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At least 505 records · Page 28Linked to original sources
USGS2008

The dynamics of coastal models

Coastal basins are defined as estuaries, lagoons, and embayments. This book deals with the science of coastal basins using simple models, many of which are presented in either analytical form or Microsoft Excel or MATLAB. The book introduces simple hydrodynamics and its applications, from the use of simple box and one-dimensional models to flow over coral reefs. The book also emphasizes models as a scientific tool in our understanding of coasts, and introduces the value of the most modern flexible mesh combined wave-current models. Examples from shallow basins around the world illustrate the wonders of the scientific method and the power of simple dynamics. This book is ideal for use as an advanced textbook for graduate students and as an introduction to the topic for researchers, especially those from other fields of science needing a basic understanding of the basic ideas of the dynamics of coastal basins.

Book↗
USGS1991

Impact of exploratory wells, offshore Florida: A biological assessment

Seven offshore exploratory oil well sites were examined in an effort to determine the ecological impact of exploratory drilling on the subtropical marine ecosystems of southern Florida, including seagrass beds and coral reefs. The time since drilling ranged from 2 to 29 years; water depths varied between 5 and 70 m. The major long-term ecological impact observed at these sites ranged from the creation of "artificial-reef" conditions to the physical destruction of hardbottom habitat that had not recovered in 29 years. Long-term ecological perturbation appeared to be limited to physical destruction and the deposition of drilling debris, which provided substratum for settling organisms. Significant deposits of drill muds or cuttings were not encountered at any of the sites, and there was no evidence of ecological damage from cuttings or drill muds. The results of this study pertain only to exploratory drilling that, unlike production wells that remain in place for tens of years, is a one-time perturbation to the habitat.

