Landscape changes on Deception Island’s coast after subglacial volcanic eruptions

M.C. Muniz1, R.M Anjos1, *, R.P. Cardoso1, L. H. Rosa2, R. Vieira1, H. Marotta1, K. Macario1, A. Ayres Neto1, C.D.N. Barboza1, A.S. Cid1, L.F. Rodrigues1

1LARA – Laboratório de Radioecologia, Instituto de Física, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, s/no, Gragoatá, 24210-340, Niterói, RJ, Brazil.

We have examined the radiocarbon ages, carbon and nitrogen isotopic compositions, and particle-size distributions in an ornithogenic soil profile from the Whalers Bay, Deception Island in Antarctica. In general, the textural characteristics of the sediment samples can be classified as muddy sand (very coarse silty very fine sand, poorly sorted). The δ13C values range from −24.8‰ to −23.0‰, showing that the predominant carbon source in Antarctic sediments is from terrestrial origin, such as mosses and lichens. The C/N ratio of the organic matter range of 5.2–8.6, consistent with the presence of penguin guano. The δ15N values range from 1.3‰ to 6.6‰, such that higher values (> 6) are observed in the topsoil and the layer of 27.5 ± 2.5 cm. However, the layers below them show a gradual decrease of δ15N. The chronology from bulk sediment samples indicate that the initial development of the organic matter began between 12500 and 11800 yr cal. BP. Additionally, the upper ground layers (between 2.5 ± 2.5 and 22.5 ± 2.5 cm depth) do not exhibit the age values monotonically increasing with depth. This behavior is only observed for layers below 27.5 ± 2.5cm depth, suggesting that the soil around this area can only be considered undisturbed below this sediment layer. Layers above this value are subjected to intense water erosion. Environment changes from the subglacial volcanic eruptions can be considered as an important factor not only for the understanding of its destruction power, but also about of the meltwater discharge effects on the autochthonous production imbalance and the erosion input from highest areas to the Antarctic coastal areas.

50. Ocean Acidification Effects on Productivity in a Coastal Antarctic Marine Microbial Community

Stacy L Deppeler (1)*, Karen Westwood (2,3), Imojen Pearce (2), Penelope Pascoe (2), Andrew T Davidson (2,3)

1 Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia
2 Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia
3 Antarctic Climate and Ecosystems Cooperative Research Centre, Private Bag 80, Hobart, Tasmania 7001, Australia


Background
The Southern Ocean is responsible for ~40% of the ocean’s uptake of anthropogenic CO2. Marine microbes (phytoplankton, protozoa and bacteria) are the base of the Antarctic food chain and critical determinants of the fixation and fate of carbon in the oceans. Few studies on ocean acidification have been performed in Antarctic waters and while its effect on marine microbes in this region are critical to ecosystem function they are poorly understood.

Methods
Six 650 L minicosm tanks were used to expose a natural community of Antarctic marine microbes from near-shore waters off Davis Station, Antarctica, to different CO2 concentrations ranging from ambient (343 ppm) to 1641 ppm. Primary and bacterial productivity was measured through the uptake of radioisotope labelled 14C-bicarbonate and 14C-Leucine, respectively, and normalised to cell abundance.

Findings
Results showed that rates of gross primary production decreased markedly with increasing CO2 concentration mainly due to the lower cell growth in the high CO2 treatments. The maximum photosynthetic rate (Pmax) and cell-specific productivity were similar across all treatments, suggesting that the cellular photosynthetic performance was not diminished by increased CO2. No marked difference was observed in rates of bacterial production amongst CO2 treatments. However, cell-specific rates of production increased substantially, despite the decline in abundance over time in all treatments.

Conclusions
This research helps establish critical thresholds of pCO2 that change microbial productivity in Antarctic waters and aids prediction of the future effects of anthropogenic CO2 on the Antarctic ecosystem.

