BENJAMIN WEIBELL

Research Interests: Community Ecology and Insect
     Production Dynamics
Entry into IGERT Program: Fall 2000
Graduation Date: May 2007 (Ph.D.)
Professional Address (September 2005):
      Benjamin Weibell, Assistant Professor
      Biology Department
      Anne Arundel Community College
      Arnold, Maryland 21012

Education:

Graduate Committee :

Dissertation Research

I propose to investigate the mechanisms of resilience for invertebrates that inhabit submerged wood in a free flowing medium-sized river. Specifically, I intend to look at how invertebrate drift, reproduction, and aestivation contribute to recovery of this community after a drying disturbance due to the natural rise and fall of the hydrograph. The overall contribution of this recovery to annual community production will be closely examined. These facets will be evaluated through season and against the intensity and duration of disturbance. The main objective is to provide a general model of recovery in a free-flowing system.

The research will include several field and laboratory experiments as well as field measurements of invertebrate drift. The success of this research is dependent on real-time monitoring of the hydrograph and a quick response time to any changes in discharge. The research experiments will be carried out over one year. Results from the proposed study will be valuable for river management and restoration of flow regime in other rivers.

Poster, North American Benthological Society, 2003 (in PowerPoint)
"Quantification of Habitat for Snag-dwelling Invertebrates: Incorporation into a Dynamic Model"


Study Site

The Sipsey River is found in the western portion of the state of Alabama in the Coastal Plain region. The Sipsey is a fifth order stream and can be described as a medium size river. It is a tributary of the Tombigbee River in the Mobile River system and runs completely unregulated for approximately 184 km before its confluence (McGregor and O'Neil 1992). The long and narrow catchment area of the Sipsey River basin is about 2043 km2. Discharge of this river is highly variable ranging from 2.5 m3/s to 566 m3/s. The mean annual discharge is about 25 m3/s. Discharge is highly correlated with precipitation events and appears to have a two-day lag time behind storms. Water levels can rise as much as a meter in one day from the effects of a single storm, but the rise is steady and not flashy. Precipitation in this area is evenly distributed throughout the year with approximately 142 cm/y. This continual precipitation throughout the year causes water levels to change constantly. Currents tend to be slow to moderate. Water spills over the channel bank into the floodplain at discharges exceeding 56 m3/s. The Sipsey has an extensive forested floodplain with a width of 1-3 km which floods most years in the winter for a few months when evapotranspiration is low and the response of river stage is high, but has been observed to flood in all seasons of the year. The floodplain is a mosaic of pools, sloughs and oxbow lakes. Channel substrate consists mostly of loose sand, some gravel beds and clay. Wood is the most stable substrate found in the channel and is abundant as has been found in other Coastal Plain rivers (see Wallace and Benke 1984).

The state of Alabama purchased a large plot of land (ca. 1,214 ha) immediately south of the USGS river gauging station, "Sipsey at Elrod-02446500", as part of the Alabama Forever Wild program. The land sits on the eastern side of the Sipsey and covers a large portion of the floodplain. This portion of the river will serve as the study site. This site is ideal because it provides us with access to the river, a relatively undisturbed portion of the river, and the USGS river gauging station immediately upstream. Data from the gauging station (e.g. discharge and river stage) can be obtained as real-time data via the internet on the USGS site (http://water.usgs.gov). Historical data from the gauging station is available from the same internet site for 57-y period of record. The study site is 31 km from the University of Alabama and the gauging station is essential for us to be able to respond to changes in the hydrograph.

RESEARCH QUESTIONS

• What is the depth-specific community composition and secondary production per area river bottom? If a pattern is found, can this pattern be related to the resilience of the community?
  
• What is the colonization potential and pattern of colonization over the course of a flooding event?
  
• What is the pattern and composition of drift over the course of a flooding event?
  
• What species are able to persist long-term through the desiccatioon period without leaving the wood and how does the recovery potential change with increasing duration of desiccation time?
  
• What are the evacuation rates and assemblage composition as wood is exposed for organisms with no adaptation to persist long-term during desiccation?
• What is the colonization potential of wood from eggs laid on desiccated snags?