Lake ecosystem : Physical factors affecting lake ecology

This presentation briefs the factors (physical) that may influence the lake ecology.

1. PHYSICAL AND
CHEMIOCAL
PROPERTIES OF LAKE
DR. SURJYA KUMAR SAIKIA
DEPARTMENT OF ZOOLOGY
VISVA-BHARATI

2. PHYSICAL PROPERTIES
TEMPERATURE
LIGHT
DEPTH
TURBIDITY
DISSOLVED SOLIDS

3. Lakes are extremely variable in their physical, chemical and
biological characteristics.
Physical (level of light, temperature andwater
currents)
Chemical ( nutrients, major ionsand
contaminants)
Biological( biomass, population numbers and growth)
MAJOR FACTORS INFLUENCY LAKE BIOLOGY

6. PHYSICALFEATURES
TEMPERATURE
WATERCONDITIONS
DEPTH
LIGHT
TURBIDITYAND
COLOUR

7. Primary role of light
-Plankton production –photosynthesis
(day)
-Respiration(night)
-Metabolism of the lake –controls the
ecosystem

8. Depending on light, lake is divided into two zones

9. Autochthonous -energy
stored inphotosynthetically
formed organic matter and
synthesisedwithin the lake or
stream Allochthonous-energy stored
in photosyntheticallyformed
organicmatter within drainage
basin and brought to the lake
or stream in various forms

10. ◦Latitude
◦Season
◦Angle of contact of light rays at watersurface
◦Time of theday
◦Degree of cloudiness or clearness of the sky, presenceof
fog, smoke, dust or other atmosphericconditions.
◦Dissolved ions –diminish light absorption. Traces of
ammonia, proteins and nitrates in solution stillreduce
transparency of water to Ultravioletlight
◦Suspended materials –composed of organic orinorganic
materials. They screen out the light (ex. Phytoplankton,
clay particles and abioticmaterials)
◦Presence of ice or snow cover –more light isreflected
Factor affecting penetration of light

11. 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 columnthat
light can penetrate, the deeper
photosynthesis canoccur.
Photosynthetic organisms include
algae suspended in the water
(phytoplankton), algae attached to
surfaces (periphyton), and
vascular aquatic plants
(macrophytes).

12. Waterismostdenseat4°Candbecomesless
denseatbothhigherandlowertemperatures.
Becauseofthisdensity-temperature
relationship,manylakesintemperateclimates
tendtostratify,thatis,theyseparateinto
distinctlayers

13. Thermal Stratification –the presence of
different temperatures in a body ofwater

14. Stratification of water in a natural water body(lake).
Formation of horizontal water current and shearing plane in upper portion (epilimnion) isshown
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m

15. www.esf.edu

17. Turbidity
•Turbidity is a condition of water resulting
from the presence of suspendedmatters
•(1) Settling suspendedmatters
•(2) Non-settling suspendedmatters

18. Secchidisc, a metal painted black and white as shown attached to
graduated chainfor lowering in thewater

19. Colours
of Lake
Blue water-water with
normal constituents
Simple.Wikimedia.org
Bright-green –water over
algae-covereddepression
en.Wikipedia.org
Yellow -due to clayey
turbidity as well as also water
overlying a clean sandyarea
Brown -abundance ofdiatoms
sightseeingtoursaustralia.com.au
Green-due to algal bloom
studio711.com
Reddish-browncolour
of blooms of
dinoflagellate
Greaterkashmir.com