Graham B Jones

Effects of carp, gambusia, and Australian bass on water quality in a subtropical freshwater reservoir

Darren Akhurst et al. — Tue, 19 Mar 2013 19:35:59 PDT

Freshwater systems are frequently compromised by excessive macrophyte biomass and cyanobacterial blooms associated with eutrophication and possibly exotic fish. The effects of piscivorous Australian bass (Macquaria novemaculeata), planktivorous gambusia (Gambusia holbrooki [Girard]), and benthivorous carp (Cyprinus carpio L) on water quality in Emigrant Creek Dam (ECD), Australia, were studied in 20 experimental enclosures (depth 1 m, volume 3.2 m³), stocked at a density of 1875 kg/ha. Fish additions had immediate effects on water quality, except for bass, which merely recycled preexisting water column nutrients. Water turbidity, total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP) concentrations, and chlorophyll a (Chl-a), were all significantly higher in gambusia, but more so in carp enclosures. Assuming a linear relationship, mean daily Chl-a increases in carp enclosures were 4.6 μg/L/100 kg carp/ha. Moreover, Chl-a (>90 μg/L) was positively correlated with TP (r² = 0.91), TN (r² = 0.89), TFe (r² = 0.96), and TMn (r² = 0.83) in carp enclosures; however, Fe and Mn resuspension from sediments does not seem to be a principal mechanism affecting total phytoplankton biomass. Macrophyte, epiphyte, and periphyton biomass were also significantly lower in carp enclosures, a consequence of sediment and nutrient resuspension, dietary excretion, and macrophyte damage. In the absence of carp, epiphytes, periphyton, and macrophytes competed with phytoplankton for available nutrients, providing a critical stabilizing role. Exotic fish removal may prove to be an effective management tool in subtropical systems to maintain high water quality.

Atmospheric dimethysulphide production from corals in the Great Barrier Reef and links to solar radiation, climate and coral bleaching

Esther Fischer et al. — Wed, 23 Jan 2013 18:26:03 PST

Coral zooxanthellae contain high concentrations of dimethylsulphoniopropionate (DMSP), the precursor of dimethylsulphide (DMS), an aerosol substance that could affect cloud cover, solar radiation and ocean temperatures. Acropora intermedia a dominant staghorn coral in the Indo-Pacific region, contain some of the highest concentrations of DMSP reported in the literature but no studies have shown that corals produce atmospheric DMS in situ and thus could potentially participate in sea surface temperature (SST) regulation over reefs; or how production varies during coral bleaching. We show that A. intermedia from the Great Barrier Reef (GBR) produces significant amounts of atmospheric DMS, in chamber experiments, indicating that coral reefs in this region could contribute to an ‘‘ocean thermostat’’ similar to that described for the western Pacific warm pool, where significantly fewer coral reefs have bleached during the last 25 years because of a cloud-SST feedback. However, when Acropora intermedia was stressed with higher light levels and seawater temperatures DMSP production, an indicator of zooxanthellae expulsion, increased markedly in the chamber, whilst atmospheric DMS emissions almost completely shut down. These results suggest that during increased light levels and seawater temperatures in the GBR coral shut-down atmospheric DMS aerosol production, potentially increasing solar radiation levels over reefs and exacerbating coral bleaching.

DMS flux over the Antarctic sea ice zone

Anne Trevena et al. — Wed, 23 Jan 2013 18:26:01 PST

This study presents concentrations of dimethylsulphide (DMS) and its precursor compound dimethylsulphoniopropionate (DMSP), and chlorophyll a in a variety of sea ice and seawater habitats from pack and fast ice in the Antarctic Sea Ice Zone (ASIZ) of the Prydz Bay-Davis-Casey region of eastern Antarctica during spring and summer. These results were used to calculate the DMS flux from ice-free ocean water and melting sea ice in this region. Estimated seawater DMS concentrations derived from sea ice DMSPt released during ice melting showed that in October, sea ice derived DMS of the order of 20-50 nM is associated with DMSPt released from melting sea ice of 0.4 m thickness. In November and December, melting of large areas of ice less than 0.6 m thick could release larger amounts of DMS around 50-80 nM and 150-270 nM, respectively. In addition, DMSPt released from 1.0-1.2 m thick ice in December could result in "hot spot" concentrations of DMS of around 100 nM. DMS fluxes measured mainly in the Prydz Bay-Davis region in November and mid to late December were highest in pack ice > fast ice > ice edge (pack ice = 54 μmol m-2 d-1; range 1-325); fast ice = 28 μmol m-2 d-1; range 0-168); ice edge = 12 and 23 μmol m-2 d-1; range 1.2-26). In ice-free seawater in the Davis area from January to February, although dissolved DMS concentrations were low, DMS fluxes were high due to high wind speeds (DMS = 3 nM; DMS flux = 27 μmol m-2 d-1umol; range 1-101). DMS concentrations and flux from a fast ice tide crack (DMS = 12 nM; DMS flux 6-81 μmol m-2 d-1), and from the Davis region 2 days following fast ice breakout (DMS 12 nM; DMS flux 45-84 μmol m-2 d-1) were also a significant source of DMS to the atmosphere of this region. In contrast DMS and DMS flux from a fast ice melt-pool was low (DMS = 1 nM; DMS flux 0.5-7 μmol m-2 d-1). These measurements support the suggestion that during sea ice melting during late spring to early summer (November - December), the ASIZ is an area of high DMS (P) production, leading to very high fluxes of DMS to the atmosphere of this region. What effect this huge pulse of atmospheric DMS has on the radiative climate of this region is unknown.

Can corals form aerosol particles through volatile sulphur compound emissions?

Elisabeth Deschaseaux et al. — Wed, 23 Jan 2013 18:26:00 PST

Acropora dominated coral reefs are a substantial source of atmospheric dimethylsulphide (DMSa), one of the most abundant reduced sulphur gases present in the marine boundary layer. DMS is believed to act as a climate regulator of solar radiation and sea surface temperatures through the formation of non-sea-salt sulphate aerosols and cloud condensation nuclei (CCN), although this regulation has not yet been demonstrated. A bubbling chamber experiment was conducted on coral reef seawater containing a branch of Acropora pulchra, to investigate whether the coral-generated DMSa could be oxidised to non-seasalt sulphate aerosols under treatment with UV light and O3. Results indicated that A. pulchra produced significant amounts of dimethylsulphoniopropionate (DMSP) and dissolved DMS although emissions of DMSa in the chamber headspace were reduced by the presence of the coral, probably as a result of antioxidant activity in the coral tissue. Significant amounts of carbon disulphide (CS2) and ethanethiol (ESH), other sulphur gases that could be involved in CCN formation, were also indicated in the bubbling chamber, most likely from coral production. A decrease in DMSa and CS2 in the presence of UV light and O3 followed by an occurrence of freshly nucleated nanoparticles (<10nm) suggested that these two sulphur compounds were oxidised and potentially participated in aerosol particle formation and thus could be involved in CCN formation and possibly climate regulation. The study provided insights into the production of sulphur compounds by Acropora dominated coral reefs with potential impact on local climate.

Dimethylsulfide, climate and coral reef ecosystems

Hilton B. Swan et al. — Wed, 23 Jan 2013 18:25:59 PST

Dimethylsulfide (DMS) is the major biogenic source of atmospheric sulfur and is mainly derived from dimethylsulfoniopropionate (DMSP) produced by oceanic phytoplankton, marine algae and endosymbiont zooxanthellae in reef-building corals. Although coral reefs occupy <1% of the global oceans, the potential source strength of DMS from these areas was found to be significant in comparison to other oceanic areas. In this study, healthy nubbins of Acropora valida and Acropora pulchra collected at Heron Island were examined to assess the source strength of DMS from these common coral species. Total DMS (free DMS and DMSPderived DMS) measured in these corals was on average 3.6 μmol cm-2 surface area. Sediment from the coral reef flat was found to release ~1000 times less DMS than the Acropora corals when compared by weight. Megatonnes of DMS are released from the oceans to the atmosphere annually, where it is oxidised to contribute to new nanoparticles that can lead to cloud condensation nuclei (CCN). These affect cloud microphysical properties and consequently the Earth’s radiation budget and climate. The results suggest emissions of DMS from coral reefs are significant and may affect regional climate. Notably strong DMS plumes of up to 13 nmol m-3 of air were detected above the coral reef flat during low tide when it was exposed at the end of the day under calm conditions. A seasonal comparison of atmospheric DMS concentrations determined at Heron Island with a temperate marine location showed the reef to be a greater source of DMS.

