Limnology Exam 3
Where are high velocities found?
where friction is less, generally at or near the surface and near the center of the channel
Cross-section of a losing stream, typical of arid regions,
where streams can recharge groundwater
The most common and accurate method for measuring current velocity is
with an electronic current meter, or measuring how long it takes a small float to move a certain distance
hydrographs can display
monthly, yearly, daily, or instantaneous discharges
Example of boosting DO conditions in reservoirs
-Air-injection system at El Captain Reservoir at the dam -Air compressor near dam injects compressed air into hypolimnion above dam, thus added O2 to water before it flows through dam
Sinuosity
(referring to a curve, bend, or turn) in a stream can be defined as the ratio of channel length between two points in a channel to the straight line distance between the same two points
Horizontal DO variations
- Can be great, especially in lakes /reservoirs where the photosynthetic production of oxygen by littoral algae/ macrophytes exceed that of limnetic phytoplankton
Positive heterograde pattern
- DO profile with peak (max) oxygen concentration at intermediate depth -characteristic of oligotrophic lakes, in which algal community is so rarefied that light penetrates into metalimnion or hypolimnion -algae often form thin, visible layer (ALGAE PLATE) ~1 meter thick, deep in the lake -Algal/ chlorophyll densities high in plate; algae production oxygen, which tends to at/above saturation - DO concentratio in metalimnion much greater than often super-saturated in relation to levels in epilimnion and hypolimnion -Below plate, DO typically depends decreases sharply with depth. Depth of algal plate depends on depth of thermocline, which depends on factors such as lake size/depth and wind/fetch -Examples: Jack's Lake (Canada)-algal plate ~9m
Improving water quality conditions below TVA Dams. -Problem
- During the summer, a process called thermal stratification occurs in many deep tributary reservoirs and some main-river reservoirs -The water stratifies, or separates, into two layers: a warm surface layer that is rich in DO and a colder bottom layer - Oxygen in the lower layer (hypolimnion) is gradually used up by organic material (which is decomposed by aerobic microbes)- washed into the reservoir when it rains or discharged from sewage treatment plants, industries, and other sources- settles to the bottom and decays - By the end of the summer, DO near the bottom can be entirely depleted
Summer kills
- Rapid decay of massive amounts of aquatic macrophytes &/or phytoplankton can result in marked reductions in DO in small shallow lakes, often killing much of the fish and other aquatic fauna 1. Summer kills most common in highly productive ponds and shallow lakes: a.) toward the end of summer, when many aquatic littoral pants die, their rapid decomposition by microbes can lower DO levels throughout most/all of the lake/pond b.) Hypolimnetic oxygen dipletion followed by storm or wind-induced mixing (anoxic or hypoxic hypolimnion mixes with epilimnetic water, drastically lowering the DO of the entire pond/lake) c.) Extended period of overcast - resulting inadequate amounts of sunlight to support algal production/biomass. (Massive die-offs of phytoplankton, followed by zoolankton ; drastically lowering DO of lake/pond
Reynold's number calculation
- Re+ inertial forces/ viscous forces= Ud/v -U= difference in water velocities and speed of an object in water -d= distance between the two points where U values were measures, or size of object (approximate length or diameter) moving through water -v= kinematic viscosity ~v is a coefficient that represents the physical nature of the water mass ~ v depends on both the viscosity and density of the water ~v= 0.01 cm^2/sec at 20 degrees C
Where is chemical weathering dominated
- in humid regions
How does atmospheric precip influence salinity
- in rivers of arid tropical/coastal regions, atm precip. with a chemical composition similar to sea water is of major importance as a source of salt -These" precip-dominated water"- are typically dominate by NaCl minerals and characterized by low salinities -sea spray carries large amounts of sea water in air
Surface aerators work by:
- increasing the area of contact between air and water (thus increasing diffusion of oxygen from air to water); other types add/pump/inject either air or pure oxygen directly into the water -Many aerators are not intended to aerate the entire ponf, but just a portion that will have higher DO concentrations -WHen the DO is anticipated to reach 3 mg/L or less before sunrise, the aerator is started and the fish move to zone of oxygenated water near aerator
Gyres (gyrals)
- large eddied -100m to 100km diameters -Lake Mendota- sqirl of floating algae provide evidence of eddy -N atlentic ocean- very large eddied where gulf stream rubs against colder coastal water
AMD influenced reaches characterized by
- low fish species richness and abundance
i. Microscopic scale (mm or less)
- water molecules diffuse or move short distances because of their kinetic energy; rate of diffusive movement depends on temperature
Travis Reservoir (Lake Travis),
-5th reservoir down in "Highland lakes" chain on Colorado River in central Texas
Boosting DO levels below TVA Dams -Solution #2
-Aerating turbines -Aerating turbines technology uses low prssure areas to draw air into the water as power is being generates -At some dams, TVA has modified the existing turbines to draw air into the water -At other dams, TVA has installed new turbines specifically designed for this purpose
Solution #7
-Aerating weirs -These are small dams designed to mimic a netural waterfall, adding oxygen to the water as it plunges over the top of the weirs walls -Aerating weirs are located a short distance form dams!! -Weirs also serve to maintain minimum flows when hydrturbines are not operatins -pipes near the bottom of the weir allow slow drainage of water form the weir pool -TVA has designed/built/tested two different kinds 1. infuser weir 2. Labyrinth weir
Solution #6
-At Fort Loudon Dam, TVA used an oxygen-injection system to help maintain adequate DO levels -Perforated hoses suspended above the reservoir bubble gaseous oxygen into the upstream water before its pulled into turbines
Mass Transport:
-At larger scales: above molecular level-water exhibits mass-flow properties that are very different from those of diffusion
acidic waters
-At pH <6, CO2 gas (including H2CO3) is the dominant form of DIC. -Any remaining inorganic carbon is provided by HCO3-. -Such waters have very little buffering capacity.
Boosting DO levels below TVA Dams -Solution #1
-Because conditions are different at each dam, TVA uses a wide range of methods to enhance DO concentrations -In some cases, more than one approach is necessary to reach "DO targets". qhich vary depending on the kind of fishery in the tailwater
Carbon Cycle
-Because it is a basic constituent of all organic compounds and a major element in the fixation of energy by photosynthesis, carbon is so closely tied to energy flow that the two are inseparable. -In fact, the measurement of biotic productivity is commonly expressed in terms of g Carbon fixed per square meter per year. -Source of all fixed carbon, both in living organisms and fossil deposits, is carbon dioxide (CO2), found in the atmosphere and dissolved in waters of the Earth.
Alkalinity
-Because pH is a measure of the concentration of hydrogen ions in a solution, alkalinity represents the ability of a solution to absorb or take up hydrogen ions.
DIC
-Carbon dioxide diffuses into the upper layers of water according to equilibrium reactions that depend on pH. CO2 (air) CO2 (dissolved) + H2O H2CO3 H2CO3 HCO3- + H+ CO32- + H+ -Shifts between these DIC forms are also affected by photosynthetic and respiratory activity of aquatic biota.
