CICEET Progress Report for the period 8/01/00 through 1/31/01

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

1. Accomplishments
   
   
   1. Scheduled Tasks:
      
      
      • Vascular plant surveys conducted in August 2000, October 2000, and January 2001.
      • Preliminary analyses of vascular plant data collected from May 2000 to Januray 2001.
      • Winter water level surveys conducted from January 15^th - February 15^th, 2001.
      • Soil geochemistry measurements collected in August, October and December 2000.
      • Preliminary analyses of soil geochemistry measurements.
      • Conducted first six-month "post sediment placement" sediment trap survey in December 2000.
      • Benthic biomass samples collected monthly from August to December 2000.
      • Analysis of benthic biomass samples collected from February to June 2000.
      • Collection of microalgal taxonomy samples in August and October 2000.
      • Preparation and processing of microalgal samples for taxonomy.
      • Benthic invertebrate core processing and identification in progress.
      • Presented overview of the project as part of another CICEET funded project "Estuaries Live!". This was a joint effort facilitated by Dr. John Taggert of the NCNERR and Ms. Susan Lovelace also of NCNERR. We broadcast our overview live from the field via internet links. The North Carolina Coastal Resources Commission and several "on-line" elementary schools were the primary audience.
        
        
   2. Progress on Task

   As described in earlier progress reports, project initiation and data collection were delayed due to the permitting process required by North Carolina State law. Since project initiation, however, data collection and analyses have generally proceeded on schedule. Exceptions are described in the "difficulties encountered" section below

   3. Difficulties Encountered

      Very few difficulties have been encountered during the last six-months of the project. Our biggest problem has been a changeover in project personnel that has hindered our progress in completing the microalgal taxonomy portion of the project. In July 2000, the graduate student who had been working on this part of the project transferred to another institution. We have not been able to find a replacement to conduct these analyses and, at this time, are relying on undergraduate research assistants. Unfortunately, it has taken more time than expected to train these students to prepare and process the samples. Another difficulty has been site access using powered jon-boats. To alleviate this problem, we purchased a canoe which can be used to access the sites even at very low tides.

   4. Anticipated Success in Meeting Project Objectives in Scheduled Project Period

   Because initiation of our project was delayed due to the NC state permitting process, we applied for and were granted a no-cost extension to this project. We are confident that we will easily and successfully meet the project objectives within the revised project period.

   5. Preliminary data
      
      

Vascular Plant Data

Vascular plant data have been collected bi-monthly since June 2000. Preliminary plant density data are summarized in Figure 1. In general, stem densities in the deteriorated sites are lower than those in the non-deteriorated sites. There appears to be no relationship between stem density and treatment, however, these results have not yet been examine statistically. As expected, the number of live shoots per meter square decreased in the winter. We expect that any relationship between thickness of added sediment and plant density will not be apparent until well into the summer 2001 growing season.


 

Sediment Traps

Sediment deposition data collected using petridish sediment traps are shown in Table 1 (see Tables.xls). Mean sediment deposition data collected in October 2000 are shown in Figure 2. In general, deposition in deteriorated sites following placement of dredged material exceeds deposition in non-deteriorated sites. This same trend existed prior to sediment placement. Accumulation in the deteriorating sites following sediment placement has risen one order of magnitude over levels observed prior to fill placement. It is our contention that these measurements actually reflect sediment mobility rather than sediment accumulation. The higher rates observed in October may be due to background seasonal trends in sediment mobility associated with canopy die-back. Note that control values (areas not treated with sediments) also show an increase in sediment accumulation at this time. Within the deteriorated sites, areas overlain by the greatest thickness of dredged material show the lowest sedimentation rates. This may indicate that the increase in sediment grain size associated with sediment placement has decreased sediment mobility in these sites.






Sediment Geochemistry

Redox potentials have been measaured 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. The Eh profiles are shown in Figure 3. In general, the sediments have become more oxygenated at all sites between August and December 2000. Sediment placement appears to have had the greatest impact near the surface in the deteriorated sites when compared to the control. These data are still be analyzed.






