Spatial and temporal distribution of dissolved oxygen in Crater Lake,Oregon

Abstract

Small temporal and spatial variations in the distribution of dissolved oxygen in Crater Lake, Oregon, are used to estimate the mean age of the lake's deep water, the flux of labile organic carbon to the deep lake, and the influence of hydrothermal activity on the concentration of dissolved oxygen within the lake. An increase in the concentration of dissolved oxygen in the deep water during winter [1988][1989] indicates that 30-45% of deep water was replaced with well-oxygenated surface water. This deep-water renewal corresponds to a mean deep water residence time of 2-4 yr. The deep-water oxygen consumption rate is 2 l-26 pmol m-3 d-l, which occurs primarily through the oxidation of organic matter and, to a lesser extent, the oxidation of reduced inorganic species that are introduced to the lake via subsurface hydrothermal springs.Dissolved oxygen is a sensitive tracer of the physical and chemical processes occurring in an aquatic system. Oxygen in excess of atmospheric saturation in the upper water column is caused by photosynthesis, in situ warming of the water column by penetration of solar radiation, and air bubble injection (Jenkins and Goldman 1985;Emerson et al. 199 1). The decrease (consumption) in dissolved oxygen at depth typically results from oxidation of particulate organic material raining out of the euphotic zone. If the photosynthetic component of the oxygen excess in the upper water column is properly constrained, then this component should have nearly the same value, but opposite in sign, as the amount of oxygen consumed in deep water. This balance between surface excess photosynthesis and deep-water respiration assumes that only a small portion of the photosynthetically derived carbon is buried in sediments.Because of the consumption of oxygen at depth in an aquatic system, deep water is generally undersaturated with respect to atmospheric saturation. In temperate lakes, oxygen-rich wintertime surface water mixes with deep water, resulting in a net increase in dissolved oxygen at depth at the time of mixing. This change in oxygen pro- AcknowledgmentsMark Buktcnica, James Milestone, John Salinas, and Scott Stonum provided day and night field support for this research; their efforts arc greatly appreciated. The field and analytical efforts of the OSU research team were invaluable. Eric Olsen and Marv Lilley provided the unpublished methane data. Special thanks are extended to Roberta Conard and Chris Moser.

Representative Freshwater Bacterioplankton Isolated from Crater Lake, Oregon

“…Bacterioplankton concentrations at 15, 130, 300, and 500 m were determined to be 2.4 ϫ 10 5 , 3.5 ϫ 10 5 , 1.3 ϫ 10 5 , and 0.7 ϫ 10 5 cells/ml, respectively. Lake temperature below 100 m is approximately 3.5°C year-round and from 4 to 17°C at the surface, and dissolved oxygen is present throughout the water column (25,28,44). In an attempt to mimic natural conditions, cultures were initiated aerobically at 4, 10, and 15°C in the dark.…”

“…It is the deepest lake (589 m) in the United States and is remarkably clear, with primary productivity limited by nitrogen and trace metal availability. An ongoing NPS commitment to research at Crater Lake has resulted in a wealth of readily available limnological data (24,25,27,28). A detailed description of Crater Lake's bacterioplankton community based on 16S rRNA gene cloning and in situ hybridization was published in 2001 (44).…”

Unusual bacterioplankton community structure in ultra‐oligotrophic Crater Lake

“…Chlorophyll concentrations were determined by fluorometry from samples collected onto 0.45-m pore-size filters (Milli- pore), extracted with 90% (v/v) acetone, and total P values were determined by the ascorbic acid method after persulfate digestion (American Public Health Association 1985). Dissolved oxygen concentrations were determined by the modified azide Winkler technique (McManus et al 1996). Phytoplankton were preserved with Lugol's solution and concentrated by gravity settling (96 h total).…”

“…Zooplankton were diluted with lake water prefiltered through 0.2-m pore-size filters, preserved with 4% formaldehyde/4% sucrose, concentrated by gravity settling (24 h), and counted by means of an inverted microscope (Larson et al 1996b). Zooplankton weight conversion factors were estimated for each taxon from dried animals and were used to convert organism densities to units of biomass per unit volume (Larson et al 1993). Bacterioplankton cell densities were determined for cells preserved in 2% formaldehyde, stained with 4Ј6Ј-diamidino-2-phenylindole (DAPI), and examined by fluorescence microscopy (Porter and Feig 1980).…”

Contribution of entrainment and vertical plumes to the winter cascading of cold shelf waters in a deep lake

“…Deep mixing events associated with winter cooling ventilate and oxygenate deep lake waters. McManus et al (1996), for example, report oxygen budget studies of Crater Lake, Oregon, which yield a mean residence time of 2-4 yr for the deep water, which is partially mixed with surface waters each year. Deep mixing also imports nutrients, which are critical to primary productivity, into the euphotic zone (Crawford and Collier 1997).…”