Winter cooling of lake surface/ Epilimnion
-Causes downward penetration of cool surface water displacing deeper warmer water upward -Cold water plumes at surface plunge downward, deepening the surface layer and eroding the thermocline -often a dominant mechanism for deep-water mixing
Eddies (horizontal currents)
-Circular turbulence patterns ~ Range in scale from cm to 1000s of Km ~Eddies often occur around rocks/points in streams ~ Strong eddied (10m scale); often occurs in rivers ~Billows- small eddies (cm to m scale) often occur between water layers of different water layers of different densities (ex: water layers, flowing along a thermocline)
3. Heterograde pattern
-DO peak or depression at some intermediate depth -Peak (max DO) occur in intermediate depth - These peaks often occur in the meta- or hypolimnion in oligotrophic lakes -Algal populations so sparse that light penetrates into meta- or hypolmnion - Algae in un-mixed, light hypolimnion flourish, receiving light from above, and nutrients such a phosphate from from sediments -Algae often form a thin, opaque layer (sometimes called agal plate) that is 1m thick and is found deep in lake -Ex: Lake Michigan, layer of algae found at 20m, algal plate found just below the thermocline
Orthograde pattern:
-DO profile where oxygen saturated throughout the water column of lake -Oxygen level below epilmnion remains at/near saturation -If lake is saturated with oxygen at all depths and has a warm epilmnion, a.) it will have a higher DO in the hypolimnion vs. epilmnion b.) (recall, warmer water holds less oxygen the cooler water) c.) orthograde patterns usually seen in spring-early summer in oligotrophic lakes that have recently stratified -Biological activity tends to modify the orthograde pattern
Negative heterograde pattern
-DO profile with sharp reduction in oxygen concentration at an intermediate depth (often in metalimnion) -METALIMNETIC OXYGEN MIN.- Term often used to descrive this pattern, although minimum DO usually occurs in lower epilimnion -Metalimnetic oxygen minimum, showing negative heterograde curve in relation to peak abundance of copepods and temperature (summer stratification), Lake Washington -Possible causes: 1. oxygen removal by decomposition/respiration exceeds input as sedimentation rate of organic matter slows upon encountering colder/denser metalimnion- bacterial decomposition and/orzooplankton respiration related to higher densities 2. Interflow of water with low DO or high organic load -common in reservoirs (ex: intrflows of urban stormwater)
Air-water exchanges of carbon dioxide gas:
-Diffusion of CO2 between air and water surface. -CO2 readily dissolves in water; aquatic systems contain substantially more CO2 than atmosphere.
What is a major threat to fisheries and other forms of aquatic life in acid sensitive lakes in NE US and Canada
-Direct effects on fish result from low pH and dissolved aluminum which is highly toxic to fish, particularly embryos and larvae -Many impacts on fish reproduction start to occur at pH below 6.5
Dissolution and deposition
-Dissolution - carbonates dissolved from compounds in rock/soil. -Deposition - carbonate precipitated from water. -Carbonate compounds usually limestone and dolomite.
Low DO in TVA/s Tributary vs Mainstream Reservoirs
-Dissolved oxygen (DO) is less of a problem below main-river reservoirs (vs tributary reservoirs) because thermal stratification is weaker in mainstream reservoirs -That is because water flows through main-river reservoirs more quickly- usually in days/weeks- and depths are shallower -Main-river reservoirs do experience reductions in DO, however, especially during low-flow conditions
Sources of Dissolved Oxygen (DO) in Inland waters
1. Atmospheric Oxygen 2. Photosynthesis
Boosting Dissolved Oxygen levels: Aerators for farm ponds
-Farm ponds are used for both commercial and recreational purposes -For many years, aerators have been used in commercial aquaculture ponds; however many private/residential farm pond owners are installing aerators in their ponds - Aeration equipment is most commonly used to keep fish alive when DO is low and minimize stress
Diffusion is a significant physical phenomenon in water at small scales: 1 mm or smaller
-Gases dissolve in the surface film of water and diffuse downward -Diffusion of oxygen into water can keep the concentration in the surface film at saturation -However, it would take years for diffusion (acting alone) from the atmosphere into still water -To increase DO concentration by 1 mg?L for any depth more than a few mm
What are the chief agents in chemical weathering
-H+ ions because they are produced when gaseous CO2 combines with water to form carbonic acid
Boosting DO levels below TVA Dams: - The problemL
-Hydroturbine intakes typically draw water from the lower levels (hypolimnion), creating low oxygen conditions downstream of the dam -This can cause problems for fish/other awuatic life, which depends on oxygen as much as terrestrial creatures do
Interpreting values of Reynold's number
-If Re < 1, water (or any fluids) is more distorted than flowing, viscosity is greater than inertial force - If Re > than or equal to 1 & < than or equal to 500, flow will be laminar; moving water will flow smoothly without turbulence
Losing streams
-In arid regions, the water table slopes away from the stream channel. -And streams originating at high altitudes often flow into drier areas where the local water table is below the bottom of the stream channel -Depending on the permeability of materials underlying the stream-bed, the stream may contribute (lose) water to the groundwater
Gaining streams
-In humid regions, the water table slopes toward the stream channel, with the consequence that groundwater discharges into the channel. Discharge from the water table into the stream accounts for baseflow during periods without precipitation.
Thermal bars can occur to some extent in all lakes:
-In small lakes, the phenomenon is transitory, often lasting only a few days -In large lakes, however, the transition to stratification of the whole basin may take weeks, as seen in the example from Lake Ontario
How is photosynthesis a source of DO in inland water bodies?
-It is usually the most important source of DO in ponds, lakes, and the lacustrine zone of reservoirs
Thermal bar moves progressively further from shore as heat influx continues to warm the larger open water mass
-Little mixing occurs between inshore and offshore waters, and a significant portion of the inshore water originates as runoff - Finally, thermal difference between the inshore and offshore regions lessen to the point where stratification of the whole basin occurs -This mechanism results in temporary isolation of inshore waters where, when augmented by surface runoff and river discharges, chemical enrichment can occur -As a consequence, increases productivity and algal booms can occur much earlier in the spring in the inshore region than in the open water
Respiratory impairment/failure
-Loss of oxygen in the tissues is reported as one of the primary causes of fish death in acid water -
Boosting DO levels below TVA Dams - Solution #4
-Low-pressure air blowers -These devices are used to force air into water flowing through a dam
Horizontal Currents
-Mass transport occurs (whether turbulent or laminar flow) with some mixing -Water currents at surface have a velocity ~usually 2% of wind speed ~ typically only a few cm/sec -Wind speeds are usually < then or equal to 1400 cm/sec ~Max wind speed- 1400 cm/sec could create a horizontal -Other causes of horizontal currents ~ streams/springs entering lakes
Reynolds number (Re)
-Mathematical ratio can be used to predict whether a current will be laminar or turbulent RE= ratio of two forces; inertia to viscosity ratio
alkalinity
-Measures concentration of titratable bases (HCO3-, CO3=, OH-, and other bases) -AKA the capacity of water to neutralize effects of strong acids -AKA buffering capacity of water (buffers against acid pollution) -Bicarbonates-carbonates (HCO3-/CO3=) comprise the dominant buffering system in most aquatic ecosystems
Indirect effects cont. -Habitat alteration
-Metal hydroxides can cover the streambed (metal armouring), filling in crevices in rocks and make substrate unit for habitation -scouring of metal floccuent from streambed during high flows may increase turbidity and this may inhibit animal feeding efficiency
Whiting -
-Milky white clouds of CaCO3 crystals observed in certain lakes. -Whiting events lower lake transparency and can affect nutrient cycling through removal of adsorbed organic matter, sorbed plant nutrients, and enhanced sedimentation of algae and other particles.
