Improving the measurement of nitrogen stable isotopes in organic materials containing high C:N ratios using a 5A molecular sieve column.

The nitrogen stable isotope composition (δN) of plant materials has numerous applications. Plant materials like bark can have a very high C:N ratio. Incomplete C combustion in such samples interferes with the δN measurement due to CO production.

Water temperature affects somatic growth, body condition and oxygen and carbon otolith isotopes of stout whiting (Sillago robusta).

Ocean warming will continue to affect the growth, body condition and geographic distributions of marine fishes and understanding these effects is an urgent challenge for fisheries research and management. Determining how temperature is recorded in fish otolith carbonate, provides an additional chronological tool to investigate thermal histories, preferences and patterns of movement throughout an individual's life history. The influence of three water temperature treatments (22°C, 25°C, and 28°C) on hatchery-reared juvenile stout whiting, Sillago robusta, was tested using a controlled outdoor mesocosm system.

Automated weighing in the stable isotope lab: When less is more.

Automated powder weighing is an elusive goal in scientific laboratories. The main problem is that powders are much more heterogeneous than liquids, making difficult the development of a unified automation solution for their handling. A compromise has been presented with miau, a low-cost, open-source autosampler for microbalance.

Adapting an elemental analyser to perform high-temperature catalytic oxidation for dissolved organic carbon measurements in water.

Rationale: Many laboratories employ elemental analyzers (EAs) coupled to isotope ratio mass spectrometers (IRMSs) to measure carbon stable isotope ratios (δ C) in solid samples. Dissolved organic carbon (DOC) in most natural water samples cannot be analyzed using this approach unless time-consuming preconcentration is employed.

Methods: An EA-IRMS can be used to measure DOC δ C in natural waters without the need for sample preconcentration by employing high-temperature catalytic oxidation.

Miau, a microbalance autosampler.

Powder weighing is an essential but tedious activity in many branches of science. Here I describe a MIcrobalance AUtosampler (miau) that transfers solids in the sub-mg range to a microbalance. Miau is a pick-and-place machine which moves a gripper with dual function: 1) move tin capsules; 2) deliver powder from a container to tin capsules.

Portable open-source autosampler for shallow waters.

Automated water sampling can be very useful, but open-source choices are limited. Here I present an autosampler which consists of a gantry robot that delivers water from a syringe pump to 24 capped 40 ml vials. The autosampler is controlled using an Android tablet automatized using Macrodroid.

Open-source autosampler for elemental and isotopic analyses of solids.

Elemental and isotopic analyses are performed using elemental analyzers, and are widely employed for diverse scientific fields. An elemental analyzer is typically equipped with an autosampler. Here we present an open-source autosampler for elemental and isotopic analysis of solid samples.

Interlaboratory test for stable carbon isotope analysis of dissolved inorganic carbon in geothermal fluids.

Rationale: Stable carbon isotope ratios have many applications in natural sciences. In the first worldwide interlaboratory proficiency test, the discrepancies in measured δ C values of natural waters were up to σ = ±3‰. Therefore, we continued the investigation on the analytical data quality assurance of individual laboratories and internal consistency among laboratories worldwide.

Bulk hydrogen stable isotope composition of seaweeds: Clear separation between Ulvophyceae and other classes.

Little is known about the bulk hydrogen stable isotope composition (δ H) of seaweeds. This study investigated the bulk δ H in several different seaweed species collected from three different beaches in Brazil, Australia, and Argentina. Here, we show that Ulvophyceae (a group of green algae) had lower δ H values (between -94‰ and -130‰) than red algae (Florideophyceae), brown algae (Phaeophyceae), and species from the class Bryopsidophyceae (another group of green algae).

Light respiration by subtropical seaweeds.

Here, we report the first-ever measurements of light CO respiration rate (CRR) by seaweeds. We measured the influence of temperature (15-25°C) and light (irradiance from 60 to 670 μmol · m  · s ) on the light CCR of two subtropical seaweed species, and measured the CRR of seven different seaweed species under the same light (150 μmol · m  · s ) and temperature (25°C). There was little effect of irradiance on light CRR, but there was an effect of temperature.

Novel use of cavity ring-down spectroscopy to investigate aquatic carbon cycling from microbial to ecosystem scales.

Development of cavity ring-down spectroscopy (CRDS) has enabled real-time monitoring of carbon stable isotope ratios of carbon dioxide and methane in air. Here we demonstrate that CRDS can be adapted to assess aquatic carbon cycling processes from microbial to ecosystem scales. We first measured in situ isotopologue concentrations of dissolved CO2 ((12)CO2 and (13)CO2) and CH4 ((12)CH4 and (13)CH4) with CRDS via a closed loop gas equilibration device during a survey along an estuary and during a 40 h time series in a mangrove creek (ecosystem scale).

Stable carbon isotope analysis of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in natural waters--results from a worldwide proficiency test.

Rationale: Stable carbon isotope ratios of dissolved inorganic (DIC) and organic carbon (DOC) are of particular interest in aquatic geochemistry. The precision for this type of analysis is typically reported in the range of 0.1‰ to 0.

Integration of analytical instruments with computer scripting.

Automation of laboratory routines aided by computer software enables high productivity and is the norm nowadays. However, the integration of different instruments made by different suppliers is still difficult, because to accomplish it, the user must have knowledge of electronics and/or low-level programming. An alternative approach is to control different instruments without an electronic connection between them, relying only on their software interface on a computer.

SHORT-TERM MEASUREMENT OF CARBON STABLE ISOTOPE DISCRIMINATION IN PHOTOSYNTHESIS AND RESPIRATION BY AQUATIC MACROPHYTES, WITH MARINE MACROALGAL EXAMPLES(1).

Progress in the study of stable isotope discrimination in carbon assimilation by aquatic macrophytes has been slower than for other groups of primary producers, such as phytoplankton and terrestrial plants. A probable reason has been the methodologies employed for such a study: field collections or long-term incubations, both relying on the observation of changes in carbon isotope composition of plant tissue. Here, we present a short-term incubation method based on the change in carbon stable isotope composition in water.