Methods in Oceanography Flashcards
microscopy
1mm - 3 micrometer
Flow cam
1mm - 6 micrometer
Flow cytometry
20 micrometer - 0.5 micrometer
molecular barcoding problems
data base incomplete, DNA content variable among species/difficult to quantify
what do you measure with biomass, bulk measurements
POC > 0.7 micrometer, Chl a > 0.7 micrometer
POC measurement problems
Unspecific for photosynthetic organisms
Concentration of Cal a depends on
irradiance, amount of nutrients present, composition and phytoplankton size
What does an argo float measure?
Temperature, Salinity, Chl a, carbon, nitrate
Remote sensing
Satellite sensors estimate cal a from irradiance leaving the water.
How does remote sensing work?
Chl a absorbs sunlight in red and blue waves. The irradiance that leaves the water becomes greener, depending on the chl a concentrations.
Remote sensing can also measure
Organic carbon pool, Photophysiology, composition
bloom
increase in biomass above a treshold
phenology
timing of periodic biological events as influenced by the environment
Phases of a bloom
Start day, intensity, duration
Limitations of remote sensing
Cloud an sea ice cover, high altitude in winter not measurable bc of low sun angles, Coastal not reliable due to detritus and sediments, satellites are expensive, no vertical profile, needs validation by in situ data
Why not measure POC or chlorine a as indicator for primary production in the ocean?
POC can be zooplankton, chl a reflects composition and physiological changes, growth = loss, growth < loss, cal a concentration can change due to mixing.
Gross primary production (GPP)
Total rate of organic carbon produced by autotrophs
Respiration
Energy used for maintenance and growth (10-20% of GPP)
Net Primary Production NPP
Total organic carbon production minus respiration of autotrophs
Oxygen evolution, Winkler technique
Light bottle: respiration and photosynthesis, dark bottle: respiration –> measure amount of oxygen used
disadvantage winkle technique
Inaccurate due to long incubation, includes respiration heterotrophs
Carbon assimilation
add 14C labeled bicarbonate, measure 14C incorporated in organic carbon.
Issues with 14c incorporation
Unnatural irradiance, unnatural irradiance, extracellular release of DOC ignored.
active chlorophyll a fluoresence
Measure electron transport rate through photosystem 2
Global ocean productivity is estimated by combining
Biomass, irradiance, in situ productivity vs irradiance measurements
