Abstracts of Proposals Funded by the 2005 SWS Student Grant Program
The Importance of Gradient Analysis, Landscape Perspectives, Metapopulation Dynamics, and Patch Dynamics in the Evaluation and Restoration of Imperiled Coastal Plain Pond Communities on Martha’s Vineyard
Investigator: Claire Berger
Duke University
Accelerated development in southeastern Massachusetts threatens the status of the already imperiled and highly diverse coastal plain pond ecosystem, making this system a high priority for conservation and restoration. This project examines the environmental and landscape factors that encourage increased rare species presence/abundance and increased overall diversity within the coastal plain pond ecosystem. I will use this information to design and initiate a restoration plan for degraded ponds on Martha’s Vineyard, an island off of the Massachusetts coast.
Just as important, coastal plain ponds provide an ideal system for studies of the effects of landscape fragmentation, habitat degradation, and connectivity on species population and community dynamics. This research will empirically evaluate four competing ecological approaches used to study plant population dynamics, to create an improved framework for the examination of composition and dynamics of plant populations and communities.
Morphological plasticity of cyanobacteria under different light underwater climates in a pristine natural wetland (Natural Otamendi reserve, Argentina)
Investigator: Paula de Tezanos Pinto
University of Buenos Aires
The Otamendi Natural Ecological Reserve (Buenos Aires, Argentina) is a pristine wetland that presents large areas with extreme low light underwater climate due to a persisting floating macrophyte cover. The present research proposal constitutes a deepening of my previous PhD studies, where I conducted a short-term mesocosm-scale experiment simulating stages of profuse vegetation cover and stages free of floating macrophytes coverage. In this way, I assessed the direct and indirect effects of light limitation produced by floating macrophytes on the phytoplankton functional groups.
This study led to a detailed knowledge of the ecology of a shade-adapted cyanobacteria flora belonging to the S1, S2 , SN, Z and Lo, functional groups sensu Reynolds. The morphological responses of these algae to different light regimes need to be further studied. I observed that under different light conditions, organisms belonging to the same species showed morphological plasticity in terms of trichome length, presence/absence of vacuoles, number of cells per colonies, presence/absence of akinets and colour, among other characteristics.
The present study will be performed with the aim of assessing the influence of light on the dimensions and shapes of these phytoplankton organisms. In order to assess morphological variability, I will analyse two sets of samples, both collected from scenarios with different light climates: 1) samples collected during the mesocosm field experiment and 2) samples collected from different sites that encompass the environmental heterogeneity of the wetland. The geometrical dimensions, shapes, axial linear dimension, length and width of the trichome, length and width of each cell within the thricome, presence of vacuoles and granules and their position within the trichome, presence of akinets and heterocysts and colour will be recorded. The surface/volume and sinking ratio will be also calculated. I will try to identify variables which link morphological variability with the ability of these shade adapted cyanobacteria to successfully exploit the resources in such light constricted environments.
Temperature effects on root exudation from wetland flora: how will climate change influence the supply of labile substrates to methanogens in peatlands?
Investigator: Angela Gallego-Sala
University of Bristol
Wetlands are environments where high water levels limit the entry of oxygen into soils, resulting in a condition known as ‘anoxia’. The only organisms that can live under such conditions are anaerobic micro-organisms, which grow by consuming soil organic matter as a source of energy and use compounds other than oxygen in their metabolism.
Some of the micro-organisms that live in wetlands are unique because a waste product of their metabolism is methane. Methane is a very effective Greenhouse Gas and because of its potential to contribute to global warming, there is great interest in understanding how methane is produced and released from wetlands.
Natural wetlands cover millions of square kilometres of the Earth’s surface and release more methane into the atmosphere each year than any other source. One of the current gaps in our knowledge about methane formation in wetlands is the role of plants in supplying nutrients to microbes. We know that micro-organisms consume plant matter once plants die. However, while plants are alive, they also release organic substances from their roots known as ‘exudates’. Little is known about the types and amounts of root exudates that are released by aquatic plants growing in oxygen-poor soils. Moreover, few studies have looked at how changes in the environment might influence production of exudates by aquatic plants.