51. Distribution of Pelagic Biogenic Carbonates in the Southern Ocean south of Australia: a Baseline for Ocean Acidification Impact Assessment

Abraham Passmore (1), Thomas W. Trull (1)*, Diana M. Davies (1), Tim Smit (1)

1. Antarctic Climate and Ecosystems CRC, CSIRO Oceans and Atmosphere, and University of Tasmania Institute of Marine and Antarctic Studies, Hobart, Tasmania, 7001, Australia

The Southern Ocean provides a vital service by absorbing about one sixth of humankind’s annual emissions of CO2. This comes with a cost – an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC) on particles filtered from surface seawater into two size fractions: 50-200 um to represent foraminifera (the most important biogenic carbonate forming zooplankton) and 1-50 um to represent coccolithophores (the most important biogenic carbonate forming phytoplankton). Ancillary measurements of biogenic silica (bSi) and particulate organic carbon (POC) provided context as estimates of the abundance of diatoms (the most abundant phytoplankton in polar waters), and total microbial biomass, respectively. Results along 9 transects from Australia to Antarctica in 2008-2015 showed low levels of all biogenic carbonate fractions compared to northern hemisphere polar waters. Levels were also ~5-fold lower than suggested by MODIS Aqua satellite remote sensing images. Coccolithophores exceeded the biomass of diatoms in Subantarctic waters, but their abundance decreased more than 10-fold southwards into Antarctic waters where diatoms dominated. Foram PIC contents were much lower, ~1/10 of coccolithophore levels, and also decreased southward. These decreases parallel the southward decrease in the saturation state of calcium carbonate in seawater, consistent with the theory that decreasing saturation restricts abundance and thus that advancing acidification will impact distributions. But other controls are also likely, and responses are likely to differ among different species. Expanded and more detailed surveys are required to better determine probable impacts.

45. Geographic variability in eco-physiological traits of benthic calcifiers along natural temperature and pH gradients: the Chilean coast as a natural laboratory

Nelson Lagos (1)*, Laura Ramajo (2) & Marco Lardies (3)

1 Centro de Investigación e Innovación para el Cambio Climático (CiiCC), Universidad Santo Tomás, Santiago, Chile
2 Centro para el estudio de forzantes multiples en sistemas socioecologicos (MUSELS), Universidad de Concepción, Chile
3 Departamento de Ciencias, Universidad Adolfo Ibañez, Santiago, Chile

Background
Chilean coast include a nested hierarchy of environmental processes modulating the abundance and distribution patterns of the benthic species. At biogeographycal scale there is an latitudinal gradient in sea surface temperature and pCO2 fluxes, and this gradient interact with the regional influence of upwelling and river discharge dynamics. In this study, we explore individual and population level responses of benthic calcifiers confronting this natural variability.

Methods
We use field survey along the Chilean coast and in situ reciprocal experiments to expose benthic calcifiers to natural changes in temperature and carbonate system parameters. We measured spatial variation in biomineralization, metabolism, abundance patterns in recruitment and carbonate production by benthic calcifiers (gastropods, mussels, barnacles).

Findings
Along the Chilean coast, we found changes in the proportion of calcium carbonate forms precipitated by the gastropods C. concholepas across their shells: the calcite:aragonite ratio in the pallial shell margin (i.e. newly deposited shell) increase significantly from northern to southern populations and this increase in calcite precipitation in the shell of juveniles snails was associated with a decrease in oxygen consumption rates in these populations. In the case of mussels, we determined that exposition to river–influenced conditions increased metabolic rates and reduced growth rates, as compared to mussels experiencing marine conditions. While the energy investment strategies of the two local populations resulted in similar net calcification rates, these rates decreased significantly when mussels were transplanted to the river- influenced site. Stressful conditions at the river-influenced site were reflected evidenced by decreased survivorship across treatments. Freshwater inputs modify the organic composition of shell periostracum through a significant reduction in polysaccharides. Spatial variation in barnacles metabolism showed non–clinal plasticity in the thermal reaction norm along the latitudinal gradient of the Chilean coast and suggest a biogeographic–scale dependence of the thermal sensitivity in the metabolism of the studied populations.

Conclusions
Our result suggests that along the Chilean coast calcite secretion may be favoured when metabolic rates of C. concholepas are lowered, as this carbonate mineral phase might be less energetically costly for the organism to precipitate. In the case of mussels, although our field experiment did not identify specific environmental factors underlying these biological differences, the observed phenotypic changes imply that plasticity plays a strong role when P. purpuratus are exposed to river–induced environmental variability in their habitats, and suggests that the lack of this exposure may promote less tolerant mussels with potential for local adaptation. Barnacles showed evidenced plasticity in metabolism and intra-population variability in thermal responses, with a strong role of thermal safety margins in determining the extent of these population differences.

