Limnology is the study of inland waters.
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.
...located in Florida, second largest
freshwater lake contained entirely within the lower
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.
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.
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.
1st order streams have no tributaries
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
St. John's River
Chlorophyll bearing organisms which possess
unicellular sex organs
Chlorophyll A, B, C, D
Zooplankton important to larval fish are classified as either rotifers, cladocerans (water fleas) or copepods.
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.
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.
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.
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.