Leaching material from Antarctic seaweeds and penguin guano affects cloud-relevant aerosol production.

Within the Southern Ocean, the greatest warming is occurring on the Antarctic Peninsula (AP) where clear cryospheric and biological consequences are being observed. Antarctic coastal systems harbour a high diversity of marine and terrestrial ecosystems heavily influenced by Antarctic seaweeds (benthonic macroalgae) and bird colonies (mainly penguins). Primary sea spray aerosols (SSA) formed by the outburst of bubbles via the sea-surface microlayer depend on the organic composition of the sea water surface. In order to gain insight into the influence of ocean biology and biogeochemistry on atmospheric aerosol, we performed in situ laboratory aerosol bubble chamber experiments to study the effect of different leachates of biogenic material - obtained from common Antarctic seaweeds as well as penguin guano - on primary SSA. The addition of different leachate materials on a seawater sample showed a dichotomous effect depending on the leachate material added - either suppressing (up to 52%) or enhancing (22-88%) aerosol particle production. We found high ice nucleating particle number concentrations resulting from addition of guano leachate material. Given the evolution of upper marine polar coastal ecosystems in the AP, further studies on ocean-atmosphere coupling are needed in order to represent the currently poorly understood climate feedback processes.

Assessing Viral Abundance and Community Composition in Four Contrasting Regions of the Southern Ocean.

We explored how changes of viral abundance and community composition among four contrasting regions in the Southern Ocean relied on physicochemical and microbiological traits. During January-February 2015, we visited areas north and south of the South Orkney Islands (NSO and SSO) characterized by low temperature and salinity and high inorganic nutrient concentration, north of South Georgia Island (NSG) and west of Anvers Island (WA), which have relatively higher temperatures and lower inorganic nutrient concentrations. Surface viral abundance (VA) was highest in NSG (21.50 ± 10.70 × 106 viruses mL-1) and lowest in SSO (2.96 ± 1.48 × 106 viruses mL-1). VA was positively correlated with temperature, prokaryote abundance and prokaryotic heterotrophic production, chlorophyll a, diatoms, haptophytes, fluorescent organic matter, and isoprene concentration, and was negatively correlated with inorganic nutrients (NO3-, SiO42-, PO43-), and dimethyl sulfide (DMS) concentrations. Viral communities determined by randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) were grouped according to the sampling location, being more similar within them than among regions. The first two axes of a canonical correspondence analysis, including physicochemical (temperature, salinity, inorganic nutrients-NO3-, SiO42-, and dimethyl sulfoniopropionate -DMSP- and isoprene concentrations) and microbiological (chlorophyll a, haptophytes and diatom, and prokaryote abundance and prokaryotic heterotrophic production) factors accounted for 62.9% of the variance. The first axis, temperature-related, accounted for 33.8%; the second one, salinity-related, accounted for 29.1%. Thus, different environmental situations likely select different hosts for viruses, leading to distinct viral communities.