lake's physical, chemical and biological aspects and interactions

1. Geronimo R. Rosario

2.  Limnology is the study of inland waters - lakes (both
freshwater and saline), reservoirs, rivers, streams,
wetlands, and groundwater - as ecological systems
interacting with their drainage basins and the atmosphere.

 Freshwater Environment
 Lake
 Pond
 River
 Swamp
 Marsh
 Bog
 Fen

3. 
 1. Lotic - running water series (ex. river)
 - continuous and with a definite direction.
 Sequence: brook creek river
 2. Lentic- standing water series
 Sequence: lake, pond, swamp

4.  Lake is a body of water occupied in a basin and lacking
continuity with the sea. It has a considerable area and deep
enough to stratify.

 Pond is a small shallow body of water either formed
through depression or man-made.

 Marsh is a type of wetland that is dominated by
herbaceous rather than woody plant species. Marshes can
often be found at the edges of lakes and streams, where
they form a transition between the aquatic and terrestrial
ecosystems. They are often dominated by grasses, rushes
or reeds.


5.  Swamp is a wetland that is forested. Many swamps
occur along large rivers, where they are critically
dependent upon natural water level fluctuations. Other
swamps occur on the shores of large lakes.
 Bog is a wetland that accumulates peat, a deposit of
dead plant material—often mosses. , and in a majority of
cases, Sphagnum moss. It is one of the four main types
of wetlands. Other names for bogs include mire,
quagmire and muskeg.

6.  Fen is one of the four main types of wetland, and is
usually fed by mineral-rich surface water or groundwater.
 Fens are characterized by their water chemistry, which
is neutral or alkaline, with relatively high dissolved
mineral levels but few other plant nurients. They are
usually dominated by grasses and sedges, and typically
have brown mosses in general

7.  Lake Ecology – is the study of the lake’s biotic
and abiotic interaction/relationship.

8.  Glacial lake -lake formed by glaciers. Ex. Pingo
lake

9.  Tectonic lake- Lake formed by movements of the
earth’s crust
◦ Graben lakes – formed between faults and adjacent
highlands.
◦ Ex. Lake Baikal of Siberia – deepest lake in the world, Lake
Tahoff – California, Lake Tanganyika – East Africa, 2nd deepest
lake.
◦ Uplift lakes – result of epeirogenesis
 Epeirogenesis – wide reaching tectonic events that raise large
crustal blocks and sometimes bring about the formation of
enormous basins. Ex. Caspian Sea
◦ Earthquake lakes – water is spilled through a series of
earthquake events forming lakes. Ex. Reelfoot lake – United
States - spilled from the Mississippi River.

10. Lake Baikal Lake Tanganyika
Caspian Sea Reelfoot Lake

11.  Landslide lakes – formed from the impoundment
of stream valleys by rock slides, mud floods and
other mass movements of rocks.

12.  Volcanic lake- formed through volcanic actions.
◦ Crater lake- Lakes formed by volcanoes.
◦ Lava lake- formed by lava depression
◦ Caulee lake – magma hardened and formed a basin.

13.  Ice-scour lake- Where ice sheets move over
relatively flat surfaces of hard jointed or fractured
rock, hollow basins are formed and subsequently
filled with water
 Solution lakes – lakes in carbonic substrates
(lakes in salt collapsy bases)

14.  Aeolian lake – formed due to the erosive force of
the wind.

15.  Fluviatile lakes – formed by founding of deltas.
◦ Levee lakes – shallow, elongate, parallel to stream
◦ Oxbow lakes – formed by isolated loops of meandering
mature streams


16.  Shoreline lakes – formed by wave actions in the
shoreline. Ex. Beach pools
 Lake basins impounded or excavated by
organisms. Ex. Beaver

17.  Lake Surface Area (Km2) Maximum Depth (M2)

 Superior (America) 83,300 307
 Victoria (Africa) 63,800 79
 Huron 59,510 223
 Michigan 57,850 265
 Tanganyika (Africa) 34,000 572
 Baikal (Siberia, Russia and China) 31,500 730
 Malawi (Africa) 30,800 273
 Erie (Canada) 25,820 64
 Winnipeg 24,530 19
 Ontario 18,760 225

18.  Laguna de Bay 89,076.30 ha.
 Lanao 33,999.70
 Taal 24,356.40
 Mainit 17,430.20
 Naiyan 7,899.50
 Buluan 6,134.20
 Bato 3,792.50
 Pagusi 2,531.50
 Laabas 2,140.80
 Lumo 1,192.00
 Buhi 1,105.80

