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141 Cards in this Set
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Reduction-oxidation potential
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AKA redox.
Eh. The electrical voltage that exists between two electrodes, one made of hydrogen and the other of the material under study. Describes the change in the oxidation state of metal ions and some nutrients. |
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What is the redox potential of most lakes at neutral pH and 25 degrees celsius?
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500 mV
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How is redox potential related to pH and oxygen concentration?
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Redox decreases by 58 mV per 1 pH unit increase
Reduction in oxygen saturation from 100% to 10% decreases redox by 30 mV. |
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The role of Iron in redox
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Iron is an important substance that undergoes redox reactions that affects the variability of nutrients.
Under oxidizing conditions, E7 > 200, Ferric iron (Fe3+) exists and it is visible on sediments as a light brown orange color. Under reducing conditions, E7 < 200, ferrous iron (Fe2+) exists, giving sediments a black color. |
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What compounds are present in oxidizing conditions?
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Oxidized forms of metals (Fe), oxidized forms of nutrients like NO2, NO3, SO4, Fe3+ salts
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Reducing conditions favor which kinds of compounds?
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Ammonia, Fe2+ salts and sulfides
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Reduced microzone
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Formed at sediment water interface where most of redox reactions occur.
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Most redox reactions are carried out by...
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Bacteria, which gain energy from converting substances to the thermodynamically favored state as oxygen concentrations and redox potentials change.
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Oxidized Microzone
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Important because ferric Fe3+ is produced which binds with phosphate as an insoluble oxide, trapping iron and phosphorus in the sediments
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Low oxygen concentrations near the mud water interface...
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lower the redox potential and releases nutrients such as PO43- and reduced Fe2+
Occurs in lakes with a clinograde oxygen profile. |
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Major nutrients
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Nitrogen (N), Phosphorus (P), Sulfer (S), potassium (K), magnesium (Mg) and calcium (Ca)
MgP SCaNK |
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Minor Nutrients
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Fe, Mn, Si, B, Mo, Zn, Cu, Co, Na - all of which are required in trace amounts
SiB CuZn MoMn CoFeNa |
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DOC
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dissolved organic carbon
Important regulator of micronutrient availability through its complexing (chelating) abilities Complexing by DOC may increase the availability of many micronutrients |
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Solubility and availability of inorganic nutrients is dependent on
1. 2. |
1. Ionic form, which is a function of pH and redox (Fe dynamics)
2. Complexing with dissolved organic carbon (DOC) |
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Micronutrients are toxic in excess. An example:
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Cu is a micronutrient but also a well known herbicide used to control algal blooms
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Typical Iron Levels in Lakes
Consists of 4 things |
50 to 200 micrograms
1. Fe(OH)3 2. Organically bound Fe (to DOC) 3. Adsorbed to particles 4. Particulate Fe |
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How is iron important in organic metabolism?
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Required in enzymatic pathways (cytochromes) of chlorophyll and protein synthesis,
and in respiratory metabolism (hemoglobin) |
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What is the manganese concentration in water?
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Ranges from 10 to 850 micrograms/liter.
Average 35 micrograms/liter |
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How is Manganese an important biological element? (2)
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It is essential for the assimilation of nitrate in photosynthesis
It is a catalyst for many enzyme-mediated metabolic reactions. |
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State of Iron in epilimnetic conditions
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epilimnetic conditions:
pH 5-8 well oxygenated E7 >= .56 V Most Fe is found as ferric hydroxide (practically insoluble) Thus, availability of Fe in trophogenic zone is limited Fe(OH)3 exists mainly as in flocculent suspension, which will remain on .5 micrometer pore size. |
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Fe can form a finer precipitate with colloidal properties that will go through...what size pores
properties of particles |
.5 micrometer pores
Positively charged, except at high pH, and will attract negatively charges particles such as phosphate (PO4 3-), clay particles, organic ions (COOH-) |
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Fe-P interaction
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Under oxygenated conditions, such as in the epilimnion or at overturn, ferrous (Fe2+) is oxidized to ferric (Fe3+)
Fe3+ forms Fe(OH)3 or FePO4 if phosphate is present Some PO4 3- is also adsorbed on Fe(OH)3 colloid Both are relatively insoluble and precipitate out of solution |
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Fe-P interaction, cycling in lakes with clinograde oxygen curves
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1. Ferric iron is reduced to ferrous which is more soluble, freeing phosphate - this reduction usually occurs at the sediment water interface.
