Biol 432 Flashcards
How to calculate lake distance
Distance between 2 furthest points
How to calculate lake width
max. distance perpendicular to length
What is fetch and what does it represent
Distance over which wind can blow (L, (L+W)/2, surface area)
a) thermocline depth and b) depth to which particles will be resuspended
What is shoreline development
D = the ratio of the length of the shore line to the length of the circumference of a circle of area equal to that of the lake
What is indicated on a bathymetric map
max depth, volume, mean depth (V/A)
What causes water movement
wind, differential heating/cooling of water body, influx of water into lake
What are the two major types of water movement
Waves= exhibit periodicity but have little to no forward flow Currents= lack periodicity but exhibit unidirectional flow
What defines waves
Wavelength (L) = distance between two wave crests Height (H) = vertical distance between wave crest & trough
Amplitude (a) = deviation in vertical axis from mean position
Period = time required for passage of two crests across a fixed point
Frequency = inverse of period
How do waves break on shore
vertical movement becomes a horizontal one :
< 0.5 wavelength (L)
Why does the wind cause such a large pile-up in the thermocline and only a small pile-up of surface waters?
The larger the density differences (more stability), the smaller the amplitude
Density difference between surface water & air is 1000-fold different whereas as the density difference between the epilimnion & hypolimnion is very smal
What happens when the wind stops blowing?
A long wave -aka internal seiche and a surface seiche
importance of internal seiche
transport of nutrients, water, and organisms from hypolimnion to epilimnion(and vice-versa)
How does N enter lake water?
Gas exchange, direct deposition (acid precipitation) and runoff (fertilizer)
What are the elements in the N-cycle
nitrification, denitrification, N-fixation, uptake and excretion & deposition
For algal uptake, what are the fastest and slowest forms?
Fastest : NH4
Slowest : N2
What are the reactions inside bacterial or algal cells ?
nitrate reduction and N-fixation
Describe n-fixation
N2 - NH4+
Anaerobic process
Requires a lot of energy (N N)
Facultative: N fixation only when other sources of N are limiting
N-fixers: Heterotrophic bacteria and Photosynthetic cyanobacteria
Describe n-fixated cyanobacteria
have a competitive advantage at low N:P ratios
frequently form mass blooms in late summer
Why are lakes typically P-limited and the oceans typically N-limited?
- Availability of MoO42-(molybdate) probably plays a role.
- Chemical binding properties of MoO42-are very similar to SO42-(sulfate).
- SO42-is in high concentrations in marine salt waters but not in freshwater.
- SO42-competitively inhibits the uptake of Mo which is needed for nitrogen fixation (part of the nitrogenase).
- input from the atmospheric N pool is lower in marine and other saline systems than in freshwater
Why is DIC important in lakes?
- Source of CO2 for photosynthesis (hence, CO2is the raw material used to build organic matter)
- However: Carbon is almost never limiting primary production (P and N are)
- Weak acidic reaction with H2O
- changes pH in lakesDetermines buffering capacity of lakes
- Interaction with Ca: Hardness , Buffering
What is the rule of thumb with organic matter?
50% is carbon
Where to find elements in carbon cycle
CO2 : atmosphere
C : biosphere
POC/DOC : hydro/geo
Fossil fuels and limestone : geosphere
Describe carbon cycle
Respiration Photosynthesis Bacterial respiration Decomposition Combustion Fossilization Erosion Deposition
Where do very acidic lakes get their acidity?
Receiving acid from acid rain, mine drainage,volcanic eruptions, pyrite (iron sulfide) in catchment, etc.(the responsible acid is most often sulfuric acid)
Bogs
Describe calcite precipitation
Is often biogenic:
High photosynthesis - high pH - precipitation
Occurs typically in late summer (sometimes every year)
Calcite can remain suspended
lakes looks milky, called a “whiting” event
Calcite can accumulate at lake edges, called “marl”
Calcite can encrust macrophyte
Carbonate is a what?
Lakes that have a lot of carbonate can resist changes in pH with the addition of acids
The ability to resist changes in pH with respect to the addition of acid is called
- Alkalinity or(better)
- Acid neutralizing capacity-ANC
Lakes in limestone regions have high buffering capacity and are therefore not as impacted by Acid Rain. Lakes on granite are highly impacted
What are the major ions in lakes?
Cations: Ca, Mg, Na, K
Anions: CO3, HCO3, Cl, SO4
How to measure ions?
