Leaf Litter Decomposition and Macroinvertebrate Assemblages Along a Longitudinal Gradient of the Ogeechee River in Southeast GA

Leaf litter decomposition and macroinvertebrate colonization were examined along a longitudinal gradient of a blackwater river in southeast GA. Leaf litter packs of Sweetgum (Liquidambar styraciflua) and Scarlet oak (Quercus coccinea) were placed at four sites along 25-km stretch of the Ogeechee River and retrieved at two week intervals for 56 days. Litter materials remaining in leaf packs were dried and weighted to estimate decay rates (-k) and macroinvertebrates collected in leaf packs were counted to estimate colonization. Decay rates varied little between leaf types (range -k = 0.011 – 0.022), with downstream sites yielding higher -k rates for both leaf types. The total number of macroinvertebrates found in leaf packs also varied little across sites and leaf types with oak packs yielding 171±50 (mean±SD) and sweetgum packs 132±82 (mean±SD) after 56 days. Our results suggest that leaf detritus can represent an adequate substrate for colonizing invertebrates in blackwater rivers and thus be an important source of fine particles as materials breakdown. Furthermore, differences in decay rates across our study sites are like explained by higher discharge rates in downstream sites.