The use of emerging techniques to understand seagrass ecosystems: Case studies using Posidonia oceanica in the Eastern Aegean

Meek, Sarah

Abstract

Seagrass meadows are vital coastal habitats that support a wide array of species and provide numerous ecosystem services. The area of seagrass meadow has declined significantly, at a rate of about 5% per year, since 1980. Emerging techniques for seagrass research has the potential to provide new insights to fill knowledge gaps and improve our understanding of seagrass ecological function and ecosystem services. This improved understanding will help us to inform policy makers about protection measures. Using Posidonia oceanica dominated habitats as a case study, this thesis assesses emerging techniques for mapping seagrass habitats, monitoring biodiversity with seagrass habitats and assessing microplastic pollution loads within seagrass sediments.

Kayak-borne down-scan sonar is shown to provide an accurate and cost-effective method for mapping the distribution of seagrass meadows. Sonar-derived data suggested current estimates of seagrass extent in the Aegean, based on analysis of satellite imagery, may contain considerable inaccuracies particularly in areas of complex bathymetry. It is suggested that kayak-borne sonar mapping can provide accurate reference data for larger scale satellite mapping, delivering benefits in terms of our ability to survey seagrass distribution and monitor temporal changes in extent and health.

Environmental DNA is proven to be an effective tool for the non invasive detection of, Pinna nobilis, a culturally important yet Critically Endangered bivalve species associated with P. oceanica habitats. The technique developed in this study is capable of detecting concentrations of DNA as low as 5.50 x 10-10 ng µl-1 from sea water samples. This technique can be used at different spatial scales dependent on the season, allowing eDNA to be a sensitive and precise tool in locating and identifying a key species inhabiting seagrass meadows.

A fine-scale analysis of microplastic distribution within the sediment under a seagrass meadow using recently developed Sediment Microplastic Isolation techniques, indicated that seagrass did not influence the deposition of microplastics to sediment at a semi isolated bay. Microplastics were recovered at relatively low densities across the entire study area. Analysis of sediment patterns suggested that most sediment input was from terrestrial sources immediately adjacent to the seagrass bed and, therefore, that seagrass beds that are closer to terrestrial sources of microplastic pollution are likely to show much greater microplastic loadings.

It is concluded that, emerging techniques such as down-scan sonar, eDNA and microplastic extraction can provide novel insights into the distribution and ecological functioning of seagrass habitats. These insights provide avenues for the development of existing monitoring methods and for conservation policies.

Citation

Meek, S. The use of emerging techniques to understand seagrass ecosystems: Case studies using Posidonia oceanica in the Eastern Aegean. (Thesis). University of the West of England. Retrieved from https://uwe-repository.worktribe.com/output/6442771

• Thesis Type: Thesis
• Deposit Date: Jul 31, 2020
• Publicly Available Date: Dec 16, 2020
• Public URL: https://uwe-repository.worktribe.com/output/6442771
• Award Date: Dec 16, 2020