Lakes and Ponds
Lakes and ponds are inland bodies of standing or slowly
moving water. Although lakes and ponds cover only 2 percent of the world's land
surface, they contain most of the world's fresh water. Individual lakes and
ponds range in area from a few square meters to thousands of square kilometers.
In general, ponds are smaller than lakes, though regional idiosyncrasies of
naming abound—Henry David Thoreau's famous Walden Pond in Massachusetts has a surface
area of 64 acres. Lakes and ponds are an important source of fresh water for
human consumption and are inhabited by a diverse suite of organisms.
Physical Features
Light and temperature are two key physical features of lakes
and ponds. Light from the sun is absorbed, scattered, and reflected as it
passes through Earth's atmosphere, the water's surface, and the water. The
quantity and quality of light reaching the surface of a lake or pond depends on
a variety of factors, including time of day, season, latitude, and weather. The
quality and quantity of light passing through lake or pond water is affected by
properties of the water, including the amount of particulates (such as algae)
and the concentration of dissolved compounds. (For example, dissolved organic carbon
controls how far ultraviolet wavelengths of light penetrate into the water.)
Light and wind combine to affect water temperature in lakes
and ponds. Most lakes undergo a process called thermal stratification, which
creates three distinct zones of water temperature. In summer, the water in the
shallowest layer (called the epilimnion) is warm, whereas the water in the
deepest layer (called the hypolimnion) is cold. The middle layer, the
metalimnion, is a region of rapid temperature change. In winter, the pattern of
thermal stratification is reversed such that the epilimnion is colder than the
hypolimnion. In many lakes, thermal stratification breaks down each fall and
spring when rapidly changing air temperatures and wind cause mixing. However,
not all lakes follow this general pattern. Some lakes mix only once a year and
others mix continuously.
The chemistry of lakes and ponds is controlled by a
combination of physical, geological, and biological processes. The key chemical
characteristics of lakes and ponds are dissolved oxygen concentration, nutrient concentration,
and pH . In lakes and
ponds, sources of oxygen include diffusion at the water surface, mixing of
oxygen-rich surface waters to deeper depths, and photosynthesis. Oxygen is lost
from lakes and ponds during respiration by living organisms and because of
chemical processes that bind oxygen. The two most important nutrients in lakes
and ponds are nitrogen and
phosphorus. The abundance of algae in most lakes and ponds is limited by
phosphorus availability, whereas nitrogen and iron are the limiting nutrients
in the ocean. The acidity of water, measured as pH, reflects the concentration
of hydrogen ions . The pH value
of most lakes and ponds falls between 4 and 9 (the pH value of distilled water
is 7). Some aquatic organisms are adversely affected by low pH conditions
caused by volcanic action, acid-releasing vegetation surrounding bog lakes, and
acid rain.
Water color
Green Water
All bodies of water go through what we call an "algae
bloom" that will turn the water green. It’s a very natural occurrence that
happens whenever the water heats up and there is enough "fuel" in the
water to feed the algae. Mother Nature has her way of clearing the water. One
day, after weeks of not being able to see your fish (much less the bottom of
the pond), you may walk out and find that your pond is clear. The following is
a list of things that you can do to help Mother Nature do her job.
Algae, like most plants, need sunlight to
survive. Most of us can’t move our pond to the shade, but there are ways to
simulate shade. There are products available that color your water blue, such
as Pond Shade. You can also create shade for your sunny pond by adding floating
plants such as water hyacinths, water lettuce and waterlillies.
Water plants, especially floaters and
anacharis, compete with algae for nutrients in the water. The more plants you
have, the more the algae starves and reproduces less. Stock up with plants. You
may not want to use fertilizer in your plants until your ecological balance has
been met.
Do not scrub the sides of your pond. The green coat that
forms on the liner and on the sides and the bottom of the pond is beneficial to
the pond itself. The jelly-like substance is algae that is packed with
nitrifying bacteria. Nitrifying bacteria is paramount in order to limit the
Ammonia levels in the pond. If you want to give your pond a thorough cleaning,
start with the bottom of the pond, where parasites and bad bacteria usually
forms.