- each ion is measured separately (via ion chromatography)
- Conductivity of the water sample is measured
- Total dissolved solids (TDS) = weight of water sample that has been filtered and then left to evaporate at temperatures ~ 100 oC
When is a lake considered saline?
Several categories proposed, one commonly used in Canada by Hammer et al. (1986)
• Freshwater < 3,000 mg/L or < 5, 500 S/cm
• Hyposaline*3 – < 20 g/L or 5.5 – 30 mS/cm
• Mesosaline‡20 – 50 g/L or > 30 – 70 mS/cm
• Hypersaline> 50 g/L or > 70 mS/cm
What factors influence
A) Climate & Hydrology – evaporation-driven
B) Weathering of soils and rock
C) Atmospheric precipitation & fallout
D) Human activities
How much does road salt contribute to salinization of surface water
51%
Why study light in lakes?
- light provides energy
- animals use it for vision, orientation
- heat lake
Light and niche partitioning
- Pigment composition determines competitive outcome
- Coexistence in white light
- Partitioning of the light spectrum (“red” and “green” niche
Solar radiation
UV = little energy, dangerous
visible light = half of daily energy, PAR
Infrared = half of daily energy, transfer of heat
How do you measure light
- Photon flux density
- Unit based on number of photons per area and time
- equivalent to energy flow ( J m-2d-1), but wave length must be known for conversion
What affects light reaching surface of water?
- latitude and season
- time of day
- altitude
- meteo
Movement of light in lake
- solar radiation
- reflection (albedo)
- scattering
- absorption
what affects reflection from lake surface
- angle
2. surface characteristics (waves, snow/ice)
describe vertical light attenuation?
A constant fraction of light is absorbed(transferred to heat) with each increase in depth, meaning an exponential decay of light with depth
affected by light intensity at surface and depth, depth and wavelength
light and the colour of lakes
- Blue light is also most prone to scattering – Rayleigh Rayleigh scattering (of intensity I): blue, clear water
- Suspended particles in water change these relationships: Blue light is rapidly attenuated - green light is transmitted best
- In humic or turbid waters: all short wavelengths are absorbed - red, orange dominate
- The lake water itself may be coloured: Coloured organic material, bacteria, anorganic substances (e.g. iron)
what is the euphoric zone?
phytoplankton photosynthesis > phytoplankton respiration): 1 % of incident radiation remains
Why study the distribution of heat in lakes?
- Biochemical reactions are temperature-dependent
- growth and reproduction
- Heat distribution affects the movement of water
- distribution of nutrients and organism
Why is heat not distributed like light?
- density anomaly in water
- wind that moves water masses
Difference of heat in lakes in clear lakes
The epilimnion of clear lakes (less attenuation per metre) tends to be deeper and colder than that of lakes with lots of particulate matter or coloured lake
Impact of climate change on lake tanganika
- Increased temperatures (peak in last 1500 years)
- sharper density gradient in mixolimnion
- impedes vertical mixing
- Reduced nutrient availabilty (stored in the monimolimnion) and reduced oxygenated layer
- Reduced primary productivity despite larger euphotic zone
- Reduces higher order productivity (fish yield)
What is CA/LA?
catchment area/lake area
• CA:LA provides an index of the relative importance of atmospheric vs. watershed loading of allochthonous material
• Lakes with highCA:LA tend to be more nutrient rich
• In CA:LA, one would not include the LA in the CA estimate CA/LA
How does the dead zone form?
1) Nutrient-rich river inputs promote algal growth in Gulf
2) Algal decomposition occurs in salty zone, mixing of water column prevented b/c of thermal and salinity gradient
How large is the hypoxic zone?
Size of Lake Ontario
What happened to the Aral Sea
4th largest lake, now only 15% diverted for cotton cultures Separate bodies now lost a lot of the biodiversity became more saline not drinking quality no longer a regional climate regulator
What is a lantic and a lotic system?
lantic = standing lotic = flowing water
Differentiate stream and river
Streams– tend to be cool, shallow and often have gravel & stony beds- typically contain clear, flowing water- alternating sequences of riffles and pools
Rivers- are warmer, deeper and have silty bed- lack riffle and pools
What are the characteristics of streams and rivers?
- Flow is undirectional
- Dynamic environments:Channel morphology and substrate undergoing constant change
- Energy flow:Much of the organic matter supporting stream metabolism can be from allochthonous sources
- High spatial and temporal heterogeneity: Flow (as well as DO and water chemistry) are primary regulators of life in running waters
- Many lotic organisms have specialized adaptations to live within running waters
Where do stream studies take place?
