PARENT SESSION
Oral Session #37: Aquatic Ecology: Macrophytes. Presiding: J. Titus.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Hall of Ideas I.

Hydrogeomorphic influences on macrophytes as habitat in Great Lakes coastal wetlands.

Trebitz, Anett¹, Anderson, Richard¹, Taylor, Debra¹, ¹

ABSTRACT- We used rapid survey techniques to map submerged, floating, and emergent vegetation in 10 coastal wetlands of Lake Superior. Density and structure of plant beds in "bay", "main channel", and "side channel" areas was evaluated from cover indices and presence/dominance by growth form. There were significant differences in cover and growth form composition among fluvial zones; bays had the most cover and structural diversity, and main channels the least. Bays and side channels had denser submergents and were more likely to have tall, dissected forms (e.g., Myriophyllum), ground-cover forms (e.g. Elodea), and large-leaved Potamogetons. Bays and side channels also had more floating leaved cover, with big-leaved (Nuphar), ribbon-leaved (Sparganium fluctuans), and floating-leaved Potamogeton forms more likely present. Density of fringing emergent vegetation did not differ among fluvial zones, but the fringe was widest in bays. Main channels were dominated by "spikey" forms (sedges, rushes) while side channels and bays were dominated by "lance-leaved" forms (Sparganium, Typha) or dicots (e.g., Sagittaria). We also measured dissolved oxygen and water flow rates in wetland fluvial zones. Microflows and DO were somewhat higher in main-channels than off-channel areas, and were substantially higher in wetlands with larger stream and lake inputs. Differences in water quality and plant structure among wetland fluvial zones translate into differences in habitat for fish and invertebrates. The distribution of fluvial zones and habitat depends on wetland type and tributary size.

KEY WORDS: coastal wetlands, macrophytes, habitat, classification