Marker Pigments Research Articles

Drivers of phytoplankton diversity in Lake Tanganyika

In keeping with the theme of this volume, the present article commemorates the 50 years of Hutchinson’s (Am Nat 93:145–159, 1959) famous publication on the ‘very general question of animal diversity’, which obviously leads to the more important question regarding the driving forces of biodiversity and their limitation in various habitats. The study of phytoplankton in large lakes is a challenging task which requires the use of a wide variety of techniques to capture the range of spatial and temporal variations. The analysis of marker pigments may provide an adequate tool for phytoplankton surveys in large water bodies, thanks to automated analysis for processing numerous individual samples, and by achieving sufficient taxonomic resolution for ecological studies. Chlorophylls and carotenoids were analysed by HPLC in water column samples of Lake Tanganyika from 2002 through 2006, at two study sites, off Kigoma (north basin) and off Mpulungu (south basin). Using the CHEMTAX software for calculating contributions of the main algal groups to chlorophyll a, variations of phytoplankton composition and biomass were determined. We also investigated selected samples according to standard taxonomic techniques for elucidating the dominant species composition. Most of the phytoplankton biomass was located in the 0–40 m layer, with maxima at 0 or 20 m, and more rarely at 40 m. Deep chlorophyll maxima (DCM) and surface ‘blooms’ were occasionally observed. The phytoplankton assemblage was essentially dominated by chlorophytes and cyanobacteria, with diatoms developing mainly in the dry season. The dominant cyanobacteria were very small unicells (mostly Synechococcus), which were much more abundant in the southern basin, whereas green algae dominated on average at the northern site. A canonical correspondence analysis (CCA) including the main limnological variables, dissolved nutrients and zooplankton abundance was run to explore environment–phytoplankton relations. The CCA points to physical factors, site and season as key determinants of the phytoplankton assemblage, but also indicates a significant role, depending on the studied site, of calanoid copepods and of nauplii stages. Our data suggest that the factors allowing coexistence of several phytoplankton taxa in the pelagic zone of Lake Tanganyika are likely differential vertical distribution in the water column, which allows spatial partitioning of light and nutrients, and temporal variability (occurring at time scales preventing long-term dominance by a single taxon), along with effects of predation by grazers.

Light acclimation states of phytoplankton in the Southern Ocean, determined using photosynthetic pigment distribution

In high-latitude waters such as the Southern Ocean, the primary production of phytoplankton supports the ecosystem. To understand the photo-acclimation strategy of such phytoplankton within cold environments, the vertical distribution profile of photosynthetic pigments was analyzed in the Southern Ocean. Samples were taken along 110°E during the austral summer, and along 150°E and around the edge of the seasonal sea ice of the Antarctic Continent during the austral autumn. Pigment extraction methods were optimized for these samples. The standing crop of chlorophyll a was larger in the region along the edge of the seasonal sea ice than at sampling stations in open ocean areas. Chlorophyll concentration seemed to be dependent on the formation of thermo- and haloclines along the edge of the seasonal sea ice, but not in the open ocean where such clines are less pronounced. The marker pigments fucoxanthin and/or 19′-hexanoyloxyfucoxanthin were dominant at most sampling stations throughout the water column, while other marker pigments such as alloxanthin were quite low. This indicated that diatoms and/or haptophytes were the major phytoplankton in this area. Comparison of the relative ratio of fucoxanthin with that of 19′-hexanoyloxyfucoxanthin allowed some stations to be characterized as either diatom-dominant or haptophyte-dominant. The relative ratio of xanthophyll-cycle pigments (diadinoxanthin plus diatoxanthin) to chlorophyll a was high in surface waters and decreased gradually with depth. This suggests that near the ice edge during summer in the Southern Ocean, both diatoms and haptophytes acclimate to their light environments to protect their photosystems under high-light conditions.

