Carbon Dioxide-induced changes in natural Antarctic microbial community at an Antarctic coastal site

Chair: Ken Caldeira

Alyce Hancock1,2, Andrew Davidson2, Rick van den Enden2, Kai Schulz3 and Andrew McMinn1

1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, 7001, Australia

2Australian Antarctic Division, Kingston, Tasmania, 7050, Australia

3Southern Cross University, East Lismore, NSW, 2480, Australia

 

Background:

Marine microbes support the vast wealth of Antarctic life, underpinning fisheries productivity and contributing significantly to the mediation of global climate.  Their small size, lack of protection and rapid growth mean marine microbes are vulnerable to changes in ocean chemistry and likely to be sensitive indicators of CO2-induced stress. Antarctic waters are amongst the most vulnerable to ocean acidification however the effects of increased CO2 on Antarctic marine microbes are poorly understood.

Methods:

Seawater off Davis Station, Antarctica was incubated in 6 x 650 l polythene tanks (minicosms).  The fCO2 concentration in the tanks was adjusted to values from 343 (ambient) to 1641 µatm.   Samples were periodically collected during the incubation to determine the composition and abundance of microbes via light and electron microscopy.

Findings:

Different taxa responded differently to changes in fCO2. At ambient/low fCO2 levels (343-507ppm) the community had a high diversity of both small and large cells. Relative to the low fCO2  control, treatments exposed to high fCO2  (953-1641 ppm) the abundance of large cells, mainly centric diatoms, declined and the community became dominated by small pennate species. Response curves of the various phytoplankton differ among species, driving changes in community composition and total phytoplankton abundance. Overall the promotion of small cells occurred at lower fCO2 than the inhibition of large taxa, resulting in the net promotion of phytoplankton abundance and biomass at intermediate fCO2  concentrations (506-

953ppm).

Conclusions:

The results from this experiment provide insights potential changes to marine microbial communities in future ocean conditions; changes that may alter biogeochemistry and biogeochemistry in Antarctic waters beyond the end of this century.

Using bacterial extracellular enzymes to assess whether natural CO2 vents are robust analogues of the future ocean

Chair: Ulf Riebesell

Law, C. S. (1,2), Burrell, T.J. (3), Sander, S.G. (2), Maas, E.W. (1)
1 National Institute of Water and Atmospheric Research Ltd, Greta Point, Kilbirnie, Wellington, 6002, New Zealand.
2 Department of Chemistry, University of Otago, Dunedin, New Zealand
3 Victoria University of Wellington, School of Biological Sciences, Wellington, New Zealand

Background
Recent research indicates that bacterial extracellular activity is sensitive to ocean acidification with potential implications for the cycling and fate of organic matter. Natural CO 2 vent systems represent potential analogues of the future high CO2 ocean, and so offer a complimentary approach to small-scale perturbation experiments for examining potential future ecosystem impacts of ocean acidification.

Methods
We assessed the potential of CO2 vents in the Bay of Plenty (North Island, New Zealand), by comparing bacteria composition, productivity and extracellular enzyme activity over the vents with upstream control water and also control water adjusted to the same pH as the vent water. This allowed us to determine whether elevated CO2 was the primary driver of change in bacteria community, aminopeptidase and glucosidase activity, or whether other factors in vent water influenced the response.

Findings
Both the vent and acidified control water exhibited higher potential bulk and cell-specific glucosidase activity relative to control water; however, vent water glucosidase activity was double that of the acidified water, as was bacterial production in one experiment. There were also significant differences in bacterial community composition in the vent water after 84 hours incubation, including the presence of extremophiles.

Conclusions
The results suggest that pH was not the only factor influencing bacterial processes in water overlying the CO2 vent. This highlights the importance of characterizing vent water biogeochemical and microbial composition to confirm that natural CO2 vents are robust analogues for the future acidified ocean.

