Dr Matheus Carvalho de Carvalho

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. Fish were measured for change in length and weight, and body condition was determined using bioelectrical impedance analysis. Sagittal otoliths were analysed for stable oxygen (δ18Ootolith) and carbon (δ13Cotolith) isotopes via isotope ratio mass spectrometry. Whiting kept at 22°C were significantly smaller and had diminished body condition compared to fish in 25°C and 28°C, which did not significantly differ from each other. The δ18O otolith values of stout whiting demonstrated a negative temperature-dependent fractionation relationship which was similar in slope but had a different intercept to the relationships reported for inorganic aragonite and other marine fish species. The δ13C otolith values also showed a negative relationship with water temperature, and the calculated proportion of metabolic carbon M in otoliths differed between fish reared in the coolest (22°C) and warmest (28°C) temperature treatments. Overall, the results suggest that stout whiting may have reached an upper growth threshold between 25°C and 28°C, and that growth and body condition may be optimised during warmer seasons and toward the northerly regions of their distribution. Otolith oxygen thermometry shows promise as a natural tracer of thermal life history, and species-specific fractionation equations should be utilised when possible to prevent errors in temperature reconstructions of wild-caught fish.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. Fish were measured for change in length and weight, and body condition was determined using bioelectrical impedance analysis. Sagittal otoliths were analysed for stable oxygen (δ18Ootolith) and carbon (δ13Cotolith) isotopes via isotope ratio mass spectrometry. Whiting kept at 22°C were significantly smaller and had diminished body condition compared to fish in 25°C and 28°C, which did not significantly differ from each other. The δ18O otolith values of stout whiting demonstrated a negative temperature-dependent fractionation relationship which was similar in slope but had a different intercept to the relationships reported for inorganic aragonite and other marine fish species. The δ13C otolith values also showed a negative relationship with water temperature, and the calculated proportion of metabolic carbon M in otoliths differed between fish reared in the coolest (22°C) and warmest (28°C) temperature treatments. Overall, the results suggest that stout whiting may have reached an upper growth threshold between 25°C and 28°C, and that growth and body condition may be optimised during warmer seasons and toward the northerly regions of their distribution. Otolith oxygen thermometry shows promise as a natural tracer of thermal life history, and species-specific fractionation equations should be utilised when possible to prevent errors in temperature reconstructions of wild-caught fish.

Compound-specific isotope analysis (CSIA) can provide unique insights into the cycling of elements including carbon and nitrogen. One approach for CSIA is the use of high-performance liquid chromatography (HPLC) to separate compounds of interest, followed by analysis of these compounds using an elemental analyser coupled to an isotope ratio mass spectrometer. A key component of this technique is the fraction collector, which automatically collects compounds as they are separated by HPLC. Here, we present a fraction collector that is a simple adaptation of a 3D printer, and, thus, can be easily adopted by any laboratory already equipped for HPLC. In addition to the much lower cost compared to commercial alternatives, this adaptation has the advantage for CSIA that the 3D printer is able to heat the collected fractions, which is not true for many commercial fraction collectors. Heating allows faster evaporation of the solvent, so that the dried compounds can be measured by EA–IRMS immediately. The procedure can be repeated consecutively so that diluted solutions can have the compounds concentrated for analysis. Any computer-controlled HPLC can be integrated to the fraction collector used here by means of AutoIt.

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. Miau was demonstrably useful to perform the automated weighing of some powders, as long as the same powder is weighed repeatedly, which is useful for preparing standards to be measured along samples. However, in stable-isotope laboratories it is also necessary to weigh samples, which are often very heterogeneous, and thus not amenable for miau. Here it is demonstrated how miau can be adapted to handle not only standards, but also samples, using the “less is more” philosophy:
• Miau is simplified to perform only the manipulation of weighing capsules, becoming “miau
redux”
• Miau redux can be used not only for standards, but for a variety of samples as well
• Miau redux saves 64% of operator time when using a microbalance

Many laboratories employ elemental analyzers (EA) coupled to isotope ratio mass spectrometers (IRMS) to measure carbon stable isotope ratios (δ13C) in solid samples. Dissolved organic carbon (DOC) in most natural water samples cannot be analyzed using this approach unless time consuming preconcentration is employed.

An EA-IRMS can be used to measure DOC δ13C in natural waters without the need for sample preconcentration by employing high-temperature catalytic oxidation. An autosampler injects water in the EA reactor at 680oC filled with platinum catalyst beads, where all carbon is converted to CO. Remaining water and halides are removed, while CO is trapped in a cryotrap and later released to the IRMS.

Measurements were accurate (deviation < 0.3 ‰ compared to solid sample measurements) and precise (error of 0.3 ‰ for concentrations ≥ 46 μM). Blanks were present and accounted for. Salinity up to seawater level did not affect accuracy or precision, but limited the number of samples that could be run before cleaning of the reactor was needed. DOC δ13C in a river/estuary varied between -25.7 and -23.2 ‰, with higher values for waters with higher salinity, as expected. Deep-sea water reference material had a value of -22.9 ± 0.5 ‰, very similar to those found in recent reports employing similar techniques.

