Distribution Of Phytoplankton Pigments Research Articles

Spatial phytoplankton community structure revealed by photosynthetic pigments in the tropical estuarine-coastal zone (Bangladesh)

To explore the variation of phytoplankton community along the Bakkhali river estuary and its adjacent coastal water in the north of the Bay of Bengal, total Chl-a (TChl-a) concentrations and group-specific photosynthetic pigments were investigated during April 2017. Distinct spatial distribution was observed in temperature, turbidity and nutrient concentrations as well as in TChl-a concentrations, showing a seaward decreasing pattern. The different distribution of phytoplankton pigments and functional groups along the gradients was also observed. Chlorophyll-b and zeaxanthin showed their highest abundance in the turbid riverine water, while alloxanthin and prasinoxanthin dominated in the coastal water. High concentrations of fucoxanthin, peridinin and hex-fucoxanthin were associated with high-light availability and showed a seaward increasing trend. Three phytoplankton groups can be classified: the riverine group (chlorophytes and cyanobacteria), the coastal group (cryptophytes and prasinophytes) and the offshore group (diatoms, dinoflagellate and haptophytes_type 6). The predominance of cryptophytes (avg. 48%) over diatoms (avg. 28%) was basically influenced by the scarcity of nitrogen and silicate relative to phosphate. Not only availability of nutrients, the photosynthetically active radiation also plays a key role in regulating TChl-a, photosynthetic pigments and functional groups in this tropical estuarine-coastal zone.

Northeast monsoon distribution of biogeochemical properties and phytoplankton pigments from Hooghly–Sundarbans estuarine region, India

Phytoplankton marker pigments and their relationships with water column properties were investigated for the first time in the Hooghly–Sundarbans region. The upper estuary (Diamond Harbour) was characterized by low salinity with high silicate and nitrate within the surface waters. This region showed a strong presence of marker pigment fucoxanthin, an indicator of diatom populations. In contrast, marker pigment zeaxanthin and chlorophyll b became equally dominant with the increasing salinity in the lower estuary Silicate and nitrate showed positive relationships with diatom indices suggesting strong dependency. Contrary to that, picoplankton indices increased the high saline oligotrophic waters of the lower estuary (Sundarbans). Divinyl Chlorophyll a and b were not detected in any of the sample sets suggesting the absence of Prochlorococcus populations around the sampling locations. Oxygen distribution was strongly correlated with temperature and salinity, suggesting significant physical control. Further silicate, also showed a positive relationship with turbidity inferring that the river discharge is an important source. Our study suggests 60 % of the chlorophyll a biomass is contributed by microplankton communities with the rest 40 % by picoplankton during the northeast monsoon. As sinking rates and carbon to chlorophyll a ratio varies among different communities, the relative efficiency of primary productivity and carbon sequestration may be re-looked here in light of this new revelation.

Nutrient concentrations and distribution of phytoplankton pigments in recently deposited sediments of a positive tropical estuary

Investigation of nutrients in the water column and phytoplankton pigments in recently formed modern sediments (0–5 cm) was carried out in Cochin estuary. The anthropogenic impacts were assessed using nutrients, nitrate, and phosphate in combination with phytopigments in sediments. The nitrate and phosphate concentration during the study ranged from 0.81 to 42.53 μmol/L and from 0.1 to 5.81 μmol/L, respectively. The mean values of the pigment showed the following order: zeaxanthin (791.53 ng/g) > lutein (347.57 ng/g) > fucoxanthin (335.30 ng/g) > pheophytin (308.84 ng/g) > pheophorbide (172.06 ng/g) > chlorophyll a (161.63 ng/g). The increase in the concentration of zeaxanthin indicated the presence of cyanobacteria, associated with eutrophication. Correlation analysis revealed that water column nutrients have a strong relationship between fucoxanthin and lutein, indicating the coexistence of diatoms and prasinophytes in the sampling sites. The principal component analysis showed positive loading of nutrients concomitant with pigment fucoxanthin and lutein, thus establishing that nutrient input controls the phytoplankton biomass of this estuary.

