Fatty Acid Biomarkers Research Articles

Non-carnivorous feeding in Arctic chaetognaths

Chaetognaths (arrow worms) are important components of zooplankton communities in terms of abundance, biomass and contribution to carbon export. Though traditionally considered strict carnivores, recent studies have identified “omnivorous” chaetognaths. These may feed on non-animal materials, including algae, detritus or sediments. The feeding strategies of the Arctic species Eukrohnia hamata and Parasagitta elegans are particularly interesting given differences in their vertical distributions, and the strong seasonality (peaks and troughs) in the abundance of expected prey items, such as copepods. We analyse the feeding history of these chaetognaths in the Beaufort and Chukchi Seas, and Baffin Bay, using gut contents (types and colours) as short-term signals (days), and biochemistry (stable isotope, lipid and fatty acid composition) as signals integrated over the longer-term (weeks to months), to investigate seasonality in diets and determine the extent to which animal and non-animal matter are consumed. Between November 2007 and July 2008 in the Beaufort Sea, green detritus and oil droplets were abundant in the guts of only E. hamata and were found to contain evidence of diatoms. Weak differences in apparent predation rates and prey items for the two species, but high amounts of green detritus and silica in E. hamata guts point towards direct ingestion of diatoms and marine snow at both epi- and meso-pelagic depths, and can explain δ15N and δ13C-contents that may predict omnivory in the Chukchi Sea and Baffin Bay (fall 2014). Dietary signals in P. elegans predict that this species has a reduced dependence on diatom source pathways relative to E. hamata, for instance a relative absence in green material in guts, and a lower 16:1 (n − 7) concentration. Whilst nitrogen isotopes and fatty acid biomarkers suggested a more carnivorous diet, they also suggest that Calanus copepods are less important to its diet than other types of zooplankters. We suggest that E. hamata (whether pelagic or hyper-benthic) likely receives a substantial energy input from algae and detritus and is thus not a strict carnivore. Our data provide the stimulus for continued focus on these organisms and the important role they play in carbon flux as we try to better understand carbon cycling in a changing Arctic Ocean.

Erythrocyte n-6 Polyunsaturated Fatty Acids, Gut Microbiota and Incident Type 2 Diabetes: A Prospective Cohort Study

Abstract Objectives To examine the prospective association of erythrocyte n-6 polyunsaturated fatty acid (PUFA) biomarkers with incident type 2 diabetes (T2D), and the potential role of gut microbiota. Methods 2731 non-T2D participants recruited between 2008–2013 in the Guangzhou Nutrition and Health Study were included in the present study. 276 incident T2D was ascertained after a median follow-up of 6.2 years, and 16S rRNA profiling was conducted using stool samples collected during follow-up. We examined the prospective association of erythrocyte n-6 PUFA biomarkers with incident T2D, and with diversity and composition of gut microbiota. Results Higher levels of erythrocyte γ-linolenic acid (GLA) were associated with higher T2D risk, with relative risk (quartile 4 versus 1) 1.72 (95% confidence intervals: 1.21, 2.44), adjusting for potential confounders. No association with T2D was found for erythrocyte linoleic acid or arachidonic acid. Baseline GLA was inversely associated with gut microbial richness and diversity (α-diversity, both P < 0.05) during follow-up, and significantly associated with microbiota β-diversity (P = 0.002). Seven genera (Butyrivibrio, Blautia, Oscillospira, Odoribacter, S24–7 other, Rikenellaceae other, and Clostridiales other) were enriched in quartile 1 of GLA, and in participants without T2D. Conclusions The present study suggests that erythrocyte GLA biomarker is positively associated with incident T2D in a Chinese population. High GLA status is associated with unfavorable gut microbial profiles, which may contribute to the increased risk of T2D. These results highlight that gut microbiota may play an important role linking n-6 PUFA metabolism and T2D etiology. Funding Sources This study was funded by the National Natural Science Foundation of China, Westlake University and the 5010 Program for Clinical Researches of the Sun Yat-sen University.