Circum-neutral Waters (pH 6-8)
-Most freshwater systems have a pH between 6 and 8. -Inorganic buffering against rapid pH changes in such waters is almost exclusively provided by HCO3-, which is abundant in this range. -LOOK AT GRAPH
Thermal bar
-Narrow shallow-water zone of warm water that develops between shoreline (littoral) zone and deeper open-water (limnetic) mass in the spring - In a large lake with a shallow water nearshore zone, the shallow area will warm faster than deeper open waters -Little mixing occurs between inshore and offshore waters until whole lake is thermally stratified
Thermal bar cont.
-Narrow transition zone in certain lakes consisting of a nearly vertical 4 degrees C isotherm that develops between littoral and limnetic water in the spring -Once dimictic lakes become ice-free, the period of spring overturn or circulation begins -More rapid warming of the shallow waters along perimeter, supplemental by inflows of warmer runoff/river water, leads to the development of a thermal ar that is most clearly evident in large lakes ~ Where the warmed (> 4 degrees C), thus lighter, nearshore water meets colder (<4 degrees C) water offshore, mixing produces 4 degree C which being most dense sinks ~ Thermal density differences drive downward flowing currents along the vertical thermal bar into both the lower portions of the inshore and offshore water masses ~ Downward density-mediated currents outside the thermal bar can penetrate to very deep strata or bottom layers and cause appreciable convective mixing
Effects of Acidity on aquatic life?
-Natural waters exhibit a wide range of pH values and in the total amount of dissolved material producing the acidity or alkalinity -Most streams and lakes have pH values between 6 and 9 -Aquatic organisms have ranges of tolerance and optima for pH itself (h+) in addition to many related effects -Ex: certain metals that become toxic at low pH values -Lethal effects for most species occur at pH < 5.5 and pH > 9.5, although the tolerances of most organisms are considerably more restricted within these extremes -The deleterious effects of acidic streamwater on aquatic biota are well established, primarily in terms of reduced numbers of species/individuals
Oligotrophic lake- Summer stratification
-Oligotrophic lakes that exhibit orthograde DO curve usually exhibit an orthograde DIC curve -Vertical pH curves are also relatively homogeneous from surface to bottom
orthograde pattern?
-Oxygen saturated throughout water column -warmer the water, the less oxygen it holds (line of 100% oxygen saturation on graph) -If lake stratified with oxygen at all depths and has warm epilimnion, it will have a higher DO concentration in hypolimnion than in epilmnion -This condition usually seen in spring low-productivity lakes that have recently stratified - Biological activity (photosynthesis, respiration) tends to modify the orthograde pattern
Boosting DO levels -Solution #5
-Oxygen-injection systems -At some reservoirs, oxygen is injected into the water before it enters the dam's intake -The system consists of an oxygen tank and evaporators on the bank that are connected to perforated hosing suspended above the reservoir floor upstream of the dam -It's the same type of hosing used in gardens for irrigation -Gaseous oxygen, instead of water, is pumped through the hosing, creating oxygen bubbles that are releases into the reservoir along the length of the hosing
Energy-transforming reactions
-Photosynthesis (reduction rxn - requires energy) - removes CO2 from water. -Respiration (oxidation rxn - releases energy) - releases CO2 to water. -Energy reactions occur much faster than dissolution/deposition.
Eutrophic lakes- Summer stratification
-Photosynthetic uptake of CO2 by epilimnion phytoplankton tends to reduce DIC and increase pH in the epilimnion -Respiratory production of CO2 throughout the water column/sediments tends to increase DIC and decrease pH -Decomposition is most intense in hypolimnion and sediments, so the amount of CO2 increased markedly in these habitats -Overall, decomposition results in a DIC and a PH decrease in the hypolimnion -Eutrophic lakes exhibit marked declines in hypolimnetic DO -With the accumulation of CO2 and the depletion of DO, microbial decomposition shifts to anaerobic, and the hypolimnion becomes anoxic
source of CO2 in inland waters
-Precipitation falling on the surface of Earth as rain/snow is charged w/ CO2 As it flows over and into the ground, water dissolves more gases, notably more CO2 from respiration/decomposition and various mineral substances w/ which it comes into contact. This water will later enter a stream/lake, introducing gaseous CO2 in solution. Most natural waters contain various bicarbonate compounds. Water rich in CO2, and hence containing some carbonic acid, may dissolve carbonates from the rocks/soil and bring them into solution as bicarbonates. Bicarbonates (HCO3-) are later introduced into the aquatic environment and made available to algae/aquatic plants as source of carbon for photosynthesis. Respiration of plants, animals, and aerobic decomposer bacteria add CO2 to the aquatic environment; anaerobic decomposition of carbohydrates in bottom sediments is another important source of CO2 gas. Such CO2 gas produced within a body of water can cause the dissolution of calcium carbonate (CaCO3 or calcite) lying within the sediments and put it in solution as calcium bicarbonate [Ca(HCO3 )2].
Bicarbonate buffering system?
-Reactions of the bicarbonate buffering system at a given time may be shifting left or right (depending on the quantity of certain dissolved substances), but allowing the pH of the solution to remain relatively unchanged. -For example, if hydrogen ions are added to the solution, they combine with available bicarbonate or (sometimes) carbonate ions causing the reaction to shift to the left, eventually liberating carbon dioxide and water molecules.
Boosting DO levels below TVA dams -Solution #3
-Surface-water pumps -These pumps, resemble big ceiling fans, push warm oxygenated water downstream, where it is mixed with low-oxygen bottom water and then drawn into by the turbines during generation -The pumps are positioned above a dam's intake and mounted on floats attaches to a rail system so they can move up/down as the water level changes -Ex: help pump oxygenated water below Douglas Dam
Temperature
-The solubility of gaseous CO2 decreases with increasing temperature. -So at higher temperatures, gaseous CO2 will diffuse from water to the atmosphere. -During evaporation, CO2 and water are lost and bicarbonate ions are converted into carbonates. -Also, calcium carbonate is less soluble in warm water than in cold water. -Calcium carbonate precipitation often occurs during the summer in shallow littoral waters of productive lakes.
Patterns of Vertical Oxygen Profiles?
-Thermal stratification sets the stage for patterns of chemical stratification in lakes -Oxygen: biologically critical chemical that dissolved in water and shows stratification ~Four patterns of DO variation with depth: 1. Orthograde 2. clinograde 3. positive heterograde 4. negative heterograde
Clinograde pattern?
