Focus Areas

Incentive Programs

Water Quality Primer

Well-Water Protection

Downloads

— Water- An Ecosystem Perspective —

An aquatic ecosystem is a group of interacting organisms dependent on one another and their water environment for nutrients (e.g., nitrogen and phosphorus) and shelter. Familiar examples are lakes and rivers, but aquatic ecosystems also include areas such as flood plain marshes, which are flooded with water for only parts of the year. Seemingly inhospitable aquatic ecosystems can sustain life.

Even a drop of water is an aquatic ecosystem, since it contains or can support living organisms. In fact, ecologists often study drops of water - taken from lakes and rivers - in the lab to understand how these larger aquatic ecosystems work.

Aquatic ecosystems usually contain a wide variety of life forms including bacteria, fungi, and protozoan; bottom-dwelling organisms such as insect larvae, snails, and worms; free-floating microscopic plants and animals known as plankton; large plants such as cattails, bulrushes, grasses, and reeds; and also fish, amphibians, reptiles, and birds.

The assemblages of these organisms vary from one ecosystem to another because the habitat conditions unique to each type of ecosystem tend to affect species distributions. For example, many rivers are relatively oxygen-rich and fast-flowing compared to lakes. The species adapted to these particular river conditions are rare or absent in the still waters of lakes and ponds.

Florida contains an abundance of freshwater (non-saline) ecosystems including lakes, ponds, rivers, streams, and wetlands.

A lake is a sizable water body surrounded by land and fed by rivers, springs or local precipitation. Florida has over 7,700 lakes with a surface area over 10 acres or more.

Ponds are smaller bodies of still water located in natural hollows. Ponds are found in most regions and may exist either seasonally or persist from year to year.
 
Rivers and streams are bodies of fresh, flowing water. The water runs permanently or seasonally within a natural channel into another body of water such as a lake, sea or ocean. Rivers and streams are generally more oxygenated than lakes or ponds, and they tend to contain organisms adapted to the swiftly moving waters. Some of the larger rivers in Florida include the Apalachicola, Chattahoochee, Choctawhatchee, St. Johns, Kissimmee (shown on right),  Peace and Suwannee rivers.

Some rivers flow into oceans, the great saltwater bodies that cover 70% of the earth's surface. The tidal areas where salt water and fresh water meet are called estuaries. These productive ecosystems on Florida's coasts are home unique species of tidal plants, wading birds, and shellfish among others.

Wetlands are characterized by three main components:

• Presence of water - water is either at or near the land surface for some time. Some wetlands are continually flooded while others may simply have saturated soils.

• Soil type - wetland soils are called hydric soils and have characteristics which indicate they are different from nearby upland soils.

• Vegetation type - wetland plants, called hydrophytes, are adapted to life in wet conditions. Cattails, bulrushes and sawgrass are familiar hydrophytes.

Florida's best known wetlands are the Everglades. Other wetlands are cypress ponds, strands, and prairies, river swamps, and flood plains, other forested freshwater wetlands, freshwater marshes, wet prairies, salt marshes, and mangrove swamps. All provide important benefits to people and the environment.

Wetlands are the largest component of the state's surface waters in terms of total area.  They occur near the ocean and gulf, adjacent to rivers and lakes, in areas of poor soil drainage, and in relict lake valleys or river channels. Prior to development, wetlands covered about half the state's area.  Over one third of the original wetlands have been drained for agriculture, flood control and residential development. Much of the remaining wetlands have been adversely affected by land use practices which have resulted in vegetation destruction, nutrient and toxic loading, sedimentation, and altered flow regimes. Click on the adjacent map to see a graphic image of the wetlands in Florida.

Wetlands are among Florida's most valuable and productive ecosystems.  They help regulate water levels within watersheds; improve water quality;  and reduce flood and storm damages. Wetlands provide a critical habitat for a wide range of plants and animals. (Nationwide, wetlands support one third of our endangered species even though wetlands comprise less than five percent of the landscape.) They provide "outdoor laboratories" for education and scientific research; and  support fishing, hunting, and other recreational activities.

Furthermore, scientists are beginning to realize that atmospheric maintenance may be an additional wetlands function. Wetlands store carbon within their plant communities and soil instead of  releasing it to the atmosphere as carbon dioxide. Thus wetlands help to moderate global climate conditions.

What kinds of animals use wetlands?

Every drop of water contains microscopic zooplankton which are a vital component of the food chain. The water's surface and the wetland bottom are covered with insect eggs, larvae and nymphs. Members of the fish, amphibian and reptile groups are all dependent on the habitat provided by wetlands. Numerous bird and mammal species make extensive use of the water and its adjacent shores.

Food and shelter are the primary requirements of life. Wetlands provide these functions for many species of animals that either live permanently within the wetland or visit periodically. Almost every part of a wetland, from the bottom up, is important to wildlife in some way.