Green
Tip:
Grow your own vegetables. This will help to reduces carbon
from fertilizers, and transportation.
White
Water
If your water is a white, milky color or cloudy you are
probably experiencing a bacterial bloom.
Nature Clear is a perfect remedy for this
situation. It is important that you dose the water correctly and have plenty or
aeration (if you have fish) because the coagulation that occurs (after Natural
Clear is applied) will consume a great amount of the water’s dissolved oxygen.
Brown
Water
Brown water indicates that there is floating dirt and
particles in the water. Rotting leaves and debris create "tanning" of
the water. There are three things that you can do to clear the brown water.
Don’t wash all the filter material with
chlorinated water. Instead, take the least dirty pads and wash them with water
from your pond (this keeps the good bacteria alive).
Applying the Natural Clear pond treatment
can help. It binds minute particles in your water together and forces it to the
bottom of the pond. Again, follow precautions and make sure that your system is
highly aerated during the process. If in doubt, we have aeration equipment that
you can rent for this reason.
Now you should be able to see the bottom
of the pond and all the debris and trash you never knew existed. One of the
ponder’s best tools is a shop vac or wet vac. Use it to vacuum the bottom and
sides of the pond. Don’t scrub the slime off the sides. It’s beneficial to your
eco-system.
Wetlands
A wetland is an ecological community that is inundated
either year around or seasonally. There are very different properties of
freshwater versus saline wetlands. Numerous national, state and provincial agencies have
regulatory interests wetlands A chief intent of this article is to
provide the reader with special interest in wetland delineation, wetland
mitigation and wetland biology with insight to additional sources that will be
useful.
Wetland phenomenology
Wetland
phenomenology is partially defined by
plants and animals in residence, but abiotic
factors are also crucial in depicting the entirety of the habitat.. Birds and
vegetation, for example, are some of the most recognizable, distinguishable
features in a wetland landscape, and many researchers focus on the
identification of such birds and plants. The Audubon Society uses the U.S. Fish
and Wildlife Service definition in The Audubon Society Nature Guides “Wetlands”
by William A. Niering.
The
gross elements of wetlands include surface water, as well as shallow aquifers.
Surface water must be present for sufficient lengths of time that the area is
dominated by hydric soils and
organisms that are sustained by and
physiologically adapted to such saturated and/or inundated conditions.
Therefore, seasonal or
vernal pools are also considered wetlands.
Hydrology largely determines how the soil develops and the types of plant and
animal communities. Wetlands may support species ranging from obligate aquatic
to obligate terrestrial.
When
the upper part of the soil is saturated with water at growing season
temperatures,
soil organisms may consume the
oxygen in the soil and cause anaerobic
conditions unsuitable for most plants. Such conditions also cause the
development of
soil characteristics (such as color and
texture) of so-called
hydric soils. The plants that grow in such conditions,
such as marsh grasses, are called
hydrophytes. Together, hydric soils and hydrophytes
provide clues that a wetland area is present.
The presence of water by ponding,
flooding, or soil saturation is not always a good indicator of wetlands. Except
for wetlands flooded by ocean tides, the amount of water present in wetlands
fluctuates as a result of rainfall patterns, snow melt, dry seasons and longer
droughts.
Some of the most well-known wetlands,
such as the Everglades and Mississippi bottomland hardwood swamps, may have
periods of dryness. In contrast, many upland areas are very wet during and
shortly after wet weather. Such natural fluctuations must be considered when
identifying areas subject to government regulation. Similarly, the effects of
upstream dams, drainage ditches, dikes, irrigation, and other modifications
must also be considered.
Types
of wetlands
Wetlands
vary widely because of regional and local differences in soils,
topography, climate,
hydrology, water chemistry, vegetation, and other factors, including human
disturbance. Indeed, wetlands are found from the tundra to the tropics and on
every continent except
Antarctica.
Two general categories of wetlands are recognized: coastal or tidal wetlands
and inland or non-tidal wetlands.
Tidal
(coastal) marshes occur along coastlines and are influenced by tides and often
by freshwater from runoff, rivers, or
groundwater.