-Typically occurs during summer stratification -DO in epilmnion at or exceeding saturation ( algal photosynthesis and mixing in epilmnion) - Little/ no DO in hypolimnion ( due to bacterial decomposition in unmixed hypolimnion -Note development of an anoxic hypolimnion during summer in the eutrophic L Mendota
Why are fish dying in Lake Travis?
-Warmer water near the surface and little water movement- both a result of the hot and dry summer- cause oxygen levels to drop 1. A layer of decaying matter (usually algae) sinks as far as it can go. Because the density of the water changes with temperature, the decaying matter doesnt reach the bootm 2. The process of decomposition depletes the oxygen that fish need to survive this layer of water. Sometimes fish swim into/get trapper in this layer and die
Turbulent flow
-Water does not all flow in same direction -Occurs at higher velocities than laminar flow -Small parts of the water mass move in different directions -Observed in almost any water body -Mixes water masses in lakes and streams -Examples: riffles, cascades, whirlpools in streams/rivers
Study og AMD effects on fish assemblages in a Cumberland Plateau stream?
-Water quality conditions and fish assemblages were studied at 12 reaches in this region of TN, which has been impacted byy decades of acid mine drainage (AMD) from abandoned coal mines -The graphs depict the relationship between fish assemblage attributes and mean pH in the North Chickamauga Creek system
Periodic movements (periodic waves)
-Waves occur at surface of both lakes and streams -underwater waves can occur at thermoclines and pycnoclines -Illusion: surface waves seem to be moving across lake or river - Water in waves is mostly moving up/down in periodic motion -most of wave movement is vertical -water mass only moves short distance and then returns to starting position -Visual eample: fishing cork slowly drifts with wind but most of its movement is vertical- up/down bobbing is one place
Chemical stability-
-a measure of tendency for a chemical substance to remain in a given chemical form rather than to react spontaneaously to become a different form
Alkalinity definition
-a measure of the buffering capacity of a solution
Conductivity (specific conductance)
-amount of electrical current that can be conducted between two electrodes spaced 1cm apart -in fresh waters, conductivity is usually expressed as .... -measurement at a standard temperature (25C) is important because conductivity increases with temp
Conductivity cont
-an index of the total amount of dissolved ions in the water
Myxobacteria
-anaerobic bacteria - slender rods with gliding motility
Indirect measures of salinity:
-because measuring total salinity can be a time consuming process, certain indirect measures of salinity are commonly used in inland water ecosystems 1. conductivity (electrical conductivity) 2. Total dissolved solids (TDS)
Silicate rocks account for much larger areas of the earth's surface than do carbonate rocks
-but because carbonate minerals dissolve faster and in greater amounts then silicate minerals, -weathering of limestone accounts for more of the total chemical weathering of the land surface than that of any other rock -Hence, limestone-base waters typically have higher concentrations of ions
During summer stratification, however, the vertical distribution of DIC is strongly influenced by what?
-by certain biologically mediated reactions (such as photosynthesis and respiration)
The same stream can switch between gaining and losing conditions along its course due to:
-changes in in its underlying lithology and local climate, or temporarily due to alteration of baseflow and stormflow conditions
Effect of current velocity on substrate composition
-current velocity , together with available parent material , determines the mineral substrate composition -Speed of the current influences the size of particles in the substrate -The size of the substrate particles that can be eroded/transported increases with current speed
Increasing levels of atmospheric CO2 seem to be the result of
-deforestation -burning fossil fuels (such as peat, oil, and coal)
DIC tends to be uniformly distributed with what?
-depth during seasonal mixing periods in holomictic lakes and in lakes that DONT stratify
Major ions (8 listed above)
-dominate the water of most inland water bodies -usually present in individual concentrations >1 mg/L
Inertia
-force related to momentum (Mass x Velocity) ~Resists viscosity and keeps water moving ~Water with enough momentum changes direction when it encounters a solid surface or when two currents meet ~Inertial forces break current up into patterns of turbulent mixing
igneous rock
-formed by solidification of magma
the critical time for low-oxygen levels (most of time) is?
-from midnight to sunrise
How does leaching/weathering from rock/soil influence salinity?
-in rivers, rocks/soils of the river basins are the predominant source of dissolved materials -" these rock-dominates waters" are characterized by intermediate rainfall/evap, intermediate salinites, and leaching of CaCO3 -most lakes/rivers tend to exhibit a dominance of Ca+ and HCO3- ions
Diffusion At the smallest molecular scales:
-individual molecules in liquid or gas move at high speed at temps in the biological range (between freezing and boiling temps of water) -molecules frequently bump into and rebound off each other -Faster movement, collisions/ricochets result in a random-movement pattern of molecules -Random movement means that as a substance dissolves in water, the substance molecules spread through the water, or diffuse -Rate of diffusion of small molecules is faster at high temps
Viscosity-
-measure of stickiness or internal friction ~Viscous forces tend to keep a mass of water together and moving in same direction ~ maintains laminar flow
total dissolved solids-
-measure of the total concentration of ions dissolved in water (mg/L)
Heat-induced convection currents
-modest vertical currents occur in some lakes with ice cover and no appreciable inflow/outflow -thermally-induced heat flowing from sediments -Heat accumulates in sediments during summer is lowly released from sediments during winter
Laminar flow
-moves fluid without mixing (requires low velocities)
Zero Flow
-point occurs at solid surface (ex: stream bed or lake bed -Just above solid surface, water flows slowly/evenly in a sheet-like manner (called laminar flow)
Weathering rates of minerals range from:
-rapid rates of salt and carbonate minerals at the least stable end -to iron oxides at the most stable end
Indirect effects of Acid. metal impacts on aquatic organisms -Biotic COmmunity-
-reduced trophic base (fewer invert pray for fish) -reduce competition
Limestone minerals calcite and dolomite ae rapidly dissolved in water containing CO2
-resulting salinity dominated by the release of Ca, Mg, nd HCO3 ions
how does evaporation influence salinty?
-rivers of hot, arid regions combined influece intense evaporation and crystallization-precip-sedimentation of CaCO2 from solution -These "evaporation-dominated waters" are dominated by Nal minerals and characterized by very high salinities
Ion-/Osmoregulatory impairment/failure
-sodium loss (from blood/tissue) across gills/respiratory surfaces is one of the primary causes of fish death and other macrofauna in acid water -Organisms that normally inhabit circumneutral waters experience a greater loss of sodium in their blood when exposed to low pH than do acid-tolerant sp
Work performed by a stream is influences the distribution of:
-suspended solids -bed material -particulate organic matter -other nutrients
Gas solubility is
-temperature dependent -declines with increasing temperature.
Stream discharge or flow
-the quantity of water that passes through a cross-section of a channel per unit of time -Discharge yields an indication of the ability of the stream to do work -
Total salinity-
-total concentration of ionic constituents dissolved in water -usually expressed in g/L or ppt in marine systems -usually expressed in Mg/L or meg/L
USGS data can provide information on
-total flow (monthly and daily) -mean monthly discharge -base flow -periods of high and low flow
Reynold's number predictions can be made for:
-two currents of water moving past one another (will they mix?) -Object moving through the water (will it cause turbulence?) -stationary object in the water (will it cause turbulence)
iii. Energy for currents and waves comes from either wind or gravity
-wind: wind blowing across water creates both currents and waves -Gravity: ~causes currents in streams/ground water to flow downhill ~contributes to periodic movement of water disturbed by wind
The pH scale ranges from
0 to 14 and denotes various degrees of acidity and alkalinity.