Wetlands  provide great volumes of food that attract many animal species. Dead plant leaves and stems break down in the water to form small particles of organic material called "detritus."   This enriched material feeds many small aquatic insects, shellfish, and  small fish that are food for larger predatory fish, reptiles, amphibians, birds, and mammals.

Some insects use bottom debris to form a protective covering. Wetland vegetation provides nesting materials and support structures to several bird species and is a major source of food to mammals. Small mammals use the lush vegetation at the edge of wetlands for cover and as a source of food, and they themselves are food for birds of prey. Each species has adapted to using the wetland and its surrounding area in a particular way.

Energy from the sun is the driving force of an ecosystem. This light energy is captured by primary producers (mainly green plants and algae) and converted by a process called photosynthesis into chemical energy such as carbohydrates.

The chemical energy is then used by the plants to perform a variety of functions including the production of plant parts such as leaves, stems, and flowers. The raw materials used for this purpose are nutrients (e.g., nitrogen, phosphorus, oxygen, and calcium): substances necessary for the growth of all plants and animals.

Animals are incapable of photosynthesis. They therefore eat either plants, other animals, or dead tissue to obtain their energy and required nutrients. In ecosystems, the transfer of energy and nutrients from plants to animals occurs along pathways called food chains. The first link in a food chain consists of primary producers: green plants and other organisms capable of photosynthesis.

Plant-eating organisms, known as primary consumers, are the next link in the food chain. They, in turn, are eaten by secondary consumers: carnivores (flesh eaters) or omnivores (plant and animal eaters). Decomposers such as bacteria and fungi make up the final link in the food chain. They break down dead tissues and cells, providing nutrients for a new generation of producers.

Most organisms in an ecosystem have more than one food source (e.g., fish feed on both insects and plants) and therefore belong to more than one food chain. The consequent overlapping food chains make up food webs: complex phenomena with links that are constantly changing.

A toxic substance is one that can cause harm to the environment or human life. Most are synthetic and include PCBs, pesticides, dioxins, and furans.

Some toxic substances can enter a food web and be transferred through it. The uptake of any environmental substance by an organism is called bioconcentration. Although nutrients taken up through this process are usually converted into proteins or excreted as waste, many toxic compounds accumulate in the fat or certain organs (e.g., liver) of animals.

As contaminated organisms are eaten by others, the toxic substances are transferred up the levels in the food web and become more concentrated, sometimes to harmful levels. This process is called biomagnification The species at the top level of the food web, including humans, are often subjected to higher concentrations of toxic substances than those at the bottom. Toxic substances reaching harmful levels is one sign that the aquatic ecosystem is unhealthy.

Unhealthy aquatic ecosystems are those where human disturbances have impaired the natural functioning (e.g., nutrient cycling) or appreciably altered the structure (e.g., species composition) of the system.

These disturbances can be physical (e.g., injection of abnormally hot water into a stream), chemical (e.g., introduction of toxic wastes at concentrations harmful to the organisms) or biological. Introduction and propagation of non-native animal or plant species is one such example of biological disturbance. There are more than 900 exotic plant species in Florida, accounting for more than one-fourth of the total number of plant species found in the state. Most were introduced to Florida on purpose, as ornamental plants, while a handful were introduced accidentally.

Many of the characteristics that make a plant easy to grow and propagate are also characteristics of invasive plants. The lack of predators (insects, animals or fungi) has given many invasive exotic plants a huge advantage over native species.

The Florida Department of Environmental Protection has authority over the state's exotic aquatic plants. However, there is a gap in who has authority over invasive exotic plants in uplands and wetlands. There is also a basic gap in the understanding of each species' biology. Additionally, development of control options has lagged behind identification of new exotic plant species, while exotic plant problems have expanded faster than the financial resources available for their management.

Herbicides are the most cost-effective method and the main ammunition used to fight the war on weeds. It can cost $600 an acre to control hydrilla using Aquathol and Sonar. Because of their high cost and the fact that they work best in cooler water temperatures that are found in early spring when hydrilla is not growing, the herbacides are used sparingly. By using fairly low doses the hydrilla can be controlled without affecting beneficial native plants like pickerelweed and eel grass.

Compounds - like Reward, Diquat, Rodeo and 2-4-D - are used on cattails, water hyacinths and water lettuce.

Symptoms of poor ecosystem health include:

• The loss of species.

• The accelerated proliferation of organisms. One example is algae blooms caused by an excess of phosphorous and nitrogen compounds in the water. This condition is called eutrophication.

• Increased incidences of tumors or deformities in animals.

• A change in chemical properties. Perhaps one of the most significant has been a reduction of pH in water caused by acid rain.

