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Dunckley J.F.,Stanford University | Koseff J.R.,Stanford University | Steinbuck J.V.,Harvard University | Monismith S.G.,Stanford University | Genin A.,Interuniversity Institute for Marine Science
Journal of Geophysical Research: Oceans | Year: 2012

Due to the many difficulties associated with measuring buoyancy flux directly in the field, parameterizations for the flux involving eddy diffusivities are commonly used. These parameterizations are often cast in terms of a mixing efficiency (), which itself is often assumed to be a constant throughout the water column (0.17-0.2). Alternatively, can be calculated in terms of turbulence parameters which attempt to capture the varying mixing dynamics throughout the water column. In this paper three separate parameterizations are used to calculate the eddy diffusivities in a dynamically evolving stratified water column in the Gulf of Aqaba. Furthermore, we use two different approaches for calculating by Ivey and Imberger (1991) and Shih et al. (2005) for these diffusivity parameterizations and compare the results obtained using each approach. Further work on the Shih et al. (2005) parameterization by D. Bouffard and L. Boegman (personal communication, 2011) has also been used in this analysis. While direct measurements of buoyancy flux are needed to validate the actual accuracy of the mixing efficiency parameterizations, we can make the following conclusions. First, we found that in some circumstances the eddy diffusivity models produce very different estimates from one another and the estimates are themselves sensitive to the choice of parameterization for . Second, when the stratification is weak and temperature variance is small, parameterizations involving calculations of the Thorpe scale, T as well as the turbulent Froude number and Reynolds numbers should be treated with great caution. Third, under the same circumstances, the Shih et al. (2005) approach for applied to the parameterization for vertical diffusivity seems to be the best vertical diffusivity (based on a comparison to ). © 2012. American Geophysical Union. All Rights Reserved.

Polak O.,Ben - Gurion University of the Negev | Polak O.,Interuniversity Institute for Marine Science | Shashar N.,Ben - Gurion University of the Negev
ICES Journal of Marine Science | Year: 2013

Polak, O., and Shashar, N. 2013. Economic value of biological attributes of artificial coral reefs - ICES Journal of Marine Science, 70: 904-912.Visitor appreciation of natural scenes such as coral reefs is well documented. However, what part the value of the biological component in these scenes plays in fostering people's enjoyment is unclear. Using the contingent valuation method (CVM), we examined divers' willingness to pay for changes in the fish and coral attributes over an artificial reef. Using image manipulations, different levels of community descriptors, such as richness, abundance, and biodiversity of corals and fish, were isolated, and the willingness to pay for proposed factors was examined. The results showed that divers were willing to contribute towards all increases in reef community attributes, and were partially able to discriminate between them. Biodiversity was the most valued index, while fish abundance was the least favoured. These results, which demonstrate that visitors understand the fundamentals that constitute a coral reef community and value its diversity, may help direct conservation efforts undertaken in the design of marine reserves and pre-planned artificial reefs. © 2013 International Council for the Exploration of the Sea.

Holzman R.,Tel Aviv University | Holzman R.,Interuniversity Institute for Marine Science | Collar D.C.,University of California at Santa Cruz | Price S.A.,University of California at Davis | And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

Morphological diversification does not proceed evenly across the organism. Some body parts tend to evolve at higher rates than others, and these rate biases are often attributed to sexual and natural selection or to genetic constraints. We hypothesized that variation in the rates of morphological evolution among body parts could also be related to the performance consequences of the functional systems that make up the body. Specifically, we tested the widely held expectation that the rate of evolution for a trait is negatively correlated with the strength of biomechanical trade-offs to which it is exposed. We quantified the magnitude of trade-offs acting on the morphological components of three feeding-related functional systems in four radiations of teleost fishes. After accounting for differences in the rates of morphological evolution between radiations, we found that traits that contribute more to performance trade-offs tend to evolve more rapidly, contrary to the prediction. While ecological and genetic factors are known to have strong effects on rates of phenotypic evolution, this study highlights the role of the biomechanical architecture of functional systems in biasing the rates and direction of trait evolution. © 2011 The Royal Society.

Chindapol N.,University of Amsterdam | Kaandorp J.A.,University of Amsterdam | Cronemberger C.,University of Amsterdam | Mass T.,Rutgers University | And 2 more authors.
PLoS Computational Biology | Year: 2013

The growth of scleractinian corals is strongly influenced by the effect of water motion. Corals are known to have a high level of phenotypic variation and exhibit a diverse range of growth forms, which often contain a high level of geometric complexity. Due to their complex shape, simulation models represent an important option to complement experimental studies of growth and flow. In this work, we analyzed the impact of flow on coral's morphology by an accretive growth model coupled with advection-diffusion equations. We performed simulations under no-flow and uni-directional flow setup with the Reynolds number constant. The relevant importance of diffusion to advection was investigated by varying the diffusion coefficient, rather than the flow speed in Péclet number. The flow and transport equations were coupled and solved using COMSOL Multiphysics. We then compared the simulated morphologies with a series of Computed Tomography (CT) scans of scleractinian corals Pocillopora verrucosa exposed to various flow conditions in the in situ controlled flume setup. As a result, we found a similar trend associated with the increasing Péclet for both simulated forms and in situ corals; that is uni-directional current tends to facilitate asymmetrical growth response resulting in colonies with branches predominantly developed in the upstream direction. A closer look at the morphological traits yielded an interesting property about colony symmetry and plasticity induced by uni-directional flow. Both simulated and in situ corals exhibit a tendency where the degree of symmetry decreases and compactification increases in conjunction with the augmented Péclet thus indicates the significant importance of hydrodynamics. © 2013 Chindapol et al.

Foran E.,Interuniversity Institute for Marine Science | Foran E.,Bar - Ilan University | Weiner S.,Weizmann Institute of Science | Fine M.,Interuniversity Institute for Marine Science | Fine M.,Bar - Ilan University
Scientific Reports | Year: 2013

The main source of calcium carbonate (CaCO3) in the ocean comes from the shells of calcifying planktonic organisms, but substantial amounts of CaCO3 are also produced in fish intestines. The precipitation of CaCO3 assists fish in intestinal water absorption and aids in whole body Ca2+ homeostasis. Here we report that the product formed in the intestinal lumen of the gilt-head seabream, Sparus aurata, is an amorphous calcium carbonate (ACC) phase. With FTIR spectroscopy and SEM imaging, our study shows that the fish-derived carbonates from S. aurata are maintained as a stable amorphous phase throughout the intestinal tract. Moreover, intestinal deposits contained up to 54 mol% Mg2+, the highest concentration yet reported in biogenic ACC. Mg is most likely responsible for stabilizing this inherently unstable mineral. The fish carbonates also displayed initial rapid dissolution when exposed to seawater, exhibiting a significant increase in carbonate concentration.

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