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Invasive introduced species
You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Skip to content. Share this: Facebook Twitter. Like this: Like Loading Next Freshwater Wetlands. Leave a Reply Cancel reply Enter your comment here Plants need oxygen and carbon dioxide to live. Aquatic plants have a more difficult time getting these because the gases dissolve more slowly in water than in air.
Aquatic vegetation needs light to photosynthesize, but light can be blocked by an aquatic plant canopy or by sediments in the water. The aquatic environment has advantages over terrestrial biomes. A biome is a region characterized by similar climate, soil, plants, and animals. Anyone who swims is aware of the buoyancy of water. Aquatic plants need less support tissue as a result, saving energy that can be used for other plant functions. In terrestrial plants, nutrient absorption occurs primarily through the roots. However, in submersed plants, the leaves can act as roots by absorbing nutrients.
Where Aquatic Plants Live The following allegory helps explain in symbolic terms the complexity of aquatic plant systems. A young ecologist thought he found a way to decipher the coral reef. He believed that all he needed to do was feed the data about reefs into a huge supercomputer, type a few commands, push the Enter key, and out would come the secrets of life on the reef. He gave it a whirl. Presented with such an impossible task, the supercomputer had blown up. These complexities are not limited to coral reefs, however.
For as little as is understood about the reefs, even more is left to discover about other aquatic environments. The obvious distinction when it comes to aquatic vegetation is whether the environment is freshwater or marine salt water. A variety of habitats exist within salt and fresh waters. Oceans The evolution of life began in the sea. All living creatures need water. Plants made the move to land by re-creating their wet environment and sealing it within themselves.
Water is vital to life and where there is more water, plant life tends to flourish. It comes as no surprise then that the ocean rivals the rain forests in terms of biological diversity. The deep sea, 3, feet 1, meters and more beneath the surface of the ocean, was previously thought to be lifeless, only to be discovered to be so rich with biological diversity that now it is referred to as an unexplored continent. Dredging of this ocean floor in the s revealed swarms of worms, crustaceans, mollusks, and other animals found nowhere else on Earth. At the sea bottom alone, there is no way of knowing the total number of species, but estimates for animal species range in the tens of millions.
The diversity of bacteria and other microorganisms cannot even be guessed to order of magnitude. A pelagic habitat consists of plants and animals that float or drift free in the open sea. The other two marine biomes are benthic, where organisms crawl, creep, burrow, or attach themselves to the ocean bottom or to each other. Benthic plants must live where the water is shallow so that they can receive light and therefore photosynthesize Figure 1. Although this term may be a mouthful, it is easy to understand if you know the meaning of each of the terms. Balanoid refers to barnacles.
Thallophyte refers to plants that absorb their food over a growing surface, such as a rocky shore. The balanoid-thallophyte habitat can be easily observed. Have you ever seen what looks like foamy bathtub rings along the coastline? These are intertidal zones where the water line varies between high and low tides. Barnacles and seaweeds are common in this habitat, as well as brightly colored lichen that appear above the water zone and are tolerant of occasional mists of salt water.
The pelecypod-annelid biome consists of unconsolidated sediments. Pelecypod refers to animals that have a shell, such as a clam. Annelid refers to animals that have a segmented body, such as a leech. Unconsolidated sediments are soft grounds with varying textures depending on particle size and are then classified as sand, silt, or clay. Many of the organisms that live here are burrowers, such as worms.
Temperature is another factor that affects the distribution of species. Temperature variations alter species and force change and competition in their environment. Similar to lakes and ponds, there is a seasonal changeover in oceans where the warmer top layer of the ocean mixes with the much colder bottom layer.
A zone of steeply decreasing temperature called a thermocline separates the extreme Figure 1. This species-rich system contains a variety of life-forms from floating plankton to benthic creatures burrowing deep in the ocean floor sediment. Autumn causes the top layer of water to cool and become heavier, and then the surface and bottom layers begin to mix; the thermocline breaks and the extreme temperature contrast is reduced.
Nutrients are brought to the surface and provide a food source for zooplankton tiny animals that drift with the ocean currents , fish, birds, and on up the food chain. Coming quickly into view is the captivating, stark contrast of blue waters set against green vegetation. During the s, before there were many regulations in New Jersey to prevent their destruction, coastal wetlands were disappearing at an astonishing rate. Private and public monies were raised to purchase the land and build the educational center.
A nationally threatened bird of prey, the osprey, returns from its wintering grounds to this area in late March to nest and raise its young. Osprey populations are recovering and growing since the ban of DDT an insecticide that persisted in the environment that nearly decimated their populations. The Wetlands Institute is also home to marsh plants, fiddler crabs, great blue herons, and perhaps most proudly, diamondback terrapins, a large species of aquatic turtle. Without the forwardthinking efforts to preserve these acres back in the s, surely this land would have been lost to more casinos and condos that now dominate this area of the New Jersey shore.
