DOCSLIB.ORG

Dissolved Inorganic Carbon

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Dissolved Inorganic Carbon Lakes: Primary Production, Budgets and Cycling Biogeochemical Systems -- OCN 401 27 September 2012 Reading: Schlesinger Chapter 7 Outline 1. Temperature / density relationship • Seasonal cycle of lake stratification 2. Carbon and nutrient cycling • Dissolved inorganic carbon speciation • Methods of measuring primary production • Nutrients and productivity / nutrient cycling • Carbon budgets • Nutrient budgets • Nitrogen fixation 3. Lake classification 4. Alkalinity and acid rain effects 1 Temperature / Density Relationship • Water is densest at 4°C • Both ice and warmer water are less dense • Important implication: ice floats! • If less-dense water is overlain by denser water, lake overturn occurs • If denser water is overlain by less-dense water, Heavier stable stratification occurs Berner & Berner (1996) Temperature Structure of a Typical Temperate Lake in Summer • Epilimnion: warm surface waters • Metalimnion: zone of rapid temperature change (thermocline) • Hypolimnion: cooler, deep waters • Many tropical lakes are permanently stratified • Temperate lakes show seasonal break-down of temperature stratification 2 Seasonal Cycle of Lake Stratification Early spring (after ice melt): www.gvsu.edu Late spring: 3 Summer: • Dead organic matter sinks from the epilimnion to the hypolimnion • The decay of this organic matter leads to O2 depletion of the hypolimnion Early autumn: 4 Autumn: Winter: 5 Berner & Berner (1996) Temperature profiles over the year for a typical temperate lake Dashed line represents maximum density at 4 C Dissolved Inorganic Carbon (DIC, CO2) Speciation - 2- DIC = CO2 = [CO2 (aq)] + [HCO3 ] + [CO3 ] Bicarbonate Carbonate ion ion CO2 (g) CO2 (aq) + - CO2 (aq) + H2O H + HCO3 - + 2- HCO3 H + CO3 Thus, CO2 speciation is pH dependent: 6 CO2(aq) Seawater values shown --- freshwater curves are shifted left ~0.8 pH aob.oxfordjournals.org Methods of Measuring Primary Production • Collect water sample • Incubate in clear and dark bottles • Measure either: – Change in dissolved oxygen (O2) 14 14 - – Production of C-labeled POC (from C-HCO3 additions) • Calculate results: – Dark bottle: Respiration (for O2 only) – Clear bottle: Net primary production (P-R) – Clear bottle - dark bottle: Gross primary production (for O2 only) 7 Lake Productivity is Linked to Nutrient Concentration Comparison of lakes of the world: (NPP) • Most lakes appear to be P-limited • Other factors can be important (e.g., other nutrients, sunlight) Nutrient Cycling in Lakes • Large proportion of P is in plankton biomass; small proportion is “available” (dissolved in lake water) • Turnover of P in the epilimnion is dominated by bacterial decomposition of organic matter • When planktonic communities are N-limited, there is a shift from green algae to “blue-green algae” (cyanobacteria) that fix N2 8 Export Ratio = percentage of PP that sinks to the hypolimnion: • Export ratio is 10- 50% of NPP • High hypolimnion concentrations of P are returned to the surface during seasonal mixing • Turnover of P is incomplete, so some P is lost to sediments Lake Carbon Budgets • NPP within the lake is “autochthonous” production • Note importance of macrophytes (i.e., rooted plants), which reflects the extent of shallow water in this lake • Organic carbon from outside the lake is “allochthonous” production (12% of total carbon inputs) 9 In lakes with lower chlorophyll concentrations (i.e., lower productivity), respiration exceeds production: • This reflects the increased importance of allochthonous carbon inputs • 74% of organic inputs are respired in the lake • 74% of that respiration occurs in the sediment (Many other lakes have more respiration in the water column) • 7.8% of OC is stored in sediments, similar to rate of accumulation of soil organic matter -- but from a much lower NPP than is typical on lan, due to less efficient anaerobic respiration 10 Lake Nutrient Budgets • Inputs: precipitation, runoff, N-fixation, groundwater • Loses: sedimentation, outflow, release of gases, groundwater • Thus, nutrient budgets require an accurate water budget for the system • Comparison of nutrient residence time with the water residence time gives an indication of the relative