In an attempt to characterise root exudation and also to assess the effect of soil temperature and light conditions on wetland plant root exudates, wetland plants will be placed in a special type of incubator that can simulate daily cyclical changes in soil temperature. Aquatic plants will be grown in sterile conditions in order to determine the effects of differences in temperature and light on root exudation without interference from micro-organisms.
The results of this work will be a first step to characterise root exudates from wetland plants. It will eventually be beneficial to scientists creating computer models of the Earth’s climate system. A better understanding of how aquatic plants produce substances which microbes consume to generate methane will aid in improving the representation of wetlands in such models.
Environmental conditions inducing accumulation of polyphosphate in microbial communities of natural and restored freshwater wetlands
Investigator: Wyatt Hartman
Duke University
Recognition of phosphorus limitation of aquatic systems has led to interest in attenuating phosphorus transport by sequestering phosphorus in wetlands. While geochemical mechanisms of phosphorus sorption in wetlands are well characterized, far less is understood about the influence of microbial communities on P cycling, despite the proximate control microbes exert over ecosystem phosphorus uptake. Polyphosphate (PolyP) accumulation may potentially play a large role in P uptake and storage by microbes in wetlands, although little is known about microbial PolyP metabolism under natural environmental conditions.
The pervasiveness of polyphosphate accumulation in natural sedimentary environments is evident from numerous 31P-NMR studies finding PolyP in wetland, riverine, lacustrine, and marine sediments. The potential to manipulate environmental conditions to enhance P sequestration by inducing polyphosphate accumulation is suggested by the success of enhanced biological phosphorus removal (EBPR) wastewater treatment systems. While EBPR systems appear to depend on coupled anaerobic/aerobic cycles to induce Poly-P accumulation, studies of bacterial physiology indicate Poly-P accumulation may be induced in response to a number of environmental stresses. It is likely that the factors controlling PolyP accumulation in wetland ecosystems will differ from those in wastewater treatment systems.
In my dissertation research, I will seek to demonstrate the presence of Poly-P accumulating organisms in natural and restored wetlands and test the effects of oxygen availability, pH, iron, and organic matter on bacterial Poly-P accumulation. Furthermore, I will determine the microbial communities responsible for Poly-P accumulation in reference and restored wetlands, and quantify the contribution of polyphosphate accumulation to wetland phosphorus cycling under different environmental conditions that may be actively managed. Understanding key controls over PolyP accumulation in wetland microbial communities may improve management and restoration of wetlands to enhance phosphorus sequestration.
Evolutionary Impacts of Human-induced Habitat Modification on an Endemic Livebearing Fish
Investigator: R. Brian Langerhans
Washington University
Habitat degradation and destruction is widely viewed as one of the greatest threats to biological diversity. Although ecological consequences of human-induced habitat alteration are receiving considerable attention, evolutionary consequences of human activities have only recently begun attracting significant interest. Fragmentation of estuaries represents a major source of environmental disturbance that threatens important ecosystem services provided by estuary systems.
Caribbean island estuaries are often fragmented by road construction, affecting numerous features, such as nutrient cycling and assemblages of resident and transient organisms. One major consequence of fragmented estuaries is a marked reduction in the density of piscivorous fishes, with severely fragmented estuaries often completely lacking piscivores. The rapid and dramatic changes in biotic and abiotic characteristics following estuary fragmentation likely generates substantially different selection pressures than were naturally present before human-induced habitat modification.
I propose to investigate the evolutionary effects of estuary fragmentation on a small, livebearing fish endemic to The Bahamas, Gambusia hubbsi. In addition, I plan to investigate the ability of restoration efforts to restore natural ecological and evolutionary processes by monitoring G. hubbsi populations subsequent to the restoration of several fragmented estuaries (including collections before and after restoration). The study will compare body morphology among populations inhabiting estuaries of varying degrees of fragmentation (e.g. ranging from undisturbed estuaries to those that have been completely separated from the marine environment for several decades).
