CICEET Progress Report for the period 9/01/01 through 3/01/02

Project Title: Sediment Recycling: Marsh Renourishment Through Dredged Material Disposal
Principal Investigator(s): Lynn A. Leonard, Martin H. Posey, Troy D. Alphin, Lawrence B. Cahoon, Richard A. Laws

Accomplishments
Scheduled Tasks:

• Vascular plant surveys conducted in August and October 2001, and January 2002.
• Analyses of vascular plant data collected from May 2000 to October 2001.
• Winter water level surveys conducted from January 15th - February 15th, 2001.
• Soil geochemistry measurements collected in September and November 2001.
• Preliminary analyses of soil geochemistry measurements collected from January 2001-December 2001.
• � Conducted fourth "post sediment placement" sediment trap survey in November 2001.
• Benthic biomass samples collected monthly from August-October 2001.
• Analysis of benthic biomass samples collected from November 2000 to June 2001.
• Collection of microalgal taxonomy samples in August and November 2001.
• Preparation and processing of microalgal samples for taxonomy is ongoing.
• Taxonomic identification of microalgae is ongoing.
• Monitoring of "pulsed sediment" experiments and subsequent monitoring of geochemistry and vascular plant biomass.
• Processing of benthic infaunal cores collected in May 2001.
• Updated web page (URL: www.uncwil.edu/people/lynnl/ciceet.htm)

Progress on Tasks

• Data collection and analyses have generally proceeded on schedule
• Results were presented by two graduate students at the Estuarine Research Federation Meeting in October-November 2001 in St. Pete Beach, FL. Alex Croft gave the presentation entitled: ". The Effects of thin Layer Disposal of Dredged Material on Tidal Marsh Processes" and Gina Panasik gave the presentation entitled: "Deteriorated Marsh Ecosystems: Can the Addition of Inorganic Sediment Increase Benthic Microalgae Biomass "
• Two published abstracts resulted during the current progress period (copies available upon request):
  1. Panasik, G.M. Deteriorated Marsh Ecosystems: Can the Addition of Inorganic Sediment Increase Benthic Microalgae Biomass. 16th Biennial Conference of the Estuarine Research Federation, Conference Abstracts, 4-8 November, St. Pete Beach, p. 105.

  2. Croft, A. and L. Leonard. The Effects of thin Layer Disposal of Dredged Material on Tidal Marsh Processes. 16th Biennial Conference of the Estuarine Research Federation, Conference Abstracts, 4-8 November, St. Pete Beach, p. 30.

Difficulties Encountered
We are now in the final phase of this project and are now compiling and analyzing our results. Things have been progressing very smoothly and we have encountered very few difficulties over the last six-months of this project. Our biggest problem remains the lag time associated with identification of microalgal taxonomy as this is a very time consuming process. The boardwalks at the study site have begun to deteriorate thus limiting site accessibility. The "Hogs Hair" filters emplaced over low areas appear to have achieved the desired effect and reduced site degradation by reducing flow in areas subject to channelization. We are interested in now examining surface hydrology at our sites due to our manipulations. We may expand the project over the time that is left to incorporate some flow analyses. This may require the purchase of additional supplies and equipment.

Anticipated Success in Meeting Project Objectives in Scheduled Project Period
We are on track to complete project objectives within the project period.

Preliminary Results
Vascular Plant Data
Vascular plant data have been collected bi-monthly since June 2000. Preliminary plant density data are summarized in Figure 1. Throughout the first growing season, stem densities in the deteriorated sites were lower than those in the non-deteriorated sites. During the second growing season, stem densities increased in the treated deteriorated sites while the densities in the deteriorated control area remained constant. In the non-deteriorated sites, stem densities in the first and the second growing season are similar. Over time, stem densities have become more uniform for all sites. No clear relationship between stem density and treatment seems apparent. These results, however, have not yet been examined statistically. As expected, the number of live shoots per square meter decreased in the winter and increased in the summer.

