Decomposition, riparian vegetation and macroinvertebrate community in re-flooded resacas: Looking at potential indicators of system stability

Background/Question/Methods

Freshwater wetlands in the Lower Rio Grande Valley of Texas are locally known as resacas. Resacas are remnants of the Rio Grande River channel that were naturally cut off by sedimentation and erosion of river banks.  Many are maintained as permanent wetlands through intermittent water pumping from the river. These resacas provide valuable habitat for fish, invertebrates, migratory birds and a diverse floral community in the otherwise semi-arid environment of South Texas. Despite the importance of the resaca ecosystems, very little is known about how the ecosystem functions. The objective of this study is to compare the macroinvertebrate community, vegetation community and decomposition patterns as potential indicators of resaca ecosystem stability. Decomposition, macroinvertebrate and floral communities will be sampled from, and compared between, a recently re-flooded resaca and two similar resacas in different stages of succession after re-flooding.

Results/Conclusions

Preliminary data for decomposition rates among resacas show that the fastest rates are found in the newest resaca with slowest rates found in the oldest resaca. Preliminary data for the macroinvertebrate community suggests that benthic community composition among sites is similar, with a greater density in the oldest resaca. From these preliminary results it is expected that the metrics derived from biological communities and processes will discriminate among sites, therefore their value as ecological indicators for these aquatic ecosystems will be assessed.