231
as achievement of management targets, restoration of former
population structures and levels of fishing mortality, we classified only 3 stocks out of the 19 as recovering. We further
investigated the reasons for the lack of recovery applying
regime shift theory. We conducted multiple analyses to detect
the presence of stable states (i.e., trend analyses, detection of
hysteresis), and also examined the relationship between
spawning stock biomass, environmental conditions (sea surface temperature) and fishing pressure to highlight the drivers that could have played a fundamental role in the decline
of these stocks. Our analyses revealed that cod recovery is
hindered by discontinuous behaviors, and the additive effect
of fishing pressure and climate change. These conditions
delay the recovery process or in the worst cases make it even
impossible. Our results are relevant because they show how
additive human and natural drivers, resulting in discontinuous systems´ responses, can prevent the recovery of such an
iconic species such as cod.
10.3.2 A Deep-Sea Sponge-Loop? Tracing Carbon
and Nitrogen from DOM to Sponges
and Detritivores
Clea van de Ven
1*
, Titus Rombouts
1*
, Martijn Bart
1
, Benjamin
Mueller
1
, Jasper de Goeij
1
1
Institute for Biodiversity and Ecosystem Dynamics,
University of Amsterdam, Science Park P.O. Box 94248,
1090 GE Amsterdam, The Netherlands
*corresponding authors: clea.vandeven@student.auc.nl,
titusrombouts@gmail.com
Keywords: Deep-sea sponge-loop, DOM uptake,
Detritivores
Deep-sea sponges form complex ecosystems on the seafloor known as sponge grounds. Their ecological importance
and biotechnological potential are estimated to be similar to,
or even greater than that of other deep-sea ecosystems such
as hydrothermal vents. Sponges are considered to be key
ecosystem drivers on shallow tropical reefs. They take up
carbon and nitrogen from dissolved organic matter (DOM)
which is assimilated in sponge cells, shed as detritus, and
subsequently consumed by detritivores. These steps facilitate the transfer of nutrients from DOM to higher trophic
levels by a process termed “the sponge-loop”. Contrastingly,
the role of sponges in deep-sea food webs is largely unknown.
Recently, ex-situ experiments demonstrated DOM uptake by
deep-sea sponges and subsequent shedding of detritus. This
provided the first evidence for the existence of a sponge-loop
pathway in the deep-sea. However, the final consumption of
sponge-derived detritus by detritivores has yet to be confirmed. With this poster, we present our approach to uncover
unique evidence for carbon and nitrogen transfer in the form
of DOM to sponges into detritus and eventually detritivores.
Isotopically labeled DOM and particulate food (bacteria) are
fed to the sponges to trace the bulk assimilation and respiration rates of
13
C- and
15
N-enriched food. Second, we collect
labeled sponge-derived detritus and determine the uptake
and respiration by deep-sea detritivores (brittle stars).
Corroborative time-lapse observation with detritivores is
used to confirm the consumption of sponge-detritus by detritivores. Preliminary experiments and results will be presented during the conference. Based on these experiments
we expect to provide the first complete assessment of spongemediated carbon and nitrogen cycling in the deep-sea. The
potential presence of a sponge-loop in the deep-sea could
demonstrate how sponge grounds function in their energylimited environment and will aid in the conservation and sustainable exploitation of deep-sea sponge grounds.
10.3.3 A Stressful Environment: Macrobenthic
Bioturbation Under Hypoxia and Heat Waves
A. Böhmer
1,2*
, A. M. Queirós
2
, D. Wain
1
, L. D. Bryant
1
1
University of Bath, Claverton Down, Bath, BA27AY,
United Kingdom
2
Plymouth Marine Laboratory, Prospect Place, The Hoe,
Plymouth, PL13DH, United Kingdom
*corresponding author: A.Boehmer@bath.ac.uk
Keywords: Habitat thresholds, Biological turnover,
Macrobenthic community bioturbation, Biogeochemical
cycling, Climate stressors
Oxygen (O 2 ) and temperature are key environmental
parameters that govern water quality and biogeochemical
processes and define important habitat thresholds for aquatic
life. The activity and biological turnover of benthic organisms
are strongly influenced by variations in these parameters. In
turn, benthic organisms have significant influence on aquatic
O 2 and carbon cycling via bioturbation (i.e., rework of sediment by biota) and respiration (i.e., biological O 2 uptake)
and thus play a highly complex and sensitive role in biogeochemical cycling in natural waters. Evaluation of benthic O 2
dynamics and other biogeochemical fluxes within the water
column and at the sediment-water interface is vital to understanding O 2 and carbon budgets and overall aquatic ecosystem health. Thus, our hypotheses are: (1) Bioturbation
contributes to carbon and O 2 uptake by the sediment; (2)
Environmental stressors (hypoxia & heat waves) impact the
ability of benthic fauna to transport carbon and O 2 into the
sediment. In this study, we are investigating the effects of
bioturbation on benthic (biological) turnover and corresponding O 2 and carbon transport under varying O 2 and temperature conditions. From June to August 2017 laboratory
experiments will be conducted to measure macrobenthic bioturbation and respiration within specially designed mesocosms and respiration chambers. To give realism to
experiments and to do something novel, we will (1) study the
macrobenthic response to the combined effect of concurrent
climate stressors (i.e., O 2 and temperature), (2) unify established work on benthic-water-column interactions, and 3)
Appendices
as achievement of management targets, restoration of former
population structures and levels of fishing mortality, we classified only 3 stocks out of the 19 as recovering. We further
investigated the reasons for the lack of recovery applying
regime shift theory. We conducted multiple analyses to detect
the presence of stable states (i.e., trend analyses, detection of
hysteresis), and also examined the relationship between
spawning stock biomass, environmental conditions (sea surface temperature) and fishing pressure to highlight the drivers that could have played a fundamental role in the decline
of these stocks. Our analyses revealed that cod recovery is
hindered by discontinuous behaviors, and the additive effect
of fishing pressure and climate change. These conditions
delay the recovery process or in the worst cases make it even
impossible. Our results are relevant because they show how
additive human and natural drivers, resulting in discontinuous systems´ responses, can prevent the recovery of such an
iconic species such as cod.
