Presenter: Emily Zembricki (Stockton University)

Description:
Humpback whales have made an astounding recovery since being hunted to near-extinction in the mid-1900s. Today, there are nearly 80,000 humpback whales worldwide with an estimated 10% annual rate of increase since 1982. As humpback whale numbers continue to rise, researchers are concerned about how their return will impact marine communities already experiencing structural shifts due to climate change. Previous studies have established that humpback whales maintain marine ecosystems using a top-down approach, however, there has been a lack of research examining how the foraging pressures exerted by these animals impact already changing community structures. This study explored how increasing humpback whale presence has impacted shifting krill dominance in the West Antarctic Peninsula (WAP). Time series of humpback whale sightings as well as Euphausia superba and Thysanoessa spp. densities were created using data from the Palmer Station LTER website. The time series were overlaid and compared to corresponding sea ice coverage data provided by the National Snow and Ice Data Center. In 1993, the dominant krill species in the WAP shifted from E. superba to Thysanoessa spp. This shift correlated with a period of major sea ice loss that lasted until 1998. Despite minor sea ice recovery taking place the following year, Thysanoessa spp. remained the dominant species in the WAP. Because humpback whales feed indiscriminately, increasing humpback presence in the WAP likely reinforced the ongoing changes in the Antarctic krill community structure. Continual reinforcement of these changes could lead to permanent alterations in the local and regional food webs of the WAP and the greater Antarctic region.