| 1. |
- Dahl, Mikael, 1976, et al.
(författare)
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Fine-scale spatial genetic structure and clonal distribution of the cold-water coral Lophelia pertusa
- 2012
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Ingår i: Coral Reefs. - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 31:4, s. 1135-1148
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Tidskriftsartikel (refereegranskat)abstract
- Determining the spatial genetic structure within and among cold-water coral populations is crucial to understanding population dynamics, assessing the resilience of cold-water coral communities and estimating genetic effects of habitat fragmentation for conservation. The spatial distribution of genetic diversity in natural populations depends on the species' mode of reproduction, and coral species often have a mixed strategy of sexual and asexual reproduction. We describe the clonal architecture of a cold-water coral reef and the fine-scale population genetic structure (< 35 km) of five reef localities in the NE Skagerrak. This study represents the first of this type of analysis from deep waters. We used thirteen microsatellite loci to estimate gene flow and genotypic diversity and to describe the fine-scale spatial distribution of clonal individuals of Lophelia pertusa. Within-population genetic diversity was high in four of the five reef localities. These four reefs constitute a genetic cluster with asymmetric gene flow that indicates metapopulation dynamics. One locality, the Sacken reef, was genetically isolated and depauperate. Asexual reproduction was found to be a highly important mode of reproduction for L. pertusa: 35 genetic individuals were found on the largest reef, with the largest clone covering an area of nearly 300 m(2).
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| 2. |
- De Clippele, L. H., et al.
(författare)
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The effect of local hydrodynamics on the spatial extent and morphology of cold-water coral habitats at Tisler Reef, Norway
- 2018
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Ingår i: Coral Reefs. - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 37:1, s. 253-266
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Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates how cold-water coral morphology and habitat distribution are shaped by local hydrodynamics, using high-definition video from Tisler Reef, an inshore reef in Norway. A total of 334 video frames collected on the north-west (NW) and south-east (SE) side of the reef were investigated for Lophelia pertusa coral cover and morphology and for the cover of the associated sponges Mycale lingua and Geodia sp. Our results showed that the SE side was a better habitat for L. pertusa (including live and dead colonies). Low cover of Geodia sp. was found on both sides of Tisler Reef. In contrast, Mycale lingua had higher percentage cover, especially on the NW side of the reef. Bush-shaped colonies of L. pertusa with elongated branches were the most abundant coral morphology on Tisler Reef. The highest abundance and density of this morphology were found on the SE side of the reef, while a higher proportion of cauliflower-shaped corals with short branches were found on the NW side. The proportion of very small L. pertusa colonies was also significantly higher on the SE side of the reef. The patterns in coral spatial distribution and morphology were related to local hydrodynamics-there were more frequent periods of downwelling currents on the SE side-and to the availability of suitable settling substrates. These factors make the SE region of Tisler Reef more suitable for coral growth. Understanding the impact of local hydrodynamics on the spatial extent and morphology of coral, and their relation to associated organisms such as sponges, is key to understanding the past and future development of the reef.
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| 3. |
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| 4. |
- Engelen, Aschwin H., et al.
(författare)
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Life history flexibility allows Sargassum polyceratium to persist in different environments subjected to stochastic disturbance events
- 2005
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Ingår i: Coral Reefs. - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 24:4, s. 670-680
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Tidskriftsartikel (refereegranskat)abstract
- Stochastic, stage-based matrix models were used to investigate the life history strategy of the seaweed Sargassum polyceratium in shallow intertidal and deep-water (18 m) populations. Matrix models were parameterized with 3 years of yearly transitions among four plant stages quantified from three bays on Curac.ao (Netherlands Antilles). There were years without a storm, with a moderate (winter) storm and with a strong storm (Hurricane Lenny). The stochastic population growth rate varied among populations (ks : 0.54–1.03) but was not related to depth. The most important stages for population growth were reproductive adults (shallow) and non-reproductive adults (deep). With the occurrence of storms, vegetative growth (mainly deep) and fertility (mainly shallow) became the most important processes. Recruitment (shallow) and regeneration from holdfasts (deep) only contributed to population persistence after the hurricane. It is concluded that S . polyceratium has a flexible, depth-dependent, life history strategy that is adjusted to disturbance events.
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| 5. |
- Farfan, Gabriela A., et al.
(författare)
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Crystallographic and chemical signatures in coral skeletal aragonite
- 2022
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Ingår i: Coral Reefs. - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 41, s. 19-34
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Tidskriftsartikel (refereegranskat)abstract
- Corals nucleate and grow aragonite crystals, organizing them into intricate skeletal structures that ultimately build the world’s coral reefs. Crystallography and chemistry have profound influence on the material properties of these skeletal building blocks, yet gaps remain in our knowledge about coral aragonite on the atomic scale. Across a broad diversity of shallow-water and deep-sea scleractinian corals from vastly different environments, coral aragonites are remarkably similar to one another, confirming that corals exert control on the carbonate chemistry of the calcifying space relative to the surrounding seawater. Nuances in coral aragonite structures relate most closely to trace element chemistry and aragonite saturation state, suggesting the primary controls on aragonite structure are ionic strength and trace element chemistry, with growth rate playing a secondary role. We also show how coral aragonites are crystallographically indistinguishable from synthetic abiogenic aragonite analogs precipitated from seawater under conditions mimicking coral calcifying fluid. In contrast, coral aragonites are distinct from geologically formed aragonites, a synthetic aragonite precipitated from a freshwater solution, and mollusk aragonites. Crystallographic signatures have future applications in understanding the material properties of coral aragonite and predicting the persistence of coral reefs in a rapidly changing ocean.
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| 6. |
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| 7. |
- Frisch, Ashley J., et al.