19.  The lake is divided into different “zones”
determined by depth and distance from the
shoreline
 littoral zone
 limnetic zone
 profundal zone
 Photic zone
 Benthic zone

20.  Littoral zone- the shallow and warmest zone of
the lake.
◦ It sustains a fairly diverse community (several species of
algae (like diatoms) , rooted and floating aquatic plants,
grazing snails, Clams, Insects, Crustaceans, Fishes and
amphibians)
◦ subject to fluctuating temperature and erosion of shore
materials through wave actions
◦ sediment is coarse
◦ unprotected shores, shallow water depth, well lighted, it’s
a bond from shoreline to the depth where aquatic plants
disappear.
◦ wave action is extreme

21.  Limnetic zone- near-surface open water
surrounded by the littoral zone
◦ well-lighted (like the littoral zone) and is dominated by
plankton, both phytoplankton and zooplankton
◦ plankton are small organisms that play a crucial role in
the food chain – most life would not be possible without
them
◦ variety of freshwater fish also occupy this zone
◦ it is where the trophogenic zone occurs
 Trophogenic- synthesis of organic carbon occurs
◦ largely defined by the epilimnion

22.  Profundal zone – cold and dense region of the lake. It
is also called as the aphotic zone where light is
reduced.
◦ current minimum
◦ temperature nearly uniform
◦ oxygen scanty, depleted
◦ methane and carbon dioxide abundant
◦ hydrogen concentration is high because of the presence of
carbonic acid.
◦ decomposing, decaying matter
◦ found in the hypolimnion
◦ sediments are fine particles
◦ benthic organisms dominate

23.  Photic zone- lighted zone of the lake

 Primary production in the photic zone is influenced by three
major factors
◦ Nutrients
◦ Light- For photosynthesis
◦ Grazing pressure -the rate at which the plants are eaten by herbivores.

 Nutrients especially phosphate and nitrate, are often scarce in
the photic zone because they are used up quickly by plants
during photosynthesis.
 External inputs of nutrients are received through:
◦ Rainfall
◦ River flow
◦ Weathering of rocks and soil
◦ Human activities- sewage dumping

24.  Benthic zone- bottom area of the lake.

◦ Many groups and varieties of animals live here, a few are
worms, crustaceans, and protozoa.
◦ The life in this zone is mostly made up of bottom dwellers
which get most of their food from dead and decaying
organisms.
◦ most of the organisms in the benthic zone are scavengers
because they depend on dead flesh as their main food source.
◦ Organisms here tend to tolerate cooler temperatures well.
◦ Place where decomposition takes place.
◦ For the profundal and benthic zones, low levels of
photosynthesis result in low levels of dissolved oxygen

25.  Oligotrophic- poor nutrient
 Mesotrophic- middle/intermediate
 Eutrophic – high nutrient

26.  Water is clear and appears blue to blue green in the
sunlight
 The nutrient content in the water is low; and although
nitrogen is abundant, phosphorus is highly limited
 Low production of organic mater, particularly
phytoplankton
 Oxygen concentration remains high
 Free of weeds or large algae blooms
 Can have some large game fish, but small populations
 No food for bacteria
 Sandy, rocky bottom


27.  Lakes that receive large amounts of organic matter from
surrounding lands particularly in the form of humic
materials that stain the water brown
 Low only in planktonic vegetation but have generally
high productive littoral zones
 Littoral vegetation dominates the metabolism of the lake,
providing a source of both dissolved and particulate
organic matter
 Some organic sediment accumulating
 Some loss of oxygen in the lower waters

28.  High productivity
 High depth of organic sediment
 associated with high nitrogen and phosphorus
 increase in growth of algae and other aquatic
plants.
 May experience oxygen depletion– Anoxic lower
layer

29.  Epilimnion- an upper layer of circulating warm water,
usually no more than 6 m (20 ft) deep, where
dissolved oxygen concentrations are moderate to
high.
 Metalimnion or thermocline- a layer of rapid
temperature and oxygen decrease with depth, often
quite thin, separating the upper and lower layers.
 Hypolimnion – a cold, deep-water, non-circulating
layer in which oxygen is low or absent.

