First assessments on marine geomorphology and bio-colonization through the study and survey of the wreck of the Hospital Ship “Po” along the Albanian coasts (Vlora Bay)

Abstract

Vlora bay (Albania) hosts the 134.98 m long wreck of the Hospital Ship “Po” (sunk in 1941), located within the Karaburun-Sazan Marine Protected Area. This study investigates the interactions between this anthropogenic structure and the surrounding marine environment through a multidisciplinary observational approach. Resting at 33–37 m depth on a gently inclined shelf, the wreck provides a hard substrate that supports benthic colonization. High-resolution geophysical surveys (MBES, SSS) and Structure-from-Motion (SfM) photogrammetry, integrated with biological and sedimentological censuses, were used to develop two preliminary quantitative metrics: the Geometric-Geomorphological Wreck Effect Index (IGEOM) and the Ecological Hotspot Value Index (IECO). Geomorphological observations reveal a 2.1 m deep upstream scour hollow and a 45 m downstream depositional tail. Sedimentological data indicate a local granulometric gradient, with fine silt-clay fractions (< 63 μm) found near the wreck, contrasting with a medium sand baseline (350 μm). These features are consistent with deposition under regional sediment-supply conditions influenced by the Vjosa River (from NW), though direct sediment-source attribution requires further investigation. Ecologically, the site exhibits high benthic diversity (H' = 2.91) and structural complexity. Findings include the presence of the non-indigenous Pterois miles , evidence of Ommastrephidae spawning and a sighting of the critically endangered Monachus monachus , generating the hypothesis that the wreck may occasionally function as a local feeding area. The proposed indices (IGEOM and IECO) offer preliminary, site-specific descriptors summarizing observational data, with potential applicability to future monitoring and Marine Spatial Planning (MSP) frameworks, pending multi-site validation.