Limnology and Oceanography
0024-3590
1939-5590
Mỹ
Cơ quản chủ quản: Wiley-Blackwell , WILEY
Lĩnh vực:
OceanographyAquatic Science
Các bài báo tiêu biểu
DETERMINATION OF CHLOROPHYLL AND PHEO‐PIGMENTS: SPECTROPHOTOMETRIC EQUATIONS1
Tập 12 Số 2 - Trang 343-346 - 1967
DETERMINATION OF AMMONIA IN NATURAL WATERS BY THE PHENOLHYPOCHLORITE METHOD 1 1 This research was fully supported by U.S. Atomic Energy Commission Contract No. ATS (11‐1) GEN 10, P.A. 20.
Tập 14 Số 5 - Trang 799-801 - 1969
SPECTROPHOTOMETRIC DETERMINATION OF HYDROGEN SULFIDE IN NATURAL WATERS1
Tập 14 Số 3 - Trang 454-458 - 1969
MEASUREMENT OF THE APPARENT DISSOCIATION CONSTANTS OF CARBONIC ACID IN SEAWATER AT ATMOSPHERIC PRESSURE1 The apparent dissociation constants of carbonic acid in seawater were determined as functions of temperature (2–35°C) and salinity (19–43‰ ) at atmospheric pressure by measurement of K’x and the product K'� K'2. At 35%° salinity and 25°C the measured values were pK ′1 = 6.000 and pK ′2 = 9.115; at 35‰ and 2°C the measured values were pK ′1 = 6.177 and pK ′2 = 9.431.
Tập 18 Số 6 - Trang 897-907 - 1973
UPTAKE OF NEW AND REGENERATED FORMS OF NITROGEN IN PRIMARY PRODUCTIVITY1 The use of 15 N‐labeled compounds to obtain specific uptake rates for the various nitrogen sources available to the phytoplankton makes it possible to separate the fractions of primary productivity corresponding to new and regenerated nitrogen in the euphotic zone of the ocean. Measurements of nitrate uptake as a fraction of ammonia plus nitrate uptake have been obtained from the northwest Atlantic and the northeast Pacific oceans. Mean values range from 8.3 to 39.5%, the former being characteristic of subtropical regions and the latter of northern temperate regions or coastal and inland waters. Nitrogen fixation is also a source of new nitrogen. Rates of nitrogen fixation are found to be as high or higher than nitrate uptake, in some cases suggesting an important role for nitrogen‐fixing phytoplankton. The role of zooplankton in regenerating nitrogen as ammonia in the Sargasso Sea is examined theoretically. Probably only about 10% of the daily ammonia uptake by phytoplankton is contributed by the zooplankton living in the upper 100 m.
Tập 12 Số 2 - Trang 196-206 - 1967
Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity We studied the fluorescence properties of fulvic acids isolated from streams and rivers receiving predominantly terrestrial sources of organic material and from lakes with microbial sources of organic material. Microbially derived fulvic acids have fluorophores with a more sharply defined emission peak occurring at lower wavelengths than fluorophores in terrestrially derived fulvic acids. We show that the ratio of the emission intensity at a wavelength of 450 nm to that at 500 nm, obtained with an excitation of 370 nm, can serve as a simple index to distinguish sources of isolated aquatic fulvic acids. In our study, this index has a value of ~1.9 for microbially derived fulvic acids and a value of ~1.4 for terrestrially derived fulvic acids. Fulvic acids isolated from four large rivers in the United States have fluorescence index values of 1.4–1.5, consistent with predominantly terrestrial sources. For fulvic acid samples isolated from a river, lakes, and groundwaters in a forested watershed, the fluorescence index varied in a manner suggesting different sources for the seepage and streamfed lakes. Furthermore, we identified these distinctive fluorophores in filtered whole water samples from lakes in a desert oasis in Antarctica and in filtered whole water samples collected during snowmelt from a Rocky Mountain stream. The fluorescence index measurement in filtered whole water samples in field studies may augment the interpretation of dissolved organic carbon sources for understanding carbon cycling in aquatic ecosystems.
