Ursula Strandberg

University of Eastern Finland | UEF · Department of Environmental and Biological Sciences

A priori knowledge of fatty acid modifications in consumers is essential for studies using fatty acids as biomarkers. We investigated fatty acid metabolism and possible modification pathways in benthic invertebrate Chironomus riparius larvae (Diptera). We conducted diet manipulation experiments using natural food sources (two chlorophyte algae, a d...

This study evaluated the spatial variability of risks and benefits of consuming fish from humic and clear lakes. Mercury in fish is a potential risk for human health, but risk assessment may be confounded by selenium, which has been suggested to counterbalance mercury toxicity. In addition to the risks, fish are also rich in eicosapentaenoic acid (...

Contaminants and essential omega-3 fatty acids were analyzed in the fillets of 15 fish species from lakes Superior and Huron in order to estimate the risks and benefits of fish consumption. Additionally, literature data from lakes Ontario and Erie fish were used to provide an overall assessment for 24 fish species from the Canadian waters of the Gr...

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,...

1. Eutrophication has been shown to increase production of nutritionally low-quality cyanobacteria and decrease the long-chain polyunsaturated fatty acid (PUFA) content of seston. Contrarily, lake browning inhibits cyanobacteria contribution in seston and favours poorly grazable mixotrophic algal species. These environ- mental changes have probable...

The effects of lake browning on trophic functioning of planktonic food webs are not fully understood. We studied the effects of browning on the response patterns of polyunsaturated fatty acids and n −3/ n −6 ratio in seston and compared them between boreal and temperate lakes. We also compared the regional differences and the effects of lake browni...

We studied how physiologically important long-chain polyunsaturated fatty acids (PUFA) in benthic macroinvertebrates (Asellus aquaticus, Chironomidae, and Oligochaeta) were related to those in periphyton and terrestrial organic matter (tree leaves), collected from littoral areas of 17 boreal lakes that differed in their dissolved organic carbon (DO...

Climate change and eutrophication are among the main stressors of shallow freshwater ecosystems, and their effects on phytoplankton community structure and primary production have been studied extensively. However, their combined effects on the algal production of polyunsaturated fatty acids (PUFA), specifically, eicosapentaenoic acid (EPA) and doc...

Environmental change, including joint effects of increasing dissolved organic carbon (DOC) and total phosphorus (TP) in boreal northern lakes could potentially affects 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 polyunsatur...

Many lakes in the northern hemisphere are browning due to increasing concentrations of terrestrial dissolved organic carbon (DOC). The consequences of lake browning to littoral invertebrates, however, are not fully understood. We analyzed community structure and fatty acid (FA) profiles of littoral invertebrates in humic (DOC-rich) and clear-water...

Cyanobacteria dominance and warming have been suggested to decrease the production of polyunsaturated fatty acids (PUFA) in freshwater ecosystems. Physiological adaptations of poikilothermic animals to higher temperatures may further decrease PUFA levels in aquatic food webs. We conducted diet manipulation experiments to investigate the combined ef...

Fatty acid (FA) content and composition of zooplankton in Puget Sound, Washington (USA) was studied to investigate the nutritional quality of diverse zooplankton prey for juvenile salmon ( Oncorhynchus spp.) in terms of their essential fatty acid (EFA) content. The study focus was on eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arac...

Food quality is one of the key factors influencing zooplankton population dynamics. Eutrophication drives phytoplankton communities toward the dominance of cyanobacteria, which means a decrease in the availability of sterols and long-chain polyunsaturated fatty acids (EPA and DHA). The effects of different restoration measures on the nutritional qu...

Littoral benthic primary production is considered the most important energy source of consumers in subarctic lakes. We analyzed essential fatty acid (EFA) and amino acid (EAA) content of 23 littoral benthic macroinvertebrate taxa as well as cladocerans and copepods from pelagic and littoral habitats of 8–9 subarctic lakes to compare their nutrition...

Elevated concentrations of dissolved organic carbon (DOC) promote browning of lakes, which alters the physicochemical properties of water and ecosystem functioning. However, browning‐induced changes in basal production of polyunsaturated fatty acids from the n‐3 and n‐6 families (n‐3 and n‐6 PUFA) in lakes are not fully understood. The concentratio...

