Productivity Flashcards
what drives the productivity in the ocean?
plankton and coastal macroalgae (kelp forests)
what are phytoplankton?
- microscopic algal cells that use chlorophyll to photosynthesize, uses sunlight and nutrients to make proteins, fats and carbs
- live in upper part of ocean where sunlight hits
what are zooplankton?
microscopic to macroscopic animals that graze on phytoplankton
how are phytoplankton distributed?
discontinuous patches
- non-random clumped population
- concentrated at interfaces between water bodies
what color on a map shows the highest productivity?
- red
- most nutrients
why are there patterns of productivity?
- turbulence and current transport at many spatial scales (conveyor belt, marginal seas)
- different physical conditions seasonally and spatially
->light, temp, salinity - spatially discontinuous levels of grazing by zooplankton - food is patchy
- localized reproduction -> max and min productivity depends on sunlight
what is the main cause of productivity?
turbulence or mixing
what causes spreading and mixing?
currents and wind
what causes Langmuir circulation?
currents converging
what causes eddies?
currents and coastlines
what do seasonal patterns depend on to cause differences?
latitude
- depending on the sunlight phytoplankton are either abundant or non-existent which causes zooplankton to fluctuate
which latitude has consistent levels of phytoplankton?
tropical
describe the mixing depth in the winter
- storms mix water to a greater depth
- less light
- light doesn’t reach as deep so nutrients are deeper
describe the mixing depth in spring
- water is mixed less
- more light
- light penetrates further
what changes as a result of mixing depth?
blooms and declining phytoplankton
compensation depth
photosynthesis = respiration
- above this depth is where phytoplankton photosynthesize
mixing depth
depth to which water column is mixed by winds
determines critical depth
-> more respiration than photosynthesis
critical depth
depth above which total oxygen produced in the water column = total oxygen consumed
- more respiration = more zooplankton to control phytoplankton = no bloom
what happens when the mixing depth is less than critical depth?
bloom
what happens when the mixing depth is more than the critical depth?
no bloom
what happens as a result of winter mixing?
brings nutrients to the surface
what happens in spring sun to the bloom?
heats water and less mixing by wind so thermocline develops and cells are in nutrient rich calmer water = bloom
how do you catch plankton?
plankton net
- cod end - name of tube at the end that catches plankton
why do we study plankton?
carbon cycle -> phyto = uptake
zoo -> respiration
what nutrients do phytoplankton need for growth?
- nitrogen
- phosphorus
- silicon
- iron
what is nitrogen used for?
make proteins
what 3 forms does N come in?
ammonium -> excretion by animals in water column (taken up the fastest)
nitrate - most abundant
nitrite - less common
what does nitrate and nitrite need?
need enzymatic reduction to convert to ammonium
- nitrate reductase and nitrite reductase
how is N formed?
new production - deep waters by mixing or upwelling
regenerated production - nutrients derived from excretion in surface waters
nitrogen fixation - some algal phytoplankton cells
purpose of P
- synthesis of ATP
- required for lipids, DNA, fats/oils
what forms do P come in?
- dissolved inorganic phosphate
- particulate phosphorus from sediments/rivers
- some dissolved P in organic molecules
redfield rations
- constant ratio of N:P = 16:1 in oceans
- phyto have 16:1 ratio
- ocean have 14.7:1 ratio
- nitrogen fixation by some plankton might make difference
why is the ratio of N to P constant in all ocenas?
residence time of nutrients way longer than mixing time of oceans
where does P come from?
land
why is Si needed?
for diatom skeletons
- from land by weathering
what is Fe used for?
cofactor in oxygen production step of photosynthesis
- crucial in parts of ocean where N is not limited
what are the areas of where N is not limited called?
high nutrient/low productivity areas (HNLP)
where are HNLP found?
antarctic ocean
north Pacific
how do Si and Fe enter oceans?
by wind as dust
where is a major source of iron dust?
Sahara
what controls phytoplankton growth?
bottom up feeding
what are organic trace substances important for?
auxotrophic
how is C produced at the ocean surface taken deep?
physical: mixing at poles
- taking dissolving CO2 down with cold saline water
- bringing up CO2 from deep
biological: productivity
- taken up into phytoplankton by photosynthesis
- eaten and moved down as organic matter
who eats most of the carbon?
zooplankton and nekton
carbon sink
sinking water
- ecosystems where C is sequestered
what are Larvacean houses?
big structures of mucus and cellulose that allow filter feeders to get C
how is C transported to the seafloor?
larvaceans
how is C caught?
- put traps for sediment
- caught larvacean houses
how many blooms do polar regions have?
1
how many blooms do temperate regions have?
2
