On the significance of Antarctic jellyfish as food for Adélie penguins, as revealed by video loggers
Résumé
Concern of pelagic gelatinous organisms taking
over perturbed marine ecosystems has led to a recent
increase in research into this group. However, the significance
of this group as prey remains challenging to assess,
and hence, gelatinous consumers are often depicted incorrectly
as dead ends of pelagic food webs. In the Southern
Ocean, where a shift in trophic webs may favour gelatinous
animals, we video-monitored prey intake of a key predator.
Twenty-eight chick-rearing Adélie penguins Pygoscelis
adeliae from Dumont d’Urville station (66°40′S,
140°01′E) were instrumented with miniaturized video
loggers in 2014–2015. Among other items (krill, fish),
101 gelatinous organisms (n = 79 jellyfish, 6 salps and 16
unidentified) were observed on 13 of 21 exploitable video footages (total: 59 h). Importantly, 65.3 % of gelatinous
organisms were attacked, but among them salps were not
attacked. Attacks on jellyfish were significantly associated
with the visible presence of the jellyfish’s gonad. Jellyfish
were encountered at an average depth of 26.2 ± 10.4 m,
significantly shallower than krill. Attacks occurred mostly
during bottom, but also descent or ascent dive phases. Concomitant
GPS location for four birds revealed that attacks
on jellyfish occurred above the shelf, 35 km north from the
colony, where sea ice concentration reached 88 %. These
results indicate that Adélie penguins occasionally feed
on jellyfish, even though other prey types are also available.
Refining our perception of scyphozoans’ niche may
thus help anticipate the functional response of the food
webs to the extensive changes witnessed in the Antarctic
environment.