Weddell seals.
Photo: Michael Hambrey, Swiss-
Educ (www.swisseduc.ch) and
Glaciers online (www.glaciers-
online.net)
increased predation rates from killer whales (Orcas); Seals
increased risks from disease and parasites; Many polar seal species depend on sea ice as a birthing,
greater potential for exposure to increased pollution moulting and resting platform, and some seals also do
loads due to long range transport of pollutants such as much of their foraging on ice-associated prey
64,68–72
.
PCBs and mercury; and, Ross seals, crabeater seals and leopard seals in the
impacts via increased human traffic and development Antarctic and harp seals, hooded seals, ribbon seals,
in previously inaccessible, ice-covered areas. and spotted seals in the Arctic all breed in drifting
pack-ice. Arctic bearded seals breed in areas of shal-
Predicted changes in sea ice in combination with oth- low water along coast-lines on small pieces of ice that
er climate change impacts on Arctic ecosystems, and break away from the annually-formed land-fast ice in
resultant changes in human activity patterns, will un- the late spring. Ringed seals in the Arctic and Weddell
doubtedly affect the abundance and distribution pat- seals in the Antarctic breed on land-fast ice. These two
terns of species within polar marine mammal com- species occupy extensive areas of ice that form along
munities. The full-time, ice-associated residents of the coastlines because they are able to maintain breathing
Arctic and Antarctic are likely going to be negatively im- holes, even in sea ice that can reach 1 to 2 metres in
pacted, while the seasonal and summer migrants will thickness (see box on ringed seals). All of the ice-as-
likely increase in abundance and extend their ranges in sociated seals require temporally predictable, extensive
a warmer Arctic that is ice-free in summer. areas of sea ice. Current projections suggested for the
CHAPTER 5 ICE IN THE SEA 83