228
explanatory variables for the dependent variables SSB and
R. Linear and additive models were used to find changes in
the functional relationship. The analyses indicated that the
herring stocks experienced changes over the course of the
time series, but only few underwent regime shifts with fishing pressure being the major driver of these dynamics.
Those results will be compared to dynamics of cod (Gadus
morhua) stocks from nearby regions and possible differences will be investigated.
10.2.3 Effects of Wounding on Detritus
Production by Caribbean Reef Sponges
M. L. Folkers
1,2*
, K. C. Tomson
1,2
, B. Mueller
1,2
, J. M. de
Goeij
1,2
1
Caribbean Marine Biological Institute (CARMABI),
Piscaderabaai, Willemstad, Curaçao
2
present Address: Department of Freshwater and Marine
Ecology (FAME), Institute for Biodiversity and Ecosystem
Dynamics (IBED), University of Amsterdam (UvA), Science
Park 904, 1098 XH Amsterdam, Netherlands
*corresponding author: mainahfolkers@gmail.com
Keywords: Reef sponges, Detritus production, Wounding
Coral reefs are the most biodiverse and productive ecosystems. To thrive in oligotrophic waters efficient energy and
nutrient recycling is essential. Despite being the largest
energy and nutrient source on coral reefs, dissolved organic
matter (DOM) is primarily consumed by microbes and
sponges. Encrusting cavity sponges use most of the energy
and nutrients obtained from filtering DOM to rejuvenate
their filtration apparatus. Old filter cells are frequently shed
and expelled as detritus. Sponge detritus production is
increasingly recognized to be an important link to pass
energy and nutrients stored in DOM through sponges to
detritivores and subsequently higher trophic levels. However,
little is known about how environmental factors, such as
increased stress, influence sponge detritus production rate.
This study examined the effects of wounding to simulate
stress on the detritus production rate of four encrusting
Caribbean reef sponge species (Scopalina ruetzleri,
Haliclona vansoesti, Halisarca caerulea and Chondrilla
caribensis). Based on previous research, detritus production
rate is expected to decrease in wounded sponges compared
to healthy sponges. Detritus was collected on six consecutive
days from healthy and wounded sponges. A linear mixed
effects analysis showed that mean detritus production rate of
wounded S. ruetzleri individuals was significantly affected
by wounding (Χ
2
(1) = 8.8274, p = 0.0030). Wounding lowered the mean detritus production rate of healthy S. ruetzleri
individuals (μ = 0.0204 mg/cm
2
/h ± 0.0039 (SE)) by 46%. In
contrast, no effect of wounding on detritus production rates
was found in H. vansoesti, H. caerulea and C. caribensis.
This suggests that the effects of wounding are not similar
among different Caribbean reef sponge species. Energy and
nutrients taken up by sponges are estimated to be in the same
order of magnitude as gross primary production on coral
reefs. Reduced detritus production by some sponges due to
increased stress may contributed to ecosystem regime shifts
and reduce ecosystem resilience.
10.2.4 The Nutrient Limitation Status of Benthic
Reef Macroalgae (Phaeophyceae) in Moorea,
French Polynesia
Hannah S. Earp
1*
, Mona Andskog
1
, Joost den Haan
2,3
, Mirta
Teichberg
4
, Deron Burkepile
5
, Maggy M. Nugues
2,6
1
Universität Bremen, Bibliothekstraße 1, 28359 Bremen,
Germany
2
EPHE, PSL Research University, UPVD-CNRS,
USR3278 CRIOBE, F-66860 Perpignan, France
3
Max Planck Institute for Marine Microbiology,
Celsiusstraße 1, 28359 Bremen, Germany
4
Leibniz Centre for Tropical Marine Sciences,
Fahrenheitstraße 6, 28359 Bremen, Germany
5
University of California – Santa Barbara, Santa Barbara,
CA 93106, USA
6
Labex Corail, CRIOBE, 98729 Moorea, French Polynesia
*corresponding author: hannahsearp@hotmail.com
Keywords: Nutrient limitation, Macroalgae, Coral reef,
NIFT experiments, Growth
A central paradigm of coral reef ecosystems is that algal
productivity is limited by nutrient availability. Nutrient
enrichment can relieve this limitation, allowing algae to proliferate at the expense of live coral. It is widely accepted that
remote Pacific island reefs are more resilient to phase-shifts
in part because they do not receive periodic influxes of
nutrient- rich aeolian dust. To investigate the role of nutrients on algal proliferation in the Pacific, we compared the
response of brown macroalgae to iron, nitrogen and phosphorous enrichment in Moorea, French Polynesia. The
nutrient- limited productivity of three macroalgae (Dictyota
spp., Sargassum pacificum, Turbinaria ornata), collected
from sites along a human population gradient, was examined using Nutrient Induced Fluorescence Transient (NIFT)
experiments. The nutrient-limited growth of two macroalgae (S.pacificum, T.ornata) was determined using a 14-day
in- situ fertilization experiment. It was hypothesized that
iron would be the primary nutrient limiting both productivity and growth. Our NIFT results found macroalgae in the
vicinity of highly-populated areas to exhibit greater nutrient-limited productivity, compared to macroalgae nearby
less-populated areas. No significant difference in productivity between nutrient treatments or algal species was
observed. The in-situ fertilization results found no significant biomass increase of the two macroalgae species in
response to the different nutrient treatments. Our results
suggest that nutrient limitation is not homogeneous across
Moorea’s reefs and exhibits strong environmental depenAppendices
explanatory variables for the dependent variables SSB and
R. Linear and additive models were used to find changes in
the functional relationship. The analyses indicated that the
herring stocks experienced changes over the course of the
time series, but only few underwent regime shifts with fishing pressure being the major driver of these dynamics.
