have also been discussed. Graphical Abstract
Article
The Great Barrier Reef is the largest reef system in the modern ocean. To date, the influence of temperature on the origin and long-term evolution of the Great Barrier Reef remains enigmatic. Here, we present a 900–thousand year TEX 86 H -derived temperature proxy record from Ocean Drilling Program Site 820 in the Coral Sea. It demonstrates that the onset of reef growth on the outer shelf was preceded by a rise in summer temperature from ~26° to ~28°C at around 700 thousand years ago (marine isotope stage 17). This approximately 2°C rise in summer sea surface temperatures (SSTs) likely resulted in higher carbonate production rates, which were crucial for the formation of the Great Barrier Reef. Subsequently, reconstructed SSTs remained sufficiently warm for the Great Barrier Reef to thrive and evolve continuously. The evolution of the Great Barrier Reef, therefore, appears to be closely linked to SSTs.
Article
Tropical reef ecosystems are strongly influenced by the composition of coral species, but the factors influencing coral diversity and distributions are not fully understood. Here we demonstrate that large variations in the relative abundance of three major coral species across adjacent Caribbean reef sites are strongly related to their different low O 2 tolerances. In laboratory experiments designed to mimic reef conditions, the cumulative effect of repeated nightly low O 2 drove coral bleaching and mortality, with limited modulation by temperature. After four nights of repeated low O 2 , species responses also varied widely, from > 50% bleaching in Acropora cervicornis to no discernable sensitivity of Porites furcata. A simple metric of hypoxic pressure that combines these experimentally derived species sensitivities with high‐resolution field data accurately predicts the observed relative abundance of species across three reefs. Only the well‐oxygenated reef supported the framework‐building hypoxia‐sensitive Acropora cervicornis , while the hypoxia‐tolerant weedy species Porites furcata was dominant on the most frequently O 2 ‐deplete reef. Physiological exclusion of acroporids from these O 2 ‐deplete reefs underscores the need for hypoxia management to reduce extirpation risk.
Article
Understanding how tropical corals respond to temperatures is important to evaluating their capacity to persist in a warmer future. We studied the common Pacific coral Pocillopora over 44° of latitude, and used populations at three islands with different thermal regimes to compare their responses to temperature using thermal performance curves (TPCs) for respiration and gross photosynthesis. Corals were sampled in the local autumn from Moorea, Guam, and Okinawa where mean (± s.d.) annual seawater temperature is 28.0±0.9°C, 28.9±0.7°C, and 25.1±3.4°C, respectively. TPCs for respiration were similar among latitudes, the thermal optimum (Topt) was above the local maximum temperature at all three islands, and maximum respiration was lowest at Okinawa. TPCs for gross photosynthesis were wider, implying greater thermal eurytopy, with a higher Topt in Moorea versus Guam and Okinawa. Topt was above the maximum temperature in Moorea, but was similar to daily temperatures over 13% of the year in Okinawa, and 53% of the year in Guam. There was greater annual variation in daily temperatures in Okinawa than Guam or Moorea, which translated to large variation in the supply of metabolic energy and photosynthetically fixed carbon at higher latitudes. Despite these trends, the differences in TPCs for Pocillopora were not profoundly different across latitudes, reducing the likelihood that populations of these corals could better match their phenotypes to future more extreme temperatures through migration. Any such response would place a premium on high metabolic plasticity and tolerance of large seasonal variations in energy budgets.
Article
Full-text available
Mass mortalities due to disease outbreaks have recently affected major taxa in the oceans. For closely monitored groups like corals and marine mammals, reports of the frequency of epidemics and the number of new diseases have increased recently. A dramatic global increase in the severity of coral bleaching in 1997–98 is coincident with high El Niño temperatures. Such climate-mediated, physiological stresses may compromise host resistance and increase frequency of opportunistic diseases. Where documented, new diseases typically have emerged through host or range shifts of known pathogens. Both climate and human activities may have also accelerated global transport of species, bringing together pathogens and previously unexposed host populations.
