Damage and recovery assessment of vessel grounding injuries on coral reef habitats by use of georeferenced landscape video mosaics

Abstract

Vessel groundings are a major source of disturbance to coral reefs worldwide. Documenting the extent of damage caused by groundings is a crucial first step in the reef restoration process. Here, we describe the application of a novel survey methodology, landscape video mosaics, to assessment of the damage caused by vessel groundings. Video mosaics, created by merging thousands of video frames, combine quantitative and qualitative aspects of damage assessment and provide a georeferenced, landscape, high‐resolution, spatially accurate permanent record of an injury. The scar in a Florida reef impacted by a 49‐foot vessel, imaged in 2005 and 2006, covered an area of 150 m2 (total imaged area was >600 m2). The impacted coral community showed limited signs of coral recovery more than 3 years after the initial impact; the cover of corals was still significantly higher in the undamaged areas compared to the scar. However, seagrass colonization of the scar was observed. Finally, no evidence of further physical impacts was documented even when four hurricanes passed near the grounding site in 2005. The video mosaics developed in this study proved to be ideal tools to survey the grounding scars. Mosaics provide a means to collect information on the size of the damage area and the status and trends of the impacted biological communities and provide a permanent visual record of the damage, thereby expanding the quality and diversity of information that can be collected during field surveys.

Image Blending Techniques and their Application in Underwater Mosaicing

“…Nowadays, underwater surveys have numerous scientific applications in the fields of archeology [38], geology [145,37] and biology [102], involving tasks such as ancient shipwreck prospection [24], ecological studies [63,77], environmental damage assessment [43,76] or detection of temporal changes [22], just to name a few.…”

Fixed‐station monitoring of a harbour wall community: the utility of low‐cost photomosaics and scuba on hard‐substrata

“…scatter) can be limited by collecting imagery closer to the substratum, although this reduces the overall sample area, additional imagery can be collected from the surrounding area and mosaicked to increase the final sample size (Burton et al , ; van Rein et al , ). Indeed, image mosaics encompassing 400 m² of sea bed have been used to assess coral reef communities in the tropics (Lirman et al , ; Gleason et al , ). Furthermore, it is generally agreed that optical methods collect data quickly, achieve greater sampling objectivity than traditional diver observations, generate permanent survey records and have a low ecological impact in sensitive areas of conservation importance (Bohnsack, ; Preskitt et al , ; Moore et al , ; Barrett et al , ; Cabaitan et al , ; Leujak and Ormond, ).…”

Image-Based Coral Reef Classification and Thematic Mapping

“…These large-area representations (commonly known as image mosaics) are obtained by registering and blending large sets of individual images acquired at close range [32][33][34].…”

“…The mosaic is created using the methods by [32][33][34] from survey images (283 high-resolution digital still images and rendered at 1 mm per pixel) of shallow water coral reefs in the Red Sea, near Eilat [37]. The mosaic covers an area of 19.2 square meters.…”