Chemistry Lecture Slides

well mixed chemically homogeneous except hyporheic environment thermal stratification rare (occasionally large pools) generally aerobic environment favors oxidation suppresses anaerobic processes but locally important exceptions (hyporheic, pools, banks, floodplains) General conditions affecting River Chemistry River Ecosystems(3):river chemistry

Principal dissolved material in freshwater ecosystems

6 HOH + 6 CO 2 C 6 H 12 O O 2 stoichiometrically useful but too simplified Photosynthesis and macro-nutrients

a more realistic (but also very simplified) equation for the production of plant (algae) protoplasm: 106 CO NO xPO HOH + 18 H + ENERGY (C 106 H 263 O 110 N 16 P 1 ) O 2 note molar ratios of 106:16 ( ~12:1) C to N and 16:1 N to P correcting for molar weights Necessary Inputsatomic wt mg per mole algaewt relative to P CO 2 -C~121272~41 NO 3 - N~14224~7 PO 4 = -P~ Energy

How much is a lot?

10 ppb 50 ppb 100 What is average?

Examples of some chemically distinct waters

…three ways to look at dissolved materials: load or loading [mg/sec or g/day or kg/yr] can standardize loading by area: yield [e.g. mg/sec/sq mile or g/day/acre or kg/yr/km2] concentration [mg/liter] River Ecosystems(3):river chemistry

dominated by input and output retention decreases with increasing velocity and decreasing biological activity longitudinally, incremental uptake/deposition leads to an assimilative capacity for consumable inputs by a combination of assimilation and dilution abnormally high inputs can be processed longitudinally nutrient cycling becomes nutrient spiraling mass balance in a channel segment River Ecosystems(3):river chemistry Spiraling length S b S w

dissolved material load constituents reflect hydrologic source and history of material contacts concentrations highly variable across landscape (spatial) as well as over time Concentration Mass/Volume Mass flux (load)/ water flux (Q) [C] = L / Q [C] = a Q b-1 River Ecosystems(3):river chemistry VdC/dt = QC in – QC out +/- VrC Mass balance For a Completely Mixed Flow reactor

material transport in rivers: load flow  transport three categories of material [load] dissolved (chemistry) suspended bed L = a Q b Where a and b are constants b=1 b >1 b< 1 b<< 1 Q L All forms of load are highly variable over time (flow effects) Point Source (PS) and non-Point Source (NPS) loading PS loads relatively constant (b<<1, concentration strongly subject to dilution) NPS loads usually increases with increasing runoff: note options

Q Load (quantity/time) Typical non-point source Typical point source hysteresis

Q Concentration (quantity/vol) Typical non-point source Typical point source

Nitrate+Nitrite (ppm) Sol. Reactive Phosphate (ppm)

Primary productivity of Aquatic ecosystems A basic model for enzyme mediated reaction rates. Common used to describe the relationship between concentrations of a limiting input and the resulting rate of photosynthesis. growth or uptake rate = (S * Max) / (S+K) S=input concentration; Max= maximum rate; K=1/2 saturation constant Monod’s model

Primary productivity of Aquatic ecosystems A basic model for enzyme mediated reaction rates. Common used to describe the relationship between concentrations of a limiting input and the resulting rate of photosynthesis. growth or uptake rate = (S * Max) / (S+K) S=input concentration; Max= maximum rate; K=1/2 saturation constant Monod’s model Max concentration of limiting input [S] photosynthetic rate 1/2 max K value

Ecological implications:  photosynthesis responds in a non-linear fashion to changes in all essential inputs Max concentration of limiting input [S] photosynthetic rate 1/2 max K value Monod’s model

Ecological implications:  photosynthesis responds in a non-linear fashion to changes in all essential inputs  small changes in rare inputs can induce large responses, but large changes in common inputs can have relatively small consequences Max concentration of limiting input [S] photosynthetic rate 1/2 max K value Monod’s model

Physiological richness

yield or growth of an organisms is determined by the abundance of that substance which, in relationship to the needs of the organism, is least abundant in the environment [i.e.,at a minimum] Liebig’s Law of the minimum

 there is always some input which is least abundant and limits primary production

limiting factors may change over time and across space co-limitations are important

[Si] : [TP] <160

RCC: does it work?      decomposers     allocthonous autochthonous DETRITAL POOL [algae+ macrophytes] invertivorous fish /birds grazers shredders collector-gathers filter-feeders invert predators [terrestrial leaves, wood, DOC ]     piscivorous fish piscivorous birds /mammals Bacteria & fungi Riparian condition Veloc Light Nutrients

Invert. biomass Algal Biomass Nutrients Grazer biomass Algal Biomass Nutrients FISH? INSECT PREDATORS? FLOODS? DROUGHTS? POLLUTION? DISEASE? Top-down community controls and high disturbance regimes can obscure simple responses to nutrient inputs

SRP [ug/l -1 ] Biomass [mg d.w. m -2 ] Periphyton Invertebrates Drift Bedrock

Figure 3. Hypothetical (A) and fitted (B) path diagram illustrating results of CSA of the effects of hydrologic disturbance on benthic algal and primary consumer biomass in Knobs and glacial drift streams. Rectangles are observed exogenous and endogenous variables, ovals are unmeasured, latent variables, and small circles are error variances. Numbers give the magnitude of direct effects, and numbers in italics are squared multiple correlations. Bold indicates significant effects at p < 0.05 based on bootstrapped error estimates (n = 133).

Oxygen consumed Biological Oxyen Demand BOD ppm Oxygen ppm time