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111 Cards in this Set

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dissolved vs. particulate chemicals
the distinction is often arbitrary, commonly based on the ability to pass through a filter of a given size
conductivity as a measure of dissolved ions and as an estimator of productivity
conductivity is proportional to the relative amount of electricity that can be conducted by water, and can be correlated approximately to system productivity because high nutrient waters have high conductivity, but other factors including concentration of nonnutrient salts also influence conductivity
chemical vs. mechanical weathering, and the role of microbes
chemical weathering releases dissolved matter, whereas mechanical weathering releases particulate matter that may react to form dissolved matter at some point. microbes can enhance the rates of weathering
why high runoff volume has low dissolved matter
the total concentration of dissolved matter is related inversely to the amount of runoff because the higher the runoff, the less time water had to dissolve ions (but relationship is variable due to geomorphology, geology of parent material, and area of runoff)
assimilation and how it decreases concentrations of ions in the water:
ex. as nitrogen is taken up by an organism(assimilated) the concentration of nitrogen in the water decreases. Has to do with interactions with biota
abundance of ions in water flowing from terrestrial habitats
indicators of water quality; what turbidity is and what influences it
- color, taste, odor, suspended solids, and turbidity
- turbidity: measured as light absorption or light scattering of water (influenced by suspended particles, and tannins and lignins from decomposition of organic material
what drives whether an environment is going to have oxidation or reduction, and generally why redox matters in ecosystems:
-the relative availability (concentration) of electrons for chemical reactions in a solution (low redox=lots of available electrons (reducing environment) & high redox=few available electrons (oxidizing environment). when O2 is present, redox values are high because oxygen has an affinity for electrons). redox potential is a large determinant of what chemical reactions will occur without an input of energy, what reactions will require energy, and what products will be favored in the environment.
-oxidizing environments only allows chemical reactions that release electrons to occur.
-whether or not the environment is oxic or anoxic, in an oxic environment, oxidation takes place and in an anoxic environment, reduction takes place

- “a compound will have high potential energy if it is a low redox compound in a high redox environment or a high redox compound in a low redox environment” (pg 297)
dissolved oxygen
amount of O2 dissolved in the water. concentration is a primary determinant of redox (when present, redox values must be high)
what processes determine how much oxygen is present in an ecosystem
metabolic activity rates, diffusion, temperature, and proximity to atmosphere (sources in water: photosynthesis, diffusion, mixing, dams)
why oxygen supersaturation can occur
if oxygen becomes supersaturated, it will form bubbles and come out of solution (in fish - leads to gas bubble trauma which causes strokes, ruptured swim bladder, decreased breathing abilities, and subdermal air bubbles) and can be caused by photosynthesis (e.g., when there is a high biomass of phytoplankton at the metalimnion)(during calm days O2 can build up in the epilimnion especially in littoral zones)
main reactants and products of photosynthesis and respiration
- photosynthesis: H2O + CO2 + light energy = CH2O + O2
- respiration: CH2O + O2 = CO2 + H2O + chemical energy (ATP)
compensation point, and the relative net photosynthesis curves of high light adapted and low light adapted plants, and where you might find those different types of plants
- compensation point: where gross production equals respiration
- low light adapted: have a low compensation point, have rapid increase in P.S. rate as light increases, but tend to be photoinhibited at low irradiance. found in the benthos/profundal zone, heavy surrounding vegetation, or under dense canopy
how mixing affects phytoplankton photosynthesis in lakes
if turbulent mixing is deep enough, the average light experienced can be too low to support growth. Phytoplankton are most likely to be below this depth during winter when lake is not stratified and ambient light is low
photoinhibition
direct or indirect damaging effects of high-intensity light on the molecules in plant cells, reducing photosynthetic capacity
factors that influence photosynthetic rates and respiration rates
- photosynthetic rates: light, temperature, nutrient availability, water velocity / dissolved oxygen content (high levels inhibit photosyn.), organic compounds (which lower photosynthetic rates)
- respiration rates: quality of organic carbon available for consumption, temperature, exchange rates with the environment, compounds that influence physiology (e.g., toxins, extreme pH, salinity), activity levels (for animals)
when and why there are low oxygen concentrations or anoxic conditions in the hypolimnion, and how it relates to lake mixing
The hypolimnion is usually deep enough that little light reaches it, restricting photosynthesis. Respiration predominates as organic carbon rains down from above. Oxygen is depleted gradually in the hypolimnion over time. Mixing blends dissolved oxygen throughout
