THE STATE OF PONDS AND LAKES

INTRODUCTION

• Lakes and ponds are essential for life and humans rely on them
• Make up only 3% of the Earth's surface
• Limnology is the study of the interrelationships of organisms of inland waters

SIZE, FORMATION, AND SUCCESSION

• Lakes can be created by tectonic plates, glaciers, rivers, or humans
• Humans also create lentic habitats for lakes
• Ponds are the main type of land locked water
• Successional development- water body is gradually incorporated into
• terrestrial landscape

THERMAL STRATIFICATION

• Occurs when temperature is high and winds are low
• The water in a lake does not turn over
• Creates layers in the water: Epilimnion, metalimnion, hypolimnion
• Water concentration and temperature is higher near the top
• Inverse stratification can occur during the water

LIGHT TRANSMISSION

• Photic zone- light transmission >1%, photosynthesis occurs
• Aphotic zone- light transmission
• Water depth and water clarity determine light transmission

NUTRIENT INPUTS AND CYCLING

• Nitrogen, phosphorous, and carbon are the most important nutrients
• Oligotrophic means low nutrient supply and low primary productivity
• Eutrophic means high nutrient supply and high primary productivity
• Human activity increases the nutrient supply, but can lead to eutrophication

BIOTIC STRUCTURE: LAKE ZONES AND FOOD WEBS

• Littoral zone- near the shore with abundant light and plant matter
• Limnetic zone- open water where light can still penetrate
• Bottom sediment of the of the habitat

PRIMARY PRODUCERS

• Periphyton- grows on rocks, mud, and leaf litter and looks like a brown film
• Phytoplankton- algae suspended in the water column
• Macrophytes- most diverse and visible of the primary producers

CONSUMERS

• Examples- worms, snails, amphibians, insects, birds, crustaceans, and fish
• An important part of lentic systems is their interaction with terrestrial habitats
• Lentic systems create good food webs

PATTERNS IN SPECIES

• Increase in habitat size increases diversification
• Acidity, permanence, and predation pressure determine species richness
• Interaction like competition and predation determine community structure
• Abiotic factors and biotic factors both determine diversification and structure

THREATS TO LENTIC ECOSYSTEMS

• Habitat loss, eutrophication, acidification, chemical contamination, global warming, and exotic species
• Laws have been made to prevent too many nutrients from entering lentic systems
• It is difficult to present the introduction of exotic species