Adapting an EA is a feasible approach for the measurement of DOC δ13C in natural waters. The low cost and simplicity of the system allow its use in any laboratory already equipped with EA-IRMS.

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. In our laboratory we routinely use miau to prepare working standards for quality control of elemental and isotopic analyses. In a test, miau produced standards between 0.3 and 1.1 mg, which is a useful range in our laboratory. Failure to produce a weighed standard happened in 5% of the cases. A comparison with manual measurements demonstrated that obtained amounts for automated samples were as accurate and precise as manually prepared ones. Setup for daily use is simple, and the microbalance can be easily used alternately with or without miau. Miau is a low-cost device that can work with microbalances from many manufacturers, and can be readily adopted by many laboratories.

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. Three rinsing cycles ensure negligible carryover between consecutive samples. Hourly sampling from a creek under rainy conditions suggested that total organic carbon in water was diluted by the rain. Some important limitations: 1) the autosampler must be on a steady, flat, horizontal surface; 2) unattended sampling can only last as long as the batteries powering the tablet and the motors; 3) distance from the syringe pump to water cannot exceed ~2 m in height and ~4 m in length for 3 mm tubing; 4) sampling frequency does not exceed one sample every eleven minutes. However, because of its open design, the autosampler can be modified and improved to not only overcome these limitations, but also potentially expand its scope to more demanding sampling if necessary.

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. We designed and performed an interlaboratory comparison exercise for δ C analyses of ten water and two solid samples (Na CO , CaCO ), including two synthetic samples prepared by dissolving the carbonates individually. Three laboratories analyzed an additional sample set to assess solution stability, at least one month after the first set analysis period. The δ C values were measured using dual inlet isotope ratio mass spectrometry (DI-IRMS) or continuous flow (CF)-IRMS. The δ C values of solid Na CO and its aqueous solution were -5.06 ± 0.21‰ and 5.32 ± 0.24‰, respectively, while the δ C value of solid CaCO was -4.49 ± 0.93‰. Similarly, the lake water has a consistent value (2.45 ± 0.19‰). The δ C values of geothermal water have a wide dispersion among individual laboratory measurements and among those of different laboratories; however, a trend exists in the δ C values measured at the three sampling points of each well. The δ C values of solid Na CO and its solution, and lake water (i.e. DIC concentration samples >100 mg/L carbon) are consistent among all the participating laboratories. The dispersion in the δ C values of solid CaCO is associated with its lower chemical affinity than that of Na CO . The poor reproducibility in the δ C values of geothermal fluids, collected at three points of a geothermal well, despite overall consistent trends regarding their collection points suggests inadequate sample handling (atmospheric CO exchange) and/or inappropriate analytical approaches (incomplete H PO acid reaction).

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. The autosampler consists of 1) a sampling table, on which a carousel pushes samples inside an orifice, and 2) a purging pipe, placed directly beneath the orifice, where the sample is purged off surrounding air, and then delivered to the reaction tube. The action of the purging pipe ensured that air contamination, an issue for the analysis of some elements like nitrogen and oxygen, was negligible, and results for elemental and isotopic composition of nitrogen and carbon were inside specs. Compared to commercial alternatives, the autosampler presented here has the advantages of lower cost to build and maintain, universal compatibility with instruments from different manufacturers, capacity do deal with bulky samples, capacity for a larger number of samples in a single run, and no necessity for time-consuming purging in-between sample loading. The autosampler could potentially also be employed for the analyses of other elements (e.g. oxygen, hydrogen and sulfur) because they are performed using similar equipment.

Microsyringe manipulation is a common approach for the automated sampling of liquids or gases. Commercial devices with this capacity are typically priced above US$30,000, despite their technology being not clearly superior to that commonly found in low-cost (commonly less than US$1,000) devices controlled using G-code (3D printers, CNC routers and laser engravers, for example). Here, we present osmar, an open-source autosampler built by combining parts of two low-cost G-code machines. Movement precision was excellent (error <1% in repeated injections, equivalent to the error reported by the microsyringe manufacturer), and system reliability was comparable to that of commercial models. Also, users do not need extensive knowledge in electronics or advanced computing to make osmar work as an autosampler, because it can easily be integrated with analytical instruments using AutoIt, a scripting language for the Windows Operating System. Therefore, osmar is a viable, low-cost, and technically-accessible alternative for automated sampling with microsyringes, and can be also adapted and expanded for more general liquid handling tasks.

Radionuclide measurements have proven to be essential for determining processes related to pressing environmental issues as well as reconstructing historical events related to natural and anthropogenic activities. The detection of radionuclide tracers in environmental and geological samples provides unique and essential insights into specific sources and sinks. Despite its usefulness in measuring natural and anthropogenic radioisotopes, high-purity germanium (HPGe) gamma ray detectors are rarely automated as a result of the heavy shielding required to use this equipment. Consequently, the commonly available autosamplers for this kind of analysis can be very expensive, exceeding AU$400,000. Here we present auto-HPGe, an autosampler for gamma ray detection in heavy shields that costs about AU$1100 to build. Auto-HPGe has potential to make HPGe analysis more attractive to scientists, especially when the equipment is located in remote locations or when the ability to change samples at odd hours is limited.