Water Level

Four RDS WL-40 water level recorders have been placed in each of the four treatment sites. Each instrument measures and records water level once every six minutes. The instruments were deployed in early January and have not yet been retrieved from the field. Preliminary water level data will be included in the next six-month progress report.

Benthic Biomass

Benthic biomass samples have been taken at all project sites and analyzed for benthic chlorophyll production. Preliminary data are shown in Figure 4. Monthly sample collection was conducted for the four months prior to the addition of the dredged material. After the addition of dredged material, samples were taken twice a month during the months of May, June, July, and August 2000. Since August 2000, samples have been collected monthly. Benthic chlorophyll samples are taken using a 2.5cm diameter coring tube that collects approximately 20 mm of sediment. Samples are then frozen until analysis for benthic chlorophyll can be completed. Samples through June of 2000 have been analyzed.






Microalgal taxonomy

Accomplishments to date are shown in Table 2. The table shows all of the samples collected thus far and the state of preparation for each sample. Some samples have been prepared to the slide stage and are awaiting microscopic analysis. Other samples are still in the cleaning stage (e.g. October set). Two more sets of samples will be collected: one in the week of Feb. 19, 2001, and one set in early April depending on suitable tides. Those two sample sets will basically complete the one year sampling cycle because the first post sediment emplacement samples were collected in late May and early June,
2000.

 

Benthic invertebrates

Benthic infaunal samples were collected six weeks following the addition of sediment. This delay allowed some degree of site recovery due to the actual sediment addition process. While processing of these samples continues preliminary data shows some potentially interesting patterns. Predicted impacts, to infauna, varied based on the amount of sediment to the added. Minimal impacts were predicted for the areas with the least sediment addition while more negative impacts were predicted for areas with larger sediment addition. However even within samples from the "thick" sediment additions we have found infaunal assemblages. While we cannot at this time say what numerical impact sediment addition had on infauna, we do know sediment additions did not defaunate the underlying substrate.

1. Tasks and activities for next reporting period
   
   
   1. Tasks for the next reporting period:
      
      
      • Extend boardwalks at sampling sites
      • Identication of areas with the potential for channelization.
      • Place "Hogs Hair" filters over low areas to prevent channelization
      • Continue bi-monthly vascular plant surveys and begin statistical analysis of results
      • Conduct summer water level measurements
      • Continue bi-monthly geochemical measurements and statistical analysis of results
      • Conduct second six-month "post sediment placement" sediment trap survey
      • Collect sediment samples for examination of 6-month granulometry changes
      • Conduct textural and compositional analyses on sediment samples
      • Continue to collect monthly benthic biomass samples
      • Continue laboratory analysis of benthic biomass samples and conduct statistical analyses
      • Complete microalgal sampling and sample preparation for year 1
      • Begin microscopic analyses for microalgal taxonomy (i.e. species identification and counting)
      • Initiate statistical analyses once all samples have been counted
      • Continued processing and analysis of benthic infaunal samples.
      • Collection of the second set of benthic infaunal samples from all, for evaluation of recovery following a major period of recruitment.
        
        
   2. Work plan to accomplish tasks

      Sampling of various parameters described above will be conducted according to the schedule of tasks provided. 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.

      Some of the preliminary results will be presented at the Southeastern Sectional meeting of the Geological Society of America in Raleigh in April 2001. One of the graduate students funded by the project (A. Croft) will be giving the presentation entitled: "Effects of Dredged Material Disposal on Salt Marsh Processes".

   3. Concerns or difficulties

   As we approach the summer season, our greatest concern is site security. Last year, we felt that the edges of the sites were somewhat compromised by non-project personnel who visited the site. We have taken steps to reduce visibility of the site to nearby boaters and also taken steps to mitigate any damage near the site caused by curious onlookers (e.g. placed hogs-hair filters where vegetation has been trampled etc.).

   4. Expenditures

   Expenditures were slightly less than anticipated for the work accomplished to date.