Needs and Gaps in Optical Underwater Technologies and Methods for the Investigation of Marine Animal Forest 3D-Structural Complexity

Paolo Rossi,Panagiotis Agrafiotis,Tali Treibitz,Massimo Ponti,Francesco Mancini,Dimitrios Skarlatos,Torcuato Pulido Mantas,Massimiliano Corsini,Alessandro Ridolfi,Andrea Gori,Leonardo Bassani,Marco Dubbini,Cristina Castagnetti,Roberto Simonini,Eva Turicchia,Sergio Rossi,Alessandro Capra,Matan Yuval,Carlo Cerrano,Joaquim Garrabou,Erica Nocerino,Fabio Menna,Gaia Pavoni,Fabio Bruno,Sara Righi,Nuno Gracias,Pierre Drap,Cristina Linares,Marco Palma,Paolo Cignoni,Jean‐Baptiste Ledoux

doi:10.3389/fmars.2021.591292

Abstract

Marine animal forests are benthic communities dominated by sessile suspension feeders (such as sponges, corals, and bivalves) able to generate three-dimensional (3D) frameworks with high structural complexity. The biodiversity and functioning of marine animal forests are strictly related to their 3D complexity. The present paper aims at providing new perspectives in underwater optical surveys. Starting from the current gaps in data collection and analysis that critically limit the study and conservation of marine animal forests, we discuss the main technological and methodological needs for the investigation of their 3D structural complexity at different spatial and temporal scales. Despite recent technological advances, it seems that several issues in data acquisition and processing need to be solved, to properly map the different benthic habitats in which marine animal forests are present, their health status and to measure structural complexity. Proper precision and accuracy should be chosen and assured in relation to the biological and ecological processes investigated. Besides, standardized methods and protocols are strictly necessary to meet the FAIR (findability, accessibility, interoperability, and reusability) data principles for the stewardship of habitat mapping and biodiversity, biomass, and growth data.

Highlights

Precise maps are nowadays available on the land surface, providing location, extent, and topography of terrestrial ecosystems
Marine animal forests are benthic communities dominated by sessile suspension feeders able to generate 3D frameworks with high structural complexity (Rossi et al, 2017)
Ranging from small to broad spatial scale of marine animal forests (Figure 1), the use of photogrammetry for georeferencing the samples and for spatial data acquisition is a promising tool to study many aspects of these communities and evaluate ecological key parameters, from organism health to the species interactions at the basis of bioconstruction and bioerosion processes. Within this viewpoint paper we mainly focus on optical techniques, in particular photogrammetry

Summary

INTRODUCTION

Precise maps are nowadays available on the land surface, providing location, extent, and topography of terrestrial ecosystems. Acoustic based techniques are well-suited in large areas of interest (from 10 m to 10 km), and acoustic 3D mapping is successfully employed to map a wide portion of the sea floor at various depths, but in case of organism biometry, higher accuracy and resolution techniques are required These systems operate in the long-range acquisition and do not suffer from turbidity, but the resulting 3D reconstructions have low resolution and accuracy compared to the optical ones (Lagudi et al, 2016; Figure 1). Surface autonomous vehicles equipped with acoustic and optical sensors (Stanghellini et al, 2020), and low altitude Unmanned Aerial Vehicle (UAV)-based photogrammetry (Casella et al, 2017; Agrafiotis et al, 2020) can provide important information outlining bathymetric profile, filling the gap between satellite and underwater imagery In the latter case, compensation for water refraction is required (Agrafiotis et al, 2020). It supports the comparison of multi-temporal surveys, automatically extracting useful historical information from segmented regions

DISCUSSION

DATA AVAILABILITY STATEMENT