Plastic and terrestrial organic matter degradation by the humic lake microbiome continues throughout the seasons.

Boreal freshwaters go through four seasons, however, studies about the decomposition of terrestrial and plastic compounds often focus only on summer. We compared microbial decomposition of C-polyethylene, C-polystyrene, and C-plant litter (Typha latifolia) by determining the biochemical fate of the substrate carbon and identified the microbial decomposer taxa in humic lake waters in four seasons. For the first time, the annual decomposition rate including separated seasonal variation was calculated for microplastics and plant litter in the freshwater system.

Protocols for sample preparation and compound-specific stable-isotope analyses (δH, δC) of fatty acids in biological and environmental samples.

Compound-specific stable-isotope analysis (CSIA) of fatty acids is a powerful tool to better understand the trophic transfer of fatty acids and their biochemical fate in and across ecosystems, including tracing animal migration and understanding physiological processes. The non-exchangeable nature of C-H bonds in acyl chains, hydrogen (H) and carbon (C) stable-isotope values of fatty acids (FA) provide independent information about the origins of fatty acids. Several technical obstacles must be overcome to ensure accurate and reproducible measurements of FA-CSIA can be made.

Preparing for the future offspring: European perch (Perca fluviatilis) biosynthesis of physiologically required fatty acids for the gonads happens already in the autumn.

Long-chain polyunsaturated fatty acids (PUFA) are critical for reproduction and thermal adaptation. Year-round variability in the expression of fads2 (fatty acid desaturase 2) in the liver of European perch (Perca fluviatilis) in a boreal lake was tested in relation to individual variation in size, sex, and maturity, together with stable isotopes values as well as fatty acids (FA) content in different tissues and prey items. ARA and DHA primary production was restricted to the summer months, however, perch required larger amounts of these PUFA during winter, as their ARA and DHA muscle content was higher compared to summer.

Environmental drivers alter PUFA content in littoral macroinvertebrate assemblages via changes in richness and abundance.

Unlabelled: Shallow littoral areas in lakes are productive and highly diverse ecotonal zones, providing habitats for both invertebrate and vertebrate species. We developed a Bayesian modeling framework to elucidate the relationships between environmental drivers (lake typology, habitat, water chemistry, and latitude) and taxon richness, abundance, as well as the content of polyunsaturated fatty acids (PUFAs) in littoral macroinvertebrate communities in 95 boreal lakes. PUFAs, particularly arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), are critical micronutrients to maintain normal physiological functions in consumers.

Eutrophication effect on production and transfer of omega-3 fatty acids in boreal lake food webs.

Eutrophication, i.e. increasing level of nutrients and primary production, is a central environmental change of lakes globally with wide effects on food webs.

Temperature, phosphorus and species composition will all influence phytoplankton production and content of polyunsaturated fatty acids.

Temperature increases driven by climate change are expected to decrease the availability of polyunsaturated fatty acids in lakes worldwide. Nevertheless, a comprehensive understanding of the joint effects of lake trophic status, nutrient dynamics and warming on the availability of these biomolecules is lacking. Here, we conducted a laboratory experiment to study how warming (18-23°C) interacts with phosphorus (0.

Mercury and amino acid content relations in northern pike (Esox lucius) in subarctic lakes along a climate-productivity gradient.

Mercury is a highly toxic element for consumers, but its relation to amino acids and physiology of wild fish is not well known. The main aim of this study was to evaluate how total mercury content (THg) of northern pike (Esox lucius) is related to amino acids and potentially important environmental and biological factors along a climate-productivity gradient of ten subarctic lakes. Linear regression between THg and sixteen amino acids content [nmol mg dry weight] from white dorsal muscle of pike from these lakes were tested.

Biodegradation of microplastic in freshwaters: A long-lasting process affected by the lake microbiome.

