Heavy metal pollution in sediments and its Biotransference in crabs from mangrove and coastal zones of Pakistan

This study endeavored to assess distributions, contamination, and sources of heavy metals (HMs) in sediments and benthic crabs in mangrove and coastal zones of Pakistan. The presence of HMs (Cu, Zn, Cr, Pb, Co, Ni, and Cd) was significant (p < 0.05) in sediments among the study sites.According to sediment quality guidelines, all sites were categorized as medium-low priority with a 25 % probability of having adverse biological effects on benthic fauna. Seven benthic crab species were analyzed to investigate HM bioaccumulation, which presented habitat-specificity and species-specific variations in HM profiles. Each species exhibited different behavior as expressed by the HM concentration indicator (HMCI). The overall HM burden in crabs was considered by the metal pollution index (MPI), and all crabs showed an MPI value > 1.0. Fiddler crabs (Austruca sindensis and A. iranica) exhibited the highest MPI values indicating their ability to cope with various HMs. Most of the metals (Cu, Zn, Co, Pb, and Cd) showed a high sediment-biota accumulation factor (SBAF >1.0) that signified the prevalence of HMs in crabs as compared with their surroundings. Principal component analysis (PCA) discriminated between HMs in sediments and crabs and suggested that long-standing anthropogenic events aggregated HMs in coastal sediments, potentially incorporated into the benthic food chain. The crab species was revealed as an efficient accumulator of HMs and acted as a potential candidate for HMCI in the contaminated environment.