Community structure of amphipods from sediment traps in the eastern Fram Strait - interactions with environmental parameters in a changing Arctic. Eberhard Karls University Tübingen,

Eva-Maria.Noethig [ at ]


Summary: During the last twenty years, the Arctic is under rapid environmental change also affecting the marine fauna. In this context, samples from sediment traps (200m water depth) of the Long-Term Ecological Research (LTER) observatory HAUSGARTEN in the northeastern Fram Strait (79°N, 4°E) have been used to obtain year-round abundances and inter-annual trends of zooplankton swimmers in time-series from the year 2000 until 2014. Those time-series sediment trap samples offer a unique insight into Arctic zooplankton population dynamics and changes therein. Dominating swimmer biomass, Arctic pelagic amphipods represent a valuable data source to reveal environmental changes. Amphipods are key species in the Arctic pelagic system linking primary consumers such as copepods with higher trophic levels like marine mammals and sea birds. This investigation is mainly based on amphipod sampling data of three consecutive years (2011-2014) obtained at two locations within the LTER HAUSGARTEN. In total, seven amphipod species of four taxonomic families could be observed (Hyperiidae, Lanceolidae, Eusiridae, and Gammaridae). Amphipods of the genus Themisto could be shown to dominate the epipelagic amphipod community by >97%. The latest abundance development of the native Themisto species – the boreal T. abyssorum and the Arctic T. libellula – and the intruding T. compressa is described and related to environmental data such as sea ice extend, North Atlantic Oscillation index, marine current velocity, current direction, ocean temperature, and water salinity. Between 2000 and 2014, increasing amphipod abundances could be observed, presumably due to changed trophic interactions and the warming system. Abundances analyzed at the central HAUSGARTEN site were considerably larger than at the northern location, which was likely provoked by hydrographic features and differences in sea ice cover. Further, range shifts in amphipods are evident: abundances of the North Atlantic species T. compressa continued to increase compared to mid-2000s, which may be attributed to warmer Atlantic water inflow causing slightly higher ocean temperatures in eastern Fram Strait. This trend is also supported by elevated abundances of the temperate species Lanceola clausi observed in the HAUSGARTEN sediment traps time-series. In addition, hardly any immature individual of the Arctic T. libellula was recorded in the sampling period 2013/14, even though juveniles of this species were common previously. These findings suggest environmental shifts taking place in the seasonally ice-covered eastern Fram Strait. The three dominating pelagic Themisto-species showed significant seasonal variability, with high abundances in summer and lower quantities in winter. Overall, Themisto abyssorum dominated the amphipod community by >50%. However, in 2012/13, T. abyssorum and T. libellula were present in nearly equal proportions (~40%) at both HAUSGARTEN sites. That sampling period was characterized by ambivalent ocean temperatures with a first warm winter and a pronounced temperature drop after which cold water prevailed all summer 2013 long. Whereas the two native species were present throughout the year, T. compressa was absent over long periods in winter (November to February). T. libellula featured erratic occurrences in late summers between July and September. A seasonal pattern was also evident in the gender analysis, which revealed similar patterns for the native species with elevated male proportions in winter only (up to 32%), which was reversed for T. compressa (40% in summers). Overall, high male proportions in T. compressa could be observed irrespective of the HAUSGARTEN site. Maturity studies rendered noteworthy proportions of juveniles for T. abyssorum only, which were further seasonally well distributed at the northern HAUSGARTEN site. No juveniles of T. compressa were detected in winters. Hence, this study also strongly highlights the advantages of sediment trap swimmer investigations in pelagic zooplankton studies complementing yet established research approaches. The present master thesis highly supports the use of sediment trap time-series to obtain year-round data sets which on a long-term basis enlarge our knowledge on pelagic processes.

Item Type
Thesis (Master)
Primary Division
Primary Topic
Research Networks
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Eprint ID
Cite as
Schröter, F. (2016): Community structure of amphipods from sediment traps in the eastern Fram Strait - interactions with environmental parameters in a changing Arctic. Eberhard Karls University Tübingen, Master thesis,

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ARK > XXVI > 2

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