importance of internal biotic cycling and physical processes • Most lakes show a substantial net retention of N and P • Lakes with high water turnover, however, may show relatively low levels of N and P storage (Experimental Lakes Area) Most lakes show a net retention of N and P 11 Lake Nutrient Budgets Nitrogen Fixation • Lakes with high rates of N fixation show large apparent accumulations of N • However, the loss of N by denitrification typically far exceeds the input of N by fixation – Denitrification removes fixed N as N2O and (especially) N2 Lake Classification • Oligotrophic lakes are: • low productivity systems • nutrient depleted • frequently geologically young • typically deep, with a cold hypolimnion • Eutrophic lakes are: • high productivity systems • nutrient rich • dominated by nutrients inputs from the surrounding watershed • often shallow and warm 12 Nutrient inputs to oligotrophic lakes are generally dominated by precipitation: Sedimentation tends to convert oligotrophic lakes into eutrophic ones over time…. • Eutrophication: a natural process by which accumulation of sediment causes 1) lake shallowing and 2) a decrease in the volume of the hypolimnion, increasing O2 drawdown: Berner & Berner (1996) • Positive feedback: lower O2, less nutrient retention in sediments, higher productivity, higher rain of organic matter to hypolimnion • Cultural eutrophication: input of nutrients due to human activity accelerates the natural process of eutrophication 13 Alkalinity and Acid Rain Effects • Alkalinity is roughly equivalent to the imbalance in charge from cations and anions: Alkalinity = cations – anions • The charge imbalance is “corrected” by changes in equilibrium in the DIC system - 2- - + • Thus: Alkalinity = [HCO3 ] + 2[CO3 ] + [OH ] - [H ] 2- - • Alkalinity increases by processes that consume SO4 , NO3 or other anions, or that release DIC • Alkalinity decreases by processes that consume cations or DIC + 2- • Acid rain decreases alkalinity due to additions of H and SO4 14 Sensitivity of Lakes to Acid Rain Effects Berner & Berner (1996) Lecture Summary • Physical properties of water, seasonal climate changes, and the surrounding landscape and geology are major controls on nutrient cycling and NPP in lakes • Primary production is closely linked to nutrient supply • Nutrient and carbon budget provide a key means of assessing lake biogeochemical cycling • Eutrophication is a natural process, which can be accelerated by anthropogenic activity • Acid rain has had profound impacts on some lakes; underlying geology is major factor on lake sensitivity 15 .
Load more

Recommended publications
  • Pond and Lake Ecosystems a Pond Or Lake Ecosystem Includes Biotic
    Pond and Lake Ecosystems A pond or lake ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions. Pond and lake ecosystems are a prime example of lentic ecosystems. Lentic refers to stationary or relatively still water, from the Latin lentus, which means sluggish. A typical lake has distinct zones of biological communities linked to the physical structure of the lake. (Figure below) The littoral zone is the near shore area where sunlight penetrates all the way to the sediment and allows aquatic plants (macrophytes) to grow. Light levels of about 1% or less of surface values usually define this depth. The 1% light level also defines the euphotic zone of the lake, which is the layer from the surface down to the depth where light levels become too low for photosynthesizers. In most lakes, the sunlit euphotic zone occurs within the epilimnion. However, in unusually transparent lakes, photosynthesis may occur well below the thermocline into the perennially cold hypolimnion. For example, in western Lake Superior near Duluth, MN, summertime algal photosynthesis and growth can persist to depths of at least 25 meters, while the mixed layer, or epilimnion, only extends down to about 10 meters. Ultra-oligotrophic Lake Tahoe, CA/NV, is so transparent that algal growth historically extended to over 100 meters, though its mixed layer only extends to about 10 meters in summer. Unfortunately, inadequate management of the Lake Tahoe basin since about 1960 has led to a significant loss of transparency due to increased algal growth and increased sediment inputs from stream and shoreline erosion.
