Lecture 11-Ocean primary productivity III

Question 1

What are the 3 major nutrients for phytoplankton?

Answer 1

-Nitrogen, Phosphorus, Iron= most limiting

Question 2

What is the limiting resource for diatoms?

Answer 2

-Sillicon

Question 3

Why are vitamins a limiting resource for some phytoplankton?

Answer 3

-some cannot make them (auxotrophic) -whereas some can make them (autotrophic)

Question 4

What are the major nutrients phytoplankton need?

Answer 4

• carbon • nitrogen • phosphorus • oxygen • silicon • magnesium • potassium • calcium

Question 5

What are the trace nutrient phytoplankton need?

Answer 5

• iron • copper • vanadium • zinc

Question 6

What are the organic nutrients the phytoplankton need?

Answer 6

-vitamins

Question 7

How do nutrients occur?

Answer 7

-dissolved or particulate form

Question 8

What is the marine snow?

Answer 8

-“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

Question 9

What is Nitrogen mainly needed for?

Answer 9

-protein synthesis

Question 10

In what three forms does Nitrogen occur in the sea?

Answer 10

• ammonium (NH4) - nitrate (NO3) - nitrite (NO2)

Question 11

What is the Nitrogen cycle in the sea?

Answer 11

• 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

Question 12

What is Phosphorus required for?

Answer 12

-required for energy cycles (ATP) and nucleic acids

Question 13

In what form does Phosphorus occur in the sea?

Answer 13

• inorganic phosphates (PO4) - dissolved or particulate phosphorus

Question 14

What are the non-ocean sources of Phosphorus?

Answer 14

non-ocean sources are weathering of rocks carried as river sediments

Question 15

What is the phosphorus cycle in the sea?

Answer 15

-

Question 16

What is the N/P ration in the ocean and in phytoplankton and what does it suggest?

Answer 16

-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

Question 17

What is Iron needed for?

Answer 17

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

Question 18

What is the Iron in the sea from?

Answer 18

• 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

Question 19

What are chelators?

Answer 19

-aid in capturing Fe2+

Question 20

In what form and from where is Silicon available in the sea?

Answer 20

• available as silicic acid - delivered to oceans by wind and river transport from land - upwelling important for recycling

Question 21

What is silicon used for and when is it limiting?

Answer 21

• polymerised by diatoms to form silica cell wall - often limiting during diatom blooming events

Question 22

Where do phytoplankton get vitamins from?

Answer 22

– 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)

Question 23

How does cell size and surface area affect nutrient uptake?

Answer 23

-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

Question 24

How does cell movement and mixing affect nutrient uptake?

Answer 24

• 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

Question 25

What are the metabolic differences in cells and how does that aid nutrient uptake?

Answer 25

-metabolic differences: some cells are good at fast nutrient accumulation in high nutrients enviroments, others are good at scavenging from low nutrient environments

Question 26

How do cells use storage and nutrient concentration to aid nutrient uptake?

Answer 26

-sometimes stored in granules, so when you need it

Question 27

What do cyanobacteria do when not enough nutrients on the surface?

Answer 27

cyanobacteria= if not enough nutrients at the top, at night sink to more nutrients and float back to the light during the day

Question 28

What is the seasonal phytoplankton succession?

Answer 28

• 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

Question 29

How is the diversity of phytoplankton affected by succession?

Answer 29

-Diversity of phytoplankton tends to increase as succession continues

Question 30

How is change in size in phytoplankton used as a defense against predators?

Answer 30

-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

Question 31

How are toxins/inhibitors in phytoplankton used as a defense against predators?

Answer 31

-cyanobacteria, dinoflagellates, haptophytes, diatoms, cann all produce noxious substances that can inhibit predation, and sometimes the growth of other phytoplankton

Question 32

How are warnings/distractions in phytoplankton used as a defense against predators?

Answer 32

-bioluminescence = the sparks in water! -distract predators

Question 33

How are behaviour changes in phytoplankton used as a defense against predators?

Answer 33

dinoflagellates in chains swim faster, and encounter predators more often - when copepods are present, chains break down and dinoflagellates swim more slowly

Question 34

What is the seasonal phytoplankton succession like in the arctic?

Answer 34

-don’t get the second bump, takes longer for sun to penetrate the ice etc. so the first bump starts later

Question 35

What is the seasonal phytoplankton succession like in the tropics?

Answer 35

-less seasonality with light availability = still peak of algae and peak of herbivores

Question 36

How does upwelling affect geographic distribution of primary productivity?

Answer 36

-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

Question 37

How do coastal nutrient sources affect geographic distribution of primary productivity?

Answer 37

-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

Question 38

How do ocean fronts/convergences affect geographic distribution of primary productivity?

Answer 38

-masses of water run into other masses of water (currents)= have mixing and can bring nutrients brought up back to the top

Question 39

What is the nutrient situation in ocean centres and gyres?

Answer 39

-nutrient poor