229
dence. It could be hypothesized that the observed disparity
is a result of nutrient inputs from human populations which
may offset nutrient-limited productivity, thus increasing the
risk of an algal dominated phase-shift.
10.2.5 Resilience of Canopy Formers to Different
Profiled Marine Heatwaves
Sandra C. Straub
1*
, Thomas Wernberg
1
1
UWA Oceans Institute & School of Biological Sciences,
The University of Western Australia, 39 Fairway, Crawley
6009 WA, Australia
*corresponding author: Sandra.straub@research.uwa.
edu.au
Keywords: Positive temperature anomaly, Extreme climatic event, Kelp forests, Temperature threshold, Ecklonia
radiata
Kelp forests, and the ecosystem services they provide, are
increasingly challenged by ocean warming and climate
extremes such as marine heatwaves. Marine heatwaves are
anomalously warm-water temperatures over a prolonged
period of time, and in recent years a number of marine heatwaves have occurred across the globe with devastating biological and socioeconomic impacts. In 2011, a marine
heatwave off Western Australia had a strong impact on the
main canopy-formers Ecklonia radiata and Scytothalia dorycarpa, which retracted their range southwards and decreased
drastically in abundance in several locations, leading to a
regime shift from a three-dimensional kelp forest to a turfdominated state in several locations. Marine heatwaves can
have different ‘profiles’, varying in intensity, duration and
return frequency, but little is known about the relative importance of these characteristics in assessing their impacts. We
determined how vulnerable the main canopy-former Ecklonia
radiata is to different marine heatwaves by exposing the kelp
to a variety of heatwaves in the laboratory, with varying
duration (2, 4, 6 or 8 weeks), maximum intensity (25 °C and
26.5 °C) and with/without a plateau phase at maximum
intensity. We measured photosynthetic efficiency, growth,
biomass, surface area, mortality and health throughout the
duration of the experiment. The kelp showed clear differences in response to the different profiles, with longer heatwaves having a strong detrimental impact, and varying
maximum intensity showing trends that 1.5°C temperature
difference can have a strong impact over extended periods of
time. We saw a strong significant effect of duration on mortality, health status, surface area and growth rate, and a
delayed effect of temperature exposure on mortality indicating short-term resilience of the kelp. These results will help
to understand how Ecklonia radiata and other kelps can deal
with future heatwaves, how likely survival is under different
scenarios and if recovery of impacted ecosystems is
possible.
10.2.6 Temperature and Food Conditions Affect
Fitness of Aurelia aurita Polyps
Xupeng Chi
1*
, Doerthe Mueller-Navarra
2
, Samuel Hylander
3
,
Ulrich Sommer
1
, Jamileh Javidpour
1
1
Experimental ecology, GEOMAR Helmholtz Centre for
Ocean Research, Duesternbrooker Weg 20, Kiel 24105,
Germany
2
Centre for Marine and Climate Research, Institute for
Hydrobiology and Fisheries Research, University of
Hamburg, Olbers Weg 24, Hamburg D-22767, Germany
3
Centre for Ecology and Evolution in Microbial Model
Systems-EEMiS, Faculty of Health and Life Sciences,
Linnaeus University, Kalmar, Sweden
*corresponding author: xchi@geomar.de
Keywords: Aurelia aurita, Polyp, Tolerance curve, Food
quality, Asexual reproduction
Summer blooms of some scyphomedusae cause high
stress on marine ecosystem structure by competing for fish
ecological niche, or directly predate fish eggs and larvae.
They are known to be dependent to the proliferation of
sessile- overwintered polyps (strobilation). So far temperature was defined as the main abiotic factor driving presence/
absence of some jellyfish outbreaks. However, little is known
about combined effects of biotic and abiotic factors on the
fitness of polyp stage. To investigate the survival, growth and
phase transition ecology of Aurelia aurita polyps, we
designed a factorial experiment manipulating food quality
(Artemia salina and two manipulated Acartia tonsa fed with
different prey), food quantity (20 μg C, 5 μg C and 1.5 μg C
polyp
−1
d
−1
) and temperature (13 °C, 20 °C and 27 °C) representing warming scenarios of the North Sea in the late
autumn, early spring and summer seasons. As expected, temperature was the key factor to determine the phase transition
of polyps. Interestingly, while high food concentration and
better food quality could promote the organisms’ production
in each life cycle mode (buds, ephyrae, podocysts). Besides,
food quality seems to compensate the physiological stress
caused by temperature and food concentration. Based on the
findings in this experiment and previous studies, we put forward the polyp’s temperature tolerance curve, which may
help us to understand that the variation of medusae population regarding the overlay and shifting of different environmental factors’ tolerance curve.
10.2.7 Catch Distribution Shifts in Tropical Tuna
Fisheries
Iratxe Rubio
1,2*
, Elena Ojea
2
1
Basque Centre for Climate Change BC3, Sede Building
1, 1st floor. Scientific Campus of the University of the
Basque Country 48940 Leioa, Spain
2
Future Oceans Lab, University of Vigo, Campus Lagoas
Marcosende, 36310 Vigo, Spain
Appendices
dence. It could be hypothesized that the observed disparity
is a result of nutrient inputs from human populations which
may offset nutrient-limited productivity, thus increasing the
risk of an algal dominated phase-shift.
10.2.5 Resilience of Canopy Formers to Different
Profiled Marine Heatwaves
Sandra C. Straub
1*
, Thomas Wernberg
1
1
UWA Oceans Institute & School of Biological Sciences,
The University of Western Australia, 39 Fairway, Crawley
6009 WA, Australia
*corresponding author: Sandra.straub@research.uwa.
edu.au
Keywords: Positive temperature anomaly, Extreme climatic event, Kelp forests, Temperature threshold, Ecklonia
radiata
Kelp forests, and the ecosystem services they provide, are
increasingly challenged by ocean warming and climate
extremes such as marine heatwaves. Marine heatwaves are
anomalously warm-water temperatures over a prolonged
period of time, and in recent years a number of marine heatwaves have occurred across the globe with devastating biological and socioeconomic impacts. In 2011, a marine
heatwave off Western Australia had a strong impact on the
main canopy-formers Ecklonia radiata and Scytothalia dorycarpa, which retracted their range southwards and decreased
drastically in abundance in several locations, leading to a
regime shift from a three-dimensional kelp forest to a turfdominated state in several locations. Marine heatwaves can
have different ‘profiles’, varying in intensity, duration and
return frequency, but little is known about the relative importance of these characteristics in assessing their impacts. We
determined how vulnerable the main canopy-former Ecklonia
radiata is to different marine heatwaves by exposing the kelp
to a variety of heatwaves in the laboratory, with varying
duration (2, 4, 6 or 8 weeks), maximum intensity (25 °C and
26.5 °C) and with/without a plateau phase at maximum
intensity. We measured photosynthetic efficiency, growth,
biomass, surface area, mortality and health throughout the
duration of the experiment. The kelp showed clear differences in response to the different profiles, with longer heatwaves having a strong detrimental impact, and varying
maximum intensity showing trends that 1.5°C temperature
difference can have a strong impact over extended periods of
time. We saw a strong significant effect of duration on mortality, health status, surface area and growth rate, and a
delayed effect of temperature exposure on mortality indicating short-term resilience of the kelp. These results will help
to understand how Ecklonia radiata and other kelps can deal
with future heatwaves, how likely survival is under different
scenarios and if recovery of impacted ecosystems is
possible.
10.2.6 Temperature and Food Conditions Affect
Fitness of Aurelia aurita Polyps
Xupeng Chi
1*
, Doerthe Mueller-Navarra
2
, Samuel Hylander
3
,
Ulrich Sommer
1
, Jamileh Javidpour
1
1
Experimental ecology, GEOMAR Helmholtz Centre for
Ocean Research, Duesternbrooker Weg 20, Kiel 24105,
Germany
2
Centre for Marine and Climate Research, Institute for
Hydrobiology and Fisheries Research, University of
Hamburg, Olbers Weg 24, Hamburg D-22767, Germany
3
Centre for Ecology and Evolution in Microbial Model
Systems-EEMiS, Faculty of Health and Life Sciences,
Linnaeus University, Kalmar, Sweden
*corresponding author: xchi@geomar.de
Keywords: Aurelia aurita, Polyp, Tolerance curve, Food
quality, Asexual reproduction
Summer blooms of some scyphomedusae cause high
stress on marine ecosystem structure by competing for fish
ecological niche, or directly predate fish eggs and larvae.
They are known to be dependent to the proliferation of
sessile- overwintered polyps (strobilation). So far temperature was defined as the main abiotic factor driving presence/
absence of some jellyfish outbreaks. However, little is known
about combined effects of biotic and abiotic factors on the
fitness of polyp stage. To investigate the survival, growth and
phase transition ecology of Aurelia aurita polyps, we
designed a factorial experiment manipulating food quality
(Artemia salina and two manipulated Acartia tonsa fed with
different prey), food quantity (20 μg C, 5 μg C and 1.5 μg C
polyp
−1
d
−1
) and temperature (13 °C, 20 °C and 27 °C) representing warming scenarios of the North Sea in the late
autumn, early spring and summer seasons. As expected, temperature was the key factor to determine the phase transition
of polyps. Interestingly, while high food concentration and
better food quality could promote the organisms’ production
in each life cycle mode (buds, ephyrae, podocysts). Besides,
food quality seems to compensate the physiological stress
caused by temperature and food concentration. Based on the
findings in this experiment and previous studies, we put forward the polyp’s temperature tolerance curve, which may
help us to understand that the variation of medusae population regarding the overlay and shifting of different environmental factors’ tolerance curve.
10.2.7 Catch Distribution Shifts in Tropical Tuna
Fisheries
Iratxe Rubio
1,2*
, Elena Ojea
2
1
Basque Centre for Climate Change BC3, Sede Building
1, 1st floor. Scientific Campus of the University of the
Basque Country 48940 Leioa, Spain
2
Future Oceans Lab, University of Vigo, Campus Lagoas
Marcosende, 36310 Vigo, Spain
Appendices