Dissolved Gases

DO and Eutrophication

Ch. 12 / 16 / 18

Dissolved gases

DO 14 PPM in water

– 21% in atmosphere

N2

CO2

~400 PPM atm

Biological processes that affect

DO (and DIC)10 productivity

Cellular respiration

– Reactions here

GPP

– NPP = GPP – Rs

– NPP = 0

– NPP > 0

– NPP < 0

Old edition

Physical factors

1. Temp

2. Pressure

3. Agitation

Fig. 12.7

Uptake of DO

SA: Volume

Tracheal

Tracheal system

ending in external gills

Circulatory system

extended in gills

Spatial / Temporal Variation in

DOSeason, time of day

Location, depth

Depth - clinograde

Organic rain

Reduced chemicals in ground

water

warm

Depth - orthograde

Depth – positive heterograde

Organic rain

Depth – negative heterograde

Other spatial patterns in DO

Lakes: Littoral vs. pelagic

Groundwater

Lake

Aquarium periphyton

Stream

Fig. 12.11

Other spatial patterns in DO

Rivers

– Longitudinal variation (RCC)

– Groundwater, springs, HWs, creeks, streams,

rivers, major rivers, estuaries (customary size

gradient !!)

– Thermal pollution

– Nutrient loading - eutrophication

Seasonal variation in DO

ICE

anoxia

Metalimnetic

Maximum

Groundwater

Lake

Aquarium periphyton

Stream

Space and

time (daily)

DO, Nutrients, and Eutrophication

Nutrient loading

– Sources

N

P

Eutrophication

– Oligotrophic

– Mesotrophic

– Eutrophic

Eutrophication

Where is it more of a problem?

– Lakes

– Streams / rivers

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