EEMB 148: Midterm 2.0

what are the two sources of organic phosphorus?

1. drainage basin

2. some anthropogenic

what is an additional source of organic phosphorus?

pacific salmon: adults swim into freshwater to breed and bring organic phosphorus with them

some adult salmon die bc of the energy expended swimming upstream → death releases additional nutrients → increases algae → increase insects → more food for juvenile fish

what are the two forms of phosphorus?

1. dissolved organic phosphorus (ex. SRP)

2. organic phosphorus

what is the difference in algal versus bacterial uptake and storage of phosphorus?

bacteria: uptake P at low concentrations, cannot store it

algae: uptake P at high concentrations, can store it

what is inorganic turbidity in large lakes?

phosphorus sticks to suspended sediments due to concentration gradient

what does a large turbid river look like?

high sediment; low light; high P; low algal production

what does a large clear river look like?

low sediment; high light; low P; low algal production

what happens at a mixing zone for turbid and clear rivers?

P is able to desorb from the sediment due to change in concentration and becomes SRP → less sediment means more light is available → increased algal production

what is the nutrient spiraling concept?

the process in which nutrients are transported downstream and cycled in the system; helps to measure retentiveness

what is spiraling length?

the average distance traveled by a nutrient atom during one complete cycle

what is the equation for spiraling length? what happens if you increase V or decrease T?

S = V * T

increase V = longer spiraling length

decrease T = shorter spiraling length

what is the decomposition equation?

S = Sw + Sb

what is the in-theory equation for spiraling length in water?

Sw = Vw * Tw

how is the spiraling length in water actually measured?

flux vs. distance of a radioactive tracer

what is Kl?

Kl: slope of decline in flux with distance

larger Kl means greater uptake and shorter spiraling length

what is the rearranged equation for the spiraling length in water?

Sw = Fw / U

how does flux and uptake affect the spiraling length in water?

increase flux rate = longer spiraling length

increase uptake rate = shorter spiraling length

what is the in-theory equation for spiraling length in biota?

Sb = Vb * Tb

how is the spiraling length in biota actually measured?

measure the loss of a label/sample over time

what is Kb?

Kb: slope of decline in flux with distance

larger Kb means greater uptake and shorter spiraling length

what is the rearranged equation for the spiraling length in biota?

Sb = Vb / Kb

increase biota = shorter spiraling length

what value has a larger impact on spiraling length?

spiraling length in water

how does geomorphology affect spiraling length? (steep slope, sediment, sand)

steep slope = increase velocity, less uptake = longer spiraling length

lots of sediment = sinks, retained = shorter spiraling length

sand = smoother, less friction, moves faster = longer spiraling length

how does discharge affect spiraling length?

low flow = less velocity, high uptake = shorter spiraling length

how does algae and bacteria affect spiraling length?

lots of algae = more uptake = shorter spiraling length

lots of bacteria = more uptake = shorter spiraling length

how do sedimentary and mobile consumers affect spiraling length?

sedimentary = absorbs in one place, long life span = shorter spiraling length

mobile = messy eater, push things downstream = longer spiraling length

how is CPOM classified?

>1 mm, slowest downstream velocity

how is FPOM classified?

<1 mm to >0.45 um, intermediate downstream velocity

how is DOM classified?

>0.45 um, fastest downstream velocity

what is labile organic matter?

simple molecules, rapidly degraded, low C:N

what is refractory organic matter?

complex molecules, slowly degraded, high C:N

what is an allochthonous system? when are the pulsed inputs?

carbon fixed OUTSIDE the system

pulsed inputs: fall (plants drop leaves), early spring (melting of snow causes flooding)

what kind of food chain is associated with an allochthonous system?

detrital food chain - donor control

macrophytes enter through this web (toxic and well defended)

what is an autochthonous system? when are the pulsed inputs?

carbon fixed INSIDE the system

pulsed inputs: late fall (leaves fall, more light available), early spring (leaves haven’t grown back yet, more light available)

what kind of food chain is associated with an autochthonous system?

grazing food chain - top down effects

what is the order of the lability index?

periphyton > macrophytes > herbs vegetation > woody vegetation

what are the two assumptions of the RCC?

1. a gradient of physical characteristics exist from the headwaters to the tailwaters

2. organism distribution is determined by organic inputs and how they are processed

what are the two predictions of the RCC?

