Open Collections

Douglas, Tristan

University of British Columbia

Intertidal mudflats are among the most productive coastal ecosystems, sustaining diverse food webs and globally significant populations of migratory shorebirds. Microphytobenthic (MPB) biofilms—key primary producers in these systems—exhibit highly dynamic spatial and temporal patterns shaped by tidal cycles, seasonal shifts, and geomorphology. Despite their ecological importance, MPB biofilms remain challenging to monitor at the spatial and temporal scales necessary to understand their role in ecosystem function and shorebird foraging. Traditional field sampling is labor-intensive and spatially constrained, while satellite remote sensing lacks the spatial and temporal resolutions to capture fine-scale variability. This dissertation develops, applies, and tests unoccupied aerial vehicle (UAV)-based remote sensing methodologies to quantify MPB biomass and mudflat morphology with unprecedented detail across spatial and temporal scales. These tools were used to investigate biofilm dynamics in the Fraser River Estuary, globally significant shorebird stopover on coastal British Columbia. UAV photogrammetry was evaluated for reconstructing fine-scale mudflat topography, demonstrating that UAV-derived digital surface models (DSMs) achieved sub-centimeter accuracy across a variety of UAV data acquisition parameters. An empirical calibration model linking UAV-acquired multispectral reflectance to in situ sediment photopigment measurements several reliable spectral indeces for estimating MPB biomass. Large-scale MPB distribution was examined across estuary sites with contrasting sedimentation regimes, revealing that sediment-deprived areas may exhibit fragmented, lower-biomass biofilm patches. Building on these spatial analyses, MPB dynamics were investigated across diel tidal cycles and seasons. A consistent diel pattern was observed, with MPB biomass peaking post-emersion in the early afternoon before declining prior to tidal immersion, aligning with shorebird foraging activity. Seasonally, the highest MPB biomass occurred in fall and winter, while the expected springtime increase in biomass appeared to be suppressed by unseasonably cold conditions during the year of study. These findings establish UAV-based remote sensing with high-resolution multispectral imagery as a versatile tool for monitoring intertidal biofilms, capturing fine-scale MPB dynamics with high accuracy. By linking environmental factors to MPB biomass and mapping biofilm at spatial and temporal scales relevant to shorebird foraging, this research provides new tools for habitat monitoring and the development of conservation climate change mitigation strategies.

Text

2025-05-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/91223

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/