why sewage releases can lead to anoxia
the load of organic carbon in untreated sewage stimulates respiration and consumes oxygen at a rate in excess of that which can be replenished by exchange with the atmosphere. water then becomes anoxic and can lead to fish death
why groundwater is generally anoxic
because when it is deep enough, there are: a low supply of O2, high temperatures associated with geothermal heating, O2 consumption by organisms, reactions with organic chemicals, and long turnover times
ability of CO2 to be supersaturated
increased atmospheric pressure, slight acidity
see the Lake Nyos example in Sidebar 13.1
forms of organic C
DOC (dissolved), POC (particulate), FPOM (fine particulate), CPOM (coarse particulate)
-the difference between DOC and FPOM is 45um, the difference between FPOM and CPOM is 1mm
why organic C availability is particularly important in groundwater, benthic sediments, and forested streams
because these habitats are dominated by heterotrophic organisms
biochemical oxygen demand, including basically how it's measured:
the total demand for oxygen by chemical and biological (respiration) oxidative reactions; common method to estimate total available organic carbon for heterotrophs; look at Method 13.1 for how it’s measured-- incubate water in a sealed bottle and measure how much O2 is depleted over time, by how much O2 is used, you can figure out the biochemical oxygen demand
humic compounds and tannins
Humic compounds are large molecular weight compounds and lend a brownish color to the water, by-product of breakdown of larger molecular weight compounds such as tannins, cellulose, and lignins. non-humic includes sugars & other carbs, amino acids, urea, proteins , pigment, lipids, Low molecular weight):
- general interaction with organic pollutants and metals(Tannins and humic substances)
1. attach to many other organic substances, which is important for the transport of pollutants.
2. they form complexes with metal ions, which can be important for keeping iron in solution.
3. how they color the water, resistance to degradation(Both are resistant to biological degradation)
4. form colloids
factors that affect rates of decay of organic compounds
(see Fig. 3.15 and p. 333)
-simple vs complex carbon
-macrophytes and organic material
- temperature and inorganic nutrients
- human land use can alter rates (agriculture input and disturbance)
why peat bogs form in anoxic conditions
b/c anoxic conditions lead to slower breakdown of organic materials due to reduced efficiency of carbon oxidation and inhibition of microbial activity by metabolic by-products (lowering pH); thus, accumulation of organic compounds under anoxic (or acidic) conditions leads to formation of peat bogs
methanotrophs, including under what conditions they live:
bacteria that specifically oxidize methane; generally found living in close proximity to anoxic habitats from which there is a constant diffusive influx of methane
why wetlands and rice paddies are a source of methane
methane escapes from wetlands b/c anoxic processes lead to methanogenesis
assimilation
organismal acquisition of nutrients; generally occurs regardless of the redox state of the environment
remineralization
the excretion of inorganic nutrients by organisms
forms of N
N2 gas, inorganic nitrogen (nitrate, nitrite, ammonium), organic N (dissolved organic N (<.45um) and particulate organic N (>.45um))
- most common form is N2 gas (atmosphere composed of 78% N2); water contains N2 as a dissolved gas
- NH3: ammonia (high pH conditions)
- NO2: nitrite - toxic
- NO3: nitrate
- NH4: ammonium (ionic form found in neutral conditions)
- organic: amino acids, nucleic acids, proteins, and urea
biological use of N – what biological molecules it's in, what form of N is necessary for use by cells
- amino acids, nucleic acids, proteins, and urea
- many animals can assimilate nitrogen only in the form of organic molecules (amino and nucleic acids in the tissues of other organisms)
- primary producers and bacteria use nitrate, nitrite, or ammonium
- understanding N fluxes are crucial because N can limit primary production
N fixation – what organisms use it, how it's a pathway for entry of N into aquatic habitats
- many bacteria (cyanobacteria and some archaea) can assimilate N2
- enzyme nitrogenase used, and is extremely energy intensive. enters aquatic habitats through leaching, leaves falling into water, large populations of cyanobacteria and rainwater
nitrification as an oxidation process; importance to ecosystems
-It is the oxidation of ammonia to nitrites, then those nitrites to nitrates. NH3 or NH4 to NO2- (+energy) to NO3- (+energy)
-vital link in the nitrogen cycle, nitrite can impact health negatively, nitrifying bacteria compete for ammonium with primary producers
denitrification as a reductive process (in anoxic conditions); why it's a key link in the N cycle
leads to the conversion of inorganic combined nitrogen (nitrate) to the relatively unavailable N2 gas
- NO3- to N2O to N2
excretion of N by organisms; why it's an important flux in ecosystems; ammonification:
- organisms can ingest more nitrogen than needed, and must excrete the surplus;
- ammonification: when ammonium in remineralized. excessive ammonium produced by high densities of fish can be toxic