• The presence of certain organisms which indicate unsanitary conditions. Coliform bacteria, for example, are a sign that the system may contain organisms that cause a variety of human diseases such as diarrhea, typhoid, and cholera.

Human health and many of our activities are dependent on the health of aquatic ecosystems. If the lake or river system is unhealthy, the water may be unsafe to drink or unsuitable for industry, agriculture, or recreation - even after treatment. Uses of aquatic ecosystems are impaired when these systems are unhealthy. For example:

• Inland and coastal commercial fisheries have been shut down due to fish or shellfish contamination or the loss of an important species from the system.

• The frequency of urban beach closures has escalated as a result of contamination by animal feces and medical waste.

• Navigation problems, caused by the rapid expansion of bottom-rooted aquatic plants, have increased for pleasure craft.

Perhaps, but it takes time and is dependent on the nature of the disturbance. The effects of dredging, for example, may last from one to several years, but many of the displaced organisms such as fish can reestablish themselves. In other cases, more severe disturbances (e.g., dam construction) may cause local extinction of already endangered species. These ecosystems are unlikely to recover naturally.

In many cases, mechanisms exist that allow us to help restore ecosystem health or minimize detrimental impacts caused by human use. Some of these mechanisms are:

• Environmental Legislation.

• Integrated Resource Planning: This approach ensures that relationships among land use, development, water flows, water quality, and aquatic ecosystems are considered prior to the land use designations for areas.

• Technology: Measures to improve the quality of waste discharges and to lower both water demands and effluent loadings are being implemented in response to environmental and water use concerns.

• Environmental Monitoring: Monitoring of chemicals in the water, sediment and organisms helps us to identify potential ecosystem problems and to track existing problems.

• Compensatory Measures: For example, a fish hatchery operation can produce young fish which a disturbed habitat can no longer supply.

Water and climate are intimately related. It is obvious, from a water resource perspective, how the climate of a region to a large extent determines the water supply in that region based on the precipitation available and on the evapotranspiration loss. Perhaps less obvious is the role of water in climate. Large water bodies, such as the oceans and large Lakes, have a moderating effect on the local climate because they act as a large source and sink for heat. Regions near these water bodies, like Florida, generally have milder winters and cooler summers than would be the case if the nearby water body did not exist.

Through the hydrologic cycle, water has a basic role in climate. The evapotranspiration of water into the atmosphere requires an enormous amount of energy which ultimately comes from the sun. When water vapor in the atmosphere condenses to precipitation, this energy is released into the atmosphere. Thus water acts as an energy transfer and storage medium for the climate system.

Most scientists now agree that it seems likely that  some degree of climate change will be with us and affect our lives over the course of the  next century.   While most scientists believe that man-made greenhouse gas emissions  are changing the climate, they are less sure about the details, particularly about the speed of the change or exactly when it will occur.

Because of the intimate relationship between climate and the hydrologic cycle, changes in the climatic regimes could directly affect the average annual water flow, its annual variability, seasonal distribution, and quality. Greater climatic variability would mean changing the frequency of extreme weather events and increased droughts and floods.

Florida, with its low coastlines -- especially in its populous southeast and western coasts -- and susceptibility to tropical storms and hurricanes, is  among the most vulnerable of U.S. states. Rising seas could mean the drowning of coral reefs, and other coastal ecosystems, such as mangrove swamps and coastal marshes, as  well as the intrusion of salt water into our drinking water aquifers.

A drought is a sustained and regionally extensive occurrence of appreciably below-average natural water availability, in the form of precipitation, stream-flow, or groundwater. Droughts are natural events which have occurred throughout history and may be considered as temporary features caused by fluctuations in the climate.

Flooding is almost always a natural occurrence. An exception would be flooding due to the collapse of a dam, of which there are very few in Florida. There are many conditions and variables that determine whether a lake or river over tops its banks or an ocean rises along its shores. Heavy rainfall itself can also cause floods. This is frequently the case in Florida where thunder storms are often very intense. Severe storms like hurricanes result in storm surges when sustained high winds from one direction push the water level up over beaches and sea walls. Flooding is worse if high tides occur at the same time.

The size, or magnitude, of a flood is described by a term called recurrence interval. By studying a long period of flow records for a stream, it is possible to estimate the size of a flood that would, for example, have a 5-year recurrence interval (called a 5-year flood). A year flood is one that would occur, on the average, once every five years. Although a 100-year flood is expected to happen only once in a century, there is a 1 percent chance that a flood of that size could happen during any year.

Flood plains are lands bordering rivers and streams that normally are dry but are covered with water during floods. Buildings or other structures placed in flood plains can be damaged by floods. They also can change the pattern of water flow and increase flooding and flood damage on adjacent property by blocking the flow of water and increasing the width, depth, or velocity of flood waters.