Micro Nutrient

INORGANIC MICRONUTRIENTS 

needed in trace quantities:

 needed in small amounts by all algae: chloride, iron, manganese, copper, molibdenum, Zn  Requires by members of a few algal groups: boron, cobalt, iodine, silicon, sodium, vanadium 9. Molibdenum (Mo)  Stimulates algal growth  Concentrated in algal cells & sediments  Active centre of nitrate reductase & nitrogenase enzymes 2. Cobalt  Essential to life; when lacking, it leads to the inactivation of certain enzymes  Serve as cofactors or coenzymes; function in binding substrate molecules to the enzymeactive site  Found in the unique vitamin B12 (cyanocobalamin); needed by algae

3. Copper  CuSO4.5H2O – algacide in aquatic systems  accumulate as copper carbonate in the sediments; detrimental to the bottom fauna  severely inhibited N-fixing by blue-green algae 4. Zinc  constituent of dehydrogenase: required in photosynthesis as an agent in hydrogen transfer  synthesis of protein  precipitates in the lake sediments as a sulphide 5. Vanadium  increases the rate of photosynthesis in the green algae Scenedesmus  substituting for Mo  used by Azotobacter as a catalyst for nitrogen reduction

Elements required in large quantities •

Silica (SiO2)

 25-60% of the dry weight of diatom; limiting nutrient for diatom growth  Silicic acid (H2SiO4): can be used by algae  Sources of Si in lakes: - rocks weathering: release soluble silica (SiO2) - inflows & from below the photic zone - release from anoxic sediments Weathering of feldspar by weak carbonic acid to form kaolinite: 2NaAlSi3O8 + 2CO2 + 3H2O

4SiO2 + Al2Si2O5(OH)4 +

2Na+ + 2HCO3-

 Stable diatom frustules: acid wash to remove organic material: - used by paleolimnologist to interpret the trophic status of lakes through time

The Si cycle in lakes

Animal feeding, death & sedimentation

SiO2.nH2O cell walls Algal growth

Lake sediments (diatom frustules) SiO2.nH2O

Frustules dissolve

Dissolved H2SiO4

Precipitation Compression over geological time spans

Complex rock/soil silicates (Al.FeSiO2)

Rock weathering & river inflow

2. Calcium CaCO3:  major skeletal-strengthening material in animals  cell wall in algae  the role of Ca and its effect on pH and CO2HCO3- system  Ca salts: the main cause of hard water CaCO3 + H2CO3 Ca(HCO3)2

CaCO3 + CO2 + H2O Ca2+ + 2HCO3-

 hard water is water that contains dissolved chalk & other minerals  the effect of hard water: - scale, scum & tidemarks around the baths & basins - blocked deposits on all water heating elements - clogging of pipework & premature failure of water heaters - more soap is required for washing

3. Magnesium  needed by cells for phosphorus transfer

ATP

Mg 2+

ADP + P + energy

 major role in algal photosynthesis  does not play a major role in limiting the growth or distribution of biota except in the higher than normal sodium levels  plants show Mg deficiency when sodium levels increase  sodium compete for binding sites in the cell

4. Sodium (Na)  very reactive & soluble  the 3rd most abundant metal in lakes & streams  sources: - igneous rocks: albite (NaAlSi3O8); nepheline (NaAlSiO4) - halite (NaCl): water soluble mineral  types of sodium lakes:

 Saltern lake (NaCl) – algae population low  Lakes typified by much Na2SO4 – algae population low  Soda lakes characterized by NaHCO3 and Na2CO3 (alkali waters – high pH); high population of algae  Na: minor factor in eutrophication  Na per se does not always favor enormous blooms of algae

Saltern lake

Water runoff from snowmelt on nearby tall volcanoes formed lakes in the altiplano of the Andes. At this lake, positioned in northernmost Chile on the border with Bolivia, long-term evaporation from the lake surface has produced saline water by concentrating salts left behind.

5. Potassium (K) Sources: • • •

weathering of rocks: Feldspar (KAlSi3O8) Leucite (KAlSi2O6)

 K2CO3, KOH, KCl: types of K available in water  Required for all cells: as an enzyme activator  Cell membranes must continually pump in K and pump out Na

6. Sulfur  important in protein structure  abundance: rarely limits the growth or distribution of the aquatic biota  stable form: sulphate (SO42-)  complex 3-dimensional structure of enzymes  cell division  S deficiency can inhibit algal population: hindering chlorophyll synthesis  H2S: - toxic gas, abundant in the hypolimnion of eutrophic lakes - poisonous to aerobic organisms: inactivate the enzyme cyctochrome oxidase

Sulfate reducers:(anoxic condition) CaSO4 + 2C CaS + CO2 + H2O

CaS + 2CO2 CaCO3 +H2S

• carried out by heterotrophic bacteria – C from organic material Sulfur oxidizers: light CO2 + 2H2S

(CH2O) + H2O + 2S Cell material

• green sulfur bacteria – utilize H2S as hydrogen donor, for the reduction of CO2 • photolithotrophic – adapt to dim light

Sulfur Cycle

Bu r

nin g

SO2

Lig h

t, O

2

aerial SO3

O2 H2S H2O

S Anoxic bacterial decay

H2SO4

aquatic

SO4 2Erosion, Weathering

Sedimentation

terrestrial Sediments, rocks Fossil fuels

Lake Mixing

Lake Stratified

SPRING

SUMMER

Lake Mixing

FALL

Upper water Epilimnion

PO43Deep water

Fe2+ + S2-

Hypolimnion FeS Fe3+ + PO4

Fe3+ + PO4

Fe3+ + PO4 Fe2+ PO43SO43SEDIMENTS

Oxygenated microzone at mud-water interface

Anoxic microzone at mud-water interface

H2S

Fe3+ + PO4

SO4

Oxygenated microzone

7. Chloride Chloride iron:  required by photosynthesizing cells for the photolysis of water to release O2.  ATP formation Sources: j. Edaphic factors  Igneous rocks: sodalite (Na(AlSiO4)6Cl2) b. Atmosphere  Windblown from the sea coasts  Volcanic gases: reaction with rainwater to produce HCl c. Pollution  Domestic sewage  Seepage from septic tanks  Salting (NaCl) and CaCl2 of city streets & highways during winter Free chlorine: Used as disinfectant to kill harmful bacteria

8. Iron  Ferrous (Fe2+)  ferric (Fe3+)  oxygenated: Fe3+ adsorbed by PO43 anoxic lake sediments: Fe3+

Fe2+

 in eutrophic lakes, metals (eg. Fe3+ ) are used to control PO43- levels  in the hypolimnia of eutrophic lakes, release of large quantities of Fe2+ (more soluble)  Fe3+ insoluble – deposited on the sediments as a rust-colored layer (ocher) (Fe(OH)3)  iron salts can be used to clean up eutrophic lakes