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A description of chloride cell and kidney tubule alterations in the flatfish Solea senegalensis exposed to moderately contaminated sediments from the Sado estuary (Portugal)
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Advisor(s)
Abstract(s)
The effects of sediment-bound contaminants on kidney and gill chloride cells were surveyed in juvenile Solea
senegalensis exposed to fresh sediments collected from three distinct sites of the Sado Estuary (Portugal) in a
28-day laboratorial assay. Sediments were analyzed for metallic contaminants, polycyclic aromatic
hydrocarbons and organochlorines as well as for total organic matter, redox potential and fine fraction.
The potential for causing adverse biological effects of each surveyed sediment was assessed by comparison of
contaminant levels to available guidelines for coastal sediments, namely the Threshold Effects Level (TEL)
and the Probable Effects Level (PEL). The Sediment Quality Guideline Quotient indices (SQGQ) were
calculated to compare the overall contamination levels of the three stations. A qualitative approach was
employed to analyze the histo/cytopathological traits in gill chloride cells and body kidney of fish exposed to
each tested sediment for 0, 14 and 28 days. The results showed that sediment contamination can be
considered low to moderate and that the least contaminated sediment (from a reference site, with the lowest
SQGQ) caused lesser changes in the surveyed organs. However, the most contaminated sediment (by both
metallic and organic xenobiotics, with highest SQGQ) was neither responsible for the highest mortality nor
for the most pronounced lesions. Exposure to the sediment presenting an intermediate SQGQ, essentially
contaminated by organic compounds, caused the highest mortality (48%) and the most severe damage to
kidneys, up to full renal necrosis. Chloride cell alterations were similar in fish exposed to the two most
contaminated sediments and consisted of a pronounced cellular hypertrophy, likely involving fluid retention
and loss of mitochondria. It can be concluded that sediment contamination considered to be low or moderate
may be responsible for severe injury to cells and parenchyma involved in the maintenance of osmotic
balance, contributing for the high mortality levels observed. The results suggest that sediment-bound
organic contaminants such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated
biphenyls) may be very toxic to the analyzed organs, especially the kidney, even when present in lowrisk concentrations.
Description
Keywords
Senegalese sole Chloride cell hypertrophy Nephrotoxicity Histopathology Sediment contaminants Estuarine environment