Hubbard Brook
Findings from Hubbard Brook?
- more acid in rivers than precipitation (from dry deposition and sulfate from watershed)
• Conducted simultaneous measurements of chemical inputs and outputs, which could then be used to derive mass-balance equations for the watersheds
1) Undisturbed sites analysed over long-term show:net retention(precip. inputs > stream outputs) of H+, N, Cl, Pnet losses (precip. inputs < stream outputs) of Ca, Mg, Na, K, S, Si, & Al
2) Experiment deforestation revealed major hydrological effect,and impacts on microbial activity and nutrient cycling, eg.decomposition and nitrification accelerated leading to greater export of H+and NO3
Describe stream food web
- Fish are dominant organisms in open water
* Invertebrates dominate stream benthos, greatest densities in riffles
Some generalities regarding aquatic insect lifecycles:
- larvae/nymphs usually the most lengthy part of lifecycle
- very few adults have a completely aquatic lifecycle
Adaptations of invertebrates to stream life
- In areas of predictable annual flooding, many insects will have evolved such that they emerge just prior to flood
- Drifting behavior at night allow invertebrates to new habitat without risk of being eaten by visual predators
what are shredders?
feed on leaf litter and twigs (aka coarse particulate organic matter: CPOM) and associated microbial and fungal community
Family Gammaridae, Subphylum Crustaceae
what are collectors?
feed on fine particulate organic material (FPOM), which consists of finer plant fragments or suspended plankton
Caddisfly and blackfly
what are grazers?
feed on periphyton (= attached algae, fungus and bacteria)
water penny and mayfly
what are predators?
feed on living animal tissue
Giant water bug, dobsonfly
Macroinvertebrates role in ecosystems?
- Benthic inverts. process 20 – 73% of leaf litter inputs into headwater streams (Covich et al., ‘99)
- Benthic inverts. are an important source of foodfor fish residing in streams
- Benthic inverts. modify nutrient transport in streams and terrestrial environment
What is the river continuum concept?
model for describing the structure and function of communities along a riversystem
What are techniques to assess environmental change?
- historical records + ancestral knowledge
- modeling
- Natural archives
How do sediments get into lakes?
allochtonous: pollen, aerial transported contaminants and soil particles
autochtonous: algae and aquatic insects
What is the paleo approach?
- Select study lake
- select coring site and core
- Section and date core
- sub sample and isolate indicator of interest
- Collect indicator data
- Analyze data
What factors can be addressed using paleolimno?
- Acidification
- Eutrophication
- Anoxia and fish habitat
- Climate change
- Changes in salinity
- Fire history
- History of organic pollutants
- Etc.
How do we collect cores?
Gravity Core
Close interval Sectioning
Freeze coring
Livingston piston coring
How to date cores?
C or radiocarbon (old) Pb (150 years) Cs (nuclear peak in the 1960s) Tephrachronology (volcano) Pollen (known veg history) Varves episodic events
Example indicators:
- Diatoms
- Cladocera
- Chironomids
- Chrysophytes
- Pollen
- Isotopes
- Sedimentary Chla
- Non‐motile metals
- Paleo DNA
- Charcoal
What makes a good indicator?
- Preserves well in sediment
- Abundant
- Morphologically distinct
- Reliable indicator of environmental condition
Diatoms indicate what?
Found all over the world (marine and freshwater species)
•Are often one of the dominant primary producers in freshwaters
•Well defined optima and tolerances for a suite of environmental conditions
•pH, nutrients, salinity •Climate•Habitat ➤periphyton
•Thermal stratification ➤planktonic vs. benthic
Chrysophytes indicate what?
Also siliceous algae
•2 types of remains•Scale
•Cyst
•> 1000 described species
•Single cells or colonies
•Most have flagella
•Are motile
•Found in the plankton (open water) of lakes
Typically inhabit low nutrient, low temperature, unpredictable climates
•Such as Arctic, Antarctic, and Alpine lakes•Most common in slightly acidic, low nutrient lakes
•Cyst to diatom ratio –coarse indicator of nutrients, ice cover, salinity (cysts)
•Commonly used to track•pH, nutrients, climate
What are animal indicators?
