final Flashcards
Describe the NPP and NEP for diff environment
terrestrial : medium NPP, + NEP
wetlands: high NPP, +or - NEP
aquatic: low NPP, - NEP
Wetland biogeochem functions
sink, source, transformers
oxidation reaction order
only nice microbes find some cold meth
limitations of redox potentials
- most redox couples not in equilibrium
- systems continuously cycle electrons
- redox potential is closely related to pH
- electrode surfaces can be contaminated
describe organic matter accumulation
detrital plant biomass, detritus, peat
methanogenesis in wetlands
- co2 reduced to CH4 during oxidation
-ch4 released from plant leaves
why is sulfur redox cycling significant
it accounts for half or more of the total organic carbon mineralization in many environments
physical properties of water
- max density at 4 C
- ice and warmer water is less dense
-when dense water is on top, there is overturn
-less dense on top there is stratification
describe lake structure
- epilimnion
-metalimnion (thermocline)
-hypolimnion
describe the epilimnion
warm surface waters, light energy rapidly attenuates with depth
Metalimnion
zone of rapid temperature change
hypolimnion
cooler, deep waters
primary production and nutrient cycling during summer
there are phytoplankton, which contribute most NPP confined to surface waters
-NPP depends on external nutrients
-epilimnion is oxic so OM decomposes quickly
fate of primary production ( photsynthetic POM)
dead particulate organic matter (POM) sinks into the hypolimnion where it is decomposed by microbial respiration
-decay in the hypo consumes O2 –> low redox potential
-o2 is consumed and nutrients build up
export of POM from the epilimnion
- export ratio = percentage of PP that sinks to the hypo
- export ratio is 10-50% of NPP in 12 US lakes
lake productivity is linked to nutrient concentration
- most lakes are P limited
-other factors may be important
-studies suggest co limitation
P v N limitation
- natural P input to lakes is small (retention in watersheds w veg and soil; P associated with soil minerals not available)
- large amount of P is in plankton biomass- not much available
-P recycling in the epilimnion is dominated by bacterial decomp of om
allochthonous
introduced from a different area
autochthonous
from that spot
vegetation impacts soil holding capacity
-reduces runoff
-reduces average soil moisture content
-when removed, run off and soil water content rises
soil porosity and texture affect runoff
- soil properties (porosity and texture) affect infiltration rates and soil water content
-sands > 2mm have higher porosity than class < 0.002
field capacity
water holding ability ; water content a soil can hold against the force of gravity
- is a function of porosity, water retention and presence of impermeable layers
groundwater height =
stream height
Estuaries
fresh (river) water to saline (ocean) water and tidal influence
factors that determine processes on shelves
-presence or absence of large rivers
-presence or absence of upwelling
-location of ocean boundaries
-shelf width
drowned river valleys or coastal plain estuaries
most common
- formed by sea level rise during holocene
-tide and river dominated
coastal plain, bar built estuaries
-longshore currents form a sand bar or sand spit across an embayment
-lack a major river source
-usually shallow and wind dominated
Fjord type estuaries
deep, built by glaciers, shallow sill, sill might trap anoxic bottom water
tectonically produced estuaries
-formed by earthquakes and block faulting
-common on active coasts
-creates basins that become filled with water
estuary circulation
net flow is out at the surface and in along the bottom - two layered circulation
Type A = salt wedge estuary
- highly stratified, river discharge dominated over tidal action
-salt exchange by vertical advection across the halocline
-mississippi
Type B- Partially mixed estuary
- part mix, moderate stratification
- tidal flow increases relative to river discharge
-vertical advection and turbulence mix the system
-Chesapeake bay
Type C- well-mixed estuary
-vertically homogenous and well-mixed
-intense tidal flow and strong turbulent mixing
-lateral heterogeneity sometimes cause by strong winds
-Delaware bay
Type D- Fjord
sill results in stagnant bottom waters, usually highly stratified
name the mixing proceses
- advection- water mass intact but transported
- diffusion- random scattering of water particles bc of random motions
- dispersive mixing- scattering of water particles bc of tidal sloshing
river and sea water ion ratios
- Na/K - reflects lower affinity of marine ricks for sodium as compared to K, ocean = less effective sink for Na
- Ca/Mg- reflects preferential removal of calcium in the ocean as biogenic calcite ( ocean more effective sink for ca)
mixing curve for salinity
- in conc v salinity is linear : conservative
- if non linear: non conservative
mid estuary turbidity maxima
Zones of elevated suspended particulate matter (SPM) concentration at the interface between the river and the sea.
flocculation
process where solids form larger clusters, or flocs, to be removed from water.