10.3.2 A Deep-Sea Sponge-Loop? Tracing Carbon
and Nitrogen from DOM to Sponges
and Detritivores
Clea van de Ven
1*
, Titus Rombouts
1*
, Martijn Bart
1
, Benjamin
Mueller
1
, Jasper de Goeij
1
1
Institute for Biodiversity and Ecosystem Dynamics,
University of Amsterdam, Science Park P.O. Box 94248,
1090 GE Amsterdam, The Netherlands
*corresponding authors: clea.vandeven@student.auc.nl,
titusrombouts@gmail.com
Keywords: Deep-sea sponge-loop, DOM uptake,
Detritivores
Deep-sea sponges form complex ecosystems on the seafloor known as sponge grounds. Their ecological importance
and biotechnological potential are estimated to be similar to,
or even greater than that of other deep-sea ecosystems such
as hydrothermal vents. Sponges are considered to be key
ecosystem drivers on shallow tropical reefs. They take up
carbon and nitrogen from dissolved organic matter (DOM)
which is assimilated in sponge cells, shed as detritus, and
subsequently consumed by detritivores. These steps facilitate the transfer of nutrients from DOM to higher trophic
levels by a process termed “the sponge-loop”. Contrastingly,
the role of sponges in deep-sea food webs is largely unknown.
Recently, ex-situ experiments demonstrated DOM uptake by
deep-sea sponges and subsequent shedding of detritus. This
provided the first evidence for the existence of a sponge-loop
pathway in the deep-sea. However, the final consumption of
sponge-derived detritus by detritivores has yet to be confirmed. With this poster, we present our approach to uncover
unique evidence for carbon and nitrogen transfer in the form
of DOM to sponges into detritus and eventually detritivores.
Isotopically labeled DOM and particulate food (bacteria) are
fed to the sponges to trace the bulk assimilation and respiration rates of
13
C- and
15
N-enriched food. Second, we collect
labeled sponge-derived detritus and determine the uptake
and respiration by deep-sea detritivores (brittle stars).
Corroborative time-lapse observation with detritivores is
used to confirm the consumption of sponge-detritus by detritivores. Preliminary experiments and results will be presented during the conference. Based on these experiments
we expect to provide the first complete assessment of spongemediated carbon and nitrogen cycling in the deep-sea. The
potential presence of a sponge-loop in the deep-sea could
demonstrate how sponge grounds function in their energylimited environment and will aid in the conservation and sustainable exploitation of deep-sea sponge grounds.
10.3.3 A Stressful Environment: Macrobenthic
Bioturbation Under Hypoxia and Heat Waves
A. Böhmer
1,2*
, A. M. Queirós
2
, D. Wain
1
, L. D. Bryant
1
1
University of Bath, Claverton Down, Bath, BA27AY,
United Kingdom
2
Plymouth Marine Laboratory, Prospect Place, The Hoe,
Plymouth, PL13DH, United Kingdom
*corresponding author: A.Boehmer@bath.ac.uk
Keywords: Habitat thresholds, Biological turnover,
Macrobenthic community bioturbation, Biogeochemical
cycling, Climate stressors
Oxygen (O 2 ) and temperature are key environmental
parameters that govern water quality and biogeochemical
processes and define important habitat thresholds for aquatic
life. The activity and biological turnover of benthic organisms
are strongly influenced by variations in these parameters. In
turn, benthic organisms have significant influence on aquatic
O 2 and carbon cycling via bioturbation (i.e., rework of sediment by biota) and respiration (i.e., biological O 2 uptake)
and thus play a highly complex and sensitive role in biogeochemical cycling in natural waters. Evaluation of benthic O 2
dynamics and other biogeochemical fluxes within the water
column and at the sediment-water interface is vital to understanding O 2 and carbon budgets and overall aquatic ecosystem health. Thus, our hypotheses are: (1) Bioturbation
contributes to carbon and O 2 uptake by the sediment; (2)
Environmental stressors (hypoxia & heat waves) impact the
ability of benthic fauna to transport carbon and O 2 into the
sediment. In this study, we are investigating the effects of
bioturbation on benthic (biological) turnover and corresponding O 2 and carbon transport under varying O 2 and temperature conditions. From June to August 2017 laboratory
experiments will be conducted to measure macrobenthic bioturbation and respiration within specially designed mesocosms and respiration chambers. To give realism to
experiments and to do something novel, we will (1) study the
macrobenthic response to the combined effect of concurrent
climate stressors (i.e., O 2 and temperature), (2) unify established work on benthic-water-column interactions, and 3)
Appendices