Differences in microphytobenthos and macrofaunal abundances associated with groundwater discharge in the intertidal zone

We investigated the impact of intertidal groundwater seepage on benthic microalgae and macrofauna in 4 study sites located in 2 large tidal flat ecosystems along the western coast of Korea by comparing the chemical, physical, and biological characteristics of 'glossy' seepage sites with those of nearby areas without visually distinct groundwater discharge (dry sediment surface). At 3 of the 4 sites, sediment properties as well as pore water chemistry were similar in groundwater seepage and dry areas. At the 4th study site, the groundwater seepage areas were more coarse- grained compared to the dry areas. Here, the groundwater seepage also had lower salinity and higher nutrient concentrations than the pore water of the dry area and the seawater in a nearby tide pool. Although diatoms were the dominant algal class in seepage and dry areas alike, the seepage areas in 3 of the sites had elevated contributions of other marker pigments such as chlorophyll (chl) b compared to the dry areas. Chl a concentrations were higher in all seepage areas compared to dry areas, and all dry areas had high pheophytin a:chla ratios, indicating a substantial amount of degraded algal material. In the seepage areas of 3 of the sites, we found large numbers of the snail Batillaria cumingi, while crab burrows of Scopimera sp. were only present in the neighboring dry areas. Correlations of sediment chl a concentrations with physicochemical properties of the ambient pore water indicated that microphytobenthos responded specifically to groundwater seepage, which may provide shelter from desiccation and salt stress during emersion of the tidal flat. Our results sug- gest that globally common groundwater seepage significantly impacts the ecosystem structures and microphytobenthos production of the tidal flats.

Stress and toxicity of biologically important transition metals (Co, Ni, Cu and Zn) on phytoplankton in a tropical freshwater system: An investigation with pigment analysis by HPLC

Stress and toxicity of four biologically important transition metals (Co, Ni, Cu and Zn) on phytoplankton in Godavari River (a tropical freshwater system) were studied to understand the fate of phytoplankton of freshwater if it receives metal contaminated water imposed by these four metals. Shift in community structure of phytoplankton and their different tolerance levels for different metals were also investigated. It was found that the variation of metal concentrations at lower level (1 × 10 −9 to 1 × 10 −8 M) did not show a dramatic change in the total biomass or concentrations of the pigment markers. At concentration of 1 × 10 −7 M of metal, Cu acted as a nutrient and helped to increase the biomass followed by Co, Ni and Zn. The variation in biomass in the freshwater system under exposure to different metals at high concentration of 1 × 10 −6 M indicates that Cu had strongest interactions with biotic ligand and was taken up by phytoplankton and acted as the most toxic metal followed by Zn, Co and Ni. Phytoplankton communities in Godavari River have different tolerance levels for different metals. Cu and Zn were found to be lethal at high concentration for both green algae and cyanobacteria. Cyanobacteria were found to be very sensitive to slight variation in Ni concentration and Co was found to be less toxic than Cu and Zn even at high exposed concentration.

Short-term variability in halocarbons in relation to phytoplankton pigments in coastal waters of the central eastern Arabian Sea

Halocarbons released from oceans are known to be important in the atmospheric processes. Their abundance in seawater is influenced by water column conditions and phytoplankton community. In the present study halocarbon abundances together with pigment composition were monitored in the coastal waters of the central eastern Arabian Sea. Short-term variability for the period December 2005–March 2007 was studied for chlorinated hydrocarbons (CHCl 3, CCl 4) and bromocarbons (CH 2Br 2 and CHBr 3) for the first time in the Arabian Sea. Variability in pigments was used to understand the influence of phytoplankton community composition on halocarbon concentrations in this region. Halocarbons and phytoplankton pigments showed strong short-term variability, with maximal values generally associated with southwest (summer) monsoon high productivity. Decreased chlorocarbon abundances in sub-surface layers indicate their possible consumption under oxygen deficient conditions, particularly during the summer monsoon and Fall-Intermonsoon periods. Halocarbon abundances were in the order: CHCl 3, CH 2Br 2, CHBr 3 and CCl 4. The CHCl 3 showed significant positive relationship with fucoxanthin ( r = 0.93, p = 0.001, n = 155) suggesting the importance of diatoms and prymnesiophytes in the Arabian Sea. Among the phytoplankton pigments chlorophyll- a showed a positive relationship with marker pigment fucoxanthin. Of the four phytoplankton groups studied, the percent dominance was in the order: diatoms > nanoflagellates > cyanobacteria > dinoflagellates. Our study shows that the utilization of halocarbons during microbial oxidation of organic matter could be a significant sink of these compounds although they might be produced in significant quantities by biochemical processes during high productivity periods, as can be seen from our observations in summer monsoon in the Arabian Sea.