Wetlands are the transition environment from land to water. The term refers to marshes, bogs, swamps, and fens. Despite the name, wetlands are not necessarily wet year round; some are What Are Aquatic and Wetland Plants? Marshes are wetlands dominated by soft-stemmed vegetation. The salt marshes of New Jersey are vast grassy meadows that protect the mainland from flooding, filter sediments and pollutants from the water, and serve as a nursery for many fish and shellfish.
Most of the local animals served as seafood in New Jersey spend at least some of the time living in a salt marsh. Swamps are another type of wetland comprised primarily of woody plants. Bogs are freshwater wetlands, often formed in old glacial lakes, characterized by spongy peat deposits, evergreen trees and shrubs, and a floor covered by a thick carpet of sphagnum moss Figure 1. Fens are freshwater, peat-forming wetlands covered mostly by grasses, sedges, reeds, and wildflowers. Wetlands are biologically rich with plants and animals.
They also provide valuable resting and feeding ground Figure 1. Wetlands are biologically rich and act as a purifier of water. These habitats play a vital role in our environment by providing food, shelter, and breeding grounds for many creatures. Degradation of wetlands has been a leading cause of species extinction. At the Wetlands Institute, salt ponds are shallow depressions in the marsh that are flooded only by high tides, not by the ordinary twice-daily tides.
The floor of the salt pond is a thick Protecting Our Wetlands Despite the ecological value of wetlands, the United States loses approximately 60, acres of wetlands per year. Although wetlands purify water, pollutants can destroy a wetland. In Florida, the sugarcane industry has been held responsible for polluting and destroying wetlands in the Everglades. Invasive species, both animals and plants, have also been a cause of destruction of wetlands. State and federal agencies have implemented policies to protect wetlands.
One way to protect these lands is to monitor the discharge of pollutants through the issue of permits for residential development, roads, and levees, all of which affect wetlands. Some states will fine polluters of wetlands and require them to compensate for it. As compensation for the damage to the wetlands, El Paso must purchase and preserve wetland acres. Agencies also protect wetlands by prohibiting building on them. Businesses must apply for permits to build, and in many states, alternatives are explored so that construction does not take place on these valuable ecosystems.
What Are Aquatic and Wetland Plants? These decaying organic materials are a food source for grass shrimp, killifish, and minnows.
Few organisms can live here because of the fluctuating salinity levels. Evaporation causes high salt levels whereas flooding and rainwater reduce salinity. Individuals can help protect and restore wetlands. Duck stamps sold in your local post office support the U. When gardening, be aware of possible wetlands; plant native grasses or forested buffer strips along wetlands. Create Your Own Wetland If you already have a wet area in your backyard, creating a wetland may be as simple as selecting wetland plants.
If not, choose a natural depression in your backyard with ideally clay soils that will drain slowly. If you have a natural depression but it is never wet, you may need to get a plastic or other type of liner. If the area is still too dry, you will need to build a berm a mound or wall of earth to hold back water.
Wetlands are also a great purifier of water by absorbing excess nutrients, sediment, and other pollutants before they reach rivers, lakes, and other water bodies. When rivers overflow, wetlands absorb and slow floodwaters. Lakes, Ponds, and Reservoirs Lakes, ponds, and reservoirs are freshwater. Reservoirs are manmade and, often, so are ponds. Beavers also create ponds by damming streams. Ponds are shallower than lakes and generally allow light to penetrate the entire depth of the water. Plant life is able to live on the bottom of a pond whereas the bottom of a lake is generally unable to support photosynthesizing plants.
In ponds, an ample supply of algae colors the water a healthy dark green. Pond life such as snails, crustaceans, worms, and tadpoles graze on the algae and decaying plant material. Zooplankton feed on algae, bacteria, and other small particles of organic matter. Tiny plantlike organisms, called phytoplankton, greenblue algae, and diatoms are the energy-producing tenants in a lake. Deeper lakes will have more phytoplankton and a greater likelihood of native fish. Although light does not penetrate the entire depth of the lake, species occupy all areas of a lake.
In the mucky, dark sediment at the bottom, bloodworms and phantom midge larvae the young of a tiny fly feed on falling organic matter. These organisms enrich and stabilize the sediment and help break down bits of plant material not digestible by other animals. The littoral zone is where aquatic, rooted plants grow along a shore or lake Figure 1.
It is the area between the highest and lowest tides, also known as the intertidal area. The vegetation in this zone behaves similarly to the vegetation in a pond because What Are Aquatic and Wetland Plants? The water is shallow enough for light to penetrate; light is needed by the plants to photosynthesize. Seen here is a littoral zone along the western U. On a lagoon with salt flats, they find laminated, brightly striped sediments underlain by gelatinous mud.
