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EAS 212: The Oceans > 18. Marine Biogeochemical Cycles 1 > Flashcards

18. Marine Biogeochemical Cycles 1 Flashcards

1
Q

T/F

All life on earth shares the same underlying mechanisms of capturing and storing energy, manufacturing proteins, & transmitting info b/w generation

A

true
- all life on earth is the same, just ‘packaged’ in different ways!

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2
Q

Pelagic environment vs benthic enviro

A

pelagic= open ocean: drifters/ swimmers live

benthic= sea bottom enviro: marine algae/ animals do not float/ spend their lives here

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3
Q

Hydrothermal vent communities were discovered in ____ and are associated with __ vents

A

1977
hot

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4
Q

What lives at hot vents? How do they produce food?

A

Archaea
Using heat and chemicals: NOT photosynthesis

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5
Q

_____ and ______ are the groups of organisms that inhabit the water column. ____ are the bottom dwellers

A

Plankton (drifters) and Nekton (swimmers)

Benthos

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6
Q

Light energy from the sun is trapped by ____ in primary producers and changed into chemical energy

A

chlorophyll

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7
Q

T/F

Photosynthesis is reversible

A

true
“remineralization” –> heat energy is released

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8
Q

What are the 3 zones of water based on light availability?

A

Euphotic zone
Dysphotic zone
Aphotic zone

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9
Q

____ is the single most important factor determining distribution of animals in the oceans

A

light

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10
Q

Euphotic zone=

A

Zone where there is sufficient light penetration to support photosynthesis
Sfc to ~100 (whatever depth all wavelengths of light penetrate to)

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11
Q

Dysphotic zone=

A

Zone that has small but measurable quantities of light
Extends from euphotic zone to the depth where light can no longer penetrate

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12
Q

Aphotic zone=

A

area of the water column with no light penetration
~1000m
no photosynthesis here

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13
Q

_____ wavelengths penetrate deepest into the water column.

Which wavelengths are absorbed first?

A

Blue= deepest

Longer wavelengths (red/ orange) are absorbed first (don’t penetrate very deep)

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14
Q

Chlorophyll is a green pigment. Which wavelengths does it absorb best? Explain how this affects the distribution of phytoplankton

Give the exception

A

Red and violet

Since very little red light penetrates past 3m, most phytoplankton stay near the sfc to absorb red light

Exception= cyanobacteria which can use blue light

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15
Q

Primary productivity is highest where? Why?

A

near the top of the euphotic zone b/c most light available for photosynthesis (inc red light)

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16
Q

Where does the max photosynthetic rate occur?

A

below the surface –> too much UV above, too little light below

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17
Q

Compensation depth=

What does this usually correspond to?
Is this fixed?

A

Depth where photosynthetic rate= respiration rate
So, net photosynthesis is zero

Usually corresponds to depth where 1% of sfc light penetrates (bottom of the euphotic zone)

Not fixed; will vary b/w locations and at diff times of day

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18
Q

Describe the oxygen and nutrient content at the surface

A

oxygen abundant due to mixing & photosynthesis

Nutrient content low b/c it’s being consumed by algae

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19
Q

At deeper depths, oxygen decreases as it’s consumed by heterotrophic organisms, producing a(n) ____ ____ _____. What are the nutrient levels at this depth?

A

Oxygen minimum layer (OML)

Nutrient level= maximum at this depth

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20
Q

The primary producers in the ocean are:

vs land

A

microscopic phytoplankton in ocean, macroscopic plants like grasses on land

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21
Q

Plankton=

A

All organisms (algae, animals, bacteria) that drift with ocean currents

planktos= wandering

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22
Q

T/F
Most of earth’s biomass consists of plankton adrift in the ocean

A

true!

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23
Q

Though 98% of marine species are bottom dwelling, the majority of the ocean’s biomass is ______

A

plankton

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24
Q

Can plankton determine their horizontal position in the water column? What about vertical?

