Lakes and Ponds
Chapter 12
Conditions in Lakes and Ponds
Cons:
• oxygen is limited
• the deeper you go, the darker it gets
Pros:
• lack of water not a problem
• temperatures change slowly and not
as much as in air
Conditions in Lakes and Ponds
A productive lake will have plants growing on
the bottom, a diverse assemblage of small
invertebrates, and a good variety of fish
species
Conditions in Lakes and Ponds
Wild, productive lakes have different zones,
based on depth and distance from shore
1. Shoreline – greatest diversity (wetland)
2. Light, open-water zone – submerged plants
3. Dark zone – bacteria and fungi feed on
dead organic matter; a few fish live here
Conditions in Lakes and Ponds
Benthos – the lake bottom, and the organisms
that live there
Microorganisms, worms, mollusks, crustaceans,
insect larvae
A vital part of a healthy lake
Diversity of Florida Lakes
Lake, Orange, Polk,
and Osceola county
contain more than a
third of Florida’s
lakes
Diversity of Florida Lakes
Florida’s lakes vary in their characteristics:
• alkaline or acid
• rich or poor in nutrients
• clear or colored (usually a “tea color”)
• bottom may be sand, silt, clay or organic
• streams may run in or out, or neither
• may always hold water, or just seasonally
Diversity of Florida Lakes
Four lake types we will discuss:
1.
2.
3.
4.
Clay-hill lakes
Sandhill lakes
Swamp lake or Basin swamp
Flatlands lakes
Diversity of Florida Lakes
Clay-Hill Lakes
A depression lake on a bed of clay; the water
cannot seep down through the clay
Water comes mostly from rain and runoff, and
is lost by evaporation
Diversity of Florida Lakes
Sandhill Lakes
A depression in sand with an organic layer on
the bottom that keeps water from draining
down
Water may come from rain or from groundwater
seepage (sideways)
Diversity of Florida Lakes
Sandhill Lakes
Shallow, sunny, with acidic water and a sandy
bottom
Important for insects, amphibians, and wading
birds
Diversity of Florida Lakes
Swamp lakes / Basin swamps
Very shady shoreline, acidic water, not very
productive
“Blackwater lakes”
Diversity of Florida Lakes
Flatlands lakes
Open water within flatwood or prairie wetlands
Many emergent plants
Lake Okeechobee
Diversity of Florida Lakes
Flatlands lakes
Cypress domes and donuts
• in small, shallow depressions
• tallest trees in center
Seasonal Changes in Florida Lakes
The area and depth of a lake changes over time
• from season to season
• over decades or centuries
• depends mainly on rainfall
Seasonal Changes in Florida Lakes
As a lake gets deeper or more shallow, it
strongly affects life on the shoreline.
As a lake gets deeper, it expands, and terrestrial
plants on the shore will die while emergent
plants move in.
Seasonal Changes in Florida Lakes
If a lake dries up, the muck that has
accumulated on the bottom will oxidize and
disappear
• fires may burn
• new seeds can sprout
• underwater life will go dormant
Seasonal Changes in Florida Lakes
Wet/dry cycling is good for a lake – keeps it from
completely filling in with muck, so water stays
clearer and oxygen-rich
Because there’s not much (or any) flow through
most FL lakes, what runs into a lake will stay
there indefinitely
- pollutants can be a problem
Seasonal Changes in Florida Lakes
Eutrophication – when excess nutrients (N and
P) run off into a lake
1. Algae take advantage and grow rapidly
(algal bloom)
2. As algae die, decomposing bacteria feed
on them and use up oxygen
3. Water becomes oxygen-poor and murky:
fish and submerged plants die
Plants and Animals in Florida Lakes
A lake isn’t just about the organisms that can be
seen – there is a diversity of microscopic
organisms
These are the basis of a lake’s food web
Plants and Animals in Florida Lakes
Lakes are important to visiting animals as well
• water birds visit to catch prey
• birds and mammals stop by to get a drink
• often, FL lakes are stopping places for
migratory birds: ducks, pelicans, cranes
Bald eagle
Haliaeetus
leucocephalus
White pelicans
Alligator
Alligator mississippiensis
Human Use of Florida Lakes
Lakes have high recreational value, and are
considered a desirable “view”
Large lakes moderate the local climate
Provide a reservoir of water for domestic or
agricultural use