Increasing human pressure combined with sea level rise and increased storminess is threatening coastal ecosystems around the world. Among these ecosystems, saltmarshes are particularly endangered due to their position in temperate areas with low wave action where human density is often high (e.g. estuaries). Around the UK, centuries of land reclamation have led to a substantial decrease of the area of saltmarsh. Over the past decades, restoration schemes have been implemented in numerous coastal locations in an attempt to counteract this loss. Such schemes involve allowing sea water to inundate a previously embanked area and letting the vegetation develop naturally, thereby reverting to saltmarsh through natural colonisation. However, surveys of restored areas that have looked at the recovery of plant species diversity or functional characteristics often show that restored saltmarshes do not reach the state of a natural saltmarsh ecosystem. While there is much data at the species level, recovery of plant intra-specific diversity (genetic diversity) has not been assessed in restored saltmarsh although this component of biodiversity is receiving increasing attention for its effect on ecosystem function. This thesis represents the first attempt to (1) characterize the nation-wide genetic structure of two important north-west European saltmarsh plant species, the common saltmarsh grass (Puccinellia maritima) and the sea arrowgrass (Triglochin maritima) and (2) compare levels of genetic diversity and structure between restored and natural ecosystems. Microsatellite molecular markers were developed for both species. Using innovative methods to analyse the genetic data obtained for these two polyploid species, this thesis highlights that genetic diversity at the national scale is organised regionally for both species, although gene-flow is still restricted between populations within the same region. Gene-flow between populations is determined by different processes depending on the species. While coastal processes mainly influence gene dispersal in P. maritima, overland routes of dispersal are involved for T. maritima. These differences are believed to be due to differences in dispersal ecology between the two species. Although gene-flow exists between distant saltmarshes, the genetic analysis of P. maritima and T. maritima colonists arriving on restored sites highlighted their local origin and reaffirmed that it is preferable to restore saltmarsh where a nearby natural saltmarsh can act as a source of colonists. A multiple paired-site comparison identified similar genetic diversity between restored and natural saltmarshes indicating that restoration of local genetic diversity is rapid for both species. A single site comparison at Skinflats in the Forth estuary compared fine-scale spatial genetic structure between the restored and natural saltmarsh. Interestingly, no structure was detected for T. maritima either in restored or natural saltmarsh. In contrast, a strong genetic structure organised along the elevation gradient was observed in the natural saltmarsh for P. maritima but was absent in the restored saltmarsh. The origin of this structure is not clear but could be due to restricted gene-flow between individuals from different elevations due to strong post-zygotic selection, as suggested in previous work. In any case, this lack of structure in the restored saltmarsh indicates that genetic recovery is incomplete in this respect for P. maritima. This thesis introduces the growing field of restoration genetics to saltmarsh ecology and identifies the principal population genetic trends in two of the species dominating the vegetation of north-west European saltmarshes community. The information given here will be useful for restoration practitioners and provides a strong foundation for future work characterizing the importance of genetic diversity for saltmarsh function.

