Developing Best Practices in the Nursery Production of Spartina alterniflora in Coastal Georgia
Because of its critical role in salt marsh growth and maintenance, Spartina alterniflora is often used as a biological component in coastal salt marsh restoration projects, such as living shorelines. Research suggests that the use of local genotypes increases the success of restoration, due to adaptation to local conditions, with high genetic variation. However, there currently is no source for native S. alterniflora in Georgia, and most nursery producers create plant stocks through clonal propagation, which creates a population with low genetic variation. Furthermore, traditional methods for nursery production include sub-irrigation in freshwater in plant trays and the use of commercial fertilizers, which does not mimic natural marsh conditions plants will experience after transplantation into the marsh. The overall aim of this ongoing project is to develop best practices in the nursery production of native Georgia S. alterniflora from seed. To this end, optimum collection, storage, and germination conditions and alternative methods of seedling growth and plant maintenance have been explored.
Optimum Collection, Storage, and Germination Conditions
Best Time and Marsh Location to Collect Spartina alterniflora Seeds
M.S. Thesis, Alex Gregory, Justin Hinson, and Maygan Palacios
To determine the best time and marsh location for seed collection, fecundity data collected over 4 years (2019-2022) from three salt marshes in Chatham County was analyzed. Selected salt marshes varied in several factors, including proximity to the ocean and degree of human disturbance, and seeds were collected bimonthly during the reproductive season for Spartina alterniflora (September-November in coastal Georgia). Additionally, phenology (or reproductive status) of plants was assessed at two marshes in 2020 and 2022. Results showed greatest number of seeds per spikelet and viability at the marsh site furtherest from the ocean and with the least human disturbance. Additionally, there was greater overall seed production and greater viability later in the reproductive season. Taken together, these results suggest collecting seeds from marshes further from the ocean and with little human disturbance in mid- to late October to maximize seedling production.
The Effect of Salinity on Seed Viability and Germination for Spartina alterniflora
M.S. Thesis, Maygan Palacios
It is assumed that freshwater maximizes seed viability and germination in Spartina alterniflora, and consequently propagation protocols for other regions often suggest winter storage and germination of seeds in freshwater. However, natural salt marshes are brackish habitats, with salinities fluctuating between freshwater (~0 ppt) and seawater (30-35 ppt), and salinity may have a greater influence on seed viability and germination than perviously thought. The purpose of this research was to determine the effect of varying salinities (0, 10, 20, and 30 ppt) for winter storage and germination on seed viability and germination. Results showed significantly greater seed viability and germination in 0 ppt, suggesting that freshwater should be used for winter storage and germination to maximize seedling production.
Optimum Storage Vessels for Winter Storage and Germination Temperatures for Spartina alterniflora
M.S. Thesis, Justin Hinson (graduated Spring 2023)
To determine optimum storage vessels for winter storage, seed viability and germination was compared among seeds stored in plastic centrifuge tubes, glass scintillation vials, and Ziploc bags. Results showed significantly greater seed viability in Ziploc bags, but there was no difference in germination among storage vessels. Seeds were then placed into one of three temperatures (~30C, ~32C, and alternating day:night temperatures of 32C:24C) and germination was monitored. Results showed greater germination in alternating temperatures but this difference was not significant. The results of this research suggest storing S. alterniflora seeds in Ziploc bags for winter stratification and germination at alternating day: night temperatures.
Best Time and Marsh Location to Collect Spartina alterniflora Seeds
M.S. Thesis, Alex Gregory, Justin Hinson, and Maygan Palacios
To determine the best time and marsh location for seed collection, fecundity data collected over 4 years (2019-2022) from three salt marshes in Chatham County was analyzed. Selected salt marshes varied in several factors, including proximity to the ocean and degree of human disturbance, and seeds were collected bimonthly during the reproductive season for Spartina alterniflora (September-November in coastal Georgia). Additionally, phenology (or reproductive status) of plants was assessed at two marshes in 2020 and 2022. Results showed greatest number of seeds per spikelet and viability at the marsh site furtherest from the ocean and with the least human disturbance. Additionally, there was greater overall seed production and greater viability later in the reproductive season. Taken together, these results suggest collecting seeds from marshes further from the ocean and with little human disturbance in mid- to late October to maximize seedling production.
The Effect of Salinity on Seed Viability and Germination for Spartina alterniflora
M.S. Thesis, Maygan Palacios
It is assumed that freshwater maximizes seed viability and germination in Spartina alterniflora, and consequently propagation protocols for other regions often suggest winter storage and germination of seeds in freshwater. However, natural salt marshes are brackish habitats, with salinities fluctuating between freshwater (~0 ppt) and seawater (30-35 ppt), and salinity may have a greater influence on seed viability and germination than perviously thought. The purpose of this research was to determine the effect of varying salinities (0, 10, 20, and 30 ppt) for winter storage and germination on seed viability and germination. Results showed significantly greater seed viability and germination in 0 ppt, suggesting that freshwater should be used for winter storage and germination to maximize seedling production.
