95th ESA Annual Meeting (August 1 -- 6, 2010)

PS 31-68 - Physicochemical factors affecting species assemblages of freshwater snails in four lakes in croton watershed, Westchester County, NY

Tuesday, August 3, 2010
Exhibit Hall A, David L Lawrence Convention Center
Tami Cloherty, Biology, The Graduate Center and Lehman College, CUNY, Bronx, NY
This suburban ecology project examines four lakes located in the Croton Watershed in the New York metropolitan area.  The purpose of this study is to determine if species assemblages of benthic macroinvertebrates are affected by physicochemical factors and lake shore line development. While there have been some recent studies of the lakes, little has been done on the benthic fauna in the lakes.  This project will provide updated ecological information on conditions of these habitats and the benthic fauna that live there. 

Sampling occurred over two seasons from April through October of 2008 and 2009.  Samples were taken in a 0.25m2 area and placed in jars, three replicates per site about twice a month, depending on access to sites.  Samples were put into jars with 70% ethanol solution and 0.01% Rose Bengal to stain macroinvertebrates. Processing of samples was done using surgical trays, forceps, stereo and compound microscopes at La MER Lab at Lehman College.  Physicochemical parameters measured included: temperature, cloud cover, pH, DO, nitrates, phosphates, hardness (Ca2+ and total), TDS, conductivity and coliform testing. Gastropods were identified to species whenever possible, massed, shell length measured and stored in 70% ethanol.  Sediment analyses were conducted with standard brass sieves to identify soil types.  Filtration of sediment and loss on ignition studies were done to assess percent organic matter and carbonates in sediments. The central hypothesis is that the data will show a significant level of association between the physicochemical parameters of the lakes and the composition and distribution of gastropod populations and levels of shore line development. Based on the initial faunal survey, there are particular species assemblages of benthic organisms that favor similar microhabitats as particular gastropods and thus are frequently found in association with those snails.  

Preliminary results indicate that there are distinct species assemblages of snails in the lakes that appear to be associated based on physicochemical preferences.  Other benthic organisms favor similar microhabitats as these groups of gastropods and are frequently found in association with particular snails.  Species assemblages of benthic macroinvertebrates exhibit specific habitat preferences, with specific physicochemical preferences.  The degree of development along the lakeshore appears to be associated with the physicochemical parameters and could be associated with the benthic species assemblages present in the lakes.  Further study, including geospatial analysis using Arc GIS mapping software is planned to elucidate the interactions in this multivariate analysis of the lakes’ benthic fauna.