Why Restore Seagrass Beds?
Since the 1800s, approximately 80 percent of the seagrass coverage in Tampa Bay has been lost mainly due to human activities. Ninety percent of the seagrass loss occurred between 1950 and 1982. Seagrasses are both economically and environmentally important; therefore, existing seagrass beds need to be preserved and expanded. Restoration of Tampa Bay's seagrass beds will not only improve water quality, but will also benefit important fishery species such as snook, seatrout, and shrimp. Whether it is the relocation of an entire bed or the removal of random plugs from an existing bed, the use of donor beds is necessary for seagrass restoration at this time. Currently, we are working on a tissue-culture technique, micropropagation, that could provide sustainable stocks of seagrass for restoration projects without causing extensive damage to existing seagrass beds.
What is Micropropagation?
Micropropagation is a way to clone plants axenically (sterile). Terminal buds collected from branches of mature plants are surface sterilized and placed in test tubes containing a specific nutrient medium. The different media we are experimenting with usually contain a carbon source, vitamins, plant hormones and antibiotics. Plantlets grown from buds of the same plant, barring mutation, will be clones (i.e., genetic replicates) of the plant from which they were cut. Once we are able to maintain rapidly multiplying plant stocks in the lab, we can use them as a source for additional micropropagation or subculturing. Subculturing involves dividing sterile plantlets into smaller segments and growing plants from these pieces. This is how we grow Widgeon-grass (Ruppia maritima) in the lab, and we are in the process of developing this technique for Shoal-grass (Halodule wrightii). Widgeon-grass is the easiest seagrass to micropropagate; other species, such as Shoal-grass (Halodule), Manatee-grass (Syringodium filiforme) and Turtle-grass (Thalassia testudinum), are increasingly difficult. We are focusing on one species at a time.
Why Use Micropropagation?
Compared to standard nursery techniques, micropropagation has the potential to produce more plants in less time. Fewer stock plants are needed because an explant can supply a great amount of material from which clonal material can be subcultured. Also, not having to rely on seeds and other propagation methods ensures greater uniformity in plants produced. Clones can be screened for different attributes and used for specific applications, or genetic variability can be assured by mixing different clonal strains in restoration projects. Another advantage to micropropagation is the contamination-free condition of the plants produced and the ability to produce microbially fit stocks that resist pathogens.
Seagrass Planting Techniques
Micropropagation will be the key to establishing non-destructive seagrass restoration and mitigation. Traditionally, seagrass has been planted by hand. Many materials have been used as substrates for rooting and anchoring plantlets. These include peat pellets, peat pots, and coconut-fiber mats. Success rates with hand planting have been variable. A new method using a boat with a planting wheel is being developed. We are developing protocols to transfer lab-produced seagrasses to the field for mechanical planting. This technique will reduce damage to the plantlets during transplantation, increase the planting rate, and cause less disturbance to sediment structure.