Lecture 14: Ocean acidification Flashcards
ocean acidification does this mean oceans are acidic
- NO, most extreme future forecast is pH = 7.8 (alkaline)
- only small changes
pH is a measure of
hydrogen ions on a log scale
acidification is ___ and ___
steady and ubiquitous
__ is naturally exchanged at the vast interface between the atmosphere and the ocean
CO2
– some remains as dissolved gas, remaining binds with water to form carbonic acid
chemistry: of ocean acidification
CO2 + H2O H2CO3
- carbonic acid dissociates into H+ and bicarbonate ions,
- hydrogen also binds with carbonate ions to form bicarbonate
- – reduction in carbonate ions in seawater
chemistry of ocean acidification in words
- increased bicarbonate ions, reduced carbonate ions and pH
carbonate important for marine life why?
- many organisms build hard parts i.e. shells, skeletons
- various forms of calcium carbonate are used
- organisms must be able to extract dissolved calcium and bicarbonate ions from seawater
producing calcium carbonate it emits
CO2
– positive feedback (more carbonic acid –> bicarbonate ions / CO2 and carbonate ions –> bicarbonate ions)
aragonite
important form of calcium carbonate for organisms i.e. reef-building corals
saturation state =
calculates how hard organisms find it to produce their calcium carbonate hard parts
saturation state >1 and <1
> 1 supersaturation, solid calcium carbonate present, favoured and plenty of CaCO3 available, shell building is easy
<1 undersaturation, dissolved ions favoured, solid calcium carbonate scarce, shell-building difficult, sea water will break down structures
areas of the world suitable for coral reefs are
declining, due to carbonate conc
ocean acidification in Deep time general
- world has had high CO2 in past
- oceans have had much lower pH in past
AND LIFE HAS SURVIVED
ocean acidification across geographical time
- varied, pH has been lower before
ocean acidification for past 2 million years
pH is lower than has been
- predicted to decline further