Seagrass is a key stone component for the Indian River Lagoon (IRL) ecosystem, and therefore it is an important topic for many studies in the lagoon. This study focuses on the effects of seagrass beds on the hydrodynamics in the IRL. A hydrodynamic model based on the Delft3D modeling system has been developed for the southern IRL including the St. Lucie estuary, Ft. Pierce and St. Lucie Inlets, and adjacent coastal waters. The model is driven by freshwater inputs from the watershed, tides, meteorological forcing, and oceanic boundary forcing. The model has been systematically calibrated through a series of numerical experiments for key parameters, particularly the bottom roughness, and configuration including heat flux formulation and bottom bathymetry. The model skills were evaluated with quantitative metrics (point-to-point correlation, root-mean-square difference, and mean bias) to gauge the agreements between model and data for key variables including temperature, salinity, and currents. A three-year (2013-2015) simulation has been performed, and the results have been validated with available data including observations at HBOI Land-Ocean Biogeochemistry Observatory (LOBO) stations and in situ measurements from various sources. The validated model is then used to investigate the effects of 1) model vertical resolution (total number of model vertical layers), 2) spatial variability of surface winds, and 3) seagrass beds on the simulated hydrodynamics. The study focuses on the vicinity of Ft. Pierce Inlet, where significant seagrass coverage can be found. A series of numerical experiments were performed with a combination of different configurations. Overall, the experiment with 2-dimensional (2-D) winds, ten vertical layers and incorporating seagrass provided the most satisfactory outcomes. Overall, both vertical resolution and spatial variability of surface winds affect significantly the model results. In particular, increasing vertical resolution improves model prediction of temperature, salinity and currents. Similarly, the model with 2-D winds yields more realistic results than the model forced by 0-D winds. The seagrass beds have significant effects on the model results, particularly the tidal and sub-tidal currents. In general, model results show that both tidal and sub-tidal currents are much weaker due to increase bottom friction from seagrass. For tidal currents, the strongest impacts lie in the main channel (inter-coastal waterway) and western part of the lagoon, where strong tidal currents can be found. Inclusion of seagrass in the model also improves the simulation of sub-tidal currents. Seagrass beds also affect model temperature and salinity including strengthening vertical stratification. In general, seagrass effects vary over time, particularly tidal cycle with stronger effects seen in flood and ebb tides, and seasonal cycle with stronger effects in the summer than in winter. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Includes vita. / Title from PDF of title page. / Document formatted into pages; contains 185 pages. / Thesis (Ph.D.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Seagrass communities are composed of numerous organisms that depend on water-column nutrients for metabolic processes. The rate at which these organisms remove a nutrient from the water column can be controlled by physical factors such as hydrodynamic regime or by biological factors such as speed of enzyme reactions. The impact of hydrodynamic regime on rates of nutrient uptake for seagrass (Thalassia testudinum) communities and for organisms that comprise the community (seagrass, epiphytes, phytoplankton, and microphytobenthos) was quantified in a series of field flume experiments employing the use of 15N-labeled ammonium and nitrate. Rates of ammonium uptake for the entire community and for seagrass leaves and epiphytes were significantly dependent on bulk velocity, bottom shear stress, and the rate of turbulent energy dissipation. / ABSTRACT: Relationships between uptake rates and these parameters were consistent with mass-transfer theory and suggest that the effect of water flow on ammonium uptake is the same for the benthos as a whole and for the organisms that form the canopy. In addition, epiphytes on the surface of T. testudinum leaves were shown to depress leaf uptake by an amount proportional to the area of the leaf covered by epiphytes. Water flow influenced rates of nitrate uptake for the community and the epiphytes; however, uptake rates were depressed relative to those for ammonium suggesting that uptake of nitrate was also affected by biological factors such as enzyme activity. Epiphytes reduced uptake of nitrate by the leaves; however, the amount of reduction was not proportional to the extent of epiphyte cover, which provided further evidence that nitrate uptake by T. testudinum leaves was biologically limited. / ABSTRACT: As an additional component of the research, hydrodynamic regime of a mixed seagrass and coral community in Florida Bay was characterized using an acoustic Doppler velocimeter. Hydrodynamic parameters estimated from velocity data were used in mass-transfer equations to predict nutrient uptake by the benthos over a range of water velocity. Measured rates of uptake from field flume experiments conducted in the same community confirmed that hydrodynamic data could be used to accurately predict nutrient transport to the benthos under natural flow conditions. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Coral reef habitats are being threatened by global warming, natural disasters and the increased pressure of the global population. These habitats are in urgent need of efficient monitoring and management programs to sustain their biological, economic and cultural values for the global community. Habitats maps, describing the extent, composition and the condition of the benthos in time and space, form a valuable information source for scientists and managers to answer their management questions. Adequate and accurate habitat maps are needed and can be provided by a range of mapping approaches, which are based on integration of field and remotely sensed image data sets. Scientists, technicians and managers lack knowledge on the cost effectiveness and procedures for calibrating and validating mapping approaches that integratef field data and remote sensing imagery, for use in various coral reef and seagrass environments. This knowledge is required to adequately design, apply and assess operational mapping approaches and their maps. Hence, the aim of this study is to improve habitat mapping capabilities by integrating low cost remote sensing approaches and field-calibration and -validation methods for a range of coral reef and seagrass environments. To achieve this aim, commonly used habitat mapping approaches that integrated field-calibration and -validation methods with remote sensing image based processing techniques were studied, in different coral reef and seagrass environments in Fiji and Australia. These environments varied in: water clarity, water depth, benthic composition, spatial complexity of benthic features, and remoteness. The study had three objectives: (1) to evaluate the accuracy, cost and perceived relevance of eight commonly used benthic cover mapping approaches for three different coral reef environments. (2) Conduct a cost-benefit comparison of two field survey methods for calibrating and validating maps of coral reef benthos derived from high-spatial resolution satellite images in three different coral reef environments. (3) Identify considerations for comparing the thematic accuracy of multi-use image based habitat maps in various coral reef and seagrass environments. A scientific assessment and an evaluation of the relevance for managers, was conducted on eight commonly used habitat mapping approaches for three different coral reef environments. This analysis revealed a preference for a mapping approach based on supervised classification of Quickbird imagery integrated with basic field data. This approach produced an accurate map within a short time with low cost in that suited the user’s purpose. Additionally, the results indicated that user preference in selecting a suitable map was affected by: variations in environmental complexity; map purpose, and resource management requirements. To assess the variation in performance of methods for calibration and validation for coral reef benthic community maps, derived from high-spatial resolution satellite images, a comparison was conducted between spot check and georeferenced photo-transect based mapping approaches. The assessment found that the transect based method was a robust procedure which could be used in a range of coral reef environments to map the benthic communities accurately. In contrast, the spot check method is a fast and low cost approach suitable to map benthic communities which have lower spatial complexity. However, the spot check approach provides robust results, if it is applied in a standardised manner, providing a description of selected homogenous areas with georeferenced benthic cover photos. Considerations for comparing the thematic accuracy of multi-use image based habitat maps in various coral reef and seagrass environments were assessed. This included a review of 80 scientific publications on coral reef and seagrass habitat mapping, which revealed a lack of knowledge and reporting in regards to the assessment of the thematic map accuracy. These publications commonly used thematic accuracy measures and factors controlling their variation were then determined for various habitat mapping approaches for different coral reefs and seagrass environments. Assessment of these measures found that variations in accuracy levels were not only a result of actual differences in map accuracy, but were also due to: spatial complexity of benthic features present in the study area; distribution of the calibration and validation samples relative to each other, and the level of detail provided by these samples. Two main outcomes resulted from this dissertation. The first was the development of a robust mapping approach based on georeferenced photo-transect method integrated with high spatial resolution imagery, which is able to accurately map a variety of coral reef and seagrass habitats. The second outcome is an increase in capacity for coral reef and seagrass habitat mapping by scientists and managers. This increase is accomplished by providing knowledge on various habitat mapping approaches in regards to their: cost/time, accuracy and user relevance; performance of calibration and validation field methods; and performance of accuracy measures, when applied in a range of coral reef and seagrass environments. The findings and outcomes from this dissertation will significantly contribute to management of coral reef and seagrass environments by enabling scientists and managers to choose appropriate combinations of: field and image data sources; processing approaches, and validation methods for habitat mapping in these environments.