2. The Fe concentration in the hypolimnion increases throughout stratification, but is undetectable in the epilimnion 3. The hypolimnion operates as an Fe trap. At overturn, water column is oxygenated, oxidizing Fe2+ to Fe3+ and liberating PO43-, which is mixed throughout the water column causing a fall algal bloom PO43- rapidly forms FePO4 or becomes adsorbed to Fe(OH)3 |
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Phosphorus is not needed in large quantities for growth, but is a limiting element for three reasons:
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1. phosphorus containing minerals are scarce geochemically, so normal nutrient supply form rock breakdown will be phosphorus poor.
2. No gaseous phase of phosphorus 3. Reactive enough to be tightly bound to soils |
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List three types of phosphorus that are normally measured:
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1. Particulate phosphorus (PP)
2. Soluble phosphate (SP) 3. Dissolved total phosphorus (TP) |
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Particulate phosphorus (PP)
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remains on .45 micrometer filter, includes organic and inorganic forms of P, e.g.:
organisms (bacteria, plant, animal) minerals such as hydroxyapatite phosphate adsorbed on clay phosphate adsorbed on dead organisms |
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Soluble Phosphate (SB)
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Filtrate that goes through .45 micrometer filter:
consisting of orthophosphate (PO43-) Polyphosphates (including detergents) colloidal phosphorus (large molecular aggregations that disperse slowly if at all Low MW P-esters |
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Dissolved total Phosphorus (TP)
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90% is PP and 10% is SP
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Soluble phosphorus consists of two fractions:
1. 2. |
1. Soluble reactive phosphorus (SRP)
Determined by molybdenum blue method Consisting mostly of orthophosphate (PO4) A good approximation of biologically available P for algal , macrophyte and bacterial growth 2. Soluble unreactive phosphorus (SUP) |
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Sources of Phosphorus (4)
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1. Stream and river inflows (erosion)
2. Wind and aerial deposition 3. Sewage 4. Internal recycling from the sediments |
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Sinks of Phosphorus
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1. sedimentation of dead organic matter
2. chemical precipitation with Fe, Ca, and Al compounds (colloidal P) |
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Most phosphorus is present as....
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Particulate phosphorus in living and dead biomass. Small amounts are excreted as soluble organic P compounds, which some phytoplankton are able to convert to PO4 by releasing alkaline phosphatase
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Phytoplankton are able to overcome phosphorus deficiencies in three ways:
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1. luxury consumption - uptake of more PO4 than required for growth and storage as polyphosphate granules in cells
2. Ability to use phosphate at low levels - in most lakes, the phosphate growth constant, Ks, is low for phytoplankton, which means that the enzyme system is not saturated most of the time There may be species differences in Ks, which may play a role in species succession Because PO4 is rapidly recycled, rate of P uptake is important High uptake rate may compensate somewhat for lack of ability to remove P at low levels 3. Alkaline phosphatase - enzyme that cleaves bond between PO4 and organic molecule to which it is attached. Enzyme is produced in response to P deficiency and is released in free dissolved form into environment This is unique to P metabolism |
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Recycling of Phosphorus:
Excreted phosphorus |
Fish and zooplankton excrete phosphorus into the water.
Excreted phosphorus consists of 50% PO4-P and the rest as organic P. Zooplankton exrecretion supplies phytoplankton demand. |
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Nitrogen:
Sources |
1. Atmosphere - diffusion
2. Nitrogen fixation (by cyanobacteria, major source in eutrophic lakes, minor source in oligotrophic lakes) 3. Precipitation directly on lake surface 4. Stream and river inflows. |
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In what form is nitrogen most abundant?
