Seasonality of a short-lived seagrass relative to environmental factors and the development of an adaptable, functional-structural plant model

Sam Whitehead

    Research output: ThesisMaster's Thesis

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    The aim of this study was to investigate the relationships between H. stipulacea seasonality and environmental variables, to appraise the feasibility of transplantation in the Persian Gulf (Gulf) and to develop a spatially-explicit, functional-structural plant model (FSPM), where the growth rate of simulated seagrass rhizomes is linked with environmental conditions.
    Understanding the drivers of seagrass seasonality is critical to informed management of this important marine habitat. In Chapter 2 I demonstrate that H. stipulacea was predominantly short-lived and growth was strongly associated with light irradiance, which is highest in spring and summer. Seagrass rhizomes grew rapidly in spring. The burrowing of crabs in summer and the smothering by mobile macroalgal mats in winter had marked influences on seagrass mortality. Despite the marked seasonality of water temperature, it provided only partial explanation for seagrass growth rate and total rhizome length and this warrants further investigation at shorter sampling intervals and in laboratory controlled conditions.
    Extensive coastal development in the Persian Gulf includes large-scale land reclamation projects and there have been recent efforts to offset development impacts by transplanting seagrass from the construction footprint into adjacent areas. The outcomes of a trial H. stipulacea transplantation project are also reported in Chapter 2. Although transplantation did not have a significant impact on seagrass growth or survival, almost complete senescence occurred in both transplanted and reference seagrass plots by early spring due to natural seasonality. Thus, transplantation of H. stipulacea from and into markedly seasonal environments of the Gulf is unlikely to produce persistent meadows and it should not be considered to be an appropriate mechanism for offsetting habitat losses from construction.
    Functional-structural plant models use data describing plant function and structure to simulate higher orders of plant growth. They are useful for integrating current understanding, identifying knowledge gaps and can be used to assess the possible outcomes of management strategies, such as transplantation. In Chapter 3 I report the development and validation of the first spatially-explicit FSPM for seagrasses where rhizome growth rate is controlled by environmental conditions. The model predictions matched empirical data well, although there was more variability in the predictions and the model parameterisation or H. stipulacea requires further refinement. This model was designed to be easily adapted for use with other species and environmental conditions and is freely available using open-source software.
    Original languageEnglish
    Publication statusUnpublished - 2015


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