Inversion of Phytoplankton Pigment Vertical Profiles from Satellite Data Using Machine Learning

Observing the vertical dynamic of phytoplankton in the water column is essential to understand the evolution of the ocean primary productivity under climate change and the efficiency of the CO2 biological pump. This is usually made through in-situ measurements. In this paper, we propose a machine learning methodology to infer the vertical distribution of phytoplankton pigments from surface satellite observations, allowing their global estimation with a high spatial and temporal resolution. After imputing missing values through iterative completion Self-Organizing Maps, smoothing and reducing the vertical distributions through principal component analysis, we used a Self-Organizing Map to cluster the reduced profiles with satellite observations. These referent vector clusters were then used to invert the vertical profiles of phytoplankton pigments. The methodology was trained and validated on the MAREDAT dataset and tested on the Tara Oceans dataset. The different regression coefficients R2 between observed and estimated vertical profiles of pigment concentration are, on average, greater than 0.7. We could expect to monitor the vertical distribution of phytoplankton types in the global ocean.

Coastal Phytoplankton Pigments Composition in Three Tropical Estuaries of Indonesia

In this study, the composition and distribution of phytoplankton pigments and its relation to nutrients and light was investigated, and an elaboration of using it as a proxy for phytoplankton group composition followed, in different nutrient-level tropical bays of Indonesia. Phytoplankton pigment analysis by using High Performance Liquid Chromatographer (HPLC) resulted in a set of pigments of chlorophyll-a (Chl-a), chlorophyll-b (Chl-b), chlorophyll-c (Chl-c), lutein, zeaxanthin, fucoxanthin, peridinin, diadinoxanthin, and ß-carotene. Linear multi regression and multivariate principal component analysis (PCA) showed that algae pigments correlate positively with nutrients and are not significantly correlated with underwater light and water transparency, suggesting important roles of nutrients for phytoplankton development in tropical estuaries. There were differences in total algae pigment concentration between bays (p < 0.005), showing that the eutrophic system of Jakarta Bay was the highest (mean of 10.55 μg L−1), Lampung Bay was the second highest (mean of 3.37 μg L−1), and the lowest were the oligotrophic waters of Semangka Bay (mean of 0.80 μg L−1). At all bays studied, high nutrient sites, which were located in the river mouths and inner part of the bay, were always characterized by high phytoplankton pigment concentration. Pigment composition had a high correlation with phytoplankton composition: diatoms with fucoxanthin, dinoflagellates with peridinin and Chl-c, and Chlorophyceae with Chl-b and lutein. This conformity suggests that algae pigments can be used as a biomarker for phytoplankton group determination along with microscopic species identification.

The spatial distribution of phytoplankton pigments in the surface sediments of the Kongsfjorden and Krossfjorden ecosystem of Svalbard, Arctic

Kongsfjorden–Krossfjorden twin fjord ecosystem in Svalbard (Arctic), is facing enhanced warm Atlantic water intrusion from ocean as well as intensified melting from glaciers. It is an interesting ecosystem to study phytoplankton productivity under the two opposing processes. For phytoplankton productivity, pigments are used as potential photosynthetic biomass indicators and taxonomic biomarkers. However, due to labile nature of pigments, degradation — preservation distribution must be investigated to form essential framework for biomarker studies. With this motivation, we have undertaken the present work to study the spatial distribution of surface sedimentary pigments in the twin-fjord ecosystem. The pigments were analysed using high-performance liquid chromatography coupled with diode array detector. A total of fifteen pigments were identified, which belonged to different classes — chlorophylls, pheopigments and carotenoids. Chlorophyll-a and pheophorbide-a were major pigments with concentration up to 700–800 ng g−1 dry weight of sediment. Among carotenoids, fucoxanthin, diatoxanthin and prasinoxanthin were abundant with maximum concentration recorded up to 400–600 ng g−1 dry weight. The distribution of the pigments varied significantly between the two fjords as well as in different regions of the fjord. Most of the pigments were significantly high in their concentration at Krossfjorden stations. Within Kongsfjorden, outer region showed higher concentration of pigments than inner. However, preservation was lesser for the outer fjord pigments than inner as confirmed by various pigment indices. Further, the overall distribution of phytoplankton communities derived from taxonomic biomarker pigments in Kongsfjorden–Krossfjorden sediments, was coherent with that of water during spring and summer. The distribution was dominated by diatoms, dinoflagellates, prasinophytes and prymnesiophytes. The surface sedimentary pigments were found capable of providing information about phytoplankton biomass and composition under environmental conditions existing in the region.