Florida↗
USGS2007

Coastal systems and low-lying areas

Since the IPCC Third Assessment Report (TAR), our understanding of the implications of climate change for coastal systems and low-lying areas (henceforth referred to as ‘coasts’) has increased substantially and six important policy-relevant messages have emerged. Coasts are experiencing the adverse consequences of hazards related to climate and sea level (very high confidence). Coasts are highly vulnerable to extreme events, such as storms, which impose substantial costs on coastal societies [6.2.1, 6.2.2, 6.5.2]. Annually, about 120 million people are exposed to tropical cyclone hazards, which killed 250,000 people from 1980 to 2000 [6.5.2]. Through the 20th century, global rise of sea level contributed to increased coastal inundation, erosion and ecosystem losses, but with considerable local and regional variation due to other factors [6.2.5, 6.4.1]. Late 20th century effects of rising temperature include loss of sea ice, thawing of permafrost and associated coastal retreat, and more frequent coral bleaching and mortality [6.2.5]. Coasts will be exposed to increasing risks, including coastal erosion, over coming decades due to climate change and sea-level rise (very high confidence). Anticipated climate-related changes include: an accelerated rise in sea level of up to 0.6 m or more by 2100; a further rise in sea surface temperatures by up to 3°C; an intensification of tropical and extra-tropical cyclones; larger extreme waves and storm surges; altered precipitation/run-off; and ocean acidification [6.3.2]. These phenomena will vary considerably at regional and local scales, but the impacts are virtually certain to be overwhelmingly negative [6.4, 6.5.3]. Corals are vulnerable to thermal stress and have low adaptive capacity. Increases in sea surface temperature of about 1 to 3°C are projected to result in more frequent coral bleaching events and widespread mortality, unless there is thermal adaptation or acclimatisation by corals [Box 6.1, 6.4]. Coastal wetland ecosystems, such as saltmarshes and mangroves, are especially threatened where they are sediment starved or constrained on their landward margin [6.4.1]. Degradation of coastal ecosystems, especially wetlands and coral reefs, has serious implications for the well-being of societies dependent on the coastal ecosystems for goods and services [6.4.2, 6.5.3]. ncreased flooding and the degradation of freshwater, fisheries and other resources could impact hundreds of millions of people, and socio-economic costs on coasts will escalate as a result of climate change [6.4.2, 6.5.3]. The impact of climate change on coasts is exacerbated by increasing human-induced pressures (very high confidence). Utilisation of the coast increased dramatically during the 20th century and this trend is virtually certain to continue through the 21st century. Under the SRES scenarios, the coastal population could grow from 1.2 billion people (in 1990) to 1.8 to 5.2 billion people by the 2080s, depending on assumptions about migration [6.3.1]. Increasing numbers of people and assets at risk at the coast are subject to additional stresses due to land-use and hydrological changes in catchments, including dams that reduce sediment supply to the coast [6.3.2]. Populated deltas (especially Asian megadeltas), low-lying coastal urban areas and atolls are key societal hotspots of coastal vulnerability, occurring where the stresses on natural systems coincide with low human adaptive capacity and high exposure [6.4.3]. Regionally, South, South- East and East Asia, Africa and small islands are most vulnerable [6.4.2]. Climate change therefore reinforces the desirability of managing coasts in an integrated manner [6.6.1.3]. Adaptation for the coasts of developing countries will be more challenging than for coasts of developed countries, due to constraints on adaptive capacity (high confidence). While physical exposure can significantly influence vulnerability for both human populations and natural systems, a lack of adaptive capacity is often the most important factor that creates a hotspot of human vulnerability. Adaptive capacity is largely dependent upon development status. Developing nations may have the political or societal will to protect or relocate people who live in low-lying coastal zones, but without the necessary financial and other resources/capacities, their vulnerability is much greater than that of a developed nation in an identical coastal setting. Vulnerability will also vary between developing countries, while developed countries are not insulated from the adverse consequences of extreme events [6.4.3, 6.5.2]. Adaptation costs for vulnerable coasts are much less than the costs of inaction (high confidence). Adaptation costs for climate change are much lower than damage costs without adaptation for most developed coasts, even considering only property losses and human deaths [6.6.2, 6.6.3]. As post-event impacts on coastal businesses, people, housing, public and private social institutions, natural resources, and the environment generally go unrecognised in disaster cost accounting, the full benefits of adaptation are even larger [6.5.2, 6.6.2]. Without adaptation, the high-end sea-level rise scenarios, combined with other climate changes (e.g., increased storm intensity), are as likely as not to render some islands and lowlying areas unviable by 2100, so effective adaptation is urgently required [6.6.3]. The unavoidability of sea-level rise, even in the longer-term, frequently conflicts with present-day human development patterns and trends (high confidence). Sea-level rise has substantial inertia and will continue beyond 2100 for many centuries. Irreversible breakdown of the West Antarctica and/or Greenland ice sheets, if triggered by rising temperatures, would make this long-term rise significantly larger, ultimately questioning the viability of many coastal settlements across the globe. The issue is reinforced by the increasing human use of the coastal zone. Settlement patterns also have substantial inertia, and this issue presents a challenge for long-term coastal spatial planning. Stabilisation of climate could reduce the risks of ice sheet breakdown, and reduce but Chapter 6 Coastal systems and low-lying areas 317 not stop sea-level rise due to thermal expansion [Box 6.6]. Hence, it is now more apparent than it was in the TAR that the most appropriate response to sea-level rise for coastal areas is a combination of adaptation to deal with the inevitable rise, and mitigation to limit the long-term rise to a manageable level [6.6.5, 6.7].

Book chapter↗
USGS2003

The seagrasses of the Gulf of Mexico

The Gulf of Mexico is a vast basin of water, spanning 12° of latitude, from 18° to 30°N. and 17° of longitude, from 81° to 98°W. It is bisected by the Tropic of Cancer and is largely subtropical; however, along the northern edge, up to five days with freezing temperatures are probable on an annual basis. The coastal fringe is moist, with annual precipitation in excess of 1 000 mm, except for southern Texas and northern Mexico. Precipitation is concentrated in the summer period, most pronounced along the coast of Mexico and least pronounced along the coast of Louisiana. Most of the Gulf of Mexico is fringed by a broad coastal plain, except for northwestern Cuba and sections of the Mexican coast near Veracruz. The inner continental shelf to a depth of 20 m is broad off the western side of the Yucatan Peninsula, along the coast of Louisiana and along the western side of Florida, extending as much as 80 km offshore to the tip of Florida. Elsewhere, the inner shelf is relatively narrow. Most of the rivers draining into the Gulf of Mexico have restricted catchments, except along the north shore, most obviously the Mississippi River, and parts of the western gulf, including the Rios Bravo IGrandel, Panuco, Grijalva and Usumacinta. Barrier islands and spits are prominent features along much of the coast, and coral reefs shelter the large expanse of water off the southern tip of Florida and off the coasts of Veracruz, Campeche, Yucatan and northwestern Cuba. Lunar spring tides are less than 1 m throughout the region.

