Algal Composition Research Articles

Algal Diversity and Water Quality Assessment During Summer in Some Suburban Water Bodies of Lucknow, Uttar Pradesh

Freshwater algae can tolerate wide range of environmental stress and grow naturally in mixed communities. In the present study diversity of algae has been studied in some suburban water bodies near Lucknow, which revealed the occurrence of 32 genera and 40 taxa under four phyla - Cyanophyta, Chlorophyta, Bacillariophyta and Euglenophyta. It is observed that heavy anthropogenic activities and low water level in late summer resulted in accumulation of pollutants which affected the algal species composition. The polluted water with high conductivity and total dissolved solids (TDS) showed the dominance of Cyanophyta and Bacillariophyta whereas most of Chlorophyta and few Bacillariophyta were found in less polluted water with low conductivity and TDS. Taxa Centritractus belonophorus belonging to Xanthophyta is being reported for the first time from Uttar Pradesh. The study also recorded for the first time several algal taxa from these water bodies of Lucknow.

Fatty Acid Composition and Biological Activity of Supercritical Extracts from Arctic Brown Algae Fucus vesiculosus

The fatty acid composition of arctic brown algae was studied using supercritical (SC) fluid extraction. A method for fractionating the SC extract based on the differences in the solubility of its components (fatty acids, polyphenols) was proposed. The composition and biological activity of the fractions were studied.

Use of soil biota in the assessment of the ecological potential of urban soils

In assessing the ecological conditions and classification of urban soils, data about soil biota should be taken into account. The environment of urban territories is characterized by significant changes compared to their surrounding environments. It is established that the algal flora of urban soils lose their zonal features and features associated with the edification influence of higher plants. Specific biotopes with a definite species structure are formed in urboecosystems. Fifty 50 algae species have been recorded in the soils of the Henichesk urboecosystems (Kherson region, Ukraine): Cyanoprocaryota – 21, Chlorophyta – 13, Charophyta – 2, Eustigmatophyta – 1, Xanthophyta – 11, Bacillariophyta – 2. Among dominant and subdominant species were Cyanoprocaryota and Chlorophyta. The other phyla were represented by Klebsormidium dissectum, K. flaccidum, Hantzschia amphioxys, Eustigmatos magnus, Botrydiopsis eriensis. Compared with the surrounding environment, the urbanized flora of Henichesk has a low species richness, and is characterized by prevalence of Cyanoprocaryota and Chlorophyta species. The coefficient that takes into account the percentage of preservation of species richness in a particular urban area compared to the background indicators of species richness can be used to evaluate the urban transformation of soil biota. The degree of degradatory changes in the composition of living organisms and the direction of these changes depends on the specificity and intensity of exploitation of the territory of the urban ecosystem. The most diverse composition of algae species within the the city of Henichesk was noted in the recreational, residential, and transport zones, in comparison with the industrial zone and the zone of special use. Different functional areas of the city are distinguished not only by the algae species richness, but also by the composition of dominants. Among the dominants and subdominants of the recreational and transport zones were species of different phyla. The dominants and subdominants of the residential and industrial zones were Cyanoprocaryota species, in the zone of special use – representatives of Chlorophyta. The distribution of species richness of algae along the soil profile in the city acquires an atypical character. The species richness increases not in the most superficial layers of soil, but in the lower, aphotic parts of the soil profile. The soil biota, on the one hand, depends on the ecological conditions of soil, and on the other as a result of its life activity, changes the ecological functions of the soil, strengthening or weakening them. The reduction in the species richness of the soil algae of the urboecosystem Henichesk shows the limitations of ecological functions of urban soils. It is established that changes in the composition of algae in soils of urban ecosystems are one of the indicators of the presence and severity of transformation processes. These processes occur with the soil biota and soil as a whole under the conditions of urban ecosystems and can be used as indicators in the environmental assessment of urban soils, in the development and subsequent examination of ways to reduce negative expression of urbanization.

