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
What are the metabolic differences in cells and how does that aid nutrient uptake?
-metabolic differences: some cells are good at fast nutrient accumulation in high nutrients enviroments, others are good at scavenging from low nutrient environments
How do cells use storage and nutrient concentration to aid nutrient uptake?
-sometimes stored in granules, so when you need it
What do cyanobacteria do when not enough nutrients on the surface?
cyanobacteria= if not enough nutrients at the top, at night sink to more nutrients and float back to the light during the day
What is the seasonal phytoplankton succession?
- Seasonal changes in phytoplankton dominance is known as phytoplankton succession E.g. spring-summer bloom in temperate- boreal regions
1. Autotrophic diatoms first - large diatoms may occur first with high nutrients (because they are autotrophic, can make all their vitamins (vital))
- auxotrophic diatoms may follow
- smaller diatoms as nutrients diminish
- as water column becomes stable diatoms may sink out
- dissolved silica depletion contributes to end of bloom
2. Dinoflagellates occur after diatoms - often require organic nutrients of earlier bloom
- prefer stable water column
- many are heterotrophic
3. Herbivores prevalence places further pressure on phytoplankton
How is the diversity of phytoplankton affected by succession?
-Diversity of phytoplankton tends to increase as succession continues
How is change in size in phytoplankton used as a defense against predators?
-if you can make yourself bigger= harder to eat, make a chain of cells= bigger or make yourself bigger with spines (like diatoms) or horns on dinoflagellates -gooey colony with mucilage=plus harder to penetrate
How are toxins/inhibitors in phytoplankton used as a defense against predators?
-cyanobacteria, dinoflagellates, haptophytes, diatoms, cann all produce noxious substances that can inhibit predation, and sometimes the growth of other phytoplankton
How are warnings/distractions in phytoplankton used as a defense against predators?
-bioluminescence = the sparks in water! -distract predators
How are behaviour changes in phytoplankton used as a defense against predators?
dinoflagellates in chains swim faster, and encounter predators more often - when copepods are present, chains break down and dinoflagellates swim more slowly
What is the seasonal phytoplankton succession like in the arctic?
-don’t get the second bump, takes longer for sun to penetrate the ice etc. so the first bump starts later
What is the seasonal phytoplankton succession like in the tropics?
-less seasonality with light availability = still peak of algae and peak of herbivores
How does upwelling affect geographic distribution of primary productivity?
-continental shelf and open ocean -may be seasonal due to winds (brings nutrients back to the surface) -continental shelfs can cause upwelling (obstacle for ocean currents and displace the water) = sea mountains do that too
How do coastal nutrient sources affect geographic distribution of primary productivity?
-after storms, dust storms as well, but murky water right next to the coast so the highest phytoplankton productivity is higher a bit off the coast as the euphotic zone is deeper
How do ocean fronts/convergences affect geographic distribution of primary productivity?
-masses of water run into other masses of water (currents)= have mixing and can bring nutrients brought up back to the top
What is the nutrient situation in ocean centres and gyres?
-nutrient poor
