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Riffle Population Estimation Using Depletion Sampling

The paper presents population estimation in Little River, Blount County, Tennessee and its analysis through the River Continuum Concept. Depletion sampling using three trials was performed to get a sample population. The program CAPTURE was used in order to estimate the population given the samples gathered. The population presents an abundance of species specifically thriving and adapted for a high kinetic energy environment. The population also presents species benefitting from dead leaves and woody debris.

Findings in this paper conform to the River Continuum Concept, presenting a deep relationship of the biotic community and its physical environment. Introduction: The River Continuum Concept (Vannote, et al. , 1980) indicates that the abundance and diversity of species in a physical system depends on its gross primary productivity to community respiration (P/R) ratio, particulate matter, maximum diel temperature range, and other changes that effect a redistribution of the kinetic energy in the system.

The concept also states that the tendency of a biotic community is to maximize the energy available in the physical and biological environment. Different relationships, such as stream size to ecosystem structure and function, upstream energy inefficiency to downstream adjustments, and particulate organic matter, dead leaves and wood debris to general functional groups (Vannote, et al. , 1980), are established in the concept. These relationships establish a continuous gradient of biological analogs (Vannote, et al. , 1980) to the system.

Thus, for every system, there is a predictable functionality and structure of the biological community given its physical environment. This predictability allows the verification and easier data processing of a population sample data given its environment. It also establishes a valid hypothesis for every pre-sampling and post-sampling analysis to the functionality and structure of the biotic community. The concept also aids to the establishment of the interrelationships within and throughout the biotic community and its physical environment.

The population sampling shall establish the validity of the River Continuum Concept given a high-energy environment. Through population sampling in a riffle and with the assumption that the riffle is a closed environment, the concept shall be used in order to establish the relationships of the population sample with the environment. Methods: Location: The sampling location shall be at the Little River, Blount County, Tennessee, upstream before its outflow to Fort Loudon Lake and the Tennessee River. Equipments Used: The equipments used in the population sampling are the kick net, ice tray, timer and white pans.

Procedures: 1. Choose a convenient location for the kick net. Then, choose a precise area upstream of the kick net. Disturb and wash rocks for a fixed amount of time in order to get a population sample. Sample the riffle for a fixed amount of time. 2. Collect the organisms in a pan, keeping them away from direct sunlight. 3. Resample the area for the 2nd and 3rd trials, separating the collected samples from the other trials. There should be a decrease in the number of gathered organisms during each trial.

If there is no decrease in the sample population, or if the observed reduction in sample population is questionable, a 4th trial should be taken following the procedure above. 4. Tally the number of organisms in each category in the data sheet, tallying separate tallies per sampling trial. Place sampling-finished organisms in the ice tray separate them. 5. After sampling, release the macroinvertebrates into the water. 6. Process the gathered data through the CAPTURE program provided by the USGS- PWRC (White, et. al, 1978), which is accessible through http:/www. mbr-pwrc. usgs. gov/software/capture. html. Results:

The area was sampled with a fixed time period of 30 seconds. Using the depletion sample method through the procedures listed above, the gathered data are listed in the following table (Data Gathered in the Experiment through Sampling and CAPTURE Program). The gathered data shows a dominance of the Flattened Scraper, followed by the Filter Feeding Cats Fly. The sampling also indicates a discrepancy in the sampling; some samples present the presence of certain species in that particular sampling, some increase in number as the trials were undertaken, while others were only discovered in the third sampling.

Data Gathered in the Experiment through Sampling and CAPTURE Program Abundance Organism Sample 1 Sample 2 Sample 3 Confidence Interval Population Estimate Water Penny 1 1 1 with standard error 0 Giant Shredder 1 1 1 with standard error 0 Flattened Scraper 5 6 16 to 41 23 with standard error 6. 0 Filter Feeding Cats Fly 3 1 4 11 to 32 16 with standard error 4. 9 Water Shype 1 1 1 with standard error 0 Water Beetle 1 1 1 with standard error 0 Chironomid Midge 1 1 1 with standard error 0

Flattened Mayflies 3 1 5 to 17 6 with standard error 2. 4 Burrowing Mayflies 1 2 to 14 3 with standard error 2. 4 Hellgrammite 1 2 to 14 3 with standard error 2. 4 It was also observed that the area was a bit dense in terms of tree population. Discussion: The River Continuum Concept indicates an intricate relationship of the physical-geomorphic environment and the biotic environment (Vannote, et al. , 1980). The findings of the population present a community adapted to clinging into rocks and/or found in leaf packs (Raymond and Robinson, 1999).

The abundance of leaves, an effect of the quite dense tree population in the riffle, allows the growth of insects thriving on the leaves, such as the Water Penny and the Giant Shredder. The presence of shredders, collectors and scrapers indicate the presence of both coarse (CPOM, >1mm) and fine particulate organic matter (FPOM, 50µm – 1 mm) (Vannote, et al. , 1980). These organisms thrive on the microbial biomass found primarily on particle surfaces (Vannote, et al. , 1980). The organisms present are in line with the high kinetic energy and thus high sediment transport capability of the riffle.

Burrowing Mayflies, which burrow under sediments, are an indication of sediment deposition near the rocks in the riffles. The Hellgrammite, the biotic environment predator, is capable on feeding on the organisms present in the community. In the data, there is a discrepancy in the sampling which does not follow the prediction of the depletion sampling method. A formidable presence of samples in the third trial shown in the following table (Population Sampling Trials of Little River, Blount County, Tennessee) suggests that there may be more organisms present in the water, with a maximum standard error of 30%.

The discovery of more species of organisms in the third trial also suggests that there may be more organisms present in the water. A fourth trial may be suggested for the improvement of data and for the accuracy of the results. The gathered data shows a maximization of the energy present in the ecosystem, with all the organisms making use of the biotic and physical environments of the riffle. Thus, the River Continuum Concept is proven and is supporting the findings of the population through the samples.

Literature Cited Vannote, R. L. , G. W. Minshall, K. W. Cummins, J. R. Sedell, and C. E. Cushing, 1980. The River Continuum Conept. Can. J. Fish. Aquat. Sci. 37:130-137 Raymond K. , J. Robinson, BIO-ASSESS, W. G. Deutsch and Auburn University. “ECO Photo Guide to Aquatic Macroinvertebrates of the Southern Appalachian Mountains. ” ECO. ECO, Jul. 6, 2010. Web. Jul. 25, 2010. White, G. C. , K. P. Burnham, D. L. Otis, and D. R. Anderson (1978). Capture. USGS-PWRC. http://www. mbr-pwrc. usgs. gov/software/capture. shtml

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