Epilithic Diatom Composition and Some Physico-Chemical Parameters of the Streams in the Çoruh Basin (Turkey)

Epilithic algae are very important for the nutritional chain for lotic ecosystems. It is also included in the group that should be examined in order to determine biodiversity in aquatic ecosystems. For this purpose, this study has been carried out in the Yagli, Mulk, Sirakonaklar and Kocunbogazi streams, which are located in the Coruh Basin. The streams’ altitude of (1730-2350 m), depth of (13.0 - 45.6 cm), water temperature of (6.20 - 8.10 °C), dissolved oxygen of (8.8-9.4 mg l−1), pH of (6.60-8.10), nitrite of (0.009 - 0.020 mg l−1,) and nitrate values of (0.50 - 2.26 mg l−1,) were determined. In the study, 17 taxa belonging to the Bacillariophyta group were detected. Cymbella affinis Kutz, Encyonema minutum (Hilse) D.G. Mann, Hannaea arcus (Ehrenberg) R.M.Patrick and Ulnaria ulna (Nitzsch) Compere species were found to be distributed throughout all streams. In particular, it was determined that Hannaea arcus (Ehrenberg) R.M.Patrick species was the highest quantitatively in the Yagli stream. It was determined that the streams have an oligotrophic character in terms of water quality and epilithic algal composition.

The use of algae in animal nutrition

In this review article the use of algae as feed in animal nutrition is being examined. The algae evolved on earth 3.5 billion years ago. They are primitive, generally aquatic and photosynthetic organisms, which range in size from 0,2-2,0 μιτι in diameter -microalgae (phytoplankton) up to 60 m length- macroalgae and may divide once or more per day. Algae are classified using a combination of characteristics in the chlorophyta, phaeophyta, chrysophyta, rhodophyta (all of them are macroalgae), pyrrhophyta and cyanophyta (they are microalgae). The chemical composition of algae varies over a wide range and depends on environmental conditions. Algae are necessary in the reduction of greenhouse gas emissions. They can be used as biodisel from their bio-lipid oil, as feed additives (alginates, carrageenans, agar, pigments), as therapeutic agents, as cosmetics, as organic fertilizer. Moreover, edible algae are considered sources of minerals and a complementary source of food protein for human -especially infunctional foods and animal nutrition, both in ruminants and monogastric animals. Algae in the rations of lactating cows increased milk production, the average milk protein, the amount of lactose, and prolonged the lactation period, while algae rich in (n-3) fatty acids effected positively on this fatty acid content of milk. In calves the dietary algae en-hanced immune function and improved carcass characteristics. Regarding the ewes, the algae nutrition affected milk fat composition and their dairy products. Researches on monogastric animals showed that the dietary supplementation of algae rich in docosqexaenoic acid increased its content in muscle tissue of rabbits, heavy pigs (live weight around 160 kg) and in the egg yolk of laying hens. In addition, algae in poultry diets can be used effectively as pigment sources both in egg yolk and in broiler skin and shanks. Algae have been found also to be a valuable food for fish farmed by acquaculture. However, further investigation is needed concerning the use of algae in human and animal nutrition.

Post-pyrogenic changes in vegetation cover and biological soil crust in steppe ecosystems

The study of the processes of restoration of species richness and productivity of steppe ecosystems after fires is an urgent problem that affects not only the conservation of biodiversity but also the maintenance of pasture resources. This article presents the results of a study of post-pyrogenic effects in steppe ecosystems, taking into account changes in the species composition of cyanoprokaryotes and algae that are art of the biological soil crust, which performs ecologically important functions in xerophytic ecosystems. The investigations were carried out in virgin and post-pyrogenic steppe ecosystems of the “Troitsk Clough” reserve (Zaporizhia region, Ukraine). For three years, the dynamics of the projective cover and the height of the vegetation cover in virgin areas of herbs-fescue-feather-grass and fescue-feather-grass steppes was studied as well as within two ecosystems of post-pyrogenic development after fires that occurred in the spring and winter periods. We discovered that restoration of the herbs-fescue-feather-grass and fescue-feather-grass steppes after fires occurs at different rates. The cause of the slow restoration of vegetation cover can be its severe damage by fire at the beginning of the vegetation season and the development of erosion processes. The number of species of cyanoprokaryotes and algae in the biological soil crust of virgin and post-pyrogenic ecosystems is not significantly different. It varies from 35 to 49 species. The greatest diversity is noted for Cyanoprokaryota. Chlorophyta is in the second place. Among the dominants, the filamentous forms of Cyanoprokaryota prevail. Nostoc edaphicum was noted as a nitrogen fixing representative. The similarity of the species lists of cyanoprokaryotes and algae of post-pyrogenic and virgin ecosystems, according to the calculated Jaccard coefficient, varies from 49.1% to 55.3%. This indicates a strong specificity of the composition of cyanoprokaryotes and algae in post-pyrogenic biological soil crusts. Changes in their composition reflect different stages of post-pyrogenic succession. In the first year after a fire, there is a slight increase in species richness, which is a consequence of the favorable effect of increasing the amount of mineral substances in the soil after the organic matter has burned out. The “pioneer” group includes: Phormidium autumnale, Ph. dimorphum, Ph. retzii, Ph. (Leptolyngbya) henningsii, Luticola mutica, Hantzschia amphioxys. Gradually this effect is leveled and the species richness of cyanoprokaryotes and algae is stabilized at a level peculiar for this type of ecosystem.