Plastics have been produced for over a century, but definitive evidence of complete plastic biodegradation in different habitats, particularly freshwater ecosystems, is still missing. Using C-labelled polyethylene microplastics (PE-MP) and stable isotope analysis of produced gas and microbial membrane lipids, we determined the biodegradation rate and fate of carbon in PE-MP in different freshwater types. The biodegradation rate in the humic-lake waters was much higher (0.

Dark matters: Contrasting responses of stream biofilm to browning and loss of riparian shading.

Concentrations of terrestrial-derived dissolved organic carbon (DOC) in freshwater ecosystems have increased consistently, causing freshwater browning. The mechanisms behind browning are complex, but in forestry-intensive regions browning is accelerated by land drainage. Forestry actions in streamside riparian forests alter canopy shading, which together with browning is expected to exert a complex and largely unpredictable control over key ecosystem functions.

Lowered nutritional quality of prey decrease the growth and biomolecule content of rainbow trout fry.

Diet quality is crucial for the development of offspring. Here, we examined how the nutritional quality of prey affects somatic growth and the lipid, carbohydrate, protein, amino acid, and polyunsaturated fatty acid content of rainbow trout (Oncorhynchus mykiss) fry using a three-trophic-level experimental setup. Diets differed especially in their content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are physiologically essential polyunsaturated fatty acids for a fish fry.

Allochthony, fatty acid and mercury trends in muscle of Eurasian perch (Perca fluviatilis) along boreal environmental gradients.

Environmental change, including joint effects of increasing dissolved organic carbon (DOC) and total phosphorus (TP) in boreal northern lakes may affect food web energy sources and the biochemical composition of organisms. These environmental stressors are enhanced by anthropogenic land-use and can decrease the quality of polyunsaturated fatty acids (PUFAs) in seston and zooplankton, and therefore, possibly cascading up to fish. In contrast, the content of mercury in fish increases with lake browning potentially amplified by intensive forestry practises.

Poor nutritional quality of primary producers and zooplankton driven by eutrophication is mitigated at upper trophic levels.

Eutrophication and rising water temperature in freshwaters may increase the total production of a lake while simultaneously reducing the nutritional quality of food web components. We evaluated how cyanobacteria blooms, driven by agricultural eutrophication (in eutrophic Lake Köyliöjärvi) or global warming (in mesotrophic Lake Pyhäjärvi), influence the biomass and structure of phytoplankton, zooplankton, and fish communities. In terms of the nutritional value of food web components, we evaluated changes in the ω-3 and ω-6 polyunsaturated fatty acids (PUFA) of phytoplankton and consumers at different trophic levels.

Ecology and extent of freshwater browning - What we know and what should be studied next in the context of global change.

Water browning or brownification refers to increasing water color, often related to increasing dissolved organic matter (DOM) and carbon (DOC) content in freshwaters. Browning has been recognized as a significant physicochemical phenomenon altering boreal lakes, but our understanding of its ecological consequences in different freshwater habitats and regions is limited. Here, we review the consequences of browning on different freshwater habitats, food webs and aquatic-terrestrial habitat coupling.

Vulnerability of the North Water ecosystem to climate change.

High Arctic ecosystems and Indigenous livelihoods are tightly linked and exposed to climate change, yet assessing their sensitivity requires a long-term perspective. Here, we assess the vulnerability of the North Water polynya, a unique seaice ecosystem that sustains the world's northernmost Inuit communities and several keystone Arctic species. We reconstruct mid-to-late Holocene changes in sea ice, marine primary production, and little auk colony dynamics through multi-proxy analysis of marine and lake sediment cores.

Environmental and biological factors are joint drivers of mercury biomagnification in subarctic lake food webs along a climate and productivity gradient.

Subarctic lakes are getting warmer and more productive due to the joint effects of climate change and intensive land-use practices (e.g. forest clear-cutting and peatland ditching), processes that potentially increase leaching of peat- and soil-stored mercury into lake ecosystems.

Selective Fatty Acid Retention and Turnover in the Freshwater Amphipod .