- An intermediate or upper trophic position
- Answer questions that algal indicators can’t
- Different restrictions on growth
- Oxygen
- Predation
- Macroinutrients, cations
Paleolimnological Cladoceran Studies reveal what?
- Resurrection ecology‐Hatch buried resting eggs ‐Analyze historical populations directly
- Trophic interactions‐Multi‐proxy analysis‐Comparison of direct‐monitoring with the sediment record
- Ca decline in softwater Ontario lakes‐Cladocera as paleoindicator of lakewater Ca
Describe eutrophic
High in nutrients High primary production High biomass of primary producers Low transparency Low hypolimnetic O2 Hypolimnion dominated by midge Chironomus(Thienemann)
Describe oligotrophic
Low in nutrients Low primary production Low biomass of primary producers High transparency High hypolimnetic O2 Hypolimnion dominated by midge Tanytarsus(Thienemann)
Describe primary production and dissolved oxygen method
DO(initial) – DO(dark) = Respiration
DO(light) – DO(initial) = Net Photosynthesis
DO(light) - DO(dark) = Gross Photosynthetis
What are TP classifications
Ultraoligotrophic<5 ug/l Oligotrophic5-10 ug/l Mesotrophic10-30 ug/l Eutrophic30-100 ug/l Hypereutrophic> 100 ug/l
How are productivity and trophic state are related to basin morphometry.
comparing volume of lake and volume of hypolimnion
epi/hypo < 1 means oligo
epi/hypo > 1 means eutro
What are reasons for cultural eutrophication?
- Use of fertilizers
- Increased population density
- Increase in (untreated) human wasteIncrease in use of detergents (after WW II)
- Most lakes are P limited. Addition of P led to increased algal growth
- Both human waste and early synthetic detergents were high in phosphoru
how to abate cultural eutrophication?
- nutrient reduction (Legislation to reduce nutrient content of inflowing water, Wastewater treatment, Diversion of nutrient-rich water)
2) P precipitation
3) Harvest of macrophytes
4) Dredging of sediment
5) Hypolimnetic aeration
6) Lake drawdown
7) Selective discharge of hypolimnetic water
8) Biomanipulation
Point vs non-point?
Point: any single identifiable source of pollution from which pollutants are discharged, such as a pipe, ditch, ship or factory smokestack” (EPA definition)
Non-point: nutrients are difficult to control because they come from many different sources and locations
Summary of eutrophication
Eutrophication is a process that scientists have been studying for about 100 years.
Major advances have been made in controlling point sources
Non-point sources continue to be a major issue
Major challenge for the next century: meeting the demands of feeding the planet while maintaining adequate water quality
What is trophic control?
In bottom-up models nutrients control community organization by controlling plant numbers. Also known as donor-control
In top-down models, predation is the structuring factor because predators control the number of herbivores. Also known as trophic cascade
What is biomanipulation
A lake improvement procedure that puts trophic cascade theory into action to reduce phytoplankton biomass (especially nuisance blooms) and to increase water clarity
How did Shapiro and Wright (1984) convince readers that biomanipulation as was at least partly responsible for increased water transparency?
Ran in-situ mesocosm experiment where Daphnia densities and nutrients altered but their treatments not replicated
What were Carpenters conclusions?
In the Planktivore Lake, phytoplankton were stimulated more by enrichment than by release from zooplankton grazing.
In the In the Piscivore Lake, the positive effect of enrichment was lessened by the increased grazing pressure from zooplankton
A 1-mm change in mean zooplankton length had about the same effect on chlorophyll as a decrease in P input rate of 1 ug Lg L-1 d-1.
Among lakes (in general) the range of zooplankton lengths ≈ 1 mm, whereas the range of P input is substantially > 1 substantially > 1 ug Lg L-1 d-1.
Therefore, the potential for increasing for increasing eutrophication by P input exceeds the potential for controlling eutrophication by food web manipulation.
Other reasons biomanipulation might be unsuccessful
- predator avoidance
- phytoplankton composition shift to inedible algae
- planktivorous fish are not the only zp predators
- many fish switch from planktivory and piscatory
- Highh recruitment of young-of-the-year fish follows reduction of planktivorous fish
Current thought on biomanipulation?
manipulation is only expected to be successful if the P loading is below a certain threshold (~ 0.6 g m-2 a-1), e.g. in oligotrophic and mesotrophic lakes.
The decrease of in-lake phosphorus is an indispensable prerequisite for long-term reduction in phytoplankton biomass.