What other forms are there? Is it most important in aquatic ecosystems? |
Gas
Ammonia (NH3 and NH4+), nitrate (NO3-), nitrite (NO2-), urea, dissolved organic compounds also present Yes |
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What determines the concentration and rate of supply of nitrate?
How does nitrate move through land? easily, maybe? |
Land use practices in the watershed.
Nitrate moves easily though soils, rapidly lost from land even in natural drainage systems. |
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Nitrogen cycle consists of five parts:
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1. Nitrogen fixation
2. Nitrification 3. Nitrogen assimilation 4. Ammonnification 5. Denitrification |
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Nitrogen fixation
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Cyanobacteria transform N2 gas to ammonia. A major source of new nitrogen.
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Nitrification
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Aerobic bacteria gain energy by oxidizing ammonia to nitrite, then oxidizing nitrite to nitrate
Nitrosomonas oxidize ammonia to nitrite, nitrobacter oxidize nitrite to nitrate. |
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Effects of nitrification on pH and alkalinity
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4.3 mg O2 are consumed for every mg of ammonia oxidized to nitrate
8.64 mg of HCO3 consumed per mg of ammonia oxidized (reduces alkalinity) Dramatically reduces alkalinity Also an acidifying process, producing build up of nitric acid Nitrification does not remove nitrogen from the system but changes nitrogen's form. |
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Nitrogen assimilation
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The uptake of nitrogen by plants including phytoplankton
Limited to nitrate-nitrogen and ammonium-nitrogen Animals obtain nitrogen by eating plants or other animals. |
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Ammonification
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the bacterial breakdown of dead animals and plants
Other sources of ammonia are wastes from zooplankton and fish |
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Ammonia is usually present as...
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Ammonium (NH4+)
more reactive than ammonia |
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Uptake of ammonia by phytoplankton and fish
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Rapidly taken up. Persists in small amounts because it is the major excretory produce of aquatic animals.
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Toxicity of ammonia
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NH4+ ammonium ion is harmless
NH4OH is toxic. Usually <.1 mg/L in freshwaters NH3 + H2O --> NH4OH --> NH4+ + OH- |
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Denitrification
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The bacterial reduction of NO3- to N2 Gas
Occurs at low DO levels in sediments and hypolimnion of some lakes Performed by facultative anaerobic bacteria that donate electrons to NO3- during respiration at low O2 levels that occur in lake sediment or in the anoxic hypolimnion |
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What organisms denitrify NH4+?
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None.
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Conversion of Nitrate to NH4
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Involves uptake and then decomposition, usually accounts for all observed lossed of NO3
Open water denitrification is insignificant |
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Vertical profile of nitrogen
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Depend on oxygen profile
Orthograde lakes are oxygenated throughout and most nitrogen is present as nitrate Clinograde profiles have low levels of nitrate but high levels of ammonia in the anoxic hypolimnion in the summer |
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SiO2 influences two things:
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Species succession
Productivity of the phytoplankton |
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SiO2 annual cycle
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SiO2 decreases during spring circulation and in epilimnion during stratification. Early in spring, phytoplankton grow. Diatoms are predominant algae in spring maximum. Spring Maximum declines as SiO2 levels fall below .5 mg/L due to diatom utilization and sedimentation
In eutrophic lakes, Si)2 can be reduced below detection limits due to diatom growth and sedimentation of dead diatoms into bottom waters Mixing of water at the fall overturn may cause second bloom due to sediments in hypolimnion being dispersed throughout lake |
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Nutrient limitations and excesses in:
1. Temperate climates 2. Semi-arid climates |
1. Excess Nitrogen, Phosphorus limited
2. Excess phosphorus, limited nitrogen |
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Limiting nutrient concept
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Leibig's law of the minimum:
the yield of any organism is determined by the nutrient least abundant in environment related to the organisms need for it |
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Main source of Phosphorus
Main source of Nitrogen |
Soil erosion carried by inflowing rivers
Precipitation of water soluble nitrogen |
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Most P is carried as...