Following estuary fragmentation and reduction in predation intensity, specific changes in body morphology of G. hubbsi are predicted based on biomechanical principles and previous empirical work with this species and other closely related species. I have conducted initial collections on Andros Island, The Bahamas (eight estuarine populations), and preliminary results match predictions, suggesting rapid evolutionary divergence in response to human-induced habitat changes. The proposed work will expand upon this preliminary evidence by extending collections to approximately 30 additional estuaries spanning several islands having a longer history and more severe cases of estuary fragmentation. Results of the study should provide a better understanding of the evolutionary consequences that human activities might induce, as well as the effectiveness of ecological restoration methods in re-establishing natural evolutionary processes.
Post-tsunami assessment of mangrove ecosystems in Phra Thong Island, Thailand, using landsat tm imagery, field surveys, and GIS
Investigator: Jennifer Morse
Duke University
Intact mangrove forests provide important ecosystem services, such as reducing coastal erosion and protecting low-lying areas from flooding and storm surges. On 26 December 2004, a earthquake in the Indian Ocean triggered massive waves that caused death and destruction in many coastal areas in the region. A disturbance of this magnitude presents an important opportunity to evaluate the role of mangroves in protecting shorelines, to determine whether mangroves were impacted differently than other habitats, and to quantify the loss of mangroves as a result of the tsunami. I propose to use remote sensing techniques to detect land cover change for this purpose.
Koh Phra Thong, a 100 km2 island off Thailand’s western coast in the Andaman Sea, was severely affected by the tsunami, losing many inhabitants, two fishing villages, two resorts, and the research base for Naucrates, an Italian scientific organization. In 2002, I worked with researchers from Naucrates and Ranong Coastal Resources Research Station (RCRRS) to establish a longterm monitoring program of mangrove areas and an ecosystem mapping program on Koh Phra Thong. I will resume that partnership to build upon our existing data on the areal extent of mangroves and other ecosystems to evaluate the impacts of the tsunami on the island. We will use our field data and a Landsat ETM+ image from 2002 to complete the land cover classification we began then. We will acquire a new satellite image (post-tsunami) and apply the land cover classification to the new image.
This work represents an exceptional chance to apply pre-disturbance data to measure changes in land cover after the tsunami and determine the extent to which mangrove areas protected the coast from the surges. I will benefit professionally by gaining skills in integrating remote sensing data with ecological data and renewing interdisciplinary collaborations with scientists from Thailand and Italy. This research is compelling also because it may help identify areas for mangrove restoration. It is personally meaningful as well, because it will be a step toward reestablishing the mangrove research and conservation program on Koh Phra Thong that was destroyed by the tsunami.
Understanding factors contributing to small population sizes: A landscape genetics study of sympatric amphibians in Yellowstone National Park
Investigator: Melanie A. Murphy
Washington State University
Effective conservation of small populations requires the identification of processes contributing to species distribution and population persistence. Thus, while ecology often focuses on the question, "Why is a species here?" in conservation the question is often, "Why is this species not here?" Habitat change and wetland health are likely critical in limiting and the persistence of amphibian species. Therefore, understanding amphibian breeding site occupancy and dispersal between sites can demonstrate the importance of functioning wetland systems to amphibian metapopulation dynamics.
Demographic studies can be used to address population movement but often require long-term studies or large sample sizes for significant results and are influenced by the frequent large fluctuations in amphibian population size. However, genetic techniques can be used to estimate migration between breeding populations and identify dispersal limitations.
The objective of this study is to identify ecological and anthropogenic landscape features influencing gene flow in two sympatric amphibian species within Yellowstone National Park, boreal toads (Bufo boreas boreas) and boreal chorus frogs (Pseudacris maculata). The National Wetland Inventory was stratified by elevation and rainfall and selected sites were visited in 2004 with additional sampling planned for 2005. Individuals will be sampled by mouth swabbing without prior identification of populations and will be genotyped with microsatellite loci.
Genetic analysis software (structure) will be used to group individuals into populations based on genetic similarity. Membership probabilities from structure will be used to create a genetic surface in a Geographic Information System (GIS). High points in the genetic surface will indicate areas of high gene flow (lots of movement) and low points will indicate areas of restricted gene flow (little movement). Spatial analysis will be used to correlate ecological and anthropogenic features with the genetic surface. Once landscape features limiting amphibian populations such as wetland alteration identified, they can be incorporated into wetland conservation and management. In addition, the methods developed will provide the foundation for using genetic and landscape data to build empirical relationships between ecological factors (e.g. hydrological gradients), anthropogenic factors (e.g. wetland modification), and gene flow in any species.