Tập 46 Số 1 - Trang 38-48 - 2001
Photosynthetic rates derived from satellite‐based chlorophyll concentration We assembled a dataset of 14 C‐based productivity measurements to understand the critical variables required for accurate assessment of daily depth‐integrated phytoplankton carbon fixation (PP (PP eu )u ) from measurements of sea surface pigment concentrations (C sat )(C sat ). From this dataset, we developed a light‐dependent, depth‐resolved model for carbon fixation (VGPM) that partitions environmental factors affecting primary production into those that influence the relative vertical distribution of primary production (P z z P (PB opt ). The VGPM accounted for 79% of the observed variability in Pz and 86% of the variability in PP eu by using measured values of PB opt . Our results indicate that the accuracy of productivity algorithms in estimating PPeu is dependent primarily upon the ability to accurately represent variability in P b opt . We developed a temperature‐dependent P b opt model that was used in conjunction with monthly climatological images of C sat sea surface temperature, and cloud‐corrected estimates of surface irradiance to calculate a global annual phytoplankton carbon fixation (PP annu ) rate of 43.5 Pg C yr‒1 . The geographical distribution of PP annu was distinctly different than results from previous models. Our results illustrate the importance of focusing P b opt model development on temporal and spatial, rather than the vertical, variability.
Tập 42 Số 1 - Trang 1-20 - 1997
Absorption spectral slopes and slope ratios as indicators of molecular weight, source, and photobleaching of chromophoric dissolved organic matter A new approach for parameterizing dissolved organic matter (DOM) ultraviolet‐visible absorption spectra is presented. Two distinct spectral slope regions (275‐295 nm and 350‐400 nm) within log‐transformed absorption spectra were used to compare DOM from contrasting water types, ranging from wetlands (Great Dismal Swamp and Suwannee River) to photobleached oceanic water (Atlantic Ocean). On the basis of DOM size‐fractionation studies (ultrafiltration and gel filtration chromatography), the slope of the 275‐295‐nm region and the ratio of these slopes (S R ; 275‐295‐nm slope : 350‐400‐nm slope) were related to DOM molecular weight (MW) and to photochemically induced shifts in MW. Dark aerobic microbial alteration of chromophoric DOM (CDOM) resulted in spectral slope changes opposite of those caused by photochemistry. Along an axial transect in the Delaware Estuary, large variations in S R were measured, probably due to mixing, photodegradation, and microbial alteration of CDOM as terrestrially derived DOM transited through the estuary. Further, S R varied by over a factor of 13 between DOM‐rich wetland waters and Sargasso Sea surface waters. Currently, there is no consensus on a wavelength range for log‐transformed absorption spectra. We propose that the 275‐295‐nm slope be routinely reported in future DOM studies, as it can be measured with high precision, it facilitates comparison among dissimilar water types including CDOM‐rich wetland and CDOM‐poor marine waters, and it appears to be a good proxy for DOM MW.
Tập 53 Số 3 - Trang 955-969 - 2008
Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments A fluorometric method is described which provides sensitive measurements of extracted chlorophyll a free from the errors associated with conventional acidification techniques. Fluorometric optical configurations were optimized to produce maximum sensitivity to Chl a while maintaining desensitized responses from both Chl b and pheopigments. Under the most extreme Chl b :Chl a ratio likely to occur in nature (1 : 1 molar), the new method results in only a 10% overestimate of the true Chl a value, while estimates from older acidification methods are 2.5‐fold low. Under conditions of high pheopigment concentrations (pheo a: Chl a = 1 : 1 molar), the new method provides Chl a estimates that are equivalent to those determined from the acidification technique. The new simple method requires a single fluorescence determination and provides adequate sensitivity for small sample sizes (<200 ml) even in the most oligotrophic marine and freshwater environments.
Tập 39 Số 8 - Trang 1985-1992 - 1994
Lakes and reservoirs as regulators of carbon cycling and climate We explore the role of lakes in carbon cycling and global climate, examine the mechanisms influencing carbon pools and transformations in lakes, and discuss how the metabolism of carbon in the inland waters is likely to change in response to climate. Furthermore, we project changes as global climate change in the abundance and spatial distribution of lakes in the biosphere, and we revise the estimate for the global extent of carbon transformation in inland waters. This synthesis demonstrates that the global annual emissions of carbon dioxide from inland waters to the atmosphere are similar in magnitude to the carbon dioxide uptake by the oceans and that the global burial of organic carbon in inland water sediments exceeds organic carbon sequestration on the ocean floor. The role of inland waters in global carbon cycling and climate forcing may be changed by human activities, including construction of impoundments, which accumulate large amounts of carbon in sediments and emit large amounts of methane to the atmosphere. Methane emissions are also expected from lakes on melting permafrost. The synthesis presented here indicates that (1) inland waters constitute a significant component of the global carbon cycle, (2) their contribution to this cycle has significantly changed as a result of human activities, and (3) they will continue to change in response to future climate change causing decreased as well as increased abundance of lakes as well as increases in the number of aquatic impoundments.
Tập 54 Số 6part2 - Trang 2298-2314 - 2009