HR: 08:45h
AN: NB41B-02    [Abstracts]
TI: Habitat Complexity of Stream Leaf Packs: Effects on Benthic Macroinvertebrates and Leaf Litter Breakdown
AU: * Ruetz, C R
EM: ruetzc@gvsu.edu
AF: Grand Valley State University, 740 West Shoreline Dr., Muskegon, MI 49441 United States
AU: VanHaitsma, D L
EM: VANHAIDA@student.gvsu.edu
AF: Grand Valley State University, 740 West Shoreline Dr., Muskegon, MI 49441 United States
AU: Breen, M J
EM: breenmj@STUDENT.GVSU.EDU
AF: Grand Valley State University, 740 West Shoreline Dr., Muskegon, MI 49441 United States
AB: We investigated two attributes of leaf-pack complexity (i.e., leaf-pack mass and leaf surface area) on fish predation, colonization of benthic macroinvertebrates, and leaf breakdown rates in a coldwater Michigan stream. We manipulated three factors using a factorial design: fish (exclusion or control cage), leaf-pack mass (1, 3, or 5 g dry mass), and leaf surface area (<7, 7-10, or >10 cm leaf width). Acer leaves were fastened into leaf packs. Exclusion cages had mesh on all sides; control cages lacked mesh on two sides to provide access to fishes. Two replicate leaf packs were randomly collected after 25-31 d from two sections of the stream (n = 4). Common shredders were Gammarus, Pycnopsyche, and Lepidostoma. We did not detect a significant effect of fish predation on benthic macroinvertebrates or leaf breakdown (i.e., mass loss). Colonization of benthic macroinvertebrates appeared proportional to leaf-pack mass but was unaffected by the surface area of leaves. Leaf breakdown was more rapid among leaf packs with fewer leaves (i.e., leaves with large surface area and leaf packs with low mass) and greater numbers of shredders. We suspect that physical fragmentation is the primary mechanism for higher breakdown rates among leaf packs with fewer leaves.
DE: 4239 Limnology
DE: 4804 Benthic processes/benthos
DE: 4817 Food chains
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly