Evaluation of the response of phytoplankton communities to heavy metal stresses using multi-statistical approaches, Alexandria coast, Egypt

Abstract

This is the first study to investigate the antioxidant response of the phytoplankton community to heavy metal stress in the open sea. The levels of Cu, Zn, Cd, Mn, Pb, and Fe were determined in the phytoplankton community and water in Abu Talat (AT), and El Dekhella Harbour (DH), Alexandria coast during spring 2018 and autumn 2019. Furthermore, the changes in phytoplankton abundance, the bioconcentration factor (BCF), the metal pollution index (MPI), and the pollution load index (PLI) were used to assess pollution status. The phytoplankton density in the DH stations was 17–42 folds higher than in the AT. The order of BCF during spring was Fe > Zn > Pb > Cu > Mn > Cd. However, Fe > Zn > Mn > Cu > Pb > Cd was found in both areas during the autumn. The BCF, MPI, and PLI of the phytoplankton community revealed that DH is more polluted than AT. The phenol, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and total antioxidant activity of the phytoplankton communities achieved higher values in DH than in AT stations, in response to heavy metal stresses. Principal component analysis was performed to follow pollution sources, suggesting that station 3 in both seasons was a hot spot because of stagnant water. A correlation matrix indicated that phenol and DPPH interacted positively in both locations during the two seasons. Analysis of variances with replicate tests on heavy metals in phytoplankton revealed significant seasonal differences across the two areas at a significance level < 0.05.