<p> While environmental controllers of decomposition have been extensively studied, organic matter quality and biotic controllers of decomposition, such as detritivore preference and manipulation of detritus, are largely understudied. In the studies described in this dissertation, a range of biotic controllers of detrital dynamics in aquatic ecosystems are presented. Crayfish, as model shredders, produce a diverse pool of fine particulate organic matter (FPOM) through fragmentation of coarse particulate organic matter (CPOM) and fecal production in the laboratory. Crayfish process maple leaves at a greater rate than oak leaves, and produced a greater amount of FPOM from maple compared to oak. Crayfish-generated FPOM had lower C:N ratios and increased bacterial abundances compared to original CPOM. Further, hydropsychid caddisfly and simuliid blackfly larvae confer greater growth efficiency when reared on crayfish-generated FPOM compared to mechanically ground FPOM in the laboratory, indicating that crayfish increase bioavailability of FPOM. No differences in growth or metamorphosis of simuliid larvae were observed when larvae were lab-reared on crayfish-generated FPOM from CPOM of different tree species (<i>i.e.</i>, sugar maple, sycamore, or white oak) or different stream conditioning times (<i>i.e. </i>, 30 or 150 d). This suggests that crayfish processing reduces organic matter origin effects on bioavailability. Changes in macrophyte abundance in a tropical wetland due to competition and ecosystem management can affect litter availability and litter quality. In two field-based, replacement series experiments with floating-mat macrophytes (<i>Eichhornia crassipes</i> and <i>Neptunia oleracea</i>), no interspecific competition was detected. However, <i>E. crassipes</i> dominated experimental enclosure biomass through attrition. Decomposition rates were faster for <i>E. crassipes</i> litter compared to <i>N. oleracea</i> litter within enclosures, but no differences in decomposition rates were detected by floating-mat species composition. Both synergistic and antagonistic diversity effects were observed on decomposition dynamics in an experiment varying litter richness from one to five species. Additionally, cattail (<i>Typha domingensis </i>) eradication efforts lead to changes in the decomposition landscape within the wetland, as <i>E. crassipes</i> colonizes managed areas, and decomposition rates were slower for litter of <i>T. domingensis</i> compared to <i>E. crassipes</i>. The compounding effects of litter species, detritivore interactions, and anthropogenic impacts on organic matter dynamics illustrate that it is critical to consider ecosystem function in ecosystem management. </p>

Thesis (Ph.D.)--The University of Toledo, 2006. / (UnM)AAI3218587. Adviser: Daryl L. Moorhead. Source: Dissertation Abstracts International, Volume: 67-05, Section: B, page: 2328.