250
sus natural food) of three model species (Chaetodon auriga,
Ctenochaetus striatus, Lutjanus fulvus) were quantified.
24% of all species observed across sites were effectively
attracted by bread. Fish biomass was significantly higher in
feeding, than control sites. Taxonomic richness decreased
during bread feeding, compared to 1 h before and after across
sites. Carnivores and omnivores dominated the community,
suggesting concentrated predation pressure. The effect of
artificial feeding on natural foraging rates varied between
species. C. auriga fed significantly more on bread in feeding
sites versus control sites, C. striatus fed less on the benthos
during feeding, compared to before and after, suggesting an
effect on foraging behavior. Stakeholder interviews revealed
differences in perceptions on the issue of fish feeding
between natives and tourists. Paradoxically, natives are
strongly in favor to improve tourist satisfaction, whereas
tourists appreciate snorkeling regardless of whether fish are
artificially attracted. Finding ways for humans to appreciate
wildlife closely while causing minimal disruptions is crucial
to balance awareness raising and conservation. Future
research on fish metabolism and cascading effects on the reef
benthos may reveal further negative impacts of artificial
feeding.
15.3 Abstracts of Poster Presentations
15.3.1 The Effect of Elevated and Fluctuating
pCO 2 Concentrations on the Growth of Calcifying
Marine Epibionts
M. Johnson
1,2#*
, L. Hennigs
2,3#*
, C. Pansch
2
, M. Wall
2
1
Christian-Albrechts Universität zu Kiel, ChristianAlbrechts- Platz 4, 24188 Kiel, Germany
2
GEOMAR Helmholtz-Zentrum für Ozeanforschung
Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
3
Carl-von-Ossietzky Universität Oldenburg, Ammerländer
Heerstrasse 114-118, 26129 Oldenburg, Germany
#shared first authorship
*corresponding authors: mildredjjohnson@gmail.com,
laura.hennigs@uni-oldenburg.de
Keywords: Macroalgae, Environmental fluctuations,
Boundary layer, Epibiont calcification
The projected reduction in surface seawater pH by 2100
has led to a significant increase in ocean acidification
research. These studies have mostly focused on constant
conditions which produced valuable results but provide
limited information on the important role of naturally
occurring environmental fluctuations within and on habitatforming organisms. In temperate regions, marine seaweeds
dominate rocky shores and via their metabolism, photosynthesis and respiration, induce diurnal fluctuations of pH
and oxygen within their surroundings. Dependent on
hydrodynamic conditions, these processes act at the larger
scale (slow flow conditions) shifting environmental conditions within the entire seaweed bed or at smaller scale at the
macroalgae-seawater interface and create unique microenvironments, the so-called boundary layer (BL). In particular, epibionts that live at the macroalgae-seawater interface
are constantly exposed to fluctuating conditions. This raises
the question whether such diurnal variations may amplify
or buffer the responses of organisms to future environmental pressures. To determine the effect of the small scale and
large-scale BL on the development of epibionts, the growth
rates of Electra pilosa and Balanus improvisus where compared on 2 substrates namely Fucus serratus and acrylic
glass slides, under 4 different pCO 2 conditions and 2 temperature regimes. A multifactorial experiment was conducted at the Kiel Indoor Mesocosms programmed with 2
constant (400 and 1250 μatm) and 2 fluctuating pCO 2 concentrations (400/2400 μatm and 100/1250 μatm) testing the
present and future role of small and large-scale BL fluctuations, respectively. These treatments were conducted at 2
different temperatures (10 and 15 °C) simulating present
day and future average temperatures in May. Preliminary
observations indicate that higher growth rates occur on
Fucus substrates and at higher temperatures. Whether the
fluctuating boundary layers of Fucus meadows provide
short term refuge from low pH and O 2 conditions and buffer
the responses to future ocean acidification still warrants
resolve.
15.3.2 Impact of Submarine Groundwater
Discharge on Fish, Plankton and Biofouling
C. Starke
1*
, N. Moosdorf
2
, W. Ekau
2
1
Institut of Hydrobiology and Fishery Science (IHF),
Olbersweg 24, 22767 Hamburg, Germany
2
Leibniz Centre for Tropical Marine Research (ZMT),
Fahrenheitstr. 6, 28359 Bremen, Germany
*corresponding author: cls@zmt-bremen.de
Keywords: Groundwater, Nutrient input, Marine
organisms
Submarine groundwater discharge (SGD) into the sea is
widely spread and increasingly studied. However, the impact
of SGD on marine organisms is still unclear. For better
understanding that effect on fish and plankton abundance as
well as on the early stage of biofouling processes, we investigated submarine wells in a coastal lagoon of Tahiti, French
Polynesia with three different sampling methods. The occurrence and behavior of fish around a wellspring was investigated by means of underwater photos using two GoPro Hero
4 cameras fixed at a freshwater spring and a control site.
Plankton samples were taken at a catchment area of around
six meters around the same spring and the control site to test
if the spring has influence on abundance and composition of
micro- and mesozooplankton. For a biofouling experiment,
settlement panels were installed along a transect through a
Appendices
sus natural food) of three model species (Chaetodon auriga,
Ctenochaetus striatus, Lutjanus fulvus) were quantified.
