1. 하구및 연안생태Coastal management
2015 년 가을학기

2. Measuring diagenesis From vertical profiles
Simple 1-dimensional diagenetic model
Sediment-water interface flux
Steady state assumptions
Underestimate actual rates
Causes of underestimation
Rapid remineralization at the surface; porewater profile was not reflected: steady state problem
Methane bubble: advection
bioturbation:

3. Anaerobic energy flux: sulfur cycle
Much of the energy is modulated through anaerobic microbial metabolism; sulfur cycle
Assimilatory; amino acid, methionine, cystine
Dissimilatory; disulfovibrio elemental sulfur
Chemoautotrophic, photoautotrophic
Pyrite formation and reoxidation
Sulfate reduction played major role in Eh on sediments

4. Anaerobic energy flux: sulfur cycle
About 50% of sediment oxygen demand is due to sulfide oxidation
Sulfide oxidation is almost balanced by sulfate reduction
Autotrophic sulfide oxidation: Beggiatoa; up to 4g dry wt/m2

6. Beggiatoa

7. Sulfate reduction and denitrification
Denitrification was relatively important in winter in Danish sediments; up to 20%
CH4 formation is less important; presence of SO4 inhibits Ch4 formation
However, when the OM load is high CH4 production can be substantial

8. Metabolic gases O2. CO2, N2, CH4, H2S, NH3, N2O
Abundant gases: N2, O2, Ar
Noble gases: Ar, Ne, He, Kr, Xe
N2:Ar ration: indicator of denitrification and nitrogen fixation
Solubility: Busen coeeficient: volume of the pure gas 1 atm pressure that can desolve in a unit volume of water at standard temperature and presure.

9. Metabolic gases Gas flux across air-sea interface
O2 flux is 2 times more than N2
Co2 flux is 70 time more than N2
Transfer coefficient:
Kd: AD/Dz
0.1~2.5 mg O2 m-2 h-1
Lower value: shallow salt pond
Higher value: windy conditions
Saturation depicts

10. The Carbon dioxide system
CO2 react with Water !!!
“Chemical composition of the ocean is the result of a great acid-base titration !!!”
Acid leaked from earth’s interior
Substance that can donate proton
Base released by weathering of rock
Substance that can accept proton
Carbonate system
Equilibrium constant

11. The carbonate system
Carbonic acid formation: Hydration-dehydration; carbonic anhydrase
Ionization
Dissociation
Controlled by pH
Dissociation constant; k1’, k2’ not k1, k2: calculated from concentration rather than the activity.

12. Calculating Carbon system
TCO2, CO2 can be measured.
All other should be calculated
Buffering reaction of sea water: resist to the pH change.
In sediments, however, high NH4+, HS- can exceeds buffering capacity
On geologic time scale, suspended clay mineral provide buffering actions

13. Alkalinity Alkalinity: degree to which water accept protons
[Bicarbonate, carbonate, borate OH- ] – [H+]
Borates can be ignored in normal pH
Carbonate alkalinity: bicarbonate + carbonate
Conservative: TCO2 >> CO2 and CO32- variation

14. CaCO3
Calcite
Aragonite
Shells of benthic animals; mollusks etc..

15. Biological efftecs on O2, CO2
CO2: air contain 2% of ocean
Water, rock, carbonate sediments, living, dead organisms is much more abundant
Green house gas: CO2 increase 0.3 % per year
Diel changes in pH and O2 can be used to indicate production and consumption
Photosynthesis: increase of O2 and pH

16. Biological efftecs on O2, CO2
AOU: apparent oxygen utilization
Long-term changes in oxygen versus conservative tracers of water masses such as salinity can be used to estimate consumptions.; does not apply to estuaries
Dispersion, vertical diffusuion, air-water transfer, production, respiration

17. O2 budget for Chesapeake Bay
Biological processes account for 43~69% of observed input
Anoxia formations

18. Warm Temperatures
Warm spring and summer temperatures heat
the water surface.

19. O2
Calm seas decrease oxygen
exchange at the surface.

20. Nutrients
Warm fresh water and nutrients are delivered by the Mississippi River and float on the denser saltwater.

21. A stratified layer is formed with lighter, fresher, warmer water at the surface and heavier, saltier, cooler water near the bottom limiting oxygen mixing throughout the water column.
Lighter
Fresher
Warmer
Water
Stratified Layer
No O2 mixing
Heavier
Saltier
Cooler
Water

22. At the surface, plankton blooms occur when excess nutrients are present

23. When plankton die, they sink and decompose
Dead plankton and fecal pellets sink to the bottom, which increases carbon accumulation in the sediments.
As nutrients are used up, phytoplankton are consumed by zooplankton causing an explosion in zooplankton populations as well.
As the dead plants and animals and their fecal pellets sink to the bottom, bacteria use the available oxygen in the water column to decompose organic matter.

24. When plankton die, they sink to the bottom and decompose.
During decomposition bacteria use up most or all of the available oxygen.
Dead Plankton
No O2
Decomposers

25. During decomposition, bacteria use up most or all of the oxygen causing the water column to become hypoxic or anoxic.
As decomposition increases in the water column and at the bottom, the oxygen is eventually used up causing hypoxic and anoxic conditions.

26. Mobile animals become stressed and leave
Stationary animals become stressed and/or die
With low DO a decrease in diversity of benthic fauna occurs.
A decrease in diversity indicates a degrading environment.
Eventually, without oxygen, the benthic population will become stressed and die.
If DO is < 2 mg/l mobile animals leave the area and stationary animals like clams and worms die because there is not enough oxygen to sustain them.
The water and the bottom will smell like rotten eggs under anoxic conditions because hydrogen sulfide is produced once oxygen is depleted.

27. When little or no oxygen is present:
Mobile animals leave.
Stationary animals become stressed or die.

28. Warm Temperatures O2 Dead Plankton Fresh River Water Nutrients
        
Nutrients O2
Plankton Bloom
Lighter, Fresher, Warmer, Water
Dead Plankton
Stratified Layer
No O2 Mixing
Heavier, Saltier, Cooler, Water
No O2
Decomposers

29. When oxygen is mixed throughout the water column during fronts, hurricanes and tropical storms, hypoxia is broken up.
Without mixing, the Gulf suffers:
— mortality of fish and their food base
— high losses of benthic (bottom dwellers) plants and animals
— reductions in the number of species
— disruption of fish spawning, recruitment and migration.

30. The autotrophic nutrients
Fertilizer !
C,N,P,Si,S,K,Mg,Na,Ca,Fe,Mn,Zn,Cu,B,Mo,Co,V, vitamins, thiamin, cyanocobalamin, biotin
Macro nutrients; N, P, Si
Constantly changing; river flow, ocean exchange
Organic  inorganic
Nutrient cycles can control energy flux in a ecosystem !!!; Nutrient cycle is fundamental to understanding of estuarien ecosystem
Mid 1960s : measurement of spatial and temporal concentration.
Last 20 years: development of isotope: rates !

31. Nutrient forms and distributions
Oxidation state
Solid-liquid-gas
Chemical structure
Nitrogen is most diverse; -3~+5
Organic: highly reduced
P: PO43- :+5; ortho, papa, meta
Si: dissolved +4 (H4SiO2) detrital quartz, aluminosilicate clays, dissolved silicon

32. Nutrient forms and distributions
Seasonal variations
Mid summer PO4 peak: temperature regulated regenerations and redox condition
NO3: winter maxima; external input via land run-off
NH4: high in sewage input sites; balance between phytoplankton uptake and benthic regneration

33. Nutrient forms and distributions
High in river head