relative amounts of ammonium and nitrate in anoxic vs. oxidized waters, and what that would mean for where each would be concentrated in a f.w. environment, e.g., a stratified lake
(Figs. 14.4, 14.5)
- nitrate is predominant of dissolved inorganic nitrogen in oxidized waters
- ammonium is in predominate form in anoxic waters
- in a lake with an anoxic hypolimnion, ammonium dominates the hypolimnion, and nitrate is mainly confined to epilimnion during stratification (in the epilimnion, nitrification transforms ammonium to nitrate in the presence of O2, but in the hypolimnion nitrate is removed by denitrification under anoxic conditions, and nitrogen continues to be excreted in the form of ammonium)
- high ammonium in streams is often associated with input of anoxic groundwaters or pollution
nitrate contamination problems for human health
- methemoglobinemia (blue baby syndrome): nitrite binds more strongly to hemoglobin than O2
- conversion to carcinogenic nitrosamines in stomach (gastric cancer and fertilizer use correlation)
S cycle as a complex nutrient cycle, supplying energy for organisms under a variety of conditions (oxic and anoxic), and interacting with metals and thus, indirectly, other nutrients → do not memorize all the various transformations, but do know that by removing iron species from solution, it frees phosphate (p. 360)
- complexity of the cycle driven by different redox states in which it can occur, and illustrates that organisms have evolved to use most of the possible common compounds in the biosphere that have potential energy
- in aquatic systems, is rarely a limiting nutrient
- removes iron from solutions, freeing phosphate that would normally precipitate
- sulfides can combine with metals to form pyrites that have low solubility under anoxic conditions (can represent iron loss (iron pyrite) in aquatic ecosystems)
- water quality factor (color and odor)
P as a key limiting nutrient for primary production in aquatic habitats:
phosphorus is mainly found in only one inorganic form (phosphate), and limits primary production in aquatic habitats
forms of P
main inorganic form: phosphate(relative concentration in oligotrophic habitats), organic forms (DOP, PP)
- phosphate (PO4) is a dominant form of inorganic phosphorus in natural waters
- organic: nucleic acids and lipids
biological use of P – what molecules it's in
- used in cells for nucleic acids, phospholipids, ATP, and other compounds
interaction of P with Fe, when and how it happens (temporally and spatially), and why that's important
- determines the availability of phosphorus in many aquatic systems
- phosphate will precipitate with some metals (ferric iron) in the presence of oxygen (forms fericphosphate) and leads to the deposition of phosphorus in sediments when surface water is oxygenated. When it settles into an anoxic zone, the iron breaks off; eddy diffusion of dissolved materials moves the phosphorus back to the surface in the fall when fall mixing breaks stratification
Si as a limiting nutrient for diatom production; frustules
diatoms rely on silicon as a component of their specialized cell walls (frustules)
silicic acid, and sources of Si
- silicon cycles drive the dominance of diatoms in surface waters and can be a primary determinant of algal community structure in lakes and streams
- silicic acid: usually the form dissolved in waters
- sources: clays containing silicon compounds
temporal and spatial variability in Si concentrations, esp. in lakes (Fig. 14.10)
- can be depleted in the epilimnion of lakes during summer because of the slow cycling of silicon, its incorporation into diatom frustules, and the sinking of these frustules before they can be re-dissolved
forms of Fe: Fe+3 and Fe+2 and under what conditions they're favored (anoxic vs. oxic)
- under oxic (high redox) conditions iron becomes ferric (Fe3+)
- under anoxic (low redox) conditions iron becomes ferrous (Fe2+)
biological use of Fe – what molecules and pathways it's in
- key element in electron transport proteins, hemoglobins, enzymes used in synthetic pathways for chlorophyll and proteins, and enzymes used for nitrate assimilation, photosynthesis, and other essential metabolic processes
temporal and spatial variability in Fe concentrations, esp. in stratified lakes
- variability is especially pronounced in concentrations related to anoxic events such as summer stratification in eutrophic lakes
Fe interaction with humic compounds and subsequent problems for organisms:
large concentrations can complex with iron so successfully that they make iron unavailable to organisms
Fe relationship with phosphate
iron can precipitate phosphate, settles to sediments in oligotrophic lake or wetland. If hypolimnion is anoxic (as expected in a eutrophic lake) the FePO4 precipitate will dissociate into phosphate and ferrous iron. Allows higher concentrations of phosphorus to be maintained in the surface waters and leads to algal growth (since it is often limiting)
generally, why redox gradients are important and how human impacts have changed redox heterogeneity (see p. 370)
- redox gradients are sites of high rates and diverse types of metabolic activities, occur because of dependence of many aquatic microbial geochemical processes on either reduced chemicals in oxidized environments or oxidized chemicals in reduced environments; locations where reduced compounds are diffuse rapidly into oxidized conditions and vice versa.