    [Show full text]
  • Estimates of Hypolimnetic Oxygen Deficits in Ponds
    Aquacullure and Fisheries Management 1989, 20, 167-172 Estimates of hypolimnetic oxygen deficits in ponds W. Y. B. CHANG Center for Great Lakes and Aquatic Sciences, University of Michigan, Ann Arbor, Michigan, USA Abstract. Shallow tropical integrated culture ponds in the Pearl River Delta. China, have been found to stratify almost daily, with high organic loadings and dense algal growth. The dissolved oxygen (DO) concentration is super-saturated in the epilimnion and is under 2 mg/l in the hypolimnion (>lm). The compensation depth corresponds to twice the Secchi disk depth ranging from 50 to 80cm. As a result, little or no net oxygen is produced in the hypolimnion (> 1 m). The low DO concentration in the hypolimnion causes organic materials, such as unused organic wastes and senescent algae cells, to be incompletely oxidized, since the rate of oxygen consumption by oxidable matter in water is dependent on the dissolved oxygen concentration in water. This material becomes the source of hypolimnetic oxygen deficits (HOD) which can drive whole pond DO to a dangerously low level, should sudden destratification occur. An improved estimate of hypolimnetic oxygen deficits is introduced in this article, and the advantages of this method are discussed. Introduction Oxygen is an important parameter in fish culture, and adequate levels of dissolved oxygen (DO) are essential for maintaining optimum fish growth. Inadequate dissolved oxygen and poor water quality are frequently found in ponds receiving organic wastes and can lead to many serious problems for fish culture in ponds. Problems of low dissolved oxygen are particularly prevalent in ponds during the night and early morning when there are high densities of fish and large additions of organic wastes and feeds (Schroeder 1974; Boyd 1982; Chang 1986).
    [Show full text]
  • Indirect Consequences of Hypolimnetic Hypoxia on Zooplankton Growth in a Large Eutrophic Lake
    Vol. 16: 217–227, 2012 AQUATIC BIOLOGY Published September 5 doi: 10.3354/ab00442 Aquat Biol Indirect consequences of hypolimnetic hypoxia on zooplankton growth in a large eutrophic lake Daisuke Goto1,8,*, Kara Lindelof2,3, David L. Fanslow4, Stuart A. Ludsin4,5, Steven A. Pothoven4, James J. Roberts2,6, Henry A. Vanderploeg4, Alan E. Wilson2,7, Tomas O. Höök1,2 1Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana 47907, USA 2Cooperative Institute for Limnology and Ecosystems Research, University of Michigan, Ann Arbor, Michigan 48108, USA 3Department of Environmental Sciences, University of Toledo, Toledo, Ohio 43606, USA 4Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration, Ann Arbor, Michigan 48108, USA 5Aquatic Ecology Laboratory, Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, Ohio 43212, USA 6Colorado State University, Department of Fish, Wildlife and Conservation Biology, Fort Collins, Colorado 80523, USA 7Department of Fisheries and Allied Aquacultures, Auburn University, Auburn, Alabama 36849, USA 8School of Biological Sciences, University of Nebraska Lincoln, Lincoln, Nebraska 68588, USA ABSTRACT: Diel vertical migration (DVM) of some zooplankters in eutrophic lakes is often com- pressed during peak hypoxia. To better understand the indirect consequences of seasonal hypolimnetic hypoxia, we integrated laboratory-based experimental and field-based observa- tional approaches to quantify how compressed DVM can affect growth of a cladoceran, Daphnia mendotae, in central Lake Erie, North America. To evaluate hypoxia tolerance of D. mendotae, we conducted a survivorship experiment with varying dissolved oxygen concentrations, which −1 demonstrated high sensitivity of D. mendotae to hypoxia (≤2 mg O2 l ), supporting the field obser- vations of their behavioral avoidance of the hypoxic hypolimnion.
    [Show full text]
  • Top-Down Trophic Cascades in Three Meromictic Lakes Tanner J
    Top-down Trophic Cascades in Three Meromictic Lakes Tanner J. Kraft, Caitlin T. Newman, Michael A. Smith, Bill J. Spohr Ecology 3807, Itasca Biological Station, University of Minnesota Abstract Projections of tropic cascades from a top-down model suggest that biotic characteristics of a lake can be predicted by the presence of planktivorous fish. From the same perspective, the presence of planktivorous fish can theoretically be predicted based off of the sampled biotic factors. Under such theory, the presence of planktivorous fish contributes to low zooplankton abundances, increased zooplankton predator-avoidance techniques, and subsequent growth increases of algae. Lakes without planktivorous fish would theoretically experience zooplankton population booms and subsequent decreased algae growth. These assumptions were used to describe the tropic interactions of Arco, Deming, and Josephine Lakes; three relatively similar meromictic lakes differing primarily from their absence or presence of planktivorous fish. Due to the presence of several other physical, chemical, and environmental factors that were not sampled, these assumptions did not adequately predict the relative abundances of zooplankton and algae in a lake based solely on the fish status. However, the theory did successfully predict the depth preferences of zooplankton based on the presence or absence of fish. Introduction Trophic cascades play a major role in the ecological composition of lakes. One trophic cascade model predicts that the presence or absence of piscivorous fishes will affect the presence of planktivorous fishes, zooplankton size and abundance, algal biomass, and 1 subsequent water clarity (Fig. 1) (Carpenter et al., 1987). The trophic nature of lakes also affects animal behavior, such as the distribution patterns of zooplankton as a predator avoidance technique (Loose and Dawidowicz, 1994).
