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Highlights: • We present the first hyperspectral image data from the deep seafloor. • The data were acquired with a new UHI in 4200 m water depth. • Supervised classification is able to detect manganese nodules and fauna. • The UHI is a promising tool for high-resolution seafloor exploration and monitoring. Abstract: Hyperspectral seafloor surveys using airborne or spaceborne sensors are generally limited to shallow coastal areas, due to the requirement for target illumination by sunlight. Deeper marine environments devoid of sunlight cannot be imaged by conventional hyperspectral imagers. Instead, a close-range, sunlight-independent hyperspectral survey approach is required. In this study, we present the first hyperspectral image data from the deep seafloor. The data were acquired in approximately 4200 m water depth using a new Underwater Hyperspectral Imager (UHI) mounted on a remotely operated vehicle (ROV). UHI data were recorded for 112 spectral bands between 378 nm and 805 nm, with a high spectral (4 nm) and spatial resolution (1 mm per image pixel). The study area was located in a manganese nodule field in the Peru Basin (SE Pacific), close to the DISCOL (DISturbance and reCOLonization) experimental area. To test whether underwater hyperspectral imaging can be used for detection and mapping of mineral deposits in potential deep-sea mining areas, we compared two supervised classification methods, the Support Vector Machine (SVM) and the Spectral Angle Mapper (SAM). The results show that SVM is superior to SAM and is able to accurately detect nodule surfaces. The UHI therefore represents a promising tool for high-resolution seafloor exploration and characterisation prior to resource exploitation.

This chapter presents aspects of underwater hyperspectral imaging (UHI) techniques aimed at mapping biogeochemical objects of interest (OOI) on the seafloor. Case examples of instrument-carrying platforms and biogeochemical applications are given. We discuss how to create high resolution, georeferenced, optically corrected digital underwater maps of different habitats, minerals, substrates, and organisms. Corrections for platform speed and direction, inherent optical properties (IOP), optical path length, dynamic positioning, and pitch/roll/yaw are discussed in the context of using UHI-based optical fingerprints (i.e. spectral reflectance in visible wavelengths) of different targets to create maps that can help discriminate, identify, and quantify OOI, and provide statistical information on relevant seafloor features. © 2013 Woodhead Publishing Limited. All rights reserved.

The cold-water coral Lophelia pertusa (Scleractinia, Caryophylliidae) is a key species in the formation of cold-water reefs, which are among the most diverse deep-sea ecosystems. It occurs in two color varieties: white and red. Bacterial communities associated with Lophelia have been investigated in recent years, but the role of the associated bacteria remains largely obscure. This study uses catalyzed reporter deposition fluorescence in situ hybridization to detect the in situ location of specific bacterial groups on coral specimens from the Trondheimsfjord (Norway). Two tissue-associated groups were identified: (i) bacteria on the host's tentacle ectoderm, “Candidatus Mycoplasma corallicola,” are flasklike, pointed cells and (ii) endoderm-associated bona fide TM7 bacteria form long filaments in the gastral cavity. These tissue-bound bacteria were found in all coral specimens from the Trondheimsfjord, indicating a closer relationship with the coral compared to bacterial assemblages present in coral mucus and gastric fluid.

The pseudocolonial coral Lophelia pertusa (Scleractinia, Caryophylliidae) is a eurybathic, stenothermal cosmopolitancold-water species. It occurs in two color varieties, white and red. L. pertusa builds vast cold-water coral reefsalong the continental margins, which are among the most diverse deep-sea habitats. Microbiology of L. pertusa hasbeen in scientific focus for only a few years, but the question of whether the coral holds a host-specific bacterialcommunity has not been finally answered. Bacteria on coral samples from the Trondheimsfjord (Norway) werecharacterized by the culture-independent 16S rRNA gene-based techniques terminal restriction fragment lengthpolymorphism and sequence analysis. L. pertusa revealed a high microbial richness. Clone sequences were dominatedby members of the Alpha- and Gammaproteobacteria. Other abundant taxa were Bacteroidetes, Actinobacteria,Verrucomicrobia, Firmicutes, and Planctomycetes. The bacterial community of L. pertusa not only differed conspicuouslyfrom that of the environment but also varied with both the location and color variety of its host. Therefore,the microbial colonization cannot be termed specific sensu stricto. However, similarities to other coral-bacteriumassociations suggest the existence of cold-water coral-specific bacterial groups sensu lato. L. pertusa-associatedbacteria appear to play a significant role in the nutrition of their host by degradation of sulfur compounds, cellulose,chitin, and end products of the corals anaerobic metabolism. Some coral-associated microbes were regarded asopportunistic pathogens. Dominance of mixotrophic members of the Rhodobacteraceae in white L. pertusa couldexplain the wider dispersal of this phenotype by supplementary nutrition.

The pseudocolonial coral Lophelia pertusa (Scleractinia, Caryophylliidae) is a eurybathic, stenothermal cosmopolitan cold-water species. It occurs in two color varieties, white and red. L. pertusa builds vast cold-water coral reefs along the continental margins, which are among the most diverse deep-sea habitats. Microbiology of L. pertusa has been in scientific focus for only a few years, but the question of whether the coral holds a host-specific bacterial community has not been finally answered. Bacteria on coral samples from the Trondheimsfjord (Norway) were characterized by the culture-independent 16S rRNA gene-based techniques terminal restriction fragment length polymorphism and sequence analysis. L. pertusa revealed a high microbial richness. Clone sequences were dominated by members of the Alpha- and Gammaproteobacteria. Other abundant taxa were Bacteroidetes, Actinobacteria, Verrucomicrobia, Firmicutes, and Planctomycetes. The bacterial community of L. pertusa not only differed conspicuously from that of the environment but also varied with both the location and color variety of its host. Therefore, the microbial colonization cannot be termed “specific” sensu stricto. However, similarities to other coral-bacterium associations suggest the existence of “cold-water coral-specific” bacterial groups sensu lato. L. pertusa-associated bacteria appear to play a significant role in the nutrition of their host by degradation of sulfur compounds, cellulose, chitin, and end products of the coral's anaerobic metabolism. Some coral-associated microbes were regarded as opportunistic pathogens. Dominance of mixotrophic members of the Rhodobacteraceae in white L. pertusa could explain the wider dispersal of this phenotype by supplementary nutrition.