From ecosystems to people: examining the variability in the provision of ecosystem services by eelgrass meadows in Atlantic Canada

Prystay, Tanya S. (2023) From ecosystems to people: examining the variability in the provision of ecosystem services by eelgrass meadows in Atlantic Canada. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Seagrass meadows provide functions that support other species and ecosystem services that directly and indirectly benefit human wellbeing. However, growing in estuarine environments, seagrass meadows are exposed to interacting pressures from terrestrial and marine systems, resulting in their degradation worldwide. Efforts to conserve these social-ecological systems have met challenges, including insufficient maps to assess seagrass status and value, a limited understanding of seagrass meadow ecosystem traits underpinning the provision of ecosystem services, and a lack of public awareness necessary to support management decisions. This thesis presents multidisciplinary studies of eelgrass (Zostera marina) meadows in Placentia Bay, Newfoundland and Labrador, Canada, that contribute toward addressing these challenges. In the first study, I evaluated the reproducibility of using remotely piloted aircraft systems (RPAS) to collect seasonal maps of submerged eelgrass meadows in a temperate environment. I show that higher altitude surveys are beneficial when surveying in rapidly changing environments; however, RPAS surveys using three-colour band imagery alone may be insufficient to discriminate seasonal changes. In the second and third studies, I identified meadow structural and environmental traits underpinning eelgrass service as fish habitat and function as a coastal filter. In the second study, I show that shallower and more saline eelgrass meadows enhance diversity in fish life history traits. In the third study, I show that carbon and nitrogen content in the surface sediment was negatively related to sediment density, where isotopic ratios indicated that the carbon was predominantly derived from marine allochthonous (non-eelgrass) sources. Lastly, in the fourth study, using an online survey, I show strong awareness of eelgrass by Canadian coastal Atlantic community members, and support for conservation efforts. Participants identified fish habitat, coastal protection, and water quality maintenance as the three most important ecosystem services provided by eelgrass in Atlantic Canada. Together, the components of this thesis characterise three Newfoundland and Labrador eelgrass meadows, the services they provide, and synthesises the perception of eelgrass by Canadian coastal Atlantic community members. These findings are relevant to local management decision-making and eelgrass monitoring, while also contributing to the growing global characterization of the variability in eelgrass meadow function driving ecosystem services.

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