Life in the polar oceans: the role of sea ice in the biology and ecology of marine species

• Main Author: Schaafsma, Fokje
• Format: Thesis
• Language: unknown
• Published: Wageningen University 2018
• Subjects: Antarc*; Antarctic; Antarctic Krill; Boreogadus saida; Euphausia superba; polar cod; Sea ice; Southern Ocean; Zooplankton; ice covered waters
• Online Access: https://epic.awi.de/id/eprint/52365/; https://epic.awi.de/id/eprint/52365/1/Schaafsma_PhD_thesis.pdf; https://hdl.handle.net/10013/epic.9ef05e00-b7b7-412f-8305-7af672967422

A unique feature of the polar oceans is formed by sea ice. The annual cycle of freezing and melting causes tremendous seasonal variation in ice-cover. Other factors, such as wind and ocean currents, cause a continuous reshaping of the sea ice resulting in assemblages of ice of different sizes and structures. This highly dynamic feature forms a habitat for life in the polar ocean. Sea ice and its seasonal changes influence the physical features of the environment, such as light availability and water column properties, resulting in fluctuating rates of primary production both within the sea ice and in the water column. This has a large impact on the food availability for higher trophic levels, which also use the sea ice for e.g. reproduction and as a shelter for predation. Zooplankton and nekton species living underneath the sea-ice of the polar oceans have in different ways adapted to the fluctuation in food availability and their seasonally changing habitat. Life cycle events, such as reproduction, are often timed to coincide with peaks in primary production. Furthermore, several species developed different overwintering strategies to cope with the food scarcity during this season, such as relying on reserves, lowering metabolism or shifting diet. Antarctic krill (Euphausia superba) and polar cod (Boreogadus saida) are considered to be key species of the under-ice surface water in the Southern and Arctic Oceans, respectively. Information on how organisms utilize the sea-ice habitat remains incomplete. The understanding of sea-ice ecology has been hampered by the difficulty to collect sufficient samples that allow the identification of large-scale spatial trends. The Surface and Under Ice Trawl (SUIT) was developed to overcome this limitation and has already been used to gain insight in the differences in zooplankton distribution and community structure between open and ice-covered waters in the Southern Ocean. Further knowledge on how polar species utilize the sea ice and how the sea ice affects their ...