18. Marine Biogeochemical Cycles 1 Flashcards
T/F
All life on earth shares the same underlying mechanisms of capturing and storing energy, manufacturing proteins, & transmitting info b/w generation
true
- all life on earth is the same, just ‘packaged’ in different ways!
Pelagic environment vs benthic enviro
pelagic= open ocean: drifters/ swimmers live
benthic= sea bottom enviro: marine algae/ animals do not float/ spend their lives here
Hydrothermal vent communities were discovered in ____ and are associated with __ vents
1977
hot
What lives at hot vents? How do they produce food?
Archaea
Using heat and chemicals: NOT photosynthesis
_____ and ______ are the groups of organisms that inhabit the water column. ____ are the bottom dwellers
Plankton (drifters) and Nekton (swimmers)
Benthos
Light energy from the sun is trapped by ____ in primary producers and changed into chemical energy
chlorophyll
T/F
Photosynthesis is reversible
true
“remineralization” –> heat energy is released
What are the 3 zones of water based on light availability?
Euphotic zone
Dysphotic zone
Aphotic zone
____ is the single most important factor determining distribution of animals in the oceans
light
Euphotic zone=
Zone where there is sufficient light penetration to support photosynthesis
Sfc to ~100 (whatever depth all wavelengths of light penetrate to)
Dysphotic zone=
Zone that has small but measurable quantities of light
Extends from euphotic zone to the depth where light can no longer penetrate
Aphotic zone=
area of the water column with no light penetration
~1000m
no photosynthesis here
_____ wavelengths penetrate deepest into the water column.
Which wavelengths are absorbed first?
Blue= deepest
Longer wavelengths (red/ orange) are absorbed first (don’t penetrate very deep)
Chlorophyll is a green pigment. Which wavelengths does it absorb best? Explain how this affects the distribution of phytoplankton
Give the exception
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
Primary productivity is highest where? Why?
near the top of the euphotic zone b/c most light available for photosynthesis (inc red light)
Where does the max photosynthetic rate occur?
below the surface –> too much UV above, too little light below
Compensation depth=
What does this usually correspond to?
Is this fixed?
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
Describe the oxygen and nutrient content at the surface
oxygen abundant due to mixing & photosynthesis
Nutrient content low b/c it’s being consumed by algae
At deeper depths, oxygen decreases as it’s consumed by heterotrophic organisms, producing a(n) ____ ____ _____. What are the nutrient levels at this depth?
Oxygen minimum layer (OML)
Nutrient level= maximum at this depth
The primary producers in the ocean are:
vs land
microscopic phytoplankton in ocean, macroscopic plants like grasses on land
Plankton=
All organisms (algae, animals, bacteria) that drift with ocean currents
planktos= wandering
T/F
Most of earth’s biomass consists of plankton adrift in the ocean
true!
Though 98% of marine species are bottom dwelling, the majority of the ocean’s biomass is ______
plankton
Can plankton determine their horizontal position in the water column? What about vertical?
Horizontal: No, can’t work against the currents
Vertical: Do have some vertical migratory ability
__-__% of the ocean’s biomass relies on photosynthesis for food (indirectly or directly)
95-98%
Ocean primary productivity=
What’s this measured in?
the incorporation of carbon atoms into carbohydrates by photosynthesis
g of C bound into carbohydrates per square m of the ocean
C/m2/yr
How can you measure marine primary productivity directly?
capture plankton in plankton nets
How can you measure marine primary productivity experimentally?
measure radioactive carbon in seawater
How can you measure marine primary productivity remotely?
monitor ocean color with satellites
- photosynthetic phytoplankton use green pigment chlorophyll
Nutrients cycle from producer to consumer & back much more quickly in _____ (marine/ terrestrial) ecosystems
marine
Total producer biomass in the ocean is:
vs
Living biomass on land is:
1-2billion metric tons
600-1000 billion metric tons
Compare global net productivity in marine ecosystems vs global terrestrial productivity
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
How are plankton typically classified?
by size
picoplankton to megaplankton
Give the 4 major groups of marine phytoplankton
Diatoms
Coccolithophores
Dinoflagellates
Picoplankton
diatoms=
dominant & most productive algae; test (shells) made of silica & these tests accumulate on the seafloor
Coccolithophores=
small single-celled autotrophs with plates of calcium carbonate; contribute significantly to calcareous seafloor deposits
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 ________ _________ ________
algae blooms (HABs) –> red tide
- mostly mixotrophic (can be autotrophic & heterotrophic: make own food & consume food)
- toxins
Paralytic shellfish poisoning (PSP)
What is picoplankton?
