1,721,085 research outputs found
Two centuries of sponges (phylum Porifera) taxonomic studies in Indonesia (1820-2021): checklist and bibliography
No full textPutra, Singgih Afifa, Ambo-Rappe, Rohani, Jompa, Jamaluddin, De, Nicole J. (2023): Two centuries of sponges (phylum Porifera) taxonomic studies in Indonesia (1820-2021): checklist and bibliography. Zootaxa 5298 (1): 1-74, DOI: 10.11646/zootaxa.5298.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5298.1.
Late Holocene (0–6 ka) sea-level changes in the Makassar Strait, Indonesia
Full text linkThe Spermonde Archipelago, off the coast of southwest Sulawesi, consists of more than 100 small islands and hundreds of shallow-water reef areas. Most of the islands are bordered by coral reefs that grew in the past in response to paleo relative sea-level changes. Remnants of these reefs are preserved today in the form of fossil microatolls. In this study, we report the elevation, age, and paleo relative sea-level estimates derived from fossil microatolls surveyed in five islands of the Spermonde Archipelago. We describe 24 new sea-level index points, and we compare our dataset with both previously published proxies and with relative sea-level predictions from a set of 54 glacial isostatic adjustment (GIA) models, using different assumptions on both ice melting histories and mantle structure and viscosity. We use our new data and models to discuss Late Holocene (0–6 ka) relative sea-level changes in our study area and their implications in terms of modern relative sea-level estimates in the broader South and Southeast Asia region
Interactions between macroalgae and scleractinian corals in the context of reef degradation
Full text linkCompetition between hard corals and macroalgae is important to the overall status of coral reefs, especially during reef degradation which often involves a "phase shift" from coral to algal dominated reefs. Declining levels of herbivory due to over-fishing (the "top-down" model), or increasing supply of nutrients (eutrophication, the "bottom-up" model) have both been suggested to cause increased algal abundance and consequent competitive overgrowth of corals. Despite the importance of coral-algal competition to either of these models, there is little direct evidence demonstrating competition with algae as the cause of coral declines, and in particular, very little evidence unambiguously demonstrating shifts in competitive balance due to either reduced herbivory or increased nutrient supply. This thesis aims to provide more experimental evidence on the processes, mechanisms and outcomes of the interactions between corals and algae for (i) a range of levels, from individual to community; (ii) a range of algal taxa and functional groups; and (iii) ranges of ecological factors such as water quality or nutrients and herbivory.
The first study compared the effects of a turfing, filamentous red alga, Anotrichium tenue, and general mixed, filamentous algal turfs, on massive Porites corals. Comparisons of plots with A. tenue present, A. tenue experimentally removed, and with mixed turfs only present, indicated that A. tenue was able to overgrow and kill healthy coral, whereas mixed algal turfs could not. These contrasting effects demonstrate the potential variability in coral-algal competitive effects and outcomes, even within a functional group.
I further explored this variability using three different algal species; the turfing, filamentous red alga Corallophila huysmansii, the non-turfing, large green filamentous alga Chlorodesmis spp., and the corticated red alga Hypnea pannosa. Experimental tests again indicate considerable variation in the effects on corals, with C. huysmansii causing considerable coral tissue mortality, whereas neither Chlorodesmis nor H. pannosa had major effects on the corals.
To explore how herbivory may affect coral-algal competitive outcomes, I examined the interaction between the creeping foliose brown alga, Lobophora variegata, and the branching coral, Porites cylindrica, under natural and experimentally reduced levels of herbivory. These experiments used exclusion cages to test for effects of herbivores, and removal of algae or coral tissue, at their interaction boundary, to test for competitive inhibition of each competitor by the other. The results showed that overgrowth of the alga caused significant coral tissue mortality, but that the coral also inhibited algal growth. Nonetheless, the algae were markedly superior competitors. Importantly, reduced herbivory resulted in faster algal (net) growth and consequent overgrowth and mortality of coral tissue, demonstrating the critical importance of herbivory to the outcome of the competitive interaction.
This approach was extended to apply simultaneous, factorial tests of the effects of herbivores, nutrients and algal competitor on the coral. Coral tissue mortality was strongly enhanced by the presence of the algal competitor and this effect was significantly higher when herbivores were excluded. Addition of nutrients had no significant effect on corals overall, but had a small effect on algal growth and consequent coral tissue mortality when herbivores were excluded. The factorial design of this experiment not only provides the first direct comparisons of the strength of all 3 main effects, but also explores the interactions between those effects, and hence the processes involved. Importantly, whilst algal abundance and hence competitive impact were affected by herbivore consumption at all levels of nutrient supply, nutrient supply did not influence algal abundance except when consumption by herbivores was reduced.
