One of the main goals of UBICA within OCEAN CITIZEN is to develop and refine innovative methodologies for environmental monitoring, with a particular emphasis on the use of photogrammetry. This technique allows for the precise reconstruction of three-dimensional models of subjects by utilising standard photographs, taken in large quantities. The main advantages of photogrammetry include its cost-effectiveness, high accuracy, and, with adequate training, its relative ease of application.
In pursuit of these goals, a dedicated field mission was conducted in the Canary Islands, from the 20th to the 27th of October 2024. During this period, a technician from UBICA travelled to Taliarte, Gran Canaria. Over five days, multiple dives at a depth of around 30 m were undertaken to perform photogrammetric scans of three distinct culture racks housing colonies of the black coral Antipathella wollastoni.
Black corals, belonging to the order Antipatharia, owe their name to their dark skeletons, rich in chitin-like proteins, enveloped in living tissue hosting coral polyps. These corals form colonies with diverse morphologies, such as bushy, tree-like, or fan-shaped structures.
A. wollastoni particularly can grow up to a few meters in height under favourable conditions. It thrives on rocky substrates in areas characterised by strong water currents, which facilitates the efficient capture of plankton and organic particles. It also plays an important ecological role as a habitat provider for a variety of marine species, offering shelter and feeding grounds for a wide array of marine species, including fish and invertebrates. Historically overharvested due to its value as an ornament or talisman, for centuries associated with protection and good luck in various cultural traditions, it is now protected under CITES Appendix II. Nonetheless, it remains vulnerable to threats such as habitat destruction and the multifaceted impacts of climate change, including ocean acidification and warming.
The culture racks under study were installed approximately one year ago on the sub-vertical side of the Arona wreck. This merchant vessel, measuring 100 meters in length, sank in 1972 following a catastrophic fire and now rests on the seabed at a depth of 35 meters, roughly 1 kilometer off the coast of Taliarte. The site was strategically selected due to the presence in the vicinity of several large A. wollastoni colonies, indicating that environmental conditions for their growth were naturally met. The corals cultivated on these racks are intended to be part of future transplantation efforts onto the SERs in Tenerife.
The aim of the mission, carried out with the invaluable assistance of Dr. Francisco Otero from Universidad de Las Palmas de Gran Canaria – ECOAQUA, along with his team of researchers, was to perform an initial photogrammetric scan of the transplanted colonies. These first models will serve as a baseline for future scans, allowing for highly precise and multiparametric measurement of colony growth over time. These measurements are crucial for better understanding which species are most suitable for farming programs designed to support transplantation initiatives.
During the dives, photogrammetric scans were conducted on three different culture racks. In addition, the scanning of a broader area was also performed in order to evaluate the method’s efficacy in estimating colony density on a larger spatial scale. The data collected during this mission will undergo detailed processing, and a follow-up scan is planned in several months. By aligning and comparing the two models, researchers aim to achieve highly accurate three-dimensional growth measurements, thereby advancing our understanding of coral cultivation and transplantation success rates.
