Limnology Unit 2

Most dominant ions in freshwaters

calcium and bicarbonate

Hardwater lakes

lakes with high concentrations of bicarbonate as a result of high weathering from limestone geology

Softwater lakes

lakes with lower concentrations of ions/bicarbonate as a result of igneous geology

Least soluble ion

CaCO3, most likely to precipitate out of solutions in high concentrations

saturation/equilibrium concentration

amount of gas that will be present in water at a given temperature (affected by pressure and salinity)

Supersaturated

higher concentration that expected at a given temperature

undersaturated/subsaturated

lower concentration than expected at a given temperature

Atmospheric flux/exchange

oxygen and carbon dioxide are moving across the air-water interface, causing a net gain or loss depending on the concentration gradient multiplied by the gas exchange coefficient

Concentration gradient

equilibrium concentration-actual concentration (+ = oxygen moves in, - = oxygen moves out)

Gas exchange coefficient (k)

depends on turbulence near the surface

Clinograde curve

oxygen concentration is declining with depth; most common pattern in Ohio lakes

Orthograde curve

oxygen concentration is increasing with depth; common in cases with limited biology

Positive heterograde curve

a curve with a sharp increase in O2 concentration in the metalimnion, commonly due to accumulation from lack of mixing

Negative heterograde curve

sharply decreased concentrations in the metalimnion due to increased respiration in the metalimnion, possibly because of accumulation of dead algae

pH

the strength of hydrogen

Acidified/acidic waters

lakes below pH 6; can be created either via acid rain or natural causes

Whiting event

calcium carbonate is precipitated out after pH or temperature is increased (likely via CO2 decrease), causing distinct swirls of white in water bodies

Nutrients

elements or compounds essential for biomass production

Macronutrients

C,H,O,N,S,P,KNa,Ca,Mg, and Cl

Liebig’s laws of minimum

growth is limited by the scarcest resource relative to need, not by total of resources available

Redfield ratio

C106 H263 O110 N16 P1, stoichiometry of nutrients needed to make algal cells

Soluble inorganic phosphorus

phosphate (PO4 3-)

Soluble organic phosphorus

DNA, RNA, phospholipids, etc; assumed to be minor

Particulate organic phosphorus

living and dead cells, algae, bacteria, etc

Particulate inorganic phosphorus

PO4 3- bound to clay or minerals

Soluble organic nitrogen

proteins, amino acids, tannins

Soluble inorganic nitrogen

NO3/NO2, NH4 (nitrate/nitrite, ammonia)

Nitrogen gases

N2, N2O

Particulate organic nitrogen

living and dead cells; algae, bacteria, etc

Oxidation state of ammonia

-3; most reduced, same as amines (amino acids)

Oxidation state of NO3

+5; most oxidized

Oxidation state of N2

0; base level

Nitrogen assimilation

conversion of ammonium or nitrate into amino acids

Nitrogen ammonification

an organic nitrogen is converted to ammonia, typically through decomposition by bacteria or animals

Nitrification

an aerobic reaction using ammonia as an energy course to fix carbon; causes a loss of ammonia and oxygen from the water column and adds nitrate and acidity

Denitrification

conversion of nitrate to N2 gas using nitrate as a terminal electron acceptor in the absence of oxygen; common in anoxic hypolimnions

DNRA

reduction of nitrate to ammonia carried out by bacteria using nitrate as an electron acceptor in anoxic environments

Annamox

an anaerobic, autotrophic process where nitrite is reduced and ammonia is oxidized, creating N2 gas

Draw the surface water phosphorus cycle map.

Draw the nitrogen cycle map.

list the important micronutrients

iron, molybdenum, and zinc