Dense saline plumes in Exuma Sound, Bahamas

Hickey, Barbara M.; MacCready, Parker; Elliott, Emily; Kachel, Nancy B.

doi:10.1029/2000jc900004

Cited by 39 publications

(41 citation statements)

References 19 publications

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“…For 9 of the 12 ⌬ Ͻ 0.01 kg m Ϫ3 , which is less than criteria used elsewhere to estimate an actively mixing layer depth (Brainerd and Gregg 1995). It is most often the case in Exuma Sound that the mixed layer depth is Ͼ20 m and thus encompasses the reef and adjacent sand flats within it (Hickey et al 2000). This suggests that the observed gradients between properties above different substrates are not aliased significantly by vertical gradients.…”

Section: Methodsmentioning

confidence: 93%

The effect of bottom substrate on inherent optical properties: Evidence of biogeochemical processes

Boss

Zaneveld

2003

Limnology & Oceanography

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Measurements of inherent optical properties (IOP) were conducted over bottoms with different substrates by use of a sampling package mounted on and operated by a SCUBA diver. It was found that in areas of low ambient currents the distribution of IOP varies with bottom type in (1) its value relative to a nearby bottom of different type, (2) its vertical gradient, and (3) its variability. This implies that radiative transfer modeling in shallow environments may need to include, besides the bottom characteristics, the bottom effect on in-water IOP. In tidally flushed shallow banks, vertical and horizontal gradients over scales of O(1, 10 m), respectively, are as large as temporal gradients over scales of minutes and cannot be separated in our measurements. However, bottom-substraterelated processes over the banks result in gradients over large horizontal spatial scales and tidal timescales. The distribution of IOP is consistent with several biogeochemical processes that may be active at a given bottom substrate and suggest that optical measurements may provide a useful tool to infer and quantify bulk rates of biogeochemical processes.The classic forward problem in ocean optics is the calculation of the distribution of radiance in space given the optical properties of the medium (the inherent optical properties [IOP]; Preisendorfer 1976) and appropriate boundary conditions. To solve this ''forward'' problem, we need to know the details of the light source or sources (e.g., the solar spectrum and its direct and diffuse light just above the ocean), transmission through the boundaries of the domain (e.g., a wave-modulated air-ocean interface), and the optical properties of the medium. In the ocean, photons interact with the water molecules and with dissolved and particulate material within the water. These constituents determine the IOP of any given water mass. In shallow waters, an additional complexity comes from the existence of a bottom boundary, which interacts with light (through absorption and reflection).The forward problem is of importance for interpretation of remotely sensed ocean color in shallow areas (e.g., Lee et al. 1999;Carder et al. 2003) and for systems designed to image the bottom (e.g., for classification of bottom substrate and target recognition; McLean et al. 1995). In order to understand the distribution of IOP in space and time, we need to understand their relationship to processes occurring in the ocean as well as processes associated with the bottom.The ocean bottom affects light propagation not only through its own optical properties; the bottom substrate and AcknowledgmentsThis research was sponsored by the Coastal Benthic Optical Properties initiative of the Office of Naval Research. We thank R. Wheatcroft for providing us his current velocity measurements. Discussions with R. Zimmerman and D. Burdige initiated the porewater sampling. We thank P. Hill for an insightful review of an earlier version of this manuscript and J. Washburn and F. Baratange for assistance in sampling and i...

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Section: Methodsmentioning

confidence: 93%

The effect of bottom substrate on inherent optical properties: Evidence of biogeochemical processes

Boss

Zaneveld

2003

Limnology & Oceanography

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“…AVHRR satellite images of the study sites in the Bahamas show that the bank area behind Harbor Island on Eleuthera, which drains over some of the study sites (all Harbor Island sites) heats and cools more than the surrounding open ocean in summer and winter, respectively. It is known from the Bahamas that bank waters can become hyperpycnal either by heating or strong cooling and drain over the shelf-edge (Hickey et al 2000;Smith 2001), where they can cause bleaching of corals (Lang et al 1988). We assume that such a process happened in Eleuthera in Summer 1998 where heated, hyperpycnal shelf-water would have drained from the Bank area behind Harbor Island and probably propagated along the shelf-edge which caused the strong bleaching of corals not only at shallow but also at intermediate depths (1-30 m, Fig.…”