48. New volcanic CO2 vents along the coast off the Ischia Island (Italy) provide a glimpse of the potential impacts of ocean acidification

Teixidó Núria (1), Enric Ballesteros (2), Kristy Kroeker (3)*, Fiorenza Micheli (4), Maria Cristina Gambi (1)

1 Stazione Zoologica Anton Dohrn, Naples, Italy, 80077, Italy
2 Center for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Spain, 17300, Spain
3 University California of Santa Cruz, Santa Cruz, USA, 95064, USA
4 Stanford University, Pacific Grove, USA, 93950, USA

Ocean acidification (OA), a suite of changes in seawater chemistry associated with increased CO2 concentrations in the atmosphere, is expected to profoundly alter the diversity and function of marine ecosystems. In recent years, studies using a shallow volcanic CO2 vent system near the Castello Aragonese on the island of Ischia (Italy) have generated key insights on the direct and indirect effects of OA on the surrounding ecosystems. These natural CO2 vents locally acidify the seawater by as much as 1.5 pH units below the average ocean pH of 8.1-8.2. Corresponding to this pH drop, the diversity and biomass of marine organisms decrease. Here, we present newly discovered vents along the coast of Ischia across depths of 3-48 m. These sites span a variety of different habitats such as Posidonia oceanica seagrass meadows, gravel and sandy bottoms, semi-dark cave habitats and coralligenous outcrops, the latter dominated by calcifying organisms that are particularly vulnerable to OA. These habitats are hotspots of Mediterranean marine biodiversity, but it is unknown how they will be affected by OA. We are carrying out SCUBA diving surveys to characterize the water chemistry and pH and to quantitatively assess seafloor community among pH zones at each of the vents as well as nearby reference areas with normal pH. This study provides new insights regarding OA’s effects on a range of community types, thereby enabling generality in our predictions of OA’s impacts. These new vents place Ischia at the forefront of natural laboratories for OA studies, as the only locations known to date where CO2 vents span a variety of habitat types, allowing us to investigate and report how a suite of ecosystem types responds to acidification.

47. Life-long in situ exposure to ocean acidification reduces heterotrophy in the stony coral Galaxea fascicularis

Joy N. Smith (1,2)*, Julia Strahl (2), Sam H.C. Noonan (2), Gertraud M. Schmidt (1), Claudio Richter (1), Katharina E. Fabricius (2)

1 Alfred Wegener Institute, Bremerhaven, D-27568, Germany
2 Australian Institute of Marine Science, Townsville, Queensland, 4810, Australia

Background
Coral heterotrophy provides essential nutrients (nitrogen and phosphorus) for biological processes. For some corals species, this feeding mode becomes increasingly important when stressed from bleaching, high turbidity, and sometimes even ocean acidification. We investigated rates of heterotrophy in a voracious zooplankton consumer, Galaxea fascicularis, after life-long in situ exposure to elevated levels of CO2.

Methods
We conducted complementary field and laboratory feeding experiments on corals that have lived their entire lives under CO2 stress. Colonies of G. fascicularis were studied on a fringing reef in Papua New Guinea where underwater volcanic seeps naturally elevate seawater pCO2. Colony fragments in the field and laboratory were fed a known amount of zooplankton and allowed to feed for one hour before being preserved in 4% formalin for later determination of gut contents. Field and laboratory experiments were repeated for two expeditions. Additional laboratory experiments were conducted to determine if changes in feeding rates might be caused by an interference of the neurotransmitter functioning of the receptor GABAA.

Findings
Results from both excursions and both methods indicate that G. fascicularis colonies eat 2.8 to 4.8 times more zooplankton under normal seawater conditions compared to corals under CO2 stress. Reduced heterotrophy was not caused by any differences in polyp expansion or polyp size since both parameters remained similar across the CO2 gradient. Furthermore, heterotrophy rates were not restored with the addition of gabazine, the GABAA receptor antagonist.

