PARENT SESSION
Poster Session 3: Aquatic Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 210 D, Level 2, Palais des congrès de Montréal

Temporal and spatial changes in macrophyte composition in a shallow turbid lake.

Lyon, Jonathan¹, Berg, Lauren^*,1, ¹ Merrimack College, North Andover, MA

ABSTRACT- The zonation of plants in freshwater systems is a well known phenomenon and can be influenced by several factors, including bottom topography, sediments, water column turbidity and light attenuation. In addition, vertical and horizontal zonation can vary temporally. In the current study, we investigated macrophyte assemblages and the linkage between assemblages and spatial patterns in macrophyte distribution over 2-years in a shallow, turbid lake. The study site was located in North Reading, MA USA in the North Eastern Coastal Zone Ecoregion. The specific study objectives included: comparing species richness, diversity and overlap between 2002 and 2004; analyzing the relationships between depth and sediment organic matter content with macrophyte abundance; comparing macrophyte assemblages and community patterns between years using multivariate statistical techniques; and use of GIS to quantify the distribution of macrophytes between years. Macrophytes were sampled in both 2002 and 2004 along transects located at discrete depths across the littoral zone. The results show that macrophyte diversity increased from 2002 to 2004 while overall mean abundance decreased. There was a significant decline in Cabomba caroliniana abundance, which could account for the increase in diversity. Multivariate ordination analyses indicated the lack of distinct macrophyte assemblages or discernible community types in either year. GIS analyses reveal shifting patterns of abundance in all species between years. Detailed analysis of the spatial distribution and density of aquatic macrophytes can be coupled with macrophyte composition data to provide a more robust assessment of macrophyte community patterns and relationships as well as macrophyte-substrate relationships.

Key words: macrophyte, shallow lake, community, spatial patterns