Salt marshes are the most prevalent types of tidal marshes and are
characterized by salt tolerant plants such as smooth cordgrass, saltgrass, and
glasswort. Salt marshes have one of the highest rates of primary productivity
associated with wetland ecosystems because of the inflow of nutrients and
organics from surface and/or tidal water. Tidal freshwater marshes are located
upstream of estuaries. Tides influence water levels. The lack of salt stress
allows a greater diversity of plants to thrive. Cattail, wild rice, pickleweed,
and arrowhead are common and support a large and diverse range of bird and fish
species, among other
wildlife.
Inland
wetlands are most common on floodplains along rivers and streams (riparian
wetlands), in isolated depressions surrounded by dry land (e.g., playas,
basins, and "potholes"), along the margins of lakes and ponds, and in
other low-lying areas where the groundwater intercepts the
soil surface or where precipitation
sufficiently saturates the soil (e.g., vernal pools and bogs). Inland wetlands
include marshes and wet meadows dominated by herbaceous plants, swamps
dominated by shrubs, and
wooded swamps dominated by trees.
Many
of these wetlands are seasonal (they are dry one or more seasons every year),
and, particularly in the arid and semiarid western United States, may be wet
only periodically. The quantity of water present and the timing of its presence
in part determine the functions of a wetland and its role in the environment.
Even wetlands that appear dry at times for significant parts of the year—such
as vernal pools—often provide critical
habitat for wildlife adapted to breeding
exclusively in these areas; in fact, biodiversity and occurrence rare and
restricted range biota is highly correlated with presence of western
USA vernal pools.
Wetland
categories
Inland
wetlands found in the United States fall into five broad categories—marshes,
swamps, bogs, vernal pools and
fens. Marshes are wetlands
dominated by soft-stemmed vegetation, while swamps have mostly 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.
Fens are freshwater peat-forming wetlands
covered mostly by grasses, sedges, reeds, and wildflowers. Vernal pools are
wetlands not subject to permanent inundation and having clearly hydric soils.
Ecological
roles of wetlands
Wetlands
are among the most productive ecosystems in the world, comparable to
rainforests and coral reefs. An immense
biodiversity of species of microbes, plants,
insects, amphibians, reptiles, birds, fish, and
mammals can be part of a wetland ecosystem.
Physical and chemical features such as climate,
topography, geology, and
the movement and abundance of water determine the plants and animals that
inhabit each wetland. The complex, dynamic relationships among the
organisms inhabiting the wetland environment are
referred to as food chains.
Wetlands
can be thought of as "biological supermarkets." They provide great
volumes of food that attract many animal species. These animals use wetlands
for part of or all of their life-cycle. Dead plant leaves and stems break down
in the water to form small particles of organic material called detritus. This
enriched material feeds many aquatic insects, shellfish, and small fish that
are food for larger predatory fish, reptiles, amphibians, birds and mammals.
The
functions of a wetland and the values of these functions to human society
depend on a complex set of relationships between the wetland and the other
ecosystems in the
watershed. A
watershed is a geographic area in which water, sediments, and dissolved
materials drain from higher elevations to a common low-lying outlet or basin a
point on a larger stream, lake, underlying
aquifer, or
estuary.
Water
Quality and Hydrology
Wetlands
have important filtering capabilities for intercepting
surface water runoff from
higher dry land before the runoff reaches open water. As the runoff water
passes through, the wetlands retain excess nutrients and some pollutants, and
reduce sediment that would clog waterways and affect fish and amphibian egg
development. In performing this filtering function, wetlands save us a great
deal of money. For example, a 1990 study showed that without the Congaree
Bottomland Hardwood Swamp in South Carolina, the area would need a US $5
million
wastewater treatment plant.
In
addition to improving water quality through filtering, some wetlands maintain
stream flow during dry periods, and many replenish
groundwater.
Many Americans depend on groundwater for drinking.
Running
Water
On
the continents, aquatic ecosystems are of two
kinds: lotic ecosystems, in which the water is free-flowing (streams and
rivers), and lentic ecosystems, in which the water is relatively stationary.
The scientists who specialize in aquatic ecosystems are limnologists.
