CICEET Progress Report for the period 9/15/04 Through 3/15/05

Project Title: Mitigating the effects of excess nutrients in coastal waters through bivalve aquaculture and harvesting
Principal Investigator(s): Hauke Kite-Powell, Dror Angel, Heidi Clark, Kevin Kroeger, Bill Walton, Di Jin, and Porter Hoagland

Figures

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Tables

Table 1

• Model development:
  • review and revision of model structure and preliminary results
  • application of 2004 field work data to bio-geophysical model
• Field work:
  • on-bottom and cage growout experiments
  • nitrogen cycling sampling and analysis
  • shellfish sacrifice and tissue analysis

Progress on Tasks
Review and revision of model structure and preliminary results: Model development is complete. Review and revision will take place in spring 2005 pending complete analysis and incorporation of 2004 field work results.

Application of field work data to bio-geophysical model: This work has been postponed pending complete analysis of 2004 field work data. Preliminary data from fall 2004 field work and sampling are described Preliminary Data below.

Growout experiments: Following sediment sampling in the late summer of 2004, the oysters were moved to deeper water in Waquoit Bay for the winter. The quahogs were left in place at the experiment site. Data on number of individuals in representative plots, mortality, and shell length were collected at the time the oysters were moved to deep water (November 2004) ­ see Preliminary Data below. We plan to restore the oysters to the experiment site in April 2005.

Nitrogen cycling sampling and analysis: Sediment samples were taken at the experiment site in September 2004, and analyzed for denitrification rates, carbon and nitrogen content, and grain size. Preliminary data are shown below.

Shellfish sacrifice and tissue analysis: Shellfish sacrifice and tissue analysis has been postponed to 2005 to allow for consistent continuation of field work during the 2005 growing season.

Difficulties Encountered
There is evidence of substantial quahog mortality in the plots, apparently from a species of shellfish drill (see Preliminary Data below). This will require us to make adjustments in the analysis of quahog plot denitrification data sets, but should pose no other problems.

Anticipated Success in Meeting Project Objectives
We anticipate no difficulties meeting the project’s objectives in the scheduled period. It is likely that we will want to continue the project beyond its scheduled conclusion to capture information on the effect of shellfish size/age on nutrient removal. However, this should not interfere with the timely conclusion of the CICEET project.

Project Objectives for Next Reporting Period

Preliminary Data
Table 1 summarizes results of shellfish growth monitoring at the beginning of the field work season. These early results suggest a significant density effect on shellfish growth rates for both oysters and quahogs.

Using GLM on the quahog size data, there was a significant effect of density (P = 0.025, numerator df = 3, denominator df = 10) on growth. Using the Fischer’s LSD post-hoc pair-wise comparison:

• Average shell length in the 100/m² treatment was greater than the average shell lengths in the 500/m² and the 2,000/m² treatments (P < 0.02); and
• Average shell length in the 1,000/m2 treatment was greater than the average shell length in the 2,000/m² treatment.

Using GLM on the oyster size data, there was a significant effect of density (P = 0.01, numerator df = 3, denominator df = 16). Using the Fischer’s LSD post-hoc pair-wise comparison:

• Average shell length in the 100/m² treatment was greater than the average shell lengths in the three other treatments (P < 0.03).

Shellfish density and mortality
As Figure 1 shows, oyster lot size as measured in sample plots in the fall of 2004 closely tracks the intended (nominal) densities; and mortality among oysters has been negligible. Among the quahogs (Figure 2), significant mortality (based on observations earlier in the year, largely due to drills) has reduced the actual the actual live densities by about half from nominal (intended) densities, and the 2,000/m² plots appear to have either not received the intended number of individuals at seeding, or seen significant migration out of the plots. We will make adjustments for actual (observed) density in the final analysis of denitrification results.

Denitrification Rates
Figure 3 and Figure 4 show preliminary results from denitrification rate measurements for sediment samples for oyster plots, and Figure 5 and Figure 6 show preliminary results for quahog plots, for the July and September 2004 sampling sessions respectively. Final analysis of these data is still pending.

Tasks and activities for next reporting period

Tasks for the next reporting period
Scheduled tasks for the reporting period were:

• Model development:
  • application of field work data to bio-geophysical model
  • review and revision of model structure and preliminary results
• Field work:
  • redeployment of oysters from deep water to experiment plots, and continuation of on-bottom and cage growout experiments
  • nitrogen cycling sampling and analysis (July/Aug 2005)
• Report production and dissemination

Work plan to accomplish tasks
We plan to return the oysters to the experiment plots in April, and to conduct another sediment sampling session in July or August of 2005. Also during the spring of 2005, we will complete analysis of 2004 field work data and integrate results of field work with the model.

Concerns or difficulties
No significant difficulties are expected. Because we will conduct a final sediment sampling session near the scheduled end of the project (August 2005), we would like to obtain a no-cost extension to the end of 2005 (December) to complete data analysis, model work, and report writing and dissemination.

Expenditures
Expenditures to date are largely in line with expectations.