1. the relative importance of allochthonous, autochthonous, and downstream transport

2. community composition is based on mechanisms to harvest organic matter

what are the RCC characteristics of a headwater?

physical: small, high canopy, low light, cold, low turbidity, low velocity

energy: allochthonous, P/R < 1

biota: shredders and filter feeding collectors

fish: fusiform (reduce drag, cold adapted, eats insects)

what are the RCC characteristics of a midwater?

physical: intermediate size, intermediate canopy, intermediate light, warmer, intermediate turbidity, intermediate velocity

energy: autochthonous, P/R > 1

biota: grazers and filter & deposit collectors

fish: laterally compressed (increase agility, variable temp. adapted, eats everything)

what are the RCC characteristics of a tailwater?

physical: large, minimal canopy, high light, warm, high turbidity, high velocity

energy: downstream transport, P/R < 1

biota: deposit collectors

fish: dorsal ventrally compressed (stay near the bottom, warm adapted), fusiform (reduce drag, warm adapted, eats FPOM in water column)

what is the dominant carbon input in most rivers?

allochthonous inputs

how are desert streams, springs, slow rivers, and rivers with extensive floodplains exceptions to the carbon budget?

desert streams: no vegetation → auto

springs: clear water, low particulates → auto

slow rivers: sediment sinks, phytoplankton persist (division rate higher than flow rate) → auto

floodplains: shallow, sediment sinks → auto

what are the three limitations of the carbon budget?

1. no distinction between labile and refractory organic matter

2. indicates total input and output of organic matter

3. most organic matter is highly refractory

what are the percentages of the carbon budget?

25% processed in place

25% stored in sediment

50% lost downstream

what are the two ways that organic matter enters the food chain?

1. organisms (fungi, bacteria)

2. invertebrates (shredders, gougers)

what is the first step in CPOM break down? what percentage is lost and how long does it take?

leaching: all soluble materials dissolve

lose 25%

24 hours

what is the second step in CPOM break down? what percentage is lost and how long does it take?

mineralization: bacteria and fungi colonize and convert dead organics to living biomass

lose 50%

10 days

what is the third step in CPOM break down? what percentage is lost and how long does it take?

fragmentation: invertebrates process organic matter through maceration, abrasion, and defecation

lose 25%

100-250 days

what biomass is usually lost first?

labile biomass

what biomass takes the longest to lose?

refractory biomass

what did studies originally show about the impact of bugs on decomposition rates?

increase bugs = increase decomposition

what organisms are better at processing thin/flat leaves?

microbes = more surface area for them to colonize

what organisms are better at processing thick/wide leaves?

bugs = able to chop up the leaves

what were the results of the leaf pack experiment on decomposition? are there any possible alternative explanations?

fine mesh leaf pack excluded bugs → saw a decrease in decomposition rate

alternative: fine mesh prevented flow of nutrients, oxygen, and waste which would decrease decomposition

what was changed in the secondary experiment on decomposition? are there any possible alternative explanations?

used insecticide to kill all the bugs → saw a decrease in decomposition rate

alternative: decomposition of bugs increased the availability of nutrients which increased the decomposition rates of microbes

what is periphyton?

benthic algae

what is a biofilm made up of?

bacteria, fungi, algae in a polysaccharide matrix

what is the difference between epilithic, episammic, epipelic, and epiphytic?

lithic = rocks

sammic = sand

pelic = mud

phytic = plants

what are the characteristics of bacillariophyta?

diatoms: silica shell, rapid reproducers via asexual reproduction in constant environment, R-selected

what are the characteristics of chlorophyta?

green algae: absorb red light, rapid reproducers via sexual reproduction, all energy into growth

what are the characteristics of cyanophyta?

cyanobacteria: fix own nutrients, grazing resistant gel coat

what are the characteristics of euglenophyta?

euglenoids/phytoflagellates: part animal/part plant, heterotrophic, mobile with flagella

what are the characteristics of rhodophyta?

red algae: absorbs green light, deep water/shaded conditions, less competition

what are submerged macrophytes?

all photosynthetic parts are underwater

what are floating macrophytes?

all photosynthetic parts are above water

what are emergent macrophytes?

rooted in water, photosynthetic parts can be above or below water

what is the first way to measure biomass? what are the benefits or downsides?

ash free dry mass: weigh and combust

benefit = cheap, easy

downside = inaccurate as it measures ALL biomass

what is the second way to measure biomass? what are the benefits or downsides?

chlorophyll A: separate pigments based on concentration

benefit: more accurate

downside: more work, less effective in low light environments

what is the third way to measure biomass? what are the benefits or downsides?

cell volume: count every algal cell

benefit: extremely accurate

downside: really costly, highly labor intensive

what is the first way to measure productivity? what are the benefits or downsides?

light and dark chambers

benefit: easy, cost effective, less labor intensive

downside: measures community metabolism (underestimates NPP), reduces flow rate

what is the second way to measure productivity? what are the benefits or downsides?

radioactive carbon

benefit: more accurate

downside: expensive, assumes C14 uptake is the same as C12 (its not)

what is the third way to measure productivity? what are the benefits or downsides?

changes in biomass overtime

benefit: works great for macrophytes (more biomass = more productivity)

downside: does NOT work for periphyton (experiences more grazing) (increases secondary production)

how can we measure the biomass change of periphyton?

rate change in biomass = gain - loss

gain = immigration, growth rate

loss = cell death, emigration (sloughing, scouring, grazing)

what is the general model of algal biomass accumulation without grazers?

