Extracting ecological metrics from archeological surveys of shipwrecks using submersible video and laser‐line scanning

Abstract

Ecological metrics derived from habitat surveys can provide information necessary to understand population, community, and ecosystem processes. Here, we present a case study on the feasibility of extracting ecological metrics from archeological studies of shipwrecks. Even though shipwrecks that are the focus of archeological surveys also form habitat for diverse flora and fauna, shipwrecks are often studied separately by archeologists and ecologists. Conducting joint archeological and ecological surveys promises to maximize research resources and outputs, yet this cross-disciplinary approach is rare. Here, we test the feasibility of extracting ecological metrics from archeological surveys of two historically significant and deep (200 m) shipwrecks, the German U-boat U-576 and the Nicaraguan freighter SS Bluefields, which sank in close proximity to one another on the continental shelf of North Carolina, USA during World War II. First, we assessed fish density, community composition, behavior, and spatial distribution on these shipwrecks using video and laser-line scanning data collected from human-occupied submersibles during archeological surveys. Second, we examined the ecological benefits and biases of pairing laser-line scanning and video surveys designed for archeological specifications. Our approach allowed us to pinpoint locations of fish around the shipwrecks and to identify these fish to fine taxonomic levels. The extracted ecological data revealed that both shipwrecks hosted high densities (U-576 38.2 AE 4.0; SS Bluefields 32.0 AE 18.0 per along-ship transect) of demersal fishes, including grouper species, and that fish concentrated around high-relief shipwreck features. More broadly, our findings demonstrate the utility and benefits of collecting multipurpose and cross-disciplinary data and provide a proof-of-concept for conducting joint archeological and ecological studies.

Shipwreck ecology: Understanding the function and processes from microbes to megafauna

“… 2019a , Johnson et al. 2020 ). Photogrammetry has been used not only to develop 3D models of shipwrecks but to measure cover and growth of benthic invertebrates (Olinger et al.…”

Four decades of reef observations illuminate deep‐water grouper hotspots

“…We also excluded fish trap and stationary or bottom‐lander video data since these observations cannot be directly compared to density metrics from transect‐type data. Given that the initial observations (Johnson et al., 2020) were of high counts of large‐bodied groupers in deep habitats, we focused on grouper species within the genera Epinephelus , Hyporthodus , and Mycteroperca , all within the family Serranidae (Fricke et al., 2020). We included observations from structured habitats, including natural rocky reefs, artificial reefs, and shipwrecks, on the shelf‐edge and upper slope between 50 and 300 m deep off the SEUS states (Cape Hatteras, North Carolina (NC) to Cape Canaveral, Florida (FL)).…”

“…On 24–26 and 28 August 2016, HOVs collected video of fish communities on two deep shipwrecks (Johnson et al., 2020). The two World War II era shipwrecks, the U‐ 576 and the SS Bluefields , sank in 1942 and rest 241 m from each other off NC (Figure 2).…”

“…Aggregations of typically non‐schooling fish species outside of spawning events and around habitats that do not appear to offer extensive prey or shelter are rarely reported. Direct observations of very high counts of large‐bodied groupers, such as snowy grouper ( Hyporthodus niveatus , Serranidae) and Warsaw grouper ( H. nigritus , Serranidae) (Figure 1) (Johnson et al., 2020) residing on deep, small, and isolated shipwrecks, seem to contradict the notion that aggregations outside of spawning events and away from habitats with prey and shelter are rare. Snowy and Warsaw grouper are generally not believed to be schooling fishes nor are they known to form spawning aggregations (Coleman et al., 1999; Farmer et al., 2017; Farmer & Karnauskas, 2013; Kolmos et al., 2019; Sadovy, 1990; Sedberry et al., 2006).…”

Spatial and temporal variability in geomorphic change at tidally influenced shipwreck sites: The use of time‐lapse multibeam data for the assessment of site formation processes

“…Historic shipwrecks are of interest from many different perspectives (Firth, 2018), as objects of cultural heritage and archaeological value (Delgado & Varmer, 2015; Elkin et al, 2020), as hidden pollution sources (Landquist et al, 2013; Vanninen et al, 2020), as habitats for marine life (e.g., Bałazy et al, 2019; Johnson et al, 2020), and as indicators of local oceanographic and seabed morphodynamic conditions (Caston, 1979; Garlan et al, 2015; Geraga et al, 2020). Their preservation state is a result of site formation processes that comprise various natural and anthropogenic influences (O'Shea, 2002; I.…”