Omega-3 Fatty Acid Biomarkers and Sleep: Pooled Analysis of Prospective Studies in the Fatty Acids and Outcome Research Consortium (FORCE)

Abstract Objectives To assess associations between individual and total circulating n-3 fatty acids (FAs) with self-reported sleep duration and difficulty sleeping in the Fatty Acids and Outcome Research Consortium (FORCE). Methods De novo harmonized individual-level analyses were performed and pooled in 10 prospective studies (N = 22,717) with data on sleep duration and 7 studies (N = 9997) with data on difficulty initiating sleeping (DIS). Participant ages ranged from 35 to 96 years from 5 countries (Finland, Iceland, Sweden, Singapore, and the United States). Measured circulating FAs included alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), and the sum of EPA, DPA and DHA. FAs were expressed as a % of total FAs. Self-reported sleep duration was categorized as short (<7 hrs), 7–8 hrs (reference) or long (>8 hrs). DIS was categorized as yes or no (reference). Cross-sectional associations were assessed by multinomial logistic regression in each study with a standardized protocol including definitions for exposures, outcomes and covariates (demographics, health factors and dietary habits). Cohort-specific odds ratios (OR) per quintile (reference: Q1) of FAs were pooled with inverse-variance weighted meta-analysis. Results In pooled multivariate analysis, we found that participants with higher circulating n-3 FAs (Q5) had a lower risk of short and long sleep duration. For short sleep ORs (95% confidence intervals, CI) for Q5 were 0.87 (0.78–0.98) for EPA, 0.87 (0.77–0.97) for DPA, 0.83 (0.73–0.93) for DHA and 0.83 (0.74–0.93) for the sum of EPA, DPA and DHA, respectively. For long sleep ORs (95% CI) were 0.79 (0.64–0.97) for DHA, and 0.80 (0.65–0.98) for the sum of EPA, DPA and DHA. The only significant association observed for DIS was for Q3 of DHA, OR = 0.77, 95% CI = 0.63–0.96. Conclusions In pooled de novo analyses across multiple cohorts, higher levels of n-3 FAs are associated with lower risk of suboptimal sleep (i.e., too little or too much sleep); These novel findings support the need for additional investigation of the temporal nature and causality of these relationships. Funding Sources International Life Sciences Institute, North America.

Associations of Long Chain Polyunsaturated Fatty Acid Biomarkers with Affective Symptoms and Cognition in Women Beginning Chemotherapy for Breast Cancer

Abstract Objectives The objective of this research was to examine if the serum levels of long chain omega 3 fatty acids (LCn-3 FA) or long chain omega-6 fatty acids (LCn-6 FA) were associated with affective symptoms and cognition in breast cancer patients beginning chemotherapy. Methods 60 women with breast cancer were assigned to a double-blinded randomized study of minocycline vs placebo. Serum was collected from 53 women at baseline and post-chemotherapy and was stored at −80C. Serum fatty acids (FAs) from 37 pairs of samples from both time points were extracted, methylated, then analyzed using gas chromatography. Changes in fatty acids were analyzed by using paired sample t-test. Cognitive and affective behaviors were measured by Behavior Rating Inventory of Executive Function—Adult Version (BRIEF-A) test, The State-Trait Anxiety Inventory (STAI), and UCLA 3 item Loneliness Scale. Associations between baseline FAs and cognitive and affective test scores were measured by Pearson correlations; p < 0.05 was considered significant. Results Preliminary results suggest there were significant increases in the following serum FAs from baseline to post chemotherapy: C14:0 (p < 0.05) and C18:1n9 (p < 0.05), and there were significant decreases in C18:0 (p = 0.01), C20:0 (p = 0.001), and C22:5n6 (p < 0.05). Baseline analysis, prior to chemotherapy, indicated a non-significant trend for EPA (20:5n3) (r = −0.27, p = 0.06) and the n-3/n-6 ratio (r = −0.27, p = 0.06) to be correlated with better (i.e., lower) scores on the BRIEF-A test. There were trends for correlations of total n-6 FA and better (i.e., lower) STAI score (r = −0.25, p = 0.07), and total n-6 FA and better (i.e., lower) Loneliness Scale scores (r = −0.24, p = 0.09). Conclusions There was a significant change in the serum FA profile of women with breast cancer from baseline to post-chemotherapy. There were non-significant trends for n-3 FAs to be associated with better executive function, and n-6 FAs to be correlated with less anxiety and loneliness prior to beginning chemotherapy. Future research will investigate associations among serum FAs, cognitive and affective tests post-chemotherapy. Funding Sources Stephanie Spielman Breast Cancer Center – Kroger Fund OSU Comprehensive Cancer Center Pelotonia Award.