The influence of biotic factors on phytoplankton pigment composition and resources in Baltic ecosystems: new analytical results

Mathematical expressions were derived describing the distribution and concentration of individual phytoplankton pigments with respect to biotic factors in the southern Baltic. Relationships were established between the chlorophyll a concentration and the total phytoplankton biomass (represented by the organic carbon content), as well as between the concentration of marker pigments and the biomasses of the corresponding phytoplankton classes. Knowledge of chlorophyll a concentrations allows the phytoplankton biomass to be estimated with a precision characterised by relative statistical errors according to logarithmic statistics of σ − = ca 56%. The best approximation was obtained for the dependence of the Bacillariophyceae biomass on the fucoxanthin concentration (σ − = 60%), Chlorophyceae on the lutein concentration (σ − = 48%), and the total biomass of Dinophyceae, Bacillariophyceae and Euglenophyceae on the concentration of * This work was carried out within the framework of IO PAS’s statutory research and also as part of projects MNiSW: 2 P04F 052 26, N306 1391 33 and N306 2838 33 funded by the Polish Ministry of Science and Higher Education. The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 102 J. Ston-Egiert, M. Łotocka, M. Ostrowska, A. Kosakowska diadinoxanthin, the main carotenoid pigment present in cells of species from these classes (σ − = 60%).

Effects of seasonality and resource limitation on organic matter turnover by Chironomidae (Diptera) in southern Appalachian headwater streams

Despite their high abundance, secondary production, and known reliance on detrital material, the role of chironomids (Diptera) in fine particulate organic matter (FPOM) dynamics has not been well quantified. We conducted field trials using fluorescent pigment markers to estimate seasonal rates of consumption, annual secondary production, assimilation efficiency (AE), and FPOM turnover for non‐Tanypodinae chironomids in two similar, southern Appalachian, headwater streams. An ecosystem‐level experimental manipulation of detrital inputs in one study stream allowed for a unique assessment of turnover in reference, resource‐limited, and resource‐recovery systems. Seasonality had a significant effect on larval gut‐passage time (GPT), with faster GPT at higher temperatures. Mean GPT ranged from 39 min (summer) to 67 min (winter). Mean annual FPOM turnover was reduced in the resource‐limited stream (5.5 kg ash‐free dry weight per year; 12% of mean annual FPOM export) compared to the reference stream (46 kg yr−1; 74% of mean export). Following 4 yr of resource recovery, FPOM turnover increased to 24 kg ash‐free dry wt yr−1 (16% of export) but remained lower than levels measured in the reference stream (53 kg ash‐free dry wt yr−1; 20% of export). Chironomid contribution to FPOM turnover was much higher in low vs. high discharge conditions (74% in low discharge vs. 20% in high discharge). Assimilation efficiency was estimated to be low in all systems (1.7–2.5%). Chironomids turned over a large portion of FPOM available to them, suggesting that turnover by the entire collector community in forested headwater systems may be much higher than expected.

Spectral fluorometric characterization of phytoplankton community composition using the Algae Online Analyser ®

The utility of a multiple-fixed-wavelength spectral fluorometer, the Algae Online Analyser (AOA), as a means of quantifying phytoplankton biomass and community composition was tested using natural communities from two southeastern United States estuaries, North Inlet, South Carolina, and the Neuse River Estuary, North Carolina. Estimates of biomass (as chlorophyll a) were correlated with HPLC values and variations (usually over-estimates) were consistent with effects of light intensity and nutrient availability on fluorescence quenching. AOA estimates of taxonomic structure were consistent with those from HPLC-derived marker pigments by ChemTax, with both methods indicating domination by chromophytes and green algae in North Inlet and chromophytes and cyanobacteria in the Neuse. We recommend frequent calibration by discrete sample collection, and calibration with species representative of the region of interest. Overall, the AOA appears to be a useful tool for monitoring of phytoplankton community composition, especially as an early warning system for the detection of harmful algal blooms.

Carbon fluxes through major phytoplankton groups during the spring bloom and post-bloom in the Northwestern Mediterranean Sea