Phytoplankton pigments and functional community structure in relation to environmental factors in the Pearl River Estuary

Summary Two cruises were undertaken in the Pearl River Estuary in November 2011 and March 2012 to analyze the distribution of phytoplankton pigments and to define the relationships of pigment indices and functional community structure with environmental factors. Among 22 pigments, 17 were detected by high-performance liquid chromatography. Chlorophyll a was found in all samples, with a maximum of 7.712 μg L −1 in spring. Fucoxanthin was the most abundant accessory pigment, with mean concentrations of 2.914 μg L −1 and 0.207 μg L −1 in spring and autumn, respectively. Chlorophyll a , chlorophyll c 2 , fucoxanthin, diadinoxanthin, and diatoxanthin were high in the northern or northwest estuary in spring and in the middle-eastern and northeast estuary in autumn. Chlorophyll b , chlorophyll c 3 , prasinoxanthin, and peridinin were similarly distributed during the two cruises. Chlorophyll a and fucoxanthin positively correlated with nutrients in spring, whereas 19′-hex-fucoxanthin and 19′-but-fucoxanthin negatively correlated. The biomass proportion of microphytoplankton (BP m ) was higher in spring, whereas that of picophytoplankton (BP p ) was higher in autumn. BP m in spring was high in areas with salinity p and the biomass proportion of nanophytoplankton (BP n ) were high in areas with salinity >30. BP m increased but BP n reduced with the increase in nutrient contents. By comparison, BP p reduced with the increase in nutrient contents in spring, but no relationship was found between BP p and nutrient contents in autumn. The ratios of photosynthetic carotenoids to photoprotective carotenoids in the southern estuary approached unity linear relationship in spring and were under the unity line in autumn.

Controls on temporal and spatial variations of phytoplankton pigment distribution in the Northern South China Sea

The seasonal and spatial variations of phytoplankton pigment distribution and their interaction with environmental controlling parameters were investigated in the Northern South China Sea (NSCS) at 37 stations covering the coastal region, the continental shelf, the slope, and the deep-water basin during two summer and two winter cruises from 2010 to 2012. Strong spatial, interseasonal, and intraseasonal variations of pigment distribution were observed in the diverse biogeochemical regions, exhibiting extremely dynamic phytoplankton community structure in the NSCS. In addition to chlorophyll a, the major pigments observed included divinyl chlorophyll a (DV Chl a), total chlorophyll b (Chl b), zeaxanthin (Zea), 19′-hexanoyloxyfucoxanthin (Hex), 19′-but-fucoxanthin (But), fucoxanthin (Fuco), and prasinoxanthin (Pras). Overall, Fuco, Chl b, Zea, Hex, But, and Pras were the dominant pigments in the coastal and shelf region; DV Chl a, Chl b, Hex, But, Zea, and Fuco were the major pigments in the offshore water. After analyzing marker pigment correlations and cellular pigment concentrations, we conclude that Zea, Hex (with But), and Fuco can be used as specific marker pigments for Synechococcus, coccolithophores, and diatoms in the NSCS, respectively. We have also derived that prasinophytes accounted for most of the elevated Chl b observed in the coastal water and appeared to be an important pico-eukaryotic group (Pico) in the coastal region. With varying cellular pigment concentrations observed vertically and seasonally, it is essential to separate sampling stations to different biogeochemical domains to apply pigment to Chl a ratios to estimate phytoplankton community structure in the NSCS. We observed close association between soluble reactive phosphate and Chl a abundance in coastal, shelf, and deep-water regions during summer cruises. Major nutrient supply appears to be the main controlling factor on the temporal and spatial variations of major pigment distribution. The supply is mainly driven by terrestrial input in summer and water mixing strength in winter. During the summer periods, major nutrients are primarily supplied from riverine and groundwater discharge; during winter periods, strong winter monsoon intensifies sub-surface water mixing and results in nutrient and pigment elevation in the euphotic zone. Also driven by the monsoon, the intrusion of the low-temperature coastal current from Taiwan Strait to the coastal region of the NSCS may replace or alter the phytoplankton community in the coastal region in winter. Overall, the temporal and spatial variations of phytoplankton pigment distribution in the NSCS are regulated by the fluctuations of these two major environmental forcings.