30.  The top-most layer in a thermally stratified lake.
 It is warmer and typically has a higher pH and dissolved
oxygen concentration than the hypolimnion.
 It typically mixed as a result of surface wind-mixing.
 Free to exchange dissolved gases (ie O2 and CO2) with
the atmosphere.
 It contains the most phytoplankton


31.  Temperature changes more rapidly with depth than it does in the
layers above or below.
 Thermoclines may be a semi-permanent feature of the body of
water in which they occur, or they may form temporarily in response
to phenomena such as the radiative heating/cooling of surface water
during the day/night.
 Factors that affect the depth and thickness of a thermocline include
seasonal weather variations, latitude, and local environmental
conditions, such as tides and currents.

32.  Typically the hypolimnion is the coldest layer of a lake in
summer, and the warmest layer during winter. Being at
depth, it is isolated from surface wind-mixing during
summer, and usually receives insufficient irradiance
(light) for photosynthesis to occur.
 In deep, temperate lakes, the bottom-most waters of the
hypolimnion are typically close to 4°C throughout the
year. The hypolimnion may be much warmer in lakes at
warmer latitudes.

33.  Lake overturn is a circulation which recharges
oxygen and nutrients through the basin.
In temperate lakes, the
changing of the seasons
help move water in the
lake.
Tropical lakes often stay
stratified because warm
water always stays on the
top.
In temperate lakes the
winter months chill the
surface water so that it
gets colder than the water
underneath, causing it to
sink. This happens in the
spring and fall

34.  Amictic: never mix as they are permanently frozen.
 Meromictic: mix only partially, the deeper layers
never mix either because of high water density caused
by dissolved substances or because the lake is
protected from wind effects.
 Holomictic: mix completely.
 Oligomictic: do not mix every year as they are large
and have higher heat storing capacity, the mixing
depending on specific climatic conditions.
 Monomictic: mix only once each year, either in winter
or summer.
 Dimictic: mix twice a year and are the most common
lakes in temperate latitudes.
 Polymictic: mixing frequently, they are shallow
tropical lakes with great wind exposure.

35.  Mixolimnion- the zone
that mixes completely
at least once a year
 Chemocline- The
intermediate layer,
where there is a sudden
change in density at the
upper edge of bottom
layer accumulating salts
or dissolved organic
matter.
 Monimolimnion- the
non-mixing bottom layer

36.  Meromixis can be:
 Ectogenic when external events transport salt
water into a freshwater lake or vice versa;
 Crenogenic, when a saline spring at the bottom of
the lake introduces in it water rich in salts
 Biogenic, when salts from organic matter
decomposition in sediments or from carbonates
precipitation due to pH changes promoted by
photosynthesis accumulate in the deeper layers.

37.  Lakes are extremely variable in their physical,
chemical and biological characteristics.

 Physical (level of light, temperature and water
currents)
 Chemical ( nutrients, major ions and
contaminants)
 Biological( biomass, population numbers and
growth)

38.  Light
 Temperature
 Water Currents

39.  Solar radiation – fundamentally important
 Plankton production – photosynthesis (day)
 Respiration (night)
 Metabolism of the lake – controls the ecosystem
 Ozone and oxygen – absorb ultraviolet rays
 Vapor, Ozone and carbon dioxide – absorb
infrared light

40.  Light plays an important role in lake ecology and
determines the potential rate of photosynthesis, which
supplies dissolved oxygen and food in the water.

 Autochthonous- energy stored in photosynthetically
formed organic matter is both synthesised within the
lake or stream
 Allochthonous - energy stored in photosynthetically
formed organic matter within drainage basin and
brought to the lake or stream in various forms

41.  Light intensity at the lake surface
varies seasonally and with cloud
cover and decreases with depth
down the water column. The
deeper into the water column that
light can penetrate, the deeper
photosynthesis can occur.
 Photosynthetic organisms include
algae suspended in the water
(phytoplankton), algae attached to
surfaces (periphyton), and
vascular aquatic plants
(macrophytes).

42.  Factors Influencing Light Penetration
◦ Latitude
◦ Season
◦ Angle of contact of light rays at water surface
◦ Time of the day
◦ Degree of cloudiness or clearness of the sky, presence of
fog, smoke, dust or other atmospheric conditions.
◦ Dissolved ions – diminish light absorption. Traces of
ammonia, proteins and nitrates in solution still reduce
transparency of water to Ultraviolet light
◦ Suspended materials – composed of organic or inorganic
materials. They screen out the light (ex. Phytoplankton,
clay particles and abiotic materials)
◦ Presence of ice or snow cover – more light is reflected

43.  Water is most dense at 4°C and becomes less
dense at both higher and lower temperatures.
Because of this density-temperature relationship,
many lakes in temperate climates tend to stratify,
that is, they separate into distinct layers.