The carbon flux through major phytoplankton groups, defined by their pigment markers, was estimated in two contrasting conditions of the Northwestern Mediterranean open ocean ecosystem: the spring bloom and post-bloom situations (hereafter Bloom and Post-bloom, respectively). During Bloom, surface chlorophyll a (Chl a) concentration was higher and dominated by diatoms (53% of Chl a), while during Post-bloom Synechococcus (42%) and Prymnesiophyceae (29%) became dominant. The seawater dilution technique, coupled to high pressure liquid chromatography (HPLC) analysis of pigments and flow cytometry (FCM), was used to estimate growth and grazing rates of major phytoplankton groups in surface waters. Estimated growth rates were corrected for photoacclimation based on FCM-detected changes in red fluorescence per cell. Given the 30% average decrease in the pigment content per cell between the beginning and the end of the incubations, overlooking photoacclimation would have resulted in a 0.40 d −1 underestimation of phytoplankton growth rates. Corrected average growth rates ( μ o) were 0.90±0.20 (SD) and 0.40±0.14 d −1 for Bloom and Post-bloom phytoplankton, respectively. Diatoms, Cryptophyceae and Synechococcus were identified as fast-growing groups and Prymnesiophyceae and Prasinophyceae as slow-growing groups across Bloom and Post-bloom conditions. The higher growth rate during Bloom was due to dominance of phytoplankton groups with higher growth rates than those dominating in Post-bloom. Average grazing rates ( m) were 0.58±0.20 d −1 (SD) and 0.31±0.07 d −1. The proportion of phytoplankton growth consumed by microzooplankton grazing ( m/ μ o) tended to be lower in Bloom (0.69±0.34) than in Post-bloom (0.80±0.08). The intensity of nutrient limitation experienced by phytoplankton indicated by μ o/ μ n (where μ n is the nutrient-amended growth rate), was similar during Bloom (0.78) and Post-bloom (0.73). Primary production from surface water (PP) was estimated with 14C incubations. A combination of PP and Chl a synthesis rate yielded C/Chl a ratios of 34±21 and 168±75 (g:g) for Bloom and Post-bloom, respectively. Transformation of group-specific Chl a fluxes into carbon equivalents confirmed the dominant role of diatoms during Bloom and Synechococcus and Prymnesiophyceae during Post-bloom.

伝導パスモデルに基づくトナー帯電メカニズム

A charge control mechanism of charge control agents （CCAs） has been proposed in the present investigation that assumes an appreciable temperature increase at the "toner/carrier" interface due to triboelectrification. A further assumption is that the CCA is present on the surface of both toner and carrier. Because of local heating, the electrical conductivity of CCAs is increased remarkably to give a conductive channel, through which the carrier flow occurs effectively to charge the toner. These two assumptions have experimentally been verified. Especially, local heating of up to 100℃ has been confirmed by using a pigment marker that changes its color from black to red. Around this temperature, the electrical conductivity of CCAs is also found to increase significantly by one to three orders of magnitude as compared with that at room temperature.

Sedimentary pigments in 308 alpine lakes and their relation to environmental gradients

We undertook a comprehensive comparison between the pigment composition of surface sediment samples and contemporary catchment and limnological data deriving from 308 mountain lakes in 11 mountain regions (Lake Districts) covering a wide latitudinal and longitudinal gradient across Europe. This paper examines whether photosynthetic algal and bacterial pigments stored in the lake sediment can be used to identify different lake typologies and population dynamics of primary producers. We focus on a multivariate numerical analysis relating the relative abundance of marker pigments of algae, cyanobacteria and phototrophic sulphur bacteria to a set of physical and chemical factors (both natural and anthropogenic) determining the environmental conditions in mountain lakes. Redundancy Analysis (RDA), including partial RDA, of carotenoid assemblages constrained by environmental variables suggests that the main differences between lake districts are caused by geographic position (e.g. longitude), catchment characteristics (e.g. % carbonate rocks) and chemical variables (e.g. Mg, NO3). Other variables such as temperature and phosphorus play a minor role, probably be cau se of the short length of the gradient covered by these cold and mostly oligotrophic lakes. Pigment composition varies primarily in response to catchment geology and pollution (i.e. acidification from long range transport) gradients. Purple sulphur photosynthetic bacteria (okenone) and cyanobacteria (echinenone, canthaxanthin, scytonemin) are replaced by siliceous algae (fucoxanthin and diatoxanthin), cryptophytes (alloxanthin) and dinoflagellates (diadinoxanthin). With respect to site classification, the pigment ordination shows a clear distinction between the more pristine lakes (in the Pyrenees) and the more polluted sites (in the Tatra Mountains and Central Southern Alps) or those with water higher in solute content (the Julian Alps and Greenland).

