Date of Award

1-1-2013

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

First Advisor

John J. Hutchens, Jr.

Second Advisor

Vladislav Gulis

Third Advisor

Kevin S. Godwin

Abstract

Interactions among macroconsumers (predators and large omnivores) and detritus breakdown are poorly understood on river floodplains. I evaluated the impact of macroconsumers on leaf breakdown, macroinvertebrate abundance and biomass, and fungal biomass on the Great Pee Dee River floodplain using exclosures in 6 wetlands. Sweetgum (Liquidambar styraciflua) leaves were held in mesh bags and in leaf packs. After 301 days, breakdown rates (k) were low in all treatments (k < 0.003 day-1) and did not significantly differ. Fungal biomass also did not significantly differ between treatments nor did overall macroinvertebrate abundance or biomass. Collector-gatherer invertebrates were significantly more abundant in treatments open to macroconsumers in mesh bags (P<0.001). Shredders had significantly higher biomass in packs held in exclosures closed to macroconsumers (P=0.048). Lack of rain limited stream-floodplain connectivity so a second, shorter study was done in one flooded wetland. After 98 days, pre-conditioned leaves in mesh bags open to macroconsumers had significantly higher breakdown rates (k = 0.0078 day-1) than those closed to macroconsumers (k = 0.0058 day-1; P= 0.050). Fungal biomass did not significantly differ between treatments. Total macroinvertebrate abundance (but not biomass) was higher in mesh bags open to macroconsumers (P=0.014). Scrapers and predators were significantly more abundant in mesh bags opens to macroconsumers (P=0.001 and P=0.004, respectively) than those closed to macroconsumers. These results indicated macroconsumers had a larger impact on litter breakdown in wet floodplain wetlands than in dry ones.

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