Distributions of picophytoplankton and phytoplankton pigments along a salinity gradient in the Changjiang River Estuary, China

We investigated the abundance of different picophytoplankton groups and the phytoplankton pigment ratio in relation to environmental factors such as nutrients and suspended solids along a salinity gradient in the Changjiang River Estuary. The average numbers of Synechococcus spp. (Syn) and picoeukaryotes (Euk) were (2.7 ± 5.1) ×103 and (1.1±1.4) ×103 cells mL−1, respectively. Prochlorococcus spp. (Pro) was only found in the high-salinity brackish water with the concentration of 3.0×103 cells mL−1. Syn and Euk numbers both tended to increase offshore and Syn showed a larger variation in cell abundance than Euk. The contribution of picophytoplankton to total phytoplankton biomass increased with increasing salinity and decreasing nutrient concentrations from the estuary to the open ocean. The response of different picophytoplankton groups to environmental variables was different. Water temperature was more important in its control over Euk than over Syn, while nutrients were more important in their influence over Syn than over Euk. Phytoplankton pigment ratios were different in the three different ecological zones along the salinity gradient (i.e., freshwater zone with 0–5 range, fresh and saline water mixing zone with 5–20 range, and high-salinity brackish water zone with 20–32 range), where three different phytoplankton communities were discovered, suggesting that phytoplankton pigment ratios can be considered as a complementary indicator of phytoplankton community structure in the Changjiang River Estuary.

