L10 - Nutrients and biogeochemical cycles

Question 1

What are phytoplankton important in?

Answer 1

Carbon and other biogeochemical cycles in marine and atmospheric systems. Overall, the ocean is a carbon ‘sink’: it takes up more carbon from the atmosphere than it gives up.

Question 2

Summary of the carbon cycle?

Answer 2

There are many important volatile gasses released from the ocean to the atmosphere that impact cloud formation, albedo etc. Before the industrial revolution, the ocean was a source of CO2, now the oceans act as a carbon sink - equilibrium.

Question 3

What is plankton greek for?

Answer 3

Drifter

Question 4

What are biogeochemical cycles?

Answer 4

Cycles of nutrients or minerals that involve biology, geology and chemistry.

Question 5

Biogeochemical cycles - POC (and or TC) - DOC?

Answer 5

Particulate Organic Carbon (>0.2 microns is a particle, if less, its Dissolved Organic Carbon)

Question 6

Biogeochemical cycles - PON - DON?

Answer 6

Particulate (Dissolved) Organic Nitrogen

Question 7

Biogeochemical cycles - POP (DOP)?

Answer 7

Particulate (Dissolved) Organic Phosphorus

Question 8

Biogeochemical cycles - DIP (Pi Phosphate) DIP?

Answer 8

Dissolved In-organic Phosphorus

Question 9

Biogeochemical cycles - DCM?

Answer 9

Deep Chlorophyll Maxima

Question 10

Biogeochemical cycles - NPP and GPP?

Answer 10

Net and Gross Primary Production

Question 11

Biogeochemical cycles - u and umax (micro)?

Answer 11

Phytoplankton growth rate

Question 12

What are the major elements (as ions) in the oceans?

Answer 12

Top 6 major elements as ions in the sea (make 99% of dissolved salts). Cl-, Na+, Mg2+, SO42-, Ca2+, K+. Mainly conserved and present in ~constant proportions throughout oceans. But these are not limiting nutrients.

Question 13

What are MACRONUTRIENTS/ELEMENTS important for plankton?

Answer 13

C, H, O, N, P, S, Mg, K, Ca, Si. Those in bold are in low concentrations umol/kg and can be limiting nutrients to phytoplankton.

Question 14

What are MICRONUTRIENTS/ELEMENTS important for plankton?

Answer 14

Fe, Mn, Cu, Zn, Mo, Cd, V, Co

Question 15

What was Iron enrichment experiment?

Answer 15

Large areas of open ocean & equatorial South Pacific respond. Natural iron fertilisation events in the post glacial periods suggest up to 60 billion tons carbon drawn out of the atmosphere, dropping global temps. Lab experiments - 1 ton Fe -> 30 - 100k tons C out of atmosphere. Small-scale experiments - can draw some C out, less efficiently and less permanently (up to 1000 tons per Fe).

Question 16

What is the microbial food web?

Answer 16

A lot of phytoplankton biomass is predated by grazing: micro and mesozooplankton. Aggregates from senescent biomass and fecal pellets sinks. Some of this is decomposed (respired, releasing CO2) by bacteria, some sinks to ocean floor sequestering the carbon. However, misses viruses, volatile gases and the importance of different macro- and micro- nutrients in driving the microbial system to maintain life in the oceans. DMS - dimethyl sulfide. Volatile gas found in surface water produced by enzymatic lyses of DMSP dimethylsulfoniopropionate by microalgae, atmosphere it is primary component of cloud condensation nuclei.

Question 17

What are some aggregates?

Answer 17

Faecal pellets from zooplankton, senescent biomass, sink to the depths, marine snow, exports nutrients, depletes surface

Question 18

How much Carbon is in major reservoirs on earth?

Answer 18

Atmosphere 720 Gt, Oceans 38,400 Gt, Terrestrial biosphere (total) - mainly forests 2,000 Gt. Over the past 200 years, human activities have altered the global carbon cycle significantly. Approx. 30-4-% of the CO2 from human activity released into the atmosphere dissolves into oceans, rivers and lakes.

Question 19

What happens in the Ocean Carbon Cycle?