Inshore reefs of the Great Barrier Reef commonly have extensive beds of large brown macroalgae (seaweeds) such as Sargassum spp., that are widely assumed to have negative impacts on coral populations. To test this assumption, I compared coral performance in large (5 x 5 m) plots in which the macroalgal canopy was removed, with that in control plots with intact algal canopies. In one study, the macroalgae had a negative impact on corals, reducing their recruitment, growth and survival. However, a second study showed a surprising increase in coral bleaching in plots from which the Sargassum canopy had been experimentally removed. Combined bleaching and recovery results suggest that coral bleaching-related mortality was higher in the removal plots. Thus the protection from bleaching provided by the Sargassum canopy may benefit long-term coral populations, as well as competing with them.
Comparison of competitive outcomes involving different algal types and functional groups, and under different herbivory and nutrient levels suggests three general conclusions. Firstly, the outcomes of the interactions are variable depending on coral-algal taxa and/or group involved. Secondly, this variability is readily interpreted in terms of a limited number of mechanisms by which corals and algae can interact: direct overgrowth, shading, abrasion, chemical or allelopathic effects, pre-emption of space,and sloughing of epithelial or mucus layers. The potential importance of these mechanisms can in turn be interpreted in terms of a limited number of properties of the algal taxa involved. These properties, which include thallus size, structure, growth form, reproductive mechanisms, and allelochemical production, are largely, but not entirely, summarised by existing algal functional groups. Thirdly, the specific interactions between competition, herbivory and nutrient enhancement, in which nutrient effects depended on levels of herbivory, but not vice versa, suggest that "top-down" control appeared to over-ride "bottom-up" control of algal abundance and competitive impact. Given the central importance of coral-algal competition to the process of coral reef phase shifts, understanding the variability and complexity in that competition will have important implications for the prediction and consequences of such phase shifts
Monitoring and Assessment of Coral Reef in Spermonde Archipelago, South Sulawesi, Indonesia
Full text link Four coral reef sites were observed in Spermonde Archipelago, off Southwest Sulawesi, Indonesia The sites were located at different distances from the mainland: Kayangan reef ('affected' site) is the closest and Samalona, Barang Lompo, and Kapoposan ('comparison' sites) are successively farther from the mainland and Ujung Pandang city. Coral cover, number of species at 3m and 1Om depths, and coral growth rates (Porites lobata) were observed to describe coral conditions. Environmental parameters suspended particulate matter (SPM), resuspended sediment, salinity, clarity, chlorophyll a, phosphate, nitrate, ammonium and o15N values ofcoral tissue (P. lobata) were also investigated to assess possible 'stress' factors on the reefs. Average coral cover at the 'affected' site was very low (14 %), compared to the other sites: Samalona (44.3 %), B. Lompo {47.2 %) and Kapoposan {66.6 %). Also, the lowest total number ofspecies occurred at Kayangan (42 spp.), compared to the other sites: Samalona {62 spp.), B. Lompo {71·spp.) and Kapoposan (80 spp.) Environmental parameters indicated that sedimentation and eutrophication (sewage) were the main 'stress' factors at Kayangan reef: while human disturbances such as fish bombing. anchoring. coral collection, and other activities affected Samalona and B. Lompo more. High coral cover and number of species at Kapoposan reef indicated fewer 'stress' factors. Coral growth rates showed a different trend from coral cover and total number of species. The highest coral growth rates occurred at B. Lompo (15.9 ± 0.8 mm yr-1) followed by Kayangan, Samalona and Kapoposan. Based on environmental parameters, it seemed that coral growth rates were higher at more eutrophic reefs, but slower at certain maximum critical nutrient values. δ^15 values of coral tissue found in this study are positively correlated with chlorophyll a, dissolved nutrients, and sedimentation rates. The high δ^(15)N values at Kayangan (8.03 ± 0.62 %) support the idea that this site was affected by human
waste and sewage. ThesisMaster of Science (MSc
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
TINGKAH LAKU MEMIJAH KARANG Acropora nobilis DAN Pocillopora verrucosa DI TERUMBU KARANG TROPIK PULAU BARRANGLOMPO, MAKASSAR
Full text linkArtikel ini sdh diterbitkan di Jurnal Torani Vol 15 edisi Desember 2005Some studies have explored coral sexual reproduction behaviour, but not such studies being reported from Indonesia. This research was intended to investigate the spawning behaviour of Acropora nobilis and Pocillopora verrucosa at Barranglompo Island, Makassar. Divings were made at night to record spawning behaviour directly (in situ observation) through one moon cycle. The results showed that both species were known as simultaneously hermaphrodite spawners, however they performed different spawning behaviour. A. nobilis released its gametes in one package of egg-sperm bundles, whereas P. verrucosa released freely and separately between eggs and sperms in 3 patterns: (i) polyp which solely released sperms; (ii) polyp which solely released eggs; and (iii) polyp which released both sperms and eggs
- …
