Factors controlling litter input dynamics in streams draining pasture,pine, and native forest catchments     

M. R. Scarsbrook  J. M. Quinn  J. Halliday  R. Morse 《新西兰海洋与淡水研究杂志》2013,47(4):751-762

The effects of varying land use on the inputs of litter to streams were investigated in nine small Waikato, New Zealand, hill country streams between June 1995 and October 1997. Mass, timing, and composition of both vertical and lateral litter inputs were measured. Litter inputs to pasture streams were lower than those to streams in native or exotic pine forest. Litter inputs to native forest streams peaked in summer, with leaf material forming the dominant litter‐type throughout the year. The pine forest sites showed a winter minimum, with a pulse of reproductive litter (pollen heads) in spring. One pasture site, where riparian vegetation included willow and poplar showed an autumnal peak, with low inputs at other times of the year. Climate variables (air temperature, rainfall, and windrun) varied in their power of prediction of litter inputs. Mean air temperature showed a strong positive relationship with monthly litter input at the most intensively sampled native forest site. Annual litter inputs were positively related to canopy cover, although canopy‐type modified this relationship. At several sites lateral inputs of litter showed a positive relationship with the slope of the contributing area. Overall, lateral inputs were positively related to % unvegetated groundcover. In open pastures the combination of a lack of riparian trees, and the potential litter‐trapping capacity of pasture grasses, severely limits inputs of coarse particulate organic matter to streams.  相似文献   

Annual variation in the nocturnal nekton assemblage of a tropical estuary     

Norman J. Quinn  Barbara L. Kojis 《Estuarine, Coastal and Shelf Science》1985,21(4):511-537

A nocturnal demersal nekton assemblage was sampled fortnightly for two years at five sites in the Labu estuary using a 3 m beam trawl with a 3·2 cm mesh net. Forty-eight species were caught, totalling 31 458 individuals with the five most abundant species comprising over 95% of the catch. Using multiple regression techniques with Fourier transformations, the mean number of species, S, the mean abundance, N, and mean weight, W, were found to conform to a regular annual cycle with maxima in April and May. Seven of the 11 most abundant species demonstrated regular annual cycles of abundance. S, N and W were greatest in the wider, middle sites and lowest in a shallow, stagnant side branch of the estuary. Catch weights and abundances were significantly correlated with physical data.Salinity and temperature values in the estuary exhibited an annual cycle with maxima occurring in February/March. The annual thermal variation of surface water outside the estuary followed a similar cycle. The salinity at the mouth of the Markham River is lowest during January/February, which corresponds with the rainy season in the Markham River catchment. Significant annual variation existed between years in estuarine bottom salinity and salinity values in Labu Bay.Several species exhibited a greater variation in abundance and mass between years than within years. This supports the hypothesis that in the tropics between-year variation in coastal marine biotic communities is greater than within-year variation.  相似文献   

Equilibria of the marine multiphase ammonia system   总被引：3，自引：0，他引：3  

P. K. Quinn  W. E. Asher  R. J. Charlson 《Journal of Atmospheric Chemistry》1992,14(1-4):11-30

A lack of empirical data has made it difficult to ascertain whether ammonia is in equilibrium between the oceanic, atmospheric gas and atmospheric particle phases in the remote marine environment. Reported here are simultaneous measurements of the saturation concentration of ammonia relative to ammonia concentrations in ocean surface waters; total seawater ammonia; atmospheric gas phase ammonia; and atmospheric particulate-phase ammonium, non-seasalt sulfate, methanesulfonate, and nitrate. Sampling was performed in May of 1987 in the northeast Pacific Ocean environment and in April and May of 1988 in the central Pacific Ocean environment.These measurements were used to determine the degree to which ammonia approached equilibrium between the oceanic and atmospheric gas and aerosol particle phases. The experimental atmospheric gas phase ammonia concentrations were compared with calculated equilibrium concentrations assuming a Henry's law type of partitioning between the gas and condensed phases. Characteristic times of the processes controlling the fate of ammonia in the marine environment also were compared.The measured atmospheric gas phase and oceanic concentrations of ammonia indicate that ammonia is not in a Henry's law equilibrium across the air/sea interface. This disequilibrium is a result of the long air/sea exchange equilibration time relative to the lifetime of ammonia in the atmosphere. Comparison of the calculated equilibrium gas phase ammonia concentrations with the measured gas phase ammonia concentrations shows that attainment of equilibrium between the atmospheric gas and particle phases is a strong function of the chemical composition of the aerosol particles. The data suggest that fully neutralized aerosol particles are not in Henry's law equilibrium with the gas phase while equilibrium is observed for particles with an average ammonium to non-seasalt sulfate molar ratio less than 1.8.  相似文献   