- humans changed: urbanization lowers heterogeneity and decreases anoxic carbon-rich habitats leading to lower rates of denitrification
why microorganisms tend to dominate extreme environments
higher plants and animals have complex multicellular systems that cannot evolve to compensate for extremes
how organisms survive freezing, lack of water, and high light intensity
- freezing: the ability to avoid ice crystal formation is necessary; supercooling (lowering of the freezing temp of the water in their bodies); some slow the rate of freezing to allow the body time to adapt; diapause; fishes amphibians, This is for salinity:invert. produce glycerol (anti-freeze)
- lack of water: produce resting eggs, accumulate sucrose to maintain biological molecules during drying
- high light intensity: compounds absorb damaging UV rays by preventing the formation of harmful free radicals, protective pigments and behavioral responses
how saline lakes and ponds form; how organismal diversity changes with increasing salinity, and which organisms (generally, not specific genera or species) have the highest salinity tolerance
- occur in closed basins where water primarily leaves through evaporation, leaving salts that have weathered from the surrounded watershed behind
- there is a general decrease in diversity of animals and plants and salinity increases (bacteria and archaea dominate in the harshest) most likely because of an inability to osmoregulate
sulfur-oxidizing bacteria – where they live and why; how organismal diversity changes with increasing temperature in hot springs, and which organisms (generally) have the highest temperature tolerances
- live in hot springs, and at the highest temps, are the dominant primary producers
- oxidize sulfides to sulfuric acid
psychrophilic
organisms that require cold temperatures (less than 5 degrees C) to grow and/or reproduce
what organisms dominate Antarctic lakes, and what adaptations allow them to do so
- primary producers (planktonic algae): adapted to compete for light(under thick layers of ice); some can consume small particles and photosynthesize, which allows them to survive in long winters with no light
- cyanobacteria (glacial channels to antarctic lakes): can be freeze-dried for much of the year but can actively photosynthesize minutes after being wetted
what organisms dominate snowfields
- microbial primary producers such as chlorophytes (most common), euglenoids, chrysophytes, cyanobacteria, and diatoms
- these primary producers can support a community of fungi, bacteria, rotifers, protozoa, and some inverts.
- most common: single-celled green algae (chlorophytes)
what the greatest challenge for organisms in temporary pools is, and what adaptations allow them to overcome it; why amphibians tend to live in these pools while fish do not
- drying: resting stages that are resistant to desication and/or life stages with the ability to fly/crawl or be blown into pools.
