Effect Of Dissolved Oxygen On Plathemis Lydia Larva Growth

In this experiment the effect of dissolved oxygen on Plathemis Lydia larva growth. For this experiment the focus is on the effects of dissolved oxygen on Plathemis Lydia larva growth in wetlands. The independent variable in this experiment is dissolved oxygen. Dissolved oxygen can be affected by a variety of things such as temperature and volume of water. Oceans for example have an average dissolved oxygen level of 9 mg/L to 4 mg/L depending on the depth. Wetlands however have a higher average dissolved oxygen level and can boast dissolved oxygen levels of up to 18 mg/L. To put this in context a dissolved oxygen level of 5 mg/L can be harmful for most aquatic life. If the dissolved oxygen level drops all the way to 2 mg/L then large aquatic life starts dying.

One reason for the difference in dissolved oxygen levels with oceans and wetlands is salinity. The chemical structure of NaCl does restrict water’s ability to absorb water. This results in a major difference between freshwater and saltwater dissolved oxygen levels. Small organisms are affected more by dissolved oxygen changes due to their ability to adapt. Most dissolved oxygen come directly from the environment, but some also comes from underwater plants conducting photosynthesis. Underwater plants conduct photosynthesis by absorbing the CO2 in water and sunlight and converting this into sugar which are used by the plant and the oxygen created by photosynthesis is absorbed by the water and contributes to the dissolved oxygen level.

Dissolved oxygen tends to be higher in moving water such rivers and streams compared to standing water such as ponds and rivers. This is because moving water is better aerated, exposed to air. Temperature can also have major effect on dissolved oxygen. Warmers waters can hold more oxygen compared to colder waters. Dissolved oxygen can be measured in mg/L or ppm. In an artificial environment like a lab, dissolved oxygen is altered using nitrogen and oxygen canisters, nitrogen is used to displace oxygen, aka reduce the dissolved oxygen level. Oxygen is added to increase dissolved oxygen levels. The mixture of oxygen and nitrogen can be controlled by a regulator that can calculate the existing dissolved oxygen level and accordingly add oxygen and nitrogen to reach a certain dissolved oxygen level. There are also other ways to measure dissolved oxygen, one of the newer methods is through an optode, a device that uses optical sensors along with chemical transductors do determine the dissolved oxygen level of a body of water.

Dissolved oxygen also plays a major role in decomposing organic matter. Dissolved oxygen is vital for the survival of a lot of small bacteria that helps decompose microscopic organisms such as algae and protists. These microscopic decomposers will die if dissolved oxygen levels get too low, resulting in accumulation of organic matter at the bottom of the body of water. This would significantly affect the lives of plants and animals that live on the bottom of these bodies of water. The dependent variable in this experiment is Plathemis Lydia larva growth. Dragonflies are mainly found near bodies of water because they give eggs in water. The common whitetail dragonfly’s male and females are almost indistinguishable besides from the males having a white body and the females having a brown body, the wings also are slightly different. Dragonfly mating starts with the female going near a pond to lay its eggs. Males are very territorial, and females tend to mate with males that have control of the best areas of a pond. This results in females rejecting a lot of male because their territory isn't good enough for laying eggs. Once the female accepts the male and they finish mating, the male with go through a very protective phase where the male hovers less than a meter away from the female to ward of any other males. The female then strategically deposits its eggs in multiple locations so that predators won’t get to all the eggs at once. These eggs are normally given in mud or the edge of a pond. If the water’s conditions fluctuate the eggs may die. Plathemis Lydia give hundreds to thousands of eggs throughout their lifetime.

It normally take anywhere from two to five week for a dragonfly egg to become a nymph. Once the eggs hatch out comes a nymph. Nymphs have no wings and aren't capable of much underwater movement. Nymphs may stay underwater for as long as four years, this is also the point in their lives where they are the most susceptible to being eaten by other aquatic life due to their lack of a defense mechanism in the water. They can only become dragonflies in the spring due to increasing temperatures. Plathemis Lydia nymphs can sometimes go up to 4 years before becoming an adult Plathemis Lydia. As nymphs Plathemis Lydia are known for eating everything from mosquito larva and small insects to small fish and tadpoles.

Once the Plathemis Lydia nymphs become Plathemis Lydia adults they only wait a few weeks before they reproduce and start the life cycle all over again. Plathemis Lydia populations are currently stable, one main reason for this is their ability to lay eggs into a wide range of freshwater sources. They may prefer more muddy water for egg protection but have been seen laying in industrial cow ponds (these are used for drinking water for the cows). Their ability to adapt is a major reason why they have a stable population. Plathemis Lydia were initially found in British Columbia, but they are now found in most of the North America continent. They have now been found as in parts of Central America, specifically Mexico. The large species range allows Plathemis Lydia to have a large gene pool, resulting in a high amount of diversity within Plathemis Lydia. Wetlands act as a sewage system for the planet. They take in endless amount of water, that comes from a variety of places. All this water helps wetlands create a very amphibian and insect heavy ecosystem that can be found in most other ecosystems. They can also help our environment by storing water that stores large amount of carbon dioxide that can help lead less global warming.

Wetlands also hold many benefits such as a tourist spots due to the high biodiversity and specific species that can only be found in condition synonymous with wetlands. The nutrients collected by water bring in sediment can not only be helpful for the sustainability of soil, but some nutrients are even found in current human medicine that can save thousands of lives. The importance of wetlands does not only fall on the species that live in it, it influences extends to the global level. If dissolved oxygen levels increase over 5 mg/L then dragonfly larva growth rate will also increase. In big fish lower dissolved oxygen level results in widespread death. A similar effect will happen to dragonfly larva, the effect of lower dissolved oxygen will be worse than big fish due to dragonfly larva due to their inability to adapt to their surroundings, which is a result of their small size. A similar parallel between size and adaptability on land.

Thousands of bacteria will die from the smallest habitat changes such as increase of a few degrees Fahrenheit. Larger animals such as elephants aren't as dramatically affected by an increase of a few degrees Fahrenheit. Due this connection it can be reasonably inferred that a lower dissolved oxygen level would be detrimental to all aquatic life especially benthic microbes such as Plathemis Lydia larva and especially their growth.