Biogeochemistry Flashcards
marine biogeochemistry
the study of physical, chemical, geological, and biological processes that govern the composition of the ocean
across evolution and time
nutrient
a substance that provides nourishment essential for growth and the maintenance of life - help form structural parts of organisms such as shells
- helps produce energy
- stimulate primary production
- limiting
macronutrients (definition)
present in relatively large amounts, used to generate energy or to incorporate into tissues for growth and repair
micronutrients/trace elements (definition)
smaller amounts, subtle biochemical and physiological role sin cellular processes
Macronutrient cycle
N as No3- and P as PO4 3- dissolved in seawater
consumed by plankton in upper ocean
returned to dissolved state deeper in ocean when plants die, sink, decay
continents provide much of these nutrients through processes like river runoff
Origins of oceanic iron
Dust from atm
sediment dissolution along continental margins
fluids from hydrothermal vents
glacial sources
Importance of O2
produced by plants when converting inorganic materials to biomass
- biomass used as nutrition for consumers
consumed by bacteria and animals
- respiring organisms and bacterial oxidation of organic detritus consume O2
Processes impacting O2 distribution
Exchanged at sea-air interface
- solubility of O2 decreases as temp increases
- polar oceans take up O2 and tropical oceans release
O2 produced in upper ocean and consumed in interior ocean
- O2 rich surface water does not mix readily with deeper water
O2 transported to interior by ocean circ
Distribution of O2 in ocean
Highest surface O2 concs found at high altitudes because ocean is cold, well-mixed, and ventilated
Lowest at mid-lats on eastern boundaries because weak supply die to sluggish circ, elevated O2 consumption due to productivity, O2 depletion in depths 100-1000m
Importance of carbon
animal and plant biomass cocnsist mainly of carbon
plant-like organisms assimilate C into Co2
C produced through respiration
changes in state through metabolism
storage and exchange
- particulate and dissolved inorganic (nonliving things)
- p and d organic (living)
carbon chemistry
CO2 does not only dissolve in seawater but also reacts with water as it dissolves
(1) Gaseous CO2 dissolves in seawater and gets hydrated to form aqueous CO2
(2) Aqueous CO2 reacts with water to form a free proton (H+) and a bicarbonate ion (HCO3−)
(3) Bicarbonate ion dissociated into a free proton (H+) and a carbonate ion (CO32-)
As CO2 dissolution in seawater releases free protons, CO2 acts as an acid (proton donor) in seawater
see equations
physical carbon pump
air-sea interface
solubility
exchanges also depend on wind and atm CO2 conc
carbon transported to interior through subduction and formation of water masses
vertical circ acts as pump bt transferring DIC from surface to depths
once in the deep ocean, DIC remains there for a long time
C also brought to surface by upwelling
biological carbon pump
in the upper ocean, C is consumed through photosynthesis - DIC gets incorporated into plant-like orgs as org matter
when orgs die, their dead cells and shells sink - may reach sediment, may be remineralized
org matter oxidized into DIC
as a result of the bio pump, the upper ocean is poorer in DIC
carbonate counter pump
in upper ocean, orgs produce CaCO3 through calcification
- releases CO2
When they die and sink, there is a flux of CaCO3 toward deep ocean and some reaches sediments and is buried
some dissolves
DIC distribution
At the surface, DIC concentration are higher at high latitudes than low latitudes
→ Due to the physical pump (high solubility and upwelling)
At the surface, DIC concentration are higher at high latitudes than low latitudes
→ Due to the physical pump (high solubility and upwelling)