This is a Technical report for the Salish Sea Marine Survival Project on food quality of juvenile salmonids in Puget Sound. https://marinesurvivalproject.com/ Summary Diets rich in essential fatty acids (EFAs) are critical for the nutritional physiology of many fish, particularly during juvenile life stages. EFAs can be limiting in aquatic food we...

Ecology of the glacial relict macrocrustacean Gammaracanthus lacustris , a rare inhabitant of deep Fennoscandian lakes, is poorly understood. We studied the life cycle and trophic position of this cold‐stenothermic amphipod in Lake Paasivesi, eastern Finland. The study is based on intensive sampling and analyses of fatty acid composition as well as...

Atmospheric changes are leading to the browning of northern lakes (i.e. increases in catchment‐derived dissolved organic matter [ DOM ]), consequently altering phytoplankton biomass and community composition. We hypothesised that lake browning and the concurrent increase in nutrients drive a shift towards greater cyanobacteria biomass. We further h...

The importance of allochthonous organic matter contributions to aquatic food webs has long been debated. We studied the aging process of terrestrial particulate organic matter ( tPOM ) in aquatic ecosystems by incubating senescent plant material in the presence of natural microbial communities in either lake water or artificial growth medium. We hy...

Restricted fish consumption due to elevated contaminant levels may limit the intake of essential omega-3 fatty acids, such as eicosapentaenoic (EPA; 20:5n −3) and docosahexaenoic (DHA; 22:6n −3) acids. We analyzed lake-and length-specific mercury and EPA + DHA contents in Walleye (Sander vitreus; Mitchell 1818) from 20 waterbodies in Ontario, Canad...

Direct consumption of allochthonous resources generally yields poor growth and reproduction in zooplankton, but it is still unclear how trophic upgrading of terrestrial dissolved organic matter (tDOM) via the microbial food web may support zooplankton. We compared survival, somatic growth and reproduction of Daphnia magna fed with the heterotrophic...

Elevated contaminant levels in the North American Great Lakes have resulted in restrictive fish consumption advisories. Avoiding the risks associated with fish consumption may also decrease the intake of omega-3 fatty acids, eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic (DHA; 22:6n-3) acids; compounds that have been associated with human heal...

Spatial and seasonal variation in the abundance and composition of phytoplankton and other basal resources (bacteria, terrestrial detritus) influence the availability of essential polyunsaturated fatty acids (PUFA) for upper trophic levels in lake food webs. We studied accumulation, composition and content of fatty acids in planktivorous ven-dace (...

Fish are an important source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for birds, mammals and humans. In aquatic food webs, these highly unsaturated fatty acids (HUFA) are essential for many physiological processes and mainly synthetized by distinct phytoplankton taxa. Consumers at different trophic levels obtain essential fatty...

Due to altered biogeochemical processes related to climate change, highly colored dissolved organic carbon (DOC) from terrestrial sources will lead to a water "brownification" in many freshwater systems of the Northern Hemisphere. This will create deteriorated visual conditions that have been found to affect habitat-specific morphological variation...

Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. H...

Trophic polymorphism has found to be common in many taxa and is a suggested mechanism of ecological speciation. To characterize the trophic linkages of specific morphotypes of organisms as well as a time-integrated niche use, several methods are available. In this study, we present data of multiple techniques to investigate the trophic divergence o...

The fatty acid (FA) composition of zooplankton has taxon-specific characteristics but may also be influenced by various environmental factors. Abiotic properties of lakes (location, morphometry, water chemistry and temperature) shape the phytoplankton community structure. We studied how this may be manifested in the FA composition of the common fre...

We modified the stable isotope mixing model MixSIR to infer primary producer contributions to consumer diets based on their fatty acid composition. To parameterize the algorithm, we generated a ‘consumer-resource library’ of FA signatures of Daphnia fed different algal diets, using 34 feeding trials representing diverse phytoplankton lineages. This...

We modified the stable isotope mixing model MixSIR to infer primary producer contributions to consumer diets based on their fatty acid composition. To parameterize the algorithm, we generated a ‘consumer-resource library’ of FA signatures of Daphnia fed different algal diets, using 34 feeding trials representing diverse phytoplankton lineages. This...

