Phytoplankton pigment pattern in the subsurface chlorophyll maximum in the South Java coastal upwelling system, Indonesia

Upwelling occurs on the coast of Java between June and October, forced by local alongshore winds associated with the southeasterly monsoon. This causes variations in phytoplankton community composition in the upwelling zone compared with the surrounding offshore area. Based on pigments analysis with subsequent calculations of group contributions to total chlorophyll a(Chl a) using CHEMTAX, we studied the distribution and composition of phytoplankton assemblages in the subsurface chlorophyll maximum along the south coast of Java and the influence of upwelling. Nineteen phytoplankton pigments were identified using high-performance liquid chromatography, and CHEMTAX analysis associated these to ten major phytoplankton groups. The phytoplankton community in the coastal area influenced by upwelling was characterized by high Chl a and fucoxanthin concentrations, indicating the dominance of diatoms. In contrast, in the offshore area, the Chl a and fucoxanthin concentrations declined to very low levels and the community was dominated by haptophytes represented by 19′-Hexanoyloxyfucoxanthin. Accordingly, microphytoplankton was found to be the major size class in the coastal area influenced by upwelling, while nanophytoplankton was most abundant in the offshore area. Low concentrations of other accessory pigments indicated less contribution from dinoflagellates,prasinophytes, chlorophytes and cryptophytes. Photo-pigment indices revealed that photosynthetic carotenoids(PSCs) were the largest component of the pigment pool, exceeding the proportion of Chl a, with the average PSCTP up to 0.62. These distribution trends can mainly be explained by phytoplankton adaption strategies to upwelling and subsurface conditions by changing species composition and adjusting the pigment pool.

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）×l03 and （1.1±1.4）×l03 cells mL-1,respectively.Prochlorococcus spp.（Pro） was only found in the high-salinity brackish water with the concentration of 3.0× 10^3 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.

Determination of the spatial and temporal variability of phytoplankton community structure in Daya Bay via HPLC-CHEMTAX pigment analysis

The spatial and temporal variability of the phytoplankton community structure in Daya Bay, South China Sea, were identified by using HPLC-CHEMTAX analytical techniques. The highest chlorophyll a(Chl a) concentrations were observed during summer(with an average value of 0.84 μg/L) and lowest ones during winter(with an average value of 0.33 μg/L). CHEMTAX processing revealed the seasonal succession of phytoplankton species in Daya Bay. During winter, diatoms were the dominant phytoplankton species and contributed 41.5% to total Chl a. Based on Chl a concentration, the average ratio of dinofl agellates to total phytoplankton biomass substantially increased with increasing temperature and nitrogen to phosphorus(N/P) ratio, reaching 52.2% in spring. Nutrient limitation shifted from phosphorus to nitrogen during summer. Moreover, this period was associated with the predominance of diatoms, which accounted for 71.1% of Chl a. Prasinophytes and cryptophytes were the other two dominant groups and particularly dominated during winter. Cyanobacteria became an important group during summer and autumn. Canonical correspondence analysis suggested that chrysophytes, dinofl agellates, and cryptophytes were strongly associated with high nitrate concentration, ammonium, dissolved inorganic nitrogen(DIN), and N/P ratio, and were negatively associated with temperature and phosphate. Diatoms and cyanobacteria were strongly associated with temperature, phosphate, and salinity, and are negatively influenced by nitrate, ammonium, DIN, and N/P ratio. Microscopic observations and pigment HPLC information were in good agreement for diatoms and dinofl agellates in the bay. This study demonstrated the usefulness of pigment analysis in investigating the distribution of phytoplankton groups in a complex physical environment, such as Daya Bay.

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.

The separation and identification of phytoplankton pigments from the adjacent waters of Great Wall Station，Antarctica

This paper presents separation and identification of the pigments of the phytoplankton samples collected from the adjacent waters (62°12. 5'S, 58°53' W～62°14. 5' S, 58°57' W) of Great Wall Station, Antarctica during March 1988～February 1989 by using thin-layer chromatographic techniques. Of the 15 kinds of phytoplankton pigments separated, 13 were identified according to the R. values of the various marine algal pigments. The features of seasonal variations of phytoplankton pigments in the studied area are also discussed.