Answer 19

POC and DOC, of the anthropogenic CO2 released into the atmosphere some is taken up by the ocean. Some CO2 returns to the atmosphere, and some is exported to the deep ocean. In figure (page 13) CO2 is pumped in, sink into the sediment and deep ocean. A biological pump, in this we have microbial food we have cycling of particulate carbon, eaten by zooplankton and bacteria -> DPC and respired by bacteria into the atmosphere. Very large area of research, what constitutes these and how they are cycled is still an active area.

Question 20

What happens in the Biological Carbon Pump?

Answer 20

Calcification Inorganic carbon. Phyto capturing CO2, dissolves and reacts with water to produce glucose via photosynthesis. Nutrients come through run off from land or upwelling from the deep. When the nutrients, light and CO2 come together, you create phytoplankton biomass that feeds into the food webs in the oceans. Another component of carbon cycling - carbonate. Weathering of rock releases Ca, which then combines with carbonate to produce calcium carbonate. Some of these calcareous organisms then sink into the sediment. You would think this captures carbon, however due to bacterial respiration this isn’t necessarily so - different areas of the ocean may provide different results depending on local conditions.

Question 21

What is formanifera?

Answer 21

Scanning electron micrograph of the foramiferan Elphidium gunteri, 1931 ‘test’. Tests or shells are made of calcium carbonate. Sink to ocean floor and fossilise, incorporated into stone. Single-celled organisms.

Question 22

What is the difference between Formanifera and other seashells?

Answer 22

Formanifera, is a protozoan, the rest are animals. Same protective strategy/buoyancy control. Convergent evolution.

Question 23

How are classifications dynamic?

Answer 23

Today protista are not treated as a formal taxon but the term ‘protist’ is still commonly used for convenience. The most popular contemporary definition is a phylogenetic one, catch all where a protist is any eukaryote that is not an animals, (land) plant, or (true) fungus.

Question 24

What is the formaniferan structure?

Answer 24

Endoplasm, ectoplasm, chamber, pores, foramen, food vacuole, nucleus, mitochondria, granureticulose, pseudopodia, granules, primary aperature, food particle, golgi apparatus, ribosomes.

Question 25

What are coccolithophore algae?

Answer 25

Covered in calcite discs called coccoliths, protective, coccoliths sink to become part of the sediment.

Question 26

What do Coccolithophores produce?

Answer 26

DMSP, which contributes to cloud formation: site of nucleation of a raindrop. Dimethylsulfoniopropionate (DMSP) converted Dimethylsulfide (DMS) which is converted to sulphate in the atmosphere. Sulphate acts as a nucleating agent for water vapour to become water droplets. Clouds are formed which reflect light back away from the earth (albedo)

Question 27

How are phytoplankton central to the marine carbon cycle?

Answer 27

Carbon is the basic currency unit in ecology; it is transferred from inorganic to organic forms and back by biological processes. Photosynthesis 6CO2 + 6H20 -> C6H12O6 + 6O2 and respiration C6H1206 + 6O2 -> 6CO2 + 6H20 are major pathways to transform carbon. Calcification: some marine organisms combine calcium with bicarbonate ions to make calcareous shells or skeletons: Ca2+ + HCO3- = CaCO3 + H2O + CO2 = CaCO3 + HCO3- + H+. But calcification produces produces CO2. Oceanic blooms of coccolithophorids and production of coral reefs do not help decrease the recent atmospheric increase in CO2 in the short term.

Question 28

What is a summary about CO2?

Answer 28

Carbon in the form of CO2 is the driver of all production - it is used to build biomass. Affects preservation of CaCO3. CO2 traps inbound radiation that gets trapped in the atmosphere (greenhouse effect) which controls the climate. CO2 affects the acidity of the ocean. CO2 in water reacts with CaCO3 to form soluble calcium bicarbonate: this is the basis of erosion, partial pressure of CO2.

Question 29

What happens in the ocean nitrogen cycle?

