Organism responses to high pCO2 and low pH Flashcards
(35 cards)
How does the change in CO2 concentration (ppm) in the past 30 years vary when looking at the atmospheric trend vs the oceanic trend?
Much greater variability in the ocean.
Which seawater variables have changed as a result of increasing CO2 concentration in the ocean?
- Seawater pH
- Co3 2- concentration
What was the starting point in terms of looking at organism responses to the higher pCO2 and lower pH in seawater?
Royal Society report in 2005
- This linked carbonate chemistry changes to biological impacts such as those on calcifiers. - - (Before this studies only focused on carbonate chemistry itself)
Which organisms were first studied when looking at biological responses to OA? Why might this be a strategic choice?
Calcifying organisms.
These may have been used to find negative effects to make a political statement.
What physiological responses to OA other than calcification can be studied? How did these compare to studies on calcification in 2009?
- Photosynthesis
- Nitrogen fixation
- Reproduction
These were limited in terms of research when compared to calcification in 2009.
What is the general impact of OA on calcifying organisms?
They are generally negatively affected (e.g., reduced calcification, increased dissolution).
How does OA affect primary producer biomass?
It generally increases due to more available CO₂ for photosynthesis.
What does a 1° producer mean?
A primary producer
What is the trend in taxonomic diversity under OA conditions?
Decreases — fewer species dominate.
Do all species respond negatively to OA?
No — some species thrive in high CO₂ environments, especially opportunistic ones.
Does OA affect organisms the same at all life stages?
No — effects vary with life stage.
What changes are likely to occur in a coral reef/carbonate reef under OA conditions?
↑ Bioerosion
↑ Macroalgal overgrowth
↓ Calcifier recruitment & structural complexity
↓ Taxonomic diversity
↕️ Community structure (change)
What changes are likely to occur in a seagrass meadow under OA conditions?
↑ Primary productivity
↑ Grazing by herbivores
↓ Competition from macroalgae
What changes are likely to occur in a pelagic food web under OA conditions?
↑ Harmful algal blooms
↓ Secondary productivity
↕️ Community structure & primary productivity (varies)
In molluscs, which life stage is more sensitive to OA in terms of survival?
Larvae are more sensitive than adults - adult survival was higher than larvae
How does calcification respond to OA across life stages in molluscs?
Adults show more calcification reduction than larvae.
Which life stage shows greater changes in metabolism under OA in molluscs?
Larvae, with more dramatic decrease in metabolic rates.
In molluscs, which life stages exhibited reduced growth under OA conditions?
Larvae and juveniles
How did different pH scenarios impact sea urchin larvae? Is the same observed in warming scenarios?
Reducing pH (from 8.1 to 7.8) caused the larval structures to break down.
The same was observed under warming even at normal pHs.
What are the two main observations of reducing pH for the Mediterranean mussel - why might this be useful initially?
- Metabolic depression
- Reduced growth
This can allow reduced energy consumption - conserving it during stressful conditions (however, in the long run this can have significant impacts).
What was observed in the brittle star under reducing pH conditions and why might this response occur?
Metabolic up-regulation -> to maintain/increase calcification and compensate dissolution with increasing seawater acidity (observed small increase in calcium content of arm).
Why might the responses of brittle stars to reducing pH be costly? What does this mean for the longevity of responses?
The metabolic upregulation was observed to cause:
- Significant muscle reduction in the arms (potentially due to reduced energy to muscle structures with increasing calcification rate)
- More brittle arms (less mobile)
Upregulation is therefore not a long-term process (more long-term studies are needed to study multiple factors).
How was biological sound production found to change in reducing pH conditions? Where was this study performed and why?
- Reduced biological sound overall (declining frequency, intensity and bandwidth)
- Reduction in snapping shrimp snaps
This was carried out at vent sites (where temperature was constant, meaning only pH effects were measured).
How were predator prey interactions expected to change in OA conditions between eastern oysters and mud crabs? Why?
Increased predation by crab as oyster calcification would reduce, making them easier prey.
