Characteristics of oceanographic processes on reefs of the Seychelles Islands

Novozhilov, A. V.; Chernova, Y. N.; Tsukurov, I. A.; Denisov, V. A.; Propp, L. N.

doi:10.5479/si.00775630.366.1

Cited by 9 publications

(7 citation statements)

References 7 publications

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“…These observations are consistent with prior observations of the vertical and horizontal movement of cool, subsurface water masses at the Florida site (Leichter et al, 2003;Leichter et al, 1996), but represent, to our knowledge, the first report of similar forcing at the regional scale of the Caribbean and Bahamas. Similar processes have been described for the outer margin of the Great Barrier Reef (Wolanski and Pickard, 1983), Tahiti (Wolanski and Delesalle, 1995), and the Seychelles Islands (Novozhilov et al, 1992). In temperate coastal systems in Southern California and Oregon internal waves have also been linked to onshore transport of surface warm fronts (Pineda, 1999;Shanks and McCulloch, 2003), and this may be a consequence of internal wave impacts on reefs as well.…”

Section: B Mechanisms Of High Frequency Thermal Variabilitymentioning

confidence: 74%

Variation beneath the surface: Quantifying complex thermal environments on coral reefs in the Caribbean, Bahamas and Florida

Leichter¹,

Helmuth²,

Fischer³

2006

J Mar Res

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Analysis of in situ temperature records collected on six coral reefs in the Caribbean, Bahamas, and Florida Keys reveal significant variability across a range of temporal and spatial scales from minutes to seasons, across depths, and among sites. Subsurface variability occurring at daily and faster frequencies is prevalent across the region, likely driven by combinations of diurnal heating and cooling, wind driven advection, and internal waves at tidal and faster frequencies. This high frequency variability is not detected in records of remotely-sensed sea surface temperature alone. Diurnal variability likely caused by diurnal solar heating and cooling and possibly by advection associated with diurnal winds (daily sea breeze) was significant at all sites and showed greatest magnitude of variation at shallowest depths. Temperature fluctuations at tidal and faster frequencies were common at 5 out of the 6 sites. The magnitude of this variability is not well explained by measured vertical temperature stratification combined with oscillations of the water column associated with barotropic surface tides. Rather, the magnitude and nature of the temperature changes point to the presence of internal waves generated at tidal and faster frequencies. Power spectra calculated seasonally show greatest variability within both diurnal and semi-diurnal frequency bands in Spring and Summer at Florida, Bahamas, Jamaica, and St. Croix. Variability within the semi-diurnal frequency band at Belize and Bonaire was greatest in Winter. Warming in Summer estimated as degree-hours per day above 29.0°C increased with increasing latitude and varied significantly among sites and depths in a manner not predictable from remotely sensed SST data alone. Site latitude was directly related to the amplitude of the seasonal thermal variability, but was not tightly related to variability at daily and faster frequencies which was greatest at the highest and lowest latitude sites. The interactions of depth, site, and season across the study region are associated with distinct signals of thermal variability, and have significant implications for the physiology and ecology of corals and other reef organisms.

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Section: B Mechanisms Of High Frequency Thermal Variabilitymentioning

confidence: 74%

Variation beneath the surface: Quantifying complex thermal environments on coral reefs in the Caribbean, Bahamas and Florida

Leichter¹,

Helmuth²,

Fischer³

2006

J Mar Res

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“…Sampling locations were stratified by habitat (fore reef, patch reefs) and wave exposure (windward, leeward, upwelling) and located haphazard within each stratum. The upwelling habitat type was inferred from past studies and datasets that show upwelling on the southern boundary of the atoll and surrounding bank [12] that match local knowledge (R. Aumeeruddy personal observations), and is differentiated from both windward and leeward reef exposures. A total of 33 sites were visited with comprehensive benthic and fish surveys conducted at 30 of these sites between 15 and 27 February 2009.…”