Optimum Storage Vessels for Winter Storage and Germination Temperatures for Spartina alterniflora
M.S. Thesis, Justin Hinson (graduated Spring 2023)
To determine optimum storage vessels for winter storage, seed viability and germination was compared among seeds stored in plastic centrifuge tubes, glass scintillation vials, and Ziploc bags. Results showed significantly greater seed viability in Ziploc bags, but there was no difference in germination among storage vessels. Seeds were then placed into one of three temperatures (~30C, ~32C, and alternating day:night temperatures of 32C:24C) and germination was monitored. Results showed greater germination in alternating temperatures but this difference was not significant. The results of this research suggest storing S. alterniflora seeds in Ziploc bags for winter stratification and germination at alternating day: night temperatures.
Alternative Nursery Production Methods
The Effect of Salinity and Microbial Activity on the Nursery Production of Spartina alterniflora
M.S. Thesis, Justin Hinson (graduated Spring 2023)
In traditional nursery production of Spartina alterniflora, plants are potted in some type of mixture that may include commercial sand, potting soil, and/or topsoil and maintained in freshwater. However, natural marsh soil contains myriad microbial communities that interact with plant roots and potentially increase plant growth in marsh soils. To examine the effect of the natural microbial community of salt marsh soil on S. alterniflora growth, seedlings were transplanted in pots with only potting mixture or potting mixture mixed with salt marsh soil. These seedlings were then either grown in freshwater or saltwater (at 13 ppt) to determine the effect of salinity on plant growth and the microbial community. Results showed increased growth in freshwater and in potting soil mixed with salt marsh soil. However, when interactions between treatments were further explored, it was found that plant growth was greatest in potting mixture mixed with salt marsh soil, regardless of the salinity treatment. These results indicate that inoculation with salt marsh soil increases plant growth in nursery production of S. alterniflora.
Nursery Production of Spartina alterniflora for Coastal Marsh Restoration Using an Aboveground Wetland Designed to Remediate Aquaculture Effluent
M.S. Thesis, Alex Gregory
Traditional nursery production methods for Spartina alterniflora include sub-irrigation with freshwater and the use of commercial fertilizers, which are not similar to the conditions in natural marshes. The aim of this study was to evaluate the production of native S. alterniflora for salt marsh restoration projects in Coastal Georgia using a constructed wetland designed for remediation of marine aquaculture effluent. It was expected that the constructed aboveground wetland would provide the growing conditions required for nursery production of S. alterniflora, such as sub-irrigation to ensure continual submergence of belowground, while mimicking several salt marsh growing conditions, such as saturated and potentially anoxic soil and an organic fertilizer source consisting of fish waste and organic debris. Results showed no difference in measured growth variables between traditionally grown plants and plants grown in the aboveground wetland, suggesting that S. alterniflora can be grown and maintained in an aboveground wetland designed to remediate aquaculture effluent.
The Effect of Salinity and Microbial Activity on the Nursery Production of Spartina alterniflora
M.S. Thesis, Justin Hinson (graduated Spring 2023)
In traditional nursery production of Spartina alterniflora, plants are potted in some type of mixture that may include commercial sand, potting soil, and/or topsoil and maintained in freshwater. However, natural marsh soil contains myriad microbial communities that interact with plant roots and potentially increase plant growth in marsh soils. To examine the effect of the natural microbial community of salt marsh soil on S. alterniflora growth, seedlings were transplanted in pots with only potting mixture or potting mixture mixed with salt marsh soil. These seedlings were then either grown in freshwater or saltwater (at 13 ppt) to determine the effect of salinity on plant growth and the microbial community. Results showed increased growth in freshwater and in potting soil mixed with salt marsh soil. However, when interactions between treatments were further explored, it was found that plant growth was greatest in potting mixture mixed with salt marsh soil, regardless of the salinity treatment. These results indicate that inoculation with salt marsh soil increases plant growth in nursery production of S. alterniflora.
Nursery Production of Spartina alterniflora for Coastal Marsh Restoration Using an Aboveground Wetland Designed to Remediate Aquaculture Effluent
M.S. Thesis, Alex Gregory
Traditional nursery production methods for Spartina alterniflora include sub-irrigation with freshwater and the use of commercial fertilizers, which are not similar to the conditions in natural marshes. The aim of this study was to evaluate the production of native S. alterniflora for salt marsh restoration projects in Coastal Georgia using a constructed wetland designed for remediation of marine aquaculture effluent. It was expected that the constructed aboveground wetland would provide the growing conditions required for nursery production of S. alterniflora, such as sub-irrigation to ensure continual submergence of belowground, while mimicking several salt marsh growing conditions, such as saturated and potentially anoxic soil and an organic fertilizer source consisting of fish waste and organic debris. Results showed no difference in measured growth variables between traditionally grown plants and plants grown in the aboveground wetland, suggesting that S. alterniflora can be grown and maintained in an aboveground wetland designed to remediate aquaculture effluent.