The taxon specificity of fatty acid composition in algal classes suggests that fatty acids could be used as chemotaxonomic markers for phytoplankton composition. The applicability of phospholipid-derived fatty acids as chemotaxonomic markers for phytoplankton composition was evaluated by using a Bayesian fatty acid-based mixing model. Fatty acid pr...

An increase in loading of dissolved organic carbon (DOC) from terrestrial to freshwater ecosystems has recently been documented in several boreal regions. We studied how transfer of important biomolecules, fatty acids, may be connected to DOC in pelagic food webs of large boreal lakes. We collected nine zooplank-ton taxa during three seasons from s...

We studied the copepod Limnocalanus macrurus for seasonal variation in the composition of fatty acids, wax esters and sterols in large boreal lakes, where it occurs as a glacial-relict. Vast wax ester reserves of Limnocalanus were accumulated in a period of only two months, and comprised mono- and polyunsaturated fatty acids (PUFA) and saturated fa...

The zooplankton is a key link in the transfer of energy from primary producers up through aquatic food webs. Previous efforts to quantify the importance of basal resources to aquatic consumers have used stable isotopes (SI) and simple ternary models, including only ‘bulk’ phytoplankton, bacteria or terrestrial particulate organic matter (t-POM).We...

The aim of this study was to assess metabolic pathways for arachidonic acid (20:4n-6) biosynthesis in Daphnia magna. Neonates of D. magna were maintained on [(13)C] enriched Scenedesmus obliquus and supplemented with liposomes that contained separate treatments of unlabeled docosapentaenoic acid (22:5n-6), 20:4n-6, linoleic acid (18:2n-6) or oleic...

There is considerable interest in the pathways by which carbon and growth-limiting elemental and biochemical nutrients are supplied to upper trophic levels. Fatty acids and sterols are among the most important molecules transferred across the plant-animal interface of food webs. In lake ecosystems, in addition to phytoplankton, bacteria and terrest...

Algal fatty acid (FA) composition is an important determinant of their food quality for consumers. FA can also be used as biomarkers for biochemical and energetic pathways in food webs. FA analyses of seven freshwater algal classes and 37 strains showed clear similarity within classes and strong differences amongst classes. The algal class was domi...

Dietary studies of seabirds provide information on food webs and oceanographic variability. Studying fatty acid signatures (FAS), which reflect changes in the composition of the diet, has several advantages over traditional methods. In the context of the Mediterranean marine ecosystem, we studied tissue FAS in captive-fed and wild seabirds. Yellow-...

Hepatic lipidosis is a common pathological finding in the American mink (Neovison vison) and can be caused by nutritional imbalance due to obesity or rapid body weight loss. The objectives of the present study were to investigate the timeline and characterize the development of hepatic lipidosis in mink in response to 0-7 days of food deprivation a...

This study investigated the structure and innervation of the vibrissal systems of the pole cat (Mustela putorius), European otter (Lutra lutra) and ringed seal (Phoca hispida) in order to find adaptations to aquatic environment. The number of myelinated nerve fibers of deep vibrissal nerve (DVN) of the entire vibrissal system was considerably great...

Abstract This study of vertical fatty acid profiles, based on analysis of 58 fatty acids sampled at 3-mm intervals throughout the blubber column of a model marine mammal, the ringed seal (Pusa hispida), revealed three chemically distinct layers. The average depths of the outer and inner layers were quite consistent (approximately 1.5 and approximat...

This study of vertical fatty acid profiles, based on analysis of 58 fatty acids sampled at 3-mm intervals throughout the blubber column of a model marine mammal, the ringed seal (Pusa hispida), revealed three chemically distinct layers. The average depths of the outer and inner layers were quite consistent (~1.5 and ~1 cm, respectively). Consequent...

Fatty acid signatures (FAS) of plasma and stable isotopes of carbon (8 13 C) and nitrogen (delta N-15) of red blood cells were determined in northern gannets Morus bassanus, great skuas Sterco-rarius skua, shags Phalacrocorax aristotelis, and common guillemots Uria aalge from colonies in the North Sea (collected 2002 to 2003) in order to compare fo...