1. A Comparative Stream Study of Two First Order Streams in Nixon Park, York PA Susan Price Department of Biological Sciences, York College Introduction Macroinvertebrates can play an integral role in aquatic environments. These organisms are detrivores, meaning they break down leaf matter in which they also live (Freshwater 2004). Although this leaf material provides ample protection for macroinvertebrates they are still prey to fish and other stream organisms higher up on the food chain. Black Nose Dace (Rhinichthys atratulus) is a common fish species living in York County streams. It preys upon many different types of macroinvertebrates (Steiner 2009). Mancinelli (2007) found fish predation affects the macroinvertebrate community composition in streams. To investigate the effects Black Nose Dace have on macroinvertebrate community composition I conducted a fall leaf pack study. In this study I compared the macroinvertebrate diversity, evenness, and richness of two first order streams in Nixon Park, York, PA. One stream (Stream 1) had a population of Black Nose Dace and one did not (Stream 2). In addition to studying the macroinvertebrates a chemical analysis and measurement of the streams substrate and water depths were completed to create an abiotic stream profile. Methods Leaves were collected from 4 common tree species present in Nixon Park during October. To determine the amount of wet leaves to place in the leaf packs a linear regression was created. This compared the wet weight of each tree species to its dry weight To assemble the leaf packs the equivalent of 1g dry weight of each tree species was placed in each mesh bag. (n=40) 20 packs were placed along various sites in both stream locations at Nixon County Park. Packs were secured to the stream bottom using metal stakes. After 5 weeks leaf packs were collected from streams. Macroinvertebrates were separated from leaf material and stored in 70% ethanol for counting and identification. Dissolved O 2 and pH were measured twice during the study for each stream (n=10 per stream) Water samples were collected for chemical analysis of NO 2, NO 3, PO 4 Stream depth and substrate depth were measured for both streams. Discussion Contrary to expectations, macroinvertebrate communities did not differ between streams with and without Black Nose Dace. Phosphorus and nitrate results can be compared to Brisbois (2008). Fluctuations of these chemicals could be due to passed agricultural activity in the area (Fran Velazquez pers. comm). Acknowledgments I would like to thank Dr. Kleiner for being a great mentor as well as the Nixon Park staff for allowing me to complete my study in the streams. I would also like to thank Shawn Fauth and Chris Broking for helping me out in the field. And Justin Mabry for supporting me throughout this past year. Questions Asked 1.Is there a difference between the species diversity, evenness and richness of a macroinvertebrate community in Stream 1 and Stream 2? 1.Will there be a difference in the abiotic stream profile that could effect macroinvertebates? Further Research Examine the effect fish and chemicals have on macroinvertebrate communities. A larger sample size and further study of other streams should be completed. Table 1: Mean macroinvertebrate abundance per leaf pack (stream 1 n=19, stream 2 n=15) Figure 9: Diagram of the average water and substrate depths of Stream 1 (A) and Stream 2 (B) 4.29cm4.58cm 14.89cm 11.34cm Results A B There was no significant difference in macroinvertebrate evenness and diversity between streams Species richness was similar in both streams Stream 1 and Stream 2 did not differ in pH Dissolved oxygen did not differ during calm weather but did differ during a storm event Phosphorus was significantly different during calm weather but was not different during a storm event Nitrates were significantly different during both times of calm weather and a storm event Nitrites were not different during calm weather but were different during a storm event The water depth for Stream 2 was.29 cm higher than Stream 1 The substrate depth for Stream 1 was 3.55 cm deeper than Stream 2 MacroinvertebrateStream 1Stream 2 Sphaeriidae 1 0.133 Plecoptera 10.959.8 Baetidae 1.6315.53 Oligochaeta 1 5.55.53 Turbellaria.21.4 Oligochaeta 2 0.066 Chironomidae 9.424.66 Ceratoposonidae 3.160 Trichoptera.1581.33 Diptera 1.4740 Oligochaeta 3.2105.066 Sphaeriidae 2.053.066 Diptera 2.737.8 Prosobranchia.2105.066 Diptera 3 0.066 Hydropsychidae.105.4 Coleoptera 1.1050 Spiral Worm.1580 Coleoptera 2.05.066 Unknown 1 0.066 Diptera 4 1.26.4 Acariforms 0.133 Earthworm.1580 Lepidostomatid 0.066 Literature Cited Brisbois, Marie Claire, et al. 2008. Stream Ecosystem Health in Rural Mixed Land use Watersheds. Journal of Environmental Engineering and Science 7:439-452 Freshwater Benthic Macroinvertebrates: Useful Indicators of Water Quality. Available from: http://www.dnr.state.md.us/streams/pubs/freswater.html. Accessed 2008 December 28. Mancinelli, Giorgio, Costantini, Maria Letizia, and Rossi, Loreto. 2007. Top-Down Control of Reed Detritus Processing in a Lake Littoral Zone: Experimental Evidence of a Seasonal Compensation between Fish and Invertebrate Predation. International Review Hydrobiology.92: 117-134. Steiner, Linda. 2009. Pennsylvania Fishes. Common Wealth of Pennsylvania, Fish and Boat Commission.