Federal drought planning in the Great Plains — A first look     

M. L. Quinn 《Climatic change》1982,4(3):273-296

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Biogeochemistry of fatty acids in recent sediments from Narragansett Bay,Rhode Island     

John W. Farrington  James G. Quinn 《Geochimica et cosmochimica acta》1973,37(2):259-268

The fatty acid composition of sediments from Narragansett Bay show significant variation between certain areas of the Bay. Both the organic carbon and fatty acid concentrations decrease with increasing distance from the Providence River area—an area which received municipal sewage and industrial effluents. The ratio of the fatty acid concentration to organic carbon concentration is fairly constant for all stations sampled. The variations in the relative abundance of fatty acids may reflect either the influence of fatty acids discharged to the river area by sewage effluents or the synthesis of fatty acids by microbial populations which probably differ for the areas compared. Temporal variations in fatty acid composition and fatty acid concentration are minimal. Lipolytic activity has been demonstrated and probably acts on glycerides deposited to the sediments releasing free fatty acids shortly after deposition. A model for the diagenesis of fatty acids in Recent sediments is proposed based upon the above findings and upon earlier reports by the authors and by other investigators.  相似文献   

Comparative Scavenging of Yttrium and the Rare Earth Elements in Seawater: Competitive Influences of Solution and Surface Chemistry     

Kelly A. Quinn  Robert H. Byrne  Johan Schijf 《Aquatic Geochemistry》2004,10(1-2):59-80

Distribution coefficients were obtained for yttrium and the rare earth elements (YREEs) in aqueous solutions containing freshly precipitated hydroxides of trivalent cations (Fe³⁺, Al³⁺, Ga³⁺, and In³⁺). Observed patterns of log _i K _S–, where _i K _S = [MS _i ][M³⁺]^?1[S _i ]^?1, [MS _i ] is the concentration of a sorbed YREE, [M³⁺] is the concentration of a free hydrated YREE ion, and [S _i] is the concentration of a sorptive solid substrate (Fe(III), Al, Ga, In)– exhibited similarities to patterns of YREE solution complexation constants with hydroxide (_OH β ₁) and fluoride (_F β ₁), but also distinct differences. The log _i K _S pattern for YREE sorption on Al hydroxide precipitates is very similar to the pattern of YREE hydroxide stability constants (log_OH β ₁) in solution. Linear free-energy relationships between log _i K _S and log_OH β ₁ showed excellent correlation for YREE sorption on Al hydroxide precipitates, good correlation for YREE sorption on Ga or In hydroxide precipitates, yet poor correlation for YREE sorption on Fe(III) hydroxide precipitates. Whereas the correlation between log _i K _S and log_F β ₁ was generally poor, patterns of log( _i K _S/_F β ₁) displayed substantially increased smoothness compared to patterns of log _i K _S. This indicates that the conspicuous sequence of inflections along the YREE series in the patterns of log _i K _S and log_F β ₁ is very similar, particularly for In and Fe(III) hydroxide precipitates. While the log _i K _S patterns obtained with Fe(III) hydroxide precipitates in this work are quite distinct from those obtained with Al, Ga, and In hydroxide precipitates, they are in good agreement with patterns of YREE sorption on ferric oxyhydroxide precipitates reported by others. Furthermore, our log _i K _S patterns for Fe(III) hydroxide precipitates bear a striking resemblance to predicted log _i K _S patterns for natural surfaces that are based on YREE solution chemistry and shale-normalized YREE concentrations in seawater. Yttrium exhibits an itinerant behavior among the REEs: sorption of Y on Fe(III) hydroxide precipitates is intermediate to that of La and Ce, while for Al hydroxide precipitates Y sorption is similar to that of Eu. This behavior of Y can be rationalized from the propensities of different YREEs for covalent vs. ionic interactions. The relatively high shale-normalized concentration of Y in seawater can be explained in terms of primarily covalent YREE interactions with scavenging particulate matter, whereby Y behaves as a light REE, and primarily ionic interactions with solution ligands, whereby Y behaves as a heavy REE.  相似文献   

New strategies to detect life on Mars     

Jeffrey L Bada  Mark A Sephton  Pascale Ehrenfreund  Richard A Mathies  Allison M Skelley  Frank J Grunthaner  Aaron P Zent  Richard C Quinn  Jean-Luc Josset  François Robert  Oliver Botta  Daniel P Glavin 《Astronomy& Geophysics》2005,46(6):6.26-6.27