- use for different parts of life cycles
- fish need water at all times, amphibians only need for certain parts of the life cycle (lack of fish predation lets amphibians and invertebrates thrive)
small pools in pitcher plants and tires (the authors don't mention bamboo!); why these are ideal study systems and what organisms tend to dominate these habitats
- dominant organisms: insect larvae and tadpoles of some amphibians
- attractive study systems b/c they form a well-defined ecosystem in which all members of the community can be identified and pools can be easily replicated and sampled
organismal adaptation to ultraoligotrophic habitats
- slow growth
- resting or static stages
neustonic organisms
microorganisms that live at the surface
why the water surface layer is an extreme environment – challenges that organisms face in the surface layer and how they overcome those challenges
- extreme b/c: biogenic surfactants (humic and fulvic acids) accumulate here; lipids, metals of concern, nutrients, and some microorganisms can also accumulate; bubbles can interact with chemicals on the surface, creating foam; water surface tension exerts considerable force on small organisms
- organisms must be able to tolerate very high levels of light (high energy exertion in repair of light damaged cells)
- organisms can manipulate surface tension by exuding organic compounds that spread across the surface; e.g., veliid (Velia caprai) and beetles in the genus Stenus are able to excrete material that lowers the water tension behind them, so surface tension in front pulls them forward
basic difference between acute and chronic toxin exposure, and lethal and sublethal responses
- acute: exposure that comes in large pulses over a short period of time
- chronic: exposure that is in low doses over a long period of time
- responses: lethal (death) and sublethal (not causing death)
bioconcentration and biomagnification; what influences uptake and retention of a contaminant
- bioconcentration: the ability of a compound to move into an organism from the water
- biomagnification: the entire increase in concentration from the bottom to the top of the food web
- factors that influence uptake/retention: metabolic rate, rate of assimilation of contaminated food, heterogeneous distribution of the pollutant, and rate of excretion of the contaminant. the less water-soluble the organic compiound, the more they are concentrated by organisms.
EPT index:
basic community-level indicator of stream health and water quality that uses the total number of insect taxa in the groups Ephemeroptera, Plecoptera, and Tricoptera, which are usually intolerant to pollution
pollution tolerance index
taxa are assigned tolerance values (0-10) based on their distributions across pollution gradients (species found in polluted environments receive values closer to 10)
basic definition and examples of organic pollutants; (pesticides, herbicides, insecticides) what we don't know about them
(almost nothing is known about how complex mixtures of these compounds at low concentrations will influence human health, not well regulated due to the large number of them) examples of pharmaceuticals and personal care products found in freshwater environments, and some of the potential negative effects of their presence
- birth control pills and painkillers
- sunscreen, caffeine
- organophosphates, carbamates, pyrethrins, organochlorides, roundup (contains a surfectant plus glycophosphate)
acid precipitation: sources, transportation mechanisms, and ecological effects
-source: combustion of coal and oil -->sulfuric and nitric acid formation in precipitation. transported via wind from factories/exhaust, precipitation. Also, mine drainage
-lowered rate of microbial decomposition, greater rates of organic material deposition (increased carbon accumulation), algal population bloom and collapse, shifts in algal, plant, and animal communities, decrease in diversity, the efficiency of energy transfer up the food web is lowered, increases concentration of aluminum (damaging fish gills); effects of emission controls on acid precipitation
which organisms commonly have lead toxicity and why
water fowl commonly have lead toxicity due to history of lead shot pellets for hunting in freshwater systems-birds consume the pellets that are in sediments. Lead fishing weights also have an effect on the lead concentrations of freshwater systems.
how mercury enters aquatic systems and which organisms are most susceptible to lead toxicity
Hg enters system from atmospheric fallout from coal burning, trash incineration, industrial emissions- methylated in anaerobic conditions in sediments-gets into food web-often through periphyton- bio accumulates into fish and then people
why climate change may exacerbate salinity problems and why that might be a problem
increased temperature and droughts will increase evaporation which will concentrate solutes. This is problem for organisms: osmotic stress-slower growth, reduced reproduction, death. reduced biodiversity and ecosystem functions-primary production and decomposition rates
why suspended solids and sediments can negatively affect freshwater ecosystems
- shading, limiting light transmission, interfering with filter feeding, and harboring pathogens, interfering with reproduction, respiratory O2 transport, habitat availability. increase scour,
sources of thermal pollution, and why thermal pollution matters to organisms
- thermal pollution: any deviation from natural temp in a habitat.
