0000000000458477
AUTHOR
Sami Taipale
Inferring phytoplankton community composition with a fatty acid mixing model
Abstract. 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 profiles from monocultures of chlorophytes, cyanobacteria, diatoms, euglenoids, dinoflagellates, raphidophyte, cryptophytes and chrysophytes were used as a reference library to infer phytoplankton community composition in five moderately humic, large boreal lakes in three different seasons (spring, summer and fall). The phytoplankton commu…
Metabolic plasticity of mixotrophic algae is key for their persistence in browning environments
Light availability is the main regulator of primary production, shaping photosynthetic communities and their production of ecologically important biomolecules. In freshwater ecosystems, increasing dissolved organic carbon concentrations, commonly known as browning, leads to lower light availability and the proliferation of mixotrophic phytoplankton. Here, a mixotrophic algal species (Cryptomonas sp.) was grown under five increasing dissolved organic carbon concentrations to uncover the plastic responses behind the success of mixotrophs in browning environments and their effect in the availability of nutritionally important biomolecules. In addition to the browning treatments, phototrophic, …
Vertical stratification of bacteria and archaea in sediments of a small boreal humic lake
ABSTRACT Although sediments of small boreal humic lakes are important carbon stores and greenhouse gas sources, the composition and structuring mechanisms of their microbial communities have remained understudied. We analyzed the vertical profiles of microbial biomass indicators (PLFAs, DNA and RNA) and the bacterial and archaeal community composition (sequencing of 16S rRNA gene amplicons and qPCR of mcrA) in sediment cores collected from a typical small boreal lake. While microbial biomass decreased with sediment depth, viable microbes (RNA and PLFA) were present all through the profiles. The vertical stratification patterns of the bacterial and archaeal communities resembled those in mar…
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-1 day-1) of ω-3 and ω-6 PUFA varied among six different phytoplankton main groups (16 freshwater strains) and between exponential and stationary growth phase. EPA and DHA concentrations, as dry weight, were similar among cryptophytes and diatoms. However, Crypto…
Effects of progressive decrease of feeding frequency and re-feeding on production parameters, stomach capacity and muscle nutritional value in rainbow trout (Oncorhynchus mykiss)
Feeds and feeding constitute the major part of costs in intensive aquaculture. Any action to reduce feeding costs without negatively affecting fish production parameters and flesh quality would improve profitability of farming. Therefore, we studied the effects of feeding frequency on production parameters, stomach capacity and nutritional value of muscle in juvenile rainbow trout (Oncorhynchus mykiss) in an experiment with two stages. First, during the nine-week “starvation period” we fed rainbow trout (initial weight c. 40 g) with four different feeding protocols in an attempt to adapt the fish to a progressive decrease in the number of feeding days. During the second stage, a four-week “…
Periphyton as a key diet source of essential fatty acids for macroinvertebrates across a nutrient and dissolved organic carbon gradient in boreal lakes
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 (DOC) and nutrient (phosphorus and nitrogen) concentrations. We also analyzed fatty acid (FA)-specific stable carbon isotopes (δ13CFA) to investigate the dietary origin (periphyton vs. terrestrial organic matter) of PUFA in the consumers. In contrast to periphyton, terrestrial organic matter was deprived of long-chain PUFA, such as eicosapentaenoic a…
Planktivorous vendace (Coregonus albula) utilise algae-derived fatty acids for biomass increase and lipid deposition
Spatial and seasonal variation in the abundance and composition of phytoplankton and other basal resources (bacteria, terrestrial detritus) influence the availability of essen-tial 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 (Coregonus albula) muscle tissue during the summer feeding period (May to late September) in six boreal lakes. Vendace muscle fatty acid content increased from ~17.7 mg/g DW to ~28.1 mg/g DW from spring to summer, corresponding to a ~59% increase in total fatty acids. PUFA accounted for 45%–65% of all fatty acids, and the most abundant fatty acid …
Bacterial-mediated terrestrial carbon in the foodweb of humic lakes
Sami Taipale tarkasteli tutkimuksessaan metaanin merkitystä humusjärvien ravintoketjussa. Suurin osa Suomen järvistä lukeutuu humusjärviin, jotka ovat väriltään ruskehtavia. Koska metaani on 21 kertaa tehokkaampi kasvihuonekaasu kuin hiilidioksidi, on sen kohtalolla järvissä sekä järvien ravintoketjussa suuri merkitys ilmastonmuutoksen kannalta. - Metaania hapettavilla bakteereilla on merkittävä rooli humusjärvien ravintoketjussa, mutta myös globaalisti, sillä ne estävät suurelta osin voimakkaan kasvihuonekaasun, metaanin, pääsyn ilmakehään. Metaania hapettavien bakteerien merkitys korostunee tulevaisuudessa ilmaston lämmetessä, Taipale täsmentää. Uudet tutkimusmenetelmät, kuten vakaiden is…
Filtration of Nordic recirculating aquaculture system wastewater : Effects on microalgal growth, nutrient removal, and nutritional value
Microalgal bioremediation of recirculating aquaculture system (RAS) wastewater represents an alternative for wastewater treatment with the potential to generate valuable biomass. This study evaluated the effects of removing biological contamination and suspended solids from Nordic area RAS wastewater through filtration with 0.45 μm filters on the performance and nutritional value of microalgae. All three tested green microalgae (Haematococcus pluvialis, Monoraphidium griffithii, and Selenastrum sp.) were able to grow in raw (unfiltered) and filtered RAS wastewater. Cultivation in raw RAS wastewater decreased the ω-3 and ω-6 fatty acid content of H. pluvialis as compared to filtered wastewat…
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. We examine global trends of browning and DOM/DOC, and the use of remote sensing as a tool to investigate browning from local to global scales. Studies have focused on lakes and rivers while seldo…
Differing Daphnia magna assimilation efficiencies for terrestrial, bacterial, and algal carbon and fatty acids
There is considerable interest in the pathways by which carbon and growthlimiting 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 terrestrial organic matter are potential trophic resources for zooplankton, especially in those receiving high terrestrial organic matter inputs. We therefore tested carbon, nitrogen, and fatty acid assimilation by the crustacean Daphnia magna when consuming these resources. We fed Daphnia with monospecific diets of high-quality (Cryptomonas marssonii) an…
Assessment of microalgae species, biomass, and distribution from spectral images using a convolution neural network
AbstractEffective monitoring of microalgae growth is crucial for environmental observation, while the applications of this monitoring could also be expanded to commercial and research-focused microalgae cultivation. Currently, the distinctive optical properties of different microalgae groups are targeted for monitoring. Since different microalgae can grow together, their spectral signals are mixed with ambient properties, making estimations of species biomasses a challenging task. In this study, we cultured five different microalgae and monitored their growth with a mobile spectral imager in three separate experiments. We trained and validated a one-dimensional convolution neural network by…
Original data for article: Filtration of Nordic recirculating aquaculture system wastewater: effects on microalgal growth, nutrient removal and nutritional value
The data processed and analyzed in this study is divided if five files: Growth_and_Nutrient_removal.txt, FA_concentration.txt, FA_proportion.txt, AA_concentration.txt and AA_proportion.txt. For detailed descriptions of the motives, methods and results of the study, see the article.