Deep Ecosystems

Question 1

Oceans Biological Carbon Pump Diagram

Answer 1

Refer to notes to draw out all 5 steps

Question 2

why is biological pump important

Answer 2

Sink atmospheric carbon
Important for connecting nutrient cycles and productivity
Bring food source to deep ocean

Question 3

Would atmospheric CO2 concentrations be different if the biological carbon pump didn’t exist

Answer 3

Yes there would be more CO2

Question 4

How does the biological carbon pump effect climate

Answer 4

It reduces atmospheric CO2, less heating and more cooling of earth

Question 5

How might climate change effect the biological carbon pump

Answer 5

OA: this may affect remineralization
Temperature: warmer water holds less gas, less ice and more stratified waters

Question 6

Explain the thermohaline circulation that drives the worlds oceans

Answer 6

This is driven by density

Begins in the warm shallow waters of the Pacific to Indian to Atlantic

Cools in the North Atlantic sinks and flows south to join the deep cold waters of Antarctica

Flows back to Indian and Pacific ocean and warms and rises

Very slow, around 1000 years from N Pacific to N Atlantic (2000 year-round trip)

Question 7

Where on the figure of NADW is oxygen highest and lowest?

Answer 7

Highest near the surface
Lowest at moderate depths with long time since surface and deep basins

Question 8

What processes explain oxygen trends with depth and latitude?

Answer 8

Time, respiration and ventilation (gas exchange with surface)

Question 9

What controls respiration rate?

Answer 9

Particle sinking rates (density)
Organic matter degradation rate (mineral protection)
Amount of O2

Highest between 100-300m

Question 10

Respiration, Renewal and Oxygen concentration at depths comparisons

Answer 10

Shallow (100-300m):
Respiration - highest
Renewal - Fastest
Oxygen - High

Mid-Depth:
Respiration - Not too low
Renewal - Slow
Oxygen - Low

Shallow (>3000m):
Respiration - lowest
Renewal - slowest
Oxygen - medium

Question 11

Highest and lowest nutrient concentrations on the NADW

Answer 11

Lowest at surface of north
Increase with depth and as you head south

Question 12

What processes explain the nutrient concentration trends

Answer 12

Time, Remineralization and productivity

Question 13

What are calcareous sediments made from and what makes them

Answer 13

calcium carbonate
Coccolithophores, zooplankton (foraminifera) and pteropods

Question 14

How is solubility of calcareous skeletons affected with depth

Answer 14

rate of dissolution increases with depth

Higher pressure
Lower temperature
Higher CO2 (acidic)

Begins dissolving at ~500m in Pacific and 1500m in Atlantic

Question 15

Lysocline

Answer 15

depth at which transition to carbonate undersaturated begins

Question 16

Carbonate compensation depth (CCD)

Answer 16

all calcium carbonate dissolved

Question 17

Where do you find calcareous sediment

Answer 17

Usually on elevated sea floor: flanks of mid-ocean ridges and seamounts

Patchy preservation: Carbonate can be buried before it is able to dissolve

Question 18

Siliceous sediment

Answer 18

silica skeletons
Diatoms & Radiolarians

Does not dissolve as readily, but the ocean is still undersaturated
Organic layers preserve the skeleton

Deposits on sea floor mirror surface production of organisms

Question 19

Inputs to the deep-sea

Answer 19

Phytoplankton: most consumed or lost to degradation

Zooplankton: most consumed or degraded before sea floor

Large animals: sink rapidly, some consumed at intermediate depths, available to benthic scavengers

Fish dumping: large portion of catch, increase benthic food supply

Faecal matter: sink rapidly to reach sea floor, mostly indigestible material, colonized by bacteria

Crustacean moults: low nutritional value, more benthic input, bacteria colonize

Macrophyte detritus: feed detritivores and bacteria

Vertical Migrations: downward transfer of organic material