These mat-forming algae exist where the sea meets and teases the land. Enchanted, Margulis puts her hands in the mud of fragrant microbial tissues and whiffs the exchanging gases. The smell is akin to rotten eggs. What she smells is death—decaying organic matter—yet the community of algae is very much alive.
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Algae consist of three general forms: microscopic, mat-forming, and stonewort. Microscopic algae are typically free floating or attach to rocks and other solid materials in the water. Mat-forming algae are generally considered undesirable because they can become difficult to control once their populations reach high levels. Stonewort algae have simple stem and leaflike structures with a portion embedded in the sediment. Often they become overly abundant in shallow parts of water. Algae are an important source of oxygen and a primary food source for many aquatic invertebrate animals, such as shellfish.
Problems from algae occur when a population crashes or dies off, the light is able to penetrate the depth of the zone and therefore support plant life. For oceans, the littoral zone is categorized in more detail. The four transitional zones are the spray zone, high tide zone, middle tide zone, and low tide zone. Algae are chlorophyll-containing organisms, often grouped together in colonies. Algae have been around for more than 2 billion years, and we are still discovering new kinds.
Although algae photosynthesize, they are not in the same taxonomic category as plants, that is, Plantae; rather, they are considered protists. Green algae are the most diverse group of all the algae with more than 7, species. Algae include pond scums, terrestrial algae, snow algae seaweeds, and freshwater and marine phytoplankton.
Unlike plants, algae do not have true leaves or roots. Some algae use other compounds to store energy. Red algae store energy in the form of floridean starch, and brown algae store energy in the form of laminarin. Since photosynthesis occurs only with the green pigment chlorophyll, this brings into question how these other algae can make their own food when they are not green. They do actually contain the green pigment of chlorophyll but just in smaller amounts that are masked by the red and brown pigments.
Algae do not flower or produce seeds; instead they produce spores for reproduction. These spores are very small, often only one cell, and they are mobile. This zone is only wet during extremely high tides or flooding. Cattails, barnacles, and lichen can be found in the spray zone. The high tide zone is flooded during high tide. Floating-leaved plants such as water lilies frequently occupy this zone. The middle tide zone is covered and uncovered by water daily.
The low tide zone or lower littoral is the deepest part of the water where submersed 20 Invasive Aquatic and Wetland Plants plants can still grow. This area is exposed only when the tide is extremely low. As a pond or lake ages, the littoral zone increases. Like most other natural systems, a lake or pond goes through transitional changes over time. This is referred to as succession. Succession is the gradual replacement of one set of plant species with another. Succession begins with species that are the first to arrive at an available site and grow relatively quickly without ample nutrients.
These species that are first to arrive, usually after a disturbance such as fire, flood, or volcanic eruption, are known as pioneer species. Pioneer species alter the environment and make it suitable for the next set of species; they add organic matter, provide shade, and create a varied habitat. As an ecosystem ages, it eventually stops switching out species. This final plant community is known as a climax community and indicates a more mature ecosystem.
Ponds and lakes change until they reach a climax community, resulting in a larger littoral zone. The Role of Aquatic and Wetland Plants Aquatic and wetland plants provide shelter and food for animals and add oxygen to the water. People rely on the biological richness of aquatic and wetland habitats. We rely on food and other resources from these biological communities or ecosystems. Many other organisms can only survive with plants for food. Animals, microbes microorganisms , invertebrates animals without backbones , and plants interact and are dependent on their environment.
The term ecosystem is used to describe this interdependence where communities of different organisms share and recycle resources needed for maintenance of the community. Aquatic and wetland plants have the fortune of ample access to water, and What Are Aquatic and Wetland Plants? They are typical of the kinds of plants that occupy the high tide zone. It is surprising how much wildlife food is produced in an acre of wetland. In an experiment, scientists found that a plant known as the salt-marsh bulrush, important to overwintering birds in South Carolina, produced an average of about pounds of seeds per acre per year.
Seeds are an important source of nutrition for animals but specifically for overwintering birds. Some wetland plants produce as much as pounds of seeds per acre. Floating-Leaved Plants Just as the words suggest, these plants have leaves floating on the surface of the water. They are rooted in a lake bottom and occupy those lakes that do not dry out.
Water lilies Nymphaea spp. Rhizomes are modified stems that spread horizontally underground. They are often referred to informally as creeping roots, but although they resemble roots, rhizomes are really underground stems. Some floating-leaved plants can exist completely underwater for days or even months. Floating-leaved plants live simultaneously in two habitats: water on the bottom and air on the top. A thick, waxy substance protects the leaves from the air.
Wind and waves can be a problem to these plants so they typically grow in sheltered areas. Emergent Plants Emergent plants are rooted in sediment, but the tops of the plants extend into the air. These plants grow in soils that are periodically inundated with water or are submersed. The erect, narrow-leaved sedges and rushes are in this group. Grasses, sedges, and rushes are critical to the diet of many waterfowl such as ducks and geese.
