Nutrient dynamics in

freshwaters

Chapter 13 (C)

Chapter 14 (N, P)

The greatest analgesic, soporific, stimulant, tranquilizer, narcotic, and to some extent

even antibiotic -- in short, the closest thing to a genuine panacea -- known to medical

science is work. -Thomas Szasz, author, professor of psychiatry (b. 1920)

Today

Nutrients dynamics

Lab: move up the OM collection

Test 3 (Wed)

Next week

– Hydrology

– Lab: flow regime analysis

– EOW 17-18

Nutrient cycle: Terms

Flux vs. Compartments (source/sink)

Budget

Assimilation

Re-mineralization

Sequestration

Redox

– High (oxic)

– Low (reducing, e.g., methanogenesis CO2

CH4)

FIGURE 13.7

Diagram of a hypothetical nutrient cycle. This will be the general format used to represent nutrient cycles. Oxic

processes are above the center line and anoxic processes are below. Those that move on the center line are required,

independent of O2 concentration. Inorganic forms are listed from left to right, from reduced to oxidized. Thus,

transformations are generally occurring with potential energy if they move from left to right in the top half of the

diagram or from right to left in the bottom half of the diagram.

Generalized Nutrient Cycle

Carbon

Why do you need it?

Carbon Cycle

Compartments

– Sources

– Sinks (sequestered C)

Fluxes (i.e., processes)

– Assimilatory

– Re-mineralization

Budgets (ignore for now)

©2010 Elsevier, Inc.

FIGURE 13.8

A diagram of the generalized carbon cycle.

Nitrogen

Why?

Forms of N

N2

N2O

Nitrate (NO3-)*

Nitrite (NO2-)

Ammonium (NH4-)*

NH3

DIN (sum of the ions)

DON (0.45 µm filter)

PON (e.g., fish)

N sources/sinks

N processes

N fixation

– Lightning

– Rhizobia

– Haber process

– Burning fossil fuels

– Cyanobacteria

Heterocytes and nitrogenase

©2010 Elsevier, Inc.

FIGURE 14.1

Streamers composed of the sulfur-oxidizing bacterium Thermothrix at Mammoth Terrace, Yellowstone National

Park (courtesy of R. W. Castenholz) and a transmission electron micrograph of a heterocyst (the site of nitrogen

fixation in Nostoc and other cyanobacteria) attached to a smaller dividing vegetative cell with a diameter of

approximately 8 μm. (Micrograph courtesy of N. J. Lang).

N processes

Nitrification

Denitification

– Nitrate reduction

N processes

Uptake

Excretion

Ammonification

N Cycle

N2

N fixation (anaerobic, cyanobacteria) PON

Detrital

PoolDie

PON

Animals

DON

NH4-

DON

NO2-

DON

NO3-

PON

Plants

NO3-

PON

Detrital

Pool

PON

Detrital

Pool

PON

Detrital

Pool

Nitri

fication (

aero

bic

)

Excrete

BGA

PON

Die

©2010 Elsevier, Inc.

FIGURE 14.6

A conceptual diagram of the nitrogen cycle.

Nitrogen Dynamics

Sources

– Lakes

– Streams

Sinks/Losses

– Lakes

– Streams

Seasonal N Distribution in Lakes

Nitra

te, N

itriteN

itriteN

H4

Seasonal N Distribution in Lakes

FIGURE 14.4

Distribution of nitrate (A) and ammonium (B) in hypereutrophic Wintergreen Lake, Michigan, as a function of depth

and time. Ice cover occurred from January to March. Darker colors represent higher concentrations. Contours are

reported in μg liter21. (Reproduced with permission from Wetzel, 1983).

N in Streams

©2010 Elsevier, Inc.

FIGURE 14.7

Correlation between nitrate intake and rates of gastrointestinal cancer. (After P. E. Hartman. 1983. Reprinted by

permission of Wiley–Liss, Inc., a subsidiary of John Wiley & Sons, Inc.).

