Ecological risks of trace elements in sediments and Thalassia testudinum from Cartagena Bay

This study assesses the ecological risks from trace elements in sediments and Thalassia testudinum in two contrasting areas of the Colombian Caribbean: Cartagena Bay (CTG Bay), an industrialized zone, and the Rosario and San Bernardo Corals National Natural Park (RSBC-NNP), a reference site. A total of 47 trace elements were quantified using inductively coupled plasma mass spectrometry (ICP-MS). Sediment contamination was quantified through pollution indices, and bioconcentration factors (BCFs) were calculated to evaluate trace element accumulation in T. testudinum. Concentrations of most trace elements in sediments from CTG Bay exceeded those found in RSBC-NNP, with the greatest fold differences observed for Cd (16.7), Ni (3.9) and Cr (3.8). At RSBC-NNP, the highest levels were found for Sr (4.333±0.412 mg/kg), B (0.109±0.032 mg/kg) and Zn (0.040±0.006 mg/kg), whereas CTG Bay recorded the maximum values for the same elements, Sr (0.988±0.512 mg/kg), B (0.178±0.05 mg/kg), and Zn (0.081±0.016 mg/kg). T. testudinum exhibited bioaccumulation capacity for most trace elements. BCFs exceeded 1 for 41 elements analyzed in CTG Bay, with Ge, Hf, Ba, Th and Ta leading the list, compared to 15 in RSBC-NNP, headed by Mo. The Pollution factors, Geoaccumulation indexes, Enrichment factors. and the Nemerow Pollution Index confirmed the degraded state of CTG Bay sediments. These findings validate T. testudinum as a bioindicator of marine quality, and emphasize the need for continuous monitoring and mitigation strategies to protect this key species and its ecosystem.