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.Clay-hill lakes 2.Sandhill lakes 3.Swamp lake or Basin swamp 4.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