Water Level
The second water level monitoring effort was completed in August 2001. Four RDS WL-40 water level recorders were placed in each of the four treatment sites for a one month period. Each instrument measured and recorded water level once every six minutes. We are in the process of analyzing these data and linking them to survey data.

Sediment Geochemistry
Redox potentials have been measured bi-monthly in each of the three treatment areas within each of the four sample plots since August 2000. Additional measurements have been collected in the control areas. Average Eh profiles from August 2000 to September 2001 are shown in Figure 2. In general, the sediments in the non- deteriorated sites are more oxygenated then the deteriorated sites. The amount of placed sediment also seems to affect Eh. In all of the deteriorated and non-deteriorated sites, the most oxygenated profiles were always correlated with the thickest treatment. Further, a more reduced Eh profile was associated with the thin treatments and the non-treated controls.

Sediment Traps
Quarterly measures of sediment deposition using petridish sediment traps have been completed. Analysis of these data indicate that deposition in deteriorated sites following placement of dredged material continues to exceed deposition in non-deteriorated sites. These trends are consistent with those documented prior to sediment placement. In addition, sediment accumulation measured in the winter months remain almost one order of magnitude lower than deposition rates measured in the fall. This seasonal pattern is consistent with deposition rates measured in other natural marsh systems.

Benthic Biomass
Monthly benthic biomass sample collection has been completed. Samples collected through October 2001 have been analyzed for benthic chlorophyll production ( Figure 3, Figure 4). In general, the data show a drop in benthic microalgal biomass immediately after sediment additions, followed by a quick and large rebound. This period was followed by a period of fairly stable biomass level, except for the very cold period in December, 2000. These data are in general agreement with microalgae data previously collected near the study site.

Microalgal taxonomy
All of the microalgal samples have been collected for a total of 165 samples . The samples are now in various stages of preparation and analysis. While identification of some samples has occurred, many samples have been prepared to the slide stage and are awaiting microscopic analysis. Other samples are still in the cleaning stage. Samples collected in August and November 2001 have not yet been processed.

Benthic invertebrates
Benthic core samples were collected in late June/early July (all samples collected within a two week window) allowing the plots time to recover from the initial act of sediment addition, with a second sampling in May of 2001 to evaluate possible effects of sediment addition on the infaunal community. During each sampling period plots were sampled at the level of maximum addition (~4 in.), at an intermediate addition (~2 in.), and at minimal addition (<1 in.), using standard 10 cm diameter X 15 cm deep benthic cores. All organisms greater than 500 micron were removed from the sample and identified to lowest possible taxon (in most cases species).

Preliminary results indicate that both degraded and non-degraded plots are dominated by the same general taxa (Capitellid and Nereid polychaetes). This is as we predicted because of the close proximity of the plots to one another and the fact that both of these groups are common marsh residents. Capitellids are primarily deeper burrowing, deposit feeding taxa. Nereids, however, are both free living and tube dwelling (depending on the individual species) and likewise have a variety of feeding mode (predatory, deposit feeding, and grazers). The overall abundance of these organisms does seem to be reduced in the areas of maximal sediment addition in both degraded and non-degraded plots. We are currently focusing on treatment-sediment addition interactions to see if the infaunal communities recover at similar rates or if there is a change in the numerically dominant taxa between degraded and non-degraded plots at one year following addition.

Tasks and activities for next reporting period

Tasks for the next reporting period

• Complete statistical analysis of all results
• Complete textural and compositional analyses on sediment samples
• Complete laboratory analysis of benthic biomass samples, forward representative specimens for outside verification, and conduct statistical analyses
• Continue microscopic analyses for microalgal taxonomy (i.e. species identification and counting)

Work plan to accomplish tasks
The project currently employs two graduate students and two undergraduate students who assist with data collection, sample preparation, and analyses. One additional graduate student, currently funded on a Teaching Assistantship by UNCW, also works 10-15 hours per week on the project.

Concerns or difficulties
None

Expenditures
Expenditures met expectations for the work accomplished to date.