During erosion PO4 is carried... Flow of P into rivers is correlated with... |
inorganic and organic particulates
sorbed to clay particles as silt the average slope of drainage basin |
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Influence of climate on sediment and nutrient transport
1. temperate areas 2. semi arid areas |
1. rainfall is spread out, lots vegetative cover
Soil erosion is minimal 2. Rainfall tends to be torrential, vegetative cover is minimal so soil erosion is extensive Nutrients like P and Fe are adsorbed to soil particles move easily in semi arid areas N, S, and SiO2 are usually present in soluble form and are easily transported by clear or muddy water |
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Cultural eutrophication
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Human settlement in drainage basin clears vegeation, develop farms and cities
this accelerates runoff from the land surface, increase nutrients, streams were convenient for disposing of household wastes and sewage, adding to nutrient load this addition of plant nutrients stimulates growth of algae and other plants, stimulates fish, food web Intense proliferation of algae and higher plants accumulate excessively Results in detrimental changes in water quality, biological populations can interfere with human uses of water body |
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DOC or DOM
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Dissolved Organic Carbon or Dissolved Organic matter
Comes from photosynthesis and is categorized into two types: allocthonous DOM or Autochthonous DOM |
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Allochthonous DOM
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comes from material formed in surrounding drainage basin, brough into lake via wind opr runoff.
generally brown |
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Autochthonous DOM
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comes from within lake itself
the result of decomposition of dead organisms the result of material formed by photosynthesis the result of the extracellular release during active growth of algae and macrophytes |
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DOM:
Nonhumic substances |
Low molecular weight compounds, used and degraded by microorganisms and have rapid flux rates within lake
carbohydrates, proteins, peptides, amino acids, fats, waxes, resins, pigments |
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DOM:
Humic substances |
Armorphus, brown or black coloured hydrophilic and acidic complexes formed by microbial activity on plant and animal matter
largest constituent of organic matter in soil and water, have high molecular weight, resistant to microbial degradation persist with long residence times in lakes |
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Two types of humic substances:
Fulvic acids |
low molecular weight carboxylic aliphatic acids that bind Mg, Na, Co, Mn, Fe, Cu, and Zn. Very stable to chemical and biological oxidation.
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Two types of humic substances:
Humic acids |
High molecular weight. Condensation products of phenols, quinones, and amino acids
Bind Fe, extremely stable, have a reddish brown color |
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DOM: five functions.
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1. Influences water transparency, so its a determinant of photic zone depth
2. Many DOM compounds are weak acids or their salts, so provide buffering capacity 3. Compounds bind to metal ions, increasing physiological availability of reactive ions such as Fe and Mn, or reduce toxic substances Acts as a chelating agent 4. Alters water chemistry. DOM is adsorbed by clay, which then sorbs P though interaction of PO4 3-, and Al3+, humic acids chelate Al and so free up PO4. 5. Source of essential nutrients. Many DOM nonhumus compounds are easily used by heterotrophic bacteria within lakes and some algal species If adsorbed on colloids and large food particles, large filter feeding invertebrates may use them |
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Ionic composition (salinity)
1. what is it 2. units 3. governed by (a) open lakes - those with stream outflows (b) closed lakes - no stream outflow |
A measure of the inorganic ion concentration
Units are mg/L a. salinity is governed by chemistry of inflows b. governed by precipitation and evaporation |
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Salinity is dominated by 4 major cations:
and four major anions: |
Ca2+, Mg2+, Na+, K+
HCO3- CO32- SO42- Cl- |
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Proportions of major cations are
Proportions of major anions |
Ca > Mg > Na > K
camnak CO3 > SO4 > Cl Cososea |
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conservative elements
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concentration of Mg Na K CL are high, but very little is used by biota
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Dynamic elements
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Ca, CO3 and SO4
concentrations are lower, but concentrations strongly influenced by biotic metabolism exhibit more seasonal variability |
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TDS
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Total dissolved solids
the total inorganic salts and organic material. measured by boiling water sample at 105 degrees celcius |
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Salinities of different kinds of water
1. freshwater 2. brackish water 3. seawater |
1. TDS is <1,000 mg/L
2. TDS is 1,000 to 20,000 mg/L 3. 35,000 mg/L |
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Soft water
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Low salinity, derived from acid igneous rock
have a salinity of <50 mg/L, cationic proportions of Ca > Na > Mg > K Anionic proportions are Cl > So4 > CO3 |
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Hard water
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Contain large concentrations of alkaline earth metals derived from drainage of calcareous rock
Cationic proportions are Ca > Mg > Na > K Anionic proportions are CO3 > SO4 > Cl |
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Conductivity
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Convenient but indirect way to measure TDS in field using a meter
The reciprocal of electrical resistance measured between two electrodes The more ions in solution, the lower its resistance to electron flow, and hence the higher its conductivity Distilled water is an insulator because it has few dissolved ions |
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Hardness - two most common bivalent cations
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Calcium and Magnesium
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The most common cation associated with carbonate
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Calcium
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Methods of introduction of exotic species
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Unintentional release
Ship related introductions Deliberate releases Entry through or along canals, movement along roads and railroads |
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How many species have had profound effects on the Great Lakes system?
