| Invertebrate communities from emergent plant zones common to two diked and two undiked marshes were compared during July 2006, in order to document differences in the potential prey base of avian fauna of Lake St. Clair deltaic marshes. Invertebrate samples were taken with a 0.5 mm D-frame dip net from the outer 1-2 m edge of the emergent plant zones dominated by Schoenoplectus acutus, Typha angustifolia, or the invasive form of Phragmities australis. Equal effort consisting of 3 minutes of sweep net collecting per sample was expended in order to quantify catch per unit effort (CPUE) differences in numbers between diked and undiked marshes for each plant zone. A total of 109,649 invertebrates were collected: 93,959 from diked marshes (3,758 per sample, N=25) and 15, 690 from undiked marshes (541 per sample, N=29). Thus, seven times more invertebrates were collected per sample from diked marsh samples than were collected from undiked samples (p=0.03, 2-way ANOVA) suggesting that the prey base for breeding waterfowl and other invertebrate predators is greater in diked marshes than in undiked marshes. I also tested Shannon's Diversity Index, evenness, and taxa richness. Shannon's Diversity and evenness were not significantly different, but taxa richness (p=0.05) was significantly greater in diked marshes compared to undiked marshes. Sorensen Similarity Index revealed that 77% of taxa were similar between diked and undiked marshes. There was no significant difference in the invertebrate community caused by plant zone or location. |
