Coastal Plant Ecology
Research in the Joesting lab focuses on plants in coastal habitats, including unique adaptations to the coastal environment, the important role they play in maintaining coastal ecosystem processes, and their potential use in coastal management techniques to created a balance between anthropogenics and ecosystem processes on barrier islands of the United States.
Research in the Joesting lab focuses on plants in coastal habitats, including unique adaptations to the coastal environment, the important role they play in maintaining coastal ecosystem processes, and their potential use in coastal management techniques to created a balance between anthropogenics and ecosystem processes on barrier islands of the United States.
Current Projects
Testing the "Local is Best" Hypothesis: Comparing Growth and Survival for Spartina alterniflora from Varying Sources
Spartina alterniflora populations can be found in salt marshes from Newfoundland to Texas, spanning a variety of climatic, hydrological, and environmental factors. Studies have indicated at least four haplotypes throughout its distribution, and research also suggests variation within these haplotype groups. Plants can become locally adapted to a particular set of conditions, and Georgia marshes are unique in terms of their tidal regimes, riverine input, and low wave/storm energy. Thus, it is hypothesized that local Georgia S. alternilfora should perform best as transplants in restoration projects in coastal Georgia. To test this hypothesis, plants from multiple sources (GA seedlings and rhizomes, SC seedlings and rhizomes, and MD seedlings) were grown together in an aboveground wetland. The wetland was attached to an aquaculture tank stocked with shrimp and set up to drain and fill on a 6 hour cycle to mimic tides. This experiment is currently underway.
Spatial and Temporal Patterns in Fecundity for Spartina alterniflora in Georgia Salt Marshes
Spartina alterniflora is the dominant coastal salt marsh plant species along the East and Gulf Coast of the United States and plays a critical role in marsh growth and maintenance. Information on S. alterniflora phenology and fecundity for an area is vital in coastal salt marsh management strategies, but there is little data on seed viability and germination success for S. alterniflora within Georgia salt marshes. The goal of this study is to assess seed set, seed viability, and germination success for S. alterniflora collected from multiple salt marshes and over multiple years in Chatham County, Georgia. The Joesting Lab has collected seeds and assessed fecundity over the past 4 years (2019-2022) and continues to do so on an annual basis. Results from this study will provide critical information to coastal managers the reproductive potential of populations of S. alterniflora in Georgia salt marshes, as well as inform plant nursery practitioners on the best marshes and time during the reproductive season to collect seeds for seedling production. For more information on these results, please visit the Nursery Production of GA Spartina alterniflora page.
Determining Best Practices in the Nursery Production of Spartina alterniflora for Restoration
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. For more information on these results, please visit the Nursery Production of GA Spartina alterniflora page.
Testing the "Local is Best" Hypothesis: Comparing Growth and Survival for Spartina alterniflora from Varying Sources
Spartina alterniflora populations can be found in salt marshes from Newfoundland to Texas, spanning a variety of climatic, hydrological, and environmental factors. Studies have indicated at least four haplotypes throughout its distribution, and research also suggests variation within these haplotype groups. Plants can become locally adapted to a particular set of conditions, and Georgia marshes are unique in terms of their tidal regimes, riverine input, and low wave/storm energy. Thus, it is hypothesized that local Georgia S. alternilfora should perform best as transplants in restoration projects in coastal Georgia. To test this hypothesis, plants from multiple sources (GA seedlings and rhizomes, SC seedlings and rhizomes, and MD seedlings) were grown together in an aboveground wetland. The wetland was attached to an aquaculture tank stocked with shrimp and set up to drain and fill on a 6 hour cycle to mimic tides. This experiment is currently underway.
