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61.
R Daly CAK Daly RH Bennett PD Cowley MAM Pereira JD Filmalter 《African Journal of Marine Science》2018,40(3):315-321
The giant trevally Caranx ignobilis (Forsskål) is an important apex predatory fish typically associated with coral reef communities. It is prized in recreational and commercial fisheries, yet little is known about its aggregation dynamics and susceptibility to fishing pressure. This study reports on a previously undocumented aggregation of mature giant trevally observed over a period of eight years (2010–2017) at Ponta do Ouro Partial Marine Reserve in southern Mozambique. The aggregation is one of the few recorded for this carangid in the western Indian Ocean and represents the first subtropical aggregation of giant trevally. The aggregation is also the largest recorded for this species, with up to 2 413 individuals representing an estimated biomass of approximately 30 tonnes. The size and predictability of this annual aggregation make it vulnerable to overexploitation and point towards the need for an appropriate conservation management strategy. 相似文献
62.
Water samples from Narragansett Bay and the Providence River, and fulvic acid/ saline water solutions were examined for their ability to solubilize n-alkane (n-C16 and n-C20), isoprenoid (pristane) and aromatic (phenanthrene and anthracene) hydrocarbons and dibutyl phthalate. Removal of the dissolved organic matter (D.O.M.) from the natural samples by activated charcoal and by ultra-violet oxidation resulted in a 50–99 per cent decrease in the amounts of n-alkanes and isoprenoid hydrocarbons solubilized. This decrease was directly related to the amount of D.O.M. removed. The solubilities of the aromatic hydrocarbons were unaffected by the D.O.M. Fulvic acid from a marine sediment, surface active organic material isolated at a chloroform/sea water interface, organic material extracted from a marine sediment by sea water, and organic matter contributed by a municipal sewage effluent, promote n-alkane solubility when added to NaCl solutions and re-enhance solubility when added to organic depleted sea water. The solubility of No. 2 fuel oil increased 2.5 times in the presence of fulvic acid (3.7 mg C/l.) with most of the increase seen in the alkane and isoprenoid components.N-Alkane solubility increases in fulvic acid/saline water solutions with increasing pH and reaches a maximum with respect to ionic strength at I = 0.3. There is evidence to suggest that the mode of solubilization of the hydrocarbons is by incorporation into micelles formed by intermolecular association of the surface active humic-type monomers. The presence of ionic species is a prerequisite for micelle formation. 相似文献
63.
Michael R. Winfrey Eric Beck Paul Boehm David M. Ward 《Marine environmental research》1982,7(3):175-194
The activities of methane-producing and sulphate-reducing bacteria in intertidal sediments along the Brittany coast of France were examined in order to determine the effect of the Amoco Cadiz oil spill on sediment microbial processes. Porewater chemistry, methane production, sulphate rate and [2?14C]-acetate metabolism did not vary significantly between beach, estuary, and marsh sites, oiled or unoiled, after the Amoco Cadiz spill. Oiled sediments contained highly weathered oil of Amoco Cadiz origin, but unoiled comparison sites also contained hydrocarbons from anthropogenic sources. The additions of weathered Amoco Cadiz mousse, fresh and slightly weathered light Arabian crude oil, benzene or toluene to sediments from the oiled and unoiled marsh site did not significantly affect rates of sulphate reduction or methane production. The oxidation of [2?14C]-acetate to 14CO2, however, was significantly decreased when mousse, crude oil, benzene or toluene was added to sediments from the unoiled site. Inhibition seemed to be proportional to the extent of weathering. Sediments recently exposed to Amoco Cadiz crude oil were less affected by a second oiling, suggesting that the indigenous populations may have been replaced by organisms more resistant to oil toxicity. These results suggested that the Amoco Cadiz oil spill did not have major long-term effects on sulphate reduction or methane production. 相似文献
64.
Paul D. Boehm 《Marine Chemistry》1980,9(4):255-281
Detailed sampling of the water column and subsequent high-resolution gas chromatographic analyses of surface film, particulate and dissolved hydrocarbons from the Georges Bank region off the New England coast have revealed large spatial and temporal heterogeneity in the source of hydrocarbons. Dissolved hydrocarbons, largely of a petroleum-related origin, surface film hydrocarbon also of a petroleum-related origin but different from the dissolved fraction, and bulk-water particulate matter of a mixed biogenic and petrogenic origin are all decoupled with respect to source and quantity in the region.Surface film (microlayer) hydrocarbons are found in greater concentrations than the dissolved fraction, which in turn is greater than the particulate hydrocarbon quantities in the water column. Although the microlayer appears enriched in hydrocarbons relative to the bulk water, the nature of the hydrocarbons is quite different, indicating that the use of a microlayer enrichment factor may not be appropriate in these waters. 相似文献
65.
F Forget L Dagorn B Mérigot JC Gaertner J Robinson PD Cowley 《African Journal of Marine Science》2020,42(2):247-254
Owing to difficulties in accessing the vast open ocean, the beta (β) diversity of pelagic fish assemblages remains poorly studied. We investigated the relationship between assemblage similarity and geographical distance between anchored fish aggregating devices (FADs), sampled by standardised underwater visual censuses in three anchored FAD arrays in the Indian Ocean—at the Maldives, the Seychelles and Mauritius. The use of two complementary indices of β-diversity, based on presence/absence data (Jaccard similarity coefficient) and abundance data (Bray–Curtis index), revealed that geographical distance between sampling sites (from 4 to 257 km) appeared to have no effect on the similarity of fish assemblages associated with FADs within each array. The results of this preliminary study question the generalisation of the paradigm of an increase in β-diversity with geographic distance to the open-ocean fish community. Large-scale studies using a variety of datasets should be conducted to further investigate patterns of β-diversity in the open ocean. 相似文献
66.
