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Title: Monitoring methods for assessing change in seabed habitats
Author: Rein, Henk B. van
Awarding Body: University of Ulster
Current Institution: Ulster University
Date of Award: 2011
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This research demonstrates the utility of repeat acoustic and photographic surveys for monitoring biotopes and hard-substratum communities in temperate waters. Kappa analysis of results derived from time-lapse backscatter surveys conducted at Church Bay, Rathlin Island (1999,2008 and 2009) indicate that the spatial distribution of biotopes is highly similar between each biotope map, possibly due to the stability of bedforms shaped by the local tidal regime. Maximum change is represented by seasonal and annual changes in the growth of Zostera marina. Changes induced by kelp harvesting are not detected in backscatter data. Low-cost photo-mosaics derived from stills and video imagery of fixed quadrats (1 OO-x-l 00 cm) are compared. Although video-collection is quicker, more species and less-conspicuous taxa are identified from stills imagery. Data extraction using point-intercepts proves efficient and generates data sensitive to 10% community change (N=16), but detects fewer species than the visual estimation measure. Frequency-of-occurrence extraction measures significantly over-estimate benthic cover. Seasonal growth, recruitment and mortality of Caryophyllia smithii, Hymeniacidon perleve and Plocamium cartilagineum are estimated to nearest 0.04 ern? month-l using digitisation. The presence of algal canopies reduce the accuracy of sessile-invertebrate cover estimates in spring and summer. Exploratory analysis of results from photoquadrat surveys conducted at Damicornis Bay, Rathlin Island (2009 and 2010), identifies six distinct sub-communities on a boulder slope. Community variability obscures detection of change. However, analysis of the most dominant sub-community indicates that boulder-slope community shifted, possibly due to local erosion of sediment. Optimal balance between precision, efficiency and species-detection ability for photoquadrats (25-x-25 cm) is 50 points-per-image. Functional groups retain structural relevance of communities, while improving precision, sensitivity and efficiency of data extraction and community-representation measures relative to full-species compositions. Continued monitoring of hard-substratum communities using high-resolution photoquadrats and fixed-photomosaics is recommended.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available