Soil microbial biomass and community responses to experimental precipitation change: A meta-analysis

The activity of soil microbes is strongly constrained by water availability. However, it is unclear how microbial activity responds to spatial and temporal changes in precipitation, particularly to long-term precipitation changes. To identify the spatiotemporal patterns of microbial responses to precipitation changes of differing durations, we conducted a meta-analysis of data from 95 field studies with drought treatments and 109 field studies with elevated precipitation treatments. Our results indicated that microbial biomass carbon (MBC) decreased by 17% under drought and increased by 18% under elevated precipitation. Across all studies, the phospholipid fatty acid (PLFA) biomarkers for fungi and bacteria decreased significantly under drought but increased under elevated precipitation. In addition, the negative effect of drought on MBC tended to be greater at sites with a high aridity index, but the effect of elevated precipitation on MBC did not differ among sites. More importantly, the responses of MBC, fungal and bacterial PLFA abundance did not vary with treatment duration under drought, but under elevated precipitation, they increased in the first five years of treatment and declined thereafter. These results are important for our prediction of microbial responses to long-term precipitation change, because they imply that microbes acclimate to long-term elevated precipitation.

Plasma fatty acids and the risk of vascular disease and mortality outcomes in individuals with type 2 diabetes: results from the ADVANCE study

Aims/hypothesisThis biomarker study aimed to quantify the association of essential and other plasma fatty acid biomarkers with macrovascular disease, microvascular disease and death in individuals with type 2 diabetes.MethodsA case-cohort study (N = 3576), including 654 macrovascular events, 341 microvascular events and 631 deaths during 5 years of (median) follow-up, was undertaken as a secondary analysis of the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified-Release Controlled Evaluation (ADVANCE) study (full details of the study design and primary endpoints of the ADVANCE trial and its case-cohort have been published previously). This current study considers new data: fatty acids measured from baseline plasma samples by proton NMR analysis. The fatty acids measured were n-3, docosahexaenoic acid (DHA), n-6, linoleic acid, and polyunsaturated, monounsaturated and saturated fatty acids. HRs were modelled per SD higher (percentage) fatty acid. C statistics and continuous net reclassification improvement were used to test the added value of fatty acids compared with traditional cardiovascular risk factors.ResultsAfter adjustment for traditional cardiovascular risk factors, an inverse association was observed for n-3 fatty acids and DHA with the risk of macrovascular events (HR [95% CI]: 0.87 [0.80, 0.95] and 0.88 [0.81, 0.96], respectively, per 1 SD higher percentage), and for n-3 fatty acids with the risk of death (HR 0.91 [95% CI 0.84, 0.99] per 1 SD higher percentage). Such associations were also evident when investigating absolute levels of fatty acids. There were no statistically significant associations between any fatty acids and microvascular disease after adjustment. However, there was limited improvement in the predictive ability of models when any fatty acid was added.Conclusions/interpretationPlasma n-3 fatty acids and DHA were found to be inversely associated with macrovascular disease, while n-3 fatty acids were also inversely associated with death. These results support the cardioprotective effects of n-3 fatty acids and DHA and further merit testing the role of high-dose supplementation with n-3 fatty acids in individuals with type 2 diabetes.Trial registrationClinicalTrials.gov NCT00145925.Graphical abstract

Threats to Rearing Juvenile Chinook Salmon from Nonnative Smallmouth Bass Inferred from Stable Isotope and Fatty Acid Biomarkers

