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SA Mwachireya M Carreiro-Silva BE Hartwick TR McClanahan 《African Journal of Marine Science》2018,40(1):25-42
Microbioerosion rates and microbioeroder community structure were studied in four Kenyan protected coral-reef lagoons using shell fragments of Tridacna giant clams to determine their response to the influence of terrestrial run-off. Fourteen different microbioeroder traces from seven cyanobacteria, three green algae and four fungi species were identified. The river discharge-impacted reef and ‘pristine’ reef showed similar composition but higher microbioeroder abundance and total cyanobacteria- and chlorophyte-bioeroded areas when compared with the other study reefs. Cyanobacteria dominated during the north-east monsoon (NEM) relative to the south-east monsoon (SEM) season, with algae and cyanobacteria being major microbioeroders in the river-impacted and pristine reefs. The rate of microbioerosion varied between 4.3 g CaCO3 m?2 y?1 (SEM) and 134.7 g CaCO3 m?2 y?1 (NEM), and was highest in the river-impacted reef (127.6 g CaCO3 m?2 y?1), which was almost double that in the pristine reef (69.5 g CaCO3 m?2 y?1) and the mangrove-fringed reef (56.2 g CaCO3 m?2 y?1). The microbioerosion rates measured in this study may not be high enough to cause concern with regard to the health and net carbonate production of Kenya’s coral reefs. Nevertheless, predicted increases in the frequency and severity of stresses related to global climate change (e.g. increased sea surface temperature, acidification), as well as interactions with local disturbances and their influence on bioerosion, may be increasingly important in the future. 相似文献
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Experimental investigation of various vegetable fibers as sorbent materials for oil spills 总被引：7，自引：0，他引：7
Oil spills are a global concern due to their environmental and economical impact. Various commercial systems have been developed to control these spills, including the use of fibers as sorbents. This research investigates the use of various vegetable fibers, namely mixed leaves residues, mixed sawdust, sisal (Agave sisalana), coir fiber (Cocos nucifera), sponge-gourd (Luffa cylindrica) and silk-floss as sorbent materials of crude oil. Sorption tests with crude oil were conducted in deionized and marine water media, with and without agitation. Water uptake by the fibers was investigated by tests in dry conditions and distillation of the impregnated sorbent. The silk-floss fiber showed a very high degree of hydrophobicity and oil sorption capacity of approximately 85goil/g sorbent (in 24hours). Specific gravity measurements and buoyancy tests were also used to evaluate the suitability of these fibers for the intended application. 相似文献
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RJM Crawford RM Randall TR Cook PG Ryan BM Dyer R Fox 《African Journal of Marine Science》2016,38(3):373-383
Numbers of Cape cormorants Phalacrocorax capensis breeding in South Africa decreased by nearly 50% from approximately 107 000 pairs in 1977–1981 to 57 000 pairs in 2010–2014. Although four colonies had >10 000 pairs in 1977–1981, there was just one such colony in 2010–2014. Almost all the decrease occurred after the early 1990s off north-west South Africa, between the Orange River estuary and Dassen Island. South of this, the number breeding in the two periods was stable, with some colonies being formed or growing rapidly in the 2000s. The proportion of South Africa’s Cape cormorants that bred south of Dassen Island increased from 35% in 1977–1981 to 66% in 2010–2014, with the opposite situation observed in the north-west. This matched a shift to the south and east in the distributions of two of the Cape cormorant’s main prey species, anchovy Engraulis encrasicolus and sardine Sardinops sagax. In 2014, an apparent scarcity of prey in the north-west resulted in Cape cormorants attempting to take bait from hooks of fishing lines over an extended period, a behaviour not previously recorded. The number of Cape cormorants breeding in the south may be constrained by the absence of large islands between Dyer Island in the west and Algoa Bay in the east. If so, it may be possible to bolster the southern population through the provision of appropriate breeding habitat, such as platforms, or restricting human disturbance at suitable mainland cliff breeding sites. 相似文献