A

Horizontal: No, can’t work against the currents
Vertical: Do have some vertical migratory ability

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25
Q

__-__% of the ocean’s biomass relies on photosynthesis for food (indirectly or directly)

A

95-98%

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26
Q

Ocean primary productivity=

What’s this measured in?

A

the incorporation of carbon atoms into carbohydrates by photosynthesis

g of C bound into carbohydrates per square m of the ocean

C/m2/yr

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27
Q

How can you measure marine primary productivity directly?

A

capture plankton in plankton nets

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28
Q

How can you measure marine primary productivity experimentally?

A

measure radioactive carbon in seawater

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29
Q

How can you measure marine primary productivity remotely?

A

monitor ocean color with satellites
- photosynthetic phytoplankton use green pigment chlorophyll

30
Q

Nutrients cycle from producer to consumer & back much more quickly in _____ (marine/ terrestrial) ecosystems

A

marine

31
Q

Total producer biomass in the ocean is:
vs
Living biomass on land is:

A

1-2billion metric tons
600-1000 billion metric tons

32
Q

Compare global net productivity in marine ecosystems vs global terrestrial productivity

A

global net productivity in marine ecosystems= 35-50 billion metric tons of C bound into carbohydrates (per yr)

global terrestrial productivity is similar: 60-70 billion metric tons

33
Q

How are plankton typically classified?

A

by size

picoplankton to megaplankton

34
Q

Give the 4 major groups of marine phytoplankton

A

Diatoms
Coccolithophores
Dinoflagellates
Picoplankton

35
Q

diatoms=

A

dominant & most productive algae; test (shells) made of silica & these tests accumulate on the seafloor

36
Q

Coccolithophores=

A

small single-celled autotrophs with plates of calcium carbonate; contribute significantly to calcareous seafloor deposits

37
Q

Dinoflagellates are marine phytoplankton that produce harmful _____ _____

  • How do they make food?
  • They can produce ____ which are consumed by fish, and then by humans. Humans who eat this may get ________ _________ ________
A

algae blooms (HABs) –> red tide

  • mostly mixotrophic (can be autotrophic & heterotrophic: make own food & consume food)
  • toxins
    Paralytic shellfish poisoning (PSP)
38
Q

What is picoplankton?

A

very small (0.2-2micrometers) plankton; extremely abundant & productive

May account for 80% of photosynthetic activity in some parts of the open ocean (esp in low nutrient areas)

39
Q

What is Prochlorococcus?

A

Probably the most abundant photosynthetic organism on earth! It’s a picoplankton
–> have a chlorophyll variant that allows it to absorb blue light at low light intensities

40
Q

Describe the classic N-P-Z marine food web

A

= most basic model of a pelagic ecosystem, examining the relationship b/w quantities of Nutrients, Phytoplankton, and Zooplankton
(NPZ)

41
Q

Microbial loop=

A

pathway by which dissolved organic C is returned to higher trophic levels via incorporation into bacterial biomass and then coupled with the classic phytoplankton-zooplankton- nekton food chain

42
Q

Small heterotrophic bacteria consume ___ ____ ____ that are released into the ocean by plankton

A

soluble organic materials

43
Q

99% of the mass of living things is built from which 4 elements?

A

Carbon
Oxygen
Hydrogen
Nitrogen

44
Q

Macronutrients compose nearly all of the other 1% of the mass of living things (after the 4 major elements).
Atoms of macronutrients combine to make what?