- small changes can have large effects
-industrial cooling activities, discharges of cold water below large impoundments, power plants & industrial factories, deforestation, urban runoff, dams
-cool water withdrawn from streams used to cool machinery and hot water returned
- urban runoff esp. during intense storm events in areas with lots of asphalt
- reduction in flow/volume
- withdraws for irrigation, hydroelectric, etc. can effect metabolic rates of ectothermic organisms, cues for spawning fish, facilitate est. of exotic species, alter growth and development of species
- thermal shock in fish
uptake & assimilation (again)
- nutrients need to be taken into cells from the water surrounding them (uptake) and then incorporated into organic molecules used for growth (assimilation)
Michaelis-Menten relationship
how the equation works, KS and Vmax adaptations to low vs high nutrient environments, using the growth curves to predict which organism would dominate in a given scenario
-As concentration increases, uptake occurs most rapidly at low levels of nutrients, and asymptotes as the maximum uptake is approached. V=uptake, Vmax=max uptake, [s]=substance concentration, Ks=concentration of S where V=1/2
luxury consumption
uptake of nutrients in excess of needs, nutrients are scarce, except in pulses, and it is necessary for organism to store it for future use.
what affects nutrient uptake, aside from nutrient concentration
temperature, light, pH, metabolic characteristics
main limiting nutrients for organismal growth in freshwater systems
usually N or P, sometimes both. they are spatially and temporally variable (this is from class notes, she drew that diagram showing inputs of N and P)
Redfield ratio
use of the ratio to determine nutrient limitation-(the relative ratio of C:N:P for balanced growth
is 106:16:1)
Leibig's law of the minimum
the rate of a process is limited by the rate of its slowest sub process, the weakest link in a sense
colimited ecosystems
ecosystems that are limited by both nitrogen and phosphorous
paradox of the (phyto)plankton: basic argument that Hutchinson proposed, and why the paradox doesn't really exist: Why don’t one/few plankton dominate in well mixed lakes?
different species have different needs and are not necessarily directly competing
temporal and spatial small scale variability
the time between the mixing events is less than they need to compete
zooplankton predation and viruses modify population dynamics
mutually beneficial interactions between some
models have trouble with more than 3 limiting factors
microbial loop and its importance for remineralization
dominates nutrient cycling in many groundwater aquifers and sediments, where larger organisms do not occur and there is little new nutrient input.
organisms as concentrations of nutrients
e.g., diatoms and Si, fish and P, or salmon and marine-derived N
oligotrophic, eutrophic, mesotrophic: what parameters are used to determine the trophic state of an ecosystem, and why that ecosystem might not fit into one trophic system classification (e.g., why would Loch Ness be characterized as ultraoligotrophic for chlorophyll but meso- or even eutrophic for Secchi depth?)
- (Based on water clarity, phytoplankton biomass, and nutrient concentration)
- (Lake may not fall into an individual category. ex. phosphorus could be high enough to classify as eutrophic, but, but light attenuation by suspended sediments could keep chlorophyll levels at mesotrophic level)
why determining the trophic levels of a stream is particularly difficult
B/c of hydrological variation,flooding, and light limitation by riparian canopy leads to high variability in benthic algal biomass over time and space
how productivity of wetlands is generally characterized
- use biological characteristics. ex. many oligotrophic N-limited wetlands have carnivorous plants that capture insects to receive nutrients, while high nutrient concentrations often result in weedy species
negative and positive effects of eutrophication in lakes
increased production, but can lead to decreased O2 and dead zones. eutrophication can lead to acid rain resistance b/c of buffering by metabolic activities
how could lake fertilization lead to increased fish production, but why might it also not work?
Fertilization could increase autotrophs , but could lead to toxic algal bloom that depletes O2
what might you need to consider when trying to mitigate eutrophication in a freshwater ecosystem?
1. identify lake with problem
2. characterization of system including morphology, land use, and nutrient loading
3. identify feasible strategies for nutrient control understanding point and nonpoint sources
4. projecting influence of management actions on nutrient concentrations in lakes, predicting response of chlorophyll to lower nutrient level
5. assess potential effects of decreased chlorophyll with lake clarity
6. cost benefit
7. monitoring
how does it differ in lakes vs. rivers and streams?
- in lakes, mitigation is mostly focused on biological controls via removal of macrophytes, providing O2 to hypolimnion to keep P in sediments, destratification (same reason), use of copper to control algae and releasing water from the hypolimnion
- in streams and rivers, focus is on controlling nutrient levels, especially from sewage effluent.
point sources of nutrients, and nonpoint sources, and the differences in controlling them
point source nutrients come from a single identifiable source eg a single sewage input. non point sources from a variety of non identifiable factors such as groundwater, leaching, rain and other large scale sources
what are the problems associated with sewage input into streams?