Book chapter↗
USGS2021

Measuring coastal acidification using in situ sensors in the National Estuary Program

Estuaries and coastal areas are highly vulnerable to the impacts of acidification on shellfish, coral reefs, fisheries, and the commercial and recreational industries that they support. Yet, little is known about the extent of this vulnerability and the estuary-specific drivers that contribute to acidification, such as nutrient enrichment from stormwater, agriculture and wastewater discharges, upwelling of CO 2 -rich seawater, elevated atmospheric CO 2 from urban and agricultural activities, benthic and marsh-driven processes, and alkalinity and carbon content of freshwater flows. Comprehensive, high resolution monitoring data are needed at varying spatial and temporal scales to provide actionable information tailored to each estuary. Because carbonate chemistry in the coastal environment can be affected by nutrient dynamics, understanding how nutrient inputs exacerbate acidification impacts is essential for the formulation of estuary-specific actions.

Alabama, California, Connecticut, Delaware. Florid↗
USGS2020

Annual outbreaks of coral disease coincide with extreme seasonal warming

Reef-building corals living in extreme environments can provide insight into the negative effects of future climate scenarios. In hot environments, coral communities experience disproportionate thermal stress as they live very near or at their upper thermal limits. This results in a high frequency of bleaching episodes, but it is unknown whether temperature-driven outbreaks of coral disease follow a similar trajectory. Here we tracked outbreaks of a white-syndrome (WS) disease over three years in the hottest region inhabited by reef-building corals, the southern Persian Gulf. From 2014 to 2016, WS affected 10 of the 16 scleractinian genera recorded at inshore and offshore sites. Intra- and inter-specific transmission of lesions was frequently observed, indicative of a single contagious disease infecting multiple coral taxa. Colonies of Acropora were the most susceptible to WS disease and were more than twice as likely to experience lesions than any other genera. Prevalence reached 42% of Acropora colonies and lesions progressed at an average rate of 1 mm day −1 . Platygyra colonies were the second most susceptible to WS disease, where prevalence reached 33% and lesions progressed at 0.3 mm day −1 . Affected colonies of both of these genera suffered considerable partial mortality that was not recovered between years, promoting the fragmentation of larger colonies into smaller size classes. Across the 3 years of our study, the onset of WS outbreaks occurred early in summer and prevalence increased exponentially with cumulative heat exposure (coral community r 2 = 0.55, Acropora r 2 = 0.72, Platygyra r 2 = 0.75). Peak levels of community-wide prevalence occurred in August (10% of all coral colonies) to September (14%) when preceding 4-week and 8-week average temperatures exceeded 34.5 °C and 34 °C, respectively. Outbreaks ceased following the return of cooler temperatures with prevalence remaining below 0.5% between December and June. Levels of bleaching remained relatively low (< 5% prevalence), despite exposure to daily temperatures ≥ 35 °C each summer. These findings demonstrate that thermal stress on coral reefs does not always manifest as coral bleaching and diseases can present as a primary sign of thermal stress. Consequently, temperature-driven outbreaks of coral disease are expected to become more widespread as climate warming pushes corals to be living increasingly closer to their upper thermal limits.

Saadiyat Island, Sir Bu Nair Island↗
USGS2019

Physical mechanisms influencing localized patterns of temperature variability and coral bleaching within a system of reef atolls

Interactions between oceanic and atmospheric processes within coral reefs can significantly alter local-scale (< km) water temperatures, and consequently drive variations in heat stress and bleaching severity. The Scott Reef atoll system was one of many reefs affected by the 2015–2016 mass coral bleaching event across tropical Australia, and specifically experienced sea surface temperature anomalies of 2 °C that caused severe mass bleaching (> 60%) over most of this system; however, the bleaching patterns were not uniform. Little is known about the processes governing thermodynamic variability within atolls, particularly those that are dominated by large amplitude tides. Here, we identify three mechanisms at Scott Reef that alleviated heat stress during the marine heatwave in 2016: (1) the cool wake of a tropical cyclone that induced temperature drops of 1.3 °C over a period of 8 days; (2) air–sea heat fluxes that interacted with the reef morphology during neap tides at one of the atolls to reduce water temperatures by up to 2.9 °C; (3) internal tidal processes that forced deeper and cooler water (up to 2.7 °C) into some sections of the shallow reefs. The latter two processes created localized areas of reduced temperatures that led to lower incidences of coral bleaching for parts of the reef. We predict these processes are likely to occur in other similar tide-dominated reef environments worldwide. Identifying locations where physical processes reduce heat stress will likely be critical for coral reefs in the future, by maintaining communities that can help facilitate local recovery of reefs following bleaching events that are expected to increase in frequency and severity in the coming decades.