Elemental speciation and distribution in sediments of a eutrophied subtropical freshwater reservoir using post extraction normalisation

Darren J. Akhurst et al. — Wed, 23 Jan 2013 18:25:57 PST

The speciation and distribution of trace and major elements (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, P, Pb and Zn) in the sediments of Emigrant Creek Dam (ECD), New South Wales Australia were investigated using sequential extraction, postextraction normalisation and spatial mapping to indicate source and dispersion patterns. Subsurface coring provided an estimate of elemental enrichment and showed that As 1.9 > P 1.7 > N 1.5 ≈ Cd 1.5 > Mn 1.3 were enriched. Moreover, a high proportion of the enriched elements (mean 57, 34, 47 and 87 % for As, P, Cd and Mn, respectively) were assessed as being bioavailable. Comparisons with ISQGs found that sediments from sites in proximity to Emigrant Creek inflows had the highest accumulations of metals and the greatest potential for causing biological harm. Spatially, contaminants accumulate in ECD sediments adjacent to anthropogenic sources including a cattle dip site, dredged sediment and macrophyte dump areas, and agricultural/residential runoff. Moreover, the integrated technique and postextraction normalisation allow assessment of texturally diverse and difficult sediments.

Preliminary carbon sequestration modelling for the Australian macadamia industry

Tim Murphy et al. — Wed, 23 Jan 2013 18:25:55 PST

There is a need to accurately estimate the carbon sequestration potential of many of our agricultural and horticultural industries now that the Australian Government has introduced the Carbon Farming Initiative and is planning to introduce an emissions trading scheme in 2015. This study estimates that the carbon sequestration of macadamia plantations is around 3t CO2e/ha/yr, and provides a methodology to assess the carbon footprint of the Australian Macadamia Industry. This study attempts to estimate the growth rate, and subsequently the sequestration rate of plantation grown Macadamia spp. through regression analysis of stem characteristics of destructively sampled Macadamia integrifolia var. 344. A volume increment curve was also derived using three common genetic varieties (A4, A16 & A42). This curve is used to extrapolate a carbon sequestration rate for the national macadamia plantation estate. Once volume estimates and sequestration rates are determined, an economic benefit of the carbon sequestration can be estimated by auditing the amount of carbon produced by activities such as ‘‘on farm’’ fuel use, fuel used in transport, and energy used in producing the product. In this way, a life cycle carbon budget can be developed that will aid the sustainable development of the macadamia and horticultural industries in Australia through the production of carbon credits from the carbon stored in the trees.

Grain size normalization: a case for post extraction normalization and inclusion of selective extraction procedures

Darren J. Akhurst et al. — Tue, 11 Dec 2012 18:26:08 PST

The spatial mapping of trace metal and/or nutrient elemental concentrations in surface is often aided by normalization approaches that allow comparison of texturally, geochemically, and mineralogically dissimilar sites. Frequently, this is a grain-size normalization at < 62.5 μm before chemical analysis. However, material that is >62.5 μm (generally geochemically inert) may have fine-grained coatings that bind components of interest and/or may consist of aggregates of fine-grained sediment. The misplacement of these essential components within the coarse fraction of size-normalized sediments may skew data and subsequent geochemical interpretations, especially when these components make up a substantial proportion of the sediment metal and/or nutrient binding capacity. In this article, sedimentary contaminant data were normalized using size normalization (wet sieving < 62.5 μm) and a post-extraction normalization (PEN). PEN is a size-based normalization procedure devised to minimize the misplacement of fine-grained coatings/aggregates by applying a size and mineralogical normalization to inert digestion residuals, post-chemical extraction. The data show that PEN provides a more ecologically and diagenetically interpretable representation of partitioning of elements between sediments in a freshwater reservoir. In addition, PEN samples are more rapidly collected, and consequently, PEN provides a cheaper alternative to traditional size normalization. In addition, application of the PEN allows the collection of data not only relevant to ecological health, but also relevant sedimentary diagenetic mobility data using a single sediment sample.

The SOLAS air-sea gas exchange experiment (SAGE) 2004

Mike J. Harvey et al. — Tue, 11 Dec 2012 18:26:06 PST

The SOLAS air–sea gas exchange experiment (SAGE) was a multiple-objective study investigating gas-transfer processes and the influence of iron fertilisation on biologically driven gas exchange in high-nitrate low-silicic acid low-chlorophyll (HNLSiLC) Sub-Antarctic waters characteristic of the expansive subpolar zone of the southern oceans. This paper provides a general introduction and summary of the main experimental findings. The release site was selected from a pre-voyage desktop study of environmental parameters to be in the south-west Bounty Trough (46.5ï¿½S 172.5ï¿½E) to the south-east of New Zealand and the experiment was conducted between mid-March and mid-April 2004. In common with other mesoscale iron addition experiments (FeAX’s), SAGE was designed as a Lagrangian study, quantifying key biological and physical drivers influencing the air–sea gas exchange processes of CO

Reef emissions affect climate

Graham B. Jones et al. — Wed, 26 May 2010 17:00:36 PDT

Coral reefs produce a natural aerosol that creates clouds over the ocean and keeps sea surface temperatures stable – with implications for both reefs and rainforests.