基于光合色素的钦州湾平水期浮游植物群落结构研究

应用反相高效液相色谱(RP-HPLC)并结合二极管阵列检测器分析技术,分析了2010年平水期钦州湾浮游植物光合色素组成,进而由CHEMTAX 软件估算全粒级浮游植物的群落结构。结果表明:平水期浮游植物特征光合色素含量以岩藻黄素最高,其次为叶绿素b、玉米黄素和青绿素,其它特征光合色素含量较低;水体中色素组成表明浮游植物的优势类群为硅藻,其次为蓝藻和青绿藻,它们分别平均占据了浮游植物生物量的73.9%、11.7%和8.7%,其它藻类所占比例很低。硅藻呈现出从湾顶往外随着盐度增加而增加的趋势,而青绿藻显现出相反的分布趋势。钦州湾浮游植物群落结构形成了茅岭江和钦江河口、湾颈-外湾近岸和外湾靠外海域共3种类型,平水期浮游植物群落结构的组成和分布特征主要是由茅岭江和钦江径流变化以及营养盐等环境所决定。平水期叶绿素b和青绿素在大部分站点存在证实了青绿藻在钦州湾的分布,而且表明青绿藻、绿藻和定鞭金藻等微型藻类在钦州湾占有相当比重,它们的重要性有待进一步研究。;Structural characteristics of phytoplankton community during normal season in 2010 in Qinzhou bay were studied. Phytoplankton samples were analyzed by RP-HPLC combined with DAD (diode array detector) to determine photosynthetic pigments composition in the study bay. Pigments data were converted into phytoplankton composition by software CHEMTAX based on least square method and steepest descent algorithm. Our results showed that salinity in the bay ranged from 14.2 to 31.0, and nitrate as well as phosphate concentrations decreased as salinity increasing from the top of bay to outer bay, which showed typical estuarial characteristics. Chlorophyll-a (Chl-a), fucoxanthin, chlorophyll-b (Chl-b), prasinoxanthin and zeaxanthin were the major pigments in the Qinzhou bay. Chl-a concentration ranged from 2693 μg/m³to 4338 μg/m³ (with a mean of 3529 μg/m³), and the concentration of fucoxanthin ranged from 390 μg/m³to 1081 μg/m³ (with a mean of 629 μg/m³). Mean concentrations of Chl-b, prasinoxanthin and zeaxanthin were 304 μg/m³, 66μg/m³ and 65 μg/m³, respectively. Other pigments generally contributed minor proportion of the total pigments, with average concentrations of less than 50 μg/m³. Diatoms dominated in the phytoplankton community, contributing to 76% (mean value) of the phytoplankton biomass during normal season in the Qinzhou Bay, while the average percentage for prasinophyceae and cyanobacteria was only 12.2% and 5.5%, respectively. The rest of other phytoplankton was rare, which only took < 10% of all phytoplankton biomass. Diatoms biomass ranged from 1.49×10³μg/m³ to 3.98×10³μg/m³ (Chl-a biomass), and the distribution of diatom biomass showed a pattern of low in the inner bay while high in the outer bay. However, the biomass of prasinophyceae showed a pattern of decreasing from the inner bay to the outer bay. Phytoplankton communities in the Qinzhou bay were clustered into three types from the estuary to the outer bay,which were primarily influenced by flood of the Maolingjiang River and Qinjiang River. Diatoms together with cyanobacteria and prasinophyceae were the major groups in the estuary of Maolingjiang River and the Qinjiang River, while diatoms were dominated between the inner bay and the outer bay. Diatoms also dominated in the offshore stations of the outer bay, and the proportion of diatoms increased a little and diatoms became a single dominated group. The distribution of major phytoplankton pigments and community were coupled with the environmental parameters in the Qinzhou Bay. River flow, salinity and nutrients were the major controlling factors accounting for the spatial distribution and composition of phytoplankton in the bay during the normal season.

Remote sensing of phytoplankton community composition along the northeast coast of the United States

Satellite imagery has proven to be a powerful tool for measuring chlorophyll a in surface waters. While this provides an estimate of total phytoplankton biomass, it does not distinguish between phytoplankton groups, many of which have functional differences and therefore affect biogeochemical cycles differently. Phytoplankton pigment analysis has been used to quantify a wide range of photosynthetic and accessory pigments, and chemotaxonomic analysis (e.g. CHEMTAX) has been used to successfully quantify functional taxonomic groups in nature based on pigment distributions. Here, we combine CHEMTAX analysis with satellite-derived distributions of specific phytoplankton pigments to describe the distributions of particular components of the phytoplankton community in the northeast coast of the United States from space. The spatial and seasonal variations in phytoplankton community structure elucidated through satellite remote sensing methods generally agreed with observations of abundance estimates of cell counts. Diatoms were generally the most abundant phytoplankton in this region, especially during Winter–Spring and in the inner shelf, but phytoplankton populations shifted to increasing abundance of other taxa during Summer, especially offshore. While still preliminary, satellite-derived taxa-specific information with proper regional controls holds promise for providing information on phytoplankton abundance to a taxonomic group level which would greatly improve our understanding of the impacts of human activity and climate change on ecosystems.

