oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Ecological States and the Resilience of Coral Reefs  [cached]
Tim McClanahan,Nicholas Polunin,Terry Done
Ecology and Society , 2002,
Abstract: We review the evidence for multiple ecological states and the factors that create ecological resilience in coral reef ecosystems. There are natural differences among benthic communities along gradients of water temperature, light, nutrients, and organic matter associated with upwelling-downwelling and onshore-offshore systems. Along gradients from oligotrophy to eutrophy, plant-animal symbioses tend to decrease, and the abundance of algae and heterotrophic suspension feeders and the ratio of organic to inorganic carbon production tend to increase. Human influences such as fishing, increased organic matter and nutrients, sediments, warm water, and transportation of xenobiotics and diseases are common causes of a large number of recently reported ecological shifts. It is often the interaction of persistent and multiple synergistic disturbances that causes permanent ecological transitions, rather than the succession of individual short-term disturbances. For example, fishing can remove top-level predators, resulting in the ecological release of prey such as sea urchins and coral-eating invertebrates. When sea urchins are not common because of unsuitable habitat, recruitment limitations, and diseases, and when overfishing removes herbivorous fish, frondose brown algae can dominate. Terrigenous sediments carried onto reefs as a result of increased soil erosion largely promote the dominance of turf or articulated green algae. Elevated nutrients and organic matter can increase internal eroders of reef substratum and a mixture of filamentous algae. Local conservation actions that attempt to reduce fishing and terrestrial influences promote the high production of inorganic carbon that is necessary for reef growth. However, global climate change threatens to undermine such actions because of increased bleaching and mortality caused by warm-water anomalies, weakened coral skeletons caused by reduced aragonite availability in reef waters, and increased incidence of diseases in coral reef species. Consequently, many coral reefs, including those that are heavily managed, have experienced net losses in accumulated inorganic carbon in recent decades and appear likely to continue this trend in coming decades. Reefs urgently need to be managed with a view to strengthening their resilience to the increased frequency and intensity of these pressures. Ecological targets must include the restoration or maintenance of species diversity, keystone species, spatial heterogeneity, refugia, and connectivity. Achieving these goals will require unprecedented cooperative synergy betw
Ecosystem-Scale Effects of Nutrients and Fishing on Coral Reefs  [PDF]
Sheila M. Walsh
Journal of Marine Biology , 2011, DOI: 10.1155/2011/187248
Abstract: Nutrient pollution and fishing are the primary local causes of coral reef decline but their ecosystem-scale effects are poorly understood. Results from small-scale manipulative experiments of herbivores and nutrients suggest prioritizing management of fishing over nutrient pollution because herbivores can control macroalgae and turf in the presence of nutrients. However, ecological theory suggests that the opposite occurs at large scales. Moreover, it is unclear whether fishing decreases herbivores because fishing of predators may result in an increase in herbivores. To investigate this paradox, data on the fish and benthic communities, fishing, and nutrients were collected on Kiritimati, Kiribati. Oceanographic conditions and a population resettlement program created a natural experiment to compare sites with different levels of fishing and nutrients. Contrary to theory, herbivores controlled macroalgae in the presence of nutrients at large spatial scales, and herbivores had greater effects on macroalgae when nutrients were higher. In addition, fishing did not increase herbivores. These results suggest that protecting herbivores may have greater relative benefits than reducing nutrient pollution, especially on polluted reefs. Reallocating fishing effort from herbivores to invertivores or planktivores may be one way to protect herbivores and indirectly maintain coral dominance on reefs impacted by fishing and nutrient pollution. 