If we are to find unequivocal evidence for life on Mars, we will need new ways to search for it. Jeff L Bada and the MOD team describe the innovative strategy developed for the ExoMars mission.  相似文献   

Geochemistry of C₂₅ and C₃₀ biogenic alkenes in sediments of the narragansett bay estuary     

Adolfo G Requejo  James G Quinn 《Geochimica et cosmochimica acta》1983,47(6):1075-1090

The distributions of a series of structurally related C₂₅ and C₃₀ biogenic alkenes in sediments of the Narragansett Bay estuary have been determined. The suite of alkenes detected differs both quantitatively and qualitatively from those previously reported in other estuanne and coastal regions. Four C₂₅ mono- and dienes and one C₃₀ diene comprise 73–91% of the total alkenes in all surface (upper 2.5–5 cm) sediments analyzed. However, significant geographic variations exist in the relative abundance of these five compounds throughout the estuary. A comparison of alkene concentrations with δ¹³C of the bulk sedimentary organic matter has shown that the geographic variations of some alkenes reflect the distribution of marine organic matter, suggesting a marine source for these compounds. The distributions of other alkenes are not similarly correlated. In particular, concentrations of the C₃₀ diene are relatively constant and exhibit no dependence on the origin of organic matter in these sediments. This distribution implies an in situ production of this alkene throughout the estuary. Analysis of several sediment cores reveals that alkene concentrations are generally highest at the surface and decrease to low, constant values within the upper 25 cm. An exception is the subsurface concentration of one C₂₅ diene, which exhibits an increase at the same depth in two separate upper bay cores.  相似文献   

Evolution of a Shallow Water Wave‐Dominated Shipwreck Site: Fougueux (1805), Gulf of Cadiz     

T. Fernndez‐Montblanc  R. Quinn  A. Izquierdo  M. Bethencourt 《Geoarchaeology》2016,31(6):487-505

The evolution of the shallow water wave‐dominated Fougueux wreck site in the Gulf of Cadiz was investigated through repeat bathymetric surveys, wave‐ and current‐velocity field measurements, and numerical modeling. This multidisciplinary approach was used to understand the relationships between scouring, morphodynamic change, and hydrodynamic forcing. Field experiments and numerical models indicate that wave processes dominate site evolution. Numerical model outputs indicate current velocity, bed shear stress, orbital velocity, and specially wave fraction breaking (with an increase of 45% and 135% for weak and significant storm conditions, respectively) are all amplified at the site. Scour pits 0.8 m depth inshore and 0.4 m depth offshore of the wreck are developed in response to hydrodynamic forcing. Time‐lapse bathymetric surveys quantify seasonal geomorphological change at the Fougueux. Up to 1.2 m of sediment is deposited and 0.7 m of sediment eroded in response to seasonal wave climate variation (an increase of 0.5 m for mean significant wave height, 0.9 m for significant wave height corresponding to 99% of nonexceedance probability, and 0.4 m·s⁻¹ for mean near‐bed orbital velocity during winter conditions). A two‐dimensional scour model reproduces observed seasonal scour changes. Results have direct applications at all stages of a wreck site investigation.  相似文献   

Ecotoxicological effects of a semi-submerged municipal dump (Castle harbour, Bermuda) on the Calico scallop Argopecten gibbus     

Quinn B  Gagné F  Weber JP  Blaise C 《Marine pollution bulletin》2005,51(5-7):534-544

A biomarker study was undertaken using the Calico scallop Argopecten gibbus to assess the ecotoxicological effects of a semi-submerged municipal dump on the adjacent patch reef lagoon ecosystem (Castle harbour, Bermuda). Caged scallops were deployed in situ for 2 months at various distances from the dump (50 m, 900 m and 2.7 km) and at a reference site (14 km). A suite of biomarkers comprising metallothionein (MT), lipid peroxidation (LPO), vitellin-like proteins (Vn), glutathione S-transferase (GST), DNA strand breaks and condition factor (CF) were investigated in various tissues of the scallop (gill, digestive gland and gonad). Levels of heavy metals were also measured in the whole scallop soft tissue. While there was some variation in response between tissues, in general the results indicated that the dump was negatively impacting scallops deployed in the adjacent marine environment: elevated levels of MT, DNA strand breaks, Vn and GST and reduced condition factor were found for scallops deployed nearest to the dump and at the site 1.5 km from this point source of contamination (Tuckers town) in Castle harbour, with respect to the reference site, North Rock (although this exhibited some degree of metal contamination). The gills from scallops deployed at the dump site were the most responsive tissue, with the highest expression of MT, LPO and DNA damage. This study indicates the potential of the Calico scallop as a convenient bioindicator species in the marine tropical benthos.  相似文献