Seed Propagation Protocol for Wigeongrass (Ruppia maritima) (Mississippi)

Wigeongrass (Ruppia maritima), is a submerged aquatic vegetation (SAV) species that occurs in broad salinity zones from near freshwater (0.5 parts per thousand) to hypersaline (> 40 ppt) conditions (Kantrud 1991). Wigeongrass reproduces asexually and sexually; it produces enormous numbers of tiny seeds that are protected by sturdy coats. Its broad salinity tolerance and versatile growth strategies have made wigeongrass the most widely distributed cosmopolitan SAV species (Kantrud 1991, Green and Short 2003). In addition, this fast growing SAV can provide favorable conditions for growth of other SAV species that require stable habitat.

Often wigeongrass is the only SAV species that can be successfully established in transitional areas between freshwater SAV beds and the declining seagrass beds in many coastal wetlands (Cho et al. 2009). Methods to produce large numbers of wigeongrass transplanting units from seeds or vegetative segments have been developed in laboratories and suggested for potential use in SAV restoration (DeLeon et al. 1997, Ailstock and Shafer 2006). However, the practical use of this plant in restoration has been underappreciated owing to large stochastic variation in its coverage and the shallow root/rhizome structures. The conventional harvesting and transplanting methods using plugs, sprigs, and staples have had limited success in wigeongrass restoration. Moreover, growing a large number of transplanting units requires a large space, advanced facilities, and trained personnel to house and maintain large (500 L) water tanks with recirculating systems and controlled environmental conditions. However, seed collection, storage, and germination do not have such demanding requirements. Therefore, restoration practitioners with SAV nurseries can involve volunteers. The hands-on participation will improve public perception of the importance of SAV habitat and restoration.

Table 1.

Collection, storage, viability, and germination rates of wigeongrass (Ruppia maritima) based on accumulated data (2001–2009) on phenology, biomass, seed production, and effects of seed pretreatments (stratification). The probability reflects pure chance likelihood with nondiscriminating analysis. Viability was tested using the tetrazolium red method (Cho and Sanders 2009).

Here, we report recent developments in restoration of SAV habitats using wigeongrass seeds from the coastal habitats of Mississippi and Louisiana in the northern Gulf of Mexico. The seeds require less labor and room to harvest, handle, transport, and store than whole plants. Also, collecting only reproductive shoots for seed harvest preserves most of the plant intact in the natural beds and causes less disturbance.

Based on our research, approximately 30% of the seeds can stay viable one year after maturation owing to inherent or induced dormancy (Cho and Sanders 2009). We present a simple procedure to collect, transport, sort, pretreat, and germinate wigeongrass seeds (Table 1). The users of the protocol need minimal preknowledge, skills, or special equipment. The information presented in Table 1 can be used to plan labor needs and number of seeds to be collected in order to produce a given number of seedling units.

Volunteers will initially need help from an expert and may require a permit to collect SAV, as well as a boat to locate and access natural wigeongrass beds. Wigeongrass beds are known to display significant seasonal and annual variations in size and location; the probability of locating substantial beds is 60%, even with expert assistance (Table 1). For example, the abundant wigeongrass beds in our biennial SAV survey sites at the Grand Bay National Estuarine Research Reserve, Mississippi, can completely disappear in the late fall and winter months (Cho and May 2008). Some wigeongrass populations in tropical and subtropical habitats also display two growing seasons per year (Cho and Poirrier 2005). Therefore, knowing the phenology of local populations will improve the probabilities of seed collection.

Wigeongrass usually grows in shallow waters up to 1.2 m deep, so the plants can easily be collected by wading in the water. Seed production time is of limited duration and varies from location to location; further, seeds are easily detached from stems by strong waves and storms, so that only 20% of collection trips will find substantial amounts of seeds available for harvest.

The plant parts containing seeds should be hand-collected, leaving...