10.5061/DRYAD.QV9S4MWBW
Doo, Steve
0000-0002-3346-6152
Leibniz Center for Tropical Marine Ecology
Leplastrier, Aero
Australian National University
Graba-Landry, Alexia
James Cook University
Harianto, Januar
University of Sydney
Coleman, Ross
University of Sydney
Byrne, Maria
University of Sydney
Data from: Amelioration of ocean acidification and warming effects through
physiological buffering of a macroalgae
Dryad
dataset
2020
physiological buffering
Macroalgae
Ocean warming
Ian Potter Foundation
https://ror.org/058smmw67
Lizard Island Doctoral Fellowship
American Australian Association
https://ror.org/04fxadq33
Sir Keith Murdoch Fellowship
PADI Foundation
https://ror.org/01pxxsm33
Australian Coral Reef Society
https://ror.org/01s62z461
Cushman Foundation for Foraminiferal Research
https://ror.org/00zkk0e65
Great Barrier Reef Foundation
https://ror.org/00d4phf77
2021-07-02T00:00:00Z
2021-07-02T00:00:00Z
en
35710 bytes
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Concurrent anthropogenic global climate change and ocean acidification is
expected to have a negative impact on calcifying marine organisms. While
knowledge of biological responses of organisms to oceanic stress has
emerged from single species experiments, these do not capture ecologically
relevant scenarios where the potential for multi-organism physiological
interactions is assessed. Marine algae provide an interesting case study,
as their photosynthetic activity elevates pH in the surrounding
microenvironment, potentially buffering more acidic conditions for
associated epiphytes. We present findings that indicate increased
tolerance of an important epiphytic foraminifera, Marginopora vertebralis,
to the effects of increased temperature (±3 °C) and pCO2 (~1000 µatm) when
associated with its common algal host, Laurencia intricata. Specimens of
M. vertebralis were incubated for 15 days in flow-through aquaria
simulating current and end-of-century temperature and pH conditions.
Physiological measures of growth (change in wet weight), calcification
(measured change in total alkalinity in closed bottles), photochemical
efficiency (Fv/Fm), total chlorophyll, photosynthesis (oxygen flux), and
respiration, were determined. When incubated in isolation, M. vertebralis
exhibited reduced growth in end-of-century projections of ocean
acidification conditions, while calcification rates were lowest in the
high-temperature, low-pH treatment. Interestingly, association with L.
intricata ameliorated these stress effects with the growth and
calcification rates of M. vertebralis being similar to those observed in
ambient conditions. Total chlorophyll levels in M. vertebralis decreased
when in association with L. intricata, while maximum photochemical
efficiency increased in ambient conditions. Net production estimates
remained similar between M. vertebralis in isolation and in association
with L. intricata, although both production and respiration rates of M.
vertebralis were significantly higher when associated with L. intricata.
These results indicate that the association with L. intricata increases
the resilience of M. vertebralis to stress, providing one of the first
examples of physiological buffering by a marine alga that can ameliorate
the negative effects of changing ocean conditions.
Collection and acclimation Specimens of Marginopora vertebralis (as
identified by Renema 2018) and Laurencia intricata were collected from
Coconut Beach (1-3 m depth), Lizard Island (014°40’08”S, 145°27’34”E) on
the Great Barrier Reef, Australia, in October 2015 (Fig. 1). Samples were
immediately transported back to Lizard Island Research Station and placed
into flow-through ambient seawater conditions and light for 5 days to
acclimate to laboratory conditions. Specimens of L. intricata were then
separated into ~1 g (wet weight) replicates, and all visible epiphytes (M.
vertebralis and other LBFs such as Calcarina hispida, Amphistegina
lobifera, and Baculogypsina sphaerulata) removed. The M. vertebralis were
separated into experimental replicates in which 6 M. vertebralis (~0.5 g
wet weight, all approximately similar size of ~5 mm diameter) were placed
into 60 mL jars with 40 mL of seawater, similar to densities found in situ
(Doo, pers. obs.). The experimental treatment groups of M. vertebralis
only, and L. intricata with M. vertebralis were established prior to the
start of the experiment, and acclimated 3 days before the initiation of
the experiment. Specimens were incubated in polypropylene jars with a hole
cut from the side to prevent overflow over the top. A 462 µm plankton mesh
was glued to the side of the jar to allow for overflow of water through
the mesh, while maintaining flow-through conditions, and resulted in a
total of ~40 mL water in each container. Light was provided using LED cool
white lights (LED Type 3528) to an intensity of ~100 µmol photos m-2 s-1
for the duration of the experiment (2 weeks) in a 12hr:12hr, day-night
cycle. A flow-through dripper tap system was used for experimental water
delivery (~40 mL min-1). Experimental conditions were gradually reached
over a three-day period, with an increase of 1°C, and decrease of 0.1 pH
unit each day prior to the start of the experiment when all replicates
were incubated in ambient temperature (~25.5°C and ~pHTotal 7.95
conditions). Experimental water was collected from Lizard Island lagoon
and filtered with a 5 µm filter bag, and delivered into 60L header tanks,
from which all treatment groups were supplied incubation water. Two
temperatures (ambient [26°C] and high [29°C]), and two pH’s (ambient [8.0]
and low [7.7] pHTotal units) fully orthogonal treatment groups were used.