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13
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Unintentional releases:
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Pets released from aquaria
accidental escape release of bait fish Plankton associated fish stockings, invertebrates associated with aquarium plants |
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Shipping related introductions include:
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transport by fouling
solid ballast ballast water |
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4 exotic animal species that are exotic
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Sea lamprey
Zebra mussels Alewife White perch |
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Sea Lamprey
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Entered following the opening of the Erie Canal
The welland canal was built around niagra falls, was enlarged in 1919 Two years later, sea lampreys were found in lake erie, within 20 years, colonized all of the great lakes |
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Sea lamprey:
Morphology |
has no jaws, attaches itself to the side of fish by mouth, rasps a hole in the skin, feeding by sucking blood and body fluids
Can remain attached for days or weeks until no longer hungry or victim dies |
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Sea Lamprey:
impact on other species |
Sea lamprey had no natural predator.
Annual catches of lake trout dropped from 11 million pounds to less than 200,000 pounds Endemic whitefish also extirpated |
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Sea Lamprey:
Growth Control |
Great Lakes Fishery Commision was created in 1955 by a treaty between U.S. and Canada to deal with the sea lamprey problem
Initial attempts to control sea lampreys with mechanical and electrical barriers were largely unsuccessful Then, TFM was used to kill lamprey larvae and not harm other biota Adults returning to spawn reduced by 85%. Lake trout recovery plans included stocking and improvement were seen in Lake superior |
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Alewife
1. how did it enter 2. why did it proliferate |
1. The walland canal from lake ontario
2. Found the great lakes devoid of larger fish predators due to the lamprey |
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Alewife: commercial harvesting
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used for fish meal, fertilizer, pet food
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Alewife:
How did the alewife compete with species? |
by eating the eggs of more valuable fish species
Lake herring completely dissapeared Emerald shiner reduced to just a few isolated population |
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Alewife: how did we get rid of them
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there was a massive dieoff, and hundreds of millions of rotting carcasses rolled up on the beach
Michigan began to stock coho and chinook salmon to prey on alewives Set up a sport fishery for these stocked fish lead to pressure from anglers and charter boat ownders on fisheries management agencies to stock them continues despite alewives have been reduced |
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Other exotic fishes, how they entered:
1. Carp 2. Rainbow Trout 3. Brown Trout 4. Rainbow smelt 5. Pink Salmon 6. golfish |
1. intentional
2. intentional 3. intentional 4. escaped 5. accidental release 6. escaped or released |
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White perch
1. how did it invade 2. which species did it threaten 3. how did it threaten them |
1. though the erie and welland canals
2. Walleye, yellow perch, white bass, minnows 3. by eating their eggs. fish eggs of walleye or white bass comprise 100% of white perch's diet. |
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White perch competing with native yellow perch
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The two species compete for zooplankton
Growth rates of yellow perch declined since invasion of white perch in Lake Erie Two species have diet overlap. |
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White perch hybridizing with yellow perch
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White perch, being in the genus moronidae, hybridized with white bass, in the genus moronidae
Hybrids capable of back crossing with parent species as well as with themselves, they could dilute the gene pool of both parent species |
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White perch:
The hostile take-over of the waters...the history |
Gained access to the lake via the Erie Barge Canal during warm weather