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These plants are not restricted to the diets of birds alone; deer, rabbits, moose, cattle, alligators, beavers, and boar all consume these wetland plants. The emergent plants face the challenge of being able to sustain the force of even subtly moving water. These plants must have strong root systems and much energy is put into creating this strong structure.
Submersed Plants Submersed plants are completely underwater. Mosses Fontinalis spp. Most plants get carbon dioxide from the air where it is relatively plentiful; submersed species must get carbon dioxide from the water where it is less readily available. One of the benefits of being fully submersed is that these plants do not need to put as much energy into creating support tissue. These plants must obtain all of the nutrients they need from the water. Wind and waves tend to relocate them so they often end up in bays. The deeper the water, the less likely a plant will be able to receive the light it needs.
Light is the limiting factor in determining the depth at which water plants will grow. A heavy sediment load as the result of runoff or erosion can reduce the amount of light that reaches below the water surface, which is why sediments are a concern in aquatic environments. The more sediment-filled a lake or pond is, the less aquatic life will be in it even if the water is relatively shallow.
Other influences of water clarity are phytoplankton and organic particles; the lower each of these are, the more clear the water is. As water clarity decreases, plant life is reduced and the littoral zone decreases. Boats, shoreline or riverbank erosion, and burrowing animals such as carp can increase suspended sediment.
In an ecosystem, these nutrients are recycled throughout the system. The nonmineral nutrients are hydrogen H , oxygen O , and carbon C. Nonmineral nutrients are found in the air and water, while mineral nutrients are found in the soil. Nutrients that plants need in large quantities are referred to as macronutrients, and those they need in small amounts are called micronutrients. Plants need the following macronutrients: nitrogen N , phosphorus P , and potassium K. Most rooted aquatic plants get phosphorus and potassium from sediments since the open seas have relatively low concentrations of these elements.
For aquatic plants, limited nutrients, particularly nitrogen and phosphorus, will limit how much the plant will grow. Aquatic and wetland plants need smaller amounts of secondary nutrients: calcium Ca , magnesium Mg , and sulfur S. In even smaller quantities they need micronutrients: iron Fe , manganese Mn , zinc Zn , borine B , copper Cu , and molybdenum Mo. These nutrients are found in the sediments of aquatic environments.
Aquatic and wetland plants get their nutrients differently depending on how they grow. Rooted emergent plants get their nutrients from sediments. Emergent floating plants get their nutrients from the water. Submersed rooted plants get their nutrients from the sediments that the roots are in, as well as through the water column. A creature floating on the water surface or burrowing in the sediment is not in the water column. Submersed floating plants only get their nutrients from the water column.
Nutrients and aquatic environments are in a delicate balance. Nutrient-rich lakes are more productive than nutrient-poor ones. Productivity is measured by the amount of biotic life. When an overabundance of nutrients is present in water bodies, algae and aquatic weeds will grow to the point that they will compete for oxygen and space in the water.
Oxygen is an important component in all bodies of water for biotic communities. Biotic communities consist of all of the living organisms in a specified area. All these organisms have a demand for oxygen. Fertilizers from farms and lawns can contribute to these nutrient-rich waters. This is known as eutrophication. Fertilizers are high in nutrients, and although they are valuable when the appropriate amounts are applied to desirable vegetation or crops, fertilizers in water are pollutants.
Failing septic tanks can also create eutrophication because the waste products are high in organic matter. The more polluted a section of water, the more microorganisms and aquatic life compete for the oxygen in the water. High levels of pollution, even in the form of nutrients can cause fish to suffocate from lack of oxygen. Other manmade activities that lead to eutrophication are factory effluents, domestic waste discharges, feed lot runoff, and construction site erosion.
Dead fish floating on the top of a body of water are one sign of nutrient-rich waters. Many state agencies monitor surface waters for an overabundance of nutrients. Procedures that will minimize an adverse impact to the water supply are required of activities that result in a discharge of nutrients. Businesses or individuals that fail to comply can be fined.
Point source pollution consists of chemicals that enter directly into a body of water. A pipe pouring wastewater directly into a stream is point source pollution. Nonpoint source pollution is when pollutants reach a body of water after passing through or over another medium. The runoff that goes into a creek from a driveway with puddles of antifreeze and oil would be nonpoint source pollution. A malfunctioning septic system would be nonpoint source pollution. Water pollutants include any chemical or substance that degrades the quality of water for drinking.
Salt and other deicers that get thrown on the road and sidewalks during the winter are sources of nonpoint source pollution. Obvious pollutants are pesticides, fertilizers, oil, and grease, but even sediment is considered a pollutant. Changes in the pattern of water flow can occur from engineering projects such as reservoirs and stream channelization. Changing the natural flow of a body of water increases sediment deposits, which in turn adversely affects aquatic life. Sediments are soil particles, and they may carry chemical pollutants and nutrients with them into the water.
