MARS2014 Lecture Notes - Lecture 1: Phycoerythrin, Osmosis, Symplast
Unit 1: Primary Production
1. What is primary production?
o The transformation of light and sugar / inorganic nutrients to make energy
o Net Primary Productivity (NPP) is the energy output remaining for respiration – the
difference between the Gross Primary Productivity and the autotroph's energy
needs
2. What are the biggest contributors to primary production?
o Oceanic phytoplankton (93%)
o Coastal phytoplankton
o Microphytobenthos
o Coral reef algae
o Macroalgae
3. What is photosynthesis?
o Light hits a plant's chloroplast, splitting water into oxygen and hydrogen
o Several chemical reactions take place to produce ATP
4. What are the requirements for photosynthesis?
o Light
o Nutrients
5. What is chemosynthesis and where do chemosynthetic organisms live?
o Conversion of inorganic matter into energy, usually done by bacteria
o Chemosynthetic organisms live in a range of environments, from cool to 200°C
temperatures, in shallow environments and on hydrothermal vents (transient
environments) at the bottom of the ocean
6. What is Dai’s Paado and what are the two ways this is dealt with?
o Darwin's Paradox is that the majority of primary production is done at the surface of
the oceans, where there is most light, but also few nutrients
o The nutrient/light separation: at the depth where there is approx. 1% of surface light
intensity, there is approx. 50% of the nutrients
o Upwelling: When Ekman Transport (or the friction of wind on the surface of the
water) causes water to move in one direction, but as the ocean gets deeper the
frictional force becomes less and the Coriolis force skews it (to the right of the wind
direction if in the Northern Hemisphere, and to the left if in the Southern
Hemisphere).
▪ When Ekman Transport occurs near the coast and the Coriolis force directs it
away, to replace the displaced water, nutrient-rich water must be drawn up
from underneath, which brings up nutrients for photosynthesis and creates
COASTAL UPWELLING
▪ When Ekman Transport happens at the equator, the Coriolis force sends
water in the same direction (I.e. does not deflect it) - due to rotation of
equator. It simply moves to either side of the equator.
o Eddies: when friction between the continent and a strong current occurs, a change
in atmospheric pressure causes change in sea level and depth – driven by Coriolis
force
▪ In the Southern Hemisphere, cold-core eddies rotate clockwise and warm-
core eddies rotate anti-clockwise
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▪ In the Northern Hemisphere, cold-core eddies rotate anti-clockwise and
warm-core eddies rotate clockwise
▪ UNFORCED EDDIES are caused by atmospheric pressure, where the
thermocline is displaced upwards, bringing nutrient-rich water closer to the
surface
▪ FORCED EDDIES are caused by and rotate faster due to currents, which
displaces the thermocline further and sucks water up to the reef
7. What is adaptation?
o A trait developed to enhance fitness in a species
8. What is trade-off?
o No species can be a super species
o To adapt to one condition, a species must reliquish another trait or environmental
condition
▪ A trade-off might be exposure to desiccation, more competition, more
predators, fewer food sources
9. Who are the (7) key players in photosynthetic communities?
o Mangroves
o Seagrasses
o Algae
o Microphytobenthos
o Attached large seaweeds
o Phytoplankton
o Bacteria & Archaea
10. Hard and soft substrates
o Which organisms live in hard substrates?
▪ Macroalgae (live in both but prefer hard)
▪ Coral
▪ Microphytobenthos
o Which organisms live in soft substrates?
▪ Macroalgae
▪ Seagrass
▪ Microphytobenthos
▪ Mangrove
▪ Salt marsh
11. Which ecosystems/primary producers are important in the blue carbon cycle?
o Mangroves
o Seagrass
o Salt marshes
o They are all highly productive ecosystems and good at sequestering carbon
o They live in anoxic soil which prevents other organisms from using the carbon
12. Mangroves
o What are they/who are the key players?
o Mangroves are marine angiosperms (flowering plants)
o The grey mangrove (Avicennia marina)
o The red/river mangrove (Rhizophora)
o What is their environment?
o They live in the intertidal zone (between mean tide and highest tide,
submerged/inundated approx. 50% of the time)
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o Soft sediment with high nutrient concentration, sheltered from large wave
action
o What kinds of mangrove forests are there?
o Forests associated with estuaries
o Forests on river deltas
o Forests on coastal embayments
o Forests on lagoons
o How are mangroves classified?
o By size and species composition
o As
▪ Tall riverine forests
▪ Seaward fringing forests
▪ Scrub forests (when mangroves are at thermal limits, <2m tall)
o What is their global distribution?
o Correlates with shallow coral reef distribution (tropical to sub-tropical) but
extends a little further north and south
o Most of their diversity is in the coral triangle
o Need a low wave energy (unlike coral)
o What influences mangrove zonation?
o Salinity
o Tidal inundation
o Nutrients
o Wave action
o What are their ecosystem services?
o They fix CO2
o The ae the kides of the oea --> clean up nutrients and remove any
suspended sediments
o Their roots provide a 3D structure and habitat for organisms --> this structure
also provides traction for soil and slows tidal water, in doing so trapping
sediments and nutrients
o Their dropped leaves in the sediment powers the detrital food cycle, which is
important for all the organisms in the sediment
o How have mangroves and salt marshes adapted to living in a salt environment?
o Some species limit uptake of salt through their roots
▪ e.g. Rhizophora
▪ This specialised mechanism to restrict salt uptake uses a "symplastic
over apoplastic transport", where the spaces around the cells (the
apoplast) through which nutrients can usually flow freely through are
blocked off, so that transport of nutrients into the roots can be
mediated by the symplast on the inner side of the cell membrane
o Some species have salt glands in their leaves
▪ e.g. Avicennia
▪ Salt is toxic to the cytoplasm so plants secrete it into their vacuoles and
expel it through their leaves
▪ This is not a trait associated with salt tolerant plants
o All mangroves use both mechanisms to a degree, but prioritise one over the
other
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Document Summary
1% of surface light intensity, there is approx. Hemisphere): when ekman transport occurs near the coast and the coriolis force directs it away, to replace the displaced water, nutrient-rich water must be drawn up from underneath, which brings up nutrients for photosynthesis and creates. Coastal upwelling: when ekman transport happens at the equator, the coriolis force sends water in the same direction (i. e. does not deflect it) - due to rotation of equator. It simply moves to either side of the equator: eddies: when friction between the continent and a strong current occurs, a change in atmospheric pressure causes change in sea level and depth driven by coriolis force. In the southern hemisphere, cold-core eddies rotate clockwise and warm- core eddies rotate anti-clockwise. Why do mangroves need oxygen: oxygen allows metabolism and growth. It alters the availability of nutrients (nitrificiation occurs in the presence of elevated levels of oxygen)