From canal system, species moved down the Oswego River to Lake Ontario Once in Lake Ontario, they moved into Lake Erie via the Welland Canal, continued to spread to upper Great Lakes First reports of westward movement through the great lakes: Lake St. Clair, Lake Huron, Lake Michigan, Illinois water of Lake Michigan Odditiy: The frist sighting of white perch in Lake Superior waters was at Deluth Harbor - one year before it was found in Lake Huron, two years before lake michigan Probably happened from interlake ballast water restricted to lake superior harbor because its the warmest part of frigid lake |
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White perch:
palatable? sport worthy? |
Yes
No |
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Ruffe
1. How/where was it introduced? 2. What species is it affecting? |
1. Duluth harbor, in tanker ballast water
2. yellow perch, emerald shiners, other forage fish |
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The ruffe's ability to displace other species in newly invaded areas is due to:
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1. high reproductive rate
2. feeding efficiency across a wide range of environmental conditions 3. characteristics that may discourage would be predators such as walleye and pike |
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Round Goby
1. What kind of fish? 2. How did it invade? 3. Spawning attributes |
1. Bottom dwelling fish
2. Ballast water 3. Can spawn several times per year, grow to about 10 inches, are aggressive, compete with native bottom dwellers like sculpins and log perch |
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Zebra Mussel
1. where did they become established 2. how were they introduced 3. What kind of problems 4. Why can it spread so rapidly? |
1. inpoundments on the Tennessee River
2. Ballast Water 3. Major biofouling problems to water intake pipes, docks and beaches colonized the shells of native unionid clams to such an extent that clams cannot open their shells to feed, and die filter large volumes of water removing phytoplankton, which are the food for zooplankton, which are the food for larval fish, which have high commerical value Balance of organic matter is changed to increase amount in benthic zone, at expense of that in pelagic zone will cost billions of dollars 4. It has free swimming larvae called veligers, which disperse and attach with a byssal thread. Attach themselves to boats and barges. |
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Zebra mussel:
the mack daddy of filtration |
Zebra mussels are capable of pumping between 39-96 % of the water column per day
Chlorophyll a concentrations dropped Bioaccumulate toxic contaminants, pass them on to ducks and fish |
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Zebra mussel:
Putting the smackdown on them...how? |
Chlorine in water intakes has been responsible
Potassium destroys integrity of gill epithelium |
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Spiny water flea
1. where was it introduced, how 2. why is it difficult to prey on? |
1. Lake huron, by ballast water
2. Long spine |
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Fishhook water flea
1. why is it called the fishhook water flea? 2. why is it a threat? |
1. It has a long tail that ends in a hook
2. Devours plankton essential to diet of larval fish |
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Rusty Crayfish
1. How is it harmful? |
frequently displaces native crayfish, reduces the amount and kinds of aquatic plants and invertebrates, reduces some fish populations
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Three fish diseases
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1. bacterial disease furunculosis
2. parasitic disease Glugea hertwigi - caused extensive mortality in rainbow smelt 3. Myxobolus cerebralis, causes whirling disease |
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Invasive Algae and Plant Species
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1. Purple loosestrife - causing problems due to the excessive beds they form
2. water chestnut - thick stems and sharp pointed seeds 3. Flowering rush - grows as emergent plant along shorelines, submersed plant in lakes and rivers Not technically a problem, but can form dense strands, interferes with recreational use Can crowd native plants, in turn hurt wildlife |
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Control of Ballast Water
1. How? 2. What was the official measure called? |
1.Ships exchange ballast water at sea, with the idea that marine organisms are unlikely to survive in great lakes
2. Aquatic Nuisance control act. At first voluntary, then required 3. |
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Plankton
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mixture of drifting, floating or weakly swimming group organisms that move with wave and currents
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Nekton
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Stronger swimming organism like fish and aquatic invertebrates. Live in pelagic zone.
