Limnology and Oceanography
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The trace metal composition of size‐fractionated plankton in the South China Sea: Biotic versus abiotic sourcesWe report the elemental composition (P, Si, Al, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) in the size‐fractionated plankton and suspended particulate matter (SPM) in the surface waters of the South China Sea. The sizefractionated plankton were effectively and gently separated by gravity through a novel trace‐metal‐clean filtration device, equipped with 150‐, 60‐, and 10‐µm aperture nets in sequence to concentrate the plankton. P‐normalized metal quotas in the largest fraction, mostly composed of copepods, were close to or slightly lower than the average metal quotas obtained from previous field studies. However, the total metal quotas in the two smaller fractions were 8‐ to 40‐fold higher than the largest one, and they increased with decreasing sizes. The striking correlation between some essential metals and chlorophyll (Chl) in the SPM at the offshore site indicates that the majority of the metals were associated with algae. Nevertheless, the P‐normalized metal quotas also showed positive correlations with abiogenic Al and Mn, indicating that most of the metals associated with phytoplankton were from extracellular inorganic particles. Preliminary evidence suggests that the extracellular metals were originally derived from anthropogenic aerosols, which contain abundant dissolvable trace metals. The metal quotas of the zooplankton assemblages have a fairly consistent value as compared to observations from other regions, but algae larger than 10 mm carry overwhelming amounts of extracellular metals even in offshore areas. The stoichiometry concept for trace‐metal composition in marine plankton assemblages is unrealistic in the field.
Limnology and Oceanography - Tập 52 Số 5 - Trang 1776-1788 - 2007
Bacterioplankton distribution and production in the bathypelagic ocean: Directly coupled to particulate organic carbon export?,A recently published evaluation of bacterioplankton abundance and productivity in the bathypelagic North Pacific suggests that these properties are generally coupled with particulate organic carbon (POC) fluxes. In that analysis, bacterial biomass and productivity were several–fold greater in subarctic than subtropical waters, consistent with the basin–scale distribution of POC flux and suggestive of a sinking POC > DOC > bacteria transformation of the carbon. To test this hypothesis, we sought to determine whether the very strong spatial and temporal gradients in POC flux in the Arabian Sea would force similar deep–ocean gradients in bacterial variables. On both a within and between–cruise basis, there was variability in bacterial abundance and thymidine incorporation in the deep Arabian Sea, but correspondence was equivocal between these variables and several correlates to export: flux of biogenic carbon from the euphotic zone, state of the monsoon, and proximity to productive coastal upwelling zones. However, when annual mean bacterial abundance at 2,000 m was compared with annual POC flux at that depth, a strong correspondence emerged: high annual flux supported high bacterial abundance (such a correspondence was not found for bacterial productivity). This finding suggests that bathypelagic bacterial abundance responds to the long–term mean input of organic matter and less to episodic inputs. A comparative evaluation of the North Pacific revealed that although the bathypelagic bacteria there showed correspondence to deep POC flux, that variable alone would not account for the wide meridional variations in bacterial abundance that have been reported.
Limnology and Oceanography - Tập 48 Số 1 - Trang 150-156 - 2003
DIURNAL CHANGES IN SHALLOW AQUATIC HABITATSDiurnal changes were studied at different times of the year in a variety of Louisiana ponds, swamps, ditches and streams by the following procedure. Collections were made between 0500 and 0600 and between 1500 and 1600 on one day, and at the same times several days later. Each sample was analyzed chemically and biologically. The times chosen measure the approximate high and low values of dissolved substances in the daily chemical cycle. The extent of change in chemical factors and plankton indicated the degree and role of oxidative processes in a shallow habitat, and provided a measure for comparing different habitats. Plankton populations, predominantly protozoa, often changed during the day, and sometimes changed significantly within 2 hr after sunrise. The conditions and organisms found in shallow habitats may thus depend upon the time of sampling.
Limnology and Oceanography - Tập 7 Số 3 - Trang 348-353 - 1962
Các hồ nước như là những báo hiệu của biến đổi khí hậu Dịch bởi AI Mặc dù có cảm nhận chung rằng các hồ nước có thể đóng vai trò như những báo hiệu của biến đổi khí hậu, nhưng hiệu quả của chúng chưa được phân tích một cách đầy đủ. Chúng tôi đã xác định các biến đáp ứng chính trong một hồ nước đóng vai trò là các chỉ số về tác động của biến đổi khí hậu đối với cả hồ và lưu vực. Những biến này phản ánh một loạt các phản ứng vật lý, hóa học và sinh học với khí hậu. Tuy nhiên, hiệu quả của các chỉ số khác nhau bị ảnh hưởng bởi phản ứng khu vực đối với biến đổi khí hậu, đặc điểm của lưu vực và các chế độ trộn lẫn trong hồ. Do đó, các chỉ số cụ thể hoặc tổ hợp các chỉ số sẽ hiệu quả hơn đối với các loại hồ và khu vực địa lý khác nhau. Việc rút ra tín hiệu khí hậu cũng có thể trở nên phức tạp hơn do ảnh hưởng của các thay đổi môi trường khác, chẳng hạn như sự phì nhiêu hóa hoặc axit hóa, cũng như các hiện tượng nghịch đảo tương đương, bên cạnh các ảnh hưởng từ sử dụng đất khác. Tuy nhiên, trong nhiều trường hợp, các yếu tố gây nhiễu có thể được xử lý thông qua các công cụ phân tích như loại bỏ xu hướng hoặc lọc. Các hồ nước là những báo hiệu hiệu quả cho biến đổi khí hậu vì chúng nhạy cảm với khí hậu, phản ứng nhanh chóng với sự thay đổi, và tích hợp thông tin về các thay đổi trong lưu vực.