Production of Methane From Microalgae Biofilms Growing in Wastewater Treatment Plants in the Canary Islands

Two recurrent topics among the scientific community are the use of microalgae in wastewater treatment plants as a biological agent for nutrient removal, and, more recently, the use of microalgae for biofuel production. In this study we have analysed the possibility of coupling these two processes, using microalgae that naturally form biofilms on wastewater treatment tanks to produce methane. The proposal is to develop a low cost, environmental friendly methodology, with the economical and environmental advantages of enhancing the removal of nutrients from wastewater, and producing sustainable biofuel. A methane assay using microalgae biofilms from the primary and secondary treatment tanks from a wastewater treatment plant (WWTP) on the Canary Islands (EDAR-del Sureste, Gran Canaria, Spain) showed that, when this substrate is added to a suitable methanogenic bacteria, in this case marine sludge from a fish farm, it gives a methane yield of 0.104 Nm3 kg-1 VS. We also checked the in situ biomass yield of the biofilm (3.16 g AFDW m-2 d-1 and 7.71 g AFDW m-2 d-1, for the primary tank and secondary tank respectively), and the growth of this biofilms in photobioreactors (PBR). When grown in PBR, the algae composition of biofilm from the primary tank becomes dominate by a unicellular chlorophyta and produces 0.24 kg AFDW m- 3 d-1 of biomass; while biofilm from the secondary tank becomes dominated by the filamentous chlorophyta Stigeoclonium, and has a biomass yield of 0.48 kg AFDW m-3 d-1. The biofilms growing the WWTP of the EDAR del Sureste, in Gran Canaria, are a free naturally available source of biomass, and we have shown in this study that this biofilm, besides being used as a natural agent for nutrient removal in a WWTP, it has also the potentialof being used as a low cost, green source of biomass for methane production.

Ecological and commercial implications of temporal and spatial variability in the composition of pigments and fatty acids in five Irish macroalgae

Seaweed habitats are characterised by constantly fluctuating environmental conditions which can influence the biochemical composition of species. To quantify the natural variability in concentrations and composition of pigments and fatty acids, a seasonal and spatial analysis of ecologically and economically important seaweed species (Fucus serratus, Ascophyllum nodosum, Himanthalia elongata, Laminaria digitata and Palmaria palmata) from Ireland was undertaken. Results revealed both common and species-specific patterns in seasonal and spatial algal composition. Generally, pigment concentrations decreased during summer months and were associated with a higher ratio of xanthophylls to chlorophylls. A similar response was observed regarding the proportions of polyunsaturated fatty acids (PUFA) which also decreased during summer. Concentrations in total fatty acids (TFA) revealed two distinct patterns in the five species investigated. In the two fucoid species, an increase in TFA during summer months was positively correlated with high proportions of monounsaturated fatty acids, implying an accumulation of storage lipids; in the remaining three species, proportions of PUFA were highest during winter and generally followed the seasonal trends of TFA. On a larger, geographical, scale, results demonstrated an influence of sampling location on pigments and fatty acids. Results highlight the complexity of interacting seasonal, spatial and species-specific drivers determining the biochemical composition of seaweeds which influences their value as food source and should be considered when natural stocks are harvested for high-value commercial applications.