(författare)
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Reassessing the trophic role of reef sharks as apex predators on coral reefs
- 2016
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Ingår i: Coral reefs (Print). - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 35:2, s. 459-472
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Tidskriftsartikel (refereegranskat)abstract
- Apex predators often have strong top-down effects on ecosystem components and are therefore a priority for conservation and management. Due to their large size and conspicuous predatory behaviour, reef sharks are typically assumed to be apex predators, but their functional role is yet to be confirmed. In this study, we used stomach contents and stable isotopes to estimate diet, trophic position and carbon sources for three common species of reef shark (Triaenodon obesus, Carcharhinus melanopterus and C. amblyrhynchos) from the Great Barrier Reef (Australia) and evaluated their assumed functional role as apex predators by qualitative and quantitative comparisons with other sharks and large predatory fishes. We found that reef sharks do not occupy the apex of coral reef food chains, but instead have functional roles similar to those of large predatory fishes such as snappers, emperors and groupers, which are typically regarded as high-level mesopredators. We hypothesise that a degree of functional redundancy exists within this guild of predators, potentially explaining why shark-induced trophic cascades are rare or subtle in coral reef ecosystems. We also found that reef sharks participate in multiple food webs (pelagic and benthic) and are sustained by multiple sources of primary production. We conclude that large conspicuous predators, be they elasmobranchs or any other taxon, should not axiomatically be regarded as apex predators without thorough analysis of their diet. In the case of reef sharks, our dietary analyses suggest they should be reassigned to an alternative trophic group such as high-level mesopredators. This change will facilitate improved understanding of how reef communities function and how removal of predators (e.g., via fishing) might affect ecosystem properties.
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| 8. |
- Guihen, D., et al.
(författare)
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Zooplankton drive diurnal changes in oxygen concentration at Tisler cold-water coral reef
- 2018
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Ingår i: Coral Reefs. - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 37:4, s. 1013-1025
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Tidskriftsartikel (refereegranskat)abstract
- Tisler Reef is a Norwegian cold-water coral reef in the Northeastern Skagerrak, which lies at an average depth of 120m, is constructed principally of the scleractinian coral Lophelia pertusa and hosts a dynamic and diverse ecosystem. The availability of oxygen within Tisler Reef, recorded between 2006 and 2008, showed a decline during the summer months, caused by both the isolation of the reef from the atmosphere under conditions of seasonal stratification, and the enhanced respiration in the water column during the seasonal zooplankton proliferations. Concentrations of dissolved oxygen were replenished from high-current flows advecting water from off the reef. Low current flow conditions (<0.05ms(-1)) coincided with a short-term reduction in oxygen, the extent of which varied seasonally and were observed to be greatest during July and August, coinciding with the summer Calanus proliferation in the Skagerrak. Normalized acoustic backscatter amplitude during the summer months showed a strong signal of zooplankton diurnal vertical migration, coinciding with the lowest oxygen concentrations at the reef observed during, and lagging slightly after, the deep phase of the zooplankton vertical migration. This effect was most obvious during low-flow conditions; highlighting the importance of zooplankton and associated activity as a consumer of oxygen at the reef.
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| 9. |
- Hellström, Ann Micaela, et al.
(författare)
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Robustness of size measurements in soft corals
- 2011
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Ingår i: Coral reefs (Print). - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 30:3, s. 787-790
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Tidskriftsartikel (refereegranskat)abstract
- Accurate colony size measurement in soft-bodied sessile aquatic invertebrates is more difficult than in hard corals because of the variable state of the hydroskeleton in the former. The present study examined variation in colony height, oral disc diameter and basal circumference in three species of soft coral of different morphological types (Sarcophyton elegans, Sinularia flexibilis and Dendronephthya sp.) over a 24-h period. Individual colonies changed considerably in size over this period. Coefficients of variation for height measurements and oral disc were 0.09–0.36 and 0.08–0.28, respectively, but were only 0.02–0.09 for basal circumference, in all three species. Measurements of basal circumference in the field showed the highest correlation with colony biomass (volume after water displacement in formalin) confirming basal circumference to be a sound measure of colony size in repeated measurement studies.
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| 10. |
- Johnstone, J. W., et al.
(författare)
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Antarctic deep-sea coral larvae may be resistant to end-century ocean warming
- 2022
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Ingår i: Coral Reefs. - : Springer Science and Business Media LLC. - 0722-4028 .- 1432-0975. ; 41, s. 1495-1510
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Tidskriftsartikel (refereegranskat)abstract
- The Western Antarctic Peninsula is home to a diverse assemblage of deep-sea species and is warming faster than any other region in the Southern Hemisphere. This study investigated how larval development of the Antarctic cold-water coral Flabellum impensum was affected by temperatures consistent with ocean warming trends predicted for the twenty-first century. F. impensum larvae were cultured under four temperature conditions and scanning electron microscopy, transmission electron microscopy, and flow cytometry were used to compare settlement, mortality, larval size, development, deformity, and cellular health over the course of 44 days. While temperature did not impact settlement, mortality, or larval stress, the warmer treatments did have a significant impact on developmental rate. Samples exposed to warmer conditions developed faster than those in cooler conditions. Increased developmental rates were not accompanied by increased stress indicators such as deformity, mortality, or programmed cell death, suggesting that larval health was not negatively impacted by the rate change and may indicate that F. impensum larvae are tolerant of warming temperatures. Development and deformity assessments considered larval condition during the period between release and settlement, when larvae are thought to be especially sensitive to environmental impacts, and when the effects of those impacts on settlement or mortality may be particularly consequential for biogeography and population survival. These results suggest that larval development of F. impensum may be largely resistant to ocean warming trends predicted for the twenty-first century.
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