Primary production in Lake La Cruz (Spain) over the last four centuries: reconstruction based on sedimentary signal of photosynthetic pigments

We analysed photosynthetic pigments in annually laminated sediment of meromictic Lake La Cruz, Spain, to cope with the timing and characterisation of primary productivity changes over the last four centuries. The photosynthetic pigments identified included chlorophyll a and b (and its derivatives) and specific carotenoids of different algal groups, such as zeaxanthin, lutein, alloxanthin, diadinoxanthin and diatoxanthin among others. Marker pigments of phototrophic sulfur bacteria were also observed, including bacteriochlorophyll a derivatives, homologue series of bacteriophaeophytins d and bacterial carotenoids okenone and chlorobactene. We investigated the diagenetic processes of pigment alteration in anoxic sediments and the possible implications for paleoproductivity reconstruction and interpretation. The lack of systematic down-core changes in diagenetic indicators suggests that variability of sedimentary pigment concentrations is the result of changes in lake productivity. The lower concentration of algal photosynthetic pigments in the bottom of sediment sequence corresponds to the onset of meromictic conditions. Before that, sediment was not continuously anoxic and the preservation of pigments was reduced. Regarding photosynthetic bacteria, green sulfur bacteria derivatives indicate that population growth was limited until the settled organic matter was sufficient to provide enough sulphide. Moreover, the presence of bacterioviridine, an oxidised derivative of bacteriochlorophyll a, suggest the competitive relation among photosynthetic bacteria. The high relative abundance of zeaxanthin indicates the dominance of picocyanobacteria in the primary productivity over the last centuries. Fluctuations of the pigment signal observed in the sediment sequence during the meromictic period were well correlated with fluctuations of solar activity.

Variability of phytoplankton pigment ratios across aquatic environments

The majority of phytoplankton pigment studies are from marine, estuarine and oceanic waters, and commonly use estimates of the ratio between marker pigments and chlorophyll a (chl a) for calculating the contribution of phytoplankton groups to total chl a. In this study, we examined pigment ratios obtained with CHEMTAX processing of field data from a range of tropical and temperate freshwater bodies with contrasting water transparency, depth of the mixed layer, and trophic state. The pigment ratios obtained from processing data from fresh waters corresponded quite well with existing values from pure cultures, and were compared with the marine marker pigment:chl a ratio calculated with CHEMTAX using identical procedures. In deep, stratifying lakes a large variation of some pigment ratios with depth was observed, as well as seasonal variation relating to changes in water column structure. There was considerable variation of average phytoplankton pigment ratios among the freshwater bodies studied. Pigment ratios were significantly correlated to indicators of nutrient availability, to depth of the euphotic zone, or to a proxy of light availability. The substantial variation in marker pigment:chl a ratio confirms that algorithms which account for natural variation of pigments in phytoplankton groups are required for accurate assessment of phytoplankton groups based on marker pigment concentration alone.

Characteristics of phytoplankton community structure during and after a bloom of the dinoflagellate Scrippsiella trochoidea by HPLC pigment analysis

A bloom of the dinoflagellate Scrippsiella trochoidea was detected for the first time in inner Tolo Harbor, Hong Kong in 2 000. Water samples were collected at eight stations along a transect passing through a red tide patch for microscopic analysis of phytoplankton composition and high-performance liquid chromatography (HPLC) analysis of phytoplankton pigments. During the bloom, the density of dinoflagellates was 1.1×106 cells L−1 within the patch and 8.6×105 cells L−1 outside the patch where the phytoplankton community was dominated by diatoms. After the bloom the S. trochoidea began to decrease in density and was replaced by diatoms as the dominating bloom-causing organisms at all stations, and the density of dinoflagellates at most stations was less than 1.0 × 106 cells L−1. The status of S. trochoidea as the causative species of the bloom was indicated by the presence of peridinin, the marker pigment for dinoflagellates. The shift from dinoflagellates to diatoms was marked by the decline of peridinin and the prevalence of fucoxanthin. Phytoplankton pigment markers also revealed the presence of other minor phytoplankton assemblages such as cryptomonads and blue-green algal.

Testing of the CHEMTAX program in contrasting Neotropical lakes, lagoons, and swamps

The problem using the CHEMTAX program in freshwater environments is that the few matrices of pigment ratios available have not been tested in a wide range of environments. Sixteen Amazonian, Andean, and Caribbean lakes, lagoons, and swamps were sampled over a year. The aim was to determine if it was possible to obtain a reliable matrix of input pigment ratios that may be used in freshwater habitats with different environmental conditions. There were no clear differences among regions for most of the ratios of marker pigments to Chlorophyll a (Chl a) in most of the phytoplankton groups. Only the zeaxanthin/Chl a ratio showed clear variations among areas. The estimates for the mean relative contribution of each phytoplankton group calculated for the pigment ratios obtained in each separate habitat and season were very similar to the estimates calculated using the average pigment ratio obtained for all habitats and seasons. Our study suggests that the matrix of the average pigment ratio obtained in this study can be used to estimate phytoplankton class abundances with the CHEMTAX program in freshwater habitats with different limnological conditions.