1. Introduction Fishing [1–7] and nutrient pollution [8, 9] or both [10–14] are cited as the most important local causes of coral reef decline. It is difficult, however, to evaluate local fishing and nutrient effects independently because these factors are almost always confounded and large-scale experiments are infeasible. Results from theoretical and small-scale experimental studies (typically <1?m2, four from 50 to 250?m2 [14]) suggest prioritizing management of herbivore populations because herbivores can control the effect of nutrients on macroalgal and turf abundance and nutrient enrichment alone is not sufficient to cause a phase shift from coral to macroalgal and/or turf algal dominance [11, 14, 15]. In order to apply these results and implement ecosystem-based management, information is needed on (1) how fishing and nutrients interactively affect the fish and benthic communities, (2) the mechanisms by which fishing (rather than cages that exclude fish) and nutrients are linked to shifts to macroalgal and turf algal dominance, and (3) whether herbivores can control macroalgae and turf algae when nutrient enrichment
Local ecological knowledge on the goliath grouper epinephelus itajara (teleostei: serranidae) in southern Brazil
Gerhardinger, Leopoldo Cavaleri;Marenzi, Rosemeri Carvalho;Bertoncini, áthila Andrade;Medeiros, Rodrigo Pereira;Hostim-Silva, Maurício;
Neotropical Ichthyology , 2006, DOI: 10.1590/S1679-62252006000400008
Abstract: the goliath grouper epinephelus itajara is a large sized (> 400 kg) and critically endangered marine fish, which is protected in many countries, including brazil. through the application of semi-structured interviews, we investigated the local ecological knowledge of seven fishermen specialist on catching e. itajara from the babitonga bay, santa catarina, brazil. local long-line fisheries for e. itajara seemed to be a disappearing tradition in the studied site, with a detailed inherent local ecological knowledge system, which is also being lost. our study also showed that fishermen engaged in recent fisheries, such as spear-fishing, can also possess a detailed local ecological knowledge system. through the analysis of fishermen local ecological knowledge, several aspects of e. itajara life history were registered. this species is found in the inner and outer babitonga bay, from saline waters to areas with a large input of freshwater, and inhabits submerged wooden substrates and artificial reefs such as shipwrecks, mooring pillars and cargo containers. it is known to spawn in december and subsequent summer months in the studied area. spawning aggregations are usually seen in december (during full moon), being also eventually observed in january and february by our informants. while lobsters, spadefishes and octopuses seem to constitute the most important food items of inner bay e. itajara, outer bay individuals may feed on catfishes, crustaceans and other fish species. the goliath grouper is regarded as pacific and curious fish, but frequently display agonistic behavior in the presence of divers. based on the perception of well experienced spear fishermen, we hypothesize that e. itajara undertakes seasonal migrations from the inner to the outer bay during summer, and that the studied population is suffering from growth over-fishing. our data provides a practical evidence of how joining scientific and local ecological knowledge will likely benefit e. itajara local con
Modeling Fish Biomass Structure at Near Pristine Coral Reefs and Degradation by Fishing  [PDF]
Abhinav Singh,Hao Wang,Wendy Morrison,Howard Weiss
Quantitative Biology , 2008,
Abstract: Until recently, the only examples of inverted biomass pyramids have been in freshwater and marine planktonic communities. In 2002 and 2008 investigators documented inverted biomass pyramids for nearly pristine coral reef ecosystems within the NW Hawaiian islands and the Line Islands, where apex predator abundance comprises up to 85% of the fish biomass. We build a new refuge based predator-prey model to study the fish biomass structure at coral reefs and investigate the effect of fishing on biomass pyramids. Utilizing realistic life history parameters of coral reef fish, our model exhibits a stable inverted biomass pyramid. Since the predators and prey are not well mixed, our model does not incorporate homogeneous mixing and the inverted biomass pyramid is a consequence of the refuge. Understanding predator-prey dynamics in nearly pristine conditions provides a more realistic historical framework for comparison with fished reefs. Finally, we show that fishing transforms the inverted biomass pyramid to be bottom heavy.