Spatial and Temporal Patterns in Fecundity for Spartina alterniflora in Georgia Salt Marshes
Spartina alterniflora is the dominant coastal salt marsh plant species along the East and Gulf Coast of the United States and plays a critical role in marsh growth and maintenance. Information on S. alterniflora phenology and fecundity for an area is vital in coastal salt marsh management strategies, but there is little data on seed viability and germination success for S. alterniflora within Georgia salt marshes. The goal of this study is to assess seed set, seed viability, and germination success for S. alterniflora collected from multiple salt marshes and over multiple years in Chatham County, Georgia. The Joesting Lab has collected seeds and assessed fecundity over the past 4 years (2019-2022) and continues to do so on an annual basis. Results from this study will provide critical information to coastal managers the reproductive potential of populations of S. alterniflora in Georgia salt marshes, as well as inform plant nursery practitioners on the best marshes and time during the reproductive season to collect seeds for seedling production. For more information on these results, please visit the Nursery Production of GA Spartina alterniflora page.
Determining Best Practices in the Nursery Production of Spartina alterniflora for Restoration
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. For more information on these results, please visit the Nursery Production of GA Spartina alterniflora page.
Past Projects
The Role of Phenotypic Plasticity in the Ability of Hydrocotyle bonariensis to Occupy Two Habitats in Coastal Georgia
Previous research in the lab found that Hydrocotyle bonariensis showed plastic response to soil types under greenhouse conditions, and this research sought to further explore the role of phenotypic plasticity in the ability of H. bonariensis to occupy different habitats in coastal Georgia. Specifically, leaf morphology was compared between populations in the coastal sand dune and inland coastal plain habitats. Environmental variables (i.e., incident sunlight, soil characteristics, and soil and air temperatures) was assessed for each habitat, and leaf characteristics were measured for individuals collected from each population. The results of this research were included in an Honors Thesis and presented at both the Southern Regional Honors Council Annual Conference and the Georgia Southern University Honors Symposium in 2022. Additionally, this research is currently in press at Southeastern Naturalist.
Effect of Barnacle Colonization on the Growth and Productivity of Spartina alterniflora
Recently, barnacles (Chthalamus fragilis) have been observed colonizing the stems and leaves of Spartina alterniflora in coastal Georgia salt marshes. The purpose of this research is to (1) investigate spatial and annual patterns in barnacle colonization and (2) investigate potential impacts of barnacle colonization on S. alterniflora growth and productivity. To this end, monthly field surveys have been conducted during the 2016, 2017, 2018, and 2019 growing season in three coastal salt marshes of varying marine influence in Chatham County, Georgia. Additionally, a field experiment was conducted in 2016 to investigate the relationship between barnacle colonization and plant productivity. The results of the 2016 field survey and experiment were published in Estuarine and Coastal Shelf Science in 2020. Results from this project have also been presented at the 78th Annual Association of Southeastern Biologists Meeting, the 46th Annual Benthic Ecology Meeting, the 2017 Armstrong Student Scholars Symposium, the 79th Annual Association of Southeaster Biologists Meeting, the 2018 Armstrong Student Scholars Symposium, and the 2020 Georgia Southern University Virtual Research Symposium. This research is done in collaboration with Dr. Michele Guidone in the Biology Department at Georgia Southern University .
Potential Use of Dried Marine Algae Removed from Algal Turf Scrubbers as a Nutrient Source for Nursery Production of Spartina alterniflora
Nursery production of Spartina alterniflora requires frequent fertilization, often using commercial fertilizers, and can represent a significant cost to nurseries. The purpose of this study was to determine if marine algae removed from an algal turf scrubber, which is designed to remove nutrients from a water body through incorporation into algal biomass, can be used as a nutrient source in the nursery production of S. alterniflora. S. alterniflora plugs were planted in three different treatments and cut back for winter senescence: (1) Control (no nutrient source), (2) Osmocote (commercial fertilizer), and (3) dried algae removed from ATS. Regrowth (e.g., weekly plant height and number of ramets) was monitored for twelve weeks, and plant growth and biomass was compared among treatments to determine the fertilizer potential of algae removed from an ATS.
