lecture 13: global trends, spatial and temporal scales of marine production

kaiser book chapter 2

oceanography book chapter 9

introduction and scales in the ocean

plankton → drifter/wanderer = all living organisms too small to swim against currents. not a very strict term
zooplankton = animals living in the water column
phytoplankton = plants (often single celled) algae living in the water column
plankton = zooplankton + phytoplankton + others (e.g. bacterioplankton)
best way to separate plankton is through size classes (refer to previous lectures)

inorganic material that is converted to organic material through photosynthesis
bacteria and algae is in a cycle of the microbial loop, where the bacteria is basically at the base of the foodweb
- basal production (algae + bacteria)
gross primary production (GPP) = photosynthesis ≈ algae
- calvin cycle and the enzyme rubisco that are resonsible for light to be converted into biomass
- and this includes macroalgae too
- the process is not only governed by light but also nutrients that are available
bacterial production = general term; all bacterial cells that assimilate (in)organic chemicals for biomass production
- they use up oxygen whereas the algae produce the oxygen

resources (bottom up)
- light
- nutrients (N, P → most abundant compounds after carbon)
- trace elements (Fe, etc)
- temperature
- salinity
top down controls:
- predation by zooplankton or larger cells in general
- bacteria/parasites
- death
- species selection (diversity)
- these factors act at different scales
when a cell dies, a part of the cell gets taken up byt he microbial loop and the rest sink down into the sediment

compensation depth → respiration equals photosynthesis
euphotic layer → are where there is enough light for photosynthesis to occur
- temperature structure → when the light heats up the upper layer, causing stratification of the top layer of the water from the lower layers
- this can happen also cause of salinity and density
chlorophyll maximum →
- chlorophyll os used as a proxy to indicated phytoplankton biomass
- most places on earth are nitrogen limited, and in few rare cases phosphorous limited

oceanographic provinces (Loghurst)
oceanic gyres
- their limits are shaped by the continents
- what drives the gyres:
  - in the north the gyres go clockwise and in the south they go anticlockwise
- north atlantic gyre
  - western boundary currents
  - e.g. gulf stream
- south atlantic current
  - upwelling on the east side
  - brazil current
  - benguela current
  - different communities
mediterranean sea
- oligotrophic/nutrient poor
upwelling
- west coast of continents
- often dominated by diatoms in the warm water blooms along the coasts or where teh currents run
- why/how does upwelling happen?
  - wind + coriolis →ekman spiral
- equatorial upwelling
downwelling
- top water goes down and the top becomes nutrient poor, and the deep gets nutrient rich water
- wind from south in the northern hemisphere
mesoscale -
- english channel
  - algae bloom
  - effect of turbulence
  - coccolithophore blooms
- baltic sea
  - cyanobacteria blooms

chlorphyll blooms deviating north and south depending on season
multi-year scale oscillation like el nino and la nina
- la nina → surface water is more cooler and more productive
- el nino → surface water is warmer, bad for fish farm and stocks
- these are linked to trade wind changes
- el nino
  - blocks upwelling
  - phytoplankton decrease
  - lower fish capture
  - year to year change in intensity
climatic change
- ALOHA station
- found an increase in chlorophyll levels - dont know exactly why
annual scale - spring bloom
- diatoms
- dinoflagellates
- depends on latitude
  - temperate
  - tropical
  - arctic
  - polar
    - in winter it is a chemoautotrophic based food web
    - spring → release of DOM
    - summer → photoautotrophic based foodwebs
monthly scale
- neap tide → where there is less gravitation pull from the moon so the tidal movements are minimum in height
- spring tides → where there is a lot of gravitational pull from the moon so the tidal movements are maximum in height
daily scale
- unique to marine systems

challenger expedition
profiles over 5 year periods
surface sampling:
- bucket
- nets
vertical profile sampling:
- bottles on a rosette, with niskin bottles that can be closed at different depths and controlled closing by the boat/ship computer
- CTD (conductivity, temperature, depth)
eularian method
- measuring only in one spot and measuring changes
- e.g transect, grid sampling
langrangian method
- measuring in multiple different places and measuring changes
- e.g. drifting bouy, which follows teh water current over time and measures the changes/characteristics through out the entire active time
each of these processes have different advantages
satellite view sampling
- ……..
- limitation:
  - only can see surface changes
  - depends on cloud cover
  - really fucking expensive
multi instrument strategy:
- ship
- fixed bouy
- drifting floats
- gliders
- mammals