Inter-annual changes in fish communities of a tropical bay in southeastern Brazil: What can be inferred from anthropogenic activities?

•We assessed inter-decadal changes in fish assemblages of a tropical bay, which experienced a heavily industrialized process.•Changes in fish assemblages occurred between the two first (1987-88; 1993-95) and the two latter (1998-01; 2012-13) periods.•These changes coincided with metal pollution (mainly, Zn and Cd) and with the enlargement of a local Port•The inner bay zone was the most affected area whereas the outer bay remained relative stable over time.•High depth in the outer bay seems to act as a buffer stabilizing temporal changes in the outer bay zone.

We assessed inter-annual changes in fish assemblages of a tropical bay which experienced a heavily industrialized process in the last decades. A highly significant difference in community structure among the bay zones, and a decrease in fish richness and abundance over time were found. Changes in fish richness and abundance between the two first (1987-1988 and 1993-1995) and the two latter time periods (1998-2001 and 2012-2013) were sharpest in the inner bay zone, the most impacted bay area, and in the middle zone, whereas the outer zone remained comparatively stable over time. These changes coincided with increased metal pollution (mainly, Zn and Cd) in the bay and with the enlargement of the Sepetiba Port. Spatial changes in the fish community structure among the bay zones were related to differences in salinity, transparency and depth with this latter variable acting as a buffer stabilizing temporal community changes.