Coral Reefs↗
USGS2020

A revised Holocene coral sea-level database from the Florida reef tract, USA

The coral reefs and mangrove habitats of the south Florida region have long been used in sea-level studies for the western Atlantic because of their broad geographic extent and composition of sea-level tracking biota. The data from this region have been used to support several very different Holocene sea-level reconstructions (SLRs) over the years. However, many of these SLRs did not incorporate all available coral-based data, in part because detailed characterizations necessary for inclusion into sea-level databases were lacking. Here, we present an updated database comprised of 303 coral samples from published sources that we extensively characterized for the first time. The data were carefully screened by evaluating and ranking the visual taphonomic characteristics of every dated sample within the database, which resulted in the identification of 134 high-quality coral samples for consideration as suitable sea-level indicators. We show that our database largely agrees with the most recent SLR for south Florida over the last ~7,000 years; however, the early Holocene remains poorly characterized because there are few high-quality data spanning this period. Suggestions to refine future Holocene SLRs in the region are provided including filling spatial and temporal data gaps of coral samples, particularly from the early Holocene, as well as constructing a more robust peat database to better constrain sea-level variability during the middle to late Holocene. Our database and taphonomic-ranking protocol provide a framework for researchers to evaluate data-selection criteria depending on the robustness of their sea-level models.

Florida↗
USGS2023

Expanding our view of the cold-water coral niche and accounting of the ecosystem services of the reef habitat

Coral reefs are iconic ecosystems that support diverse, productive communities in both shallow and deep waters. However, our incomplete knowledge of cold-water coral (CWC) niche space limits our understanding of their distribution and precludes a complete accounting of the ecosystem services they provide. Here, we present the results of recent surveys of the CWC mound province on the Blake Plateau off the U.S. east coast, an area of intense human activity including fisheries and naval operations, and potentially energy and mineral extraction. At one site, CWC mounds are arranged in lines that total over 150 km in length, making this one of the largest reef complexes discovered in the deep ocean. This site experiences rapid and extreme shifts in temperature between 4.3 and 10.7 °C, and currents approaching 1 m s −1 . Carbon is transported to depth by mesopelagic micronekton and nutrient cycling on the reef results in some of the highest nitrate concentrations recorded in the region. Predictive models reveal expanded areas of highly suitable habitat that currently remain unexplored. Multidisciplinary exploration of this new site has expanded understanding of the cold-water coral niche, improved our accounting of the ecosystem services of the reef habitat, and emphasizes the importance of properly managing these systems.

Scientific Reports↗
USGS2008

Coral and crustose coralline algae disease on the reefs of American Samoa

Surveys for lesions in corals were conducted at seven sites around Tutuila in June 2004 and January 2005. The objectives of the study were to document the distribution and prevalence of disease in the major genera of corals and crustose coralline algae, systematically describe gross and microscopic morphology of lesions in reef corals and determine whether there are seasonal differences in prevalence of disease. We documented 12 different coral disease states from the reefs of Tutuila and two diseases of crustose coralline algae (CCA). Acropora white syndrome, Acropora growth anomalies and coralline lethal orange disease were the most common diseases on the reefs of Tutuila. No seasonal differences were found in overall prevalence of coral or abundance of CCA disease. Histological analyses of coral lesions revealed that microscopic changes in tissues can be used to distinguish tissue loss due to trauma from changes due to disease, detect micro-organisms associated with certain types of discolorations and found that hyperplasia of the basal body wall was the hallmark microscopic appearance of Acropora growth anomalies regardless of gross morphology of tumors.

Conference Paper↗
USGS2021

Wave-driven flood-forecasting on reef-lined coasts early warning system (WaveFoRCE)