Application of PCR – Based Denaturing Gradient Gel Electrophoresis to Profile Archaeal, Eubacterial, and Fungal Populations in Two Forested Floodplains of the Southeastern United States
Investigator: John A. Navaratnam
West Virginia University
Floodplain forests (FFs) are wetlands that are biogeochemically linked to both surrounding uplands and adjacent aquatic ecosystems. As natural landscapes are transformed to culturally dominated ones by agriculture, urbanization, or other anthropogenic activities, inputs of phosphate (a common agent of cultural eutrophication) to aquatic ecosystems generally increase.
Floodplain forests play an important role in the retention and transformation of phosphorus (P) received through both upland hydrologic discharge and overbank flooding, thereby improving water quality in downstream aquatic ecosystems. Through a variety of processes (sediment deposition, soil adsorption, plant uptake, and microbial immobilization), FFs remove phosphates from the water column, storing them within the wetland ecosystem or converting them to a less harmful organic form. Recent evidence suggests that soil microorganisms play a more important role in these P retention and transformation processes than previously believed, and that microbial processing of P inputs can vary spatially within a FF ecosystem, as well as temporally, with seasonal changes in microbial community composition.
While it has been known for some time that microorganisms can represent important short-term sinks for phosphate in freshwater wetland ecosystems, little is known about how microbial diversity affects P retention and transformation. To assess the dominant microbial species, I will use the genetic finger printing technique of denaturing gradient gel electorphoresis (DGGE), to complete and complement a previously established clone library of 520 archaeal, eubacterial, and fungal sequences.
In this project, the overall objective is to investigate the microbial community structure in soils collected from an alluvial (Wateree River, SC) and a blackwater (Black River, NC) FF site, as well as their spatial variation in higher elevation ridge and lower elevation swale microsites in these floodplain types. Knowledge of the microbial community structure in these FFs is the first step toward linking microbial diversity to P retention and transformation functions.
Hydraulic Resistance due to Emergent Wetland Vegetation
Investigator: Candice Piercy
Virginia Tech University
Wetland creation and restoration is intended to offset the widespread loss of wetlands since European colonization. A critical factor in restoring or recreating wetland function is establishing the correct water depth in the wetland. Many created wetlands fail because they are actually too wet to function like the wetlands they were intended to replace. While there are several causes of this problem, one of the issues is inaccurate prediction of the rate of water outflow from the wetland. Often this outflow rate is determined by the hydraulic resistance due to wetland vegetation; thickly-vegetated wetlands will slow down water flow and increase the water depth. Since little knowledge on how wetland vegetation affects water flow exists, flow through sparsely-vegetated open channels has been used a guide, with little success.
An equation has been developed that specifically describes how wetland vegetation affects water flow; it allows for modification for the specific flow and vegetative conditions in the wetland. Little work has been done to quantify how to specifically modify the equation based on measurable parameters like flow depth and vegetation density.
The goal of this research is to evaluate the effectiveness of this equation in the design of emergent wetlands and to relate the model parameters to measures of flow and vegetation type and density. To achieve this goal, a large outdoor flume, 4 ft wide and 40 ft long, will be built and planted with woolgrass (Scirpus cyperinus). Water depths, flow rates and vegetation density will be measured in a series of experiments throughout the growing season so the effect of vegetation height and density on wetland flow can be accurately assessed. Using the data collected from the flume experiments, the parameters of the flow equation will be determined and compared to the equation currently used to estimate flow in vegetated open channels. A method will then be developed to estimate these model parameters based on easily measured vegetation characteristics. This project will result in an improved tool for wetland designers to better estimate how the water depth in wetlands changes with vegetation and water flow. The tool will ultimately result in better-designed wetlands that better achieve their intended function.