Conclusions
Although increased heterotrophy may help to alleviate the harmful effects of ocean acidification, G. fascicularis consumed less zooplankton after life-long exposure to CO2 stress despite having an equal opportunity to catch food particles (same quantity of food fed to them, similar polyp extension, same polyp size). Reduced heterotrophy will likely have grave consequences for the metabolic processes that require essential nutrients acquired by consuming zooplankton.

46. Diurnal and seasonal variations of pH in Oshoro Bay, Hokkaido, Japan

Shintaro Takao (1)*, Masahiko Fujii (1)

1 Hokkaido University, Sapporo, Hokkaido, 0600810, Japan

Coastal marine organisms have already been experiencing low pH environment (< 7.9) that is not predicted to occur until 2100 in open ocean systems. To properly assess the impacts of ocean acidification on them inhabiting wide ranges of diurnal variation of pH, we need to conduct long-term, high-frequency monitoring measurements of environmental parameters. To investigate diurnal and seasonal variations of pH in a subarctic region, we have conducted monitoring measurements of seawater pH, temperature, and salinity in Oshoro Bay, Hokkaido, Japan since 2013. Large seasonal variation of pH was found based on seawater sample analysis. Annually maximum pH value (8.35) was observed in April, which is consistent with timing of seaweed growth. On the other hand, annually minimum pH value (8.05) appeared in July, consistent with timing of strong grazing by sea urchins. Maximum and minimum of hourly pH value obtained by a pH sensor during the monitoring period were 8.40 and 7.33, respectively, high in the daytime and low in the night time, in all monitoring periods. Therefore, the fluctuation was relatively larger in hourly pH value (1.07) than in seasonal pH value (0.30). These results indicate that marine organisms in the bay have already experienced extremely low pH conditions that may appear more commonly in the high CO2 world.

44. Epifaunal invertebrate community variation along a salinity-acidity gradient in a tropical estuary

M. Belal Hossain* and David J. Marshall

Environmental and Life Sciences, Faculty of Science, Universiti Brunei Darussalam, Jalan Tunkgu Link Brunei Darussalam, BE1410. Email: mbhnstu@gmail.com

The invertebrate communities associated with hard substrata in estuaries are generally underexplored, despite the prevalence of such substrata. We studied the variation in species composition, abundance and community structure of intertidal epifaunal invertebrates associated with a ‘rocky’ (barnacle-dominated) community along a salinity and pH gradient in a tropical South East Asian estuary (Brunei Darussalam, Borneo). Species richness, species diversity and abundance were concomitantly greatest at the most seaward station (relatively high pH and salinity), lowest at the middle stations and relatively high again at the most landward (low pH and salinity) of the Sungai Brunei estuary. A total of 34 species (taxa) occurred in 72 samples collected from four stations, and sample abundances for all species together ranged between 94.5 to 335.67 individuals per 100cm2. An abundance analysis at a coarse taxonomic level (class/order) suggested the existence of three distinct communities along the physicochemical gradient; the community varied from a tanaid-polychaete dominated one to a mussel-dipteran one, and then a mussel-amphipod-dipteran one, from the landward to the seaward stations. However, the community structure at the most seaward station was influenced by the abundance there being more than twofold that of the other stations. The pattern of three distinct communities was somewhat confirmed by a multivariate analysis (Bray-Curtis similarity and nMDS). The shift from amphipod dominance to polychaete dominance with increasing acidification is consistent with observations of other studies for non-estuarine coastal systems. In addition to presenting the first known description of community structure variation for hard substratum invertebrates along an acidification gradient in an old world tropical estuary, the present study also hints at the potential for using estuarine systems to understand community-level effects of marine acidification in general.