    [Show full text]
  • Phosphorus Relese from Oxic
    PHOSPHORUS RELEASE FROM SEDIMENTS IN SHAWANO LAKE, WISCONSIN by DARRIN HOVERSON A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN NATURAL RESOURCES (WATER RESOURCES) COLLEGE OF NATURAL RESOURCES UNIVERSITY OF WISCONSIN STEVENS POINT, WISCONSIN FEBRUARY 2008 ABSTRACT The release of phosphorus (P) from lake sediments to the water column is important to lake water quality. Previous research on sediment P release has largely been in deeper, stratified lakes where hypolimnetic anoxia can lead to very high sediment P release rates. Recent studies suggest that sediment P release may also be important in large shallow lakes. Sediment P release in shallow lakes is poorly understood, and it is important that lake managers have a better understanding of how it influences lake nutrient budgets. This research developed a P budget for Shawano Lake, a large shallow lake in north central Wisconsin, and used the sediment P release to explain the difference between measured loads and summer P increases in the lake. Laboratory derived P release rates from intact sediment cores taken from littoral areas of Shawano Lake exhibit mean P release rates that are high under anoxic conditions (1.25 mg m-2 d-1) and lower, although still significant, under oxic conditions (0.25 mg m-2 d-1). When compared to the other components of the summer P budget, internal sediment P load accounted for 71% (46% to 81% range) of the summer P budget. This P release could be explained with an oxic P release rate of 0.31 mg m-2 d-1 (0.10 to 0.49 mg m-2 d-1 range).
    [Show full text]
  • Ecological Features and Processes of Lakes and Wetlands
    Ecological features and processes of lakes and wetlands Lakes are complex ecosystems defined by all system components affecting surface and ground water gains and losses. This includes the atmosphere, precipitation, geomorphology, soils, plants, and animals within the entire watershed, including the uplands, tributaries, wetlands, and other lakes. Management from a whole watershed perspective is necessary to protect and maintain healthy lake systems. This concept is important for managing the Great Lakes as well as small inland lakes, even those without tributary streams. A good example of the need to manage from a whole watershed perspective is the significant ecological changes that have occurred in the Great Lakes. The Great Lakes are vast in size, and it is hard to imagine that building a small farm or home, digging a channel for shipping, fishing, or building a small dam could affect the entire system. However, the accumulation of numerous human development activities throughout the entire Great Lakes watershed resulted in significant changes to one of the largest freshwater lake systems in the world. The historic organic contamination problems, nutrient problems, and dramatic fisheries changes in our Great Lakes are examples of how cumulative factors within a watershed affect a lake. Habitat refers to an area that provides the necessary resources and conditions for an organism to survive. Because organisms often require different habitat components during various life stages (reproduction, maturation, migration), habitat for a particular species may encompass several cover types, plant communities, or water-depth zones during the organism's life cycle. Moreover, most species of fish and wildlife are part of a complex web of interactions that result in successful feeding, reproduction, and predator avoidance.