The suspended soil particles in the water may reduce light needed for photosynthesis by plant life and clog the gills of fish. Nutrients in a lake are the result of management practices, watershed influences, and direct human-caused nutrient additions, such as fertilizer runoff. Ponds tend to be more nutrient rich than rivers, and therefore ponds support a greater diversity of aquatic life. The reason is that ponds move more slowly, although biological 28 Invasive Aquatic and Wetland Plants diversity of aquatic life is a reflection of water depth, sediment type, and geology.
Just as terrestrial plants are affected by the pH of their soils, aquatic species composition is determined in part by water pH and water quality. Pollution can reduce the quality of water and therefore plant life. Neutral or alkaline water generally supports the best plant growth in ponds; shallow depth will allow in light. High concentrations of soluble iron can limit the availability of phosphorus. Excessive organic matter often contains high levels of organic acids that are toxic to aquatic vegetation.
Aquatic vegetation attempts to temper these toxins by releasing oxygen from its roots. This eliminates the condition where a lack of oxygen creates toxic substances. Common cattail Typha latifolia is a wetland plant capable of producing oxygen by its roots to counteract the difficulties of growing in an anaerobic environment. With this knowledge, scientists are able to choose plants like cattail to grow in a polluted wetland where most plants would have difficulty thriving.
Oxygen Terrestrial plants exchange gases that they need, such as carbon dioxide and oxygen, through openings in the leaves known as stomates. The oxygen then diffuses to the lower parts of the plant. Their invasion threatens native ecosystems or commercial, agricultural, or recreational activities dependent on these ecosystems. They may even harm the health of humans. Invasive species are generally not native; they are usually from another country or region.
Other terms used to describe invasive species are invaders, nonnatives, exotics, invasives, and nuisance species. These terms will be used interchangeably. Organisms in a new environment are not a new problem. Humans traveling across the Atlantic Ocean have assisted with this invasion for centuries. Many of these invasives entered the United States back in the s. In some cases they were purposefully introduced because benefit was perceived in their introduction, such as being easy to grow or having a pretty flower. This travel transformed the existing plant and animal species.
A hundred years ago people did not realize the kind Figure 2. Stomates are openings in the leaves. Leaves that are underwater have aerenchyma instead of stomates. This photograph depicts the air passages found in the tissue of aquatic plants that enable plant roots to grow underwater. Scientists have compared the movement of these exotic plants, animals, and microbes to a game of biological roulette. Once in a new environment, the organism might die or it might take hold and became an ecological bully by stealing nourishment and habitat from native species. Today we see the dwindling of native species caused by these invaders.
Introductions are accelerating due to travel, trade, and tourism. Whereas oceans and unscalable mountains kept animals from entering terrain where they did not belong, trade and travel have bridged any geographic barrier. A plane can take you from Philadelphia to sub-Saharan Africa. If an animal finds its way into the cargo area of a plane, it could travel thousands of miles within a day. The barriers that nature has instituted can be overcome in a day. Invasive species are a problem because they are outstanding competitors.
All creatures evolve toward becoming a better competitor. Changes occur based on the requirements of their environment. On a large scale, this drama unfolds, like much of human history, as a succession of dynasties. Organisms possessing common ancestry rise to dominance, expand their geographic ranges, and split into multiple species.
Those species that do not adapt and change retreat into obscurity; their populations become smaller, more compromised, and eventually extinct. All biological creatures have an innate desire to perpetuate their species. As such, clever competition is crucial. Clever Competition Environments are ever-changing. Even a desert can have a day of freezing rain. And how is a plant to cope? Purple loosestrife The Natural World of Aquatic and Wetland Plants 31 Lythrum salicaria possesses the ability to make physical changes in response to its immediate environment Figure 2.
This is not necessarily a permanent, genetic variation like mutation or adaptation but a temporary change during the life cycle of the individual plant. Changes usually consist of variation in the type and placement of new organs. One type of structural change is to elongate leaf shape to adjust to decreased levels of light.
Phenotypic plasticity is the term describing this variation between individual plants of the same species but growing in different environments. Some scientists prefer to think of phenotypic plasticity as plants expressing behavior. However, it is important to note that plants have the capability to use internal states and external cues to be more competitive in their environment. Considering the obvious advantages of phenotypic plasticity, it is no surprise that invasive plants use this trait in their repertoire of adapting to small variations in the environment or microenvironments.
Purple loosestrife develops aerenchyma as additional parts of the plant are submerged in water. As mentioned, aerenchyma are intracellular spaces between underwater stems and leaves that supply oxygen to the plant. There are limits to the benefits of phenotypic plasticity. Variations could result in a switch in competitive advantage and 32 Invasive Aquatic and Wetland Plants Figure 2.
