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Limnology is the study of inland waters.
This includes rivers, creeks, billabongs, ponds, pools, swamps, lakes, salt lakes and other wetlands.
The word limnology comes from the Greek word "limne", meaning marsh.


Florida Lake Watch Secchi Disk
 American Rivers


St. John's River 

Water Management District


 How Streams become Rivers


Aquatic Photos-animals



Aquatic & Invasive Plants

Invasive Plants 
Coloring Book (UF)

 University of Florida 

Aquatic Plant Database

Benthic Macroinvertebrates

Key to Aquatic Macroinvertebrates

University of Wisconsin



 US Army Corps of Engineers


 Lake Atlas

 Water Atlas

Biofilms & Biodiversity

Lake Data



 Lake Stratification

Water Fleas 


Measuring Biodiversity

Water Quality

Dissolved Oxygen

Nutrient Cycles



 Rivers & Springs

 Watershed Management

Limnologists study:

Groundwater/Surface Water Interaction
Oxygen Budgets
Sediment Mapping and Analysis


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Lake Origins


Lake Stratification


bulletAmictic - never mix.  Sealed totally  by ice.  Arctic Lakes, high Alpine Lakes.
bulletOligomictic- (few) rare circulation.  Usually tropical well above 4C all year.
bulletMonomictic- (one) mixes once a year.  Won't usually stratify.  Good example of Florida lakes.
bulletCold- never greater than 4C, ex. Canada
bulletWarm- never below 4C, subtropical, Florida
bulletPolymictic- (many)
bulletCold- near 4C, tropical, high altitude
bulletWarm- well above 4C, tropical, equatorial
bulletDimictic- (two) mixes twice a year, fall and spring overturn.  Above 4C and below 4C.
bulletHolomictic- (whole) entire column circulates from surface to bottom.
bulletMeromictic- never totally circulates, very deep, usually tectonic.
bulletMixolimnion- mixing layer
bulletChemocline- layer of increased salinity
bulletMonilimnion- very saline, never mixes
bulletEctogenic meromictic- external source of salt flowing into lake
bulletCrenogenic meromictic- submerged saline springs
bulletBiogenic meromictic- accumulation of salts due to sediments

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Temperate Lake Overturn
(Northern Lakes)


Temperature has a direct effect on living organisms in the lake system. Dissolved oxygen levels are directly related to temperature which in turn effects zooplankton and other aquatic life.

Lake Okeechobee

 ...located in Florida, second largest freshwater lake contained entirely within the lower
48 states of the U.S.

Great Lakes

The Laurentian Great Lakes of North America were formed 10,000 to 15,000 years ago and consist of five major lakes: Lakes Superior, Huron, Michigan, Erie, and Ontario.  This lake district contains more fresh water (greatest unfrozen mass) than any other in the world.

What's Polluting Lake Erie?

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Dissolved Oxygen

Dissolved oxygen is an essential indicator in assessing a water-body's health. Oxygen enters the water from the atmosphere and through aquatic plant and phytoplankton photosynthesis. The oxygen is then available for aquatic organisms to utilize in basic metabolic processes. Most plants and animals can grow and do well when the dissolved oxygen level exceeds 5 mg/l. A drop in the level to 3-5 mg/l causes organisms to become stressed. Levels below 3 mg/l causes death in many species. Oxygen is used up during the decomposition of organic material. An overload of nutrients from human activities cause overgrowth of phytoplankton. The phytoplankton ultimately die and fall to the bottom where they decompose, using up oxygen.

 Nitrogen & Phosphorus

The same nutrients - phosphorus (P) and nitrogen (N) that fertilize our lawns, also "fertilize" our river, lakes, ponds and streams. Our rivers, lakes, ponds and streams don't need fertilizing. In fact,  many area streams, lakes and ponds are grossly over-fertilized by nutrients, which come from storm water runoff and sewage treatment plant discharges. These excess nutrients cause aquatic plants and algae to grow over abundantly in the summer, a condition called eutrophication. This prolific plant and algal growth can ruin  waterways for boating, fishing and swimming.  The uncontrolled growth also harms fish and other aquatic life by changing the amount of dissolved oxygen in the water system.

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Floridan Aquifer

Florida has over 50,000 miles of rivers and streams, 7800 lakes, and 4000 square miles of estuaries, with an abundance of surface waters that are used for a variety of purposes.

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River & Stream Systems

A river system consists of a main channel and all of the tributaries that flow into it.  Within a river system, the surface of the ground slopes toward the network of tributaries, so the drainage system acts as a funneling mechanism for removing surface runoff and weathered rock debris.


tributary  a stream flowing into or joining a larger stream 
distributary any of the numerous stream branches into which a river divides where it reaches its delta 
upstream  moves toward headwater (up the regional slope of erosion) 
downstream moves toward mouth of river (delta)
delta  a large, roughly triangular body of sediment deposited at the mouth of a river
meander a broad, looping bend in a river 


1st order streams have no tributaries
2nd order streams are where two 1st order streams meet
3rd order streams are where two 2nd order streams meet
4th order streams are where two 3rd order streams meet

Length of stream > with order number, .5 relationship to slope


Florida has 17 to 27 springs (depending on the resource), many of which are 1st order.  Silver Springs, located in Marion County, is the largest 1st order spring in the United States, with a flow rate of
808 cubic feet per second.

