Structure from Motion Photogrammetry as an Effective Nondestructive Technique to Monitor Morphological Plasticity in Benthic Organisms: The Case Study of Sarcotragus foetidus Schmidt, 1862 (Porifera, Demospongiae) in the Portofino MPA

Porifera are essential components of marine ecosystems, providing valuable ecological functions. Traditional approaches to estimating sponge growth and biomass are destructive and often not suitable for certain morphologies. The implementation of new innovative techniques and nondestructive methodologies have allowed for a more sustainable approach. In this study, a population of Sarcotragus foetidus Schmidt, 1982 (Demospongiae, Dictyoceratida, Irciinidae), thriving inside the Portofino Marine Protected Area, was monitored using Structure from Motion photogrammetry over a period of 6 years, from September 2017 to October 2023. Of the 20 initial individuals, only 12 were still in place during the last monitoring, indicating 40% mortality. Through photogrammetry, the overall volume change and biomass production were estimated to be 9.24 +/- 5.47% year(-1) and 29.52 +/- 27.93 g DW year(-1), respectively, indicating a general decreasing trend between 2021 and 2023. Signs of necrosis were observed in some individuals, potentially related to the high temperature occurring during summer 2022 and 2023. Considering the current climate crisis, long-term monitoring efforts must be made to better understand the dynamics of this species, and photogrammetry has the potential to be a versatile monitoring tool that will contribute to the standardization of methodologies for sponge growth studies.