Section: Water Temperature In the Bahamasmentioning

confidence: 99%

Possible refugia for reefs in times of environmental stress

Riegl

Piller

2003

International Journal of Earth Sciences

306

227

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This paper investigates the refuge potential of (1) upwelling areas, (2) coral areas at medium depth, and (3) offshore bank and island reefs in a scenario of increased global warming, and thus increased sea surface temperature (SST) and increased solar UV radiation. (1) Observations on coral health and water temperature in the subtropical Atlantic (Eleuthera and Cat Island, Bahamas) and Indian Ocean (Sodwana Bay, South Africa) suggest a link between cool water delivered by upwelling and coral health. After the 1998 bleaching event, caused by strong SST anomalies, coral health and recovery from the previous year's bleaching was significantly better on the narrow southern Cat Island shelf (70% of corals healthy) where the presence of cold water was observed, which was attributed to small-scale upwelling, than on the wide northern Eleuthera shelf (44% of corals healthy), where downwelling of hot bank waters was believed to have damaged corals. In South Africa, regular, short-term upwelling events in five summers reduced SST to well below bleaching level. (2) In the northern Red Sea (Safaga Bay) and in South Africa (Sodwana Bay), wide areas with either coral frameworks or non-framework communities exist. Calculations show that if the top 10 m (20 m) of the ocean became inhospitable to corals, still 50.4% (17.5%) of the coral area would remain intact in the Red Sea and 99% (40%) in South Africa. (3) Offshore bank and island reefs investigated in the Turks, Caicos, and Mouchoir Banks and Grand and Little Cayman showed high rates of mortality and coral diseases. The most remote sites (Mouchoir Bank) were not the healthiest. Refuge areas appear to exist in (1) and (2), but in (3) only if vigorous water-circulation is encountered.

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“…While hurricanes and tsunamis have a smaller direct impact at greater depths, they may wash limestone rubble down the reef slope, potentially smothering MCEs (Bak et al 2005). Moreover, there is some indication that oscillations in sea temperatures, such as those caused by internal waves, cold-water intrusion, and down-welling of warmer waters, may extend to deeper depths and cause depauperate zones, stress, bleaching, and eventually death (Hickey et al 2000;Smith 2001;Wolanski et al 2004;Colin 2009;Smith et al 2010). Although such potential threats are mostly speculative at this time, in certain locations encroaching threats have begun to adversely affect the condition of MCEs (Menza et al 2007).…”

Section: Introduction To Mesophotic Coral Ecosystemsmentioning

confidence: 99%

Theme section on “Mesophotic Coral Ecosystems: Characterization, Ecology, and Management”

et al. 2010

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Mesophotic coral ecosystems (MCEs) are characterized by the presence of light-dependent corals and associated communities that are typically found at depths ranging from 30 to 40 m and extending to over 150 m in tropical and subtropical regions. The dominant communities providing structural habitat in the mesophotic zone can be comprised of coral, sponge, and algal species. Because working in this depth range is constrained by traditional SCUBA limits, less is known about corals and associated organisms there compared to shallower coral communities. Following the first-ever gathering of international scientists to review and discuss existing knowledge of MCEs, this issue focuses on the ecological characterization, geomorphology, and concept of MCEs as refugia for shallow-water populations. The review and research papers comprising this special issue reflect the current scientific understanding of these ecosystems and the underlying mechanisms that regulate them, as well as potential resource management implications. It is important to understand the value and role of mesophotic coral ecosystems in tropical and subtropical regions as these areas face increasing environmental change and human impacts Keywords Mesophotic coral ecosystem Á Biodiversity Á Geomorphology Á Connectivity Á Community structure Á Resource management Mesophotic coral ecosystem workshopOn 12-15 July 2008, a scientific workshop was held in Jupiter, Florida, to identify critical research and resource management needs for mesophotic coral ecosystems

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Dense saline plumes in Exuma Sound, Bahamas

Cited by 39 publications

References 19 publications

The effect of bottom substrate on inherent optical properties: Evidence of biogeochemical processes

The effect of bottom substrate on inherent optical properties: Evidence of biogeochemical processes

Possible refugia for reefs in times of environmental stress

Theme section on “Mesophotic Coral Ecosystems: Characterization, Ecology, and Management”

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