 Thermal Stratification – the presence of different
temperatures in a body of water
 - Occurs in deep bodies of water
 - Sometimes, it also occur in shallow ponds

44.  density differences
 Turbidity – turbid water absorbs more heat in a
warm sunny day
 No water inflow

45.  Cooling the surface through evaporation
 Inflow of cold water rain
 Strong wind action – cause water turbulence
 use of mechanical aerators
 Disappearance of heavy phytoplankton blooms

47.  The watershed, also called the drainage basin, is
all of the land and water areas that drain toward a
particular river or lake.
 Thus, a watershed is defined in terms of the
selected lake (or river). There can be subwater
sheds within watersheds.
 For example, a tributary to a lake has its own
watershed, which is part of the larger total
drainage area to the lake.

48.  Morphometry - refers to physical factors (shape,
size, structure, etc) that determine the lake basin.
 Generally, lakes that are small in surface area and
larger in depth exhibit higher water quality than
those that are larger in surface area and shallow
in depth. This is referred to as surface to volume
ratio (S/V).

49.  Increasing ratio of watershed to lake area- water quality
decreases
◦ Seepage lake- Lake with small watersheds, maintained primarily
by groundwater flow.
◦ Drainage lake- lake fed by inflowing streams or rivers are known
as drainage lakes
 Land use – Urban areas tend to have higher flushing rate
causing erosion
 Soil type
 Type and abundance of vegetation- Areas with native
undisturbed vegetation are less prone to erosion than
areas with disturbed vegetation like agricultural lands.
 Open and closed system- closed system is more stagnant
than open system

50.  Dissolved Oxygen
 Carbon Dioxide
 pH
 Nitrogen
 Phosphorous

51.  The chemical composition of a lake is a
function
◦ Climate
◦ Hydrology
◦ Basin geology.

52. Anions Percent Cations Percent
1. Bicarbonate
(HCO3)
73% 1. Calcium (Ca 2+) 63%
2. Sulfate (SO4) 16% 2. Magnessium
(Mg2+)
17%
3. Chloride (Cl) 10% 3. Sodium (Na+) 15%
4. Potassium (K+) 4%
Other <1% Other < 1%

53.  Calcium is present in all surface waters as Ca2+ and
is usually dissolved from rocks rich in calcium
minerals.
 Responsible for water hardness together with Mg
 Hard water lakes- high concentrations of calcium and
magnesium
 Soft-water lakes- low concentrations of calcium and
magnesium
 It is an important constituent in all organisms and is
incorporated into the shells of many invertebrates and
bones of vertebrates.
 Calcium concentration in natural water is <15 mg/L.

54.  Magnesium also contributes to hardness in water.
 It occurs in many of the organometallic
compounds and in organic matter since it is an
important element for living organisms.
 Natural concentrations of magnesium vary from 1
to > 100 mg/L.

55.  Chloride. Most chlorine occurs as chloride in
solution.
 In a clean surface water, chloride concentrations
are less than 10 mg/L and sometimes less than 2
mg/L.
 Higher concentrations can occur due to sewage,
industrial effluents and agricultural and road run-
off.

56.  Inorganic CO2 arises from atmosphere and
biological respiration.
 The relative amounts of carbonates, bicarbonates
and carbonic acid are related to pH.
 As a result of weathering of rocks combined with
the pH range of surface waters (6-8.2),
bicarbonate is found as the dominant anion in
most surface waters.
 Carbonate is uncommon in natural surface waters
because they rarely exceed pH 9.0.

57.  Sulphate is naturally present in surface water as SO4.
 It is the stable, oxidised form of sulphur that is readily
available in water. Industrial discharges can also add
significant amounts of sulphate to surface waters.
 Sulphate can be used as an oxygen source by
bacteria that convert it into hydrogen sulphide (H2S)
under anaerobic conditions.
 Sulphate concentrations in natural waters are usually
between 2mg/L to 80 mg/L and exceed 1000 mg/L
near industrial discharge.

58.  Sodium is found in the ionic form and in plant and
animal matter.
 All natural waters contain some sodium, as its salts
are highly soluble in water.
 Sewage and industrial effluents increase the presence
of sodium, commonly measured where water is used
for drinking or agriculture, particularly irrigation.
 The surface waters, including those receiving
wastewater have concentrations well below 50 mg/L.