Phosphorus

Why needed?

Forms of P

Rare

Soluble Particulate

Inorganic PO43- (BAP) Mineral apatites

Organic ATP, phospholipids Detritus, POP

Ca(PO4)2

FePO4

e.g., a fish

Phosphorus fluxes

Geophysical weathering

Cycling (rapid uptake)

– DOP

– POP

– DIP

Sedimentation (attachment)

– Importance of macrophytes

Role of P-ase (alkaline phosphatase)

©2010 Elsevier, Inc.

FIGURE 14.9

A diagram of the phosphorus cycle.

P Cycle in a Lake

Rock

Inorganic

sediments

DIP,

BAP

Organic

sediments

Trophic

dynamics

Decay

Organic detritus,

soluble POP,

leaching, lysis

Total P distribution

90% particulate

10% soluble

P – Sediment Interaction

Mechanical attachment of P

P dynamics

Sources

– Lakes

– Streams

Sinks/Losses

– Lakes

– Streams

What is more N and P limited?

Streams or lakes? Why?

Nutrient Spiraling

Time for

1 cycleSpiral distance

Nutrient

available

here

©2010 Elsevier, Inc.

FIGURE 24.7

A diagram of nutrient spiraling in streams. S is the total spiral length, Sp is the time spent in particulate form in

water column or the benthic zone and Sw is the average time spent in the water. Average velocity is greater in the

riffle on the left, so spiral length is greater than in the pool at the right.

Nutrient loading and

Eutrophication

Nutrient loading

N sources (tera grams per year)

N fixation

Lightning – 10

Soil microbes –130

BGA – trivial

Human fertilizers – 80

N fixing crops – 40

Fossil fuels – 20

Deforestation – 40

P sources

Very rare

Human sources (mostly non-point)

– Fertilizers

– Detergents

– Sewage

– Livestock waste

Eutrophication

Human activities

N and P loading

Alteration of physico-chemical

and biological conditions

Processes/Events

Lake Trophic Status

Oligotrophic

Mesotrophic

Eutrophic

Eutrophication

Where is it more of a problem?

– Lakes

– Streams / rivers

Mitigation

Remove cause / control inputs

– Point sources

– Non-point

Treat symptoms

– Bio-manipulation

IndicatorsTable 18.1

Chl a indicator

Fig. 18.2

SolutionsHodgson 2005

Dec spiraling distance in

upstream areas and HWs.

Maintain HW structure and

function (retentiveness)

Table 18.3

Trophic cascade theory

FIGURE 12.13

O2 increase

Super-saturation

Anoxia:

Winter kill

Summer kill

Implications for

wetland plants

©2010 Elsevier, Inc.

FIGURE 14.8

A conceptual diagram of the sulfur cycle. A 5 assimilation.

©2010 Elsevier, Inc.

FIGURE 14.10

Concentration of silica as a function of depth and time in hypereutrophic Wintergreen Lake, Michigan (A), and

oligotrophic Lawrence Lake, Michigan (B). Concentrations are given in mg liter21, with darker contour fills

corresponding to greater concentrations. (Reproduced with permission from Wetzel, 1983).

©2010 Elsevier, Inc.

FIGURE 14.11

The relationship between epilimnetic silicon and biomass of the diatom, Asterionella, in Lake Windermere, England.

Note how decreases in dissolved silica correspond with high densities of diatoms. (Data from Lund, 1964).

©2010 Elsevier, Inc.

FIGURE 14.12

A conceptual diagram of the iron cycle.

©2010 Elsevier, Inc.

FIGURE 14.13

Relationship among redox gradients, dissolved oxygen, nutrient concentrations, and functional groups of

microorganisms responsible for biogeochemical fluxes. This figure illustrates the steep gradients that occur at

oxic/anoxic interfaces, and how such interfaces are a hot spot for biogeochemical activities.