Gammarid amphipods are a crucial link connecting primary producers with secondary consumers, but little is known about their nutritional ecology. Here we asked how starvation and subsequent feeding on different nutritional quality algae influences fatty acid retention, compound-specific isotopic carbon fractionation, and biosynthesis of ω-3 and ω-6 polyunsaturated fatty acids (PUFA) in the relict gammarid amphipod . The fatty acid profiles of closely matched with those of the dietary green algae after only seven days of refeeding, whereas fatty acid patterns of were less consistent with those of the diatom diet.

Increasing temperature and productivity change biomass, trophic pyramids and community-level omega-3 fatty acid content in subarctic lake food webs.

Climate change in the Arctic is outpacing the global average and land-use is intensifying due to exploitation of previously inaccessible or unprofitable natural resources. A comprehensive understanding of how the joint effects of changing climate and productivity modify lake food web structure, biomass, trophic pyramid shape and abundance of physiologically essential biomolecules (omega-3 fatty acids) in the biotic community is lacking. We conducted a space-for-time study in 20 subarctic lakes spanning a climatic (+3.

Stable isotopes of fatty acids: current and future perspectives for advancing trophic ecology.

To understand consumer dietary requirements and resource use across ecosystems, researchers have employed a variety of methods, including bulk stable isotope and fatty acid composition analyses. Compound-specific stable isotope analysis (CSIA) of fatty acids combines both of these tools into an even more powerful method with the capacity to broaden our understanding of food web ecology and nutritional dynamics. Here, we provide an overview of the potential that CSIA studies hold and their constraints.

Comparison of Bayesian and numerical optimization-based diet estimation on herbivorous zooplankton.

Consumer diet estimation with biotracer-based mixing models provides valuable information about trophic interactions and the dynamics of complex ecosystems. Here, we assessed the performance of four Bayesian and three numerical optimization-based diet estimation methods for estimating the diet composition of herbivorous zooplankton using consumer fatty acid (FA) profiles and resource library consisting of the results of homogeneous diet feeding experiments. The method performance was evaluated in terms of absolute errors, central probability interval checks, the success in identifying the primary resource in the diet, and the ability to detect the absence of resources in the diet.

Variation in ω-3 and ω-6 Polyunsaturated Fatty Acids Produced by Different Phytoplankton Taxa at Early and Late Growth Phase.

Phytoplankton synthesizes essential ω-3 and ω-6 polyunsaturated fatty acids (PUFA) for consumers in the aquatic food webs. Only certain phytoplankton taxa can synthesize eicosapentaenoic (EPA; 20:5ω3) and docosahexaenoic acid (DHA; 22:6ω3), whereas all phytoplankton taxa can synthesize shorter-chain ω-3 and ω-6 PUFA. Here, we experimentally studied how the proportion, concentration (per DW and cell-specific), and production (µg FA L day) of ω-3 and ω-6 PUFA varied among six different phytoplankton main groups (16 freshwater strains) and between exponential and stationary growth phase.

Osmotrophic glucose and leucine assimilation and its impact on EPA and DHA content in algae.

The uptake of dissolved organic compounds, that is, osmotrophy, has been shown to be an efficient nutritional strategy for algae. However, this mode of nutrition may affect the biochemical composition, for example, the fatty acid (FA) contents, of algal cells. This study focused on the osmotrophic assimilation of glucose and leucine by selected seven algal strains belonging to chlorophytes, chrysophytes, cryptophytes, dinoflagellates and euglenoids.

Eutrophication reduces the nutritional value of phytoplankton in boreal lakes.

Eutrophication (as an increase in total phosphorus [TP]) increases harmful algal blooms and reduces the proportion of high-quality phytoplankton in seston and the content of ω-3 long-chain polyunsaturated fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) in fish. However, it is not well-known how eutrophication affects the overall nutritional value of phytoplankton. Therefore, we studied the impact of eutrophication on the production (as concentration; μg L) and content (μg mg C) of amino acids, EPA, DHA, and sterols, i.