AbstractNonnative Smallmouth BassMicropterus dolomieuare increasingly sympatric with juvenile spring Chinook SalmonOncorhynchus tshawytschain the rivers of western North America. Understanding the potential effects of introduced Smallmouth Bass is essential to efficiently direct salmon management efforts, especially given the potential for upstream range expansion of Smallmouth Bass in response to the climate‐induced warming that many rivers may experience. However, the predatory and competitive threats of Smallmouth Bass to juvenile salmonids remain largely unexamined, particularly in salmon rearing areas. To address this knowledge gap, we collected stable isotope (δ13C and δ15N) and fatty acid data to assess the trophic role of Smallmouth Bass in the upstream reaches of the North Fork John Day River, a tributary of the Columbia River where the upstream invasion extent of Smallmouth Bass co‐occurs with the native predator Northern Pikeminnow and river‐rearing juvenile Chinook Salmon. We found that Smallmouth Bass and Northern Pikeminnow occupy divergent dietary niches, and there was little evidence of a strong predation or competition threat to juvenile Chinook Salmon from either predator. In addition, we found a disproportionate reliance on autochthonous resources across the entire community and low isotopic uniqueness, suggesting potential competition among the broader fish community given the scarcity of resources. Importantly, this study focused on the overlap between the upstream‐most habitats of encroaching Smallmouth Bass and downstream‐most habitats of juvenile Chinook Salmon. Therefore, the relative scarcity of rearing salmon in comparison with other available prey in this zone may limit current predation threats. The results from this study help guide resource‐limited managers that are tasked with conserving and restoring native salmonid populations.

Growth, health and biochemical composition of the sea cucumber Cucumaria frondosa after multi-year holding in effluent waters of land-based salmon culture

Methods have been proposed to mitigate the environmental footprint of aquaculture, including co-culture of species occupying different trophic levels. In this study, sea cucumbers Cucumaria frondosa, either from production tanks fed with effluent water from land-based salmon culture over 4 yr or collected from the field, were compared using stable isotope, lipid and fatty acid (FA) signatures as indicators of waste assimilation, health and biochemical composition. Enrichment of δ13C in muscle bands and intestine and of δ15N in muscle bands, gonad and intestine was detected in captive individuals relative to wild individuals, suggesting the uptake and assimilation of waste from salmon culture. The higher levels of FA biomarkers typical of salmon feed (18:1ω9, 18:2ω6 and 20:1ω9) and lower ω3/ω6 ratio in the captive sea cucumbers were also in line with assimilation of the waste. However, male and female sea cucumbers from the co-culture became smaller with time, their organ indices were lower than those of wild individuals (e.g. poorly developed gonad), and their biochemical composition differed: triacylglycerol content was greater in wild individuals and phospholipid content was greater in captive individuals. Also, FA profiles of all tissues differed between the 2 groups, whereas total lipid in muscle bands and gonad remained similar. Overall, results support that co-culture with suspension-feeding sea cucumbers may help mitigate the salmon industry footprint. In turn, the biochemical composition of the sea cucumbers changed, and their reduced size and body indices suggest that this food source does not provide suitable nutrients to sustain growth and reproduction.

Antarctic Krill Lipid and Fatty acid Content Variability is Associated to Satellite Derived Chlorophyll a and Sea Surface Temperatures

Antarctic krill (Euphausia superba) are a key component of the Antarctic food web with considerable lipid reserves that are vital for their health and higher predator survival. Krill lipids are primarily derived from their diet of plankton, in particular diatoms and flagellates. Few attempts have been made to link the spatial and temporal variations in krill lipids to those in their food supply. Remotely-sensed environmental parameters provide large-scale information on the potential availability of krill food, although relating this to physiological and biochemical differences has only been performed on small scales and with limited samples. Our study utilised remotely-sensed data (chlorophyll a and sea surface temperature) coupled with krill lipid data obtained from 3 years of fishery-derived samples. We examined within and between year variation of trends in both the environment and krill biochemistry data. Chlorophyll a levels were positively related to krill lipid levels, particularly triacylglycerol. Plankton fatty acid biomarkers analysed in krill (such as n-3 polyunsaturated fatty acids) increased with decreasing sea surface temperature and increasing chlorophyll a levels. Our study demonstrates the utility of combining remote-sensing and biochemical data in examining biological and physiological relationships between Antarctic krill and the Southern Ocean environment.

