Monitoring of marine benthos with an hyperspectral camera: a first in the Mediterranean

Habitat destruction is one of the main causes of the decline of marine biodiversity and fisheries resources. An artificial reef can be considered as a tool to protect or restore these habitats and their declining biodiversity. The Barcelona Convention defines artificial reefs as "structures specifically built to protect, regenerate, concentrate and / or increase the production of biological marine resources, whether for fishing or nature conservation, which includes the protection and protection of the environment. regeneration of habitats ". In response to these problems, nearly 88,000 m3 of artificial reefs, mostly made of concrete, have been deployed on the Mediterranean coast of France for some thirty years. To date, the assessment of reef performance has focussed primarily on fish communities and has almost completely ignored the development of epibiosis (biofilm and macrofouling). Historically in the Mediterranean, the first published works in the 70s deal with the species of macrofouling. Thereafter, during the last decades, most of the works focussed on the fish assemblages. However, the biofilm (mainly bacteria and unicellular micro-algae) and macrofouling (mostly algae and fixed invertebrates) are the first elements of the food web that will allow the installation and development of the fauna of large invertebrates (crustaceans) and fish on or around artificial reefs.

In November 2017, 6 large 3D printed artificial reefs were immersed in the Larvotto marine protected area (Monaco). ECOMERS and BOREA (Museum of Natural History of Paris), in collaboration with AMPN, launched a long-term monitoring of these reefs, including an analysis of biofilm and macrofouling.

To answer this, an innovative technique is being tested with the use of an immersible hyperspectral camera. This camera is developed by PlanBlue, a start-up from the Max Planck Institute (Germany). Briefly, hyperspectral imaging is a technique combining imaging and spectroscopy where each image is taken for a narrow band of the electromagnetic spectrum. For example, the human eye sees light in three bands (red, green, and blue) while hyperspectral imaging can 'see' in a very large number of bands typically ranging from visible to near infrared. Each species has a particular signature (hyperspectral image) that can be used to identify it. The development of a submergible camera allows to acquire underwater scuba images of different substrates colonized and thus to quickly have a precise identification (species or genus) of the species present. This speed and ease of identification are the main highlights of this camera. Once the validation is done (association between a light spectrum and a species or group of species), it will then be easy to determine the composition of the macrofouling species. Moreover, this promising technology go further than the simple identification of species. This camera can also give information about the physiological activities of photosynthetic species growing over the time.

This innovative technique has never been used in the Mediterranean. Its development in Monaco by ECOMERS and AMPN in partnership with CREOCEAN and its validation as a method of monitoring the macrofouling will be a first. This technique could subsequently be used in the monitoring of the benthos, whether on artificial or natural substrate. The prospects of application far exceed the only artificial reefs.

Photos P. Francour: Test and calibration of the hyperspectral camera in shallow habitats

Oceanographic Museum of Monaco, June 20, 2018

A conference organized by the Association Monégasque pour la Protection de la Nature (special thanks to Jacqueline Gautier-Debernardi and Jean-Marc Ferrie, AMPN, and to Robert Calcagno and his staff, Oceanographic Museum of Monaco) has be led by Patrice Francour (ECOMERS laboratory and former president of the Scientific Committee Prado Artificial Reefs, Marseille). It focussed on the first Monegasque artificial reefs to the latest reefs, printed in 3D, immersed in November 2017.

The first artificial reefs date back to the 17th century and were submerged in Japan, the undisputed leader in this field. Today, throughout the world, they serve to preserve, restore and improve the coastal ecosystems and related ecological services. Described simply as submerged structures, positioned deliberately on the seabed, they aim to imitate certain characteristics of natural rocky habitats. In the Mediterranean the use of artificial reefs began during the 20th century but only increased in quantity after 2000. In Monaco the first artificial reefs used were those associated with the creation of the Larvotto marine reserve some 40 years ago. In France and Monaco artificial reefs principally provide the means to sustain artisanal fisheries or to restore damaged habitats. Generally speaking they have simple shapes, nothing complex architecturally and for the most part are made of concrete.

The recent increase in the use of artificial reefs has essentially been motivated by the extent of damage to the coastline and the need to find solutions to remedy the problem. But how can an ancient concept of artificial reefs made of concrete evolve to face such a challenge ?

Recent progress in technology has led to the idea of more complex designs of artificial reefs thanks to the use of 3D printing. Using natural materials, mainly sand from the Dolomite, has allowed the creation of ecological reefs. Thanks to the joint efforts of the Monegasque Association for the Protection of Nature, the Boskalis company and the Prince Albert II of Monaco Foundation, six 3D printed reefs were immersed in November 2017 in the Larvotto MPA: a first in the Mediterranean and in the world due to the size of the reefs. The research undertaken by international scientific teams (ECOMERS, BOREA, Boskalis, D-Shape) prior to this project in Monaco was original, innovating and advanced our knowledge in the field of artificial reefs, as much in terms of management (how to put in place a programme for submerging artificial reefs) as in scientific terms (which designs, what materials).

The full presentation can be dowloaded here in French.After the presentation, Elisabeth Riera, (PhD student in ECOMERS lab; her PhD subject deals with the 3D printed artificial reefs immersed in Monaco) and Enrico Dini have joined Patrice Francour to answer the questions of the audience. Enrico Dini, CEO of D-Shape (https://d-shape.com/) is the "father" of the giant 3D printer which printed the 3D ARs. He was also involved in the world first project of 3D printed ARs immersed in Bahrain in 2012.