Phenotypic Plasticity in Hydrocotyle bonariensis in Response to Soil Type and Salt Spray
Previous research examining ramet morphology of Hydrocotyle bonariensis individuals from the coastal sand dune habitat in response to two soil types showed differences in stomata density and length between individuals grown in beach sand and inland soil, suggesting a phenotypic plastic response in this species to soil type (see "Examination of Phenotypic Plasticity in Hydrocotyle bonariensis in Response to Two Soil Types" below under Past Projects). The aim of this research project was to further explore potential phenotypic plasticity in this species in response to soil type by comparing ramet morphology between individuals from the coastal sand dune habitat and an inland habitat (i.e., Georgia Southern University Armstrong Campus) grown in beach sand and inland soil. Furthermore, the response of individuals from both habitats to salt spray was investigated to determine if sand dune individuals have unique adaptations to salt spray or if this species responds plastically to this environmental stressor. The results of this project was presented at the 80th Annual Association of Southeastern Biologists Meeting (received Outstanding Student Poster Presentation Award from the Southeastern Section of the Botanical Society of America) and the 2019 Georgia Southern University Research Symposium. This research is currently in press at Southeastern Naturalist.
Examination of Phenotypic Plasticity in Hydrocotyle bonariensis in Response to Two Soil Types
Phenotypic variation is physiological and/or morphological variations within a species in response to variations in the environment. Hydrocotyle bonariensis is commonly found in sandy habitats along the southeastern coast of the United States, including coastal sand dunes, roadside ditches and disturbed areas, and residential and commercial lawns. Although the macroclimate is similar in these habitats, there are differences in microenvironmental variables (e.g., soil composition and water holding capacity, nutrient availability, and daily incident sunlight) that can influence plant morphology. The purpose of this project was to compare plant morphology and anatomy between H. bonariensis from the coastal sand dune habitat and plants from a more inland habitat (Armstrong Campus). Plant fragments collected from the sand dune habitat of Tybee Island, GA, were propagated in both native soil and soil from the Armstrong Campus and maintained under greenhouse conditions. Leaf and petiole morphology and stomata density and length were measured for single-leaf ramets from the sand dune and inland soil over a seven week period. These results were presented at the 2016 Student Scholar Symposium at Armstrong State University as a poster and will be published in BIOS in the September 2018 issue.
Exploring Spatial and Temporal Variations in the Morphology of the Coastal Sand Dune Shrub Croton punctatus
Croton punctatus is a common inhabitant of the coastal sand dunes of Georgia. Although this shrub is an important component of the coastal sand dune plant community in the Southeastern U.S., little research has focused on the morphological and physiological responses of this species to the abiotic factors of the sand dune environment. The purpose of this project was to determine if there are variations in plant morphology and/or physiology diurnally, seasonally, and/or between the windward and leeward side of the primary dunes. Data on plant height, leaf chlorophyll content, leaf salt deposition, leaf size, and trichome density was collected seasonally (June - August) for individuals located along two 25-m transects extending from the beginning of the primary dune to the dune interior on Sapelo Island, GA. Additionally, measurements of photosystem efficiency, leaf temperature, and leaf-level sunlight incidence were measured every two hours for these individuals. The results from this research as a poster at the 77th Annual Meeting of the Association of Biologists and Botany 2016.
Effect of Leaf Inclination on Diurnal Leaf Temperature and Photosynthesis in Hydrocotyle bonariensis
Leaf inclination from horizontal is common in plants occupying high light habitats, and studies have suggested that leaf inclination in these habitats functions to reduce midday sunlight exposure, thus reducing leaf temperature and enhancing leaf photosynthesis. The clonal sand dune herb Hydrocotyle bonariensis (large-leaf pennywort) has been observed to increase leaf inclination over the growing season from ~55 degrees from horizontal in May to ~90 degrees in August (Joesting et al. 2011). Furthermore, this increased leaf inclination was shown to reduce midday light exposure while increasing morning and afternoon incident sunlight. The purpose of this research was to investigate the function of leaf inclination in H. bonariensis by comparing leaf temperature, leaf chlorophyll content, and leaf photosystem efficiency between control inclined leaves and experimental forced horizontal leaves on Jekyll Island, GA, during the summer of 2014. The results of this research were presented as a poster at the 76th Annual Meeting of the Association of Southeastern Biologists and as an oral presentation at the 100th Annual Ecological Society of America Meeting. The results were also published in Flora in 2016.