The DIC pool is of tremendous importance in aquatic systems:
1) Buffers freshwater systems against rapid changes in pH; 2) Regulates biological processes such as rates of photosynthesis and respiration; 3) Carbon can form many different compounds.
Three major classes of processes involved in cycling of carbon in aquatic systems:
1. Air-water exchanges of carbon dioxide gas 2. Energy-transforming reactions 3. Dissolution and deposition
Oxygen needs of aquatic organisms?
1. DO requirements and stress levels 2. Anaerobic micro-organisms
Invertebrate body shapes thought to be adaptive to life in running waters:
1. Dorsoventral compression 2. streamlining 3. Sucker-like
What are 3 physical processes that influence salinity?
1. Evaporation 2. Atmospheric precipitation 3. leaching/weathering from rock/soil
Winter stratification? (distribution of oxygen in inland water ecosystems)
1. Exchange of oxygen with the atmosphere ceases for all practical purposes with the advent of ice formation. 2. DO concentrations are reduced at lower depths in productive lakes, but not to the extent observed during summer stratification, because of prevailing colder winter temps. ( higher solubility; less respiration)
Conductivity is controlled by factors )that affect salinity) such as:
1. Geology of watershed 2. climate 3. distance of water body from the sea 4. watershed size relative to that of lake/river surface area 5. Anthropogenic disturbances
Clinograde DO profiles? (distribution of oxygen in inland water ecosystems)
1. In productive eutrophic lakes, loading of organic matter to the hypolimnion and sediments increases the consumption of DO ( Thus the DO decreases) 2. Consequently, the DO of hypolimnion is reduced progressively during summer stratification, usually most rapidly at deepest part of lake where strata are exposed to more intensive decomposition in surficial sediments 3. Resulting oxygen distribution called a CLINOGRADE DO PROFILE 4. Extreme clinograde DO profiles occur in meromictic lakes, in which the monolimnion may be permanently anoxic
Orthograde DO profiles? (distribution of oxygen in inland water ecosystems)
1. In unproductive oligotrophic lakes that stratify thermally in the summer, the DO content of the epilimnion decreases as the water temp. increases. 2. The DO of hypolimnion is higher than that of epilmnion because saturated colder water from spring turnover (mixing period) is exposed to limited oxidative consumption 3. such a vertical distribution of oxygen called and ORTHOGRDE DO PROFILE
What are resons for low biotic diversity.abundance in acid/metal-polluted water?
1. Increased mortality 2. increased stress 3. decreased growth/reproduction (due to increased stress -> less energy) 4. increases avoidance behavior
Two different kinds of aerating weirs
1. Infuser weir- compact structure that uses slotted decking to create a series of waterfalls 2. Labyrinth weir- long, W-shaped structure that creates a waterfall (at Ute Dam, New Mexico_ -(infuser weir below Chatuge Dam consists of decking made of metal grates. As water falls throught he small openings, it becomes oxygenated)
Physiological effects of increased H+ and metal concentrations
1. Ion-/Osmoregulatory impairment/ failure 2. Respiratory impairment/failure
Anaerobic micro-organisms? (Oxygen needs of aquatic organisms)
1. Obligate ad facultative anaerobic micro-organisms can obtain energy through fermentation in the anoxic environment of the sediments, and hypolimnion of eutrophic lakes, and monimolimnion of meromictic lakes 2. Facultative anaerobes- can exist in the presence or absence of oxygen a.) many fungi and decomposer bacteria b.) These microbes use aerobic respiration when oxygen is available; but in its absence, they can shift to fermentation, utilizing inorganic compounds as an oxidant ex: Denitrifying bacteria are facultative anaerobes that can switch from DO (O2) to Nitrate (NO3) as an alternative electron donor in the oxidation of organic matter as the oxygen depleted 3. Obligate anaerobes - cannot exist in the presence of oxygen a.) certain groups of chemosynthetic, photosynthetic , and decomposer bacteria can grow only in anaerobic environments
Distribution of oxygen in inland water ecosystems:
1. Orthograde DO profiles 2. Clinograde DO profiles 3. winter stratification 4. Metalimnetic oxygen maxima 5. metalimnetic oxyen minima 6. Horizontal DO variations 7. Summer kills 8. winter kills
How is atmospheric oxygen a source of DO?
1. Oxygen enters water through diffusion at the air-water interface 2. Diffusion rate is directly related to: a.) The oxygen concentration gradient at air-water interference b.) Surface area of air-water interference - greater in turbulent waters (not calm) - relatively high in streams ans reservoir tailwaters - In small, turbulent streams that receive only limited pollution , diffusion maintains oxygen and carbon dioxide levels near saturation (In such streams, DO concentrations will change daily/seasonally in response to shifts in temperature, but percent saturation tends to remain near 100%) -Diffusion plays a reduced role in large rivers, because of the smaller surface area relative to volume; an din more smoothly flowing rivers, because of less turbulence
DO requirements and stress levels/ (oxygen needs of aquatic organisms)
1. Oxygen is essential for respiratory metabolism of most aquatic organisms 2. DO levels necessary to prevent mortality differ among species for different life-history stages (within species) a.) Fish eggs and larvae/juveniles, characterized by relatively high metabolic rates, are more sensitive to low DO levels than adults 3. DO concentrations may be above lethal levels, but still may be low enough to cause stress- resulting in impaired growth /reproduction 4. For maintaining healthy fish populations, limited data suggest that waters have DO concentrations of at least ~ 5mg/L for moderately tolerant warm water sp ~ 5-9 mg/L for cold water species (ex: salmon) and warm water species with high oxygen demands 5. The Tennessee Department of Environment and Conservation (TDEC) has a minimum DO criterion for protecting aquatic life: - The DO content of surface waters shall not be <5 mg/L (except under certain circumstances determined on an individual basis) and cant be <3 mg/L under any circumstances 6. Other stresses (Ex: high temps, various pollutants) can increase an organisms' oxygen requirements 7. Community structure of aerobic organisms ( such as amcro-invertabrates and fish) is greatly affected by hypoxic/ anoxic conditions - Prolonged hypoxia (DO< 1.5b-2.0 mg/l) or anoxia (NO DO) is lethal for most aerobic organisms, which do not posses special adaptions 8. many macro-invertebrates and some fish evolved in waters characterized by natural periods of hypoxia/anoxia a.) such organisms have evolved adaptions to survive periods of weeks/months with little/no DO (ex: mosquito fish) b.) The best adapted aerobic species are able to survive periods of hypoxia/anoxia by: -Entering "resting stages" characterized by reduced rates and/or - Anaerobic respiration of glycogen reserves 9. Many lakes and reservoirs at low altitudes may remain anoxic/hypoxic ( usually in hypolimnia) for days-weeks, and wetlands probably remain longer
How are atmospheric and hydrostatic pressure factors that affect DO concentrations in water?