43. Effects of river streamflow on summer-winter dynamics of pH/pCO2 in a Patagonia highly stratified fjord

José L. Iriarte (1,2)*, Michael DeGrandpre (3), Maximiliano Vergara (4), Cory Beatty (3), Rodrigo Torres (5,1), Luis A. Cuevas (6)

1 IDEAL, Universidad Austral de Chile and Instituo de Acuicultura, 5501558, Puerto Montt, Chile.
2 COPAS-Sur Austral, Universidad de Concepción, Concepción, Chile
3 Department of Chemistry & Biochemistry, University of Montana, Missoula, USA.
4 Programa de Doctorado en Ciencias de la Acuicultura, Universidad Austral de Chile, 5501558, Puerto Montt, Chile.
5 CIEP, Coyhaique, Chile.
6 Facultad de Ciencias Ambientales, Universidad de Concepción, Concepción, Chile

Background
Patagonian fjords are characterized by subantarctic surface water receiving high volume of freshwater (rivers, glaciers). The interplay between continental and marine influences affect the chemical stoichiometry, organic matter input and finally affect the plankton community in an “uncertain way” that make a difficult task the modelling efforts. In addition, fjords, will face major changes in the carbonate chemistry speciation which most probably will trigger changes in carbon budgets, impacting primary productivity and the entire biogeochemistry of this cold and rainy region.

Methods
In order to investigate the summer-winter pH/pCO2 dynamics related to freshwater streamflow, we analysed high temporal resolution observations of in situ pH and pCO2 (SAMI, at 3.5 m), river streamflow and bimonthly sampling of pH, total alkalinity (AT) at the middle section of Reloncaví fjord between January to July 2015.

Findings
Strong summer-winter variability showed that the influence of freshwater layer affected the pCO2 and pH dynamics in the fjord surface water. During summer months, data showed the lowest pCO2 (mean=200 μatm) and highest pH values (8.0 – 8.2), coincident with the lowest freshwater inputs. In contrast, we observed that increased winter freshwater inputs decreased pH (down to 7.6), AT (<1000 μmol kg-1), and increased pCO2 (mean=1000 μatm). The surface water shows a winter undersaturation of Aragonite (Ω < 1), contrasting with oversaturated levels of warmer waters of spring-summer period.

Conclusions
The summer-winter variability showed that freshwater streamflow affected the chemical features of the fjord, suggesting that increased winter freshwater inputs plays a role enhancing the shift from CO2 sink in summer (high community net production, higher temperature and higher buffer capacity) to a CO2 source in winter (high community respiration, lower temperature, lower buffer capacity). Furthermore, the system change from a supersaturated state in summer (Ω >1) to “corrosive waters” for Aragonite during winter (Ω <1).

52. Effect of elevated CO2 and nutrients on phytoplankton community structure during spring in the Western English Channel

Matthew Keys (1,2)*, Gavin Tilstone (1), Helen Findlay (1), Karen Tait (1), Tracy Lawson (2).

1 Plymouth Marine Laboratory, Plymouth, Devon, PL1 3DH, United Kingdom.
2 University of Essex, Colchester, Essex, CO4 3SQ, United Kingdom.

Background
Coastal zones support 10-15% of the global ocean net annual primary production and >40% of its carbon sequestration. Elevated CO2 affects the growth rate and biomass of many marine phytoplankton species, though the majority of studies have been conducted on species in culture and there have been comparatively fewer studies conducted on natural populations.

Phytoplankton taxonomy and community structure in the Western English Channel (WEC) has been analysed since 1992 at the WEC time-series (50° 15’N, 4° 13’W) and has shown significant decline in diatoms and Phaeocystis, whereas coccolithophorids and dinoflagellates have increased.

Methods
A fifteen day experiment was conducted on the natural phytoplankton community from the WEC time-series in April 2015, maintained at ambient pCO2 (~380 µatm) and elevated pCO2 (1000 µatm) plus nutrients amended to 8µM nitrate+nitrite and 0.5 µM phosphate in a closed semi-continuous incubation system.

Findings
Total phytoplankton community biomass increased significantly by 50% to ~225 µg C L-1 in the high CO2 treatment. Phaeocystis globosa exhibited a significant response to elevated CO2, increasing from ~60 µg C L-1 to ~185 µg C L-1 and constituted 80% of the total biomass. In the short term, the biomass of chain forming and pennate diatoms increased significantly in the high CO2 treatment, but then declined after 7 days.

Conclusions
P. globosa is an indicator species of water disturbance resulting from eutrophication. OSPAR recommend that waters of good ecological status have low abundance of P. globosa. This study suggests that future CO2 concentrations in the WEC could favour P. globosa, possibly tipping the balance towards poor ecological status in these waters.

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