Crude fucoidan content in two North Atlantic kelp species, Saccharina latissima and Laminaria digitata\u2014seasonal variation and impact of environmental factors

Fucoidans are sulphated fucose-rich polysaccharides predominantly found in the cell walls of brown algae. The bioactive properties of fucoidans attract increasing interest from the medico-pharmaceutical industries and may drive an increase in demand of brown algae biomass. In nature, the biochemical composition of brown algae displays a seasonal fluctuation driven by environmental factors and endogenous rhythms. To cultivate and harvest kelps with high yields of fucoidans, knowledge is needed on seasonal variation and impact of environmental conditions on the fucoidan content of brown algae. The relations between the fucoidan content and key environmental factors (irradiance, nutrient availability, salinity and exposure) were examined by sampling natural populations of the common North Atlantic kelps, Saccharina latissima and Laminaria digitata, over a full year at Hanstholm in the North Sea and Aarhus in the Kattegat. In addition, laboratory experiments were carried out isolating the effects of the single factors. The results demonstrated that (1) seasonal variation alters the fucoidan content by a factor of 2–2.6; (2) interspecific differences exist in the concentrations of crude fucoidan (% of dry matter): L. digitata (11%) > S. latissima (6%); and (3) the effects of single environmental factors were not consistent between species or between different conspecific populations. The ambiguous response to single environmental factors complicates prospective directions for manipulating an increased content of fucoidan in a cultivation scenario and emphasizes the need for knowledge on performance of local kelp ecotypes.

Developing a two-step method for retrieving cyanobacteria abundance from inland eutrophic lakes using MERIS data

Cyanobacteria are the main dominant species in inland eutrophic lakes during algae blooms, and measures of cyanobacteria abundance can be used for monitoring and early detection of algal blooms by remote sensing. During May 2013 and August 2016, a total 137 water samples were collected from Lake Taihu and Lake Chaohu. Remote-sensing reflectance was measured, surface water was collected in the field, and chlorophyll-a concentration, phycocyanin concentration, suspended-matter concentration and phytoplankton pigment absorption parameters were measured in the laboratory. The composition and density of planktonic algae were also detected by microscope examination. The remote-sensing reflectance at 15 MERIS bands was simulated based on our measured spectral data, and a two-step method for detecting cyanobacteria abundance using the partial least squares model based on 5 MERIS bands was developed. The results showed that the estimation algorithm can predict cyanobacteria abundance in inland eutrophic lakes with satisfactory accuracy, with RMSE of 7.56 and MAPE of 13.44 %. This algorithm was successfully applied to the MERIS image acquired on August 12, 2010, and showed a reasonable spatial distribution of cyanobacteria abundance in Lake Taihu. It demonstrated that the developed estimation method was an effective way to monitor cyanobacteria abundance in water with a potential to be successfully applied to Sentinel-3 images.

Local adaptation along an environmental cline in a species with an inversion polymorphism

Polymorphic inversions are ubiquitous across the animal kingdom and are frequently associated with clines in inversion frequencies across environmental gradients. Such clines are thought to result from selection favouring local adaptation; however, empirical tests are scarce. The seaweed fly Coelopa frigida has an α/β inversion polymorphism, and previous work demonstrated that the α inversion frequency declines from the North Sea to the Baltic Sea and is correlated with changes in tidal range, salinity, algal composition and wrackbed stability. Here, we explicitly test the hypothesis that populations of C.frigida along this cline are locally adapted by conducting a reciprocal transplant experiment of four populations along this cline to quantify survival. We found that survival varied significantly across treatments and detected a significant Location x Substrate interaction, indicating local adaptation. Survival models showed that flies from locations at both extremes had highest survival on their native substrates, demonstrating that local adaptation is present at the extremes of the cline. Survival at the two intermediate locations was, however, not elevated at the native substrates, suggesting that gene flow in intermediate habitats may override selection. Together, our results support the notion that population extremes of species with polymorphic inversions are often locally adapted, even when spatially close, consistent with the growing view that inversions can have direct and strong effects on the fitness of species.