Section: Methodsmentioning

confidence: 99%

Coexistence of Low Coral Cover and High Fish Biomass at Farquhar Atoll, Seychelles

et al. 2014

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We report a reef ecosystem where corals may have lost their role as major reef engineering species but fish biomass and assemblage structure is comparable to unfished reefs elsewhere around the world. This scenario is based on an extensive assessment of the coral reefs of Farquhar Atoll, the most southern of the Seychelles Islands. Coral cover and overall benthic community condition at Farquhar was poor, likely due to a combination of limited habitat, localized upwelling, past coral bleaching, and cyclones. Farquhar Atoll harbors a relatively intact reef fish assemblage with very large biomass (3.2 t ha−1) reflecting natural ecological processes that are not influenced by fishing or other local anthropogenic factors. The most striking feature of the reef fish assemblage is the dominance by large groupers, snappers, and jacks with large (>1 m) potato cod (Epinephelus tukula) and marbled grouper (E. polyphekadion), commonly observed at many locations. Napoleon wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum) are listed as endangered and vulnerable, respectively, but were frequently encountered at Farquhar. The high abundance and large sizes of parrotfishes at Farquhar also appears to regulate macroalgal abundance and enhance the dominance of crustose corallines, which are a necessary condition for maintenance of healthy reef communities. Overall fish biomass and biomass of large predators at Farquhar are substantially higher than other areas within the Seychelles, and are some of the highest recorded in the Indian Ocean. Remote islands like Farquhar Atoll with low human populations and limited fishing pressure offer ideal opportunities for understanding whether reefs can be resilient from global threats if local threats are minimized.

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“…Orthophosphate levels followed the same trend with the lowest total inorganic phosphorus at St. Joseph Atoll (0.11 pM) followed by Cerf Island (0.12), Victoria Harbor (0.22) and Pagode Island (with the highest value of 0.50 M). Novozhilov et al (1992) also noted that the waters of Victoria Harbor and near the bird rookeries of Cosmoledo Atoll contain elevated levels of nutrients which they likewise attributed to sewage discharges and bird excrements, respectively. Our photosynthetic assays coincide closely with the predicted trends in nutrient levels and are consistent with the hypothesis that macroalgae from enriched waters differ in their relative levels of nutrient limitation from species growing in nutrient-poor habitats.…”

Section: : !mentioning

confidence: 97%

Photosynthesis vs. irradiance curves for six species of macroalgae from the Seychelles Islands under four levels of nutrient enrichment

Littler¹,

Littler²

1992

Atoll Research Bulletin

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The relative nutritional status, with respect to phosphorus (P) versus nitrogen (N) limitation, and light-limited photosynthesis (Ps) was examined over a broad range of quantum fluxes (I) for four species of Chlorophyta (Codium sp., Avrainvillea amadelpha f. montagnei, Dicfyosphaeria cavemosa, Udotea orientalis and two species of Rhodophyta (Gracilaria crassa, G, multifurcata) taken from Seychelles coastal waters. The results are consistent with the hypothesis that differences in nutrient status among algal forms are related to antecendent habitat history. Maximum photosynthetic rates (Pmax) for Codium sp., U. orientalis and G. multifurcata from nutrient-poor habitats increased (Pc0.05) following nutrient enrichment. However, the species examined from nutrient-rich waters, A. amadelpha f. montagnei, D. cavemosa and G. crassa, showed decreases in the initial slope (a) of the P vs.

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Characteristics of oceanographic processes on reefs of the Seychelles Islands

Cited by 9 publications

References 7 publications

Variation beneath the surface: Quantifying complex thermal environments on coral reefs in the Caribbean, Bahamas and Florida

Variation beneath the surface: Quantifying complex thermal environments on coral reefs in the Caribbean, Bahamas and Florida

Coexistence of Low Coral Cover and High Fish Biomass at Farquhar Atoll, Seychelles

Photosynthesis vs. irradiance curves for six species of macroalgae from the Seychelles Islands under four levels of nutrient enrichment

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