    [Show full text]
  • Metalimnetic Oxygen Minimum in Green Lake, Wisconsin
    Michigan Technological University Digital Commons @ Michigan Tech Dissertations, Master's Theses and Master's Reports 2020 Metalimnetic Oxygen Minimum in Green Lake, Wisconsin Mahta Naziri Saeed Michigan Technological University, [email protected] Copyright 2020 Mahta Naziri Saeed Recommended Citation Naziri Saeed, Mahta, "Metalimnetic Oxygen Minimum in Green Lake, Wisconsin", Open Access Master's Thesis, Michigan Technological University, 2020. https://doi.org/10.37099/mtu.dc.etdr/1154 Follow this and additional works at: https://digitalcommons.mtu.edu/etdr Part of the Environmental Engineering Commons METALIMNETIC OXYGEN MINIMUM IN GREEN LAKE, WISCONSIN By Mahta Naziri Saeed A THESIS Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE In Environmental Engineering MICHIGAN TECHNOLOGICAL UNIVERSITY 2020 © 2020 Mahta Naziri Saeed This thesis has been approved in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE in Environmental Engineering. Department of Civil and Environmental Engineering Thesis Advisor: Cory McDonald Committee Member: Pengfei Xue Committee Member: Dale Robertson Department Chair: Audra Morse Table of Contents List of figures .......................................................................................................................v List of tables ....................................................................................................................... ix Acknowledgements ..............................................................................................................x
    [Show full text]
  • Water-Quality and Lake-Stage Data for Wisconsin Lakes, Water Year 1996
    Water-Quality and Lake-Stage Data for Wisconsin Lakes, Water Year 1996 U.S. GEOLOGICAL SURVEY Open-File Report 97-123 Prepared in cooperation with the State of Wisconsin and local agencies WATER-QUALITY AND LAKE-STAGE DATA FOR WISCONSIN LAKES, WATER YEAR 1996 By Wisconsin District Lake-Studies Team U.S. GEOLOGICAL SURVEY Open-File Report 97-123 A report by the Wisconsin District Lake-Studies Team- J.F. Elder (team leader), H.S. Garn, G.L Goddard, S.B. Marsh, D.L Olson, D.M. Robertson, and W.J. Rose Prepared in cooperation with THE STATE OF WISCONSIN AND OTHER AGENCIES Madison, Wisconsin 1997 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Gordon P. Eaton, Director For additional information write to: Copies of this report can be purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Earth Science Information Center 6417 Normandy Lane Open-File Reports Section Madison, Wl 53719 Box25286, MS 517 Denver Federal Center Denver, CO 80225 CONTENTS Introduction........................................................................ 1 Methods of data collection ............................................................ 4 Explanation of physical and chemical characteristics of lakes................................. 7 Water temperature and thermal stratification........................................ 7 Specific conductance.......................................................... 8 Water clarity................................................................. 9 pH ......................................................................
    [Show full text]
  • Lake Stratification and Mixing
    Lake Stratification and Mixing Many of our Illinois lakes and reservoirs are deep force strong enough to resist the wind's mixing forces enough to stratify, or form "layers" of water with (it only takes a difference of a few degrees Fahrenheit different temperatures. Such thermal stratification to prevent mixing). The lake now stratifies into three occurs because of the large differences in density layers of water—a situation termed summer (weight) between warm and cold waters. Density stratification. The upper layer is a warm (lighter), depends on temperature: water is most dense (heaviest) well-mixed zone called the epilimnion. Below this is a at about 39EF, and less dense (lighter) at temperatures transitional zone where temperatures rapidly change warmer and colder than 39EF. called the metalimnion. The thermocline is a horizontal plane within the metalimnion through the The Stratification Process point of greatest water temperature change. The metalimnion is very resistant to wind mixing. Beneath In the fall, chilly air temperatures cool the lake's the metalimnion and extending to the lake bottom is surface. As the surface water cools, it becomes more the colder (heavier), usually dark, and relatively dense and sinks to the bottom. Eventually the entire undisturbed hypolimnion. lake reaches about 39EF (4EC). As the surface water cools even more, it becomes less dense and "floats" on The most important actions causing lake mixing are top of the denser 39EF water, forming ice at 32EF wind, inflowing water, and outflowing water. While (0EC). The lake water below the ice remains near wind influences the surface waters of all lakes, its 39EF.
