Showing papers on "Turbinaria ornata published in 1999"
TL;DR: The different responses to nutrient pulses of macroalgal species with different life cycles and distributional ranges provide important information for the prediction of the response of whole inshore reef communities.
Abstract: Inshore coral reefs of the Great Barrier Reef, Australia, are subjected to episodic nutrient inputs, mainly by rain and riverine run-off during the summer wet season. Increased nutrient availability, potentially caused by human activity, is assumed to enhance the production of primary producers. To simulate increased nutrient inputs, 6 species of coral reef macroalgae were treated with short-term (24 h) nutrient pulses of 10 μM ammonium and/or 1 μM phosphate. Sargassum baccularia, an inshore perennial algae, had a ∼50% higher net photosynthetic rate and ∼40% higher tissue nutrients after nutrient addition. The net photosynthetic rates of the inshore, ephemeral species Chnoospora implexa, Hydroclathrus clathratus, and Padina tenuis increased by ∼30 to 50% and the tissue nutrient levels by 10 to 20% after a single nutrient pulse. Two perennial species, Chlorodesmis fastigiata and Turbinaria ornata, which occur inshore as well as on reefs further offshore, did not respond to nutrient addition with higher production, however, accumulated 15 to 20% more tissue nutrients than untreated thalli. The different responses to nutrient pulses of macroalgal species with different life cycles and distributional ranges provide important information for the prediction of the response of whole inshore reef communities.
81 citations
TL;DR: The populations of both species settled on the fringing reef and outer biogenic ridge, two physically and chemically unstable areas, exhibited a high sexual reproduction, whereas it was lower on the inner barrier reef.
Abstract: Abstract In terms of widespread distribution and high population density Turbinaria ornata and Sargassum mangarevense are the most conspicuous organisms settled on the reefs in Tahiti and other high islands of French Polynesia. This study reports on quantitative investigations of the temporal and spatial patterns displayed by these two species. It was carried out at three different sites on Tahiti Island. Data dealing with density, maturity, size structure of the mature population, sex-distribution and fertility were collected over 16 months between November 1994 and February 1996. Turbinaria ornata and Sargassum mangarevense populations settle on the reef throughout the year with a peak in density during the cool season. A density gradient from the fringing reef to the outer biogenic ridge was evident. A peak in maturity and fertility was observed during the warm season. A dwarfism of thallus length was noticed in Turbinaria ornata on the outer biogenic ridge whereas it was not observed in Sargassum mangarevense. The populations of both species settled on the fringing reef and outer biogenic ridge, two physically and chemically unstable areas, exhibited a high sexual reproduction, whereas it was lower on the inner barrier reef. Whatever the area considered the period of reproduction of these two species extended throughout the whole year. The data collected during this study were used to explain the colonization of different habitats by these two species.
80 citations
TL;DR: It is proposed that the tendency for fertile thalli of T. ornata to float over long distances, combined with its oogonia stock and higher settlement efficiencies, could account for its greater capacity to colonize new areas, as compared to S. mangarevense.
Abstract: Turbinaria ornata and Sargassum mangarevense are the most conspicuous macroalgal species that grow on the reefs of Tahiti and other high islands of French Polynesia. This study reports on a quantitative investigation of spatial and seasonal settlement efficiencies and dispersal distances for these 2 species in a coral reef habitat on Tahiti. Settlement patterns of germlings were observed in situ on settlement plates placed around parental thalli during 2 seasons (hot and cold). For both species, the dispersal of germlings was limited to within 90 cm of the parental thalli, and the greatest number of settled germlings was observed during the cold season. T. ornata showed a higher attachment ability and lower dispersal distances than S. mangarevense. A model of dispersal is suggested for the 2 species showing a decrease in germling number with distance from parental thalli. Dispersal of germlings appears to be influenced by the dominant current during their release. This short-distance dispersal allows rapid establishment and maintenance of local populations, and is consistent with the explanation of the metapopulation distribution of the 2 species. The 2 species did not release all oogonia present in their reproductive structures. T. ornata had a stock of oogonia that varied seasonally (with low amounts during the hot season), whereas there was no seasonal variation in the oogonia stock of S. mangarevense. Recently, isolated atolls have been settled by T ornata but not by S. mangarevense. It is proposed that the tendency for fertile thalli of T. ornata to float over long distances, combined with its oogonia stock and higher settlement efficiencies, could account for its greater capacity to colonize new areas, as compared to S. mangarevense.
76 citations