-increased nutrients, eutrophication
Sewage input into streams leads to a loss in O2 and the introduction of pathogenic bacteria. Current sewage treatment does not lower total nutrient input much, but does lower loads of biochemical oxygen demand and pathogenic bacteria
nutrient sinks:
Wetlands can have major impacts on flows of nutrients, sediments and water through watersheds. Wetlands are successful at nutrient removal and sewage treatment. Essentially all wetlands retain nitrogen and therefore function as nutrient sinks.
the mechanism that makes it possible for cyanobacteria to sink and rise in the water column with differing nutrient concentrations (taxis)
(Gas vacules allow cyanobacteria to float or sink.
cyanobacteria as example of phototaxis
phototaxis is a kind of locomotion of an organism based on response to light-ex. may be positively phototactic , as light increases the organism moves toward light, may be photophobic at high light levels. may move down into microbial mat for nutrients at night, until day comes and phototaxis overrides chemotaxis
microbial loop (again)
Transfer of energy, carbon, and other nutrients through the microbial food web. The majority of organic material that originates in terrestrial environments and enters aquatic environments must be processed by microbes. organisms that eat these bacteria or fungi, or use them in their guts, return the carbon back into the food web. without microbes, the majority of carbon would be tied up in nonliving dissolved and particulate organic matter. microbial loops are dominated by phytoplankton, bacteria, protozoa, viruses, and rotifers.
bacteria and fungi as key suppliers of C in stream food webs-
Bacteria and fungi break down wood and leaves, making carbon available to primary consumers
role of viruses in plankton communities
Viral infections occur in all known organisms, and viruses predate on bacteria and other microbes, helps control population. also, viruses are important vectors for gene transfer. Transduction, is when gene transfer among bacteria by viruses occurs. viral infection keeping cell densities below a threshold may prevent competitive dominants from overrunning less competitive cells. some cyanobacterial bloom collapses have been attributed to viral infections. helps explain “paradox of the plankton”
factors that control grazing on planktonic food webs
plankton are difficult to consume because very small particles are hard to remove from water via infiltration due to low Re and high viscosity. Clearance rate is the volume of water that can be cleared of particles per unit time. viscosity affected by temperature, so feeding is more difficult in cold environments, and feeding on plankton decreases. Particle size, as particles become more dilute, greater volumes of water must be cleared to receive the same amount of food.
scrapers
scrape biofilms, feed on subsurface strata, consuming algae, heterotrophic components of biofilm, and associated organic sediments
shredders
organisms that eat detritus & are essentially microbial predators, since the microbes make up much of the nutritional value of the detritus. Shredders are key in the decomposition of organic material, by breaking down CPOM. prefer conditioned detritus, due to microbes
collector-gatherers
organisms that consume relatively small, less than 1mm diameter, deposited organic material from the surface of substrata are collector gatherers. many eat entire microbial assemblages or pick out particles that are rich in cellular material and more biologically active. contribute significantly to turnover rates of organic particles. affects higher trophic levels
filter feeders
passive vs. active, and what that means for how much they can consume and its effect on the ecosystem):(Active=pump water through filtering structure, ex.bivalves. can filter large quantities of water and remove significant amounts of phytoplankton and suspended particles Passive filter feeders are often dominant in flowing water
parasites
including trematodes that affect frogs, and how that happens):(Trematoda Ribeiroia has been linked to deformities in frogs bc the cercariae larvae of this parasite penetrate and encyst in developing limb buds of larval amphibians.Trematoda Gorgoderina vitellioba, infects frogs by tadpoles ingest trematoda and enters kidneys, after 21 days the fluke enters the bladder and deposits eggs, which are excreted into the water. they hatch, and small swimmer form enters gills of fingernail clam, then they emerge as worm that is eaten by tadpoles
conditioning, and the peanut-butter-on-the-cracker example
Microbial colonization of detritus is conditioning. Microbes=peanutbutter or Nitrogen source, detritus=cracker or Carbon source. Together they are just smearing in...
a. You are at a scientific conference and go to hear two presentations by two different research teams about the same lake. In the first presentation the lake is described as oligotrophic, but in the second presentation the lake is described as mesotrophic. Assuming both research teams are correct, how could this be? Give specific examples. If you had only heard the first presentation, what would you assume about O2 concentrations in the hypolimnion and why? If you had only heard the second presentation, how would that assumption about O2 concentrations in the hypolimnion have been different?
