Land based mesocosm experiment studying the simultaneous impact of warming and acidification on the planktonic food web of the Eastern Mediterranean

A land based mesocosm experiment focusing on the study of the simultaneous impact of warming and acidification on the planktonic food web of the Eastern Mediterranean took place in August-September 2013 at the mesocosm facilities of HCMR in Crete (CRETACOSMOS). Two different pCO2 (present day and predicted for year 2100) were applied in triplicate mesocosms of 3 m**3. This was tested in two different temperatures (ambient seawater T and ambient T plus 3°C). Twelve mesocosms in total were incubated in two large concrete tanks. Temperature was controlled by sophisticated, automated systems. A large variety of chemical, biological and biochemical variables were studied, including salinity, temperature, light and alkalinity measurements, inorganic and organic, particulate and dissolved, nutrient analyses, biological stock (Chla concentration, enumeration and community composition of microbial, phyto- and zooplankton organisms) and rate (primary, bacterial, viral production, copepod egg production, zooplankton grazing, N2 fixation, P uptake) measurements, bacterial DNA extraction and phytoplankton transcriptomics, calcifiers analyses. Twenty three scientists from 6 Institutes and 5 countries participated in this experiment.

European mink (Mustela lutreola) and American mink (Neovison vison) detection histories in Northern Spain between 2000 and 2011

Understanding changes over time in the distribution of interacting native and invasive species that may be symptomatic of competitive exclusion is critical to identify the need for and effectiveness of management interventions. Occupancy models greatly increase the robustness of inference that can be made from presence/absence data when species are imperfectly detected, and recent novel developments allow for the quantification of the strength of interaction between pairs of species. We used a two-species multi-season occupancy model to quantify the impact of the invasive American mink on the native European mink in Spain through the analysis of their co-occurrence pattern over twelve years (2000 - 2011) in the entire Spanish range of European mink distribution, where both species were detected by live trapping but American mink were culled. We detected a negative temporal trend in the rate of occupancy of European mink and a simultaneous positive trend in the occupancy of American mink. The species co-occurred less often than expected and the native mink was more likely to become extinct from sites occupied by the invasive species. Removal of American mink resulted in a high probability of local extinction where it co-occurred with the endemic mink, but the overall increase in the probability of occupancy over the last decade indicates that the ongoing management is failing to halt its spread. More intensive culling effort where both species co-exist as well as in adjacent areas where the invasive American mink is found at high densities is required in order to stop thedecline of European mink.

Simultaneous high-resolution pH and spectrophotometric recordings of oxygen binding in native blood microvolumes, link to supplementary material

Oxygen equilibrium curves have been widely used to understand oxygen transport in numerous organisms. A major challenge has been to monitor oxygen binding characteristics and concomitant pH changes as they occur in vivo, in limited sample volumes. Here we report a technique allowing highly resolved and simultaneous monitoring of pH and blood pigment saturation in minute blood volumes. We equipped a gas diffusion chamber with a broad range fibre optic spectrophotometer and a micro-pH optode and recorded changes of pigment oxygenation along PO2 and pH gradients to test the setup. Oxygen binding parameters derived from measurements in only 15 µl of haemolymph from the cephalopod Octopus vulgaris showed low instrumental error (0.93%) and good agreement with published data. Broad range spectra, each resolving 2048 data points, provided detailed insight into the complex absorbance characteristics of diverse blood types. After consideration of photobleaching and intrinsic fluorescence, pH optodes yielded accurate recordings and resolved a sigmoidal shift of 0.03 pH units in response to changing PO2 from 0-21 kPa. Highly resolved continuous recordings along pH gradients conformed to stepwise measurements at low rates of pH changes. In this study we showed that a diffusion chamber upgraded with a broad range spectrophotometer and an optical pH sensor accurately characterizes oxygen binding with minimal sample consumption and manipulation. We conclude that the modified diffusion chamber is highly suitable for experimental biologists who demand high flexibility, detailed insight into oxygen binding as well as experimental and biological accuracy combined in a single set up.