Includes bibliographical refe / xiv, 171 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the causes and consequences of a sudden dieback of intertidal and shallow subtidal seagrasses along 95 km of the eastern coast of Spencer Gulf, South Australia. Concludes with a conceptual model specific to shallow waters of Spencer Gulf where climatological extremes and geological processes are the main environmental factors influencing the processes of seagrass dieback and subsequent recolonisation and succession. / Thesis (Ph.D.)--Adelaide University, Dept. of Environmental Biology, 2001

[Truncated abstract] Biogeochemical processes in seagrass sediments influence growth and nutrition of seagrasses. This thesis investigates the below-ground interactions between biotic and abiotic factors that influence seagrass nutrition and growth, with focus on a small species of seagrass, Halophila ovalis (R. Br.) Hook ƒ., from the Swan River Estuary, Western Australia. Seagrass showed significantly lower growth and an increase in leaf nitrogen and phosphorus concentrations with increased organic matter loading. With maximal light reduction, lower growth rates and average leaf weights were observed, and leaf nitrogen and phosphorus concentrations were higher. Light reduction was also shown to increase bioavailability of inorganic nutrients within porewater of seagrass sediment . . . Sulphide was hypothesised to have an inhibitory effect on nutrient uptake of Halophila ovalis. Below-ground sulphide inhibits the photosynthetic efficiency of photosystem II at sulphide concentrations greater than 1 mM. Sulphide exposure enhanced phosphate uptake, with no significant effect on ammonium uptake of H. ovalis. This thesis demonstrates that biogeochemical processes both constrain the potential growth of seagrasses and influence the nutrient status of seagrass tissue. Consideration of the influence of sulphide stress on seagrasses is likely to be particularly important for anthropogenically influenced aquatic systems, where inputs of organic matter are enriched relative to pristine ecosystems. A better understanding of biogeochemical processes will allow researchers to predict how future changes in sediment chemistry will influence seagrass meadows.

ix, 60 leaves : maps ; 28 cm Notes Typescript Thesis (M.S.)--University of Oregon, 1983 Includes vita and abstract Bibliography: leaves 56-60 Another copy on microfilm is located in Archives

