Abstract
Glacio-marine fjords occur widely at high latitudes and have been extensively studied in the Arctic, where heavy meltwater inputs and sedimentation yield low benthic faunal abundance and biodiversity in inner-middle fjords. Fjord benthic ecosystems remain poorly studied in the subpolar Antarctic, including those in extensive fjords along the West Antarctic Peninsula (WAP). Here we test ecosystem predictions from Arctic fjords on three subpolar, glacio-marine fjords along the WAP. With seafloor photographic surveys we evaluate benthic megafaunal abundance, community structure, and species diversity, as well as the abundance of demersal nekton and macroalgal detritus, in soft-sediment basins of Andvord, Flandres and Barilari Bays at depths of 436–725 m. We then contrast these fjord sites with three open shelf stations of similar depths. Contrary to Arctic predictions, WAP fjord basins exhibited 3 to 38-fold greater benthic megafaunal abundance than the open shelf, and local species diversity and trophic complexity remained high from outer to inner fjord basins. Furthermore, WAP fjords contained distinct species composition, substantially contributing to beta and gamma diversity at 400–700 m depths along the WAP. The abundance of demersal nekton and macroalgal detritus was also substantially higher in WAP fjords compared to the open shelf. We conclude that WAP fjords are important hotspots of benthic abundance and biodiversity as a consequence of weak meltwater influences, low sedimentation disturbance, and high, varied food inputs. We postulate that WAP fjords differ markedly from their Arctic counterparts because they are in earlier stages of climate warming, and that rapid warming along the WAP will increase meltwater and sediment inputs, deleteriously impacting these biodiversity hotspots. Because WAP fjords also provide important habitat and foraging areas for Antarctic krill and baleen whales, there is an urgent need to develop better understanding of the structure, dynamics and climate-sensitivity of WAP subpolar fjord ecosystems.
Highlights
Fjords are deep estuaries carved by glaciers and typically contain one or more sediment-floored basins separated by sills [1], [2]
In contrast to expectations from Arctic fjord models [4], [5], [10], [13], soft-sediment epibenthic megafaunal communities in the subpolar fjords along the West Antarctic Peninsula (WAP) were characterized by very high abundance relative to the adjacent open shelf at similar depths (,400–700 m)
The WAP fjord mean megafaunal abundances (9.5–43.2 m22) generally exceeded those at similar depths measured with similar image resolution around Antarctica in the Bellingshausen, Weddell, and Ross Seas, except at the mouth of Potter Cove, another Antarctic fjord [42], [43], [44], [45], [46] (Table 4)
Summary
Fjords are deep estuaries carved by glaciers and typically contain one or more sediment-floored basins separated by sills [1], [2]. If the Arctic models apply, we expect the following hypotheses concerning benthic ecosystem structure to apply in subpolar WAP fjords: (1) Benthic communities in the inner-middle basins of WAP subpolar fjords (i.e., within ,5–10 km of tidewater glaciers) are characterized by low (a) faunal abundance, (b) species richness, (c) species diversity, and (d) trophic complexity, as well as (e) dominance by small-bodied mobile deposit feeders, compared to similar depths on the open WAP shelf.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