Ontogenetic patterns in lipid and fatty acid biomarkers of juvenile polar cod (Boreogadus saida) and saffron cod (Eleginus gracilis) from across the Alaska Arctic

Characterizing the condition of fish in dynamic seasonal environments requires an understanding of their energy allocation strategies. Both polar cod (Boreogadus saida) and saffron cod (Eleginus gracilis) are important mid-trophic fish in Alaska Arctic waters, and changes in their lipid allocation could have important implications for their overwintering survival as well as their energetic value for predators. We used a combination of laboratory and field approaches to describe allometric relationships in lipid storage of polar cod and we then explored spatial patterns in field-caught juvenile gadid condition during 2012 and 2013. Lipid density in wild juvenile Arctic gadids increased with size leading into the first overwintering period, but age-1 + fish showed a reduction in lipid density with size prior to the 2nd overwintering period. Using the residuals from the underlying allometry of total lipid and fatty acid density in each species, we were able to develop a condition metric which was then explored in relation to spatial patterns in large Calanus glacialis copepodite (stages C3 and older) abundance and thermal conditions measured in the field. Fatty acid biomarkers from the total lipid pool indicated that polar cod have a higher reliance on calanoid copepods than saffron cod. Collectively, these data suggest polar cod and saffron cod will likely respond differently to regional warming depending upon the shift in the zooplankton communities, such that the energetic contribution of these fish to higher trophic levels could be transformed with future ocean warming.

Ontogenetic diet change of hadal amphipods in the New Britain Trench revealed by fatty acid biomarker and stable isotope ratio

The hadal zone (from 6 to 11 km depth) is one of the least explored habitats on Earth, and the knowledge about trophic ecology of hadal organisms is limited. Here, we analyzed fatty acid biomarker and stable isotope ratios of the amphipod species (Alicella gigantean) collected in the New Britain Trench (8225 m depth) in the southwestern Pacific Ocean. A total of 50 samples were divided into five developmental stages according to body length (1–129 cm): Stages I (juvenile), II (sub-adult) and III/IV/V (adult). Stages III, IV and V were further divided according to sex. Mean total fatty acid content for stage I (237.7 ± 105.6 mg g-1) was significantly lower than that for stages II to V (476.4 ± 49.0 mg g-1). The δ15N (14.7–18.4‰) positively correlated with the body length, whereas the EPA/DHA (C20:5ω3/C22:6ω3) ratio (0.09–0.51) negatively correlated with the body length. These results suggested an increase of trophic level with growth. Principal component analysis (PCA) separated major fatty acids into three clusters: (1) C18:1ω9, C16:1ω7, C14:1ω5 (indicative of carrion-based diet); (2) C14:0, C15:0, isoC15:0, C16:0, C17:0, isoC17:0, anteisoC17:0, C18:1ω7, C18:0, C20:1ω9, and C22:1ω9 (bacteria/zooplankton-based diet); and (3) C20:4ω6, C20:5ω3, C22:6ω3 and C22:5ω6 (benthic fauna/algae-based diet). The PCA result revealed that stage I-individuals consumed more bacteria/zooplankton debris, stages II to IV-individuals primarily preyed on carrion, while stage V-individuals had more diverse diet (benthic fauna/algae and carrion). Female amphipods had higher proportions of monounsaturated fatty acids, lower proportions of polyunsaturated fatty acids, and higher δ15N compared to male amphipods, suggesting that female individuals rely more on carrion from higher trophic organisms. This sex-related difference, however, diminished from stage III to V. Overall, our fatty acid and stable isotope data suggest an ontogenetic diet shift for hadal amphipods that may contribute to their success in the deepest ocean.

Transition in the isotopic signatures of fatty-acid soil biomarkers under changing land use: Insights from a multi-decadal chronosequence

The effects of climate warming on soil erosion in upland ecosystems will be disproportionately higher than for lowlands due to steeper topography and higher predicted rainfall. Soil erosion may be enhanced by climate warming and upslope shifts in agriculture as conditions for plant growth improve. Identification of eroded-soil sources will inform land management practices that mitigate soil loss and impacts on aquatic receiving environments. Isotopic signatures of plant-derived fatty acid (FA) soil biomarkers can discriminate sediment sources and will detect shifts in land use and natural vegetation toposequences. Accounting for these isotopic shifts requires knowledge of the magnitude and time scale for transition in biomarker signatures. We examined a 30-year chronosequence to quantify the transition in isotopic values of bulk nitrogen, carbon and FA biomarkers following a change from pine forestry to pastoral agriculture in the central North Island of New Zealand. We found the transition in soil biomarker isotopic values was complete within 6 years, with substantial increases in both organic carbon (1% yr−1) and total N (0.13% yr−1) of top soils. Subsequent changes were negligible (i.e., <0.04% yr−1), indicative of a new steady state. Similar patterns were observed in the isotopic signatures of bulk δ13C and δ15N values and FA δ13C values (i.e., ±0.5–0.6‰ yr−1). Bulk C and N properties and the FAs C14:0, C16:0, C18:2, C24:0 and C26:0 displayed clear transitions from harvested pine to mature pasture. We found evidence that mycorrhizal fungi could disperse and influence soil FA isotopic signatures. This highlights the need to consider both harvested and mature forests in source-tracing studies. Finally, our study shows that near-instantaneous changes in land use associated with agriculture can alter the isotopic signatures of plant biomarkers in soils. This produces a step change that can be readily detected in sedimentary records.