59.  Sulphide formation in surface waters is principally
through anaerobic, bacterial decay of organic
substances in the sediment.
 Traces of sulphide ion occur in unpolluted bottom
sediments due to the decay of vegetation but
higher concentration often indicates the presence
of sewage or industrial effluents.
 Due to its high concentration, toxicity and strong
odour make the water unsuitable for drinking and
other uses.

60.  Fluoride originates from weathering of fluoride
containing minerals and enters surface waters from
run-off and groundwater. Its concentrations vary from
0.05 to 100 mg/L.

 Metals: The metals in freshwater ecosystems include
aluminium, cadmium, chromium, copper, iron,
mercury, zinc, nickel, manganese and lead. The ability
of a water body to support aquatic life as well as its
suitability to other uses depends on the concentration
of metals. Some metals are important for physiological
functions of living tissue and regulate many
biochemical

61.  Oxygen concentration in water is lower as compare
to air.
 About 5 ml of O2 per liter of water in the surface
water
 210 ml of O2 per liter of air in land (consume by
human)
 90% of water (by weight) but not biologically
available or important in this form
 Probably the most important single indicator of
aquatic conditions for biota
 Concentration in water generally expressed as PPM
(Parts per million) = mg/l, or as percent saturation:
 = 100% amount present
 solubility

62.  Sources of Oxygen
 Photosynthesis
 Atmospheric air (diffusion)

 Losses of Oxygen
 Respiration
 Decomposition
 Diffusion

63.  Diffusion rate depends on:
 Wave action
(rate increases with increasing wave action)
 Atmospheric pressure
(rate increases with increasing atmospheric
pressure)
 Oxygen saturation of water
(rate decreases with increasing saturation)
 Salinity (rate decreases with increasing salinity)
 Moisture content of air
(rate decreases with increasing humidity)


64.  Lake zonation by oxygen generation
 trophogenic zone /epilimnion-(where organic
matter is synthesised and oxygen generated)
 tropholytic zone (leads to decomposition of
organic matter and lowering of oxygen level).

 Below 5 mg/L - may adversely affect the
functioning and survival of biological communities
 Below 2 mg/L may lead to fish mortality.

65.  Generally, the most important source of carbon for
photosynthesis
 Involved in buffering the pH of neutral and
alkaline lakes

66.  Inorganic Carbon-bicarbonate equilibrium
◦ Carbon dioxide: CO2
◦ Carbonic acid: H2CO3
◦ Bicarbonate: HCO3
-
◦ Carbonate: CO3
2-
 CO2 + H2O H2CO3 HCO3
- + H+ CO3
2- + 2H+
 Organic Carbon

67.  pH is defined as the negative of the logarithm to the
base 10 of the hydrogen ion concentration.
 The pH scale runs from 0 to 14 (i.e., very acidic to
very alkaline) with pH 7 representing a neutral
solution.

 Acidity of water is controlled by:
 Strong mineral acid
 Weak acids (carbonic, humic and fulvic)
 hydrolysing salts of metals such as iron and
aluminium.

68.  photosynthesis
 respiration
 nitrogen assimilation.

69.  The effect of photosynthesis and respiration depends
on carbonate-bicarbonate-carbon dioxide equilibrium.
The simplified formulae for photosynthesis using
carbon dioxide or bicarbonate are:
 6CO2 + 6 H2O  C6H12O6 + 6O2
 6 HCO3 + 6 H  C6H12O6 + 6O2

 Note!
 When pH is less than 6.3 and only carbon dioxide is
present, photosynthesis and respiration have no effect
on the pH. At higher pH values, when other forms of
inorganic carbon are available, photosynthesis and
respiration alter the uptake and release of protons.
This affects the alkalinity or acid-neutralising capacity
of the water.

70.  Nutrients are the basic requirements of plants for their
growth along with water and sunlight.

 Two most important nutrients
 Nitrogen
 Phosphorous

 A nutrient-poor lake may have only about 1g/l of
phosphorous or 50 g/L of nitrogen, while the
most fertile lake may have up to a milligram of
phosphorous or 20-30 mg/L of nitrogen.


