하구및 연안생태Coastal management 2015 년 가을학기

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:

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

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

Beggiatoa

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

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.

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

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

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.

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

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

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

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

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

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

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

O2 Calm seas decrease oxygen exchange at the surface.

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

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

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

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.

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

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.

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.

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

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

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.

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 !

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

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

Nutrient forms and distributions High in river head