DrosophilaABC transporter mutantswhite,brownandscarlethave altered contents and distribution of biogenic amines in the brain

Monoamines such as dopamine, histamine and serotonin (5-HT) are widely distributed throughout the brain of the fruit fly Drosophila melanogaster, where many of their actions have been investigated. For example, histamine is released from photoreceptor synapses in the lamina neuropile of the visual system. Mutations of the genes white, an important eye pigmentation marker in fly genetics that encodes an ABC transporter, and its binding partner brown, cause neural phenotypes not readily reconciled solely with actions in eye pigmentation. We find that flies mutant for these genes, and another binding partner, scarlet, have about half the wild-type amount of histamine in the head, as well as reduced 5-HT and dopamine. These differences parallel reductions in immunoreactivity to the corresponding biogenic amines. They also correlate with the amine content of fractions after differential centrifugation of head homogenates. Thus, most of the amine is found in the vesicle-rich fraction of wild-type head homogenates, whereas it is found in the supernatant fractions from white, brown and scarlet flies. White co-expresses in lamina epithelial glia with Ebony, which conjugates histamine to beta-alanine. Histamine is then released when the conjugate is hydrolyzed in photoreceptors, by Tan. Mutant white ameliorates the effects of tan on head histamine whereas it exacerbates the effects of ebony. Our results are consistent with the proposal that histamine uptake by the epithelial glia may be white dependent. Behavioral abnormalities in white, brown and scarlet mutants could arise because aminergic neurons in the Drosophila brain have reduced amine for release.

Percutaneous Collagen Induction: Minimally Invasive Skin Rejuvenation without Risk of Hyperpigmentation—Fact or Fiction?

Photoaging is generally treated by ablative procedures that injure the epidermis and basal membrane and lead to fibrosis of the papillary dermis. Damaging the epidermis significantly can cause potential adverse effects such as dyspigmentation. It was recently shown in clinical trials that percutaneous collagen induction therapy is an alternative for safely treating wrinkles and scars and for smoothening the skin without the risk of dyspigmentation. The purpose of this study was to increase current knowledge regarding whether percutaneous collagen induction therapy presents an effective means for skin rejuvenation without risk of dyspigmentation, as the authors' clinical data suggested. Fifty-six rats were assigned to three groups: group A (n = 24), percutaneous collagen induction therapy plus skin care; group B (n = 24), skin care; and group C (n = 8) controls. The authors evaluated the effect of percutaneous collagen induction therapy on the epidermis, melanocytes, and the pigmentation markers interleukin-10 and melanocyte-stimulating hormone. Percutaneous collagen induction therapy left the epidermis intact without any damage to the stratum corneum, any other layers of the epidermis, or the basal membrane. No signs of dermabrasive reduction of epidermal thickness were evident 24 hours after the procedure. The number of melanocytes neither increased nor decreased in any of the groups. DNA microarray experiments demonstrated that interleukin-10 was increased in percutaneous collagen induction therapy-treated skin after 2 weeks. Concerning the MC1R (melanocyte-stimulating hormone) gene, gene expression microarray analysis indicated a faint down-regulation both 24 hours and 2 weeks after percutaneous collagen induction therapy. Percutaneous collagen induction therapy offers a modality with which to rejuvenate and improve skin appearance and quality without risk of dyspigmentation.

Sedimentary pigments in the western Barents Sea: A reflection of pelagic–benthic coupling?