Sucession of Fish Species in Artificial Reefs at a Coastal Island in Souh Brasillian Litoral Sucess o de espécies de peixes em recifes artificiais numa ilha costeira do litoral sul brasileiro
C. L. F. Jardeweski,Tito C. M. Almeida
Brazilian Journal of Aquatic Science and Technology , 2005,
Abstract: The utilization of artificial structures placed in marine bottom for fish attraction date of long time. In the last 10 years artificial reefs has been used in brazillian coast under several reasons, like: productivity enhancement, sub-aquatic tourism, fish trawling reduction, etc. However little information was known about the impacts of artificial reef, such positives than negatives, in the first semester of 2004 a law project, in Brazil, was approved liberating the practice by many ecological reasons. The present study was developed in Porto Belo Island, in the shore of Santa Catarina, Brazil. Six unities of ReefBall TM, in two blocks of three unities, were placed near the island. One block was placed near the island rocky shore (RD) and the other block 60 meters far from the rocky shore (RF). Fish visual censuses were done by SCUBA, monthly, since October of 2002 to September of 2003 in both sites. The pattern of species succession in each block was characterized by cumulated curves of species in the time long, and the curves calibrated by the minimum squares and the angular coefficient founded for each one of the sites compared by the Student Test. A Total of 23 species was identified for RD and 8 to RF. The increasing number of species, measured by the angular coefficient of each equation, was significant different (t cal(b1- b2) =4,474; p<<0,01) and superior in the block near the rocky shore (bRD=1,503; bRF=0,682). Different raising pattern in the species number could be verified when compare the both succession curves, RF showed two distinct pulses. In RD the raising number of species also was verified however this raise was more gradual and continual. The results indicated that the proximity to other natural subtract act directly on the colonization process by fishes in artificial structures. The utilization of artificial structures placed in marine bottom for fish attraction date of long time. In the last 10 years artificial reefs has been used in brazillian coast under several reasons, like: productivity enhancement, sub-aquatic tourism, fish trawling reduction, etc. However little information was known about the impacts of artificial reef, such positives than negatives, in the first semester of 2004 a law project, in Brazil, was approved liberating the practice by many ecological reasons. The present study was developed in Porto Belo Island, in the shore of Santa Catarina, Brazil. Six unities of ReefBall TM, in two blocks of three unities, were placed near the island. One block was placed near the island rocky shore (RD) and the other block 60
ASSESSING ECOLOGICAL RESILIENCE OF INDONESIAN CORAL REEFS  [cached]
Imam Bachtiar1,2, Ario Damar1, Suharsono3, Neviaty P. Zamani4
Journal of Coastal Development , 2011,
Abstract: Ecological resilience is an important property of natural ecosystem to be understood in coral reef management. Resilience of Indonesian coral reefs was assessed using 2009 COREMAP data. The assessment used 698 data of line intercept transects collected from 15 districts and 4 marine physiographies. Resilience index used in the assessment was developed by the authors but will be published elsewhere. The results showed that coral reefs at western region had higher average resilience indices than eastern region, and Sunda Shelf reefs had higher resilience indices than coral reefs at Indian Ocean, Sulawesi-Flores, or Sahul Shelf. Four districts were found to have coral reefs with highest resilience indices, i.e. Bintan and Natuna (western region), and Wakatobi and Buton (eastern region). Raja Ampat had coral reefs with lower average resilience indices than that of Wakatobi. Uses of resilience index in coral reef management should be coupled with other information such as maximum depth of coral communities.
Overview on artificial reefs in Europe
Fabi, Gianna;Spagnolo, Alessandra;Bellan-Santini, Denise;Charbonnel, Eric;?i?ek, Burak Ali;García, Juan J. Goutayer;Jensen, Antony C.;Kallianiotis, Argiris;Santos, Miguel Neves dos;
Brazilian Journal of Oceanography , 2011,
Abstract: artificial reefs in europe have been developed over the last 40 yrs. most of these reefs have been placed in the mediterranean sea, but there is an increasing interest on the part of northern european countries. fish stock enhancement and fishery management are the main purposes of reef construction in the mediterranean sea and on the atlantic coast of the iberian peninsula, while nature conservation/restoration, research, and recreation have been the main purposes served in the other european regions to date. artificial reef deployment falls under some general regulations concerning the protection of the sea against pollution due to the dumping of unsuitable materials. specific regional plans relating to the use of artificial reefs in the marine environment and guidelines for reef construction have been derived from these general regulations. in spite of recent developments, national and/or regional programs for the deployment of artificial reefs and/or their inclusion in overall management plans for integrated management of coastal zones are in force only in the majority of mediterranean countries, while only a few projects have, to date, been undertaken in the other european regions. moreover, there is a noteworthy lack of plans, in many countries, for the management of the reefs after their deployment.
