Deep-sea infauna with calcified exoskeletons imaged in situ using a new 3D acoustic coring system (A-core-2000)

Abstract

The deep ocean is Earth’s largest habitable space inhabited by diverse benthic organisms. Infauna play crucial roles in shaping sedimentary structures, relocating organic matter, porewater chemistry, and hence biogeochemical cycles. However, the visualization and quantification of infauna in situ inside deep-sea sediment has been challenging, due to their sparse distribution and that deep-sea cameras do not visualize animals living below the sediment surface. Here, we newly developed a 3D acoustic “coring” system and applied it to visualize and detect burrowing bivalves in deep-sea sediments. The in situ acoustic observation was conducted at a dense colony of vesicomyid clams in a hydrocarbon seep in Sagami Bay, Japan, focusing on a patch of juvenile clams with a completely infaunal life style. We clearly observed strong backscatters from the top and lower edges of animals in our 3D acoustic data. At least 17 reflectors were identified in the survey area (625 cm2), interpreted to correspond to living clams. The estimated depths of the lower edge of clams ranged between 41 and 98 mm. The acoustic system presented here is effective for detecting and monitoring infauna with calcified exoskeletons. This novel tool will help us better assess and understand the distribution of deep-sea infauna, particularly those groups with hard exoskeletons, as well as biogeochemical cycles.

Heterogeneity on the abyssal plains: A case study in the Bering Sea

“…From previous comparisons of sampling gears, it is clear that each method has a different efficiency in capturing various faunal groups (Montagna et al, 2017;Joźẃiak et al, 2020;Lins and Brandt, 2020), which is to be expected as they have been designed for different purposes and for collecting different taxa. Revealing the 'hidden' infaunal biodiversity of the Aleutian Basin requires additional extractive sampling, though recent and ongoing breakthroughs in acoustic imaging methods provide promising avenues for future developments (Mizuno et al, 2022).…”

“…Video and still camera data can provide high resolution information regarding the seafloor habitat, but only limited information about benthic biodiversity. Abyssal-plain biodiversity is dominated by meio-and "macro-" faunal species (typically defined as species retained by 63 µm or 300 µm mesh sieves, respectively) that cannot be resolved from image data, either because they are too small and/or live below the sediment surface (Mizuno et al, 2022). Nonetheless, even early imaging methods were considered highly cost effective for surveying megafauna (Uzmann et al, 1977), often defined as those larger than 1 cm or so and that can be recognised in seafloor images (Rybakova et al, 2020).…”

“…Nonetheless, even early imaging methods were considered highly cost effective for surveying megafauna (Uzmann et al, 1977), often defined as those larger than 1 cm or so and that can be recognised in seafloor images (Rybakova et al, 2020). Image-based methods generally have higher positional accuracy and are less destructive (Diaz, 2004;Ayma et al, 2016;De Mendonca and Metaxas, 2021;Mizuno et al, 2022). They can also be implemented at long-term seafloor observatories to collect time-series data (Soltwedel et al, 2005;Taylor et al, 2017).…”

Broad distribution of spider-shaped lebensspuren along the Australian continental margin

“…Many deep-sea investigations rely on imagery which has advanced by leaps and bounds in recent years (Durden et al, 2016). Nevertheless, deep-sea imagery rarely allows for the detection of infauna (but see Mizuno et al, 2022), and we are instead reliant on direct surface detections of infauna during reproduction or feeding (Ohta, 1984), or indirectly via lebensspuren.…”

Data Analysis in Deep-Sea Mineral and Organism Interplay: A Review

“…Such reviews can provide insights into the complex interplay between deep-sea mineral resources and the organisms that inhabit these regions. They can highlight knowledge gaps, guide future research, and inform policy decisions to ensure that the pursuit of economic gains does not come at the expense of ecological sustainability [4].…”