To determine the effect of symbiosis of L. intricata and M. vertebralis,
10 replicates each of M. vertebralis only, and L. intricata with M.
vertebralis were incubated in each of the pH/temperature treatment groups
for a total of 80 replicates. Incubation parameters and seawater chemistry
The seawater pH and temperature conditions were controlled using a Neptune
Apex system dosing pure CO2 to regulate pH. In the experiment, a total of
4 sumps were used, one for each manipulated seawater condition (see
above). This water was pumped into individual jars (see above),
maintaining independence between replicates. Total alkalinity, pH, and
temperature of the header tanks were measured on a daily basis, from
randomly selected drippers. Total alkalinity samples were filtered with a
0.22 µm filter prior to analysis to eliminate possible contamination of
calcium carbonate in the sample and measured using open-cell
potentiometric titrations (DOE 1994). Seawater pH was monitored using
m-cresol spectrophotometric measurements on an Ocean Optics USB4000+
spectrophotometer, and pHTotal calculated based using standard protocols
(DOE 1994). These were referenced to seawater Certified Reference Material
(CRM), Batch 161, prepared by A. Dickson in the Scripps School of
Oceanography. Temperature and salinity measurements were collected with
Vernier TMP-BTA and CON-BTA probes, respectively. Seawater parameters
remained stable throughout the experimental incubation (Table 1). Growth
measurements The wet weight of M. vertebralis across individual replicates
were pooled within replicate jars and measured prior to the start of the
experiment, and at the termination using a Mettler-Toledo ML240 balance to
10-4g resolution. Measurements were then converted into a percentage daily
change in weight. In treatments of both L. intricata and M. vertebralis,
only the pooled M. vertebralis from each replicate were weighed at the
initiation and termination of the experiment. Instantaneous calcification
measurements After a 2-week incubation, alkalinity anomaly measurements
were made using close bottle experiments as a proxy of instantaneous
calcification. Organisms were carefully sealed in ~20mL glass
scintillation vials with their chosen treatment group water, and in the
case of the algal associated groups, with the algal hosts. The sealed
vials were immersed in the appropriate flow-through water system to
maintain treatment temperature. Treatment groups were incubated for 8h in
light conditions. Analyses of water samples for total alkalinity were as
above, and calcification (G) was calculated using Eqn. 1: TA is total
alkalinity (µmol kg-1), p is seawater density, V is chamber volume (mL),
w.w. is wet weight (mg), and T is incubation time (h). All calculated
values were normalized to final wet weight.
G(µmolCaCO3)=-0.5×∆TA×ρ×V×w.w.-1×T-1 (Eqn. 1) Photochemical efficiency
measurements At the termination of the experiment, maximum photochemical
efficiency (Fv/Fm) data were measured using WALZ DIVING-PAM underwater
fluorometer (similar to Schmidt et al. 2014a). Measurements were recorded
4 hours after sunset in dark conditions, and individual M. vertebralis,
and averaged across pseudoreplicate M. vertebralis within individual
treatments. Total chlorophyll measurements Following measurement of wet
weight, samples were immediately frozen (-20°C) in dark conditions and
stored for chlorophyll analyses. Samples were placed in 15 mL
polypropylene plastic tubes with 10mL of 90% acetone, and subsequently
mechanically ground with a hard metal rod. Samples were then incubated in
4°C overnight in the dark. Absorbance measurements were then taken from
the supernatant using an Ocean Optics usb4000+ spectrophotometer, and
wavelengths of 630nm, 647nm, 664nm, and 691nm were recorded. Total
chlorophyll was calculated based on universal equations developed by
(Ritchie 2008). In treatments of both L. intricata and M. vertebralis, M.
vertebralis were pooled within the replicate sample jar, and measured
separately. All measurements were normalized to final wet weight of the
corresponding M. vertebralis replicate. Oxygen flux measurements Oxygen
flux measurements were made with a Presens Oxy-10 mini 10-channel optical
sensor. At the end of the 15-day incubation period, oxygen flux
measurements were taken in 30 mL glass scintillation vials that were
gently stirred. Replicate samples (including L. intricata in association
treatments) were gently placed in the glass jars with corresponding pH and
temperature conditions, and allowed to acclimate for at least 5 minutes
before measurements were recorded. For oxygen production measurements,
light conditions in replicates were ~100 µmol photons m-2 s-1 during
measurements (similar to incubation levels) and measured for a total of
~30 min in light conditions first. Subsequently, respiration was measured
in dark conditions for ~30 min, allowing for 5 min of acclimation, and
rate of oxygen consumption measured after the acclimation period. All
analyses were performed using standard protocols for LBFs outlined in
(Uthicke and Fabricius 2012). As the association treatment of M.
vertebralis was incubated with L. intricata, an additional set of
experiments was performed to separate the effect of LBF from macroalgae by
independently measuring oxygen flux rates of algae in isolation. A total
of 10 replicates were measured using similar incubations protocols
described above, and the average of the four pH and temperature treatment
groups were subtracted from the L. intricata with M. vertebralis
replicates to obtain oxygen flux measurements of M. vertebralis in
association treatment groups (Table 2). Statistical analyses For growth
rate, instantaneous calcification, maximum photochemical efficiency
(Fv/Fm), total chlorophyll, and oxygen flux measurement data, a three-way
ANOVA was performed using pH (amb, -0.3 pH units), temperature (amb, and
+3°C), and association (no association—treatments of M. vertebralis only,
and with association--treatments of M. vertebralis and L. intricata) as
fixed factors. Assumptions of ANOVA (homogeneity of variance and
normality) were tested and met. All analyses were performed in R Tukey HSD
test analyses conducted with the agricolae package.
Metadata are provided on the first tab of the excel file.