Monismith S.G.,Stanford University |
Davis K.A.,Stanford University |
Davis K.A.,Woods Hole Oceanographic Institution |
Shellenbarger G.G.,Stanford University |
And 16 more authors.
Limnology and Oceanography | Year: 2010
We present measurements of flows and fluxes of phytoplankton to Conch Reef, Florida, a Caribbean reef dominated by sponges and soft corals, located in 15 m of water offshore of Key Largo. Vertical profiles of chlorophyll a, a proxy for phytoplankton biomass, showed a near-bed depletion, indicating the existence of concentration boundary layers. Along with simultaneous measurements of velocity profiles, near-bed turbulence, and temperature stratification, these profiles were used to compute α, the mass transfer velocity of phytoplankton to the bed (i.e., the flux to the bed normalized by near-bed concentration). The a value ranged from-40 to +130 m d-1, with a significant linear positive relationship with shear velocity. The median value of a = 48 ± 20 m d-1 is larger than would be expected, given the observed population of filter-feeding sponges. Nonetheless, these large values of α are consistent with values found recently for another coral reef as well as for a soft bottom estuarine community. Taken as a whole, these measurements indicate that reefs with large roughness and/or energetic currents should be able to support higher biomasses of benthic organisms than would low relief reefs or reefs in sluggish waters. © 2010, by the American Society of Limnology and Oceanography, Inc.
Torfstein A.,Lamont Doherty Earth Observatory |
Torfstein A.,Hebrew University of Jerusalem |
Torfstein A.,Interuniversity Institute of Marine science |
Goldstein S.L.,Lamont Doherty Earth Observatory |
And 5 more authors.
Earth and Planetary Science Letters | Year: 2015
Sediment cores recovered by the Dead Sea Deep Drilling Project (DSDDP) from the deepest basin of the hypersaline, terminal Dead Sea (lake floor at ~725 m below mean sea level) reveal the detailed climate history of the lake's watershed during the last interglacial period (Marine Isotope Stage 5; MIS5). The results document both a more intense aridity during MIS5 than during the Holocene, and the moderating impacts derived from the intense MIS5e African Monsoon. Early MIS5e (~133-128 ka) was dominated by hyperarid conditions in the Eastern Mediterranean-Levant, indicated by thick halite deposition triggered by a lake-level drop. Halite deposition was interrupted however, during the MIS5e peak (~128-122 ka) by sequences of flood deposits, which are coeval with the timing of the intense precession-forced African monsoon that generated Mediterranean sapropel S5. A subsequent weakening of this humidity source triggered extreme aridity in the Dead Sea watershed and resulting in the biggest known lake level drawdown in its history, reflected by the deposition of thick salt layers, and a capping pebble layer corresponding to a hiatus at ~116-110 ka. The DSDDP core provides the first evidence for a direct association of the African monsoon with mid subtropical latitude climate systems effecting the Dead Sea watershed. Combined with coeval deposition of Arabia and southern Negev speleothems, Arava travertines, and calcification of Red Sea corals, the evidence points to a climatically wet corridor that could have facilitated homo sapiens migration "out of Africa" during the MIS5e peak. The hyperaridity documented during MIS5e may provide an important analogue for future warming of arid regions of the Eastern Mediterranean-Levant. © 2014 Elsevier B.V.All rights reserved.
Dishon G.,Bar - Ilan University |
Dishon G.,Interuniversity Institute of Marine science |
Dubinsky Z.,Bar - Ilan University |
Caras T.,Ben - Gurion University of the Negev |
And 5 more authors.
International Journal of Remote Sensing | Year: 2012
Solar light penetrates deep into the clear water of oligotrophic oceans and may have both beneficial and destructive effects on marine phytoplankton. In oligotrophic waters worldwide, phytoplankton communities consist mostly of ultraphytoplankton of the groups Synechococcus and Prochlorococcus, which differ in their optical properties and, therefore, are better suited for thriving in different niches along the natural vertical light gradient. In this article, we aim to draw the optical boundaries separating the two populations in order to get a better insight into the light-driven dynamics in ultraphytoplankton-community structure and to predict future trends. We report spectral, photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) penetration through the stratified season along with temporal and vertical distributions of Synechococcus and Prochlorococcus in the Gulf of Eilat (Aqaba). These light-field parameters are used to define the apparent limits of the vertical distribution of Synechococcus and Prochlorococcus throughout the water column. Furthermore, we formulate the necessary empirical algorithms, allowing for characterization of the optical habitats defined in this study by remote-sensed or in situ radiometric measurements. © 2012 Taylor and Francis Group, LLC.
Shwartsberg M.,Interuniversity Institute of Marine science |
Shwartsberg M.,Bar - Ilan University |
Kizner Z.,Bar - Ilan University |
Dubinsky Z.,Bar - Ilan University |
Bachar A.,Ben - Gurion University of the Negev
Israel Journal of Ecology and Evolution | Year: 2012
Morphological and physiological phenotypic plasticity of Stylophora pistillata in response to environmental changes was studied, with the objective of evaluating the impact of light and water flow as environmental factors. An in-situ artificial manipulation of combined light intensity and water flow was conducted, and the responses of several colonies were followed, over a period of nine months, documenting changes in colony architecture and zooxanthellae attributes. The results suggest the existence of a light threshold level, above which light is sufficient for fulfilling the association's energy needs and below which water flow becomes more crucial for attaining resources. S. pistillata exhibited phenotypic plasticity, with a strong dependence on light intensity. A conceptual model explaining the main patterns of morphological change in response to different combinations of the two factors is proposed. The suggested model is based on the idea that morphology is not intended to serve as an a priori optimizer of the hermatypic organism's performance in a given environment, but rather reflects an a posteriori response of the symbiotic association's architecture, mediated by its physiological response, to availability of resources and their gradients.
Byler K.A.,University of Mississippi |
Carmi-Veal M.,Interuniversity Institute of Marine science |
Fine M.,Interuniversity Institute of Marine science |
Fine M.,Bar - Ilan University |
Goulet T.L.,University of Mississippi
PLoS ONE | Year: 2013
In obligate symbioses, the host's survival relies on the successful acquisition and maintenance of symbionts. Symbionts can either be transferred from parent to offspring via direct inheritance (vertical transmission) or acquired anew each generation from the environment (horizontal transmission). With vertical symbiont transmission, progeny benefit by not having to search for their obligate symbionts, and, with symbiont inheritance, a mechanism exists for perpetuating advantageous symbionts. But, if the progeny encounter an environment that differs from that of their parent, they may be disadvantaged if the inherited symbionts prove suboptimal. Conversely, while in horizontal symbiont acquisition host survival hinges on an unpredictable symbiont source, an individual host may acquire genetically diverse symbionts well suited to any given environment. In horizontal acquisition, however, a potentially advantageous symbiont will not be transmitted to subsequent generations. Adaptation in obligate symbioses may require mechanisms for both novel symbiont acquisition and symbiont inheritance. Using denaturing-gradient gel electrophoresis and real-time PCR, we identified the dinoflagellate symbionts (genus Symbiodinium) hosted by the Red Sea coral Stylophora pistillata throughout its ontogenesis and over depth. We present evidence that S. pistillata juvenile colonies may utilize both vertical and horizontal symbiont acquisition strategies. By releasing progeny with maternally derived symbionts, that are also capable of subsequent horizontal symbiont acquisition, coral colonies may acquire physiologically advantageous novel symbionts that are then perpetuated via vertical transmission to subsequent generations. With symbiont inheritance, natural selection can act upon the symbiotic variability, providing a mechanism for coral adaptation. © 2013 Byler et al.