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Observation of Coral Reef and Macroalgae Competition in the Sempu Strait, Malang

Isdianto Andik, Kurniawan Andi, Wicaksono Agus Dwi, Marhaendra Quanta Nur Ihza, Putri Berlania Mahardika, Fathah Aulia Lanudia, Asadi Muhammad Arif, Luthfi Oktiyas Muzaky, Pratiwi Dwi Candra, Harahab Nuddin

Journal of Ecological Engineering

2023

Vol. 24, nr 10

174--184

Competition for space between coral reefs and macroalgae has a significant impact on coral cover and, consequently, on the sustainability of coastal ecosystems. This study aimed to ascertain the Sempu Strait’s substrate coverage, dominant coral reef lifeform, coral-macroalgae competition, and water quality. The Underwater Photo Transect method and the CPCe software are used to monitor coral reefs. The condition of the approximately 11.5% of living corals was deemed to be substandard. The western portion of the Sempu Strait is dominated by encrusting, branching, and massive corals, whereas the eastern portion is dominated by Acropora corals. Temperature varied between 26 and 35 °C, salinity varied between 17 and 35 ppt, pH varied between 7 and 8, water clarity varied between 2.25 and 2.73 m, and dissolved oxygen varied between 6.28 and 6.71 mg/L. Competition between corals and macroalgae is observed at multiple stations, including Banyu Tawar, Waru-Waru, and WatuMeja. This phenomenon can be attributed to the presence of suitable substrates such as sand, rubble, and pebbles, as well as favorable seasonal conditions and water quality that promote the growth of macroalgae. Essentially, macroalgae grow more rapidly than corals, resulting in competition for growing space.

Temporal variations in coral reef health at a coastal industrial site on the Gulf of Aqaba, Red Sea

Al-Zibdah M.K., Damhoureyeh S.A., Badran M.I.

Oceanologia

2007

No. 49 (4)

565-578

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.

The Torrecilla Reef Complex (Early Kimmeridgian, N Spain): an example of tectonically forced regression

Benito M., Mas R.

Volumina Jurassica

2006

Vol. 4, no. 1

79-80

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.