Nutrient input in Cleveland Bay

Graham B. Jones — Wed, 26 May 2010 15:51:30 PDT

Water quality: compliance assessment

Graham B. Jones — Wed, 26 May 2010 15:48:56 PDT

The effect of Trichodesmium blooms on water quality in the Great Barrier Reef Lagoon

Graham B. Jones — Wed, 26 May 2010 15:48:56 PDT

Chemical contaminants in Cleveland Bay: water quality and ecotoxicological issues

Graham B. Jones et al. — Wed, 26 May 2010 15:33:09 PDT

A global database of sea surface dimethylsulfide (DMS) measurements and a procedure to predict sea surface DMS as a function of latitude, longitude, and month

A J. Kettle et al. — Wed, 26 May 2010 15:02:35 PDT

A database of 15,617 point measurements of dimethylsulfide (DMS) in surface waters along with lesser amounts of data for aqueous and particulate dimethylsulfoniopropionate concentration, chlorophyll concentration, sea surface salinity and temperature, and wind speed has been assembled. The database was processed to create a series of climatological annual and monthly l°×l° latitude-longitude squares of data. The results were compared to published fields of geophysical and biological parameters. No significant correlation was found between DMS and these parameters, and no simple algorithm could be found to create monthly fields of sea surface DMS concentration based on these parameters. Instead, an annual map of sea surface DMS was produced using an algorithm similar to that employed by Conkright et al. [1994]. In this approach, a first-guess field of DMS sea surface concentration measurements is created and then a correction to this field is generated based on actual measurements. Monthly sea surface grids of DMS were obtained using a similar scheme, but the sparsity of DMS measurements made the method difficult to implement. A scheme was used which projected actual data into months of the year where no data were otherwise present.

Chemical and microbiological aspects of acoustically turbid sediments: preliminary investigations

Graham B. Jones et al. — Wed, 26 May 2010 15:02:34 PDT

Investigations of the speciation of phosphorus in coastal and estuarine waters of the great barrier reef, using iron strips and colorimetry

R K. Chiswell et al. — Wed, 26 May 2010 15:02:33 PDT

A new method of determining phosphorus in sea water, using iron-impregnated strips of filter paper, was investigated and compared with standard colorimetric methods of phosphorus analysis. Laboratory experiments were undertaken to determine the number of iron strips required to extract phosphorus from sea water, the length of time a strip needed to adsorb all P from solution, the reproducibility of the method, and whether the strips could measure P adsorbed to different particles. Field studies were carried out with iron strips in Cleveland Bay and the Herbert estuary, and comparisons were made with concentrations of dissolved, particulate and organic phosphorus determined by standard techniques. The iron-strip method was shown to work well under laboratory conditions, but the field studies showed varying results for the different environments tested. Generally, most of the dissolved inorganic phosphorus present in sea water was taken up by the strips. The iron strips also took up a proportion of other phosphorus fractions in sea water, but the nature of this uptake appears to vary with environmental conditions.

Effect of terrestrial and marine humics on copper speciation in an estuary in the Great Barrier Reef Lagoon

Graham B. Jones et al. — Wed, 26 May 2010 15:02:32 PDT

Regional and seasonal variations of trace metals in tropical Phaeophyceae from North Queensland

C Burdon-Jones et al. — Wed, 26 May 2010 15:02:31 PDT

The brown algae Padina tenuis and P. tetrastromatica were selected as indicator organisms to monitor levels of ten metals (Fe, Cu, Co, Cd, Ni, Cr, Ag, Pb, Mn, Zn) in seawater from stations within Halifax Bay, Cleveland Bay, and Bowling Green Bay, near Townsville, on the northeast coast of Australia. Samples were collected monthly for one year to determine regional and seasonal variations of metal concentrations. The highest Cu, Pb and Zn concentrations in algae were found at the Townsville Harbour station in Cleveland Bay. However, seawater samples from the Harbour and Bowling Green Bay showed significantly higher levels only for Zn in the harbour waters. Furthermore, levels of dissolved Cd and Mn did not differ significantly between the two stations whereas levels of both metals were significantly lower in algae from the Harbour. It was concluded that the availabilities of, at least, Cd, Pb and Mn to algae were not readily identified by the techniques employed. Location-dependent variability was observed regarding correlations between metal pairs in algae and in those metals which were significantly correlated with temperature and salinity changes.

Trace metals as tracers of dredging activity in Cleveland Bay - Field and laboratory studies

A J. Reichelt et al. — Wed, 26 May 2010 15:02:30 PDT