This study will be testing the effects of turbidity on the abundance of Dragonfly Nymphs. It is important to understand the potential findings of this study to know what level of turbidity is best suited for this organism, and the effects turbidity has on their prosperity. The experiment will allow for specific data to be measured on the Nymphs. This will not only increase knowledge on this species, but the impact they have on the ecosystem through a ripple effect. Through these findings, changes can be made in order to protect the environment and the wildlife found within.
The independent variable in the study is the amount of turbidity present in the water. Turbidity is the measurement of how much the water loses its transparency, or the ability of light to penetrate the water. Water with lots of scattered particles is marked as having high turbidity because the particles prohibit light from easily passing through it. Turbidity gives valuable data when testing the quality of different water samples. Water most often contains suspended particles of many different sizes. If certain particles weigh enough to eventually sink to the bottom of a contained volume of water when it settles, it is called a settleable solid. The remaining smaller particles will sink at a slower pace, these are known as colloidal solids. The colloidal solids are the particles responsible for giving water it's turbidity.
There are many different causes for the amount of turbidity water has based on its surrounding areas. In open water, having a large population of phytoplankton can contribute to high turbidity in that region. Another common cause for turbidity is erosion. Sediment is taken from the riverbank, or carried through runoff into rivers and streams. This effect can often be seen in areas undergoing construction. Precipitation causes runoff to form, which carries sediment and high turbidity water into bodies of water. Turbidity dramatically increases when fine silt and clay particles get caught in the runoff. These particles take a while to settle due to gravity, causing high turbidity that can be seen in the murky coloring of the water. Turbidity can also be caused by runoff of paved structures like parking lots, roads, or sidewalks. These areas contain many different particles such as pieces of pavement, rocks, sediment, etc. Turbidity is an essential factor to calculate when also looking at potable (drinking) water. Higher the turbidity, the more likelihood of developing gastrointestinal diseases. This is because viruses and harmful bacteria are able to attach themselves to the floating particles. These contaminants are better able to take effect because the suspended solids they are attached to interfere with disinfection.
Measuring turbidity is done by shining a light beam through water and is measured in the United States in Nephelometric Turbidity Units (NTU). Nephelo is greek for cloud, while metric means measurement; defining nephelometric as “measuring cloudiness”. A nephelometer is used to shine the light beam through the water, the suspended solids floating in the water scatter the light. The more light that is able to reach the detector, the less turbidity the water has and vice versa. The measurement can easily vary based on the location of the water sample. A way to measure turbidity in open water is to use a Secchi disk. A Secchi disk is a black and white disk that is lowered down in the water until it is no longer visible. This depth, known as the Secchi depth, is recorded using its correlating number to measure the clarity of the water. This device gives an advantage by allowing multiple areas with different turbidity layers to be measured in a cheap and simple way.
High turbidity can have a degrading impact on the tourism and recreational usage of bodies of water by causing a decline in the esthetic quality of the water. Water with high turbidity costs a lot more to treat for drinking/food production purposes. It can also have a harmful effect on organisms by disrupting gill function, decreasing the amount of food available, inhibiting the complete development of fish larvae and eggs, reducing resistance to diseases, prohibiting aquatic plants from carrying out photosynthesis, and reshaping migrations and natural movements.
Turbidity has a negative effect on wetlands and its containing species. If the process of sediment from runoff and erosion continues, it will cause a chain of reactions that has the potential to be devastating to these important ecosystems. Whether one species is terminated or many, the ecosystem will be damaged regardless. Each organism has a job/role that is vital to the survival of another. It may be a predator/prey or any other symbiotic relationship that connects each and every organism in an ecosystem. It is important to understand and analyze the issues regarding turbidity, in order for a proper solution to be found.
The dependent variable is this study is the Dragonfly Nymph (Erythrodiplax berenice). A nymph refers to a premature stage of an insect's life, before it undergoes metamorphosis. Nymphs differ from common larva by already showing features of an adult. Another difference between Nymphs and common larva is the stages of development. Nymph’s stages of development are known as instars, during instars the nymph moults. Moulting refers to the shedding of the exoskeleton to uncover a new, larger, and more developed body. Towards the end of their days in the nymph stage, their wings will be developed but folded on their back. They use the stems of plants to crawl above the water and use their wings, now an adult.
Dragonfly Nymph’s are aquatic insects with six legs and two large eyes with little wing buds located on its thorax. Each of the legs contains 2 claws. The color of their skin is based on their environment, but typical colors include; brown, a darker red, and occasionally green. Dragonfly Nymphs have an oval shaped abdomen, and a scoop-shaped lower jaw (mask) that covers majority of their head. The lower jaw contains connected parts with palps at the end. These palps secure the sharp spikes that the Nymphs use to grab hold of their prey. They can range from being ¼ to 2 ½ inches in length, exact length varies on age and habitat. They are able to breathe through the gills found in their rectum. They force water in and out of their behind, which also gives them ability to move around swifty through a kind of jet propulsion.
When attempting to catch prey, they are able to increase the reach of their mask by contracting the rest of their body muscles/fluids. This ability is a fast-acting mechanism that makes them a predator in their habitats. They use camouflage by crawling and staying on top of rocks with a similar color. This allows them to appear as smaller rocks to prey swimming by, whom they will then ambush and consume for dinner. Dragonfly Nymphs will eat almost any organism that is smaller than itself, these vary from random invertebrates to even tadpoles and small fish caught by larger ones. They use their camouflage and jet propulsion ability to avoid being eaten by predators. Typical predators include larger insect nymphs, fish, and leeches.
Dragonfly Nymphs
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