The Role of Phenotypic Plasticity in the Ability of Hydrocotyle bonariensis to Occupy Two Habitats in Coastal Georgia
Previous research in the lab found that Hydrocotyle bonariensis showed plastic response to soil types under greenhouse conditions, and this research sought to further explore the role of phenotypic plasticity in the ability of H. bonariensis to occupy different habitats in coastal Georgia. Specifically, leaf morphology was compared between populations in the coastal sand dune and inland coastal plain habitats. Environmental variables (i.e., incident sunlight, soil characteristics, and soil and air temperatures) was assessed for each habitat, and leaf characteristics were measured for individuals collected from each population. The results of this research were included in an Honors Thesis and presented at both the Southern Regional Honors Council Annual Conference and the Georgia Southern University Honors Symposium in 2022. Additionally, this research is currently in press at Southeastern Naturalist.
Effect of Barnacle Colonization on the Growth and Productivity of Spartina alterniflora
Recently, barnacles (Chthalamus fragilis) have been observed colonizing the stems and leaves of Spartina alterniflora in coastal Georgia salt marshes. The purpose of this research is to (1) investigate spatial and annual patterns in barnacle colonization and (2) investigate potential impacts of barnacle colonization on S. alterniflora growth and productivity. To this end, monthly field surveys have been conducted during the 2016, 2017, 2018, and 2019 growing season in three coastal salt marshes of varying marine influence in Chatham County, Georgia. Additionally, a field experiment was conducted in 2016 to investigate the relationship between barnacle colonization and plant productivity. The results of the 2016 field survey and experiment were published in Estuarine and Coastal Shelf Science in 2020. Results from this project have also been presented at the 78th Annual Association of Southeastern Biologists Meeting, the 46th Annual Benthic Ecology Meeting, the 2017 Armstrong Student Scholars Symposium, the 79th Annual Association of Southeaster Biologists Meeting, the 2018 Armstrong Student Scholars Symposium, and the 2020 Georgia Southern University Virtual Research Symposium. This research is done in collaboration with Dr. Michele Guidone in the Biology Department at Georgia Southern University .
Potential Use of Dried Marine Algae Removed from Algal Turf Scrubbers as a Nutrient Source for Nursery Production of Spartina alterniflora
Nursery production of Spartina alterniflora requires frequent fertilization, often using commercial fertilizers, and can represent a significant cost to nurseries. The purpose of this study was to determine if marine algae removed from an algal turf scrubber, which is designed to remove nutrients from a water body through incorporation into algal biomass, can be used as a nutrient source in the nursery production of S. alterniflora. S. alterniflora plugs were planted in three different treatments and cut back for winter senescence: (1) Control (no nutrient source), (2) Osmocote (commercial fertilizer), and (3) dried algae removed from ATS. Regrowth (e.g., weekly plant height and number of ramets) was monitored for twelve weeks, and plant growth and biomass was compared among treatments to determine the fertilizer potential of algae removed from an ATS.