Chapter
Full-text available
In recent decades, the cover of fleshy macroalgae has increased and coral cover has decreased on most Caribbean reefs. Coral mortality precipitated this transition, and the accumulation of macroalgal biomass has been enhanced by decreased herbivory and increased nutrient input. Populations of Acropora palmata (elkhorn coral) and A. cervicornis (staghorn coral), two of the most important framework-building species, have died throughout the Caribbean, substantially reducing coral cover and providing substratum for algal growth. Hurricanes have devastated local populations of Acropora spp. over the past 20–25 years, but white-band disease, a putative bacterial syndrome specific to the genus Acropora, has been a more significant source of mortality over large areas of the Caribbean region. Paleontological data suggest that the regional Acropora kill is without precedent in the late Holocene. In Belize, A. cervicornis was the primary ecological and geological constituent of reefs in the central shelf lagoon until the mid-1980s. After constructing reef framework for thousands of years, A. cervicornis was virtually eliminated from the area over a ten-year period. Evidence from other parts of the Caribbean supports the hypothesis of continuous Holocene accumulation and recent mass mortality of Acropora spp. Prospects are poor for the rapid recovery of A. cervicornis, because its reproductive strategy emphasizes asexual fragmentation at the expense of dispersive sexual reproduction. A. palmata also relies on fragmentation, but this species has a higher rate of sexual recruitment than A. cervicornis If the Acropora spp. do not recover, macroalgae will continue to dominate Caribbean reefs, accompanied by increased abundances of brooding corals, particularly Agaricia spp. and Porites spp. The outbreak of white-band disease has been coincident with increased human activity, and the possibility of a causal connection should be further investigated.
Article
Full-text available
The final effort of the CLIMAP project was a study of the last interglaciation, a time of minimum ice volume some 122,000 yr ago coincident with the Substage 5e oxygen isotopic minimum. Based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean, last interglacial sea-surface temperatures (SST) were compared with those today. There are small SST departures in the mid-latitude North Atlantic (warmer) and the Gulf of Mexico (cooler). The eastern boundary currents of the South Atlantic and Pacific oceans are marked by large SST anomalies in individual cores, but their interpretations are precluded by no-analog problems and by discordancies among estimates from different biotic groups. In general, the last interglacial ocean was not significantly different from the modern ocean. The relative sequencing of ice decay versus oceanic warming on the Stage 6/5 oxygen isotopic transition and of ice growth versus oceanic cooling on the Stage 5e/5d transition was also studied. In most of the Southern Hemisphere, the oceanic response marked by the biotic census counts preceded (led) the global ice-volume response marked by the oxygen-isotope signal by several thousand years. The reverse pattern is evident in the North Atlantic Ocean and the Gulf of Mexico, where the oceanic response lagged that of global ice volume by several thousand years. As a result, the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years. These regional lead-lag relationships agree with those observed on other transitions and in long-term phase relationships; they cannot be explained simply as artifacts of bioturbational translations of the original signals.
Article
AN extensive Acropora palamata (Lamarck) barrier reef flourished off the south-east coast of Florida in an area considerably north of present-day reef development during the early Holocene transgression. Pipeline construction across the continental shelf 40km north of Miami (26°15′15″N, 80°03′52″W) has disclosed this relict shelf-edge reef that is at least 95 km long. Radiocarbon dates indicate that reef growth terminated ∼7,000 yr ago, which coincides with the time of extensive flooding of the continental shelf. This relict barrier reef forms a low (10-m relief) ridge-the crest of which occurs at depths of 15-30 m-extending along the shelf break from Palm Beach southwards to Miami1,2. Present-day fauna on the surface of the ridge include alcyonarians, sponges and scattered coral heads 2,3. The study reported here indicates that the early Holocene provided favourable conditions for reef development in the western Atlantic.