Answer 29

In the atmosphere Nitrogen is present at 78% but it is very inert chemically, so is not bioavailable in this form. However, some algae, particularly some cyanobacteria species (e.g. Synechococcus) can fix N2 into ammonium that can then go through the cycle of nitrification where it is converted to Nitrate via Nitrite. Most Nitrification occurs in the lower portion of the euphotic zone in the water column. In the ocean, nitrate is the main nitrogenous compound. Ammonium and nitrate are both taken up by phytoplankton but ammonium is used preferentially to nitrate. Some of the major ocean cyanobacteria can only use ammonium (e.g. most Prochlorococcus). Because it is faster to convert to amino acids and proteins. In fact, Nitrate has to be converted to ammonium using the reducing power of photosynthesis, so it requires energy. When nitrate is reworked by consumers, it is decomposed to ammonium (faecal pellets) and recycled by bacteria into nitrogen and released back into atmosphere (denitrification)

Question 30

What happens in the nitrogen cycle in different ocean waters? page 25

Answer 30

Coastal shelf and upwelling, OMZ oxygen minimum zones, open ocean surface waters, deep ocean. A: DIN assimilaton by phytoplankton, nutrients coming in from rivers. B: ammonium regeneration: phytoplankton predation and C: nitrogen fixation by some of the cyanobacteria D: nitrate diffusion up from deepwater from E: microbial nitrification of ammonium to nitrate. F: microbial denitrification of nitrate to nitrogen. Generally, in anoxic conditions (depleted oxygen) but also in intertidal zones. Note PON burial in sediment.

Question 31

What happens in phosphorus?

Answer 31

Phosphate is the most important inorganic form (Pi) of phosphorus: PO43-. Phosphorus (as phosphate) forms part of the ATP, RNA, DNA and phospholipid molecules within the planktonic cells in the open ocean. Microalgae can store Pi as polyphosphate (polymers of Pi). DOP found to be increasingly important.

Question 32

What is the role of microbes and marine phosphorus cycle?

Answer 32

While Pi is generally regarded as the most bioavailable form of P, its concentration in the surface waters of the open ocean is much smaller than that of DOP. Yet, we know surprisingly little about the chemical composition or bioavailability of DOP. Many uncertainties about microbial P metabolism and P cycling remain, and studies on marine microbes and the P cycle will continue to be a critical area of future research.

Question 33

What are the 2 forms of particulate inorganic and organic phosphorus?

Answer 33

Abiotic and biotic particulate phosphorus

Question 34

What is abiotic particulate phosphorus?

Answer 34

Mineral absorbed phosphorus, mineral associated phosphorus

Question 35

What is biotic particulate phosphorus?

Answer 35

Orthophosphate pyrophosphate polyphosphate, inorganic phosphorus. Phosphomonoesters - phosphosugars, phospholipids, nucleoside monophosphate, phytic acids. Nucleosides di, tri-phosphate. Phosphodiesters - nucleic acids (DNA, RNA), phosphonates

Question 36

What is the Redfield ratio (redfield stoichiometry)?

Answer 36

Redfield, found that plankton build biomass with a stochiometric ratio of: 106C:16N:1P. We get a linear relationship plotting phosphate to nitrate- this was done by Alfred Redfield. Is important to understand uptake of nutrients. If this ratio is shifted, phytoplankton don't grow as well. They build biomass with this. Stochiometric (optimised for growth)

Question 37

What are the controls on primary production in the ocean?

Answer 37

More light at surface and here nutrients limit growth (N). N increases with depth. Euphotic zone receives enough light for photosynthesis to exceed respiration (net production). DCM Deep chlorophyll maximum, occurs where light and nutrients are both limiting. Algae responds to low light by increasing chlorophyll. Thermocline can prevent nutrients from mixing. Peak POC peaks above DCM, more light here.

Question 38

How is marine phytoplankton cycled?

Answer 38

Nutrient input comes from land (from soils and agriculture) and the deep ocean (upwelling), contributing to phytoplankton growth. This organic carbon is cycled through meso and micro zooplankton (predation), bacteril degradation and viral lysis.

Question 39

What are the abiotic factors influencing marine ecosystems?

Answer 39

Nutrients, light, temp, pH, salinity

Question 40

What are the biotic factors influencing marine ecosystems?

Answer 40

Grazers - zooplankton, bacteria, symbiosis, phytoplankton growth.

Question 41

How do we sample phytoplankton and other particles?

Answer 41

Most commonly use the CTD system - conductivity, temperature and depth. Set depths in water column. Has sets of water bottles that are triggered at certain depth to collect seawater. Moored traps pulled up after a certain amount of time.