We adapted methods from Palmer & Strayer (1996)

1. 6 40 60 Harpacticoida Aeolosoma sp. Chironomidae 5 50 30 4 40 20 3 30 20 2 10 Col 1 vs Ambient 10 1 Col 1 vs Control 0 0 Col 1 vs Side 0 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 180 10 50 160 Oligochaeta Tardigrada Cyclopoida 8 40 140 120 6 30 2.5 100 4 20 80 60 2 10 2.0 40 0 0 20 0 1.5 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 35 1.0 0 2 4 6 8 Ambient Ostracoda 30 Control 25 Endobenthic 20 Epibenthic 15 10 5 0 0 2 4 6 8 Ambient Epibenthic Endobenthic Control Special thanks to the Biological Field Station, Cooperstown NY RECOLONIZATION OF AZOIC SEDIMENTS BY MEIOFAUNA IN THE HYDROPSAMMON OF OTSEGO LAKE, NEW YORKMark D. Cornwell1 & Thomas G. Horvath2State University New York, Technical College at Cobleskill1 College at Oneonta2 INTRODUCTION EPIBENTHIC EPIBENTHIC & ENDOBENTHIC ENDOBENTHIC SUMMARY Meiofauna are organisms that pass though a 500m mesh and are retained on a 63m mesh and live between the grains of the littoral and sublittoral sediments. Freshwater psammolittoral zones, sediments and their associated meiofauna communities have been classified as either eupsammon (middle beach), hygropsammon (within 1 m above lake’s edge), and hydropsammon (submerged) by Pennak (1940). These nearshore zones often experience physical disturbances, such as wave actions, ice scouring, and lake-level fluctuations, which can defaunate the sediments. The communities associated with these sedimentsmust recolonize after such disturbances. Little attention has been given to recolonization dynamics involving freshwater meiofauna. 300 250 200 150 Total inverts per sample (50 ml) 100 50 0 Invertebrates per sample (50 ml) 0 2 4 6 8 Shannon-Weiner index Time in Weeks Shannon-Weiner Index based on data accumulated through time. All error bars ± 1 standard error. Hydropsammon: Permanently inundated with water. Experimental plot under 0.5m water. Otsego Lake: Deep (50 m max. depth), 1710 hectares, mesotrophic (12 µg TP/L, 0.8 mg Chl a/L). Time in Weeks MATERIALS & METHODS CONCLUSIONS Literature Cited Palmer, M. A. & D. L. Strayer. 1996. Meiofauna, in Hauer and Lamberti (eds), Methods in Stream Ecology. Academic Press. Pennak, R. W. 1940. The ecology of the microscopic metazoa. Ecol. Monogr. 10(4):5539-611. • Colonization complete by week 1: Invertebrate abundance in treatment and ambient samples not significantly different • No significant difference among treatments • Harpacticoids and cyclopoids appear to colonize epibenthically: higher abundance in epibenthic tubes • Oligochaetes and aeolosomatids appear to colonize endobenthically: higher abundance in endobenthic tubes • Tardigrads, ostracods, and chironomids appear to colonize both epibenthically and endobenthically: no difference in colonization between treatments • Meiofauna community in the hydropsammon exhibits both stability and resilience • We adapted methods from Palmer & Strayer (1996) • for recolonization of hyporheic invertebrates in lake • sediments. • 50-m-mesh panels, 50 ml tubes • Sediments defaunated by oven drying at 120C for 4 h • Azoic sediment packed into treatment tubes with organic material intact (2% OM by wt) • Randomized block design (treatments randomly assigned), blocked by time: 0, 1, 4, and 8 week • Each time block: 5 replicates for each treatment. • Four ambient core samples collected when time block pulled • Sediment separated from organisms by elutriation through 63-m-mesh screen Ambient: Simple core sample Epibenthic: Open top, closed sides Endobenthic: Closed top, open sides Control: Open top, open sides