CICEET Progress Report for the period 02/01/01 through 08/31/02
Project Title: Density-Dependent Effects on Grazing and Success from Seed Generated Seagrass (Zostera marina L.) Plants
Principal Investigator(s): Scott W. Nixon, Stephen Granger, Brian Maynard, and Malia Schwartz
In our previous progress report we outlined the following tasks for the last six months of this project;
- To collect 1.5 million seeds for the replanting and creation of seagrass habitat totaling 0.25 acres in Narragansett Bay. We received funding from the U.S. Navy to apply restoration technologies developed during the first years of this project. State environmental agencies required the Navy to remove marine sediment containing elevated concentrations of polychlorinated biphenyls (PCB), aromatic hydrocarbons and metals at McAllister Point, Newport, Rhode Island. The habitat mitigation plan included in the project required the backfilling of the dredged area with marine sediments and the replanting of any lost seagrass habitat. The opportunity to field test our underwater sled in a “real-case” mitigation program presented us with a unique opportunity, however the U.S. Navy could not provide funding for tasks deemed as scientific research or not essential to completing the mitigation plan. As a result, CICEET provided funds for a thorough monitoring and economic evaluation of our field trials of the sled (see CICEET project: Field Testing of a Mechanical Seeding Machine for the Propagation of Zostera marina L. from Seed: An Ecological and Economic Assessment).
- To double the number of tines (used to create furrows) and delivery tubes (used to place seeds into furrows), and thereby increasing the area planted by a single pass of the sled over the sediment surface.
- To investigate alternative gelling agents that avoid or reduce any increase in sediment respiratory rates. During our previous experiments we found that the organic content and depth of the redox layer in sediment effected the production of plant biomass (both above and below the sediment surface) and to a lesser extent the number of seeds that successfully germinated. There is evidence that persistent anoxia is detrimental to the successful propagation of seedlings from seed. During our first trials with the Knox gel media we noticed that sediment anoxia developed shortly after the seed/gel mixture was placed in a furrow. As a result we will investigate non-organic media such as sodium bentonite to determine if we can reduce the anoxia created by our traditional planting media of Knox gel.
- To complete a series of trial seeding experiments with the alternative gels. The experiments were conducted in sediment-lined boxes held in flowing seawater aquaria.
Progress on Tasks
- Over 1.7 million seeds were harvested from Ninigret Pond, near the eastern shore of Prudence Island and from Kings Beach in Newport, Rhode Island. After collection, flowering stalks were held in flowing seawater tanks for a minimum of six weeks allowing seeds to mature, ripen and be released form the attendant shoots. The harvested seeds were used in the Navy mitigation project, as well as aquaria experiments designed to test the effect of alternative gel agents on seed germination and seedling health.
- We collaborated with a local fabrication shop to redesign the manifold system on the sled and increase the number of tines delivering seeds to the sediment. The Design Machine Company (firstname.lastname@example.org) worked with our group to reengineer transition points in the manifold where tubing diameters change abruptly and seeds tended to lodge. We also increased the number of tines from four to eight to effectively double the delivery of seeds to the sediment. The redesign process also offered an opportunity to include a number of features for the quick disassemble and cleaning of the manifold system. A particularly useful feature when trying to purge the lines of one gel type before introducing another during field trials.
- Seeds were planted in sediment-lined boxes in late November 2001. All treatments were run in triplicate and included sediment taken from Coddington Cove and Prudence Island (identified as a possible restoration sites in the upcoming Navy project), and sediment from a local gravel pit. The terrestrial sediment was included as one of our planting media since there was a possibility that the depression in the McAllister Point seagrass bed, created when the contaminated sediment was removed from at McAllister Point, would be backfilled with similar material. We thought it proactive to test germination success in the gravel pit material in the advent it would be used as a substrate at McAllister Point, a location we were to test the planting machine.
We planted 52 seeds suspended in Sodium Bentonite, Cabosil, Agrigel and Knox gelatin in each of the triple treatments. In addition, we hand planted equal numbers of seeds as controls. Once seeded the boxes were placed in flowing seawater tanks and kept at ambient field temperatures.
There were no real difficulties in meeting the indicated tasks. In fact, our work with an engineer at the Design Machine Company was very productive and allowed for design considerations that we would not have normally considered viable or possible with our skills or University’s infrastructure.
Anticipated Success in Meeting Project Objectives in Scheduled Project Period
We have completed the proposed tasks with little difficulty. The seed stocks were used in the mitigation portion of the navy project, the changes in sled design have facilitated our field operations and our seeding experiments with alternative gel agents appear promising for increasing seed germination when compared to the Knox gel (planting media used in our first experiments).
Germination success of seeds hand planted or planted with various suspension gels. Seeds were planted on November 28, 2001 in sediment-lined boxes then placed in flowing seawater tanks and kept at ambient field temperature. Seeds were considered as successfully germinated if a viable seedling was produced. The results presented below were determined on May 5, 2002 Note: Knox gel used in our earlier work produced the lowest number of germinated seeds (See Figure 1).
Tasks and activities for next reporting period
Tasks for the next reporting period
This progress report is the last report on this project therefore we will not identify future tasks other than the construction of a final report. In addition we plan to present the results of this project at a special session hosted by CICEET the Restore America’s Estuaries (RAE) meeting in July 2003.
Work plan to accomplish tasks
We have produced an instructional pamphlet with step by step instructions on the collection and storage of seagrass seeds for environmental activist groups. Much of the work funded during this project is included in the pamphlet. This will facilitate the communication of our findings to interested groups and provide the foundation for our presentation at the RAE meeting.
We will also test sodium bentonite, cabosil and knox gel in replicated field plots at two sites during the fall of 2002 as part of our CICEET project (discussed earlier). Our aqauria tests indicate the potential of a three-fold increase in seed germination with the new gel types. We look forward to our first counts of seed germination in spring 2003.
Concerns or difficulties
We do not anticipate any difficulties in meeting the project objectives set for the up-coming reporting period.
We have had no problems staying with in the expected budget for this reporting period.