Those results will be compared to dynamics of cod (Gadus
morhua) stocks from nearby regions and possible differences will be investigated.
10.2.3 Effects of Wounding on Detritus
Production by Caribbean Reef Sponges
M. L. Folkers
1,2*
, K. C. Tomson
1,2
, B. Mueller
1,2
, J. M. de
Goeij
1,2
1
Caribbean Marine Biological Institute (CARMABI),
Piscaderabaai, Willemstad, Curaçao
2
present Address: Department of Freshwater and Marine
Ecology (FAME), Institute for Biodiversity and Ecosystem
Dynamics (IBED), University of Amsterdam (UvA), Science
Park 904, 1098 XH Amsterdam, Netherlands
*corresponding author: mainahfolkers@gmail.com
Keywords: Reef sponges, Detritus production, Wounding
Coral reefs are the most biodiverse and productive ecosystems. To thrive in oligotrophic waters efficient energy and
nutrient recycling is essential. Despite being the largest
energy and nutrient source on coral reefs, dissolved organic
matter (DOM) is primarily consumed by microbes and
sponges. Encrusting cavity sponges use most of the energy
and nutrients obtained from filtering DOM to rejuvenate
their filtration apparatus. Old filter cells are frequently shed
and expelled as detritus. Sponge detritus production is
increasingly recognized to be an important link to pass
energy and nutrients stored in DOM through sponges to
detritivores and subsequently higher trophic levels. However,
little is known about how environmental factors, such as
increased stress, influence sponge detritus production rate.
This study examined the effects of wounding to simulate
stress on the detritus production rate of four encrusting
Caribbean reef sponge species (Scopalina ruetzleri,
Haliclona vansoesti, Halisarca caerulea and Chondrilla
caribensis). Based on previous research, detritus production
rate is expected to decrease in wounded sponges compared
to healthy sponges. Detritus was collected on six consecutive
days from healthy and wounded sponges. A linear mixed
effects analysis showed that mean detritus production rate of
wounded S. ruetzleri individuals was significantly affected
by wounding (Χ
2
(1) = 8.8274, p = 0.0030). Wounding lowered the mean detritus production rate of healthy S. ruetzleri
individuals (μ = 0.0204 mg/cm
2
/h ± 0.0039 (SE)) by 46%. In
contrast, no effect of wounding on detritus production rates
was found in H. vansoesti, H. caerulea and C. caribensis.
This suggests that the effects of wounding are not similar
among different Caribbean reef sponge species. Energy and
nutrients taken up by sponges are estimated to be in the same
order of magnitude as gross primary production on coral
reefs. Reduced detritus production by some sponges due to
increased stress may contributed to ecosystem regime shifts
and reduce ecosystem resilience.
10.2.4 The Nutrient Limitation Status of Benthic
Reef Macroalgae (Phaeophyceae) in Moorea,
French Polynesia
Hannah S. Earp
1*
, Mona Andskog
1
, Joost den Haan
2,3
, Mirta
Teichberg
4
, Deron Burkepile
5
, Maggy M. Nugues
2,6
1
Universität Bremen, Bibliothekstraße 1, 28359 Bremen,
Germany
2
EPHE, PSL Research University, UPVD-CNRS,
USR3278 CRIOBE, F-66860 Perpignan, France
3
Max Planck Institute for Marine Microbiology,
Celsiusstraße 1, 28359 Bremen, Germany
4
Leibniz Centre for Tropical Marine Sciences,
Fahrenheitstraße 6, 28359 Bremen, Germany
5
University of California – Santa Barbara, Santa Barbara,
CA 93106, USA
6
Labex Corail, CRIOBE, 98729 Moorea, French Polynesia
*corresponding author: hannahsearp@hotmail.com
Keywords: Nutrient limitation, Macroalgae, Coral reef,
NIFT experiments, Growth
A central paradigm of coral reef ecosystems is that algal
productivity is limited by nutrient availability. Nutrient
enrichment can relieve this limitation, allowing algae to proliferate at the expense of live coral. It is widely accepted that
remote Pacific island reefs are more resilient to phase-shifts
in part because they do not receive periodic influxes of
nutrient- rich aeolian dust. To investigate the role of nutrients on algal proliferation in the Pacific, we compared the
response of brown macroalgae to iron, nitrogen and phosphorous enrichment in Moorea, French Polynesia. The
nutrient- limited productivity of three macroalgae (Dictyota
spp., Sargassum pacificum, Turbinaria ornata), collected
from sites along a human population gradient, was examined using Nutrient Induced Fluorescence Transient (NIFT)
experiments. The nutrient-limited growth of two macroalgae (S.pacificum, T.ornata) was determined using a 14-day
in- situ fertilization experiment. It was hypothesized that
iron would be the primary nutrient limiting both productivity and growth. Our NIFT results found macroalgae in the
vicinity of highly-populated areas to exhibit greater nutrient-limited productivity, compared to macroalgae nearby
less-populated areas. No significant difference in productivity between nutrient treatments or algal species was
observed. The in-situ fertilization results found no significant biomass increase of the two macroalgae species in
response to the different nutrient treatments. Our results
suggest that nutrient limitation is not homogeneous across
Moorea’s reefs and exhibits strong environmental depenAppendices