Phenotypic Plasticity in Hydrocotyle bonariensis in Response to Soil Type and Salt Spray
Previous research examining ramet morphology of Hydrocotyle bonariensis individuals from the coastal sand dune habitat in response to two soil types showed differences in stomata density and length between individuals grown in beach sand and inland soil, suggesting a phenotypic plastic response in this species to soil type (see "Examination of Phenotypic Plasticity in Hydrocotyle bonariensis in Response to Two Soil Types" below under Past Projects). The aim of this research project was to further explore potential phenotypic plasticity in this species in response to soil type by comparing ramet morphology between individuals from the coastal sand dune habitat and an inland habitat (i.e., Georgia Southern University Armstrong Campus) grown in beach sand and inland soil. Furthermore, the response of individuals from both habitats to salt spray was investigated to determine if sand dune individuals have unique adaptations to salt spray or if this species responds plastically to this environmental stressor. The results of this project was presented at the 80th Annual Association of Southeastern Biologists Meeting (received Outstanding Student Poster Presentation Award from the Southeastern Section of the Botanical Society of America) and the 2019 Georgia Southern University Research Symposium. This research is currently in press at Southeastern Naturalist.
Examination of Phenotypic Plasticity in Hydrocotyle bonariensis in Response to Two Soil Types
Phenotypic variation is physiological and/or morphological variations within a species in response to variations in the environment. Hydrocotyle bonariensis is commonly found in sandy habitats along the southeastern coast of the United States, including coastal sand dunes, roadside ditches and disturbed areas, and residential and commercial lawns. Although the macroclimate is similar in these habitats, there are differences in microenvironmental variables (e.g., soil composition and water holding capacity, nutrient availability, and daily incident sunlight) that can influence plant morphology. The purpose of this project was to compare plant morphology and anatomy between H. bonariensis from the coastal sand dune habitat and plants from a more inland habitat (Armstrong Campus). Plant fragments collected from the sand dune habitat of Tybee Island, GA, were propagated in both native soil and soil from the Armstrong Campus and maintained under greenhouse conditions. Leaf and petiole morphology and stomata density and length were measured for single-leaf ramets from the sand dune and inland soil over a seven week period. These results were presented at the 2016 Student Scholar Symposium at Armstrong State University as a poster and will be published in BIOS in the September 2018 issue.
Exploring Spatial and Temporal Variations in the Morphology of the Coastal Sand Dune Shrub Croton punctatus
Croton punctatus is a common inhabitant of the coastal sand dunes of Georgia. Although this shrub is an important component of the coastal sand dune plant community in the Southeastern U.S., little research has focused on the morphological and physiological responses of this species to the abiotic factors of the sand dune environment. The purpose of this project was to determine if there are variations in plant morphology and/or physiology diurnally, seasonally, and/or between the windward and leeward side of the primary dunes. Data on plant height, leaf chlorophyll content, leaf salt deposition, leaf size, and trichome density was collected seasonally (June - August) for individuals located along two 25-m transects extending from the beginning of the primary dune to the dune interior on Sapelo Island, GA. Additionally, measurements of photosystem efficiency, leaf temperature, and leaf-level sunlight incidence were measured every two hours for these individuals. The results from this research as a poster at the 77th Annual Meeting of the Association of Biologists and Botany 2016.
Effect of Leaf Inclination on Diurnal Leaf Temperature and Photosynthesis in Hydrocotyle bonariensis
Leaf inclination from horizontal is common in plants occupying high light habitats, and studies have suggested that leaf inclination in these habitats functions to reduce midday sunlight exposure, thus reducing leaf temperature and enhancing leaf photosynthesis. The clonal sand dune herb Hydrocotyle bonariensis (large-leaf pennywort) has been observed to increase leaf inclination over the growing season from ~55 degrees from horizontal in May to ~90 degrees in August (Joesting et al. 2011). Furthermore, this increased leaf inclination was shown to reduce midday light exposure while increasing morning and afternoon incident sunlight. The purpose of this research was to investigate the function of leaf inclination in H. bonariensis by comparing leaf temperature, leaf chlorophyll content, and leaf photosystem efficiency between control inclined leaves and experimental forced horizontal leaves on Jekyll Island, GA, during the summer of 2014. The results of this research were presented as a poster at the 76th Annual Meeting of the Association of Southeastern Biologists and as an oral presentation at the 100th Annual Ecological Society of America Meeting. The results were also published in Flora in 2016.