Fatty acids elucidate sub-Antarctic stream benthic food web dynamics invaded by the North American beaver (Castor canadensis)

Despite being remote, polar and sub-polar regions are increasingly threatened by global ecological change. For instance, South America’s sub-Antarctic forest ecoregion is considered one of the world’s last wilderness areas and a global reference site for pre-Industrial Revolution nutrient cycles. Nonetheless, the North American beaver (Castor canadensis) was introduced to Tierra del Fuego in 1946 and, as an invasive ecosystem engineer, has transformed the ecology of regional watersheds. Beavers’ engineering activities transform forested streams (FS) into beaver ponds (BP), where there is greater light and primary production (allochthonous organic matter) and, consequently, increased basal resource quality. To investigate this, we analyzed algal, diatom, fungal and bacterial fatty acid (FA) biomarkers in three basal resource categories (biofilm, very fine benthic organic matter, coarse benthic organic matter) and benthic consumers from four functional feeding groups (FFG). The amphipod Hyalella spp. was chosen as an indicator species due to its abundance and biomass in both habitats. Hyalella spp. had higher proportions of algal and bacterial FA in BP than FS. In FS, Hyalella spp. (gatherer) and Gigantodax spp. (filterer, Diptera) had greater contributions of higher quality FA (higher in polyunsaturated FA), while Rheochorema magallanicum (predator, Trichoptera) and Meridialaris spp. (scraper, Ephemeroptera) showed lower quality monounsaturated and saturated FA. All FFGs showed evidence of microbial FA and had higher levels of autochthonous FA biomarkers than their food resources. Scrapers had the greatest proportion of autochthonous FA. These data provide new insights into the utilization of basal resources by stream consumers in sub-Antarctic streams and how beavers modify these ecosystems.

Omega-3 fatty acid supplementation in pregnancy-baseline omega-3 status and early preterm birth: exploratory analysis of a randomised controlled trial.

To identify a polyunsaturated fatty acid (PUFA) biomarker able to detect which women with singleton pregnancies are most likely to benefit from omega-3 supplementation to reduce their risk of early preterm birth. Exploratory analysis of a randomised controlled trial. Six Australian hospitals. Women with a singleton pregnancy enrolled in the ORIP trial. Using maternal capillary whole blood collected ~14weeks' gestation, the fatty acids in total blood lipids were quantified using gas chromatography. Interaction tests examined whether baseline PUFA status modified the effect of omega-3 supplementation on birth outcomes. Early preterm birth (<34weeks' gestation). A low total omega-3 PUFA status in early pregnancy was associated with a higher risk of early preterm birth. Among women with a total omega-3 status ≤4.1% of total fatty acids, omega-3 supplementation substantially reduced the risk of early preterm birth compared with control (0.73 versus 3.16%; relative risk=0.23, 95% confidence interval [CI] 0.07-0.79). Conversely, women with higher total omega-3 status in early pregnancy were at lower risk of early preterm birth. Supplementing women with a baseline status above 4.9% increased early preterm birth (2.20 versus 0.97%; relative risk=2.27, 95% CI 1.13-4.58). Women with singleton pregnancies and low total omega-3 PUFA status early in pregnancy have an increased risk of early preterm birth and are most likely to benefit from omega-3 supplementation to reduce this risk. Women with higher total omega-3 status are at lower risk and additional omega-3 supplementation may increase their risk. Low total omega-3 fat status helps identify which women benefit from extra omega-3 to reduce early prematurity.

