Particle export during the Southern Ocean Iron Experiment (SOFeX)

Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of American Society of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 50 (2005): 311-327, doi:10.4319/lo.2005.50.1.0311.We studied the effect of iron addition on particle export in the Southern Ocean by measuring changes in the distribution of thorium-234 during a 4 week Fe enrichment experiment conducted in the high-silicate high-nitrate waters just south of the Southern Antarctic Circumpolar Current Front at 172.5°W. Decreases in 234Th activity with time in the fertilized mixed layer (0-50m) exceeded those in unfertilized waters, indicating enhanced export of 234Th on sinking particles after Fe enrichment. The addition of Fe also affected export below the fertilized patch by increasing the efficiency of particle export through the 100 m depth horizon. Extensive temporal and vertical Lagrangian sampling allowed us to make a detailed examination of the 234Th flux model, which was used to quantify the fluxes of particulate organic carbon (POC) and biogenic silica (bSiO2). Iron addition increased the flux of both POC and bSiO2 out of the mixed layer by about 300%. The flux at 100 m increased by more than 700% and 600% for POC and bSiO2, respectively. The absolute magnitude of the POC and bSiO2 fluxes were not large relative to natural blooms at these latitudes, or to those found in association with the termination of blooms in other ocean regions. Our results support the hypothesis that Fe addition leads directly to significant particle export and sequestration of C in the deep ocean. This is a key link between ocean Fe inputs and past changes in atmospheric CO2 and climate.This work was supported by the Division of Ocean Sciences at the U.S. National Science Foundation, the Biological and Environmental Research Office, Office of Science, U.S. Department of Energy, and for RIB Polar Star logistical support, Polar Programs at the U.S. National Science Foundation

Keeping the brown marmorated stink bug out of New Zealand

Halyomorpha halys, commonly known as the brown marmorated stink bug (BMSB), is a severe crop and fruit pest that originated from Eastern Asia. In the mid-1990s an invasion of BMSB was detected in Pennsylvania USA. The species is highly polyphagous. Within its native range, there are reports of occasional losses of fruit crops including apple, peach, pear and persimmon. In 2010, populations in the USA hit a record high, and commercial fruit orchards incurred substantial losses. Generally, orchard plots most at risk are those bordered by a forest, as the BMSB tends to move regularly between shelter areas (in the forest) and feeding areas in orchards. Due to this behaviour, the worst BMSB damage is found at the edges of orchards bordered by forests or hedge rows. However, during population outbreaks, high levels of damage can occur orchard-wide. Another concern is that BMSB is a vector of a phytoplasma that causes witches’ broom in Paulownia trees, a favourite host tree

Identification of volatiles released by diapausing brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae)

The brown marmorated stink bug, Halyomorpha halys, is an agricultural and urban pest that has become widely established as an invasive species of major concern in the USA and across Europe. This species forms large aggregations when entering diapause, and it is often these aggregations that are found by officials conducting inspections of internationally shipped freight. Identifying the presence of diapausing aggregations of H. halys using their emissions of volatile organic compounds (VOCs) may be a potential means for detecting and intercepting them during international freight inspections. Headspace samples were collected from aggregations of diapausing H. halys using volatile collection traps (VCTs) and solid phase microextraction. The only compound detected in all samples was tridecane, with small amounts of (E)-2-decenal found in most samples. We also monitored the release of defensive odors, following mechanical agitation of diapausing and diapause-disrupted adult H. halys. Diapausing groups were significantly more likely to release defensive odors than diapause-disrupted groups. The predominant compounds consistently found from both groups were tridecane, (E)-2-decenal, and 4-oxo-(E)-2-hexenal, with a small abundance of dodecane. Our findings show that diapausing H. halys do release defensive compounds, and suggest that volatile sampling may be feasible to detect H. halys in freight.Contributions by L.J.N. and E.G.B. were supported by the New Zealand government via Ministry of Business, Innovation, and Employment core funding to Plant and Food Research and Scion (contract C04X1104), respectively, and the BetterBorder Biosecurity Collaboration (www.b3nz.org)

Iron and mixing affect biological carbon uptake in SOIREE and EisenEx, two Southern Ocean iron fertilisation experiments

This study explores the changes in the surface water fugacity of carbon dioxide (fCO2) and biological carbon uptake in two Southern Ocean iron fertilisation experiments with different hydrographic regimes. The Southern Ocean Iron Release Experiment (SOIREE) experiment was carried out south of the Antarctic Polar Front (APF) at 61°S, 141°E in February 1999 in a stable hydrographic setting. The EisenEx experiment was conducted in a cyclonic eddy north of the APF at 48°S, 21°E in November 2000 and was characterised by a rapid succession of low to storm-force wind speeds and dynamic hydrographic conditions. The iron additions promoted algal blooms in both studies. They alleviated algal iron limitation during the 13-day SOIREE experiment and probably during the first 12 days of EisenEx. The fCO2 in surface water decreased at a constant rate of 3.8 µatm day-1 from 4 to 5 days onwards in SOIREE. The fCO2 reduction was 35 µatm after 13 days. The evolution of surface water fCO2 in the iron-enriched waters (or ‘patch’) displayed a saw tooth pattern in EisenEx, in response to algal carbon uptake in calm conditions and deep mixing and horizontal dispersion during storms. The maximum fCO2 reduction was 18–20 µatm after 12 and 21 days with lower values in between. The iron-enriched waters in EisenEx absorbed four times more atmospheric CO2 than in SOIREE between 5 and 12 days, as a result of stronger winds. The total biological uptake of inorganic carbon across the patch was 1389 ton C (±10%) in SOIREE and 1433 ton C (±27%) in EisenEx after 12 days (1 ton = 10^6 g). This similarity probably reflects the comparable size of the iron additions, as well as algal growth at a similar near-maximum growth rate in these regions. The findings imply that the different mixing regimes had less effect on the overall biological carbon uptake across the iron-enriched waters than suggested by the evolution of fCO2 in surface water.

Physical exchanges at the air-sea interface: UK-SOLAS Field Measurements

As part of the U.K. contribution to the international Surface Ocean–Lower Atmosphere Study, a series of three related projects—DOGEE, SEASAW, and HiWASE—undertook experimental studies of the processes controlling the physical exchange of gases and sea spray aerosol at the sea surface. The studies share a common goal: to reduce the high degree of uncertainty in current parameterization schemes. The wide variety of measurements made during the studies, which incorporated tracer and surfactant release experiments, included direct eddy correlation fluxes, detailed wave spectra, wind history, photographic retrievals of whitecap fraction, aerosol-size spectra and composition, surfactant concentration, and bubble populations in the ocean mixed layer. Measurements were made during three cruises in the northeast Atlantic on the RRS Discovery during 2006 and 2007; a fourth campaign has been making continuous measurements on the Norwegian weather ship Polarfront since September 2006. This paper provides an overview of the three projects and some of the highlights of the measurement campaigns

Supplement to physical exchanges at the air-sea interface: UK-SOLAS Field Measurements

Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 90 (2009): ES9-ES16, doi:10.1175/2008BAMS2578.2