This invasive plant readily adapts to its environment, making it highly competitive and able to displace native plants. The Natural World of Aquatic and Wetland Plants 33 a zonation of species with different growth forms along gradients of water depth in lakes.
Emergent species respond to their environment, specifically the water level, by growing longer stems or other support structures. Emergent species generally outcompete floating and submerged species. As the water in a lake or pond gets deeper however, the emergent species must produce much support tissue. Eventually floatingleaved species such as water lilies get the competitive edge because they are supported by buoyancy; they are not forced to grow more structures as water depth fluctuates.
This is not the end of the story however. Floating-leaved species such as these are then replaced by submerged species with short petioles. Growing from cut pieces of root is one method of propagating vegetatively. Many aquatic and wetland weeds are adapted to fragment easily so that they can be dispersed. Plant Adaptations Adaptations enable plants to compete more effectively. One of the most remarkable adaptations in the aquatic plant world is the carnivorous behavior of the bladderwort Utricularia sp.
Tiny traps or bladders on the leaves catch very small organisms such as paramecia. This adaptation allows the bladderwort to get nutrients from the paramecia that it would not be able to get from the water. Salt water is corrosive to most plants. Plants in these marine environments must find ways to resist the corrosive nature of salt.
Adjacent to the river are thatch palms and majestic mangroves with tentacle-like roots rising in grandeur and resembling pipe organs. An American crocodile peeks its head out of the slowmoving water and barely notices the tourists in the small boat on the river. River safari trips traverse 6 miles 9.
While tourists snorkel in the coral reefs of northern Jamaica, the ecological treasure of the mangroves is diminishing. Mangroves are a haven for fish and other wildlife; they protect the shoreline and purify the water by removing pollutants. Their sturdy roots that enable them to withstand constant contact with water are also the source of their demise. In Jamaica, mangroves are disappearing because their value is little recognized and conservation efforts are relatively recent.
Mangroves make an excellent source of wood and charcoal in a country where fire is the only source of fuel for many people. The destruction of the mangroves threatens the fishing industry that the people also rely on. Conservation efforts to preserve the remaining mangroves have focused on educating Jamaicans about the importance of these ecosystems. In tropical locations in Florida, Panama, Australia, and Bermuda, turtle grass Thalassia testudinum is a sea grass that masters the adaptation of resistance to salt water in the shallow, sandy areas just off shore.
Only the adult straplike leaves can resist the corrosive nature of salt. Turtle grass protects the young leaves by growing a protective, cushiony sheath over them. Pushing on the The Natural World of Aquatic and Wetland Plants 35 sheath shows the resilience of this package and the water that is contained within it. The water contained within the sheath is not the salt water that the grass is in but freshwater that the plant has desalinated. When the leaf has matured enough to develop a resistance to salt water, it grows out of the protective sheath and another shoot is left behind.
Mangroves are another type of plant living in salt water that must deal with the problem of salt in the environment Figure 2. Mangroves are woody plants living in brackish waters of tropical and subtropical regions between the sea and land in areas inundated by tides. Brackish waters are where freshwater and salt water mix. Mangroves provide a habitat for fish and protect shores from harsh waves. Without salt-excreting mechanisms, the roots Figure 2. Mangroves are a vital part of the aquatic ecosystem, serving as a haven for fish and protecting the shoreline from harsh waves.
In many countries, mangroves are being lost because of their value as firewood. Pictured above is a black mangrove swamp in Texas. Salt that enters the system is quickly excreted by salt glands on the leaves. These glands are some of the most effective salt-excreting systems known in the natural world, and a lick of the mangrove leaves will show how salty they can get. Mangroves also filter out the salt at the root level. A third method that mangroves use to get rid of salt is to concentrate it in the bark or older leaves that will soon fall from the plant.
Another clever adaptation of the mangrove is having its roots above water to get oxygen.
Little oxygen is available in fine, often waterlogged mud. Roots grow upward above the mud, giving them access to oxygen yet keeping the plant properly supported. Lenticels, or special breathing cells, cover the roots and draw in air. The number of lenticels changes along the root structure as more oxygen is available. More oxygen availability means more lenticels, and vice versa.
How plants Reproduce Plants reproduce by seeds, spores, or vegetative parts. Plants that live for one growing season, called annuals, generally produce large numbers of seeds. Biennials are plants that complete their life cycle in two growing seasons and reproduce by both seeds and roots. Perennials live for more than two growing seasons, with some long-lived herbaceous perennials living decades, such as Canada thistle Cirsium arvense. Perennials generally focus energy into significant root growth, although there are exceptions such as purple loosestrife, which is a prolific seed-producing perennial.