24% of all species observed across sites were effectively
attracted by bread. Fish biomass was significantly higher in
feeding, than control sites. Taxonomic richness decreased
during bread feeding, compared to 1 h before and after across
sites. Carnivores and omnivores dominated the community,
suggesting concentrated predation pressure. The effect of
artificial feeding on natural foraging rates varied between
species. C. auriga fed significantly more on bread in feeding
sites versus control sites, C. striatus fed less on the benthos
during feeding, compared to before and after, suggesting an
effect on foraging behavior. Stakeholder interviews revealed
differences in perceptions on the issue of fish feeding
between natives and tourists. Paradoxically, natives are
strongly in favor to improve tourist satisfaction, whereas
tourists appreciate snorkeling regardless of whether fish are
artificially attracted. Finding ways for humans to appreciate
wildlife closely while causing minimal disruptions is crucial
to balance awareness raising and conservation. Future
research on fish metabolism and cascading effects on the reef
benthos may reveal further negative impacts of artificial
feeding.
15.3 Abstracts of Poster Presentations
15.3.1 The Effect of Elevated and Fluctuating
pCO 2 Concentrations on the Growth of Calcifying
Marine Epibionts
M. Johnson
1,2#*
, L. Hennigs
2,3#*
, C. Pansch
2
, M. Wall
2
1
Christian-Albrechts Universität zu Kiel, ChristianAlbrechts- Platz 4, 24188 Kiel, Germany
2
GEOMAR Helmholtz-Zentrum für Ozeanforschung
Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
3
Carl-von-Ossietzky Universität Oldenburg, Ammerländer
Heerstrasse 114-118, 26129 Oldenburg, Germany
#shared first authorship
*corresponding authors: mildredjjohnson@gmail.com,
laura.hennigs@uni-oldenburg.de
Keywords: Macroalgae, Environmental fluctuations,
Boundary layer, Epibiont calcification
The projected reduction in surface seawater pH by 2100
has led to a significant increase in ocean acidification
research. These studies have mostly focused on constant
conditions which produced valuable results but provide
limited information on the important role of naturally
occurring environmental fluctuations within and on habitatforming organisms. In temperate regions, marine seaweeds
dominate rocky shores and via their metabolism, photosynthesis and respiration, induce diurnal fluctuations of pH
and oxygen within their surroundings. Dependent on
hydrodynamic conditions, these processes act at the larger
scale (slow flow conditions) shifting environmental conditions within the entire seaweed bed or at smaller scale at the
macroalgae-seawater interface and create unique microenvironments, the so-called boundary layer (BL). In particular, epibionts that live at the macroalgae-seawater interface
are constantly exposed to fluctuating conditions. This raises
the question whether such diurnal variations may amplify
or buffer the responses of organisms to future environmental pressures. To determine the effect of the small scale and
large-scale BL on the development of epibionts, the growth
rates of Electra pilosa and Balanus improvisus where compared on 2 substrates namely Fucus serratus and acrylic
glass slides, under 4 different pCO 2 conditions and 2 temperature regimes. A multifactorial experiment was conducted at the Kiel Indoor Mesocosms programmed with 2
constant (400 and 1250 μatm) and 2 fluctuating pCO 2 concentrations (400/2400 μatm and 100/1250 μatm) testing the
present and future role of small and large-scale BL fluctuations, respectively. These treatments were conducted at 2
different temperatures (10 and 15 °C) simulating present
day and future average temperatures in May. Preliminary
observations indicate that higher growth rates occur on
Fucus substrates and at higher temperatures. Whether the
fluctuating boundary layers of Fucus meadows provide
short term refuge from low pH and O 2 conditions and buffer
the responses to future ocean acidification still warrants
resolve.
15.3.2 Impact of Submarine Groundwater
Discharge on Fish, Plankton and Biofouling
C. Starke
1*
, N. Moosdorf
2
, W. Ekau
2
1
Institut of Hydrobiology and Fishery Science (IHF),
Olbersweg 24, 22767 Hamburg, Germany
2
Leibniz Centre for Tropical Marine Research (ZMT),
Fahrenheitstr. 6, 28359 Bremen, Germany
*corresponding author: cls@zmt-bremen.de
Keywords: Groundwater, Nutrient input, Marine
organisms
Submarine groundwater discharge (SGD) into the sea is
widely spread and increasingly studied. However, the impact
of SGD on marine organisms is still unclear. For better
understanding that effect on fish and plankton abundance as
well as on the early stage of biofouling processes, we investigated submarine wells in a coastal lagoon of Tahiti, French
Polynesia with three different sampling methods. The occurrence and behavior of fish around a wellspring was investigated by means of underwater photos using two GoPro Hero
4 cameras fixed at a freshwater spring and a control site.
Plankton samples were taken at a catchment area of around
six meters around the same spring and the control site to test
if the spring has influence on abundance and composition of
micro- and mesozooplankton. For a biofouling experiment,
settlement panels were installed along a transect through a
Appendices