Dissolved organic material in dry valley lakes: A comparison of Lake Fryxell, Lake Hoare and Lake Vanda

McKnight, Diane M.; Aiken, George R.; Andrews, E. D.; Bowles, E. C.; Harnish, R.A.

doi:10.1029/ar059p0119

Cited by 26 publications

(20 citation statements)

References 19 publications

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“…These findings suggest that the solute profiles, including the DOC profile, are the result of the addition of dissolved solutes to the deep water of the lake via advection of modified surface water in addition to diffusion. We also have estimated the flux of DOC and humic substances from streams to the lake and found that, depending on the age of the lake, streamflow may be a significant source of organic matter in the lake (McKnight et al 1993). In light of these findings, in this paper we examine in more detail the nature and distribution of DOC and aquatic humic substances in Lake Fryxell.…”

Section: Introductionmentioning

confidence: 96%

Geochemistry of aquatic humic substances in the Lake Fryxell Basin, Antarctica

et al. 1996

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Abstract. Dissolved organic carbon (DOC) in Lake Fryxell, 10 streams flowing into the lake, and the moat surrounding the lake was studied to determine the influence of sources and biogeochemical processes on its distribution and chemical nature. Lake Fryxell is an amictic, permanently ice-covered lake in the McMurdo Dry Valleys which contains benthic and planktonic microbial populations, but receives essentially no input of organic material from the ahumic soils of the watershed. Biological activity in the water column does not appear to influence the DOC depth profile, which is similar to the profiles for conservative inorganic constituents. DOC values for the streams varied with biomass in the stream channe1,and ranged from 0.2 to 9.7 mg CIL. Fulvic acids in the streams were a lower percentage of the total DOC than in the lake. These samples contain recent carbon and appear to be simpler mixtures of compounds than the lake samples, indicating that they have undergone less humification. The fulvic acids from just above the sediments of the lake have a high sulfur content and are highly aliphatic. The main transformations occurring as these fractions diffuse upward in the water column are 1) loss of sulfur groups through the oxycline and 2) decrease in ali hatic carbon and increase in the heterogeneity of aliphatic moieties. The fraction of modem ' C content of the lake fulvic acids range from a minimum of 0.68 (approximately 3000 years old) at 15m depth to 0.997 (recent material) just under the ice. The major processes controlling the DOC in the lake appear to be: 1) The transport of organic matter by the inflow streams resulting in the addition of recent organic material to the moat and upper waters of the lake; 2) The diffusion of organic matter composed of relict organic material and organic carbon resulting from the degradation of algae and bacteria from the bottom waters or sediments of the lake into overlying glacial melt water, 3) The addition of recent organic matter to the bottom waters of the lake from the moat.

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Section: Introductionmentioning

confidence: 96%

Geochemistry of aquatic humic substances in the Lake Fryxell Basin, Antarctica

et al. 1996

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“…Additionally, the lakes are virtually closed systems owing to the permanent 4-to 5-m ice cover, lack of outflow, and relatively low inflow. Although ഠ20% of the DOC pool in Lakes Fryxell and Hoare is comprised of lowmolecular-weight fulvic acid that is microbial in origin (McKnight et al , 1993, the remainder of the bulk DOC pool of these lakes is relatively high-molecular-weight DOC that is presumably recalcitrant. Phytoplankton extracellular release (ECR) and upward diffusion from the nutrient-rich hypolimnia (Howes et al 1992;Priscu 1995) are believed to be the two dominant mechanisms that supply new DOC to the trophogenic zone of the lakes.…”

Section: Bacterial Dissolved Organic Carbon Demand In Mcmurdo Dry Valmentioning

confidence: 99%

“…Although grazing and viruses are important in Taylor Valley Lakes (Laybourn-Parry et al 1997;James et al 1998;Kepner et al 1998), we are presently unable to estimate the DOC contribution made by these groups of the food web. The low-molecular-weight fraction of DOC in the lakes (20% of the DOC pool) is presumed to be relatively labile and important to BP in these lakes (McKnight et al , 1993. The turnover time of water-column DOC ranged from 46 to 407 yr, or from 9 to 82 yrs if only 20% of the DOC was assumed to be utilizable.…”

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confidence: 99%

“…Our diffusion coefficient is similar to the one used to predict chlorofluorocarbon (CFC) concentration profiles in Lakes Fryxell and Hoare (4.93 ϫ 10 Ϫ5 m 2 d Ϫ1 ; Tyler et al 1998) if the molecular mass of CCl 3 F (137 Daltons) is taken into account. Lake Fryxell sediment pore-water DOC is of a different composition than deep-water DOC and is a significant source of DOC to Lake Fryxell and presumably the other lakes McKnight et al 1993). DOC flux from sediment pore water was calculated as in Eq.…”

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confidence: 99%

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Bacterial dissolved organic carbon demand in McMurdo Dry Valley lakes, Antarctica

Takacs

Priscu

McKnight

2001

Limnology & Oceanography

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The proximal substrate source of planktonic bacteria is dissolved organic carbon (DOC), and the combined sources of DOC (bulk, phytoplankton production, and advected) set an upper limit on how much C is available for bacterial respiration (BR). We compared measurements of bacterial production (BP) and estimates of BR to measurements of what we assumed to be the major DOC inputs for three permanently iceߚcovered lakes in Antarctica: Lakes Fryxell, Hoare, and Bonney. These measured inputs, which included phytoplankton extracellular release (ECR), stream input, and upward diffusion of DOC across the chemocline, sediments, and benthic microbial mats, were three to eight times smaller than planktonic BR, suggesting that a major source of bacterial C was unaccounted for. Despite overestimating DOC and doubling bacterial growth efficiency (BGE), BR in the lakes was 1.25ߚ2 times greater than our estimate of DOC supply. We hypothesize that a major source of organic C for planktonic bacteria in these lakes comes from drawdown of bulk DOC and/or decomposition of particulate material.

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“…The only way biological processes can contribute a net source of O2 in the lake is by the removal of biologically produced organic material, either via liftoff mat (microbial mat which leaves the lake after freezing into the ice cover) or by burial in the sediments (Wharton et al 1986). Because there is very little exogenous organic matter carried into the lake (McKnight et al 1993), there is no biological net sink for OZ. Biological cycling of O2 may alter the efficiency of other loss terms by affecting the O2 concentration locally or seasonally.…”

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confidence: 99%

Sediment oxygen profiles in a super‐oxygenated antarctic lake

Wharton

Meÿer

McKay

et al. 1994

Limnology & Oceanography

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Perennially ice-covered lakes arc found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to tcmperatc lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of 0, at supersaturated levels in certain portions of the water column. Here we report the first sediment 0, profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment 0, profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photopcriod and benthic primary production in sediments overlain by a highly oxygenated water column.

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Dissolved organic material in dry valley lakes: A comparison of Lake Fryxell, Lake Hoare and Lake Vanda

Cited by 26 publications

References 19 publications

Geochemistry of aquatic humic substances in the Lake Fryxell Basin, Antarctica

Geochemistry of aquatic humic substances in the Lake Fryxell Basin, Antarctica

Bacterial dissolved organic carbon demand in McMurdo Dry Valley lakes, Antarctica

Sediment oxygen profiles in a super‐oxygenated antarctic lake

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