Vegetative Reproduction Root segments or pieces that contain a node can reproduce to form a new plant. Root segments are cut by farming equipment, boat propellers, gardening tools, and any other tool that is used where plants exist and can segment a root. Shoots or suckers are consumed, pass through migratory waterfowl, and are spread to new sites. People dumping the water in home aquariums into streams, creeks, ponds, and lakes are also another source of invasive plant introductions. Boats moving from one body of water to another also spread invasive aquatic plants.
The propellers are perfect for entangling plants. When boaters dock, very few take the time to clean their boats. Many state natural resource agencies are educating boaters about how to properly clean their boats to prevent spreading invasive aquatic plants. Figure 2. The daisy left is one of many thousands of species of flowering plants.
Ferns right are gymnosperms. Gymnosperms do not flower; they produce spores to reproduce sexually. Not all plants are flowering, however; some plants produce spores for reproduction and these plants are classified as gymnosperms Figure 2. Pine trees are one example of a plant that bears spores in cones. Aquatic plants have unique ways of reproducing to ensure the perpetuation of their species. Coontail Ceratophyllum demersum has developed structures referred to as winter buds.
The winter bud is a dense mass of foliage produced on the top portion of the plant that contains an embryo plant. This bud is also packed with food reserves for the embryo plant since it will need these reserves for early growth. As the winter bud develops in the fall, it detaches from the parent plant and sinks to the bottom.
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In spring, it will form a new plant. O ne of the dangers of invasive aquatic and wetland plants is that their populations increase exponentially each year without any constraints, which alters fragile ecosystems. Wetlands can become so clogged by the overgrowth of invasive plant species that native birds will no longer make the wetland their home. Invasive plant species threaten the supply of freshwater.
Aquatic invasive species all species, not just plants continue to arrive in the Great Lakes at a rate of one every eight months, adding to the more than species already causing serious ecological and economic damage. One of the most notorious invasive species in the Great Lakes is the zebra mussel Dreissena polymorpha. The zebra mussel is a 1-inch-long 2. Each invasive species has the potential to have disastrous results on aquatic systems.
As these invaders found their way into other environments, the organisms that keep their populations in control were left behind. A predator is the animal that eats the other. Prey is the animal that the predator is eating. Predators and prey in action have been depicted on nature shows on television, for instance, where the cheetah outruns and eats the gazelle.
Although not quite as dramatic, insects and plants have predator-prey relationships as well. Predators and prey evolve together and occur naturally in the environment. The predator encourages the fittest of the prey species. The prey will try to avoid being eaten and will therefore develop characteristics to prevent death. The prey may evolve to be faster if the predator is a chasing animal.
The prey may also develop a better sense of smell, sight, or camouflage.
Identification and Sustainable Management
Characteristics that the prey possesses that do not enable it to escape the predator would not be improved or refined. Similarly, characteristics of predators that enable them to catch their prey, like claws, sharp teeth, and keen eyesight, would be developed over time. Possessing the ability to be transported around the globe presents the possibility of ending up in places never intended by nature. What makes some aquatic and Wetland Plants Invasive? Invasive species lack predators, and this enables them to keep expanding their populations.
In this photograph, an insect prey rests on the jaw-like leaf of a Venus flytrap predator. Flooding can cause a new invasive aquatic or wetland plant invasion but it can also be used to control invasives. Flooding is a type of disturbance, just as plowing, fire, or any other practice that disrupts the soil profile and denudes the surface of vegetation.
Invasive plant species love disturbance because it provides an opportunity of establishment. Flooding is a natural function of a river system. Spring flooding introduces nutrients into the soil surrounding the root system of riverbank trees, such as cottonwoods.
Human influences, however, have altered natural systems, and flooding occurs on an unnatural timetable in many places. Flooding, however, clearly affords the opportunity for invasive plant species to become easily established. In addition, the seeds of many invasive aquatic and wetland plants float, and flooding can help disperse seeds great distances.
If the force of the flood is truly strong enough, fragmented roots of biennials and perennials can also be sent miles downstream. Flooding has also been used to a limited extent to control aquatic and wetland invasive plants. In water bodies where the level can be regulated, weeds can be submerged.
The ship unloads the rice at a port in the Mediterranean and must take up millions of gallons of water to maintain its weight and therefore stability in transport. The ship then crosses the Atlantic Ocean and enters the Great Lakes to pick up wheat for transport to a receiving port. The water that the ship took up to maintain stability, referred to as ballast water, is no longer needed when cargo is put on the ship.
This ballast water is dumped in the Great Lakes, where nonnative organisms are introduced into a foreign environment. Species that are native to one port are suddenly the outsiders in another port thousands of miles away. Scientists estimate that as many as 3, alien species per day are transported in ships around the world. These organisms range from microscopic plants and animals to crabs, mussels, and even schools of fish. Some of these nonnatives can even cause human disease. Vibrio cholerae is a bacterium that causes a severe diarrheal disease called Asiatic cholera or epidemic cholera.
