Ocean Productivity Flashcards
the gulf stream has very high productivity due to:
the interaction between the gulf stream and neighboring colder waters (mixing/ turbulence)
the center of gyres has __ (high/ low) productivity
very low b/c no mixing
t/f
productivity in the oceans is driven entirely by plankton
false
mostly plankton, but also by coastal macroalgae such as kelp forests
phytoplankton=
where do they live?
microscopic algal cells that use chlorophyll to photosynthesize, using sunlight and nutrients to make protein, fat, carbohydrates
they live in the upper part of the ocean where sunlight reaches
zoopolankton=
microscopic or macroscopic animals that graze on phytoplankton
does plankton occur uniformly around the ocean?
no
occurs in spatially discontinuous patches
(sometimes concentrated at interfaces b/w water bodies)
what 4 things control plankton abundance/ patterns of productivity?
- turbulence and ‘current transport’ at many spatial scales (mixing)
- different physical conditions seasonally and spatially (light, temp, salinity)
- spatially discontinuous levels of grazing by zooplankton
- localized reproduction
____ is the main cause for productivity
- currents and winds cause ____ and ___
- currents converging cause ___ ___
- currents and coastlines cause ___
turbulence (mixing)
- spreading and mixing
- langmuir circulation
- eddies
Explain how Langmuir circulation works. What are some impacts of it?
currents converge, causing circular circulation & localized mixing
Results in higher productivity because of the mixing
- This is where you see lines of birds etc eating the plankton at the lines of convergence
Seasonal patterns in plankton abundance differ depending on latitude.
Explain the plankton patterns in the arctic
Arctic:
1 bloom per year
- starting to get 2 blooms b/c waters are warming
phytoplankton bloom first, zooplankton bloom follows
Seasonal patterns in plankton abundance differ depending on latitude.
Explain the plankton patterns in temperate locations
Temperate:
eg BC coast
- 2 plankton blooms
- zooplankton deplete the first phytoplankton bloom, but phytoplankton come back for a second bloom as zooplankton numbers drop
Seasonal patterns in plankton abundance differ depending on latitude.
Explain the plankton patterns in tropical locations
Tropical:
- not enough mixing= no obvious blooms
- depends on nutrients
- can have localized blooms after a storm etc if there are enough nutrients
In winter, storms mix to a ____ (greater/ lesser) depth that in spring
greater in winter
Blooms and declines of phytoplankton are due to changes in mixing ____
depth
Explain the differences in light and mixing depth in the winter vs spring
winter:
- storms= water mixes to a greater depth
- less light= light doesn’t reach as deep
spring:
- water is less mixed
- more light= it penetrates further
Compensation depth=
where photosynthesis= respiration
- phytoplankton photosynthesize above this depth above
Mixing depth=
depth to which the water column is mixed by winds
- determines the critical depth
- moves phytoplankton down
Critical depth=
depth above which total oxygen produced in the water column= total oxygen consumed
if the mixing depth is ____ (<, > or =) critical depth, then phytoplankton cells can photosynthesize –> bloom
mixing depth < (less than) critical depth
mixing depth > critical depth= _____ (bloom/ no bloom)
no bloom
not sure why
explain the steps that happen that allow a spring plankton bloom to occur
- winter mixing brings nutrients to the surface
- spring sun heats the water & less mixing by wind= a thermocline develops
- phytoplankton cells are now in nutrient-rich, calmer water = BLOOM!
How do we catch plankton to study it?
Plankton nets
-“Cod End”= the name of the tube at the bottom of the net that catches plankton
List 4 of the main nutrients (+2) that phytoplankton need for growth
- Nitrogen
- Phosphorous
- Silicon
- Iron
- Trace elements like Mn, Zn, etc
- Organic trace substances (vitamins etc)
Nitrogen is used by phytoplankton for making ____ and it occurs in 3 dissolved forms:
1
2
3
which of these 3 is taken up the fastest?
proteins
- ammonium (NH4): excretion products (TAKEN UP FASTEST)
- nitrate NO3: most abundant dissolved form
- nitrite (NO2): less common form
ammonium is the easiest form of nitrogen to be taken up. How are nitrate and nitrate taken up?
Both require enzymatic reduction to convert to ammonium
Nitrate + nitrate reductase = nitrite
Nitrite + Nitrite reductase = ammonium
Then ammonium is the usable form
What are 3 ways nitrogen can be acquired for use?
- new production: from deep waters (mixing or upwelling)
- regenerated production: nutrients derive from excretion in surface waters
- nitrogen fixation: by some algal phytoplankton cells
_____ is required by phytoplankton for lipids, DNA, fats/ oils, and synthesis of ATP
It occurs in water mainly as dissolved inorganic ____ (___)
phosphorus
inorganic phosphate (PO4 3-)
where does oceanic phosphorus mainly come from?
the land! plants and soil
also
bubbles/ foam in ocean= broken up lipids of planktons (phosphorous)
The ratio of nitrogen to phosphorous is constant in all the oceans. Why?
What is the ratio?
Because the residence time of all these nutrients is way longer than the mixing time of the oceans (~1000yrs)
Ratio is 16N: 1P
Silicon is required for diatom ___ and it’s a ___ nutrient in the oceans
Where does it come from?
skeletons
limiting
Comes from the land (rocks) by weathering
Iron and silicon often enter the ocean as ___
dust
___is a cofactor required in the oxygen production step of photosynthesis
iron
Iron may be crucial in parts of the ocean where ___ appears not limited
- this means iron is a ____ factor
- these areas are called:
list 2 examples of areas that fall into this category
nitrogen
limiting
high nutrient/ low productivity areas (HNLP)
eg
-parts of the Antarctic ocean
- north pacific
Explain the controversial experiment with iron that took place off Canada’s west coast
they dumped iron into the ocean to increase productivity (because iron was a limiting nutrient)
- fishery success and productivity sky rocketed, but it was not sustainable (eventually Si becomes the limiting factor)
T/F
phytoplankton cannot synthesize organic compounds
true
organic trace substances still important for auxotrophic etc
Carbon produced at the ocean surface is taken into the deep by 2 different methods: physical and biological. Explain each
Physical: mixing at the poles takes dissolved CO2 down with cold saline water
Biological: (productivity)
- taken up into phytoplankton by photosynthesis
- they’re eaten and moved down as organic matter (falls as marine snow/ in diatoms etc)
Not all carbon produced makes it to the deep sea. Where is the missing carbon?
Larvacean houses!
these houses filter out food from the water column, and when they get full, the animal abandons the house and it drops to the seafloor, brining with it all the food (carbon!) caught in it
Phosphorous in the oceans comes from ___ and ____. Redfiled ratios are ratio of __ to __ (16:1 near shore) .
Redfeild ratios are constant due to short ___ time of oceans relative to ___ of the nutrients from ____ and ____
land and rivers
N to P (16:1)
mixing
input
land and rivers
