Environmental conditions controlling cold-water coral growth in the southern Alboran Sea since the last deglaciation

Abstract

Cold-water coral (CWC) mounds are commonly found in the Alboran Sea (westernmost Mediterranean), specifically in the so-called East and West Melilla mound provinces. This study presents a multi-proxy analysis on the environmental changes that occurred in west Melilla since the last deglaciation (∼14 kyr), based on the on-mound core MD13–3451 (∼370 m). The analyses performed include geochemical measurements of foraminiferal coatings (U/Mn) and skeletal calcite (stable oxygen and carbon isotopes, Mg/Ca-derived deep-water temperatures). Furthermore, the seawater δ¹⁸O (δ¹⁸O_sw) and the ice-volume-corrected seawater δ¹⁸O (δ¹⁸O_sw-ivc) have been estimated via paired analyses of Mg/Ca and δ¹⁸O_carbonate. Our findings suggest that i) pulses of relatively warm deep-water during the last mound flourishing stage, here-referred to as ‘Cold Water Coral - Growth Phase 1’ (CWC-GP1; ∼11–9 kyr), triggered a shift in coral species dominance in the west Melilla province, and ii) a rapid freshening of the waters occurred during CWC-GP1, indicating significant hydrographical changes. To further interpret these results, we combined them with comparable records from neighboring sites. We find that CWC-GP1 is closely coupled with a reorganization of the Alboran Sea water column. More precisely, we discuss the potential emergence of a western Mediterranean intermediate sourced water, which partly replaced intermediate waters from eastern Mediterranean sources and contributed to the enhanced hydrodynamics of the region. We further propose that the interplay between strong near-bottom currents and increased upwelling conditions may have played a crucial role in controlling CWC growth dynamics.