Using fatty acid markers to distinguish between effects of salmon ( Salmo salar ) and halibut ( Hippoglossus hippoglossus ) farming on mackerel ( Scomber scombrus ) and whiting ( Merlangius merlangus )

Presence of coastal aquaculture activities in marine landscapes is growing with impacts on the wild fish that share these habitats. However, it is difficult to disentangle subsequent ecological interactions between these activities and marine fish communities. We evaluated the impact of both salmon and halibut farms on mackerel (Scomber scombrus) and whiting (Merlangius merlangus) sampled near sea cages using condition indices and fatty acid (FA) biomarkers. Results of the stomach content analysis indicated that mackerel and whiting consumed waste feed which was also reflected in their modified FA profiles. Both mackerel and whiting had elevated levels of FAs that are of vegetable oils origin. The use of vegetable oils as replacement for marine oils is a lot more common in salmon farming than halibut farming. Additionally, the overall effects of the two fish farms were more pronounced in whiting than in mackerel sampled near the sea cages. By allowing discrimination between sources of trophic interactions, this method could lead to more informed decisions in managing different farming activities.

Sterol, fatty acid, and lignin biomarkers identify the response of organic matter accumulation in Englebright Lake, California (USA) to climate and human impacts

Climate change is one of the biggest challenges facing humankind. Higher temperatures and changes in precipitation will lead to a greater frequency of drought, wildfire, and intense storms that will threaten systems already vulnerable to climate and anthropogenic change. These threats will transform carbon delivery across the terrestrial–aquatic interface. This study investigated how anthropogenic activities and climate influence organic carbon delivery using Englebright Lake, a reservoir in California, as a model system. Organic carbon accumulation in three depositional settings (bottomset, foreset, topset) was analyzed using fatty acid, sterol and lignin biomarkers and compared to records of watershed events to determine responses to dam construction, mining impacts and flood events. Concentrations of long chain saturated fatty acids, plant sterols, epi-brassicasterol/brassicasterol and lignin biomarkers increased by an order of magnitude in foreset deposits in response to flood events (p < 0.007 for each biomarker). Hydraulic mining for gold was recorded as near-zero concentrations of terrigenous biomarkers in topset deposits, whereas decreases in diacids coincident with increases in aquatic sterols in bottomset deposits reflected the response to dam construction (p < 0.007 for each biomarker). Organic carbon accumulation was controlled by event magnitude and duration, and climate-driven event signals were up to an order of magnitude larger than anthropogenic-driven event signals. These data demonstrate the importance of understanding the depositional environment because the ability to characterize three different depositional settings in Englebright Lake enabled us to identify the smaller anthropogenic signals that would have been obscured by the much larger response to climate events.

Meiobenthos as food for farmed shrimps in the earthen ponds: Implications for sustainable feeding

Shrimp farming in earthen pond is one of the largest seafood growing industries among coastal mariculture, but it has faced environmental issues in recent years, e.g. overloading of supplementary feed cause deterioration of pond environments. In order to assess the impact of pond shrimp farming on the benthic environment, we investigated the changes in environmental variables and meiobenthic community structure during January to August in the earthen ponds rearing Marsupenaeus japonicus and Litopenaeus vannamei. Water and sediment samples were taken in January (before aquaculture), May (early stage) and August (late stage). We found sedimentary redox potential showed values below −150 mV in all ponds in the early and late rearing stages, indicating overall reduced and anoxic conditions. Sedimentary bulk organic matter (total nitrogen and organic carbon) accumulated along with the feeding addition during the rearing period. We found meiobenthic community structure to change over different rearing stages mainly because of an increase in nematode densities that was associated with shrimp farming activity in the studied ponds. We also investigated the functional roles of pond biota and supplementary feed by studying the benthic food web in these ponds by means of natural stable isotope ratios of carbon and nitrogen and fatty acid biomarkers in the early (May) and late (August) rearing stages. Pond biota (i.e. microalgae and meiobenthos) contributed abundantly to the diets of the two shrimp species. In the early stage, meiobenthos shared similar diets with shrimps (with both feeding on primary organic sources) and they could thus potentially compete for resources. At late rearing stages, meiobenthos represented however a functional link between primary producers and shrimps, serving as nutritional food sources for shrimp and providing them high amounts of polyunsaturated fatty acids (PUFAs). We found that the supplementary feed was not substantially consumed by the two shrimp species, which might pose an overfeeding threat to deteriorate the pond environment.

