lecture 14 (phytoplankton eco-physiology) Flashcards
why are phytoplankton so important on earth?
they form large blooms,
influence atmospheric chemistry and biogeochemistry of nutrient cycling,
fix about 1/2 of total carbon fixed by photosynthesis,
represent the base of food chains supporting marine mammals, birds, and fisheries,
form oil and siliceous and limestone deposits
describe the biological carbon pump:
CO2 is reduced in surface waters and fixed into organic matter by photosynthesis,
organic matter passes from producers to consumers through respiration and bacterial decomposition of organic matter
ultimate deposition locks the C away in sediments (carbon sequestration)
atmospheric CO2 -> algae -> consumers -> sink -> deposition/remineralization -> sequestration
what is the difference between PP and phytoplankton biomass? how do you measure them?
primary productivity: the rate at which food is incorporated, yields biomass eg. g O2 produced/L, gC/m2/d (measured with fluorescence, satellites etc.)
phytoplankton biomass: standing stock (set number, not rate) eg. cells/L or chla/L
what is NPP
net primary productivity (GPP-respiration)
what is GPP
the total PP
what is a phytoplankton bloom
an accumulation of phytoplankton biomass in a particular area
how is size relevant to phytoplankton eco physiology?
as they grow larger, the SA:V ratio decreases, since SA increases to radius squared and thus it increases slower than volume. This is relevant since a high SA/V ratio allows for faster nutrient exchange
why is a smaller size beneficial?
because it corresponds to a high SA/V ratio, allowing for faster and more nutrient exchange, and faster growth rates
how does SA to volume ratio change with algal size
smaller size has a higher SA/V ratio
larger size has a smaller SA/V ratio
this is because Volume changes with radius cubed, and SA changes with radius Square
how does size affect sinking?
larger cells sink faster, smaller cells are more buoyant
what are adaptations to avoid sinking (5)
gas bubbles, lipids, oils, spines, chains
explain the importance of considering spatial and temporal scales in phytoplankton ecology
different parts of phytoplankton ecology occur at different scales of time and space.
abundance of phytoplankton depends on time and space
spatial scale
what volume or area (eg. how much volume)
temporal scale
how often a bloom occurs (eg. what season)
describe how certain aspects of the aquatic physical environment affects phytoplankton
density changes with temperature and salinity
increasing salinity increases density and lowers freezing point, keeping phytoplankton more buoyant
temperature increases lower density, causing phytoplankton to sink faster
give four examples of nutrients essential for phytoplankton and their roles in physiology
Nitrogen -> amino acids, chlorophyll, nucleotides
Mg -> chlorophyll
Si -> diatom frustules, scales, stomatocyst walls,
S some amino acids, nitrogenase, thylakoid lipids, carrageenan, agar, DMSP, biotin
how much light makes it to the surface
50% of light
what wavelength penetrates deepest? shallowest?
blue penetrates deepest in water column
red is shallowest
what impacts the depth that light reaches in the water column
clarity of the water (particulate/dissolved matter scatters light more quickly)
location (deeper in offshore, shallower in coastal)
what is radience
the light that is visible
what is the base of the euphotic zone
depth with 1% of incident light remaining
draw a temperature profile, and a chlorophyll profile
both are straight down at surface (mixed layer), temperature decreases from then.
chlorophyll increases slightly below the surface, then decreases to 0 (too bright/no nutrients at surface, too dark further down)
what is a langmuir cell
water with streaks of white lines parallel to one another
water masses spinning in localized area, upwelling and downwelling cells beside one another
how does water motion impact phytoplankton
horizontal water motions concentrate/disperse phytoplankton patches
vertical motion affects sinking and nutrient supply
turbulence has species dependent effects
define net growth rate
controlled by growth and loss
define gross growth rate
rate of reproduction (only growth, does not include death rate)
compare phytoplankton biomass in northern hemisphere tropic, temperate, and polar oceans over a year
tropical stays low all year round, stable
polar peaks only in summer (june, july/august) since usually not enough light (only enough for short period of time, when less ice)
temperate has spring and fall blooms (larger in spring, smaller in fall)
draw how light, nutrients, and zooplankton effect/interact with the temperate ocean phytoplankton bloom cycle. label whether they are bottom up/top down
phytoplankton has a peak in spring and fall. nutrients are high in winter, lowered with bloom and low through summer until fall, when they start to go up again (plateauing briefly during fall bloom) -> bottom up
sunlight is low in winter, high over spring to fall (peak in summer) -> bottom up
zooplankton have lower, and slightly delayed blooms after phytoplankton blooms -> top down
sketch logistic and exponential growth. how are these different? which occurs in nature/lab?
exponential growth: occurs in lab. biomass increases exponentially to infinity
logistic growth: occurs in nature, exponential increase to a certain carrying capacity (K), then plateaus, with an optimal yield of 1/2 K
equation for net growth rate
r = mu-lambda
(net growth rate = gross growth rate - death rate)
draw the relationship between photosynthesis and irradience in phytoplankton
increasing light to a certain point increases PP, and then PP decreases again (too much light causes photodamage)
when light is lowered, PP decreases, and reaches the compensation point where light is 1% of surface light and respiration and PP are equal
what is the compensation point
when Respiration = Production, NPP=0
when <1% of visible light remains (compensation light intensity)
describe the Michaelis-menten model
nutrient uptake from the environment (algae growth curve)
quick uptake to a certain point (saturation), then plateaus
x-axis = nutrients (concentration nutrient), y-axis = nutrient uptake/cell/min)
describe the droop model
growth as a function of internal nutrient stores and quotas. quick growth until reaches max growth rate
Q0= minimal subsistence quota, Q = internal pool/quota of nutrient
y-axis = growth rate, x-axis = Qxmol/cell
describe the Monod model
growth as a function of external nutrient supply
increases to a maximum growth rate.
x-axis = nutrient concentration, y-axis = growth rate
how do you calculate net growth rate of phytoplankton population by using exponential or logistic growth models?
for exponential: gross growth rate - death or loss rate.
if no loss then net growth rate = gross growth rate. r can be estimated from slope of ln N vs time plot
for logistic growth: use (K-N/K) to estimate (as N approaches K, this approaches 0, when N is small, close to 1
how do you calculate doubling time
for exponential growth:
doubling time (td) = ln2/r
How do you calculate divisions per time?
for exponential growth,
divisions per unit time = 1/doubling time
What parameters of the photosynthesis-irradiance relationship are commonly used to determine the success of some phytoplankton species relative to others?
amount of net production/uptake (maximum K), as well as the speed of uptake/growth
how do you determine the compensation depth on a graph of photosynthetic rate vs depth?
the compensation depth is where the Respiration line and photosynthesis curve intersect (or where Net PP is 0)
using a michaelis-menten model, how can you determine which species would out compete another for the limmiting nutrient?
depends on high or low nutrient concentrations.
when low nutrient concentrations, the one that uptakes faster will dominate.
when nutrients are high, the one that has higher overall growth/uptake rates will dominate
describe general loss processes in phytoplankton populations (7)
grazing, perennation, sedimentation, death/morality, parasitism, washout, competition
Compare the general relationships and the effects to energy transfer of a marine food web dominated by larger phytoplankton cells (e.g. diatoms) with one dominated by picophytoplankton. Where in the oceans are these different types of food webs commonly found?
the larger the phytoplankton (base of food chain), the shorter the food chain, and more efficient. (cold, temperate/boreal, coastal upwelling zones)
intermediately sized plankton have medium length chains, occur in subtropical gyres, summer/stratified temperate oceans
smaller cells (picoplankton) have longer, less efficient chains (coastal/eutrophic waters)
