PARENT SESSION
Oral Session # 15: Wetland Ecology I: The Everglades and Southern Wetlands.
Presiding: J Chick
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 101.

Macroinvertebrates in the Florida Everglades: Community-level observations of the effects of hydroperiod and nutrient enrichment.

Smith, Shawn^*,1, Trexler, Joel¹, ¹ Department of Biological Sciences, Miami, Florida, USA

ABSTRACT- The extensive floating periphyton mat and its associated invertebrate community are an integral part of the Everglades food web. No published studies have directly sampled or characterized this community, so its distribution and response to variations in the physical environment are poorly understood. In this study we sought to describe the response of both the floating periphyton mat and benthic macroinvertebrate communities to nutrient enrichment and variation in hydroperiod. Here we sampled sites at two levels of phosphorus enrichment (ambient and enriched) and three hydroperiods ("short": <200 days since last dry-down; "long": >400 days since last dry-down; and "very long": >4000 days since last dry-down) in a factorial design. This was replicated in two different geographic areas of the Everglades separated by water control structures ("very long" sites were only available in one area). We found that community composition varied with both enrichment and variation of hydroperiod, and that these effects were different in floating mat and benthic communities. We noted almost a three-fold increase in the total density of invertebrates in the floating mat with enrichment. We also observed a significant interaction between hydroperiod and enrichment. When short hydroperiod sites were enriched, they experienced almost a six-fold increase in the total number of invertebrates, with more than twice as many invertebrates as any other enriched sites. We feel that this dramatic increase in invertebrates at short hydroperiod, enriched sites may be the result of compounding top-down and bottom-up trophic interactions. Understanding this interaction and gaining a deeper understanding of the associated community dynamics will enable researchers to better identify trophic interactions and determine the impact of environmental stressors on this system.

Key words: macroinvertebrates, Everglades, periphyton, hydroperiod and nutrient