A habitat is a place where an organism lives. All habitats provide basic necessities of life including: food, oxygen, water, space and shelter.
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When an organism’s habitat changes, the organism must adapt or migrate, or it can die. For examples, a lobster’s habitat is shallow water along the sea floor. Until the 1990s the Long Island Sound provided American lobster with a wonderful habitat. Habitat destruction is often thought of as a physical loss of resources. such as deforestation or cutting down trees to build homes. For lobster however, habitat loss can occur simply by changing conditions of the surrounding water. The following are several changes to Long Island Sound that are believed to have contributed to the 1999 lobster die-off.
Oxygen levels and hypoxia
Oxygen is dissolved in sea water. While we as humans breathe oxygen through our lungs, lobster and other aquatic life breathe oxygen when they take in water through their gills.
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The amount of oxygen on the sea floor of the Sound has been dropping since the 1970s. This decrease in oxygen levels is called hypoxia and it is believed to have created a stressful environment for the lobster.
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Several factors have led to this decrease in oxygen levels, including an increase in nutrients such as nitrogen flowing into Long Island Sound from sewage and fertilizers. As the Long Island Sound watershed has become more developed there is more pavement, more sewage, and more fertilizers used on lawns.
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More pavement causes more water with fertilizers (nutrients) to flow into Long Island Sound. The effluent of a sewage treatment plant is a point source for nutrients. Also, sometimes during a big rainstorm, sewage treatment plants will release untreated sewage to the Sound due to combined sewer overflow. Once in the Sound, these extra nutrients cause more algae to grow.
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When they die, they sink to the sediment and bacteria break them down and use oxygen in the process, causing dissolved oxygen, or oxygen in the water, to go down. Since the water is stratified, the low oxygen in bottom waters is not easily replenished from the atmosphere.
Sulfide and Ammonia
When sediments on the bottom of the sea floor do not receive enough oxygen, a different type of bacteria, that does not need oxygen, can take over.
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These bacteria releases hydrogen sulfide, which is a poison. Concentrations of ammonia can also get high enough to be toxic to lobsters. The types of bacteria that survive without oxygen are called anaerobic bacteria. Thus, a secondary impact of anoxia caused by nutrient loading is the production of these toxic compounds.
Pollution
For many years, Connecticut and other states the boarder the Long Island Sound have dumped the runoff of rainfall, agriculture, and sewage into the Sound. Until recently, people did not consider the impact this pollution was having to organisms on the bottom of the Sound. The 1999 lobster die-off led scientists and researchers to uncover what was causing large numbers of lobster and other organisms to die.
One of the causes they found was nutrient loading. Nutrient loading is the increase of nitrogen and phosphorous compounds in a body of water. This is usually due to a lack of wetlands, agricultural runoff, and urbanization of land.
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When nitrogen and phosphorus levels increase to high levels in the water, they can become harmful to aerobic aquatic organisms.
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Anaerobic organisms on the other hand thrive when these compounds increase, leading to an increase in bacteria and fungi. These anaerobic organisms then take oxygen out of the water and add methane gas. This oxygen depletion can lead to hypoxic conditions, which are dangerous of many organisms in the Sound, including lobster.
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Hypoxic environments exist when any of the following conditions occur including, “elevated water temperatures, organic carbon loading from agriculture, elevated sediment temperatures, poor bioturbation, dissolved oxygen levels and water stratification.”
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When a combination of any of these factors are present over long periods of time it can create a very harmful environment.
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While hypoxic environments usually are present for short periods of time, such as during the summer months, this problem has existed in the Sound for a much longer period of time now, leading to the death of organisms, like the American lobster.
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Freshwater run-off during rain storms has also increased along the Sound. Run-off transports a variety of non-point source pollutants into local water bodies and the Long Island Sound, including pet waste, automobile fluids, fertilizers, herbicides, pesticides, and debris.
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These materials have a negative impact on the water quality.
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The good news is that actions can be taken to improve conditions in Long Island Sound. By preventing excess sewage and storm runoff from entering the Sound cities can greatly reduce pollution to the water. One way of doing this is by creating storage tanks to hold water during major storms. Also, by helping re-build wetlands we can “catch nutrients” and stop them from freely flowing into the Sound watershed.
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Temperature
Lobsters prefer temperatures below 20.5 degrees Celsius. However, lobster in the Sound are being subject to stressful conditions, as the temperature on the sea floor of the Sound has been rising since the 1970s. For example, in September of 1999 the water at the bottom of the Sound reached temperatures of 24 degrees Celsius.
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This also causes an increase in stratification, mentioned earlier, which coupled with the decrease in oxygen levels further complicates the situation for lobster in the Sound.