There is more available oxygen in oligotrophic lakes in the hypolimnion because there are fewer organisms in the lake that die and sink to the bottom where they decompose (eutrophic lakes can be anoxic at the hypolimnion due to algal blooms). it depends on what factors that determine classification you are focusing on. A lake can appear to be mesotrophic due to higher concentrations of phosphorus, however there may be other facts limiting algal growth, so if you look at the algal growth in the lake, the lake would appear to be oligotrophic. The classification of lakes is based on water clarity, phytoplankton, and nutrient concentration. Because of variances in these categories, lakes may not fall into one particular classification. Loch Ness - Lake may not fall into an individual category. ex. phosphorus could be high enough to classify as eutrophic, but, but light attenuation by suspended sediments could keep chlorophyll levels at mesotrophic level

Lake Baikal: the intensity of primary production in lake baikal makes it near mesotrophic, however its physico-chemical characteristics categorize it as ultra-oligotrophic.
Describe G.E. Hutchinson's paradox of the plankton. What are three reasons that can explain this apparent paradox? Why does the paradox of the plankton refer to communities in lakes but doesn't cross over to apply to plankton in rivers or in groundwater?
The paradox stems from liebigs law of the minimum and the competitive exclusion principle that when two or more organisms are competing for the same resources, one will out compete the other and will dominate. However, plankton occur in high diversity and generally have similar requirements, and so they are competing for the same nutrients. Nutrients are evenly dispersed due to the regular mixing in lakes, and each species of plankton has a chance of survival. Explanations: 1.Species have different needs, so they may not be directly competing.
2.there is temporal and spatial variability, or micropatches of nutrients from uneven mixing .
3.The time between mixing events is not long enough for species to outcompete- lake isn’t sitting as a well mixed environment for long.
4. Zooplankton predation and viruses modify population dynamics by removing dominant competitors.
5.some have mutually beneficial interactions, where a weaker species may rely upon a stronger, dominant species.
6. Models have trouble when three or more limiting factors are present.
Does Loch Ness provide an appropriate habitat for the existence of a monster? Use ecological evidence to defend your position
Loch Ness is oligotrophic in terms of nutrients, has low light levels deeper in the lake due to a brown color (resulting from humic acids from surrounding peat) and it has a very small littoral zone. These all limit primary production in the lake. Also, the top predator (excluding any pleiosaur), ferrox trout (a piscivorous and cannibalistic fish) was found with empty stomach contents in february and march.
List and discuss three forms of carbon available to heterotrophs in aquatic ecosystems. For each form, describe the location in a river where it would dominate, and how that relates to the types of invertebrates and fish that would be found at that location.
DOC
CPOM: found in headwaters - higher abundance of shredders and collectors. fish which consume invertebrates are therefore also abundant.
FPOM: in midsized rivers, higher abundance of grazers and collectors, because the greater availability of sunlight which increase algae production (consumed by grazers). Grazer activity can also enhance algae production by reducing light limitations, cycling nutrients. predators are both invertivores and piscivorous.
FPOM: in large rivers, filter feeders and collectors are dominant (declining primary production because of growing pelagic zone with river order), and fish which consume invertebrates, plankton and fish may be present.
What human impacts are common across many freshwater system case studies? Give three examples of impacts using at least two case studies each
-Eutrophication due to nutrient input
-Ag runoff into Florida Everglades produces huge cattail blooms and eutrophication
-Flow alteration- water use for agriculture, consumption, construction of Dams, Levees
-three gorges dam on Yangtze River- flooding of upper portion of river: erosion & siltation, loss of wetlands & lakes, reduced temp. & O2 levels downstream which affects the fish and plant life.
- Yuba river dams and mining: dams prevent species such as the Chinook salmon from their full range, while mining releases large amounts of sediments, altering river formation
-Mesopotamian Marshlands: draining-over 70% gone
-diversion of water from Mono Lake for Los Angeles area
-Introduction of invasive species
- fish stocks at flathead lake, MO-extreme changes in foodweb
-introduction of Nile Perch to Lake Victoria- decline of native cichlid population
- Climate Change
- vernal pools-changes in both drought and rainfall would alter the presence of this type of wetland
-Florida everglades-same as above
- Channelization
- Missouri River
- Sacramento - San Joaquin Delta
Mesopotamian marshlands