1. Oxygen solubility is directly related (positively correlated) to atmospheric/hydrostatic pressure ; therefore, oxygen solubility inversely related to altitude a.) Oxygen solubility is greater at sea level versus that at higher altitudes which have lower atmospheric pressure s b.) Oxygen solubility increases with greater hydrostatic pressures at greater depths within seas and deep lakes
How is temperature a factor that effects DO concentrations in water?
1. Oxygen solubility is inversely related (negatively correlated) to temperature 2. Physical capacity for H2O to hold oxygen increases as temperature decreases (vice versa) -Ex: 25C -> 8.3 mg/L, 15C -> 10.1 mg/L
How is salinity a factor that affects the DO concentration in water?
1. Oxygen solubility is inversely related to salinity 2. oxygen solubility decreased exponentially as salinity increases - Example: Oxygen solubility is 20% lower in seawater versus freshwater
Physiologial effects of increased H+ and metal concentrations (direct effects of acid/metal impacts
1. Precipiation/polymerization of metals on gills 2. coagulation of mucous on gills (response to acid/metal stress) -coagulation of gill membranes themselves 3.Impaired cell/plasma and enzyme function -Enzymes function within specif pH values and this require that cell plasms pH be held relatively constant. An organism can do this to a certain point. However, this process becomes more difficult for the organism to further the Ph of the surrounding water deviates from the optimal range for the cell for a particular organism 4. Metal hydroxide precipitation -In addition to dissolved metals, precipitates hydroxides of iron, Al or manganese (as well as other metal hydroxides) oftne occur in mining-impacted streams with elevated metal concentrations -Heavy precipitation of certain metal hydroxided may occur in "mixing zone" -Ferrric and Al hydroxided can decrease oxygen availability as they form precipitates the respiratory surfaces of an aquatic organism; precipitats may coat gills and body surfaces, be ingested, smother eggs
Metalimnetic oxygen minima
1. Results in negative heterograde DO curves 2. common occurrence in in reservoirs 3. Several processes have been proposed to explain the cause of metlimnion oxgen minima in lakes and reservoirs a.) Removal by oxygen by decomposition/ respiration exceeds oxygen inputs as the rate of organic matter sedimentation from the epilimnion decreases upon encountering colder, denser metalimnetic water. - Bacterial decomposition of organic matter trapped in the metalimnion can result in oxygen declines in this denser stratum - Respiration by dense populations of zooplankton in the metalimnion can also contribute to oxygen loss in this stratum b.) Interflow of water with either a low DO or a high organic load ( and thus high oxygen demand); this is a common mechanism in reservoirs - interflows, particularly during flood events may bring about metalimnetic oxygen minima due to high oxygen demand associated with increased amounts of oganic matter in highly turbid storm flows -EX: turbid or saline inflow ( more dense water will enter deeper/cooler water with similar density
Salinity can be determined by
1. measuring concentrations of individual major ions -cations (Ca+, Mg+, Na+, K+) -anions (HCO3-, CO3-, SO4-, Cl-) 2. and then summing them
Solution at Watts bar (2 different methods help meet aeartion targets):
1. Since turbines nearest to the banks typically drawn in water that is higher in DO, TVA operates those units first during periods when oxygen levels are low 2. If additional aeration is needed, an oxygen-injection is also available -At Fort Loudon, oxygen can be bubbles into the water through perforated hoses suspended above the reservoir bottom
Chemical stability of a mineral is determined by its:
1. Solubility 2. rate of dissolution
What are the factors that affect the DO concentrations in water?
1. Temperature 2. Atmospheric and hydrostatic pressure 3. Salinity 4. Photosynthesis and respiration
water flows in a stream one of 2 ways
1. laminar flow 2. turbulent flow
Chemical composition and salinity of freshwaters is determined by what?
1. local geology 2. climate (temp, precip, evap) 3. biota 4. length of time soil formation 5. distance from the sea 6. anthropogenic inputs -acid precip or mine drainage -trace metals (elevated in low pH waters) -road salts (higher latitudes) -fertilizers (agricultural, residential)
Metalimnetic oxygen maxima
1. often observed, in which the DO concentration of the metalimnion is much greater than, and often supersaturated in relation to, levels in the epilmnion and hypolimnion 2. The resulting positive heterograde DO profile is usually caused by photosynthetic-oxygen production by algae in excess of oxygen consumption in the metalimnion - When the euphotic zone extends into the metalimnion, a buildup of phytoplankton community may result in a metalimnetic oxygen maxima 3. Other mechanisms causing metalimnetic oxygen maxima include - increased solubility of oxygen in colder waters of metalimnion, with a typical decrease in DO with depth in the hypolimnion -Interflow of more highly oxygenated waters
3 major types of DO patterns?
1. orthograde pattern 2. Clinograde pattern 3. Heterograde pattern
Winter kills
1. oxygen depletion may occur in winter when there is heavy snow cover on the ice 2. Light reduction slows/stops algal photosynthesis 3. if this lasts several weeks, bacterial decomposition and animal respiration can reduce DO below tolerance limits of many organisms (result in fish kills) 4. Winter kills are common in shallow, productive temperate lakes
Human impacts on acidity: Acidification of an aquatic ecosystem requires a combo of two factors
1. poor buffering capacity 2.acid pollution caused by acid deposition or acid mine/ rock drainage
Other possible adaptions for life in fast flow may include:
1. streamlining 2. reduction of projecting structures 3. Development of suckers 4. friction pads 5. hooks/ grapples 6. secretion of adhesive products
Precipitation of calcium carbonate
1. temperature 2. Calcareous springs/seeps 3. photosynthesis
More adaptions for fish in flowing waters
1.) fast swimming fishes that swim in fast currents are usually streamlined 2. Dorsoventrally flattened fish with eyes that are dorsally situated, and paired enlarged/lateral fins 3. oral suckers
ii. At larger scales, water moves in two ways:
1.) mass transport- from one place to another as a current/package 2.) waves or periodic movement- from one place to another and back in a regular manner
Global concentrations of atmospheric CO2 is about
370 ppm by volume
Pure water has a pH around
7; the exact values depend on the temperature.
human impacts on acidity cont
Acid deposition is defined by a low average pH (<5.5-5.7), and includes various forms of wet precipitation (e.g., rain, snow) and dry deposition (e.g., particles containing sulfate or nitrate salts). Sulfuric and nitric acids are the main pollutants. Their acid precursors -- sulfur dioxide (SO2) and nitrous oxides (NOx) - are released from smokestacks of coal-burning electrical facilities, smelters, and steel mills and emitted from trucks/other vehicles.
Al is important in aspect of the problem of acidification of natural waters
Al is one of the most common elements in the earth's crust and found in inexhaustible quantities in the watershed regions of lakes/streams
Acidic waters cont.
At pH <4.5, virtually all DIC is CO2 and H2CO3. Almost no HCO3- can be found. Bicarbonate buffering is negligible.
Alkaline waters
At pH values of 9.0-10.5 recorded in highly productive sewage lagoons and rivers, dense macrophyte beds, and highly buffered and often nutrient-rich saline lakes Buffering is provided by bicarbonates and carbonates (CO3-2). Note that as pH increases above 8.3, bicarbonate levels decline and carbonate increases.
