Macroinvertebrate Production in a Southeastern United States Blackwater Stream

Macroinvertebrate production was studied by replicated monthly sampling of five different substrate types at three sites in a second—order South Carolina blackwater stream. Both community—level and species—specific production in the major habitats found above, within, a below a swamp were determined. In addition, total stream production at the three sites was determined using data on habitat availability and habitat—specific production. Production varied among habitats at each site. Production on snags was at least twice as high as that found in any other habitat. Production in the muddy stream banks was higher than in sandy, main channel sediments, but was similar to levels found in the silty main channel sediments within the swamp. Production in leaf packs caught on snags was the lowest found in any of the habitats. High production on the snags was due to filter—feeders and collector—gatherers. The hydropsychid caddisfly Macronema carolina (dry mass of 4.90 g°m — 2 °yr — 1 ) dominated upstream production on the snags, while the chironomid Tanytarsus sp. was the main filter—feeder on snags within and downstream of the swamp. Collector—gatherers dominated production in the other habitats. Highest production in all habitats was found above the swamp. Filter—feeder production, which was lower within and below the swamp, exhibited the greatest site differences. Total annual stream production, incorporating production from all habitats adjusted according to habitat availability, dropped from 4.11 g/m 2 at the upstream site, to 3.09 g/m 2 within the swamp, to 1.96 g/m 2 below the swamp. The main channel sediments, which accounted for 44, 39, and 42% of production at the three sites, respectively, supported the greatest proportion of total macroinvertebrate production of any habitat. Snag production contributed 32, 35, and 28% of total production at the three sites. Total production from this habitat and from the main channel sediments decreased within and below the swamp. From 40 to 53% of total stream macroinvertebrate production was due to collector—gatherers (especially Polypedilum digitifer, Eurylophella doris, and Tubificidae), while filter—feeders accounted for 13—34% of total stream macroinvertebrate production. Shredders accounted for <5% of total production at each site within this fully canopied, deciduous forest headwater stream.