G

orgonians are one of the main benthic habitat-forming species in the Mediterranean Sea. Their three-dimensional structure increases substrate complexity, providing shelter and support to other species. They form gorgonian forests characterized by hosting a high specific and functional diversity. Over the past decades, mass mortality events of gorgonians have been reported, mostly attributed to rising seawater temperatures. To understand gorgonian distribution, environmental variables such as temperature or current velocity have been monitored. However, food availability, a key variable for their development, has never been measured.

The main objective of this thesis is to model the food availability for gorgonians at both local and regional scales. The local-scale modelling will focus on gorgonian populations restored through the European project OCEAN CITIZEN, under which this thesis is framed. Regional-scale modelling will cover the entire Catalan coastline, at depths ranging from 15 to 45 meters. The methodology for both scales will be the same. First, gorgonian food availability will be monitored. Then, using the collected data, this variable will be modelled in the respective area.

To monitor gorgonian food availability, a benthic trap will be designed to capture particulate organic matter ranging from a few microns to hundreds of microns, which constitutes the food for gorgonians in the study area. Other environmental variables, such as temperature, turbidity, and current velocity and direction, will also be monitored. Finally, using all the collected data, gorgonian food availability will be modelled using machine learning techniques.

The result of the regional-scale modelling will be a map of gorgonian food availability in the study area. This map will integrate data from the monitored environmental variables and gorgonian presence data obtained from databases and literature. This combination will enable: i) Assessing the importance of trophic conditions in gorgonian distribution. ii) Defining the trophic conditions necessary for gorgonian survival. iii) Identifying areas in the study region suitable for initiating gorgonian forest restoration projects, considering the modelled environmental and trophic conditions.