Lecture 11-Ocean primary productivity III Flashcards
What are the 3 major nutrients for phytoplankton?
-Nitrogen, Phosphorus, Iron= most limiting
What is the limiting resource for diatoms?
-Sillicon
Why are vitamins a limiting resource for some phytoplankton?
-some cannot make them (auxotrophic) -whereas some can make them (autotrophic)
What are the major nutrients phytoplankton need?
• carbon • nitrogen • phosphorus • oxygen • silicon • magnesium • potassium • calcium
What are the trace nutrient phytoplankton need?
• iron • copper • vanadium • zinc
What are the organic nutrients the phytoplankton need?
-vitamins
How do nutrients occur?
-dissolved or particulate form
What is the marine snow?
-“marine snow” can drive nutrients out of the photic zone - dead phyto and zooplankton usually sink - can aggregate to larger particles - exopolymers from diatoms (acidic polysaccharides) enhance aggregation - transport nutrients toward the sea floor
What is Nitrogen mainly needed for?
-protein synthesis
In what three forms does Nitrogen occur in the sea?
- ammonium (NH4) - nitrate (NO3) - nitrite (NO2)
What is the Nitrogen cycle in the sea?
- N available in three forms (80% of air is Nitrogen)
- cynobacteria can fix N2 into ammonia denatrification= sources of N in water converted back to atmosphere
What is Phosphorus required for?
-required for energy cycles (ATP) and nucleic acids
In what form does Phosphorus occur in the sea?
- inorganic phosphates (PO4) - dissolved or particulate phosphorus
What are the non-ocean sources of Phosphorus?
non-ocean sources are weathering of rocks carried as river sediments
What is the phosphorus cycle in the sea?
-
What is the N/P ration in the ocean and in phytoplankton and what does it suggest?
-NITROGEN/PHOSPHORUS ratio in ocean 14.7 : 1 -Phytoplankton NITROGEN/PHOSPHORUS ratio 16 : 1 -Suggests phytoplankton growth, decomposition and recycling controls ocean N and P levels. -Also suggests that N is limiting
What is Iron needed for?
don’t need as much but is essential -iron is involved in releasing oxygen in photosynthesis -important fo rthe enzyme that fixes nitrogen in cyanobacteria - important in redox reactions - iron in O2 emitting step of photosynthesis - required for nitrogen fixation in cyanobacteria
What is the Iron in the sea from?
- soluble iron (Fe2+) is not very available - plankton may release chelators to help with its capture –major source of Fe is dust being blown across the ocean
What are chelators?
-aid in capturing Fe2+
In what form and from where is Silicon available in the sea?
- available as silicic acid - delivered to oceans by wind and river transport from land - upwelling important for recycling
What is silicon used for and when is it limiting?
- polymerised by diatoms to form silica cell wall - often limiting during diatom blooming events
Where do phytoplankton get vitamins from?
– most phytoplankton require some vitamins that they cannot synthesis - bacteria likely produce the bulk of these - different requirements and availabilities can favour one group over another (autotrophic vs auxotrophic)
How does cell size and surface area affect nutrient uptake?
-small cells= more surface to absorb nutrients= better -bigger cells do better when lot of nutrient availability -dinoflagellates= make their surface bigger= invagination into the cell=like lungs= so larger surface -the colonies= with mucilage, the elements dissolve in it and better accessible -sometimes stored in granules, so when you need it
How does cell movement and mixing affect nutrient uptake?
- motile cells can migrate to better nutrient sources (e.g. dinoflagellates, or cyanobacteria) - diatom spines can cause microturbulences to disperse patches of nutrients -long spines in diatoms= helps them mix the watre and get more nutrients stable water column creates advantage for motile cells -combined with excess nutrients can often lead to nuisance blooms or harmful algal blooms