Decreased pH increases predation rates of a gelatinous predator

Chair: Ken Caldeira

Edd Hammill (1)*, Ellery Johnson (2), Januar Harianto (3), Maria Byrne (3)

1 Utah State University, Logan, UT, 84341, USA
2 University of Technology Sydney, NSW 2006, Australia
3 University of Sydney, NSW 2006, Australia

Background
Oceanic zooplankton form the key link between primary producers and higher trophic levels in the world’s largest food chains. This role as a key link means any disruption to predator-prey interactions within the zooplankton community could have far-reaching consequences for oceanic food webs. Single-species experiments show how ocean acidification can dramatically affect zooplankton exoskeletons. Should ocean acidification reduce the ability of the exoskeleton to perform its defensive functions, pH-mediated changes to exoskeleton thickness need not be fatal in isolation, as sub-lethal changes may increase susceptibility to predation.

Methods
We conducted a two-way experiment to understand how changes in oceanic pH affect trophic interactions between calcified zooplankton and a gelatinous predator. pH levels were set at either ambient (pH 8.2) or reduced (pH 7.8), and crossed with the presence/absence of the cubozoan jellyfish Carybdea rastoni.

Findings
In isolation, reduced pH or the presence of Carybdea rastoni led to changes in zooplankton community composition. Crucially, the combined effects of changes in pH and Carybdea rastoni had a greater impact on overall zooplankton community composition than would be predicted from combining the effect of each factor in isolation. It appeared that this antagonistic effect was generated by low pH increasing predation rates of Carybdea rastoni on the most abundant zooplankton subclass (copepoda).

Conclusions
Our results indicate that the ecological consequences of changes in oceanic pH may be greater than predicted from single-species experiments alone. By adjusting the strength of interactions between predators and prey, changes to ocean pH have the potential to destabilise population dynamics and community structure, despite not being fatal in and of themselves. We suggest that increased acidity may benefit gelatinous predators by increasing prey availability, potentially increasing the risk of jelly fish blooms.

Future ocean acidification and temperature rise alters community structure and diversity in marine benthic communities

Chair: Ken Caldeira

Rachel Hale (1)*, Martin Solan (1), Jasmin Godbold (1)

1 University of Southampton, Ocean and Earth Science, Waterfront Campus, National Oceanography Centre Southampton, SO14 3ZH

Background
Most studies of the synergistic effects of low pH hypercapnia and temperature increase have focused on individual species in isolation and few experiments investigate the effects of either on intact communities. Complex community dynamics and species interactions have the potential to ameliorate or enhance environmental stress related effects through competitive, predatory and positive or negative symbiotic relationships. Single species mesocosm experiments are therefore unlikely to provide results that will be realised in natural environments.

Methods
To determine the effects of the combined stressors of low pH hypercapnia and elevated temperature on the marine benthic habitat whole communities (macrofauna, meiofauna and microbial fauna) were incubated in the laboratory. After medium term exposure species were identified and enumerated to the lowest taxonomic level.

Findings
Communities showed significant changes in structure and diversity in response to the combined stressors of low pH hypercapnia and increased temperature. The calcifying groups molluscs, echinoderms, and copepods were the most vulnerable to the future conditions and many species were absent in the treatments exposed to the highest CO2 levels. Species shown to be vulnerable to low pH or high temperature in other single species based studies, such as nematodes, increased in abundance due to the relief of predation in low pH and high temperature treatments, however nematode species diversity decreased. We also observed a functional shift in the bacterial groups present with a large reduction in the abundance of both bacterial and archaeal ammonium oxidisers and nitrite reducers.

Conclusions
Species interactions observed within these community studies show the importance of considering both direct physiological and indirect ecological and behavioural effects that occur within multispecies assemblages when attempting to predict the consequences of ocean acidification and global warming on marine communities.

The White Island Blitz: Investigating a Southern Hemisphere temperate vent system

Chair: Ulf Riebesell

Abigail M Smith (1), Miles D. Lamare (1), Sylvia G. Sander (2), Sally Carson (3), the White Island Blitz Team
1 Department of Marine Science, University of Otago, Dunedin 9010, New Zealand
2 Department of Chemistry, University of Otago, Dunedin 9010, New Zealand
3 New Zealand Marine Studies Centre, University of Otago, Portobello, New Zealand

Natural CO 2 vents allow study of the effects of climate change on marine organisms on a different scale from laboratory-based studies. The advantages of acclimated organisms, integrated ecosystems and natural variability outweigh the disadvantages that may be posed by emissions such as sulphur or copper. This study outlines a preliminary investigation into the suitability of natural CO2 vents near White Island, Bay of Plenty, New Zealand (37°31.19°S, 117°10.85°E) for climate change research by characterising water chemistry, planktonic communities, and benthic algae and invertebrates from vent and control locations during a single week in the (southern) spring.