Why do most freshwaters contain bicarbonate alkalinity
Because CO2 is relatively abundant in water in gaseous and dissolved form, and because carbonates are common minerals over wide areas of the Earth
Distributions of DO in thermally stratified lakes is controlled by what?
By a combination of solubility conditions, turbulence due to wind/hydrodynamics, inputs from photosynthesis, and losses to chemical and metabolite oxidations (ex: respirtation)
Marl -
Calcareous sediments, usually soft and littoral, mostly CaCO3.
Hardness properties
Calcium (Ca2+), magnesium (Mg2+) usually principle causes of hardness Calcareous substrates (limestone, dolomite) are dissolved, releasing Ca2+ and Mg2+ Iron, aluminum, manganese, strontium, zinc, and other polyvalent metal cations can contribute to relatively high hardness values; however, high concentrations of these/other trace metal cations are not commonly found in natural waters. Certain anthropogenic disturbances can result in high hardness values. For instance, acid mine drainage often releases large quantities of certain mineral and metal cations (e.g., Fe, Al, Mn) into a stream, resulting in relatively high hardness readings.
Facultative anaerobes
Can exist in the presence or absence of oxygen
Anaeromyxobacteria
Closely related to myxobacteria
Carbon pools usually occur as
DIC > DOC > POC, in order of the relative size of the pools.
Clinograde Pattern
DO profile in which hypolimnion has less oxygen than epilimnion -Results from bacterial decomposition of organic matter in the hypolimnion -In the summer, a stratified productive lake will typically have DO levels near or exceeding saturation in epilimnion and little or no DO in hypolimnion ~This is because phytoplankton supplyoxyge to epilimnion, which is mixed, and decomposition removes oxygen from the unmixed hypolimnion ~ As productivity increases due to algal growth, more organic matter falls into hypolimnion bacterial metabolism of this organic matter can reduce hypolimnetic DO concentrations to zero.
Anthropogenic disturbances can increase concentrations of chemicals, causing them to have significant effects on salinity
Example: NO3- concentrations in agricultural and urban areas are sometimes high enough to make nitrogen a major ion
Calcareous Springs/Seeps -
Groundwater is normally supersaturated with dissolved CO2 from soil respiration. The excess CO2 is lost to the atmosphere where calcareous springs reach the surface. The result is the precipitation of CaCO3, evident from whitish crystalline encrustations on sediments or stones in high alkalinity streams.
Hard water
High concentrations of Ca2+ and Mg2+ derived from carbonates of calcium and magnesium that is generally found in areas of limestone/dolomite substrates Conductivity levels are relatively high
What rock weathers most quickly in humid regions?
Limestone (composed of magnesium carbonate minerals)
Soft water
Low concentrations of Ca2+ and Mg2+ and low conductivity Generally found in areas with sandstone or igneous rock substrates
Despite the small proportion of CO2 among the gases of the air, it's relatively abundant in natural waters.
Major reason for this abundance - its high coefficient of solubility.
rate of dissolution-
Measure of amount of a mineral that dissolves in an unsaturated solution in a given length of time
Diffusion:
Net movement of a substance (ex: atom, molecule) from region of high concentration to a region of low concentration; also described as movement of a substance down a concentration gradient
Anaerobic organisms
Obligate and facultative anaerobic micro-organisms can obtain energy via fermentation in the anoxic environment of the sediments, and hypolimnion of eutrophic lakes, and monimolimnion of meromictic lakes
What are the most important pools of carbon in aquatic systems?
POC, DOC, DIC
POC
Particulate organic matter
How are photosynthesis and respiration factors that affect the DO concentration in water?
Photosynthesis and respiration are the two important biological processes that alter concentration of O2 and CO2 1. Oxygen is ADDED to water by photosynthesis and REMOVED by respiration 2. Diel (24-hour) cycles of O2 and CO2 a.) Photosynthesis occurs only during daylight hours but respiration occurs day and night b.) DO is lowest before sunrise and highest in the afternoon 3. In highly productive lakes - DO levels are typically highest near the water surface and lowest near the bottom - in highly productive waters, such as lakes and slow moving rivers with abundant phytoplankton and aquatic macrophytes, oxygen is elevated and CO2 is reduced during daytime, while the reverse is occurring at night 4. Effects of nutrient/ organic enrichment - The river Thames is a good example of the effect of organic pollution on dissolved oxygen concentrations - Human/ animal waste has been a documented source of foulness since atleast 1620, and 1858 was known as the "Year of the great stink" but the volume of untreated human sewage reduced water quality to an all-time low in the 1950s. (During this time, parts of Thames around London became anaerobic from microbial respiration driven by organic waster)
Water movement processes are
Scale dependent
What are the main pollutants?
Sulfuric and nitric acids
Metalimnetic Oxygen Minimum
Term often used to descrive this pattern, although minimum DO usually occurs in lower epilimnion -Metalimnetic oxygen minimum, showing negative heterograde curve in relation to peak abundance of copepods and temperature (summer stratification), Lake Washington
Gaseous CO2 comes from where?
The atmosphere or respiration
boundary layer
The current velocity diminishes progressively toward the bottom and drops dramatically near the substratum within a 1-3 mm thick area
Discharge, in combination with other factors, influences:
The meander pattern and floodplain dynamics of a river system
Hardness
Total concentration of polyvalent cations expressed as calcium carbonate
Much of hydrological info is maintained by
USGS- Unites States Geological Survey
Photosynthesis -
Upper surfaces of submerged macrophyte leaves in moderate to high alkalinity lakes and wetlands are often encrusted with a CaCO3 precipitate usually attributed to an uptake of CO2 in photosynthesis. (A similar phenomenon often occurs in the epilimnion of certain lakes.) An alternative or complementary explanation for such calcite deposition is that it is the result of a combination of elevated temperature in macrophyte beds and reduced CaCO3 solubility.
Components of periodic waves
Wave height (h): difference in height from crest to trough Wavelength (L)- distance between crests of two waves (crests to crest) Period- time required for a water molecule to complete one vertical cycle- time it takes for one wave to be replaced by another Cycloid path- water of surface waves moves in a cycloid path; water is displaced upward by wind and downward by gravity along a circular path (orbit)
lag time
When the water of a stream does not rise at the onset of precipitation because time is needed for water to move from the place it fell to the stream
Stream invertebrates are often adapted morphologically or in life-history traits to moderate, seasonally predictable spates, but large unpredicatable floods may eliminate all or most of the fauna of a stream by causing bed movement and severely scouring the bottom
When these scouring events occur,the sources for recolonization may be biotic assemblages found in adjacent hyporheic zone, or separate, nearby catchments
Sandstone
a clastic sedimentary rock composed of grains from 0.0625 to 2 mm (feldspar, qartz,etc
anoxia
a total depletion in the level of oxygen,
In calcareous drainage basins,
about half (~50 %) of the HCO3- released to water bodies is derived from weathering (dissolution) of the substrate.
Anaerobic
absence of free oxygen.