biomass: initially increases due to excess resources, then reaches a carrying capacity

division rate: decreases as algal biomass increases due to the decrease in resources

NPP: initially increases due to excess resources, then drops off as resources decrease

how does light impact productivity?

light limited: low light = critical resource = limits production

light saturated: algae absorbs the maximum amount of light = fueling production

photoinhibition: too much high energy light can damage the algal cells

what were the results for the open canopy stream from the Hill and Knight experiment?

open canopy stream covered with a tarp + added nutrients

results = no increase in biomass

stream is nutrient limited

what were the results for the closed canopy stream from the Hill and Knight experiment?

closed canopy stream had vegetation cut down + added nutrients

results = increased biomass

stream is light limited

what is hypothesis 1 regarding if nutrients limit algal growth?

high delivery rate despite nutrient is low → replaced by upstream sources

never feels the nutrient limitation

what is hypothesis 2 regarding if nutrients limit algal growth?

velocity gradient near the bottom

much slower in boundary layer → decreases delivery rate

means that delivery rate is dependent on the concentration of nutrients

what is the Redfield ratio?

the ratio in which a systen switches from being phosphorus limited to nitrogen limited

below 16:1 = N limited

what does the Redfield ratio look like in natural rivers?

below 10-30:1 = N limited

what are the three ways to manipulate nutrients?

1. nutrient diffusing substrata

2. experimental stream channels

3. whole stream additions

what is Liebig’s Law of the minimum?

growth of an organism is set by substrate in lowest supply relative to the needs of the organism

what were the conditions and results of the Grimm and Fisher experiment in desert streams?

desert stream = high P, low N

added only N = increase Chl A

added N+P = no further increase (since there is already P, cannot flip Redfield ratio)

what were the conditions and results of the Stockner and Shortreed experiment in PNW troughs?

PNW troughs = moderate N, low P

added only N = no change from control

added only P = increase Chl A (P was limiting and in most need)

added N+P = further increased Chl A (add P, now N is limiting - flipped Redfield ratio)

what are brushers? what are mobile brushers?

fast moving, takes the top off of algae

mobile brushers: fast resource tracking, removes LESS algae

what are raspers?

intermediate moving, grinds up food more than brushers

what are scrapers? what are sessile scrapers?

slow moving, pulls algae right off the rock

sessile scrapers: slow resource tracking, removes MORE algae

what is the general model for how algae respond to grazing pressure?

biomass: decreases since algae is being consumed by grazers

growth rates: initially there are excess resources per individual allowing for exponential growth → eventually reach peak efficiency and cannot divide anymore

NPP: initially enough resources to stimulate productivity and pack on biomass BUT not enough per unit area so it drops

what are the three experimental techniques used to measure herbivory?

1. insecticide treatments

2. artificial substrate

3. artificial stream channels

what were the Caddisfly results of the Hill and Knight experiment on the direct effects of herbivory?

caddisfly = scraper = bigger impact on algae

decreased Chl A, AFDM, bio volume

match to the model

what were the Mayfly results of the Hill and Knight experiment on the direct effects of herbivory?

mayfly = brusher = less of an impact on algae by only taking the top off

no change in Chl A, AFDM, bio volume

mismatch to the model (why? feeding apparatus)

what were the results of the Lambreti experiment on the effects of multiple grazers (Caddisfly, Snails, Mayfly) on herbivory?

⬆ grazers ⬇ biomass ⬆ growth rate

magnitude of effect: caddisfly > snail > mayfly

match to the model (fails the indirect effects)

what were the results of the Powers experiment on the indirect effects of grazing catfish on herbivory in Panamanian rivers?

low density of grazers = increased algae biomass (why? grazers bush away sediment allowing for light to reach algae)

high density of grazers = decreased algae biomass (why? grazers are consuming SO much algae that they cannot replenish their biomass)

mismatch to the model

what were the results of the Dudley experiment on the effects of Caddisfly on Cladophora in SPRING?

smooth tile: ⬆ caddisfly = ⬇⬇ cladophora (why? smooth = easier to consume)

rough tile: ⬆ caddisfly = ⬇ cladophora (why? harder to eat the algae due the grooves in the tile)

match to the model

what were the results of the Dudley experiment on the effects of Caddisfly on Cladophora in SUMMER?

⬆ caddisfly = ⬇ epiphytes = ⬆ cladophora (why? missing a trophic level; cladophora grows into a bigger filament making it harder to eat; removal of epiphytes provides more light and nutrients to cladophora)

mismatch to the model

what does adding light and nutrients do to a closed system?

increases algal biomass

what does adding light and nutrients do to a open system?

no effect on algal biomass (why? rapid immigration of grazers)

what were the results of the Steinman experiment adding light to an open system in a SHORT time scale?

match to the model (no change in biomass, increase in grazer density)

increased growth rate due to secondary production by grazers