Primary description of surface water phytoplankton pigment patterns in the Bay of Bengal

Spatial and temporal variations in surface water phytoplankton pigment distribution in the Bay of Bengal were studied during the spring intermonsoon (SpIM, February–April) and the commencement of the summer monsoon (CSM, May–June), using pigment and diagnostic indices. The Prokaryotic pigment index (Prok DP) was dominant at all the oceanic stations whereas the Flagellate pigment index (Flag DP) was dominant at the near coastal stations. However, during the commencement of summer monsoon, an oscillation in the dominance of Prok DP and Flag DP was observed in the central oceanic bay, whereas flagellates and diatoms were dominant at the near coastal stations. This change in pigment pattern is possibly related to the influence of rainfall. Comparison of pigment data with microscopic cell counts indicated a significant relationship between the diatom pigment index (Diat DP) and diatom abundance. However, the relationship between the dinoflagellate pigment index (Dino DP) and dinoflagellate abundance was not significant. Studies coupling pigment composition analysis with microscopic analysis of phytoplankton in natural conditions should thus be a prerequisite in establishing valid biogeochemical and ecosystem models.

Spatial–temporal distribution of phytoplankton pigments in relation to nutrient status in Jiaozhou Bay, China

We conducted studies of phytoplankton and hydrological variables in a semi-enclosed bay in northern China to understand the spatial–temporal variability and relationship between these variables. Samples were collected during seven cruises in Jiaozhou Bay from November 2003 to October 2004, and were analyzed for temperature, nutrients and phytoplankton pigments. Pigments from eight possible phytoplankton classes (Diatoms, Dinoflagellates, Chlorophyceae, Prasinophyceae, Chrysophyceae, Haptophyceae, Cryptophyceae and Caynophyceae) were detected in surface water by high performance liquid chromatography (HPLC). Phytoplankton pigment and nutrient concentrations in Jiaozhou Bay were spatially and temporally variable, and most of them were highest in the northern and eastern parts of the sampling regions in spring (May) and summer (August), close to areas of shellfish culturing, river estuaries, dense population and high industrialization, reflecting human activities. Chlorophyll a was recorded in all samples, with an annual mean concentration of 1.892 μg L −1, and fucoxanthin was the most abundant accessory pigment, with a mean concentration of 0.791 μg L −1. The highest concentrations of chlorophyll a (15.299 μg L −1) and fucoxanthin (9.417 μg L −1) were observed in May 2004 at the station close to the Qingdao Xiaogang Ferry, indicating a spring bloom of Diatoms in this area. Although chlorophyll a and other biomarker pigments showed significant correlations, none of them showed strong correlations with temperature and nutrients, suggesting an apparent de-coupling between the pigments and these hydrological variables. The nutrient composition and phytoplankton community composition of Jiaozhou Bay have changed significantly in the past several decades, reflecting the increasing nutrient concentrations and decline of phytoplankton cell abundance. The unchanged total chlorophyll a levels indicated that smaller species have filled the niche vacated by the larger species in Jiaozhou Bay, as revealed by our biomarker pigment analysis.

Remote sensing of phytoplankton pigment distribution in the United States northeast coast

Phytoplankton pigments constitute many more compounds than chlorophyll a that can be applied to study phytoplankton diversity, populations, and primary production. In this study, field measurements were applied to develop ocean color satellite algorithms of phytoplankton pigments from in-water radiometry measurements. The match-up comparisons showed that the satellite-derived pigments from our algorithms agree reasonably well (e.g. 30–55% of uncertainty for SeaWiFS and 37–50% for MODIS-Aqua) to field data, with better agreement (e.g. 30–38% of uncertainty for SeaWiFS and 39–44% for MODIS-Aqua) for pigments abundant in diatoms. The seasonal and spatial variations of satellite-derived phytoplankton biomarker pigments, such as fucoxanthin, which is abundant in diatoms, peridinin, which is found only in peridinin-containing dinoflagellates, and zeaxanthin, which is primarily from cyanobacteria in coastal waters, revealed that higher densities of diatoms are more likely to occur on the inner shelf and during winter–spring and obscure other abundant phytoplankton groups. However, relatively higher densities of other phytoplankton, such as dinoflagellates and cyanobacteria, are likely to occur on the mid- to outer-continental shelf and during summer. Seasonal variation of riverine discharge may play an important role in stimulating algal blooms, in particular diatoms, while higher abundances of cyanobacteria coincide with warmer water temperatures and lower nutrient concentrations.

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%).

