Environmental feedbacks in temperate aquatic ecosystems under global change: why do we need to consider chemical stressors?

Regional Environmental Change - Globally increasing temperature and modifications in precipitation patterns induce major environmental alterations in aquatic ecosystems. Particularly profound...     

When to pay the cost of reproduction? A brood size manipulation experiment in great tits (<Emphasis Type="Italic">Parus major</Emphasis>)

Parental investment (PI) theory assumes that optimal parental investment is a function of expected cost/benefit ratio of current versus future reproduction. This study tests the prediction of PI theory that in a species with high adult mortality, paying of reproductive costs can be induced or prevented by manipulation of brood reproductive value (RV). Analysis of recruitment rates in a 10-year study of great tits (Parus major) showed that brood RV was affected by both fledgling number and quality (body mass and tarsus length). A 4-year brood size manipulation experiment (±2 hatchlings) resulted in reduction of fledgling quality in enlarged versus control and reduced broods, while the fledgling number did not differ between manipulation categories due to increase of nestling mortality with brood size manipulation score. Hence, the experiment resulted in reduction of brood RVs in enlarged broods. Females rearing enlarged broods survived better than those with control and reduced broods, while male survival was not affected by the experiment. This indicates that paying the survival costs for reproduction was a part of normal life history for studied female great tits, and that decisions whether to pay this cost were based on the estimation of brood RV. Recruitment rate was lowest (but extremely male-biased) in reduced broods, while control and increased broods did not differ in the number of locally recaptured offspring.     

A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters

The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO₂) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO₂ production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO₂ production by mineralization as well as CO₂ loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of \( {0.70}_{-0.31}^{+0.27} \) to \( {1.52}_{-0.90}^{+1.09} \) Pg C yr^?1 depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO₂ sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO₂ sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.     

Quantification of a Primary Production Model Using Two Versions of the Spectral Distribution of the Phytoplankton Absorption Coefficient

In a recent publication, we discussed and presented a semi-empirical phytoplankton primary production model. In the present paper, our main purpose is to determine how the algorithms of a primary production model change when different values of specific absorption coefficient by phytoplankton are used in the model. A new version of our earlier model was quantified for this purpose. Differences between the previous and the new models are as follows: (a) the spectra of the specific absorption coefficient of light by phytoplankton differ in the new model from those used in the previous model, and (b) the quantification of the new model brings about a change in the parameters of the algorithm for the quantum yield of carbon fixation. We compared the results of primary production profiles obtained by the new model with those measured in situ and also with the values obtained by the previous model. Due to an adequate choice of quantification parameters, both the old and new models give rather close values of phytoplankton primary production. In the present study, the computational algorithms of both models have been automated. The resulting programs calculate the temporal–spatial variability of phytoplankton primary production, providing hourly values from morning to evening, daily sums, and monthly sums. The input of a table of initial parameters and selected depths produces rapid calculations of the model's results, which are given as vertical profiles of primary production and areal values.     

Multidimensionality of fear in captive greenfinches (Carduelis chloris)

Covariation of individual responses to different fear-eliciting situations is expected to manifest in general “fearfulness syndrome.” We tested for the existence of such a syndrome in wild-caught captive greenfinches. We assessed the propensity to give distress calls at handling, latency to feed at the presence of a predator image, and changes in locomotor activity in response to distress calls of conspecifics. Additionally, we measured the frequency of flapping flight movements against cage bars and tendency to damage tail feathers in captivity as indicators of the ability of birds to cope with captive conditions. As a proxy of neuroendocrine activity (an expected covariate of fearfulness), we measured the amount of stress hormone corticosterone deposited into feathers grown during captivity. All the behavioral traits were individually repeatable in time, but there were no correlations between them. Lack of the behavioral syndrome for fearfulness was also revealed by structural equation modelling. The findings of this experiment challenge the concept of a single internal variable responsible for fearfulness and support the proposed multidimensional nature of fear responses.     

Assessment of oxidative burst in avian whole blood samples: validation and application of a chemiluminescence method based on Pholasin

Immunoecology deals with the questions about how immune defences have evolved and are being used and optimized in different environments, ecological settings and lineages. In such research, often only single time point measures and small sample volumes are available, which limits the applicability of traditional immunological methods. Methodological progress in the field thus largely depends on the development and validation of immune assays suitable for ecological studies. Here we validate and apply a novel, Pholasin-based chemiluminescence method for assessment of oxidative burst in the whole blood samples of birds. This assay measures an inducible component of innate immunity by quantifying the immediate extracellular oxidative burst of stimulated phagocytes. The assay procedure is simple, measurement precision is satisfactory and the measurement time is only 6 min. It can be performed on 20 μL (or smaller) blood samples that can be preserved for a few days. Blood of six studied passerine species produced chemiluminescence response to stimulation with bacterial lipopolysaccharide (LPS) in vitro. The magnitude of the response depended on the concentration and origin of the LPS. Parameters of this response depended on biological factors such as age of birds and in vivo priming with different antigens such LPS and Brucella abortus antigen suspension. Different parameters of the chemiluminescence response were significantly repeatable over 6-day period. All these properties argue for a great potential applicability of this method in immunoecological research.     

Interacting environmental and chemical stresses under global change in temperate aquatic ecosystems: stress responses,adaptation, and scaling

Regional Environmental Change - Unfavorable environmental conditions—abiotic stress—constitute one of the key drivers of evolution leading to environmental adaptation. Since the start...