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81.
Consideration of the oasis analogy for chemosynthetic communities at Gulf of Mexico hydrocarbon vents 总被引:4,自引:0,他引:4
Robert S. Carney 《Geo-Marine Letters》1994,14(2-3):149-159
The analogy between desert oasis and deep-sea chemosynthetic community arose from the biomass contrast between vents and the relatively depauperate background benthic fauna. Fully developed, the analogy helps pose questions about interactions with the background fauna with respect to resources, colonization, and persistence. The chemosynthetic sites of the Gulf of Mexico provide an opportunity to consider possible interactions between vent and nonvent fauna over a 3000-m depth range. It is postulated that deep chemosynthetic communities require the operation of geochemical transporting and concentrating processes to overcome low levels of in situ methane and sulfide production. Clathrate reservoirs may serve these functions. A few chemosynthetic species at the Gulf of Mexico upper slope sites are related to shallow-water sulfide species, but it can be speculated that the dominant chemosynthetic fauna may have originated in a wide spread deep sulfide biome of the Cretaceous. Generic endemism of consumers is low in Gulf of Mexico sites, suggesting a high level of colonization from the surrounding benthos. Chemosynthetic communities may avoid excessive colonization by predators in spite of the apparent food limitation of the surrounding benthos due to toxicity or an evolutionary mechanism selecting against specialized predators. The abundance of large predators is related to the composition of the surrounding benthos and is high at the Gulf of Mexico upper slope sites. Exclusion of chemosyntheic communities from shallower depths may be due to excessive predation by generalists. 相似文献
82.
83.
84.
J. Christopher Rutherford Roger G. Young John M. Quinn Robert J. Wilcock 《新西兰海洋与淡水研究杂志》2020,54(3):410-430
ABSTRACT Instream processes alter the concentration and bioavailability of nutrients as they are transported downstream. By relating primary production and periphyton composition to changes in nutrient concentration in a gravel-bed river this study made inferences about recycling and attenuation. Where dissolved inorganic nitrogen (DIN) was abundant, concentrations decreased linearly with distance but by less than required to meet the nitrogen demand of primary production. Where DIN was barely measurable photosynthesis was reduced but only by 50%. We infer that recycling sustained primary production even when DIN concentrations were negligibly small. One implication is that DIN removal underestimates attenuation. Further experimental research on recycling and improved modelling is required to better quantify the length of streams adversely affected by nutrients. 相似文献
85.
Robert D. Pierce 《Ocean Engineering》1985,12(6):493-529
A procedure is presented for the estimation of extreme values of stationary Gaussian random processes with arbitrary bandwidths. This approach is based on the analytic envelope defined by the Hilbert Transform; this envelope is Rayleigh distributed regardless of bandwidth. For experimentally derived data that has been converted into digital form, the Hilbert Transform is approximated using algorithms implemented on a digital computer to produce samples of the envelope's time history. Next, the degree of correlation between these envelope samples is taken into account using a method developed from simulation studies of a series of synthetic Gaussian time histories with varying bandwidths. Once this correlation effect has been estimated, the standard methods of order statistics are applied to these samples using the Rayleigh probability density function. Examples of applying this procedure to experimentally derived data are presented. 相似文献
86.
In 1980, a large earthquake caused extensive sediment failure on the shallow continental shelf off the Klamath River in northern
California. Side-scan sonography was used to complement detailed geophysical profiling in identifying specific features and
resolving modes of failure. The features include a nearly flat failure terrace mantled with sand boils, collapse craters and
sediment flows, and bounded on the seaward side by a meandering continuous toe ridge. Seaward of the terrace lies a compression
zone delineated by small pressure ridges. Our findings indicate a temporal progression of failure from lique-faction of shallow
subsurface sand to lateral spread of intact blocks to sediment collapse and flow. 相似文献
87.
The sterol composition of a cockle population from an unpolluted environment in South Wales was monitored by monthly sampling over a 12-month period. In spite of the likely variation in dietary sterols during this period, the component sterols of the cockles showed no significant seasonal variation, indicating that the cockle was able to exhibit a high degree of control over the composition of its functional sterols.Dramatic differences were observed in the sterol compositions of a nearby cockle population from a highly polluted environment, near a sewage outfall; only three out of the ten sterols present were common to the unpolluted cockles. Forty-five per cent of the sterols from the ‘polluted’ samples contained fully reduced systems and included three new alkylated C-29, C-30 and C-31 stanols. It is considered possible that these structural changes may affect the stereochemistry of the functional sterols and hence alter the permeability of the animal's membranes. This may reflect a biochemical response to the polluted environment. 相似文献
88.
89.
Robert E. Salomon 《Ocean Engineering》1989,16(3)
A device for converting ocean wave energy into electricity utilizing a rocking buoy and a hydrogen pressure cell is described. The moored buoy contains a pneumatic tube filled with a dense liquid which rocks back and forth as a result of the ocean wave activity. Hydrogen gas, maintained above the dense fluid is alternatively compressed and expanded by the moving fluid. The hydrogen gas communicates with a hydrogen pressure cell and the resulting pressure difference across the cell leads to an electrical voltage and under load, to electrical power. 相似文献
90.
氮浓度对四株海洋绿藻总脂含量和脂肪酸组成的影响 总被引:6,自引:0,他引:6
本文用NaNO3作为氮源,分别作了氮浓度的五个水平对2属(小球藻属、裂丝藻属)的四株绿藻的生长率、总脂含量及主要脂肪酸组成的影响。C19、C97和C102的脂肪含量随N浓度的改变而有较大变化,其中C102在1.6m mol/L时脂肪含量达到最大值(24.8%)。C95的脂肪含量随氮浓度变化不大。同时,由氮浓度引起的平均生长率μ与总脂含量之间无明显相关关系。四株绿藻的EPA(20∶5n-3)和PUFAs(polyunsaturated fatty acids)含量随培养基中氮浓度的改变有较大变化但因种而异。C95和C97均在中等氮浓度时EPA含量达到最大值,分别为23.8%和27.4%。C19和C102在高氮浓度(40mmol/L)获得EPA的最大值,分别为25.7%和26.6%。 相似文献