The DIC of the water column is infuenced by the addition of what?
additions of CO2 from respiration and removal of CO2 from photsynthesis -Such influences/changes are most pronounced in eutrophic lakes
TDS includes-
all organic/inorganic salts and non-ionized components in the water
Fermentation?
an anaerobic process which converts carbohydrates and other organic mater into CO2 , organic acids, and alcohols. - relatively little energy is gained from fermentation, compared to aerobic respiration
silicate rock
an igneous/ metamorphic rock made up largely of silicate minerals (feldspar, quartz, and mica)
pH
an index of hydrogen ion activity - approximates the negative logarithm (base 10) of the molar concentration of the hydrogen ion (H+) concentration.
clay
any number of hydrous alumniosilicate minerals with sheetlike crystal structures, formed by weathering of other silicates (fragments smaller than 0.0039mm)
Where is physical weathering dominate?
arid regions
Hydrogen ions
increased concentrations of H+ can exert direct and indirect impacts on aquatic orgainsims
Hydrogen ions are taken up by molecules such as bicarbonate and carbonate,
because the negatively charged ions bond with the positively charged hydrogen ions thereby removing them from the solution.
Chemical weathering
breakdown of rock/mineral and resulting in salinity decrease as the chemical stability of the rock/mineral increases -The varying rates at which minerals weather reflect their chemical stability under weathering conditions
In shallow water columns, the mean water column velocity can be estimated by:
measuring current speed at 60% of the depth below the surface
TDS is determined by:
by filtering a water sample, evaporating the filtrate to dryness (<100C) and measureing the dry weight of the major ions plus silica and other remaining constituents
Obligate anaerobes
cannot exist in the presence of oxygen - certain groups of chemosynthetic, photosynthetic, and decomposer bacteria can grow only in anaerobic environments
The DIC pool is defined as the sum of all carbon present as:
carbon dioxide (CO2), carbonic acid (H2CO3), bicarbonate (HCO3-), carbonate (CO32-).
Source of all fixed carbon, both in living organisms and fossil deposits, is
carbon dioxide (CO2), found in the atmosphere and dissolved in waters of the Earth.
Ions in solution are capable of
conducting an electric current.
hypoxia
deficiency in the amount of oxygen reaching the tissues.
Catchment geology
defines chemical composition and salinity of most fW
Rising limb
depicts the increase from base-flow conditions to peak-flow
Recession limb
depicts the return to base-flow conditions
At what depth does the mean current velocity occur in a water column?
depth of 0.6 times the maximum depth
Carbonic acid promotes the
dissolution of limestone as well as the weathering of silicates and other rocks/minerals
DIC
dissolved inorganic carbon
DOC
dissolved organic carbon
TDS is primarily used to
estimate the amount of chemical erosion or weathering of different landscapes -sometiems used as an indicator of potential production -also may be reported as a filterable residue (FR)
It is customary to say that CaCO3 is virtually insoluble
except in the presence of an acid
Ephemeral stream
flows are short-lived or transitory and occur from precipitation, snow melt, or short-term water releases
Intermittent stream
flows at certain times of the year only when groundwater levels are adequate, but may cease entirely in low-water years or be reduced to as a series of separated pools
Perennial stream
flows continuously throughout the year
Cross-section of a gaining stream, typical of humid regions where
groundwater recharges the stream
Carbonate alkalinity may be present when the pH is?
high
peak flow
highest discharge recorded within a specified period- often related to snowmelt or storm events
Baseflow (dry-weather flow)
in a stream is due to groundwater entering the stream channel
Hydrograph
is a continuous record of discharge plotted against time
pH
is a measure of the acidity or alkalinity of a solution
Calcium carbonate
is abundant in soils/rocks, and is the main structural component of certain aquatic organisms (e.g., mollusk shells, coral), but is feebly soluble in water.
Gradient
is the change in the value of a quantity (concentration, pressure, temperature) over a distance
The higher the mineral's solubility
is under weather conditions
Slow chemical weathering-
little goes into solution during initial weathering, initially, most is retained as new, largely insoluble mineral -a large amount of silica and Al are released when the weathered minerals are hydrolyzed to a secondary clay and then to ts elemental components
Hypoxia refers to
low DO conditions
Dissolved metals
low pH has a strong effect on the solubility and speciation of metallic ions, many of which may become toxic to aquatic life in acidified conditions
Solubility-
measure of amount of the mineral dissolved when water reaches the point of saturation
In catchments that are very low in carbonates (e.g., igneous rock) or basins lined with peat (peat bogs),
most of the HCO3- produced is the result of respiratory CO2 production.
"Haline" and "saline"
often used interchangeably but differ based on the origin of the salts.
Chemical reactions of the bicarbonate buffering system (e.g., dissociations of carbonic acid and bicarbonate) and the proportions of different forms of DIC are
pH dependent
physical weathering-
physical processes by which rock is broken up into smaller particles
base flow
portion of the stream discharge derived from groundwater - not the result of runoff
saline
refers to land-derived salts
Haline
refers to ocean-derived salts
Chemical buffering-
resistance of a solution to changes in pH.
Sedimentary rock
rock formed at/near earths surface by settling or precip of material -can be formed from fragments of grains of other rocks -or formed by chemical/biochemical precip of minerals from an aqueous solution
metamorphic rock
rock formed by modifying a pre-existing rock (high pressures and temps)
Example:
rock salt is unstable under weathering conditions; its is highly soluble in water and is leached from a soil by even small amounts of water
Most of the TDS weight is due to
salts present in ionic form
carbonate sedimentary rock
sedim rock formed by accumulation of carbonate minerals precipitated organically/ inorganically -Rocks chiefly limestone and dolomite
Chemical weathering-
set of all chemical reactions that can act on rock exposed to water and the atmosphere and this dissolve the minerals or change them to more stable forms
Weathering-
set of all processes that breakup and decompose rock, by a combination of physical fractures and chemical decomposition
Perennial stream
streams/rivers that continue to flow during periods of no rainfall -much of the water in the channel comes from groundwater
silicates
substances made up of silicon, oxygen, and other elements
storm flow
sudden and temporary increase in stream discharge caused by runoff inputs from precipitation
Relative saturation (or percent saturation)
the concentration of a gas expressed as percentage of the concentration resulting from equilibrium conditions -The saturation of a gas can change as a result of changing conditions, even thought eh actual concentration has not changed -For example: Oxygen saturation in water under equilibrium conditions ( based on solubility constant) and 20 C is 9.09 mg/L; this is equal to 100% saturation - As you increase temperature, but leave the conc. the same, the saturation % increases (or decreases as you decrease the temp)
the faster a mineral dissolves
the lower its stability under weathering conditions
current velocity
the speed of water moving through a channel varies considerably within a stream's cross-section owing to friction with the bottom and sides of the channel, and to sinuosity and obstructions
Igneous (volcanic) rocks-
typically composed of silicates (substances composed of silicon + oxygen + other elements) containing Al, Na, K, or Ca
Precipitation falling on the surface of Earth as rain/snow is charged
w/ CO2
Distribution of these materials has a substantial influence on
water/habitat quality and stream biota