An annually resolved record of Western European vegetation response to Younger Dryas cooling

The regional patterns and timing of the Younger Dryas cooling in the North Atlantic realm were complex and are mechanistically incompletely understood. To enhance understanding of regional climate patterns, we present molecular biomarker records at subannual to annual resolution by mass spectrometry imaging (MSI) of sediments from the Lake Meerfelder Maar covering the Allerød-Younger Dryas transition. These analyses are supported by conventional extraction-based molecular-isotopic analyses, which both validate the imaging results and constrain the sources of the target compounds. The targeted fatty acid biomarkers serve as a gauge of the response of the local aquatic and terrestrial ecosystem to climate change. Based on the comparison of our data with existing data from Meerfelder Maar, we analyse the short-term environmental evolution in Western Europe during the studied time interval and confirm the previously reported delayed hydrological response to Greenland cooling. However, despite a detected delay of Western European environmental change of ∼135 years, our biomarker data show statistically significant correlation with deuterium excess in Greenland ice core at ∼ annual resolution during this time-transgressive cooling. This suggests a coherent atmospheric forcing across the North Atlantic realm during this transition. We propose that Western European cooling was postponed due to major reorganization of the westerlies that were intermittently forcing warmer and wetter air masses from lower latitudes to Western Europe and thus resulted in delayed cooling relative to Greenland.

The basal food sources for Murray cod (Maccullochella peelii) in wetland mesocosms

The use of freshwater for human consumption and agriculture has resulted in many wetland ecosystems being some of the most seriously impacted ecosystems in the world. In attempts to rehabilitate wetland ecosystems environmental flows are used to restore parts of the hydrological regime altered by human water use. The use of environmental water intends to improve ecosystem health, but frequently aims to have specific outcomes for populations of higher-order consumers such as iconic fish and bird species. To date, research and monitoring has mainly focused on understanding ‘flow-ecology’ relationships, without investigating the mechanisms underlying them. We sought to understand the importance of different basal food sources to the growth of the endangered Murray cod in temporary wetland systems using fatty acid biomarkers. We flooded replicate mesocosms with two different wetland soils to produce sufficient zooplankton prey to sustain and grow Murray cod larvae for approximately 2 weeks. The fatty acid profiles of Murray cod and percentages of different biomarkers were compared at the start and finish of the experiment and our results suggest that the most important basal food source is green algae. However, the biomarkers of diatoms, cyanobacteria and bacteria also increased and differed between wetlands with different hydrological regimes. It is unclear if our results can be extended to other wetland systems and we encourage further research both into the relationship between length of wetland flooding and invertebrate densities in other systems. We also encourage research into the mechanistic pathways in which green algae carbon is transferred through food webs to higher order consumers in wetland systems to help generalise our results to other wetlands and support the management of wetlands through the timing and duration of flooding from environmental water.

Dietary versus nondietary fatty acid profiles of lake trout ecotypes from Lake Superior and Great Bear Lake: Are fish really what they eat?

Fatty acids are well-established biomarkers used to characterize trophic ecology, food-web linkages, and the ecological niche of many different taxa. Most often, fatty acids that are examined include only those previously identified as “dietary” or “extended dietary” biomarkers. Fatty acids considered as nondietary biomarkers, however, represent numerous fatty acids that can be extracted. Some studies may include nondietary fatty acids (i.e., combined with dietary fatty acids), but do not specifically assess them, whereas in other studies, these data are discarded. In this study, we explored whether nondietary biomarker fatty acids can provide worthwhile information by assessing their ability to discriminate intraspecific diversity within and between lakes. Nondietary fatty acids used as biomarkers delineated variation among regions, among locations within a lake, and among ecotypes within a species. Physiological differences that arise from differences in energy processing can be adaptive and linked to habitat use by a species’ ecotype and likely explains why nondietary fatty acid biomarkers can be a relevant tool to delineate intraspecific diversity. Little is known about the nondietary-mediated differences in fatty acid composition, but our results showed that nondietary fatty acid biomarkers can be useful tool in identifying variation.