AICE Marine Unit 4 - Nutrient Cycles in Marine Ecosystems Part I Fill-In Notes
I.
Detritus
What is it? _______________________________________________________________
How does it fit in to a food web/chain?
________________________________________________________________________
 Who/what consumes it?
___________________________________________________________________________
________________________________________________________________________
 Detritus is broken down and released as chemical elements into the ____________,
_________, & _________ where P.P. can recycle them into organic compounds
 Without detritivores, life would cease! Essential nutrients would be _______________ &
___________________ to the ecosystem
II.
Chemical Cycling
 Nutrients move between ____________ and ________________ parts of the ecosystem in
______________________________ cycles.
 Cycles may be _____________ or _____________. Nutrient cycles with a gaseous
component (_____________, ________________, and ________________________) are
global whereas phosphorus, potassium and calcium cycle more locally (at least on short time
scales).
- 2 Major Types of Biogeochemical Cycles:
**Based on the Primary Source of nutrient input**
o Gaseous cycles—____________________ & _________________ (global circulation
patterns)
o Sedimentary cycles—___________________________________________; these vary
from one element to another, but essentially each has two abiotic phases:
 ______________ phase
 _____________ phase
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Draw me!
III.
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IV.
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V.
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VI.
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VII.
General Structure of Nutrient Cycles
Nutrients can move from __________________________________ by a variety of processes
Some examples:
a. Photosynthesis (_________________________________________________)
b. Respiration (makes inorganic nutrients available from organic)
c. ___________________________ (makes inorganic nutrients available from organic)
d. ____________________ (makes inorganic nutrients available from organic)
Decomposition and nutrient cycling rates
Rate of nutrient cycling is affected by _________________________________
In the tropics, _________________________________________ cause organic material to
decompose __________________________ than it does in temperate regions!
In aquatic ecosystems decomposition in ____________________ sediments can be very
slow (50 + years)
As a result, sediments are often a __________________ and only when there is upwelling*
are _______________________________________________.
(*Upwelling
___________________________________________________________________________
________________________________________________________________________)
Human effects on nutrient cycles:
Recent studies suggest that human activities
(________________________________________________) have approximately doubled
the supply of __________________ available to plants.
Fertilizers that are applied in amounts greater than plants can use or that are applied when
plants are not in the fields leach into groundwater or run off into streams and rivers
therefore getting to the ocean.
A major problem with intensive farming is _______________________________.
The ________________________________________ causes blooms of algae and
cyanobacteria as well as explosive growth of water weeds.
Because respiration by plants depletes the oxygen levels at night this process of
_____________________________ can cause fish kills.
Eutrophication of Lake Erie, for example, wiped out commercially important populations of
fish including lake trout, blue pike and whitefish in the 1960’s.
Limits on primary productivity
____________________________________________________ affecting NPP in aquatic
biomes.
In marine environments the nutrients limiting primary productivity are usually
________________ and __________________________, which are scarce in the photic
zone.
5 Nutrient Cycles
1. ________________________________
2. _______________________________
3. ______________________________
4. _______________________________
5. ______________________________
VIII.
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Carbon Cycle
Carbon forms _________________________________________ (organic chemistry is the
study of carbon chemistry). ________________________________________ etc. all contain
carbon.
Photosynthetic organisms take in _______________________________ and using energy
from sunlight join carbon atoms ________________________ (energy is stored in the
chemical bonds).
Major reservoirs of carbon include:
___________________________________________________________________________
___________________________________________________________________________.
Photosynthesis removes ______________________________________
An approximately equal amount of CO2 is returned to atmosphere by cellular respiration.
_______________________________________ adds large amounts CO2 to the atmosphere.
IX.
Nitrogen Cycling
o N is an essential element in
o Protein: ____________________________________________
o Nucleic acids: nitrogenous bases
o N2 makes up about _________________________________________
o N2 is only usable by prokaryotes with the enzyme nitrogenase
o Cyanobacteria like Anabaena carry their nitrogenase in a low oxygen package, the
heterocyst.
- Fixation
- Converts N2 to
o ________________________________ NH4 :
o N2 --> 2N
o 2N + 3H2 --> 2NH3
o Rhizosphere bacteria: mutualistic, some nodule formers
o Free-living bacteria (+cyanobacteria) ~ 12,000 species
o Nitrate (high energy discharge, like lightning) - NO3
o NO3 in atmosphere + water vapor = H2NO3
o Atmospheric fixation low: 8.9 kg N/ha/yr
- Mineralization (ammonification)
o Major step in ______________
o Biomolecules (proteins, nucleic acids) from
___________________________________________________________ and fungi to
amino acids then to CO2 + H2O + NH4 + energy
o Fate: dissolved in H2O, trapped in soil, fixed in clay
X.
Nitrification
- Nitrosomonas bacteria use __________________________ as sole E source
- Nitrobacter bacteria use the remaining E in nitrite ion and oxidize it to nitrate
- _________________________________ if nitrates build up in aquatic ecosystems
- Denitrification
• Nitrates reduced _______________________________________
• Denitrifiers are _______________________________
– Bacteria: Pseudomonas
– Fungi
Phosphorus Cycle:
Terrestrial & Aquatic
Nitrogen Cycle