Algae pyrolytic poly-generation: Influence of component difference and temperature on products characteristics

Pyrolytic poly-generation of three algae (Enteromorpha prolifera (EP), Spirulina platensis (SP) and Nannochloropsis sp. (NS)) was carried out in a fixed bed reactor and pyrolysis mechanism was explored in detail. Influences of pyrolysis temperature (400–800 °C) and biochemical components (carbohydrates, proteins and lipids) of algae on pyrolytic behavior and products characteristics were investigated. EP showed higher char yield, while SP and NS showed high bio-oil yields. At lower temperature (400–500 °C), CO2 was the main gas product, while H2, CH4 and CO evolved out quickly with temperature increasing. EP cracking could release more CO, while SP and NS cracking could release more H2, CH4 and C2. While for bio-oil, it was variant with algae composition and temperature, as EP showed higher furans, SP yielded large amounts of N-containing chemicals, while aliphatics and carboxylic acids were the dominated components for NS. However, aromatics gradually became the major compounds for all bio-oil at 700–800 °C. For char, C-O/C-O-C/C=N, C=O/C-N and COO- groups cracking gradually with temperature increasing and resulted in more aromatic C=C. The optimum operating temperature is 500–600 °C for algae pyrolytic poly-generation to achieve higher value of char, bio-oil and gas products together.

Evaluation of phenotype stability and ecological risk of a genetically engineered alga in open pond production

Genetically engineered (GE) algae offer the promise of producing food, fuel, and other valuable products with reduced requirements for land and fresh water. While the gains in productivity measured in GE terrestrial crops are predicted to be mirrored in GE algae, the stability of phenotypes and ecological risks posed by GE algae in large-scale outdoor cultivation remain unknown. Here, we describe the first US Environmental Protection Agency (EPA)-sanctioned experiment aimed at understanding how GE algae perform in outdoor cultivation. Acutodesmus dimorphus was genetically engineered by the addition of two genes, one for enhanced fatty acid biosynthesis, and one for recombinant green fluorescence protein (GFP) expression; both the genes and their associated phenotypes were maintained during fifty days of outdoor cultivation. We also observed that while the GE algae dispersed from the cultivation ponds, colonization of the trap ponds by the GE strain declined rapidly with increasing distance from the source cultivation ponds. In contrast, many species of indigenous algae were found in every trap pond within a few days of starting the experiment. When inoculated in water from five local lakes, the GE algae's effect on biodiversity, species composition, and biomass of native algae was indiscernible from those of the wild-type (wt) progenitor algae, and neither the GE nor wt algae were able to outcompete native strains. We conclude that GE algae can be successfully cultivated outdoors while maintaining GE traits, and that for the specific GE algal strain tested here they did not outcompete or adversely impact native algae populations when grown in water taken from local lakes. This study provides an initial evaluation of GE algae in outdoor cultivation and a framework to evaluate GE algae risks associated with outdoor GE algae production.

Polysaccharides of algae 69. Monosaccharide composition of polysaccharides of several Pacific red algae studied by reductive hydrolysis of biomass

Polysaccharide composition of 23 species of red algae collected from the coastal waters of Kamchatka and Commander Islands has been determined. Total acid hydrolysis of biomass was carried out in the presence of borane-4-methylmorpholine complex under the conditions where 3,6-anhydrogalactose liberating from sulfated galactans was protected from the acid degradation due to reduction into 3,6-anhydrogalactitol. Partial hydrolysis of biomass in the presence of the same reducing agent gave rise to diastereomeric agarobiitol or carrabiitol (3,6-anhydro-4-O-β-d-galactopyranosyl-l-or -d-galactitol, respectively). Identification of these fragments made it possible to attribute the algal galactans to agars or carrageenans. The data obtained was used to confirm the correlations between the taxonomic status and polysac-charide composition of the red algae.