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Neuston
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special community inhabiting surface waters adapted to exploiting surface tension of water
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Periphyton
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Attach algae important in littoral zone where rocks or higher plants provide firm substrate
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Aquatic macrophytes
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dominate in sandy or muddy areas of the littoral zone
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Benthic organisms
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Organisms associated with lake bottom, including forms found in or on substrates regardless of whether they are in littoral or profundal zone
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Phytobenthos
Zoobenthos |
Aquatic benthic plants
Aquatic benthic animals |
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Epibenthic organisms
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Live and move about on lake bottom
ex: crayfish and dragonfly larvae |
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Detritus community
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Obtain energy from dead materials or detritus
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Microbial loop
1. what is it 2. what trophic level has high concentrations? |
1. Nonphotosynthetic bacteria found in open water that exploit dissolved organic carbon
2. Oligotrophic systems have smaller populations than eutrophic lakes |
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Wetlands
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A complex group of habitats representing zones of transition between typical terrestrial ecosystems and aquatic habitats.
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Phytoplankton: Desmids
1. What are they 2. Morphology 3. Where does the nucleus occur 4. How do they occur |
1. Distinctive group within green algae
2. Each cell consists of two symmetrical cellulose walled halves -- two semi cells joined by an isthmus. Walls of semi-cells are ornately sculptured. Makes the puuurty. 3. In the isthmus 4. planktonic forms in rivers and streams, sometimes in large number in ponds |
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Seasonal succession of phytoplankton
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Phytoplankton grow in a series of booms.
There are quantitative changes (in abundance) and qualitative changes (in species composition) In temperate and polar waters, growth is reduced during winter period Numbers and biomass increase as light increases. Temperature is not the key factor. Buildup continues to a spring maximum Spring blooms dominated by diatoms Asterionella, Fragilaria, Tabellaria Diatoms dominate spring blooms because they grow faster Predation by fungi, zooplankton grazing, and protozoan infections may slow boom formation, but not stop it. Growth eventally ceases after stratification, because nutrients in epilimnion are depleted and become limiting The limiting nutrient for diatoms is SiO2 The end of the spring bloom may be related to physical (no light) chemical (nutrient limitation, toxic accumulation) or biological (grazing) factors. Spring maximum is often followed by period of low abundance and biomass during summer As diatoms decline, they are followed by irregular peaks of various flagellets, greens, and blue greens Zooplankton grazing may be a big factor in delcine of algal populations, and a contributor to seasonal succession In eutrophic lakes, this low period may be brief as late summer blooms of blue greens may occur and persist until fall overturn Blooms of blue greens are often the first sign of cultural eutrophication Blue greens dominate in culturally eutrophic lakes because N is usually the first nutrient to be depleted, and they are capable of atmospheric nitrogen fixation If Fe levels drop, blooms of blue greens will cease because N-fixation is dependent on Fe Growth of other species during the summer is dependent on ammonia-N from animal and bacterial excretion in water, but large populations cannot be supported by recycling of euphotic zone nutrients because the pool is small In the fall, a second maximum occurs This fall maximum is composed of diatoms, but not as big as spring maximum Blooms occur in the fall as a result from nutrient supply and overturn |
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Zooplankton: 3 groups
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1. Microzooplankton - rotifers and protozoa
2. Mesozooplankton - cladocerans and copepods 3. Macro-zooplankton - insects, shrimp |
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Rotifers
Morphology 1. Lorica 2. corona 3. trophi 4. pharynx 5. cuticle |
Body is elongated, divided into distinct regions of head, trunk, and foot
The cuticle (5) is thin and flexible. In some species, cuticle is thickened and forms a (1) lorica The anterior end or corona (2) where the mouth is located is ciliated Cilia are used for both locomotion, and in the directional movement of food to mouth The food is ground by the trophi (3) located just behind the mouth in the pharynx (4). Trophi are found in almost all rotifers The body of the rotifer is externally but internally segmented the body is telescopic, with semi flexible cuticle (5) covering Within the body are the stomach and reproductive organs. Final region of the rotifer body is the foot; this foot ends in a "toe" containing a cement gland with which the rotifer may attach itself to objects in the water, sift food at its leisure |
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Rotifer
Reproduction |
Many rotifer species have no males, females producing only females
Called parthenogenesis In some rotifer species, stress can cause females to produce eggs that hatch as males Males have no mouth or digestive tract, die within hours or days. The appearance of males is followed by sexual reproduction. The females then produce resting eggs, which settle to the bottom to hatch when conditions permit The tiny eggs can withstand dessication for considerable periods of time and can be carried by wind or birds to any place that holds water (even bird baths, gutters) where they will hatch |
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Rotifer density
1. highest where? 2. why are planktonic populations less dense? |
1. in association with submerged macrophytes, where it may approach 25,000 individuals/L
2. because there are few sites for attachment, less protection from predation |
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Zooplankton: Cladocera
Morphology |
Have a distinct head, the body is covered by a bivalve cuticular carapace
Have a large compound eye and smaller ocellus that are light sensitive The second antennae are large swimming appendages and constitute the primary means of locomotion |
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Zooplankton: Copepoda
Three groups |
1. Calanoida
2. Cyclopoida 3. Harpacticoida |
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Harpacticoids
1. Morphology 2. Where are they found 3. How do they feed |
1. Anterior part not broader than posterior.
First antennae are very short and usually have one egg sac carried medially. 2. Exclusively littoral, found on macrovegetation and sediments 3. Seizing and scraping particles from vegetation and sediments |
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Cyclopoids
1. Morphology 2. Where are they found 3. Food niches |
1. Anterior part of body much broader than posterior, first antennae is short,
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Repeats
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The following flashcards are repeats on the exam
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How and under what conditions were autotrophic picoplankton connected in this paper?
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Filtered under black polycarbonate membranes, counted under an epiflouresent microscopy with UV illumination with a green filter
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What was the most important factor affected the horizontal distribution of phytoplankton in Loch Ness and what affects this?
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North south gradient in productivity and the catchments in the north basin have more arable land compared to south so there were more nitrate and chlorophyll from south to north
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What info was used to infer that the highest concentration of the small… (Sorry I didn’t write fast enough to get the rest of this question)
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The highest concentration of fish was in the south where there was a large path of diatoms and the number of zooplankton was negatively related to the number of fish suggesting fish were actively foraging and deleting the zooplankton in the areas they were
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Q. What two things happened in Lake 26 when only phosphorus was added for 3 years?
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No nitrogen fixation appeared in phytoplankton
- A luxurious growth of attached algae that was capable of high nitrogen fixation was observed. |
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Die off of fish in a lake or pond due to low oxygen concentrations can occur both under the ice in winter and in the summer. What factors are involved?
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Use previous
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Why does the pH of unproductive calcareous lakes fluctuate?
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Unproductive calcareous lakes have a pH of 7-8.
Unproductive means little CO2 is used No decline in pH |
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Explain what is happening in this figure. What causes this effect?
picture of lake calcifying |
Calcium carbonate precipitation
High rates of photosynthesis in such lakes can raise the pH to about 9 by removing CO2 and even to a pH of 11 if plants use bicarbonate. This can lead to dramatic daily cycles of pH change in poorly buffered lakes. Calcium rich lakes usually have 7-8 pH. When CO2 is removed from water, equilibrium shifts to insoluble CaCO3, releasing CO2 from bicarbonate |
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The amount of oxygen in the hypolimnion can be used as....
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a comparative index of lake primary productivity.
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The absolute oxygen deficit is...
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the difference between observed concentration at prevailing temperature and saturation value at 4 degrees celsius.
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The areal hypolimnetic oxygen deficit is...
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the amount of oxygen lost per unit time between spring circulation and height of summer stratification
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