Seagrasses are the only group of submerged plants that are permanently growing in marine environment. They play an important role in the sea bottom ecosystem. Seagrasses are primary producers capable of accumulation and deposition of carbon. They influence water flow at the sea bottom and form symbioses with variety of organisms. Our knowledge of symbiotic interactions of seagrasses is still limited even though several studies of the topic have been carried out in recent years. Unlike most of terrestrial plants, seagrasses are generally considered as plants that do not form any specific associations with mycorrhizal or endophytic fungi. Surprisingly, we have discovered a novel fungal endophytic association in roots of Mediterranean endemic seagrass species Posidonia oceanica (L.) Delile. Morphology of this symbiotic fungi strongly resembles common symbiotic fungi of terrestrial plants, dark septate endophytes (DSE). We sampled roots of P. oceanica in large area of the Mediterranean from southeastern Spain to Albania and described range and taxonomical classification of the endophyte using microscopy, in vitro cultivation and molecular determination. Roots of P. oceanica in whole area of study are colonized by mere two endophytic fungal species. Over 90 % of the fungal symbionts belong to a single...

<p>The present study is one of the first attempts to analyze the societal importance of seagrasses (marine flowering plants) from a Natural Resource Management perspective, using a social-ecological systems (SES) approach. The interdisciplinary study takes place in East Africa (Western Indian Ocean, WIO) and includes in-depth studies in Chwaka Bay, Zanzibar, Tanzania. Natural and social sciences methods were used. The results are presented in six articles, showing that seagrass ecosystems are rich in seagrass species (13) and form an important part of the SES within the tropical seascape of the WIO. Seagrasses provide livelihoods opportunities and basic animal protein, in from of seagrass associated fish e.g. Siganidae and Scaridae. Research, management and education initiatives are, however, nearly non-existent. In Chwaka Bay, the goods and ecosystem services associated with the meadows and also appreciated by locals were fishing and collection grounds as well as substrate for seaweed cultivation. Seagrasses are used as medicines and fertilizers and associated with different beliefs and values. Dema (basket trap) fishery showed clear links to seagrass beds and provided the highest gross income per capita of all economic activities. All showing that the meadows provide social-ecological resilience. Drag-net fishery seems to damage the meadows. Two ecological studies show that artisanal seaweed farming of red algae, mainly done by women and pictured as sustainable in the WIO, has a thinning effect on seagrass beds, reduces associated macrofauna, affects sediments, changes fish catch composition and reduces diversity. Furthermore, it has a negative effect on i.a. women’s health. The two last papers are institutional analyses of the human-seagrass relationship. A broad approach was used to analyze regulative, normative and cultural-cognitive institutions. Cooperation and conflict take place between different institutions, interacting with their slow or fast moving characteristics, and are thus fundamental in directing the system into sustainable/unsustainable paths. Ecological knowledge was heterogeneous and situated. Due to the abundance of resources and high internal control, the SES seems to be entangled in a rigidity trap with the risk of falling into a poverty trap. Regulations were found insufficient to understand SES dynamics. “Well” designed organizational structures for management were found insufficient for “good” institutional performance. The dynamics between individuals embedded in different social and cultural structures showed to be crucial. Bwana Dikos, monitoring officials, placed in villages or landing sites in Zanzibar experienced four dilemmas – kinship, loyalty, poverty and control – which decrease efficiency and affect resilience. Mismatches between institutions themselves, and between institutions and cognitive capacities were identified. Some important practical implications are the need to include seagrass meadows in management and educational plans, addressing a seascape perspective, livelihood diversification, subsistence value, impacts, social-ecological resilience, and a broad institutional approach.</p>

The goal of this study was to develop an alternative approach to typical seagrass transplantation techniques that damage the donor bed. Floating individuals of Halodule wrightii were collected in the Indian River Lagoon (IRL), Florida, during fall of 2013 and spring of 2014, with the fall collection planted in outdoor tanks. Only 25% of individuals collected in the fall survived the winter in the tanks. Individuals from both collections were deployed onto biodegradable mats in a capped dredge hole in the IRL in March, 2014. Approximately 66% of the mats survived the six-month experiment, and the area covered by seagrass quadrupled. Growth in shoot count, average height, horizontal spread, and biomass was similar for both fall and spring treatments. Thus, time and effort of overwintering had no benefit over spring harvesting. The use of floating individuals can provide a more practical, environmentally friendly alternative to traditional transplanting for seagrass re storation. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection