1. How do diurnal tidal cycles affect habitat selection in Piermont marsh? Giselle Triviño and Janeth Ortega Piermont Marsh Abstract MethodsResults Number of organisms vs. creekWater quality vs. creek Animal density in three Hudson River sites Water quality in three Hudson River sites Animal density in three interior pools sites Event 1: Water quality in three interior pools Event 2: Water quality in three interior pools Event 3: Water quality in three interior pools. 3 sampling events were conducted: Event 1: Sparkill, Tidal, Crumkill, Hudson River and 3 pools were sampled. Events 2 and 3: Interior pools 1, 2, and 3 were sampled. Creek sites include erosional and depositional banks, and rivulet habitats. 3 minnow traps were deployed along a 3 meter transect. Water depth was measured with a PVC pipe. Salinity, temperature, dissolved oxygen was measure a YSI meter Traps were deployed for 24 hours. Organisms were preserved in 10% formalin solution. Samples were returned to lab; after 24 hours, rinsed and transferred to 50% solution of Isopropyl alcohol. Organisms were measured, identified and weighted. Pool 1 Assembling traps Sample transect Pool 2: train tracks from late 1800’s still remain. Sample jars Fish being identified. Site map Sparkill Creek Piermont Marsh is located on the west shore of the Hudson River. It is a brackish marsh and occupies 284 acres. It is disected by three creeks; Tidal (unnamed),Sparkill, and Crumkilll. Piermont Marsh provides critical habitat for many organisms. Phragmites australis has rapidly replaced native vegetation, reducing habitat for aquatic organisms. Phragmites australis is an invasive plant. Rapid expansion occurs in disturbed soils and native wetlands plants are pushed out. Culms can reach a height of over 5 meters; stems, 1.5 to 2.5 centimeters in diameter; rhizomes reach lengths of more than 12 meters. Colonies can be very dense; areas in Piermont Marsh have densities greater than 200 culms per m², creating a fence that prevents restricts movement of aquatic animals across marsh surface. Phragmites australis Conclusion Our data showed that during spring tides water levels are high enough to provide habitat for aquatic animals in the interior pools. Events 1 and 3 were conducted during neap tides; Event 2 was conducted during spring tide. Our study indicates that animal density varies with the lunar cycle. There is little variation between temperature, dissolved oxygen and salinity across the 3 creeks. However physical data varies between creeks and pools. Our study will continue throughout the fall and winter seasons to observe seasonal variations in habitat use. The objective of this project is to investigate how the diurnal tidal cycles affect habitat selection in Piermont Marsh. We investigated 3 creeks within the marsh, 3 sites on the Hudson River- marsh ecotone, and 3 interior pools to answer these questions: Which habitat has the greatest number of organisms? Is there a difference in the number of organisms in the creeks, pools, and Hudson River? Is there a relationship between salinity, temperature, dissolved oxygen, and the number of organisms? Our results show a greater number of organisms in Sparkill Creek and many fewer in the Hudson River sites. Number of organisms found in pools was affected by lunar cycles. Physical data did not vary significantly across the creek sites; more variation occurred in pools. This ongoing investigation will continue throughout the school year.