Spatial variability of phytoplankton pigment distributions in the Subtropical South Pacific Ocean: comparison between in situ and predicted data

Abstract. In the frame of the BIOSOPE cruise in 2004, the spatial distribution and structure of phytoplankton pigments was investigated along a transect crossing the ultra-oligotrophic South Pacific Subtropical Gyre (SPSG) between the Marquesas Archipelago (141° W–8° S) and the Chilean upwelling (73° W–34° S). A High Performance Liquid Chromatography (HPLC) method was improved in order to be able to accurately quantify pigments over such a large range of trophic levels, and especially from strongly oligotrophic conditions. Seven diagnostic pigments were associated to three phytoplankton size classes (pico-, nano and microphytoplankton). The total chlorophyll-α concentrations [TChlα] in surface waters were the lowest measured in the centre of the gyre, reaching 0.017 mg m−3. Pigment concentrations at the Deep Chlorophyll Maximum (DCM) were generally 10 fold the surface values. Results were compared to predictions from a global parameterisation based on remotely sensed surface [TChlα]. The agreement between the in situ and predicted data for such contrasting phytoplankton assemblages was generally good: throughout the oligotrophic gyre system, picophytoplankton (prochlorophytes and cyanophytes) and nanophytoplankton were the dominant classes. Relative bacteriochlorophyll-α concentrations varied around 2%. The transition zone between the Marquesas and the SPSG was also well predicted by the model. However, some regional characteristics have been observed where measured and modelled data differ. Amongst these features is the extreme depth of the DCM (180 m) towards the centre of the gyre, the presence of a deep nanoflagellate population beneath the DCM or the presence of a prochlorophyte-enriched population in the formation area of the high salinity South Pacific Tropical Water. A coastal site sampled in the eutrophic upwelling zone, characterised by recently upwelled water, was significantly and unusually enriched in picoeucaryotes, in contrast with an offshore upwelling site where a more typical senescent diatom population prevailed.

Phytoplankton pigment distribution in the northwestern Alboran Sea and meteorological forcing: A remote sensing study

A set of weekly-composite SeaWiFS (Sea-viewing Wide Field of view Sensor) imagery (from 1998 to 2004) has been used to asses the temporal and spatial variability of the surface chlorophyll distribution in the Northwestern Alboran Sea. Empirical Orthogonal Function (EOF) analysis of the images series shows the existence of three different regions in which surface chlorophyll presents a homogeneous temporal behavior in the neighborhood of the Strait of Gibraltar. The temporal patterns of surface chlorophyll concentrations in each region have been characterized by studying the role of several forcing factors, mainly the zonal component of the wind field. The first identified region occupies the coastal area in front of Estepona and Malaga and shows the highest chlorophyll concentration in the entire region of study in absence of easterly winds. A second region is located far offshore, in the zone usually occupied by the Atlantic jet entering the Alboran Sea, showing high concentrations of chlorophyll when the easterlies blow. Finally, a third region has been situated in the normal location of the Western Alboran Gyre (WAG). The zonal wind field arises as a main forcing function in the modulation of the intensity and location of the upwelling processes in the area, while the entrance of the Atlantic jet seems to be the main agent feeding of all these processes.

Spatial and vertical distribution of phytoplankton pigments in the eastern Atlantic sector of the Southern Ocean

