Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 2

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  coral reef
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
EN
A detailed ecological study was conducted for three years (2001-03) on a 5 km stretch of well-developed coral reef facing an industrial site in the southernmost section of the Jordanian coast of the Gulf of Aqaba, Red Sea. The degree of modification associated with the prevailing ecological factors was assessed with respect to species diversity and abundance of the major groups of the macrobenthic community: corals, bivalves, hydrozoans, echinoderms, sponges and macroalgae. Three locations of two depths each - 6 and 12 m - were selected and surveyed using the visual census point-intercept method. The actual area of the survey covered about 2250 m2. Macrobenthic communities occurring close to the industrial jetty were characterized by low diversity and the obvious dominance of soft coral (16-30% cover). In the deep transects (12 m) hard coral cover was higher than that in the shallow transects (30-55%). Correlation analyses indicated that species richness increased with increasing distance from the industrial jetty. Species richness of other macrobenthos was also higher as depth increased. The results revealed that the distribution and abundance of coral, echinoderms, hydrozoans and macroalgae were correlated with the relative importance of bottom modification within the various locations in the entire study area. However, no distinct influence of location or depth on the identities of most macrobenthic species was indicated.
EN
Palaeontological, sedimentological, palaeoecological and/or depositional aspects of most Late Jurassic reefs, specifically coral reefs, have been studied in detail (e.g. see references in Flugel & Flugel-Kahler 1992; Leinfelder et al. 1996; Insalaco et al. 1997; Dupraz & Strasser 2002; among others), but only a few papers deal with their depositional architecture and response to tectonics and/or sea-level change. For example, Leinfelder et al. (1994, 1996) conclude that both eustatic and tectonic changes were important in controlling platform geometry and evolutionary trends in Upper Jurassic reefs. The Early Kimmeridgian Torrecilla Reef Complex in the northern Iberian Basin of Spain consists of a fringing reef composed of eight accretionary units (Alonso et al. 1986-1987;Mas et al. 1997; Benito & Mas 2002, 2006). The first four were deposited along a steep margin. They display down-lapping and off-lapping geometries, and are characterized by poor reef-framework development, large volumes of reworked corals and transported sediment, and limited growth of micro-encrusters.In contrast, deposition of the fifth and younger accretionary units occurred on a shallow platform without a pronounced slope where coral reefs grew in a shallow protected environment (Benito & Mas 2006). The main features of these reefs are: an absence of reef-slope facies, a high proportion of preserved framework elements, relatively low volumes of intrareef sediment, high proportions of terrigenous material, and abundant micro-encrusters and microbialites. These reefs were protected from storm waves by long-shore sand bars, which also protected a very shallow lagoon during the last stage of sedimentation. The Early Kimmeridgian was a period of rising global sea level (Haq et al. 1988; Hallam 2001), a trend apparent across other portions of the Iberian Basin. However, geometry and sedimentary evolution of the Torrecilla Reef Complex is consistent with those of off-lapping reefs that develop during sea-level fall. Thus, we conclude that down-stepping geometries and evolution to progressively shallower environments within the Torrecilla Reef Complex occurred as a result of a tectonically forced regression.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.