Neoparamoeba paraquedensis
Increasing temperatures have also lead to an increase in the
Neoparamoeba paraquedensis
parasite leading to additional stress on lobster populations. The parasite is just one of more than forty lobster parasites found in the Sound. Scientists believe that
Neoparamoeba paraquedensis
has become more dangerous to lobster in recent years, because the parasite it able to reproduce more quickly in the warmer water.
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Climate
Climate is a description of the “temperature and weather found in a particular location.”
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The climate of an area is based on the amount of sunlight it receives, the local geography of the region, and local bodies of water.
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Sunlight is the most influential factor on the climate of region. The Earth rotates on its tilted axis once every day. This rotation of Earth on its axis causes day and night. While the Earth is rotating it is also revolving around the sun. The Earth makes one full revolution each year. The 23.5 degree axis of the Earth’s axis combined with the revolution causes the change in seasons. Connecticut is located in the northern hemisphere, which means that it is getting the most direct sunlight from the spring through the fall. From the fall through the spring the northern hemisphere is pointing away from the sun leading to colder temperatures. Areas that have higher latitude, those that are located further from the equator have more dramatic changes in temperature.
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The Sound is located at 41 degrees North latitude, making it about half way between the equator and the North Pole. This latitude location causes significant temperature change between summer and winter for the Sound.
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Another important factor in determining climate is the water located near the area. Water and lad trap and release heat at different rates.
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Water heats and cools much slower than land. A simple experiment that can be used to demonstrate this concept is placing a thermometer in glass of water and another in a sample of soil.
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The third factor that plays a role in climate is the geography of the area.
Locations that have higher altitude have colder climates than areas located closer to sea level. Another geographic feature that impacts climate is proximity to mountains and glaciers, which can block and disrupt wind patterns.
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Wind and Water
When wind and water circulate they carry heat and nutrients from one location to another.
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While the Earth is rotating on its axis, the atmosphere around it does not rotate as fast as the Earth itself.
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This causes the West to East patterns of the wind.
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Another type of air movement in addition to winds is thermal expansion. Thermal expansion causes air to move between the poles and the equator. Areas located close to the equator receive the most direct sunlight and as a result are hotter than areas further from the equator. The sunlight that reaches areas of higher latitude is not as direct making the air in these areas cooler, than air along the equator.
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Air at the equator as a result expands because it is hotter. This expansion causes air molecules to occupy more space, causing other air molecules to be pushed. The air cannot push the ground down and as a result pushes up.
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This explains why hot air rises. When this extra air moves into the upper atmosphere, it joins with the air that was already there, causing the pressure of the atmosphere to also rise.
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Areas close to the poles do not receive direct sunlight and therefore air there does not absorb as much heat as air along the equator. The air at the poles does not expand, causing less pressure in the upper atmosphere.
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Areas near the poles have higher pressure at the ground level and lower pressure in the upper atmosphere. On the other hand, areas near the equator have lower pressure near the ground and higher pressure in the upper atmosphere. The higher pressured air in the upper atmosphere over the equator moves to the upper atmosphere over the poles, since it has more room available.
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This air movement from the upper atmosphere of the equator to the upper atmosphere of the poles causes changes to climate. Some places as a result have hot or cold winds and wet or dry winds.
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Cold and wet winds bring rain and snow, while hot and dry winds dry out the land because they absorb moisture.
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Mountains and other landforms can change the wind pattern. When air hits a mountain, it must go up and over it. As the air travels up the mountain it cools. This cold air holds less moisture than hot air so it lets the water out as rain. When the air finally reaches the top of the mountain it often has very little water left in it. This causes land on the eastern side of mountains to be drier than the land on the western side of mountains.
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Water movement on the Earth’s surface shows similar patterns to air movement. Like the air at the equator, water at the equators absorbs more direct sunlight than water at the poles. Water at the poles is also covered by ice. Water, like air, expands when it is heated causing warmer water to push colder water. This expansion of water is the cause of water currents, like the Gulf Stream, which causes warm water from the Gulf of Mexico to Florida to travel up the eastern coastline of the United States and eventually end up in the Atlantic Ocean.
Both air and water contain energy from the movement of its particles, which is called thermal energy.
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Substances with higher temperatures have a higher thermal energy.
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And energy transfer always goes from warmer to colder substances. Water as a result moves from areas of warmer water to areas of colder water.
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These annual fluctuations in temperature and the amount of sunlight, affects marine sea creatures, like lobster. The water that is first impact by these seasonal conditions is in the upper layers of the ocean because it is involved in direct heat exchange with the atmosphere from solar radiation. Lower layers of the ocean and sea floor are affected later because they do not receive direct heat exchange with the atmosphere or absorb solar radiation from the sun.