Physical
Features
The limiting factors that govern what organisms can live in
lotic ecosystems include current, light intensity, temperature, pH ,
dissolved oxygen, salinity, and nutrient availability—variables routinely measured by
limnologists to develop a profile of the environment. These conditions differ
greatly between small headwater streams and the mouths of such great rivers
such as the Mississippi and the Amazon. Living occupants of streams and rivers
show corresponding differences along the way.
Small headwater streams, where water first collects by
runoff from the land or emerges from springs, are called first-order streams.
When two first-order streams meet, they form a second-order stream; two of
these converge to form a third-order stream, and so on, until the water may
flow into bodies as large as twelfth-order rivers (for example, the Columbia
and the Mississippi). Bodies of the first to third order are usually considered
streams, and those of the fourth order and larger are considered rivers.
Streams provide diverse habitats including relatively swift
rapids and quiet pools. They often have hard substrates of
stones, rubble, or bedrock to which animals can cling. Flat rocks and rubble
typically harbor the greatest species diversity of stream animals. Stream
animals often have flat, streamlined bodies that are not easily swept away by
currents, and hooks, suckers, or sticky undersides for clinging to substrates.
They tend to face into a current and swim against it, behavior called
rheotaxis. Lake animals,
Estuaries
Estuaries are partially enclosed bodies of water that occur
where the land meets the ocean. The world's largest estuaries are at the ocean
ends of rivers that deliver freshwater from surrounding and sometimes remote
upland areas. Estuaries may be configured as sounds, bays, lagoons, or networks
of tidal creeks and marshes. Many estuaries are separated from the ocean by
barrier islands and do not have major sources of freshwater inflow. Estuaries
are more common on coasts with wide and shallow continental
shelves than on coasts close to tectonic
plate boundaries.
Estuaries are physically and chemically dynamic and
complex ecosystems . Annual, seasonal, and daily fluctuations
in freshwater input, tidal inundation, temperature, wind, and other hydrological and meteorological factors are responsible for the highly changeable
character of estuaries. Due to variations in tidal height, currents, wave
exposure, sediment types, salinity, and depth within estuaries, many
different types of submerged and intertidal habitats exist. The diversity and
interrelatedness of habitats contributes to the biological richness of
estuaries.
Temperate and tropical estuaries are among the most
biologically productive ecosystems on Earth. Salt marshes dominated by Spartina grasses
can produce 5 to 10 tons of organic matter per acre per year,
which is more than most agricultural crops. In tropical estuaries, mangroves
are the dominant producers. Submerged seagrass beds, macroalgae
("seaweeds"), and phytoplankton also produce organic
material that supports abundant and diverse populations of animals. Direct
consumption of estuarine plants is important, but many small estuarine animals
process decomposing plant material and associated microbes known as detritus.
Rich populations of invertebrates living in the sediments and water provide
food for shrimps, crabs, fishes, birds, and mammals.
Estuaries support large commercial and recreational
fisheries. Crabs, clams, oysters, herrings, drums, striped bass, and other
harvested species reproduce and grow within estuaries and rivers. In addition,
major fishery species such as shrimps, flounders, mullets, and menhaden, which
spawn in the ocean, rely on estuaries as nurseries for juveniles. At least 70
percent of the species harvested in the United States requires a period of
estuarine residency
to complete their life cycles. Adult fish,
marine mammal, and bird migrations are often timed to coincide with best
conditions for reproduction and feeding in estuaries.
Coastal areas, especially estuaries, have always attracted
and supported human populations. About 40 percent of the world's population
lives within 60 miles of the coast, and 22 of the 32 largest cities are located
on estuaries. Human impacts associated with agricultural, industrial, and
residential development in coastal watersheds have resulted in changes in
freshwater inflow, increases in nutrients, and the destruction of wetlands.
Dredging, diversion, and damming have also altered estuarine habitats.
Reductions in water and habitat quality and overharvesting have reduced
resources and changed biological communities.
Healthy estuaries help to regulate flooding and decompose
contaminants. Increasing awareness of impacts and advances in scientific
knowledge and technology have led to some success in reducing impacts and
restoring water quality. Education and long-term planning are keys to achieving
a balance between sustaining economies and preserving the ecological integrity
of estuaries.