Abstract The spatial and vertical distribution of phytoplankton pigments was analysed during the Scandinavian/South African Southern Ocean JGOFS expedition of the S.A. Agulhas from 31 December 1997 to 26 January 1998. In total, seawater from 12 different stations along a transect at 6°E from 60.38 to 49.82°S were sampled at water depths of approximately 2, 10, 20, 30, 50, 75 and 100 m. Pigment concentrations were analysed using high-performance liquid chromatography. The highest chlorophyll a (chl a ) concentrations were found within the Spring Ice Edge (SIE) at water depths of 2–30 m (1.5–2.0 μg l −1 ). The lowest phytoplankton biomass (chl a ) was found within the Winter Ice Edge (WIE) with typical values around 0.3 μg l −1 . While the chl a concentrations decreased with depth within the SIE, no apparent difference between depths was found within WIE. The same trend with similar chl a concentrations (0.8–1.2 μg l −1 ) at all depths was found for the northernmost part of the Antarctic Polar Front (APF) except for samples from 100 m. Principal component analysis (PCA) and the matrix factorisation program, CHEMTAX, were used to interpret the pigment data. The PCA indicated small differences between the samples in WIE and APF, while the SIE samples were separated into three groups. At the southernmost stations a clear separation was found between surface samples and deeper samples; this was not seen at the two northernmost stations within SIE. Along the whole transect, CHEMTAX suggested a dominance of diatoms and haptophytes. In general, the haptophytes contributed more to total chl a further south and the diatom contribution increased from south to north. Within WIE, CHEMTAX indicated that cyanobacteria were contributing approximately 3% to the total autotrophic biomass. In APF, a more diverse phytoplankton community was found compared with WIE and SIE. The pigment patterns interpreted by CHEMTAX showed that different phytoplankton assemblages were associated with distinct water masses along the transect.

The influence of hydrodynamics on the spatial and temporal variation of phytoplankton pigments in a large, sub-tropical coastal lake (Brazil)

This study evaluated the spatial and temporal distribution of phytoplankton pigments in Itapeva Lake and its relationship with hydrodynamic aspects. Regarding spatial distribution, a decreasing N®S gradient was generally observed for the pigments, except in summer. This inversion observed during the summer was influenced by the predominant fetch (N-E). The horizontal heterogeneity was proved (ANOVA) for all seasons of the year, except spring. Spatially in spring, the vertical variance was much more significant (p&lt;0.05) than the horizontal one. The sampling shifts presented a permanent degree of variability among the seasons of the year, showing the existence of a diurnal cycle in the concentration of chlorophyll a. This behavior was related to the fetch, mainly from the NE and SW quadrants, disturbing the system because it is a shallow lake. This confirmed the influence of the Itapeva Lake's hydrodynamic regime on the spatial-temporal distribution of the phytoplankton pigments.

PHYTOPLANKTON PIGMENTS IN COASTAL LAKE MICHIGAN: DISTRIBUTIONS DURING THE SPRING ISOTHERMAL PERIOD AND RELATION WITH EPISODIC SEDIMENT RESUSPENSION1

Phytoplankton pigment distributions during the spring isothermal periods of 1998 and 1999 and their association with episodic sediment resuspension were characterized in coastal waters of southern Lake Michigan. Total and phylogenetic group chl a concentrations (derived using chemical taxonomy matrix factorization of diagnostic carotenoids) corresponded with assemblage and group biovolumes estimated from microscopic enumeration (P≤ 0.001). Diatoms and cryptophytes dominated assemblages and together typically comprised greater than 85% of relative chl a. Total chl a concentrations and both fucoxanthin·chl a−1 and alloxanthin·chl a−1 ratios were similar across depths (P&gt; 0.05), indicating uniform distributions of and photophysiological states for assemblages and diatoms and cryptophytes, respectively, throughout the mixed water column. Total chl a concentrations were not always spatially uniform from near‐shore to offshore waters, with the greatest variability reflecting the influence of tributary inflows upon coastal assemblages. Sediment resuspension strongly influenced water column particle density and light climate; however, total and group chl a concentrations did not correspond with coefficients of Kd and suspended particulate matter concentrations (P&gt; 0.05). The correspondence of both light attenuation and suspended particulate matter concentration with relative diatom chl a (P≤ 0.001) indicated an apparent association between sediment resuspension and diatoms. This, and the negative association (P≤ 0.0001) between relative diatom and cryptophyte chl a, corresponded with the spatial dominance of diatom and cryptophyte chl a in near‐shore and offshore waters, respectively. The presence of viable chl a and fucoxanthin within the surficial sediment layer, established this layer as a potential source of meroplanktonic diatoms for near‐shore assemblages.