A “blitz” consisting of 17 scientists from 8 institutions in New Zealand, Australia, New Caledonia, Belgium, Germany and the UK was undertaken in early December 2015. Divers and snorkelers on two vessels sampled vent gases, water, plants and animals. Moored instruments collected data on water movement, temperature, salinity, and pH all week long. At the same time, a shore-based team conveyed information about the importance of vent communities to local tourist operators, media, the public, teachers, and school children.

Preliminary data suggest that White Island can provide a suitable natural laboratory for studying temperate marine systems of the future. More than that, we demonstrate the usefulness of multi-scientist expeditions to ascertain connections and relationships in a volcanic vent setting. We also reflect on the importance of community involvement and engagement when engaging in major scientific expeditions.

Coral Reef within a Hydrothermal Vent as an Indicator to the Future of Shallow Water Tropical Reefs Threatened by Ocean Acidification

Chair: Ana Queiros

Nithiyaa Nilamani (1)*, Zulfigar Yasin (1,2), Vashiraporn Sriboonruang (2), Zulfikar (1,3), Norhanis Razalli (1), and Aileen Tan Shau Hwai (1)

1 Marine Science Lab, School of Biological Sciences, Universiti Sains Malaysia, Minden, Penang, 11800, Malaysia
2 Institute of Oceanography and Environment, Universiti Terengganu Malaysia, Kuala Terengganu, Terengganu, 21030, Malaysia
3 Universitas Malikussaleh, Lhokseumawe, Provinsi Acheh, Indonesia

Background
Naturally acidified reef ecosystem such as hydrothermal vent has become a natural laboratory for ocean acidification study. The pH of seawater at the study area ranged from 6.99 to 8.01, which approaches the projected scenarios of the year 2100.

Methods
Field survey was carried out to measure the in-situ pH, temperature and salinity at study sites. 5 meter long transect were laid parallel to the shore at 4 m depth (5 transects at hydrothermal site and 1 at control site). Photographs were taken at every meter along the transect to determine the coral cover and species diversity.

Findings
The gas produced in the vicinity of the hydrothermal vent affected the pH of the seawater in the area. The pH of seawater ranged from 6.99 to 8.01. The study also indicates a significant increase (R2=0.916, P<0.05) in live coral cover and diversity as it gets away from the vent following the increase in pH towards normal seawater values. Highest live coral cover was recorded at the furthest station from the vent (0.48 ± 0.08m2) with 13 coral genera. The dominant coral that was found to be surviving in such area was Porites sp.

Conclusions
This provides an opportunity to look at the effect of the acidified seawater on the natural ecology of shallow water reefs and adaptation of the reef to this extreme environment.

Scaling up experimental ocean acidification and warming research: from individuals to the ecosystem

Chair: Victoria Cole

Ana Queirós (1), José Fernandes (1), Sarah Faulwetter (2), Joana Nunes (1), Samuel Rastrick (3, 4), Nova Mieszkowska (5), Yuri Artioli (1), Andrew Yool (6), Piero Calosi (3, 7), Christos Arvanitidis (2) , Helen Findlay (1), Manuel Barange (1), William Cheung (8) and Stephen Widdicombe (1)<o:p></o:p>

1Plymouth Marine Laboratory, PL1 3DH Plymouth, UK
2Hellenic Centre for Marine Research, Heraklion, 710 03 Crete, Greece
3Marine Biology and Ecology Research Centre, Plymouth University, PL4 8AA Plymouth,UK
4 Institute of Marine Research in Norway, Nordnesgaten 50, 5005 Bergen, Norway
5Marine Biological Association of the United Kingdom, PL1 2PB Plymouth, UK
6National Oceanography Centre, SO14 3ZH Southampton, UK
7 Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC G5L 3A1, Canada
8Fisheries Centre, University of British Columbia, V6T 1Z4 Vancouver, Canada