Florida Springs

St. John's River flows north
273 miles, longest river in Florida

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Upper Clean Water Zone


Pollution Source


Zone of Degradation


Anaerobic Zone


Recovery Zone

Upper Recovery Zone


Lower Recovery Zone


Lower Clean Water Zone






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pH scale


A logarithmic scale for expressing the acidity or alkalinity of a solution.  A pH below 7 indicates an acid solution; pH above 7 indicates an alkaline solution.

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Chlorophyll bearing organisms which possess unicellular sex organs
or multi-cellular ones in which every cell forms a gamete.


Bluegreen algae is prokaryotic and the rest are eukaryotic


90% of oxygen in atmosphere is produced by algae


photosynthetic algae lack roots, steams and leaves


all algae contains chlorophyll a



Chlorophyll A, B, C, D



bullet Alpha-carotene
bullet Beta-carotene
bullet gamma-carotene
bullet epsilon-carotene



bullet lutein 
bullet violazanthin 
bullet fucoxanthin 
bullet neoxanthin 
bullet astaxanthin 
bullet diatoxanthin 
bullet diadinoxanthin 
bullet peridinin 
bullet dinoxanthin 
bullet ueraxanthin 
bullet antheraxanthin 
bullet mayxoxanthin 
bullet myxoxanthophyll 
bullet oscilloxanthin 
bullet echinenone 

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Rotifers     Crustaceans     Copepods

Zooplankton  important to larval fish are classified as either rotifers, cladocerans (water fleas) or copepods.


bulletPlankton - passively floating or weakly swimming animal or plant inhabiting open water in the ocean, lake, pond or stream
bulletZooplankton- animal component of plankton
bullet Phytoplankton- plant  component of plankton


life span 12 days

most common rotifer^

Rotifers are the first organism to invade water systems.

Epiphanes brachionus

The name "rotifer" is derived from the Latin word meaning "wheel-bearer"; this makes reference to the crown of cilia around the mouth of the rotifer. The rapid movement of the cilia in some species makes them appear to whirl like a wheel. The general body plan of a rotifer consists of four basic regions: head, neck, trunk (body), and the foot. In most species, the head carries a corona (crown) of cilia that draws a vortex of water into the mouth, which the rotifer sifts for food. The food itself is ground by the trophi (jaws), located just behind the mouth in the pharynx (throat). Trophi are found in almost all rotifers, and are characteristic organs of the phylum Rotifera. The shape of the trophi determines what these animals feed on and are also a typical  way of classifying them.  The body is telescopic, with a semi-flexible, extendible, transparent cuticle covering. The lorica is a scleratized chitineous skeleton, which gives the rotifer its permanent shape.  Interestingly,  rotifers pull their corona into the lorica during death/preservation causing it to be unseen. Within the body are the stomach and reproductive organs. The final region of the rotifer body is the foot; this foot ends in a "toe" containing a cement gland with which the rotifer may attach itself to objects in the water and sift food at its leisure.

As well as their morphology and feeding habits, reproduction in rotifers is rather unusual. Several types of reproduction have been observed in rotifers. Some species consist only of females that produce their daughters from unfertilized eggs, a type of reproduction called parthenogenesis (cloning of females). This means these parthenogenic species can develop from an unfertilized egg, asexually. Other species produce two kinds of eggs that develop by parthenogenesis: one kind forms females and the other kind develops into degenerate males that cannot even feed themselves (sexual dimorphism). These individuals copulate resulting in a fertilized egg developing within the rotifer. The males survive long enough to produce sperm that fertilize eggs, which then form resistant zygotes (resting eggs) that can survive if the local water supply should dry up. When conditions are right the eggs hatch in the water regenerating a new population.
Females carry one egg at a time.

life span 50 days

Cladocera - Water Flea


< 1/ 4 in

< 1/ 8 in 

< 1/ 16 in

< 1/ 16 in

Scientists are concerned that Daphnia lumholtzi may have negative effects on North American ecosystems. The large spines make it difficult for young fish (larval and juvenile stages) to consume this exotic. Native Daphnia have fewer, smaller spines  and, therefore, are more susceptible to fish predation. The protection from predation afforded by its spines may allow Daphnia lumholtzi to replace native Daphnia species. If this replacement occurs, the amount of food available to larval and juvenile fishes may be reduced. This could result in reduced survivorship of young sport and food fishes in lakes, rivers, and fish hatcheries where Daphnia lumholtzi becomes abundant.

life span 50 days

Cyclopoid copepodite

 mini-crustacean found in both fresh and sea water


There are two forms of Copepods. One kind swims freely and actively about, skipping in the water.
The second kind of Copepods are parasitic crustaceans. They attach themselves to other water creatures by digging into the flesh or scales and get their food by eating at the animals they are attached to.

Plankton Management for Fish Culture Ponds

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Aquatic Plants
(Native & Exotic to Florida)


Native Freshwater Plants


Invasive Nonnative

Reflecting on Lakes

Nutrients lead to high primary productivity, resulting in an algae laden hypereutrophic  system.  Hypereutrophic lakes are nearly impossible to repair, excess nutrients and their consequences (organic sediments, loss of habitat, organisms and wildlife) are seldom reverted to an oligotrophic condition.