Limnology and Oceanography - Tập 54 Số 6part2 - Trang 2283-2297 - 2009
#biến đổi khí hậu #hồ nước #chỉ số môi trường #lưu vực #phản ứng sinh học #phì nhiêu hóa
Nutrient limitation of phytoplankton in freshwater and marine environments: A review of recent evidence on the effects of enrichment
Limnology and Oceanography - Tập 33 Số 4_part_2 - Trang 796-822 - 1988
DISTRIBUTION OF n‐PARAFFINS IN MARINE ORGANISMS AND SEDIMENT1Twelve species of benthic algae from the northeast coast of the United States, three species of planktonic algae grown in the laboratory, a pelagic alga, a sample of mixed phytoplankton and zooplankton, and a recent marine sediment were analyzed for their normal paraffin distribution from C14 H30 to C32 H66 . Normal paraffins occurred in all samples. Benthic and planktonic algae and the mixed plankton sample exhibited only a slight odd‐carbon predominance. All algae showed a major maximum at n ‐C15 H32 or n ‐C17 H36 , a minimum between n ‐C18 H38 and n ‐C31 H44 and a secondary maximum between n ‐C27 H56 and n ‐C30 H62 . In all these features, the algae and the plankton differed from recent marine sediments. This suggests that the normal paraffins of recent marine sediments are largely derived from sources other than the organisms studied. Differences in the hydrocarbon distribution patterns of various classes of benthic algae may be of taxonomic value. Pristane occurs in several benthic and planktonic algae; phytane, if present, occurs at a concentration too low to be detected by the method used.
Limnology and Oceanography - Tập 12 Số 1 - Trang 79-87 - 1967
Benthic community—water column coupling during the 1982‐1983 El Niño. Are community changes at high latitudes attributable to cause or coincidence?1The 1982–1983 El Niño generated a strong signal which diminished poleward. Although water mass properties were clearly influenced at 48°N, no effects were identified on a rocky intertidal community which could unambiguously be attributed to El Niño. The analyses included long term studies of the upper limits to the distribution of a red alga (7 years) and two species of mussels (14 years). No effect was identified on the recruitment, mortality, or growth of a brown alga, Postelsia. Major sea urchin recruitments have occurred on the Washington outer coast four times in the last 22 years, only two of which have been El Niño events, although all were in years of warmer than average water. Major (extreme) episodes of mussel bed disruption occurred immediately after the latest El Niño, but also during a cold water winter (1975–1976). The data suggest that it is difficult to distinguish the influence of even a potentially strong perturbation against a biologically variable background when a long term data base exists.
Limnology and Oceanography - Tập 31 Số 2 - Trang 351-360 - 1986
Mechanical adaptations of a giant kelpUnusually high extensibility of the kelp Nereocystis luetkeana minimizes breakage by waves and tidal currents. Cellulose fibrils in cortical cell walls have a preferred angle of 60° to the stipe axis; this may be the structural basis of stipe extensibility. Although undamaged plants can sustain drag due to most waves and tides, breakage of single plants occurs most often at flaws in the stipes caused by sea urchin grazing or by abrasion.
Limnology and Oceanography - Tập 22 Số 6 - Trang 1067-1071 - 1977
From Greenland to green lakes: Cultural eutrophication and the loss of benthic pathways in lakesBenthic community responses to lake eutrophication are poorly understood relative to pelagic responses. We compared phytoplankton and periphyton productivity along a eutrophication gradient in Greenland, U.S., and Danish lakes. Phytoplankton productivity increased along the phosphorus gradient (total phosphorus [TP] = 2–430 mg m−3 ), but whole‐lake benthic algal productivity decreased, substantially depressing increases in primary productivity at the whole‐lake scale. In shallow, oligotrophic Greenland lakes, periphyton was responsible for 80–98% of primary production, whereas in Danish lakes with TP > 100 mg m−3 , phytoplankton were responsible for nearly 100% of primary production. Benthic contributions ranged from 5 to 80% depending on morphometry and littoral habitat composition in lakes with intermediate phosphorus concentrations. Thus, eutrophication was characterized by a switch from benthic to pelagic dominance of primary productivity. Carbon stable isotope analysis showed that the redistribution of primary production entailed a similar shift from periphyton to phytoplankton in the diets of zoobenthos. Benthic and pelagic habitats were energetically linked through food web interactions, but eutrophication eroded the benthic primary production pathway.
Limnology and Oceanography - Tập 48 Số 4 - Trang 1408-1418 - 2003
Linkages among the bioreactivity, chemical composition, and diagenetic state of marine dissolved organic matterBacterial growth and the chemical composition of dissolved organic matter (DOM) were followed during a 10ߚd decomposition experiment with fresh, algalߚ;derived DOM from an Arctic ice floe. During the experiment ~30% of the dissolved organic carbon (DOC) was used by bacteria, indicating the highly reactive nature of this fresh DOM. Over half of the DOC consumption was accounted for as losses of combined neutral sugars and amino acids. The initial composition of the DOM was characterized by high neutral sugar (14% DOC) and amino acid (7.4% DOC) yields and the dominance of glucose (~75 mol%) and glutamic acid (~25 mol%). During microbial degߚradation the neutral sugar and amino acid yields decreased, and the molecular composition of the DOM became more uniform. The relatively constant abundance of D amino acids and the dramatic changes in the neutral sugar and amino acid compositions indicated that bacteria were important in shaping the chemical composition of marine DOM by selectively removing bioreactive components and by leaving behind biorefractory components. Based on principal component analysis and other parameters, neutral sugars and amino acids were found to be excellent indicators of the diagenetic state and bioavailability of marine DOM.
Limnology and Oceanography - Tập 46 Số 2 - Trang 287-297 - 2001
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