Seasonal Dietary Shifts of the Gammarid Amphipod Gondogeneia antarctica in a Rapidly Warming Fjord of the West Antarctic Peninsula

The amphipod Gondogeneia antarctica is among the most abundant benthic organisms, and a key food web species along the rapidly warming West Antarctic Peninsula (WAP). However, little is known about its trophic strategy for dealing with the extreme seasonality of Antarctic marine primary production. This study, using trophic markers, for the first time investigated seasonal dietary shifts of G. antarctica in a WAP fjord. We analyzed δ13C and δ15N in G. antarctica and its potential food sources. The isotopic signatures revealed a substantial contribution of red algae to the amphipod diet and also indicated a significant contribution of benthic diatoms. The isotope results were further supported by fatty acid (FA) analysis, which showed high similarities in FA composition (64% spring–summer, 58% fall–winter) between G. antarctica and the red algal species. G. antarctica δ13C showed a small shift seasonally (−18.9 to −21.4‰), suggesting that the main diets do not change much year-round. However, the relatively high δ15N values as for primary consumers indicated additional dietary sources such as animal parts. Interestingly, G. antarctica and its potential food sources were significantly enriched with δ15N during the fall–winter season, presumably through a degradation process, suggesting that G. antarctica consumes a substantial portion of its diets in the form of detritus. Overall, the results revealed that G. antarctica relies primarily on food sources derived from benthic primary producers throughout much of the year. Thus, G. antarctica is unlikely very affected by seasonal Antarctic primary production, and this strategy seems to have allowed them to adapt to shallow Antarctic nearshore waters.

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The seasonal cycle of ocean-atmosphere CO2flux in Ryder Bay, west Antarctic Peninsula

Geophysical Research Letters ◽

10.1002/2015gl063796 ◽

2015 ◽

Vol 42 (8) ◽

pp. 2934-2942 ◽

Cited By ~ 31

Author(s):

Oliver J. Legge ◽

Dorothee C. E. Bakker ◽

Martin T. Johnson ◽

Michael P. Meredith ◽

Hugh J. Venables ◽

...

Keyword(s):

Antarctic Peninsula ◽

Seasonal Cycle ◽

West Antarctic ◽

Ocean Atmosphere ◽

West Antarctic Peninsula

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Megafaunal Communities in Rapidly Warming Fjords along the West Antarctic Peninsula: Hotspots of Abundance and Beta Diversity

PLoS ONE ◽

10.1371/journal.pone.0077917 ◽

2013 ◽

Vol 8 (12) ◽

pp. e77917 ◽

Cited By ~ 62

Author(s):

Laura J. Grange ◽

Craig R. Smith

Keyword(s):

Antarctic Peninsula ◽

Beta Diversity ◽

The West ◽

West Antarctic ◽

West Antarctic Peninsula

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The role of fish in the Antarctic marine food web: differences between inshore and offshore waters in the southern Scotia Arc and west Antarctic Peninsula

Antarctic Science ◽

10.1017/s0954102002000111 ◽

2002 ◽

Vol 14 (4) ◽

pp. 293-309 ◽

Cited By ~ 90

Author(s):

ESTEBAN BARRERA-ORO

Keyword(s):

Food Web ◽

Antarctic Peninsula ◽

Demersal Fish ◽

Pelagic Fish ◽

West Antarctic ◽

Antarctic Marine ◽

Scotia Arc ◽

West Antarctic Peninsula ◽

The Antarctic

The role of fish in the Antarctic food web in inshore and offshore waters is analysed, taking as an example the coastal marine communities of the southern Scotia Arc (South Orkney Islands and South Shetland Islands) and the west Antarctic Peninsula. Inshore, the ecological role of demersal fish is more important than that of krill. There, demersal fish are major consumers of benthos and also feed on zooplankton (mainly krill in summer). They are links between lower and upper levels of the food web and are common prey of other fish, birds and seals. Offshore, demersal fish depend less on benthos and feed more on zooplankton (mainly krill) and nekton, and are less accessible as prey of birds and seals. There, pelagic fish (especially lantern fish) are more abundant than inshore and play an important role in the energy flow from macrozooplankton to higher trophic levels (seabirds and seals). Through the higher fish predators, energy is transferred to land in the form of fish remains, pellets (birds), regurgitation and faeces (birds and seals). However, in the general context of the Antarctic marine ecosystem, krill (Euphausia superba) plays the central role in the food web because it is the main food source in terms of biomass for most of the high level predators from demersal fish up to whales. This has no obvious equivalent in other marine ecosystems. In Antarctic offshore coastal and oceanic waters the greatest proportion of energy from the ecosystem is transferred to land directly through krill consumers, such as flying birds, penguins, and seals. Beside krill, the populations of fish in the Antarctic Ocean are the second most important element for higher predators, in particular the energy-rich pelagic Myctophidae in open waters and the pelagic Antarctic silver fish (Pleuragramma antarcticum) in the high Antarctic zone. Although the occurrence of these pelagic fish inshore has been poorly documented, their abundance in neritic waters could be higher than previously believed.

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Changes in the upper ocean mixed layer and phytoplankton productivity along the West Antarctic Peninsula

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2017.0173 ◽

2018 ◽

Vol 376 (2122) ◽

pp. 20170173 ◽

Cited By ~ 20

Author(s):

Oscar Schofield ◽

Michael Brown ◽

Josh Kohut ◽

Schuyler Nardelli ◽

Grace Saba ◽

...

Keyword(s):

Sea Ice ◽

Antarctic Peninsula ◽

Mixed Layer ◽

Carbon Fixation ◽

Upper Ocean ◽

The West ◽

Phytoplankton Productivity ◽

West Antarctic ◽

West Antarctic Peninsula

The West Antarctic Peninsula (WAP) has experienced significant change over the last 50 years. Using a 24 year spatial time series collected by the Palmer Long Term Ecological Research programme, we assessed long-term patterns in the sea ice, upper mixed layer depth (MLD) and phytoplankton productivity. The number of sea ice days steadily declined from the 1980s until a recent reversal that began in 2008. Results show regional differences between the northern and southern regions sampled during regional ship surveys conducted each austral summer. In the southern WAP, upper ocean MLD has shallowed by a factor of 2. Associated with the shallower mixed layer is enhanced phytoplankton carbon fixation. In the north, significant interannual variability resulted in the mixed layer showing no trended change over time and there was no significant increase in the phytoplankton productivity. Associated with the recent increases in sea ice there has been an increase in the photosynthetic efficiency (chlorophyll a -normalized carbon fixation) in the northern and southern regions of the WAP. We hypothesize the increase in sea ice results in increased micronutrient delivery to the continental shelf which in turn leads to enhanced photosynthetic performance. This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

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