Erratum to: Changes in ecosystem engineers: the effects of kelp forest type on currents and benthic assemblages in Kachemak Bay, Alaska

In many temperate, rocky-reef coastal ecosystems, kelp forests modify alongshore currents, impact invertebrate settlement, and regulate understory algal abundances. Along the southern coasts of Alaska, in particular, two species of canopy-forming kelps with dissimilar morphologies, Nereocystis luetkeana and Eualaria fistulosa, co-occur but vary in their distributions and patterns of abundance, with one species often replacing the other at given sites in subsequent years. As a result, their differences in morphology may affect patterns of current flow through the forests, which could have strong impacts on invertebrate settlement and benthic diversity, particularly in Kachemak Bay, Alaska (59° 36′33ʺN, 151° 20′51ʺW), which experiences large tidal fluctuations resulting in strong alongshore currents. In this study, significant differences in current reductions were observed between the two kelp forest types within Kachemak Bay, but these reductions were small compared to the natural spatiotemporal variability of currents within the bay, and they were primarily limited to the upper few meters of the water column where the two species exhibit their greatest differences in morphology. Consequently, invertebrate settlement and abundance differed between the two kelp forest types as well as among study sites within the bay. In addition, there were differences observed in the composition and abundance of understory algae between the two forest types, which were presumably due to differences in shading abilities of the dominant kelps. Together, our results suggest that future changes in the distribution and abundances of these two kelp forest types may result in corresponding changes in hydrodynamic conditions within the forests, and thereby impact invertebrate and benthic algal assemblages.

Sustainable approaches for algae utilisation in bioenergy production

Rapidly increasing global energy consumption has caused depletion of fossil fuels, leading to the search of alternative energy resources. One of the potential solutions is utilizing algae biomass as the source of bioenergy. To fulfil the high biomass demands for biofuel production, it is of pivotal importance to develop feasible technologies to enable economic, efficient and high density cultivation of algae. Algae can be cultivated in either open or closed systems in the presence of nutrients and light intensity. The maximum yield, growth rate and composition of algae can be optimized according to cultivation conditions, such as temperature, pH, light intensity and nutrient concentration. The potential types of algae in contributing carbohydrate and lipids to produce biofuel such as biodiesel, bioethanol and bio-gas are reviewed. Economic feasibilities of algae based fuel production are discussed based on Life Cycle Analysis. Current challenges and future prospective are also presented to realize the use of algae as a feedstock for commercial and cost effective fuel production.

Comparative DNA sequence analyses of Pyramimonas parkeae (Prasinophyceae) chloroplast genomes.

Prasinophytes form a paraphyletic assemblage of early diverging green algae, which have the potential to reveal the traits of the last common ancestor of the main two green lineages: (i) chlorophyte algae and (ii) streptophyte algae. Understanding the genetic composition of prasinophyte algae is fundamental to understanding the diversification and evolutionary processes that may have occurred in both green lineages. In this study, we sequenced the chloroplast genome of Pyramimonas parkeae NIES254 and compared it with that of P.parkeae CCMP726, the only other fully sequenced P.parkeae chloroplast genome. The results revealed that P.parkeae chloroplast genomes are surprisingly variable. The chloroplast genome of NIES254 was larger than that of CCMP726 by 3,204bp, the NIES254 large single copy was 288bp longer, the small single copy was 5,088bp longer, and the IR was 1,086bp shorter than that of CCMP726. Similarity values of the two strains were almost zero in four large hot spot regions. Finally, the strains differed in copy number for three protein-coding genes: ycf20, psaC, and ndhE. Phylogenetic analyses using 16S and 18S rDNA and rbcL sequences resolved a clade consisting of these two P.parkeae strains and a clade consisting of these plus other Pyramimonas isolates. These results are consistent with past studies indicating that prasinophyte chloroplast genomes display a higher level of variation than is commonly found among land plants. Consequently, prasinophyte chloroplast genomes may be less useful for inferring the early history of Viridiplantae than has been the case for land plant diversification.