Increasing the resilience of coastal communities while decreasing the risk to them are key to the continued inhabitance and sustainability of these areas. Low-lying coral reef-lined islands are experiencing storm wave-driven flood events that currently strike with little to no warning. These events are occurring more frequently and with increasing severity. There is a need along the world’s coral reef-lined coasts for a tool that can forecast the timing and severity of wave-driven flooding events. Without this tool, coastal communities are vulnerable to: loss of life from drowning • loss of, and damage to, property and infrastructure • decreasing viability of communities via loss of, and damage to crops, fishing (via decreased water quality and wave-damaged reefs), and freshwater resources • reduction of livable land due to increased erosion and salt intrusion. The currently available tools were developed for sandy shorelines and do not accurately predict wave-driven flooding on reef-lined coasts, leaving inhabitants without accurate and timely warnings. In addition, the flood models that do exist for reef-lined coasts have only been implemented on a small number of areas throughout the world because running these models is costly and requires a high level of computing power. Using these existing models and techniques to generate high-resolution forecasts for wave-driven flooding for all reef-lined coasts would cost approximately US$1 billion. To remedy this issue, an international team associated with the GEO Blue Planet initiative is working to develop a wave-driven flood-forecasting early-warning system (EWS) for coral reef-lined coasts known as WaveFoRCE. The system aims to provide all nations and people living on a coral reef-lined coast anywhere in the world with an up to 7.5-day forecast of storm wave-driven flood events.

Newsletter↗
USGS2006

Airborne lidar sensing of massive stony coral colonies on patch reefs in the northern Florida reef tract

In this study we examined the ability of the NASA Experimental Advanced Airborne Research Lidar (EAARL) to discriminate cluster zones of massive stony coral colonies on northern Florida reef tract (NFRT) patch reefs based on their topographic complexity (rugosity). Spatially dense EAARL laser submarine topographic soundings acquired in August 2002 were used to create a 1-m resolution digital rugosity map for adjacent NFRT study areas characterized by patch reefs (Region A) and diverse substratums (Region B). In both regions, sites with lidar-sensed rugosities above 1.2 were imaged by an along-track underwater videography system that incorporated the acquisition of instantaneous GPS positions. Subsequent manual interpretation of videotape segments was performed to identify substratum types that caused elevated lidar-sensed rugosity. Our study determined that massive coral colony formation, modified by subsequent physical and biological processes that breakdown patch reef framework, was the primary source of topographic complexity sensed by the EAARL in the NFRT. Sites recognized by lidar scanning to be topographically complex preferentially occurred around the margins of patch reefs, constituted a minor fraction of the reef system, and usually reflected the presence of massive coral colonies in cluster zones, or their derivatives created by mortality, bioerosion, and physical breakdown.

Florida↗
USGS2001

A lone biodetrital mound in the Chesterian (Carboniferous) of Alabama?

A carbonate mound in the Chesterian Bangor Limestone of Lawrence County, Alabama, consists chiefly of packstone and grainstone dominated by echinoderm ossicles and fragments of fenestrate bryozoans. In-situ colonies of the rugose coral Caninia flaccida comprise about 8% of the mound by volume. The exposed portion of the mound is approximately 25 m wide, 1.6 m thick at the thickest point and roughly circular in plan. The mound developed on top of a shallow ooid shoal that had been cemented and stabilised during an earlier episode of sub-aerial exposure. Subsequent flooding of the exposed shoal surface permitted establishment of the mound biota. Lateral and vertical facies relationships suggest that the mound possessed about 45 cm of synoptic relief when fully developed. Rugose corals, fenestrate and ramose bryozoans, stalked echinoderms, and sessile soft-bodied organisms encrusted by foraminifera colonised the shoal, forming a mound. Baffling resulted in deposition of mixed-fossil packstone containing locally derived debris and coated grains from the surrounding sea floor. Strong currents within the mound are indicated by preferred orientation of corals and by coarse, commonly cross-stratified grainstone in channels between neighboring coral colonies. Corals are most abundant on the windward side of the mound, where they account for about 13% of the mound compared to 6- 10% in the central part of the mound, and 2-4% on the leeward flank. Biodetrital mounds such as the one described here are uncommon in upper Paleozoic strata and previously unknown in the Bangor Limestone. Of 10 carbonate buildups we examined in the Bangor in Alabama and Tennessee, only one is a biodetrital mound. Two are rugose coral-microbial reefs, one is a coral biostrome, and six are dominated by microbialite. The Bangor shelf, previously interpreted as sedimentologically simple, appears to contain many small mounds of quite varied characteristics. Also, the discovery of a biodetrital mound in the Chesterian of Alabama suggests that there may be more kinds of upper Paleozoic mounds than commonly acknowledged. ?? 2001 Elsevier Science B.V. All rights reserved.