Background
Understanding long-term, ecosystem-level impacts of climate change is challenging because experimental research frequently focuses on short-term, individual-level impacts in isolation.<o:p></o:p>

Methods
We address this shortcoming first through an inter-disciplinary ensemble of novel experimental techniques to investigate the impacts of 14-month exposure to ocean acidification and warming (OAW) on the physiology, activity, predatory behaviour and susceptibility to predation of an important marine gastropod (Nucella lapillus). We simultaneously estimated the potential impacts of these global drivers on N. lapillus population dynamics and dispersal parameters. We then used these data to parameterise a dynamic bioclimatic envelope model, to investigate the consequences of OAW on the distribution of the species in the wider NE Atlantic region by 2100. The model accounts also for changes in the distribution of resources, suitable habitat and environment simulated by finely resolved biogeochemical models, under three IPCC global emissions scenarios.

Findings
Experiments showed that temperature had the greatest impact on individual-level responses, while acidification has a similarly important role in the mediation of predatory behaviour and susceptibility to predators. Changes in Nucella predatory behaviour appeared to serve as a strategy to mitigate individual-level impacts of acidification, but the development of this response may be limited in the presence of predators. The model projected significant large-scale changes in the distribution of Nucella by the year 2100 that were exacerbated by rising greenhouse gas emissions. These changes were spatially heterogeneous, as the impact of OAW on the combination of responses considered by the model varied depending on local environmental conditions and resource availability.<o:p></o:p>

Conclusions
Changes in macro-scale distributions cannot be predicted by investigating individual level impacts in isolation, or by considering climate stressors separately. Scaling up the results of experimental climate change research requires approaches that account for long-term, multi-scale responses to multiple stressors, in an ecosystem context.<o:p></o:p>

The pelagic nitrogen cycle in a high CO2 world: What do we know so far?

Chair: Andrew McMinn

Nicola Wannicke (1) & Maren Voss (1)
1) Leibniz Institute for Baltic Sea Research (IOW), Department of Biological Oceanography, Seestrasse 15, D-18119 Rostock, Germany, Nicola.Wannicke@io-warnemuende.de

Background
The increase in atmospheric CO 2 has already caused significantly higher aquatic CO2 concentrations and lower pH values, changes which will continue over the next decades. Phytoplankton and other pelagic microbes will be widely affected (e.g. Liu et. al. 2010), and thus elemental cycles like the nitrogen cycle in the pelagial.

Methods
This review summarizes findings from six years research of the German BMBF funded project BIOACID with a focus on nitrogen fixation, combined with a literature survey of other nitrogen processes.

Findings
A strong stimulation of nitrogen fixation in tropical species like Trichodesmium and Crocosphaera has been reported (e.g. Levitan et. al. 2007, Hutchins et. al. 2013). However, for temperate brackish species like e.g. Nodularia and Dolichospermum either no significant effect was detected (Karlberg & Angela Wulff 2013, Brutemark et. al. 2015), or a stimulation during an exponential growth phase in the laboratory (Wannicke et. al. 2012) and even a negative impact (Czerny et. al. 2009). As an explanation for the observed differences, the availability of inorganic phosphorous and the physiological status of the bloom forming species will be discussed.

In contrast, nitrate assimilation seems not to be affected by elevated CO 2 (Clark et. al. 2014).

Nitrification on the other hand, appears to be more sensitive and decreasing at high CO 2 (Beman et. al. 2011). If true, the available form of dissolved nitrogen might be shifted from nitrate towards ammonium in the future ocean. Coastal sites, however, showed contrasting results with a high tolerance of nitrification against high CO2 concentrations (Fulweiler et. al. 2011). Potentially underlying reasons of these differences will be discussed.

Conclusions
For changes in the nitrogen cycle of the future ocean there are more conflicting than consistent results which we will try to consolidate.