Abstract Local pelagic and sympagic primary production are usually the base of the Arctic food webs, and can be the main inputs of organic matter to the benthos. In order to characterize the major sources of production and understand the fate of organic matter to the benthos, water-column, ice, and sedimentary pigments of the Barents Sea were studied by HPLC analysis at 12 stations during the summer 2003, summer 2004, and spring 2005, in the framework of the CABANERA project. Chlorophyll a (chl a) concentration in surface sediments correlated significantly with total chl a integrated throughout the water-column as well as the chl a fluxes measured at 1 and 90 m water depth. This suggests that local water-column and ice-associated algae production are the main sources of fresh organic matter to the benthos. In the sediment, water-column, and ice, the major accessory pigment found was fucoxanthin, the marker pigment of diatoms, particularly dominant in spring. In summer, chlorophyll b, a marker of green algae, was found in stations influenced by Arctic waters, while 19′-hex-fucoxanthin, a marker of prymnesiophytes, was found in stations influenced by Atlantic water. The source of organic matter inputs to the benthos is thus highly dependent of the water masses influences in the summer. The ratio of sedimentary chl a to total phaeopigments (chl a/phaeo) was higher in the spring, and the total of phaeopigments in the sediment was correlated with water-column phaeopigments and with sedimentary phaeophorbide a, a pigment typical of grazing by zooplankton. This suggests that in the summer, organic matter reaching the sediment already has been degraded through grazing, while in spring, more fresh material reaches the sediment. The chl a/phaeo ratio was correlated with benthic oxygen demand measured by other researcher in this project, suggesting the importance of the quality of the organic matter reaching the sediment for benthos activities. Our results confirm a close pelagic–benthic coupling in both spring and summer over the entire study area.

History of anthropogenically mediated eutrophication of Lake Peipsi as revealed by the stratigraphy of fossil pigments and molecular size fractions of pore-water dissolved organic matter

We investigated stratigraphic changes in fossil pigments and the molecular structure of the UV-absorbing fraction of pore-water dissolved organic matter in a sedimentary record from Lake Peipsi (Estonia/Russia) temporally covering the 20th century. The aims of the study were to define the onset of eutrophication in the lake and to track its course. An attempt was also made to reconstruct lake conditions before the intensive nutrient loading began. Fossil pigment analysis indicated that the eutrophication of the lake started in the 1960s and accelerated in the 1970s. Sedimentary pigments also indicate a continuing tendency of the lake ecosystem towards eutrophy in the 1980s and 1990s. However, changes in the molecular size structure of pore-water dissolved organic matter indicated that the contribution of autochthonous matter to the organic pool of the lake ecosystem had already started to increase around the end of the 1930s. We conclude that this rise was generated by a coincidence of several anthropogenic and natural factors. The pore-water data also show that a slight relative reduction in the autochthonous organic matter took place in the 1990s. A discordance in the paleodata obtained for the beginning of the 20th century complicates clear conclusions about earlier conditions in the lake. On the one hand, the qualitative characteristics of pore-water dissolved organic matter and the low concentration of chlorophyll a indicate that the phytoplankton biomass was low in Lake Peipsi during that period. On the other hand, the concentrations of marker pigments of specific phytoplankton groups are high, comparable with the values in the recent sediments. Possible reasons for the high levels of these pigments in the early 1900s sediments, such as a shift in the preservation conditions of organic substances and their transport from the lake’s catchment, are discussed.

Use of marker pigments and functional groups for assessing the status of phytoplankton assemblages in lakes

Phytoplankton is a key biological quality element for the establishment of the Water Framework Directive (WFD) ecological status in reservoirs and lakes. In freshwaters, inverted microscope examination is the traditional standard method for estimating phytoplankton and assessing taxonomic composition. Based on the enumeration of algal units and measurements for biovolume calculation, this technique is cumbersome and time-consuming. In large monitoring programmes, such as the application of the WFD in lakes and reservoirs, chemotaxonomy (HPLC pigment analysis and CHEMTAX treatment) is ideally suited as an alternative method because it allows the rapid processing of large numbers of samples from numerous locations and depths, thereby providing ideal temporal and spatial resolution. The low taxonomical detail obtained by HPLC and CHEMTAX (phytoplankton classes or phyla) can easily be overcome by a rapid inverted microscope screening with identification of the dominant species. Combining HPLC and microscopy provides a useful method for monitoring phytoplankton assemblages, which can be used to implement the WFD with respect to phytoplankton. Here, we present the application of a method combining marker pigments and microscopy to phytoplankton samples from 12 Belgian reservoirs. This method substantially reduced the workload and enabled us to assess the status of the phytoplankton assemblage in these lakes. The method complies with the WFD, as it takes into account taxonomic composition, assesses abundance and biomass of the phytoplankton taxa, and easily detects blooms. Additionally, a set of templates of probability of occurrence of phytoplankton functional groups at the maximal ecological potential for reservoirs from the Central/Baltic region is presented, based on reference conditions defined for natural lakes from other regions.