71.  Generally considered to be the 2nd most
important nutrient in lakes in terms of limiting the
rate of primary production (Phosphorus being
1st)
 Occurs in many forms and energy states (gas,
organic and inorganic)
◦ Lithosphere 97.6%
◦ Atmosphere 2.3%
◦ Hydrosphere + Biosphere 0.1%
 Important both as a nutrient and (in some forms)
for its toxicity to organisms

72.  A. Sources
 1. Precipitation (wet & dry)
 2. Nitrogen Fixation
 3. Runoff
 B. Losses
 1. Outflow
 2. Denitrification (NO3 => N2)
 3. Sediments

73.  A. Dissolved molecular Nitrogen (N2)
 B. Organic Nitrogen
◦ Proteins Highest Energy
◦ Amino acids
◦ Amines
◦ Humic compounds
 C. Inorganic Nitrogen
◦ NH4
+ Ammonium
◦ NO2
– Nitrite
◦ NO3
– Nitrate Lowest Energy

74. Nitrate/Nitrite – concentrations in drinking water>10
mg/l can cause the disease Methemoglobinemia
Ammonia (especially in the form NH4OH) is toxic to
many organisms
 Amount of NH4
+ vs. NH4OH is pH dependent:

75.  Transformation in nitrogen in the following
order:
◦ mineralization
◦ nitrification
◦ denitrification
◦ nitrogen fixation

76.  Mineralization – is the breakdown and conversion of
complex organic nitrogenous compounds into simple
compounds (such as NH3) by heterotrophic bacteria.
 Nitrification – is the biological oxidation of
ammonia (NH3) to nitrite (NO2) by Nitrosomonas
bacteria and of NO2 to nitrate (NO-3) by nitrobacter
bacteria.
◦ Nitrification is also defined as the aerobic bacterial
conversion of NH3 and organic nitrogen to stable salts,
nitrates.]


77.  Denitrification – is defined as the biological reduction of
NO3 or NO2 to either nitrous oxide (N2O) or free nitrogen
(N2) by Pseudomonas bacteria under either aerobic or
anaerobic condition.

 Nitrogen fixation – is defined as the biological
conversion of atmospheric nitrogen (N2) to inorganic
forms available to plants, whereby they are able to
synthesize proteins. The major nitrogen fixers in ponds
include several species of bacteria and blue-green
algae.

78.  Unpolluted waters may contain small amounts of
ammonia and ammonia compounds (less than
0.1mg/L as nitrogen), but may reach 2-3 mg/L N.
 Higher concentrations are an indication of organic
pollution due to sewage, industrial waste and
fertiliser run-off.
 Natural seasonal fluctuations also occur as a
result of death and decay of aquatic organisms,
particularly phytoplankton and bacteria in
nutritionally rich waters.


79.  Phosphorous is an essential nutrient for living
organisms and exists in water bodies as dissolved and
particulate matter.

 Forms of Phosphorous
 inorganic phosphorous (orthophosphates, like H2PO4
and HPO4);
 suspended particulate organic phosphorous (living
protoplasms and decaying organisms);
 soluble organic phosphorous (excretion and
decomposition).

80. ◦ As a nutrient, it renders vitality and sturdiness of
plants.
◦ It is used up in the form of phosphate (P2O5),
particularly aluminum phosphates (acid-forming),
iron phosphates (acid-forming), and calcium
phosphates (alkaline-forming).
◦ It is found the lowest level in soil and water
among the four major nutrients.

81.  Phosphorous is rarely found in high concentrations in
freshwaters and ranges from 0.005 to 0.020 mg/L.
 High concentrations of phosphates can indicate the
presence of pollution and are responsible for eutrophic
conditions.
 In majority of lakes, availability of phosphorous is the
limiting factor, which controls the rate at which plants
grow and therefore the productivity of the whole plant
community.
 Phosphorous is much more readily lost from an
ecosystem than nitrogen and carbon as it reacts with
mud and chemicals in water in ways that make it
unavailable for plants.

82.  Plants can absorb phosphorous only as dissolved
inorganic phosphorous, which is rapidly taken up
by algae and macrophytes.
 Bacteria in the sediments at the bottom of the lake
break down organic content of dead plants and
animals and phosphate is released into the water
in the spaces between the sediment particles.
 Oxygen acts as barrier in the release of
phosphate.

83.  from the atmosphere in the form of rain;
 from decayed plants and animals, and animal
manures;
 water inflow: surface runoffs, water supply, and
waste water from agricultural and municipal
waste water;
 from inorganic (chemical) fertilizers;
 from feeds.

