Environmental degradation and recovery after termination of whaling in sub-Antarctic fjord, South Georgia

Polar ecosystems are considered very fragile, however, due to the short observation record it is hard to assess the recovery processes of the coastal and fjord environments after a major disturbance. Here, we provide a unique case study from South Georgia (sub-Antarctic), an area seriously affected by the whaling industry. The study focuses on King Edward Cove, serving as a sheltered harbor for the former whaling station at Grytviken, as well as other parts of Cumberland Bay considered to represent generally pristine areas. We studied 210Pb dated sediment cores, which were subjected to analysis of sediment geochemical composition, concentrations of anthropogenic organic markers and biomarkers, foraminiferal assemblage changes, as well as sedimentary ancient DNA. Three distinct phases have been identified. The oldest one, predating ca. 1970, recorded the whaling period, and was characterized by anoxic conditions, high organic carbon content, contamination with heavy metals, organic markers, distinct DNA signature and lack of foraminiferal microfossils. It took only a few years to establish a new ecosystem with a fully developed foraminiferal assemblage and decreased contamination characteristic for the middle phase (ca. 1970–2000). Ancient DNA suggests macro-zoobenthic recovery being delayed by a several years in comparison to benthic foraminifera. In the youngest period, around Cumberland Bay, the increase of iceberg rafted debris from rapidly retreating tidewater glaciers was noted, while the improved oxygen availability in bottom waters in King Edward Cove can be likely ascribed to frequent water mixing due to increasing traffic of large cruise vessels. The recorded pace of ecosystem recovery from major anthropogenic disturbance appears similar to that observed in the temperate fjords from the Northern Hemisphere, however, the effects of new anthropogenic threat and the ongoing climate change are already resulting in the new ecosystem disturbance. [Display omitted] •Multiproxy record of whaling industry impact on fjord environment in South Georgia•King Edward Cove next to Grytviken was subjected to major anthropogenic disturbance.•The impact is well recorded in pollutants and ecosystem changes (microfossils, DNA).•End of whaling in mid-1960s resulted in relatively rapid ecosystem recovery.•Increasing vessel traffic in early 2000s caused a measurable ecosystem disturbance.