Three Decades of Change in Potentially Toxic Elements in Brown Algae in the Northeast Atlantic Ocean

Marine pollution from potentially
toxic elements (PTEs)
threatens
coastal ecosystems, making long-term assessments essential. This study
analyzes trends in Al, Cr, Fe, Ni, Cu, Zn, As, Cd, and Hg using 446
samples of Fucus ceranoides, F. spiralis, and F. vesiculosus collected between 1990 and
2021 at 173 coastal sites in NW Spain. A consistent resampling approach
revealed significant declines in most anthropogenic PTEs, including
Cu (−84.7%), Cr (−84.6%), Hg (−49.6%), and Cd
(−36.7%) over time. In contrast, arsenic increased by 36.1%,
but the underlying causes remain unclear, with potential factors including
changes in sediment inputs, bioavailability, or emerging sources such
as groundwater discharges. Higher PTE levels were detected in inner
estuarine areas, but no consistent latitudinal patterns emerged. Overall,
the results suggest effective mitigation of coastal pollution, with
reduced bioavailable PTEs entering the food web via Fucus spp. However, rising As levels and complex contamination dynamics
underscore the need for continued monitoring. This study offers the
most comprehensive standardized assessment of long-term PTE trends
in brown algae to date, providing valuable insights for environmental
policy and coastal management.