This bacterium is one of the most common organisms in surface waters. It was introduced to Asia likely through shipping. Scientists have isolated this organism in ballast water of cargo ships from the Gulf of Mexico. Cholera has been referred to in literature dating back to Ancient Greece, and has been associated with numerous epidemics after being introduced into a new location. No single management technique has proven successful in killing or removing all organisms in ballast water.
Selecting a treatment method depends on the structural integrity of the ship and its size, the expense of method, amount of potential 44 Invasive Aquatic and Wetland Plants damage to the environment, safety of the crew, and ease for port authorities to monitor compliance. One option is open sea exchange. In the above example, instead of the ship discharging in the Great Lakes, it would empty the ballast water in the open sea, the Atlantic Ocean in this case, and then fill the ballast tank with ocean water.
This method works because coastal organisms are unlikely to be able to survive in the open sea. The option has the appeal of being easily monitored since a simple salinity test would be able to detect whether the ballast water is seawater or freshwater. Open sea exchange is not safe, however, when the seas are stormy or rough. Another limitation is that sediments and residual water are difficult to remove from the ballast tank. Biocides can also be used to treat ballast water by killing organisms. One concern is for the health of the crew handling these chemicals.
Another concern is the potential of corroding the ballast tank. No easy solution to this major pathway of biological invasions exists. Research continues for techniques to treat ballast water without jeopardizing the safety of crew members. Hull Fouling Sea ballast water accidentally carries organisms inside the ship, whereas hull fouling carries organisms outside the ship where they attach to the hull. Organisms such as barnacles, mussels, sea squirts, sponges, and algae are able to attach to the hull and be transported long distances.
Once they arrive in a new port, they can create new exotic populations by releasing their larvae immature offspring or attaching to another structure in the port. Hull fouling What makes some aquatic and Wetland Plants Invasive? As shipping increases, it becomes vitally important to incorporate these preventative measures to prevent an exotic species explosion.
The Effects on Native Organisms Native organisms have evolved with natural predators and disease. Predators and disease control their populations. The unfair advantage that nonnative plants have is usually too great for native populations. Without intervention to remove nonnative invasive plants, native plants will generally become displaced, eventually to the point of complete exclusion. In aquatic and wetland communities, organisms that rely on native plants will be adversely affected. Fish will no longer have a food source; birds will have to go elsewhere for nesting sites, and often, the invasive plant grows so thickly that animals cannot physically access or navigate the water.
Invasive aquatic and wetland plants compete for sunlight, nutrients, and water. Generally, they are more aggressive than their native counterparts at acquiring these resources and taking the available resources, leaving little for native plants. The result is a shift from a biologically diverse plant community to a monoculture of one invasive species. Clogging Waterways Invasive species are notorious for rapid growth. Not only does this rapid growth suck up large amounts of resources, including water, the undesirable vegetation inhibits waterways. Turbines, dams, canals, and ditches become choked with weeds; removal is often costly.
Without consistent removal, waterways would be brought to a standstill and their function would be rendered useless. When it comes to habitat preservation, linking natural areas is best. If you had a total of ten acres to preserve, it would be best to have ten acres all in the same location, not ten one-acre parcels.
Creating small parcels of protected areas is the ecological equivalent to creating islands where species are more isolated than those living on a vast land mass. Geographic isolation reduces gene flow between populations, and the resulting gene pool is isolated, less diverse, and smaller.
With animals, as a gene pool becomes more and more narrow, inbreeding will occur, which reduces genetic diversity and weakens the species. Colonization is when species occupy a region that was previously not part of their range. Colonization increases biological diversity, assuming the new species is not an invasive plant, animal, or microbe.
When populations are diverse and natural systems are functioning properly, species will become more fit, change over time, or evolve. Preserved land that is larger in size generally has greater species diversity and gene flow between populations. Most important, new plant or animal populations will become genetically divergent from their parent population due to natural selection and mutation.
Habitat fragmentation adversely affects animal and plant populations. Once a habitat has been fragmented, there is not much that can be done to restore a species. Because of this, preserving land should focus more on creating corridors rather than islands of preservation. Invasive Wetland Plants W etlands are highly productive systems. The availability of water enables the system to maintain this high level of productivity by providing food and shelter for a variety of organisms.
As with any ecosystem, interaction among species and recycling of nutrients within the system is critical. An aggressive outsider, such as purple loosestrife, giant reed, reed canarygrass, or giant hogweed, just to name a few, can interrupt these interactions to the extent that the wetland is not performing to its potential any longer.
Butterflies extract nectar from purple coneflower Echinacea ssp. Behind the Joppa Flats Education Center, Gerome, their resident green heron, has again taken up its roost in the restored marsh behind the building. Fish and Wildlife Agency. Staff members identify and dig out invasive plants that threaten these wetland ecosystems.