    [Show full text]
  • Calculation of the Indiana Trophic State Index (ITSI) for Lakes
    USE OF THE INDIANA TROPHIC STATE INDEX (ITSI) TO GUIDE LAKE MANAGEMENT LAKE AND RIVER ENHANCEMENT (LARE) PROGRAM INDIANA DEPARTMENT OF NATURAL RESOURCES DIVISION OF FISH AND WILDLIFE Eutrophication is a natural process of lake aging, the rate of which can be adversely increased by human activities. Physical, chemical, and biological data gathered on each lake are combined into a standardized multi-metric index known today as the Indiana Trophic State Index (ITSI), a modified version of the BonHomme Index developed for Indiana in 1972. Samples are taken at both the surface (epilimnion) and bottom of the lake (hypolimnion) to identify the effects of stratification on water chemistry. Eutrophy points are assigned to each parameter and totaled to create a final ITSI score ranging from 0 to 75 (Appendix 1). Lower scores indicate lower levels and effects of nutrients on factors related to lake management and use, including water clarity, nutrients available for plant growth and blue green algae dominance. Over more than three decades, the ITSI score has been calculated regularly during July-August at the deepest point in over 600 boat-accessible public lakes and reservoirs, generally on a five-year rotating basis. Since 1989 the sampling and analytical efforts for this program have been conducted for IDEM by the staff and students of the Indiana University School of Public and Environmental Affairs (IU-SPEA). Values are reported every two years in the Indiana Integrated Water Monitoring and Assessment Report (www.in.gov/idem/4679.htm) and are available on a more frequent basis from LARE and IDEM lake program staff.
    [Show full text]
  • Minnesota Lake Water Quality Assessment Report: Developing Nutrient Criteria
    MINNESOTA LAKE WATER QUALITY ASSESSMENT REPORT: DEVELOPING NUTRIENT CRITERIA Third Edition September 2005 wq-lar3-01 MINNESOTA LAKE WATER QUALITY ASSESSMENT REPORT: DEVELOPING NUTRIENT CRITERIA Third Edition Written and prepared by: Steven A. Heiskary Water Assessment & Environmental information Section Environmental Analysis & Outcomes Division and C. Bruce Wilson Watershed Section Regional Division MINNESOTA POLLUTION CONTROL AGENCY September 2005 Acknowledgments This report is based in large part on the previous MLWQA reports from 1988 and 1990. Contributors and reviewers to the 1988 report are noted at the bottom of this page. The following persons contributed to the current edition. Report sections: Mark Ebbers – MDNR, Division of Fisheries Trout and Salmon consultant: Stream Trout Lakes report section Reviewers: Dr. Candice Bauer – USEPA Region V, Nutrient Criteria Development coordinator Tim Cross – MDNR Fisheries Research Biologist (report section on fisheries) Doug Hall – MPCA, Environmental Analysis and Outcomes Division Frank Kohlasch – MPCA, Environmental Analysis and Outcomes Division Dr. David Maschwitz – MPCA, Environmental Analysis and Outcomes Division Word Processing – Jan Eckart ----------------------------------------------- Contributors to the 1988 edition: MPCA – Pat Bailey, Mark Tomasek, & Jerry Winslow Manuscript review of 1988 edition: MPCA – Carolyn Dindorf, Marvin Hora, Gaylen Reetz, Curtis Sparks & Dr. Ed Swain MDNR – Jack Skrypek, Ron Payer, Dave Pederson & Steve Prestin University of Minnesota – Dr. Robert
    [Show full text]
  • Limnology 2008 - 11
    Limnology 2008 - 11 Oxygen in Lakes A. Solubility Oxygen is sparingly soluble in water. At equilibrium with the atmosphere, the maximum concentration of O2 in water (at sea level, 760 mm Hg and at 0 degrees C) is just 14.16 parts per million (0.0014%). In contrast, the concentration of O2 in the atmosphere is nearly 21%. It is therefore not surprising that oxygen is often a serious constraint on the distribution of aerobic organisms in water. Hutchinson (1957): “A skillful limnologist can probably learn more about the nature of a lake from a series of oxygen determinations than from any other kind of chemical data.” p575 1. Henry’s law: The mass of a slightly soluble gas that dissolves in a definite mass of a liquid at a given temperature is very nearly directly proportional to the partial pressure of that gas. This holds for gases that do not unite chemically with the solvent. 2. The equilibrium solubility of oxygen in water is strongly influenced by temperature. (See table 15-1, p227, Kalff) Oxygen concentration, atmospheric pressure 760 mm Hg. Temperature Oxygen concentration at saturation 0 C 14.16 5 12.37 10 10.92 15 9.76 20 8.84 25 8.11 30 7.53 35 7.04 Comment: It is apparent that as water temperature increases, the solubility of oxygen decreases. At the same time, most biochemical processes, including those that lead to the consumption of oxygen, are speeded up at higher temperatures. It is not surprising that elevated temperatures sometimes provoke oxygen stress in aquatic organisms.
    [Show full text]