Abstract
Abstract. Structure-from-motion (SfM) has emerged as a popular method of characterizing marine benthos in tropical marine environments and could be of tremendous value to glass sponge monitoring and management efforts in the Northeast Pacific Ocean. However, temperate marine environments present a unique set of challenges to SfM workflows, and the combined impact that cold, dark, and turbid waters have on the veracity of SfM derived data must be critically evaluated in order for SfM to become a meaningful tool for ongoing glass sponge research. This paper discusses the design, development, testing, and deployment of an innovative underwater SfM workflow for generating high-resolution 3D models in temperate marine environments. This multi-phase research project (dry-lab, wet-lab, and field), while possibly seen as unconventional, was designed to innovate in two ways. First to build an operational data capture platform to support low-cost SfM-based seafloor surveys. And second, to enable systematic isolation and evaluation of SfM data capture parameters and their implications for representational veracity and data quality. This paper reports the challenges and outcomes from a series of field surveys conducted in Howe Sound, BC, one of which serves as the first of two data sets in a temporal analysis of 3D morphometric change. This research demonstrates that accurate, high-resolution morphometric characterization, of all benthic species and habitats, is dependent on a range of equipment, procedural, and environmental variables. It is also intended to share our applied problem-solving path to successful 3D capture, backed up by robust data science.
Highlights
The glass sponge reefs found throughout the western Canadian continental shelf are considered a key structural habitat due to their uniqueness, delicacy, and role in maintaining ecosystem dynamics (Fisheries And Oceans Canada, 2010)
Effective monitoring efforts are inhibited by insufficient pragmatic indicators of glass sponge reef function stemming from their relative inaccessibility and a reliance on traditional 2D metrics that are subjective, time consuming, prone to error, and provide an inadequate characterization of the complex 3-D structure of glass sponges
Habitat complexity is a critical attribute of underwater ecosystems, as kelp forests, coral reefs, and glass sponge reefs support a variety of marine fish and invertebrates, and higher levels of structural complexity are linked to increased biodiversity, productivity, and survivorship (Connell & Jones, 1991; Gratwicke & Speight, 2005)
Summary
The glass sponge reefs found throughout the western Canadian continental shelf are considered a key structural habitat due to their uniqueness, delicacy, and role in maintaining ecosystem dynamics (Fisheries And Oceans Canada, 2010). Glass sponge reefs support a variety of marine fauna, including bryozoans, gastropods, crustaceans, echinoderms, and fish (most notably, several species of rockfish) (Chu & Leys, 2010; Krautter, Conway, Barrie, & Neuweiler, 2001; Marliave, Conway, Gibbs, Lamb, & Gibbs, 2009). This ecological productivity attracts many commercial fisheries, resulting in an estimated 253 tons of coral and sponge bycatch between 1996 and 2002 (Leys, Mackie, & Reiswig, 2007) and widespread reports of damage There is a lack of published SfM research in temperate marine environments where the collective impact of cold, dark, nutrient-rich waters on photograph, and by extension, SfM data quality is unknown
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