Double Jeopardy for Wetland Reptiles: Assessing Threats Beyond the Wetland Border in an Australian Freshwater Turtle, Chelodina longicollis
Investigator: John H. Roe
University of Canberra
Wetland destruction and the decline of associated fauna have instigated conservationists to take action and protect wetland habitats from encroaching anthropogenic development. However, despite modest gains in wetland conservation, protection is rarely extended into terrestrial habitats despite the demonstrated importance of such habitats for many wetland animals and the potential for large-scale and persistent mortality to occur when animals interact with human infrastructure in terrestrial habitats. In reality, many wetland animals are facing double jeopardy as they are forced to cope with habitat degradation both within and outside the wetland, yet conservation plans rarely address threats occurring beyond the wetland border.
The broad aim of this study is to investigate the potential for anthropogenic habitat modification in terrestrial landscapes to affect populations of an Australian freshwater turtle, Chelodina longicollis. For the initial phase of the project, I propose to conduct a radio-telemetry and capture-mark-recapture study of C. longicollis to determine the extent to which this species relies on terrestrial habitats for inter-wetland movements, aestivation, hibernation, nesting, and other behaviors. Based on the radio-telemetry and mark-recapture findings, I will then assess the potential consequences of terrestrial habitat alteration (e.g., road networks) for C. longicollis populations on a regional scale by simulating C. longicollis terrestrial movements on maps of wetlands and road networks to predict probability of road mortality in southeast Australia.
In the final stage of the project, I will test the predictions of the road mortality models by conducting a natural experiment investigating C. longicollis population structure along a gradient of wetlands differing in the degree of habitat modification (e.g., road density) in surrounding terrestrial landscapes. Such information would contribute to our knowledge of the complex interaction that aquatic reptiles may have with both aquatic and terrestrial habitats. In doing so, this study will also highlight potential threats to freshwater turtles and other wetland animals, and identify management actions and interventions that will enhance conservation efforts for wetland fauna both on and off reserve.
The relationship between hydrogeochemical alterations and the spread of invasive species in calcareous fen ecosystems
Investigator: Maura E. Sullivan
Lehigh University
Invasive species pose a major threat to the ecological integrity of calcareous fens, a unique type of peatland that supports numerous rare animal and plant species. The objective of this study is to identify the relationship between variations in hydrogeochemical parameters and the distribution of Lythrum salicaria (purple loosestrife) and Phragmites australis (common reed) in these ecosystems. Our approach will use two representative calcareous fen complexes as model systems to examine the processes enabling invasive species to be successful in highly alkaline, low nutrient peatlands. Our methods will correlate the chemical analysis of groundwater, the soil rhizosphere, and plant tissue N:P ratios across a gradient of invasive species densities. The results of this study will identify key components regulating the spread of exotics in calcareous fens and provide management recommendations for the conservation of this habitat.
The Role of Plant Diversity In Regulating Nitrogen Removal In A Restored Riparian Wetland
Investigator: Ariana Sutton-Grier
Duke University
There have been many studies demonstrating that biodiversity affects the stability and functioning of ecosystems; yet the role of plant diversity in wetland ecosystems is largely unknown. As biodiversity declines, conservationists and scientists want to determine what happens to ecosystem function as species are lost. Ecosystem restoration projects offer an exciting opportunity to explore the alternative, innovative question: What happens to ecosystem function as additional species are added to a newly restored system?
There has recently been a great deal of interest in the restoration of wetland ecosystems. Wetlands are critical ecosystems that provide many ecosystem services important to humans including flood control and water purification. Many wetlands have been destroyed or degraded due to human intervention and, as a result, restoration of wetland ecosystem functions is increasingly important. This research is designed to investigate how increasing plant diversity affects the restoration of riparian wetland ecosystem functions that remove nitrogen from surface and ground water: nitrogen retention in plant biomass and denitrification. Field plots will be planted with 1, 4 or 8 species selected from 10 suggested species for Piedmont riparian wetland restorations. The results of this study will be critical for guiding future riparian restoration efforts to improve water quality and prevent eutrophication. The results will also provide valuable information about how ecosystems function that will help ecologists better understand the importance of biodiversity in ecosystems.