Parrotfish Size: A Simple yet Useful Alternative Indicator of Fishing Effects on Caribbean Reefs?  [PDF]
Henri Vallès, Hazel A. Oxenford
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0086291
Abstract: There is great need to identify simple yet reliable indicators of fishing effects within the multi-species, multi-gear, data-poor fisheries of the Caribbean. Here, we investigate links between fishing pressure and three simple fish metrics, i.e. average fish weight (an estimate of average individual fish size), fish density and fish biomass, derived from (1) the parrotfish family, a ubiquitous herbivore family across the Caribbean, and (2) three fish groups of “commercial” carnivores including snappers and groupers, which are widely-used as indicators of fishing effects. We hypothesize that, because most Caribbean reefs are being heavily fished, fish metrics derived from the less vulnerable parrotfish group would exhibit stronger relationships with fishing pressure on today’s Caribbean reefs than those derived from the highly vulnerable commercial fish groups. We used data from 348 Atlantic and Gulf Rapid Reef Assessment (AGRRA) reef-surveys across the Caribbean to assess relationships between two independent indices of fishing pressure (one derived from human population density data, the other from open to fishing versus protected status) and the three fish metrics derived from the four aforementioned fish groups. We found that, although two fish metrics, average parrotfish weight and combined biomass of selected commercial species, were consistently negatively linked to the indices of fishing pressure across the Caribbean, the parrotfish metric consistently outranked the latter in the strength of the relationship, thus supporting our hypothesis. Overall, our study highlights that (assemblage-level) average parrotfish size might be a useful alternative indicator of fishing effects over the typical conditions of most Caribbean shallow reefs: moderate-to-heavy levels of fishing and low abundance of highly valued commercial species.
Ecological Consequences of Sediment on High-Energy Coral Reefs  [PDF]
Christopher H. R. Goatley, David R. Bellwood
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0077737
Abstract: Sediments are widely accepted as a threat to coral reefs but our understanding of their ecological impacts is limited. Evidence has suggested that benthic sediments bound within the epilithic algal matrix (EAM) suppress reef fish herbivory, a key ecological process maintaining reef resilience. An experimental combination of caging and sediment addition treatments were used to investigate the effects of sediment pulses on herbivory and EAMs and to determine whether sediment addition could trigger a positive-feedback loop, leading to deep, sediment-rich turfs. A 1-week pulsed sediment addition resulted in rapid increases in algal turf length with effects comparable to those seen in herbivore exclusion cages. Contrary to the hypothesised positive-feedback mechanism, benthic sediment loads returned to natural levels within 3 weeks, however, the EAM turfs remained almost 60% longer for at least 3 months. While reduced herbivore density is widely understood to be a major threat to reefs, we show that acute disturbances to reef sediments elicit similar ecological responses in the EAM. With reefs increasingly threatened by both reductions in herbivore biomass and altered sediment fluxes, the development of longer turfs may become more common on coral reefs.
Patterns of genetic structuring in the coral Pocillopora damicornis on reefs in East Africa
Petra Souter, Oskar Henriksson, Niklas Olsson, Mats Grahn
BMC Ecology , 2009, DOI: 10.1186/1472-6785-9-19
Abstract: Gene flow among reefs was found to be variable, with a significant overall genetic subdivision (FST = 0.023 ± 0.004 SE; p < 0.001), however, only 34% of all pairwise population comparisons showed significant differentiation. Panmixia could not be rejected between reefs separated by as much as 697 km, while other sites, separated by only a single kilometre, were found to be significantly differentiated. An analysis of molecular variance indicated that population genetic differentiation was significant only at the smaller spatial scale (< 10 km), whereas panmixia could not be rejected between groups of samples separated by over 100 km. Estimates of contemporary gene flow showed similar results, with numbers of first generation migrants within each population ranging from 0 to 4 (~5% of the total number of colonies sampled) and likely dispersal distances ranging between 5 and 500 km.This study showed that population differentiation in P. damicornis varied over spatial scales and that this variability occurred at both evolutionary and ecological time scales. This paradox is discussed in light of stochastic recruitment and small scale population structures found in other species of coral. The study also identifies potential source reefs, such as those within Mnemba Conservation area near Zanzibar and genetically isolated reefs such as those within Malindi Marine National Park and Reserve in northern Kenya.Current threats to coral reefs, such as elevated sea water temperatures, coral disease, pollution and destructive and unsustainable fishing methods, have depleted or degraded more than half of the world's coral reefs [1-4]. The poor condition of many of these reefs is attributable to the extreme El Nin? event in 1998, which functionally destroyed approximately 16% of the world's coral reefs through bleaching-induced mass mortality. In 2004, slightly more than 40% of the reefs affected by the El Nin? showed signs of recovery. Most of these reefs were exposed to minimal a
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.