CO2 Impacts to Copepod Populations Mediated by Changes in Prey Quality

Chair: Ana Queiros

Anna McLaskey (1)*, Katherina L. Schoo (2), Julie E. Keister (1), Brooke A. Love (2), M. Brady Olson (2)

1 University of Washington, School of Oceanography, Seattle, WA, 98105, USA
2 Western Washington University, Shannon Point Marine Center, Anacortes, WA, 98221, USA

Background
Most studies of elevated pCO2 have focused on single species, with few studies linking individuals across trophic levels, despite the importance of indirect effects in determining ultimate ecosystem outcomes. Copepods are an important link between primary production and higher trophic levels in marine ecosystems. Recent studies show that increased pCO2 can alter the physiology and biochemistry of some phytoplankton species, including fatty acids, an indicator of food quality that influences copepod reproductive outcomes. Changes to phytoplankton may be an important mechanism through which ocean acidification affects copepods.

Methods
We investigated impacts of elevated pCO2 on copepod populations mediated through changes in phytoplankton quality in the laboratory. Phytoplankton were grown under three different pCO2 conditions (400, 800, and 1200 μatm) for approximately five generations and fed to adult female copepods held at the same pCO2 level as their prey for 3-8 days. The biochemistry of the phytoplankton was analyzed, particularly for fatty acids. After acclimation we measured copepod grazing rates, respiration rates, egg production, hatching success, and larval development. Calanus pacificus, a large, high-lipid species, was fed the dinoflagellate Prorocentrum micans and the diatom Ditylum brightwellii, each at 12˚C. Acartia hudsonica, a smaller, low-lipid species, was fed Rhodomonas salina at 12˚C and 17˚C.

Findings
Although phytoplankton lipids increased at elevated pCO2, C. pacificus had significantly lower clutch sizes fed P. micans at 1200 compared to 400 μatm, with no effects on hatching or larval development. There were no effects on C. pacificus fed D. brightwellii. Preliminary results from A. hudsonica experiments indicate a trend towards slower larval development with elevated pCO2 at 12˚C and faster development with elevated pCO2 at 17˚C.

Conclusions
Prey quality is an important mechanism through which OA can impact marine ecosystems; understanding effects on the phytoplankton-copepod link will be critical to our knowledge of OA impacts.

Rapid ocean acidification in the Sub-Arctic Deep Sea and the Diversity of Benthic Molluscs

Chair: Victoria Cole

Hronn Egilsdottir(1,2), Jon Olafsson(1,2), Niall McGinty(3,4), Gudmundur Gudmundsson(5)

1 Institute of Earth Sciences, University of Iceland, Reykjavik, 101, Iceland
2 Marine Research Institute, Reykjavik, 121, Iceland
4 Mathematics and Computer Science, Mount Allison University, New Brunswick, Canada
5 Icelandic Institute of Natural History, Gardabaer, 212, Iceland

Background
Deep sea ocean acidification (OA) and the ecological consequences thereof have received little attention in the scientific literature to date. The main reason is the inaccessibility of the deep sea and the costs involved with sample collection. This is regrettable as deep sea organisms are predicted to have limited capacity for acclimatization. Molluscs are both common and functionally important in benthic ecosystems but also highly vulnerable to decreasing ocean pH and calcium carbonate saturation (ΩCaCO3). Studies on biodiversity patterns in relation regional hydrography are crucial for predicting future impacts of OA and warming.

Methods
The Greenland-Iceland-Scotland Ridge is a topographic barrier between the Arctic Iceland Sea and the Subpolar North Atlantic south of Iceland. We compare the temporal variation in hydrography and carbonate chemistry between these areas using data collected for over 30 years at two time series stations. We also compare the depth distribution, species richness and biodiversity of benthic molluscs in these areas by using data collected during the benthic sampling program BIOICE (1992 to 2004) which contained 1390 samples from 590 stations at depths ranging from 20-3000 meters around Iceland.

Findings
There is a strong contrast between the study areas in terms of temporal hydrographic variability with high rates of change observed in the Iceland Sea where the Ωaragonite=1.0, Ωaragonite=1.1 and Ωaragonite=1.2 horizons are shoaling at a rate of 6, 8 and 13 meters per year respectively. Species richness and diversity of bivalves and gastropods decreased more strongly with depth in the Iceland Sea compared to the area south of Iceland. We identify abundant taxa and relate to their life history and functional traits.

Conclusions
The findings of this study are discussed in the context of ecosystem resilience in the Arctic Nordic Seas and the rates of change observed throughout the water column in this region.

123456