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Modern foraminiferal assemblage zones can be used to reconstruct palaeo sea levels when applied to fossil foraminifera down a sediment core. Previous intertidal foraminiferal studies have predominantly focused on assemblages in surface sediments (0–1 cm), with the rationale that surface assemblages reflect the modern-day environment. Foraminifera live infaunally and therefore there is a need to document the infaunal vertical distribution of living foraminifera to fully capture the modern environment. Infaunal foraminiferal populations may compositionally differ from or be similar to those in the uppermost 1 cm of a core sample, but abundance is variable vertically, making it very complex to reconstruct and interpret past sea levels. This can have implications for the choice of assemblages to use as modern analogues for past sea-level reconstructions. This study documents the vertical infaunal distribution of living foraminifera, to allow for more informed interpretations of palaeo-reconstructions in mangrove environments. The down-core vertical distribution and abundance of living foraminifera, along with grain size and organic content, were documented using sediment cores along an elevational transect. Nine taxa were recorded as living at the time of collection, six of which were restricted to the top 4 cm. The majority of these were calcareous and found in the cores situated closer to the intertidal channel. Therefore, we argue that the diversity of living calcareous and agglutinated foraminifera could be restricted by grain size, with coarser grain sizes associated with lower species diversity. The findings suggest that foraminiferal species inhabiting the top 4 cm represent deeper living foraminiferal populations. Therefore, the top 4-cm interval can be used to establish a modern training set upon which reconstructions can be based. The findings from this study will provide guidance on the use of South African mangrove environments for future sea-level reconstructions. 相似文献
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五大连池火山群喷气锥成因机制探讨 总被引：1，自引：0，他引：1
五大连池火山群1537个喷气锥中,多数分布在火烧山熔岩流中,在水量充足的五池到四池之间的熔岩台地上,喷气锥数量集中、个体较大、发育良好。通过对五大连池火山群喷气锥的形态结构和集中分布特点进行分析,认为水蒸气在混合气体形成喷气锥中起主导作用,重力也在喷气锥形态塑造上有一定意义。含挥发分的基性岩浆溢流到在靠近水域的地区时表层冷凝固结,内部熔岩仍温度高、粘度低,与地下水作用形成火山气体和水蒸气构成的混合气体,气体冲破表层间歇溢出时,带动熔岩外掀堆叠在喷气孔周围形成喷气锥,中央保留气体多次逸出的通道形成中空结构。当气体压力不足以使熔岩从喷口溢出,喷气锥的生长停止。 相似文献
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A Payo-Payo A Sanz-Aguilar D Gaglio RB Sherley TR Cook R Altwegg 《African Journal of Marine Science》2018,40(1):43-50
The nominate race of the greater crested tern Thalasseus bergii breeds only along the coast of the Benguela region (west coast) of southern Africa, where its population is increasing, in contrast to other species of breeding seabirds in the region which similarly depend on forage fish. Although this population’s trends are well known, its demographic parameters remain obscure. We used multi-event capture–recapture–recovery modelling to provide the first estimates of survival. The survival rate of birds older than two years was 0.93 (0.91–0.95); second-year survival was 0.93 (0.90–0.95) and first-year survival was 0.80 (0.73–0.85). A resighting of a 34-year-old bird is a new longevity record for the species. Population growth rates projected with a Leslie matrix model that included our survival estimates were very similar to estimates from annual counts of the breeding population (7–8% y?1), suggesting that these survival estimates adequately describe the species’ demography. High survival rates have likely contributed to the species’ recent population increase in the region. 相似文献
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We measured tissue phosphorus content of high and low intertidal Hormosira banksii to test the hypothesis that tissue phosphorus content would be greater in individuals from the low intertidal because of greater total uptake associated with longer immersion in seawater. Moreover, we predicted that tissue phosphorus would be greater at sites where the seawater contained higher phosphate concentrations. There was a positive, linear relationship between local seawater phosphate concentrations and tissue phosphorus content of H. banksii from high and low intertidal zones at six different sites in winter. However, there were no comparable relationships in summer, even though the range of seawater phosphate concentration was similar in both seasons. The phosphorus contents of low intertidal H. banksii were significantly greater than high intertidal H. banksii in winter, but not in summer. Reasons for these differences may be related to greater access to seawater phosphate in low intertidal algae (than those in the high intertidal) in winter, followed by greater utilisation of the internal phosphorus between winter and summer, due to faster growth rates in the low intertidal. 相似文献
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