Reefs under stress: Nutrient environment Flashcards
From the PAG example, how much is diversity expected to reduce by under stress?
Could be a 90% diversity reduction
What needs to be remembered when using specific case studies to predict future conditions, such as diversity, globally?
- Climate change can vary between regions
- Multiple other abiotic factors will change, such as ocean acidification, nutrients etc. This may mean that predictions/case studies are no longer relevant.
Where are coral reef ecosystems associated with in terms of nutrient conditions globally? What is this theory and why is this surprising?
This shows a clear distribution of nutrients – the corals are associated with oligotrophic regions/nutrient desserts.
Darwin Paradox.
This is surprising as corals have photosynthetic algae, suggesting nutrients are required to thrive.
Give some examples of macromolecules that N and P are crucial for in organisms.
- Nucleic acids (e.g., DNA)
- Proteins (amino acids each connected with a peptide bond, containing N)
- Phospholipids
- ATP = energy storage and transport
(3 P and 5 N)
What are the two major forms of nutrient uptake (hint: this varies with type of nutrient)
- Plants take up dissolved inorganic forms
- Animals take up particulate organic forms
What are examples of Dissolved Inorganic Nutrients?
Nitrate, phosphate and ammonium
Where are dissolved inorganic nutrients from in coral ecosystems?
Upwelling and currents (e.g., remineralised nutrients from depth)
Release by reef organisms (e.g., sponges)
Terrestrial run-off (e.g., fertilisers, excrement)
Where are particulate organic forms of nutrients from in coral ecosystems?
Currents and migration (e.g., zooplankton DVMs)
Release by reef organisms
Growth in reef ecosystems (e.g., reef plankton communities, larvae etc.)
Main particulate forms of organic nutrients in coral reefs.
Bacterioplankton, phytoplankton and zooplankton
How are sponges useful in nutrient release in reef systems? What form are these nutrients released as?
Sponges and other filter feeders graze on bacterio- and phytoplankton and remineralize the organic N to inorganic N.
The re-release of the nutrients in their dissolved inorganic form in the vicinity of corals can represent the most significant import pathway for new nutrients to reefs.
What exchanges occurs between symbionts and corals?
Coral feeds on particulate organic N/P and produces inorganic N/P waste. This is transferred to symbionts.
The symbiont takes up dissolved inorganic N/P and produces organic C and some organic N. Large amounts of org C, small amounts of N and very little P are transferred to the coral.
How can corals survive in regions with no particulate food? What is an example of this?
Thought to digest symbionts, with organic nutrient (N/P) increases in corals matching losses of symbionts.
Example:
Increased access to dissolved inorganic N from seabird guano results in increased coral growth rates (birds release a lot of nutrients into the seawater etc.).
50% of coral host N can be traced back to guano-derived N and thus to the primary uptake by the symbionts.
This suggests that the symbiont digestion is an important import pathway for coral nutrients.
What is the Redfield Ratio?
C : N : P = 106 : 16 : 1
What is environmental stoichiometry?
The relationship between quantities of elements in the environment, specifically nutrients, on the functioning and composition of an organism exposed to this environment.
What is Leibig’s Law of the Minimum? (think of the barrel)
The water in the barrel represents growth. The barrel can only fill to the shortest plank (limiting nutrient), before overflowing.
There is always a limiting nutrient, if N is no longer limiting then the next most limiting nutrient controls growth (e.g., P).
How does the bleaching threshold change in regions with nutrient enrichment?
The bleaching threshold lowers to a colder temperature.
This is because other nutrients, such as P, become limiting - an imbalance.
Upon P limitation: This results in an emergency reaction, reallocating P in the cell (e.g., replace phospholipids with sulpholipids). This is fine under normal conditions, but under warmer conditions, sulpholipids behave differently in the membrane and can cause increased bleaching with lower thresholds.
How do high nutrient/chlorophyll affect symbiont division?
In increased nutrient conditions, the symbiont cells quickly divide as no longer limited. With increasing cells, the demand for other nutrients also increases.
E.g., Increased N-supply promotes population growth – more P is needed.
