Abstract to be lotic, which means that they

Abstract Two different bodies of water were used, specifically the stream and the pond, in this experiment to test how they affect net primary productivity.  Net primary productivity is the amount of chemical energy captured by the producers through photosynthesis minus the amount of respiration.  The experiment was conducted in the Fullerton Arboretum.  Four BOD bottles were used, two for each body of water, to measure oxygen concentration and water temperature as a means of calculating NPP.  The data was provided on Excel and it was organized in a way to make graphical and data analysis easier to do.  The hypothesis was to test whether there is a significant difference in NPP between the stream and the pond.  The results showed a significant difference between the stream NPP and the pond NPP as shown in Figure 1 and reiterated by the t-test.  There is evidence to support that the type of water that different organisms live in can lead to differences in net primary productivity and overall impact them in a drastic way.Introduction Freshwater and aquatic ecosystems consist of diverse bodies of water, such as lakes, ponds, rivers, and streams.  Lakes and ponds are considered to be lentic, which means that they are standing or still bodies of water.  On the other hand, rivers and streams are considered to be lotic, which means that they are flowing bodies of water.  These ecosystems are classified as the amount of nutrients present, which determines how much productivity will take place.  Primary productivity is measured through Net Primary Productivity (NPP), Respiration (R), and Gross Primary Productivity (GPP).  NPP is defined as the amount of energy that producers capture by photosynthesis minus the amount used on respiration (chemosynthesis).  Photosynthesis can be described in two ways.  One way to describe it is as the production of oxygen by consumers.  Another way is when the organisms use sunlight to produce food from carbon dioxide and water.   R is defined as the consumption of oxygen by producers and consumers.  Lastly, GPP is defined as the rate at which light energy is converted to chemical energy by photosynthetic and chemosynthetic organisms.  These ecosystems can also be described in terms nutrient availability as oligotrophic, mesotrophic, and eutrophic.  If aquatic ecosystems are oligotrophic, that means that they lack sufficient nutrients.  If the ecosystems are mesotrophic or eutrophic, that means that they have an average amount of nutrients or are nutrient rich, respectively.  The hypothesis tested for this experiment was whether there is a significant difference in NPP between the stream and pond habitat.  The null hypothesis on the other hand, states that there is no significant difference in NPP between the stream and the pond habitat.Methods For this experiment, the materials consisted of a YSI oxygen meter, magnetic stirrer, electrode, four BOD bottles, microscopes, and slides.  The very first step was to calibrate oxygen using an additional BOD bottle with water filled up to about 1 inch, a YSI meter, and an electrode.  Two replicate pairs of light and dark bottles, labeled A and B, were then gathered and the oxygen concentration was measured in each.  A contained water from the pond and B contained water from the stream.  To ensure that the concentration remained the same throughout the water, the BOD bottles were added with a magnetic stirrer.  The YSI meter was also used to measure and record the water temperature.  For the remaining three bottles, the procedure was repeated three more times.  This experiment was done before hand and the data was premade by students from previous semesters.  Using data from only the fall semesters, a pivot table was created on Excel to create a graph comparing the average NPPs of the stream and the pond as well as a t-test data analysis.  These results were then used to support or reject the hypothesis.  Results Figure 1. Graph of NPP of the stream and pond.Figure 1 depicts the average Net Primary Productivity between the stream and the pond.  According to the graph, the pond seems to have a much higher NPP compared to the stream.  This graph supports the hypothesis in that there is a significant difference in NPP between the stream and the pond.  The error bars on the graph are close to microscopic, making them hard to see.  The small error bars are a representation of little to no flaw in the results and a high probability of accurate results.   There was also a two-tailed T-test done between the stream and the pond (t-stat = 1.977, p-value = 0.0000000000152).  The P-value came out to be extremely small (< 0.05), thus the results are significant, and the hypothesis is supported.Discussion Figure 1 shows that the pond has a higher net primary productivity compared to the stream.  One of the main reasons why the pond would have a higher NPP is due to their size.  Their bigger size enables them to have more organisms present, thus increasing NPP.  Ponds, being lentic bodies of water, have an advantage because they are still and therefore, more nutrients and productivity available.  Due to the availability of nutrients, ponds are better able to sustain life and provide energy to the organisms.  Streams, on the other hand, are lotic bodies of water, or flowing water, and so they are at a disadvantage because nutrients are constantly being swept away.   Streams have the least amount of productivity, giving primary producers very little time to photosynthesize and conserve energy.  The two-tailed t-test performed in the results shows the difference in NPP between the pond and the stream (t-stat = 1.977, p-value = 0.0000000000152).  Since the P-value is very small (< 0.05), the null hypothesis would be rejected, indicating that the two means are different.  The reason for such a difference is probably because the stream has nutrient-limiting factors that prevent organisms from being able to produce nutrients and increase stream productivity and the pond does not.  Howarth (1988) states, "Both phosphorous and nitrogen can simultaneously be limiting factors or that primary production can switch seasonally from being nitrogen-limited or phosphorous-limited."  This experiment was done using the fall data and during the fall, the stream could have these nitrogen or phosphorous-limiting factors rather than the pond.  If the spring data was used, the results may have been the other way around.  According to Bott (1983), "Harvest techniques (which ideally should include below ground material) also yield a net estimate loss through respiration, grazing, fragmentation, or sloughing, even though they are usually are not accounted for."  These are other factors that could affect why the stream has such low productivity.  Productivity depends on a variety of factors and the stream could have been affected by any one of these rather than the pond, since it has such a high productivity.  Likens (1975) states, "Many of these aquatic ecosystems have undergone dramatic changes in recent years as a result of man's activities. In some cases, the change has been beneficial to man's short-term desires and requirements, but often the changes have been detrimental (e.g., polluted water supplies) because man has used water bodies widely as an inexpensive receptacle for waste products."  Human activities could perhaps be one of the major factors why such bodies of water either have or lack productivity.  Generally, streams have organisms such as insects, snails, and worms and humans are not very fond of them.  The lack of care for these organisms could result in polluting the streams and leaving the organisms to die.  On the other hand, ponds have organisms such as tadpoles, fishes, and turtles, which humans tend to like more.  This would result in more care of the pond, being careful not to pollute it or cause harm to the organisms in it.  Some possible sources of error include the fact that there was more data collected for pond compared to the stream, so it could have skewed the results to favor the pond, since only the fall semester data was used in this experiment.  Also, the experiment had already been done and the data had already been collected and provided, rather than performing own experiment.  This is a major disadvantage because others' data must be relied on rather than your own and a different result might have occurred if it was performed on my own.    For future research, it would be best to perform one's own experiment and repeat it multiple times to compare data and results with.  This ensure the accuracy of the experiment with little to no room for skewed or incorrect results.  


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