84.  Potassium is found usually in the ionic form, its
concentration is low in natural water (less than 10
mg/L).
 Potassium salts are highly soluble.
 It is readily incorporated into mineral structures
and accumulated by aquatic biota, as it is an
essential nutrient.

85. ◦ As a plant nutrient, it is used up generally for fruiting
purposes in the case of plants that produce fruits and
perhaps for multiplication of cells or strands for non-
fruiting plants, like phytoplankters and certain algae.
◦ It is used up in the form of potash (K2O).
◦ It is not a limiting factor in plant production in ponds,
especially in seawater and brackishwater ponds where it
is found readily available and abundant. In other words, it
is not essentially required in such types of water.

86.  decayed plants and animals, and animal
manures
 inorganic (chemical) fertilizers

87.  Organic matter in freshwater arises from living
material (directly from photosynthesis or indirectly
from terrestrial organic matter) and as a
constituent of many waste materials and effluents.
 The total organic matter can be a useful indication
of pollution. In surface waters, concentration of
total organic carbon is less than 10 mg/L

88.  Chemical Oxygen Demand (COD) is a measure
of the oxygen equivalent of the organic matter in a
water sample that is susceptible to oxidation by
strong chemical oxidant such as dichromate.
 The concentration of COD in surface water ranges
from 20mg/L oxygen or less in unpolluted waters
to greater than 200 mg/L (in waters receiving
industrial effluents).

89.  Biochemical Oxygen Demand (BOD) is an
approximate measure of the biochemically
degradable organic matter present in the water
sample.
 It is defined as the amount of oxygen required for
aerobic microorganisms in the sample to oxidise
the organic matter to a stable inorganic form.
 Unpolluted water typically has BOD value of
2mg/L, but those receiving effluent may have
more than 10mg/L.

90.  Organic matter from flora and fauna makes a major
contribution to the natural quality of surface water, the
composition of which is extremely diverse.
 Natural organic matter is not toxic but exerts major
influence on biochemical and hydrochemical
processes in the water body.
 Humus is formed by biochemical and chemical
decomposition of vegetative residues and
microorganism activity. It enters directly from the soil
or is a result of biochemical transformations within the
lake.
 Humus is divided into humic and fulvic acids.
These concentrations are highly dependent on the
physical-geographical conditions and range from 10 to
100 g of carbon/litre.

91.  Plankton (Phytoplankton, zooplankton and
bacterioplankton) includes both the micro and macro
components that are at the mercy of the water current.
 Plants- primary producers which include:
◦ Emergent plants are rooted in the lake bottom, but their
leaves and stems extend out of the water
◦ Submergent plants have most of their structures below water.
Common examples are coontail and pond weeds.
◦ Floating plants- non-anchored plants that float freely in the
water or on the surface. Ex. Water hyacinth (water lily),
duckweeds
 Nekton – organisms that have the ability to swim
against the current. Ex. Fish, reptiles
 Benthos- organisms living on the lake bottom
◦ Epifauna- organisms living on the surface of the lake bottom
◦ Infauna- organisms living inside the lake substrate


92. THOSE THAT GO WHERE THEY CHOOSE
Fish Amphibians
Turtles
Larger Zooplankton
Insects
THOSE THAT GO WHERE THE WATER TAKES THEM
LIVING THINGS = PLANKTON
animals - zooplankton
algae - phytoplankton
bacteria - bacterioplankton
DEAD MATERIAL = DETRITUS
internal - produced within lake
external - washed in from watershed
THOSE THAT LIVE ON THE LAKE BOTTOM
BENTHOS = ANIMALS
aquatic insects
molluscs - clams, snails
other invertebrates -
worms, crayfish
PLANTS
higher plants -
macrophytes
attached algae -
periphyton
BACTERIA & FUNGI
sewage sludge
aufwuchs - mixture
of algae, fungi
and bacteria

93.  Megaplankton. > 20 cm
 Macroplankton. 2-20 cm
 Mesoplankton. 0.2 – 20 mm
 Microplankton. 20- 200m
 Nanoplankton. 2- 20 m
 Picoplankton. 0.2- 2 m
 Femtoplankton. 0.02- 0.2 m

94.  Holoplankton. Organisms that spend their entire
lives in the plankton.
 Meroplankton. Organisms that spend but a part
of their lives in the plankton

