Variation in Invertebrate and Fish Communities Across Floodplain Ecotones of the Altamaha and Savannah Rivers

Abstract

In floodplains of large rivers, different ecotones-zones of transition between adjacent ecological systems-develop where the river and uplands interact with the floodplain. Unique communities of invertebrates and fish may develop in each of these ecotones and in the floodplain interior. In our study, we sampled the river-floodplain ecotone, the upland-floodplain ecotone, and the interior of floodplains of the Altamaha and Savannah Rivers, Georgia, USA to assess how water quality, invertebrate community structure, total invertebrate abundance and biomass, and fish abundance and species richness varied across floodplains. In terms of water quality, electrical conductivity was greatest in the river-floodplain ecotone, while pH and temperature did not vary among sites. Nonmetric multidimensional scaling ordination indicated that overall invertebrate community composition across the floodplain was similar, and was dominated by wetland organisms that likely reside permanently on the floodplain. Total abundance and biomass of invertebrates was greater in the river-floodplain ecotone than the upland-floodplain ecotone, with levels in the floodplain interior being intermediary. Fish abundance and species richness was greater in the river-floodplain ecotone than other sites. Managers should consider lateral variation in invertebrate and fish assemblages across floodplains when planning management of river-floodplain ecosystems.

Decreasing Richness And Biomass During A Flood Pulse Observed In A Southeastern US Coastal Floodplain Following A Multi-Year, Supra-Seasonal Drought

“…The assemblage that was found in this study were predominantly obligate wetland occupants that consisted mostly of organisms that were desiccation-resistant organisms able to survive in soil or leaf litter and lentic organisms that inhabit permanently inundated areas. Our results are consistent with other studies conducted in southeastern US oodplains (Batzer and Wissinger 1999;Reese and Batzer 2007;Bright et al 2010). These ndings highlight the importance of adaptation to a changing environment as a key mechanism for survival, especially with the increasing prevalence of extended drought and a rapidly changing climate (Lytle and Poff 2004) The high degree of overlap in communities during both years of this study suggests the potential for biotic homogenization.…”

Comparison of a wood sampler for macroinvertebrate bioassessment of non-wadeable streams in the southeastern coastal plain

“…Although the sites sampled in this study are all within the same ecoregion, the Savannah and Ogeechee might be different enough to account for the differences in colonizing communities observed. The Ogeechee River exhibits natural flood pulses in which the floodplain is regularly in contact with the river channel (Meyer et al 1997), whereas the Savannah River has a regulated flow regime and less variable flood pulses (Bright et al 2010) due to major impoundments along the river. Further, the Savannah River was channelized, with approximately 40 bends straightened and snags removed, which has changed its hydrology and channel morphology.…”

Influence of water quality, local knowledge and river–floodplain connectivity on commercial wild crayfish harvesting in the Atchafalaya River Basin

“…Previous studies have linked floodplain connectivity with elevated water quality, habitat diversity, and biodiversity in southern USA rivers (Sabo et al 1999;Pringle et al 2000;Bright et al 2010;Kaller et al 2011;Bonvillain et al 2013;Bonvillain et al 2015;Pasco et al 2016), although the effects of river connectivity can be overwhelmed where high spatial coverage of aquatic macrophytes, such as invasive water hyacinth, leads to decreased dissolved oxygen (Kaller et al 2015). Macrophyte-associated declines in water quality were likely not evident during this study because sampling occurred early in the growing season when plant density was low.…”