Seasonality of chrysophyte cyst and diatom assemblages in varved Lake Nautajärvi – implications for palaeolimnological studies

Phytoplankton species composition is strongly affected by seasons, which should be taken into account in palaeolimnological studies. Although chrysophyte cysts and diatoms are widely used as palaeobioindicators in palaeolimnological studies, only recently have attempts been made to use their modern deposition from sediment trap data to provide more detailed, seasonal-based environmental reconstructions. In this study sediment traps were used to record seasonality of chrysophyte cysts and diatoms during two climatically different years 2009 and 2010 in an annually laminated Lake Nautajärvi, Finland, and this seasonal data was then compared with the fossil record derived from the surface sediment of the lake. The overall changes in cyst and diatom assemblages between years and seasons are subtle. For both groups, no clear connection to any particular season could be detected in the sediment surface. Despite the climatological differences between the study years, the inter-annual accumulation rates of both algal groups were surprisingly similar, whereas the intra-annual accumulation rates differed substantially. This and the high amount of taxa occurring during all seasons in the trap samples implies that primary producers are more dependent on prevailing seasonal limnological conditions than on rapid, shortly lived episodes. Redundancy analysis (RDA) revealed that chrysophyte cyst assemblages from the spring sediment trap are mainly controlled by the spring discharge intensity, a surrogate variable of spring weather conditions, whereas precipitation and air temperature have the strongest impact on the summer assemblages. However, only discharge explains statistically significantly the variance in the cyst data. Precipitation and air temperature have the strongest impact on the diatom summer samples, whereas the spring sediment trap sample of the snowy and harsh winter of 2010 was strongly correlated with the spring discharge. However, none of the measured environmental variables explains the variance in the diatom data statistically significantly. The similarity between the algae found in the sediment traps and surface sediment sample suggests that within small and shallow lakes without any extreme environmental settings the surface sediment sample represents well the lake´s overall algal composition and can thus be used in palaeolimnological studies.

Stable isotope mass balances versus concentration differences of dissolved inorganic carbon – implications for tracing carbon turnover in reservoirs

ABSTRACTThe aim of this study was to identify sources of carbon turnover using stable isotope mass balances. For this purpose, two pre-reservoirs in the Harz Mountains (Germany) were investigated for their dissolved and particulate carbon contents (dissolved inorganic carbon (DIC), dissolved organic carbon, particulate organic carbon) together with their stable carbon isotope ratios. DIC concentration depth profiles from March 2012 had an average of 0.33 mmol L–1. Increases in DIC concentrations later on in the year often corresponded with decreases in its carbon isotope composition (δ13CDIC) with the most negative value of –18.4 ‰ in September. This led to a carbon isotope mass balance with carbon isotope inputs of −28.5 ‰ from DOC and −23.4, −31.8 and −30.7 ‰ from algae, terrestrial and sedimentary matter, respectively. Best matches between calculated and measured DIC gains were achieved when using the isotope composition of algae. This shows that this type of organic material is most likely responsible for carbon additions to the DIC pool when its concentrations and δ13CDIC values correlate negatively. The presented isotope mass balance is transferable to other surface water and groundwater systems for quantification of organic matter turnover.

Interactive effects of elevated summer temperature, nutrient availability, and irradiance on growth and chemical compositions of juvenile kelp, Eisenia bicyclis

SUMMARYPrevious experiments with a factorial design have revealed the effects of several environmental factors on species performance and their interactions, which indicate synergistic or antagonistic effects. Temperature, nutrient availability, and irradiance are well‐known environmental factors that affect the growth and chemical composition of brown algae. However, relatively few studies have tested their combined effect on brown algal growth and chemical composition using a three‐way factorial design. We conducted a culture experiment to test the combined effects of elevated summer temperatures (23 and 26°C), irradiance (180 and 30 μmol photon m−2 s−1), and nutrient availability (enriched and non‐enriched seawater) on four relative growth rates (RGRs; based on wet weight, blade width, length, and area) and three chemical compositions (including carbon, nitrogen, and phlorotannin content) in juvenile sporophytes of the kelp Eisenia bicyclis. RGR based on blade width was the most sensitive to abiotic factors among all RGRs. A significant interaction between temperature and nutrient availability on this RGR suggested that the negative effect of elevated temperature was antagonized by a reduction in nutrient availability. Similarly, the positive effect of elevated irradiance on carbon content was synergized by reduced nutrient availability. Moreover, the negative effect of increased irradiance on nitrogen content was antagonized by elevated temperature in nutrient‐enriched treatments, but not in non‐enriched treatments. The content of carbon‐based phlorotannins increased with reduced nutrient availability but not with elevated irradiance. These results suggest that these abiotic factors have complex interactions on the growth and chemical composition of this species.