 Neuston. Small swimming organisms inhabiting
the surface water film (10 cm)
 Epineuston- aerial side
 Hyponeuston- aquatic side


95.  The biological communities within lakes may be organized
conceptually into food chains and food webs.
 The broad base of primary producers supports overlying
levels of herbivores (zooplankton), planktivores and much
smaller numbers of carnivores (predators).
 These individual trophic levels may be idealized as a food
chain, but in fact many organisms are omnivorous and not
necessarily characterized by a particular level.
 Consumers often shift levels throughout their life cycle. For
example, a larval fish may initially eat fine particulate
material that includes algae, bacteria and detritus. Then it
may switch and graze on larger zooplankton and ultimately
end up feeding on so called "forage fish" or even young
game fish (i.e., top predators) when it reaches maturity.


97.  Three main factors regulate the trophic state of
a lake
 Rate of nutrient supply
 Climate
 Shape of lake basin (morphometry)

98.  Rate of nutrient supply
 Bedrock geology of the watershed
 Soils
 Vegetation
 Human landuses and management

99.  Climate
 Amount of sunlight
 Temperature
 Hydrology (precipitation + lake basin turnover
time)

100.  Shape of lake basin (morphometry)
 Depth (maximum and mean)
 Volume and surface area
 Watershed to lake surface area ratio (Aw : Ao)


101.  Eutrophication is the process by which a body of
water becomes enriched in dissolved nutrients
(such as phosphates) that stimulate the growth of
aquatic plant life usually resulting in the depletion
of dissolved oxygen.




102.  Noxious algae (scums, blue-greens, taste and
odor, visual)
 Excessive macrophyte growth (loss of open water)
 Loss of clarity (secchi depth goes down)
 Possible loss of macrophytes (via light limitation
by algae and periphyton)
 Low dissolved oxygen (loss of habitat for fish and
fish food)
 Excessive organic matter production (smothering
eggs and bugs)

103.  Blue-green algae inedible by some zooplankton
(reduced food chain efficiency)
 "Toxic" gases (ammonia, H2S) in bottom water (more
loss of fish habitat)
 Possible toxins from some species of blue-green
algae
 Chemical treatment by lakeshore homeowners or
managers may
 Drinking water degradation from treatment disinfection
byproducts
 Carcinogens, such as chloroform (from increased
organic matter reacting with disinfectants like chlorine)

104.  Roots are anchored in the bottom bud. Ex: Spike rushes and
small sedges
 Narrow, tubular, linear leaves and have broad leaves. Ex.
Bulrushes, reeds, and cattails
 Poorly developed root system but highly developed aerating
system. Ex. Pond lily (Nuphar spp.) and Pond weed
(Potamegaton)
 Lacks cuticles. These plants absorb nutrients and gases directly
from the water through thin and finely dissected or ribbon like
leaves. Ex. Certain pond weed species (Chara muskgrass)
 Have compressed bodies that permit them to move with ease
through the masses of aquatic plants. Fishes lack strong lateral
muscles characteristics of fish living in swift water such as
sunfish.
 Carry a bubble of air with them when they go under water in
search of prey. Diving insects such as water boatman and Diving
beetles

105.  Spike rushes and small
sedges
Adaptation:
Roots are anchored in
the bottom bud.

106.  Bulrushes, reeds, and
cattails
Adaptation:
Narrow, tubular, linear
leaves and have broad
leaves

107.  Pond lily (Nuphar spp.)
and Pond weed
(Potamegaton)
Adaptation:
Poorly developed root
system but highly
developed aerating
system

108.  Certain pond weed
species (Chara
muskgrass)
Adaptation:
Lacks cuticles. These
plants absorb nutrients
and gases directly from
the water through thin and
finely dissected or ribbon
like leaves,

109.  Fishes Lack Strong Lateral
Muscles Characteristics Of
Fish Living In Swift Water
Such As Sunfish.
Adaptation:
Have Compressed Bodies
That Permit Them To Move
With Ease Through The
Masses Of Acquatic Plants.

110.  Diving Insects Such As
Water Boatman And
Diving Beetles
Adaptation:
Carry A Bubble Of Air
With Them When They
Go Under Water In
Search Of Prey.

111.  Urbanization. Reclamation of some portions of the
lake.
 Overfishing. Increased fishing pressure.
 Increased sewage effluents
 Introduction of exotic species accidentally or on
purpose
 Human activities like road construction, logging,
mining and agriculture affects the lake physical,
chemical and biological aspects.