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)
What is Prochlorococcus?
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
Describe the classic N-P-Z marine food web
= most basic model of a pelagic ecosystem, examining the relationship b/w quantities of Nutrients, Phytoplankton, and Zooplankton
(NPZ)
Microbial loop=
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
Small heterotrophic bacteria consume ___ ____ ____ that are released into the ocean by plankton
soluble organic materials
99% of the mass of living things is built from which 4 elements?
Carbon
Oxygen
Hydrogen
Nitrogen
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?
carbohydrates, fats, proteins, nucleic acids (DNA)
________ are present in living organisms in very small quantities but are necessary for life
micronutrients
______, not diversity is the central message of biology
unity
detritus=
dead remains and waste products
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
ocean
(or earth)
What do the nature of biogeochemical cycles dictate? (3)
- what will live where
- which organisms will be successful
- ultimately what the composition of the ocean & atmosphere itself will be
The ______ cycle is the earth’s largest cycle
carbon
____ is the basic building block of life on earth
carbon
How does carbon enter the atmosphere?
as CO2
- by the respiration of living organisms, volcanic eruptions, the burning of fossils fuels etc
How is CO2 fixed into organic molecules?
photosynthesis captures sunlight and use this energy to fix CO2 into organic molecules –> food or structural components
When an animal eats a plant, what are 3 ‘pathways’ it can take?
- it can be incorporated into the animal’s body for growth
~45% - It can be respired by the animal (taken apart to harvest energy)
~45%
- ultimately to atmosphere - It can be wasted (excreted) back into seawater as dissolved organic carbon
~10%
Eventually, organisms (& their shells) sink below the mixed layer in the ocean and fall to the seafloor. What happens to the C?
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
POC=
particulate organic carbon
- Carbon in particulate organic material
- litter of plant/ herbivore origin
- detritus
DOC=
dissolves organic carbon
- C in organic compounds (acids, sugars, etc)
- serve as primary food source
DIC=
dissolved inorganic carbon
- serves as a primary course for photosynthesis and controlling the pH
Dissolved carbon can pass through a small pore sized ____
filter
Biological pump=
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
Do marine organisms often suffer from deficient C? Why or why not?
No
- B/c of large amounts of CO2 available in the ocean & b/c atmospheric CO2 readily dissolves in seawater
Deficiencies to marine life are typically in which cycles? (3)
nitrogen
phosphorus
iron
Respiration _______ oxygen and photosynthesis ______ oxygen
(produces/ consumes)
resp= consumes
photosyn= produces
T/F
Surface [O2] is close to equilibrium with the atmosphere
true
How does [O2] change with depth? Why?
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
Why does the deep ocean have higher [O2]?
Because rates of O2 consumption are low & there is a supply of cold, O2-rich waters from polar regions
Eutrophication=
causes/ effects?
artificial enrichment of waters by a previously scarce nutrient
causes: sewage, fertilizer, animal waste
- can cause algal blooms –> extensive hypoxia causing “dead zones”
T/F
Dead zones caused by eutrophication are associated with mouths of major rivers and spring runoffs
true
Can most higher order marine organisms tolerate dead zones caused by eutrophication?
Impact on bottom dwellers?
No
suffocates bottom dwellers
Describe 2 dead zones that currently exist
- Gulf of Mexico dead zone: 2nd largest
- runoff of nutrients, esp nitrates= algal blooms - North East Subarctic Pacific Ocean
- off coast of Van island
- expansion over last 5 decades