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Greenhouse Effect
In a greenhouse, short wave radiation comes in through the glass and turns into long wave radiation. As the long wave radiation tries to escape, it cannot pass through the glass very well, so the whole building stays warmer all winter. On Earth, the gases in our atmosphere act like the glass of a greenhouse.
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Short wave radiation comes in from the sun and long wave radiation tries to escape back to space. While our atmosphere has been trapping heat this way since the early days of the Earth scientists are now concerned because the Earth is trapping more heat than it used to.
Carbon dioxide and methane are examples of greenhouse gases because are better at trapping heat than other gases.
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Some greenhouse gases are created naturally; for example, volcanic eruptions and marshes emit greenhouse gases. In recent decades though scientists have noticed that human activities, like burning gasoline in a car’s engine, produce much higher levels of greenhouse gas than natural activities do.
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This increase in greenhouse gas has led to an increase in the amount of heat trapped in the Earth’s atmosphere.
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This excess heat trapped in the atmosphere has also led to an increase in the temperature of the Earth. While many people love the warmer months of the year, these rising temperatures do not offer favorable conditions for lobster. Lobster prefer cool places and the rising temperatures of the atmosphere have also led to rising temperatures of the water creating a significant habitat change for lobster that must adapt to these warmer environmental conditions.
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About Climate Change
While the Earth’s average temperature has changed over the past 10,000 years, much of this is due to natural causes.
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Over the past 100 years, scientists have seen a much more dramatic increase in the average global air temperature.
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Much of this temperature increase is the result of increased release of greenhouse gases by human activities,
Carbon dioxide is the most abundant and most important greenhouse gas.
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It plays a vital role in keeping the earth’s temperature at a point that can support life. Fossil fuels, including coal, oil and natural gas, are all made up of carbon.
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When fossil fuels, such as coal, oil and natural gas, are burned, carbon dioxide is released. This carbon dioxide can build up in the earth’s atmosphere. The amount of carbon dioxide and other greenhouse gases in the atmosphere is increasing rapidly, as a result of human activities that include fossil fuel combustion and deforestation. In essence, these gases act like a greenhouse, reflecting heat back to the earth’s surface. Some amount of greenhouse gasses is needed to make the earth hospitable for life, but too much can stress organisms and ecosystems.
Climate change is taking place much quicker than it has in any other time in Earth’s history. This rapid climate change is greatly impacting ecosystems and the species that live in them. Some noticeable effects of this rapid climate change include droughts, floods and storms.
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These issues have in turn been linked to an increase human problems such as, disease, death, displacement, and hunger.
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While these change in global temperature may seem small they can have major impacts on the climate.
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Alien Invaders
The Long Island Sound has experienced many changes in its lifetime. One of the most unpredictable changes it has undergone is the introduction of non-native species to its waters. Over the past few decades, the Sound has become home to over 100 invasive species.
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This species also referred to as alien species of both plants and animals are not native to the Sound. By invading the Sound, they have forced native species to have to compete for resources.
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Non-native species have been introduced to areas around the world, and aquatic ones most often reach their new habitats on the outside of ships, in ballast tanks, become pushed along in a water current, and some are even intentionally introduced to a region to solve one problem and often create another.
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Every non-native species has the potential to become an invasive one. An organism is classified as an invasive species when its introduction to an ecosystem causes or is likely to cause economic harm, environmental harm, or harm to human health.
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Invasive species cause a variety of problem for native organisms in the Long Island Sound. While all species are affected by these new organism, endangered species are often most affected by these invaders, as they often eat native species, their food, destroy their habitat, or take the place of the existing species within the habitat. This can put a great deal of pressure and stress on native species that may not be “adapted to compete with the new arrivals.”
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Disease
Researchers have also investigated whether this decline in lobsters could be the result of disease. A number of diseases are associated with lobster death including: parasitic paramoeba, shell disease, red tail, and other bacterial diseases.
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One potential lobster killer is a parasitic paramoeba that enters the lobster’s nervous system and destroys nerve tissue.
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After the parasite attacks the lobster, death usually occurs within 24 hours.
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Additionally, shell disease, a bacterial infection that eats away at the lobster’s exoskeleton, has shown an increase in the Sound in recent years. Researchers believe America lobster are more susceptible to this disease because they are so aggressive. When they fight and molt they damage their exoskeleton, providing an entry point for the bacteria.
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Another lobster disease,
Gaffkemia
, or red tail, affects the lobster’s circulatory system.
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Some believe that the lobster illnesses are due to other changes like temperature, climate, storms, or pollution making lobster more susceptible to diseases and parasites.
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One piece researches do not have data on is how many of the lobster killed by disease were egg-bearing females, affecting the next generations of lobster for years to come.
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