Sedimentary Geology↗
USGS2020

Testing glacial isostatic adjustment models of last-interglacial sea level history in the Bahamas and Bermuda

Part of the spatial variation in the apparent sea-level record of the last interglacial (LIG) period is due to the diverse response of coastlines to glacial isostatic adjustment (GIA) processes, particularly where coastlines were close to the Laurentide Ice Sheet during the past two glacial periods. We tested modeled LIG paleo-sea levels on New Providence Island (NPI), Bahamas and Bermuda by investigating emergent coral patch reefs and oolitic/peloidal beach deposits. Corals with closed-system histories collected from patch reefs on NPI have ages of 128-118 ka and ooids/peloids from beach ridges have closed-system ages of 128-116 ka. Elevations of patch reefs indicate a LIG paleo-sea level of at least ∼7 m to ∼9 m above present. Beach ridge sediments indicate paleo-sea levels of ∼5 m to ∼14 m (assuming subsidence, ∼7 m to ∼16 m) above present during the LIG. Some, though not all of these measurements are in good agreement with GIA models of paleo-sea level that have been simulated for the Bahamas. On Bermuda, corals with closed-system histories collected from marine deposits have ages of 126-114 ka. Although coral-bearing marine deposits on Bermuda lack the precise indication of paleo-sea level provided by patch reefs and oolitic beach ridges, these sediments nevertheless provide at least a first-order estimate of paleo-sea level. Paleo-sea level records on Bermuda are consistently lower (∼2 m to ∼7 m) than what GIA models simulate for the LIG. The reason for the reasonable agreement with models for the Bahamas and poor agreement for Bermuda is not understood, but needs further investigation in light of the probability of a higher sea level in the near future.

Quaternary Science Reviews↗
USGS2009

Applying New Methods to Diagnose Coral Diseases

Coral disease, one of the major causes of reef degradation and coral death, has been increasing worldwide since the 1970s, particularly in the Caribbean. Despite increased scientific study, simple questions about the extent of disease outbreaks and the causative agents remain unanswered. A component of the U.S. Geological Survey Coral Reef Ecosystem STudies (USGS CREST) project is focused on developing and using new methods to approach the complex problem of coral disease.

Fact Sheet↗
USGS2010

Coral calcification in a changing ocean

Animals and plants that live in the ocean form skeletons and other hard parts by combining calcium ions and carbonate ions to create calcium carbonate. This process is called calcification. In tropical and subtropical oceans, the calcification of corals and other organisms creates reefs that protect islands, produce beautiful white-sand beaches, and create habitat for thousands of species that live on coral reefs. Many reefs around the globe are declining in health. Live, reef-building corals are becoming scarcer, often being replaced by fleshy algae (seaweeds) that do not build reefs. Many factors contribute to reef decline, but scientific consensus is that coral bleaching, coral disease, overfishing, and coastal development are largely to blame. It is the role of the U.S. Geological Survey (USGS) to provide science that informs the decision-making process of those who are tasked with managing reef resources under U.S. jurisdiction. One of the goals of the Coral Reef Ecosystem Studies (CREST) project is to examine how calcification rates in reef-building corals and encrusting coralline algae are changing in response to changes in the ocean environment.

Fact Sheet↗
USGS2015

A new record of the late Pleistocene coral Pocillopora palmata from the Dry Tortugas, Florida reef tract, USA

Pocilloporid corals dominated shallow-water environments in the Caribbean during much of the Cenozoic; however, the regional diversity of this family declined over the last 15 My, culminating with the extinction of its final member, Pocillopora palmata , during the latest Pleistocene. Here we present a new record of P. palmata from Dry Tortugas National Park in the Florida Keys and infer its likely age. Although most existing records of P. palmata are from the sub-aerial reef deposits of MIS5e (&sim; 125 ka), the presently submerged reef in the Dry Tortugas was too deep (> 18 m) during this period to support significant reef growth. In contrast, the maximum water depth during MIS5a (&sim; 82 ka) was only &sim; 5.6 m, which would have been ideal for P. palmata . Diagenetic alteration prevented direct dating of the samples; however, the similarity between the depths of the Pleistocene bedrock in the Dry Tortugas and other reefs in the Florida Keys, which have been previously dated to MIS5a, support the conclusion that P. palmata likely grew in the Dry Tortugas during this period. Our study provides important new information on the history of P. palmata , but it also highlights the vital need for more comprehensive studies of the Quaternary history of Caribbean reef development. With modern reef degradation already driving yet another restructuring of Caribbean coral assemblages, insights from past extinctions may prove critical in determining the prognosis of Caribbean reefs in the future.

Florida↗