A

carbohydrates, fats, proteins, nucleic acids (DNA)

45
Q

________ are present in living organisms in very small quantities but are necessary for life

A

micronutrients

46
Q

______, not diversity is the central message of biology

A

unity

47
Q

detritus=

A

dead remains and waste products

48
Q

Elements/ small molecules forming the tissues of an organism may cycle rapidly in/ out of living things or they may be stored in the deep _____ for great spans of time

A

ocean
(or earth)

49
Q

What do the nature of biogeochemical cycles dictate? (3)

A
  • what will live where
  • which organisms will be successful
  • ultimately what the composition of the ocean & atmosphere itself will be
50
Q

The ______ cycle is the earth’s largest cycle

A

carbon

51
Q

____ is the basic building block of life on earth

A

carbon

52
Q

How does carbon enter the atmosphere?

A

as CO2
- by the respiration of living organisms, volcanic eruptions, the burning of fossils fuels etc

53
Q

How is CO2 fixed into organic molecules?

A

photosynthesis captures sunlight and use this energy to fix CO2 into organic molecules –> food or structural components

54
Q

When an animal eats a plant, what are 3 ‘pathways’ it can take?

A
  1. it can be incorporated into the animal’s body for growth
    ~45%
  2. It can be respired by the animal (taken apart to harvest energy)
    ~45%
    - ultimately to atmosphere
  3. It can be wasted (excreted) back into seawater as dissolved organic carbon
    ~10%
55
Q

Eventually, organisms (& their shells) sink below the mixed layer in the ocean and fall to the seafloor. What happens to the C?

A

Most of the C in CaCO3 (shells etc) is turned into CO2 by heterotrophic bacteria before it hits the bottom.
- a small amount ~1% reaches the sediments where it’s buried

  • eventually the buried C can be weathered etc and returned to upper ocean
56
Q

POC=

A

particulate organic carbon

  • Carbon in particulate organic material
  • litter of plant/ herbivore origin
  • detritus
57
Q

DOC=

A

dissolves organic carbon
- C in organic compounds (acids, sugars, etc)
- serve as primary food source

58
Q

DIC=

A

dissolved inorganic carbon
- serves as a primary course for photosynthesis and controlling the pH

59
Q

Dissolved carbon can pass through a small pore sized ____

A

filter

60
Q

Biological pump=

A

the way in which material is removed from the euphotic zone to the seafloor

  • ‘pumps’ CO2 and other nutrients from the upper ocean & concentrates them in the deep ocean/ seafloor sediments
61
Q

Do marine organisms often suffer from deficient C? Why or why not?

A

No
- B/c of large amounts of CO2 available in the ocean & b/c atmospheric CO2 readily dissolves in seawater

62
Q

Deficiencies to marine life are typically in which cycles? (3)

A

nitrogen
phosphorus
iron

63
Q

Respiration _______ oxygen and photosynthesis ______ oxygen

(produces/ consumes)

A

resp= consumes
photosyn= produces

64
Q

T/F

Surface [O2] is close to equilibrium with the atmosphere

A

true

65
Q

How does [O2] change with depth? Why?

A

decreases with depth as oxygen is consumed in respiration (more respiration deeper as light is lost)

Below 1000m, [O2[ increases again because most organic matter is consumed above that level

66
Q

Why does the deep ocean have higher [O2]?

A

Because rates of O2 consumption are low & there is a supply of cold, O2-rich waters from polar regions

67
Q

Eutrophication=

causes/ effects?

A

artificial enrichment of waters by a previously scarce nutrient

causes: sewage, fertilizer, animal waste

  • can cause algal blooms –> extensive hypoxia causing “dead zones”
68
Q

T/F
Dead zones caused by eutrophication are associated with mouths of major rivers and spring runoffs

A

true

69
Q

Can most higher order marine organisms tolerate dead zones caused by eutrophication?

Impact on bottom dwellers?

A

No

suffocates bottom dwellers

70
Q

Describe 2 dead zones that currently exist

A
  1. Gulf of Mexico dead zone: 2nd largest
    - runoff of nutrients, esp nitrates= algal blooms
  2. North East Subarctic Pacific Ocean
    - off coast of Van island
    - expansion over last 5 decades
71
Q
A

EAS 212: The Oceans (18 decks)

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