A number of experiments were carried out in the Canadian Arctic on Baffin Island with the purpose of defining the short- and long-term effects of exposure to dispersed crude oil on marine benthic invertebrates. The study reported here assessed metabolic responses by physiological and biochemical indices, and evaluated these in relation to exposure concentration. The overall objective of the study was to evaluate the potential for long-term survival of benthic communities in the Arctic following an oil spill. This objective was consistent with the goals of the larger Baffin Island Oil Spill (BIOS) program, which was implemented to evaluate the relative mitigating effectiveness of chemical dispersants, as compared to conventional oil spill counter-measures. 相似文献
67.
Karen L. Knee Blythe A. Layton Joseph H. Street Alexandria B. Boehm Adina Paytan 《Estuaries and Coasts》2008,31(4):607-622
Water quality monitoring in Hanalei Bay, Kaua`i (Hawai`i, USA) has documented intermittent high concentrations of nutrients
(nitrate, phosphate, silica, and ammonium) and fecal indicator bacteria (FIB, i.e., enterococci and Escherichia coli) in nearshore waters and spurred concern that contaminated groundwater might be discharging into the bay. The present study
sought to identify and track sources of nutrients and FIB to four beaches in Hanalei Bay and one beach outside the bay, together
representing a wide range of land uses. 223Ra and 224Ra activity, salinity, nutrient and FIB concentrations were measured in samples from the coastal aquifer, the nearshore ocean,
springs, the Hanalei River, and smaller streams. In addition, FIB concentrations in beach sands were measured at each site,
and the enterococcal surface protein (esp) gene assay was used to investigate whether the observed FIB originated from a human source. Nutrient concentrations in groundwater
were significantly higher than in nearshore water, inversely correlated to salinity, and highly site specific, indicating
local controls on groundwater quality. Fluxes of groundwater into Hanalei Bay were calculated using a mass-balance approach
and represented at least 2–10% of river discharges. However, submarine groundwater discharge (SGD) may provide 2.7 times as
much nitrate + nitrite to Hanalei Bay as does the Hanalei River. It may also provide significant fluxes of phosphate and ammonium,
comprising 15% and 20% of Hanalei River inputs, respectively. SGD-derived silica inputs to the bay comprised less than 3%
of Hanalei River inputs. FIB concentrations in groundwater were typically lower than those in nearshore water, suggesting
that significant FIB inputs from SGD are unlikely. Positive esp gene assays suggested that some enterococci in environmental samples were of human fecal origin. Identifying how nutrients
and FIB enter nearshore waters will help environmental managers address pressing water quality issues, including exceedances
of the state Enterococcus water quality standard and nutrient loading to coral reefs. 相似文献
68.
69.
Volker Tesmer Johannes Boehm Robert Heinkelmann Harald Schuh 《Journal of Geodesy》2007,81(6-8):409-421
This paper compares estimated terrestrial reference frames (TRF) and celestial reference frames (CRF) as well as position time-series in terms of systematic differences, scale, annual signals and station position repeatabilities using four different tropospheric mapping functions (MF): The NMF (Niell Mapping Function) and the recently developed GMF (Global Mapping Function) consist of easy-to-handle stand-alone formulae, whereas the IMF (Isobaric Mapping Function) and the VMF1 (Vienna Mapping Function 1) are determined from numerical weather models. All computations were performed at the Deutsches Geodätisches Forschungsinstitut (DGFI) using the OCCAM 6.1 and DOGS-CS software packages for Very Long Baseline Interferometry (VLBI) data from 1984 until 2005. While it turned out that CRF estimates only slightly depend on the MF used, showing small systematic effects up to 0.025 mas, some station heights of the computed TRF change by up to 13 mm. The best agreement was achieved for the VMF1 and GMF results concerning the TRFs, and for the VMF1 and IMF results concerning scale variations and position time-series. The amplitudes of the annual periodical signals in the time-series of estimated heights differ by up to 5 mm. The best precision in terms of station height repeatability is found for the VMF1, which is 5–7% better than for the other MFs. 相似文献
70.
The growth rate of speckled snapper Lutjanus rivulatus was investigated using data from a long-term tag-recapture study conducted in the St Lucia Marine Reserve within the iSimangaliso Wetland Park, a World Heritage Site in northern KwaZulu-Natal, South Africa. A total of 1 429 L. rivulatus were tagged and 453 (31.7%) individual fish were recaptured one or more times. Growth rates were modelled from the tag-recapture data using a maximum-likelihood approach. It is shown that L. rivulatus is a slow-growing species with L∞ = 918?mm FL, K = 0.06 and phi-prime (Ø, the growth index) = 2.69. The effects of deep-hooking and multiple captures were tested and this revealed that there was no significant impact on the growth of L. rivulatus. The growth index was lower than that recorded in many other similar congeneric species. Slow growth, coupled with high levels of residency and site fidelity, suggest that this species is vulnerable to exploitation and that a precautionary approach towards future management is appropriate. 相似文献