Selective feeding of bay scallop Argopecten irradians on phytoplankton community revealed by HPLC analysis of phytopigments in Bohai Sea, China

Understanding the feeding selectivity on phytoplankton by shellfi sh is currently a big challenge. In order to investigate the feeding behavior of bay scallop ( Argopecten irradians ) on phytoplankton, we compared its compositions of phytopigments in digestive glands with those in the surrounding seawater, and conducted fi ve consecutive investigations between July and November 2016 in a bay scallop culture area along coast of Qinghuangdao City, northwest of the Bohai Sea, China. Phytopigments in four-size fractionated phytoplankton of seawater (micro-(20-200 μm);nano(L)-[10-20 μm];nano(S)-[2.7-10 μm], and pico-[<2.7 μm]) and digestive glands of A . irradians were examined to investigate the selective feeding of A . irradians . Results show that fucoxanthin and peridinin constituted the major part of taxonomically diagnostic carotenoids (TDCs) in the micro- and nano(L)-phytoplankton in seawater. Compared with total phytoplankton biomass of seawater (TPB, sum of the four sizes), a substantial decrease of fucoxanthin proportion to total DCs in digestive glands was observed while that of peridinin, 19′-butanoyloxyfucoxanthin, alloxanthin and 19′-hexanoyloxy-fucoxanthin showed an obvious increase when those pigments were mainly confi ned to micro-sized phytoplankton (20-200 μm). However, zeaxanthin and prasinoxanthin were mainly confi ned to nano(s)- and pico-phytoplankton, of which the proportions in digestive glands were usually lower in TPB. The contribution of lutein to total DCs in digestive glands (with an average of 7.23%) increased compared with TPB of seawater (with an average of 0.63%) during all fi ve sampling times.

Spatial variability of summer and autumn phytoplankton community structure in Xiamen Western Bay based on pigment analysis

The spatial variations of phytoplankton community structure in the Xiamen Western Bay during the summer and autumn cruises in 2001 were investigated based on HPLC analysis of photosynthetic pigments in algal cells and CHEMTAX processing of pigment data. The Chl a concentration reached 18.9 μg/L in the summer and declined to 0.28–2.17 in the autumn, respectively, consistent with the observation of diatom blooms in June. Among the accessory pigments, fucoxanthin was consistently the most abundant, ranging from 0.172 to 8.46 μg/L, with the maximum concentrations in June. 19’- hexfucoxanthin and alloxanthin were the other two abundant pigments in the summer and autumn. In addition, 19’-butanoyloxyfucoxanthin or peridinin was also important in late autumn. Generally the biomass of all the phytoplankton or each group was higher in the inner part than the mouth of this bay, represented by Chl a. CHEMTAX processing revealed the dominance of diatoms with their contribution of 14.6%–52.5% to the total Chl a, but its importance decreased in the autumn. Cryptophytes and Haptophytes, with an average contribution of 16.9%–31.4% and 12.1%–26.3%, were the other two important groups, especially in the autumn. On the contrary, Dinoflagellates and Chlorophytes were the minor groups, but the former became important sporadically in the autumn. It was suggested that there was distinctive variation in both the phytoplankton community structure and biomass between summer and autumn in the Xiamen Western Bay and the latter was coupled to the changes in temperature and dissolved oxygen. However, the spatial variation of the phytoplankton community structure was not as clear as the trend in the biomass of phytoplankton among all the sites in this bay.

Variability of phytoplankton absorption in the northern South China Sea:influence of the size structure and pigment composition of algal populations

Data from three cruises conducted in the Zhujiang River （ZR）, coastal waters of Guangdong （CWGD） and the northern South China Sea （NSCS） during 2003 and 2004 were examined for assessing the relative importance of pigment composition and packaging effect in modifying the specific absorption coefficients of phytoplankton. The three survey regions differ widely in their phytoplankton community with large cells dominating the ZR and CWGD waters and small cells dominating the NSCS region. Variations in the size structure and the accessory pigments have much effect on the chlorophyll a-specific absorption coefficient of phytoplankton. The size index accounted for about 42% and 33% of the variation of the specific absorption coefficient at 440 and 675 nm, respectively. Using the multiple regression analysis approach, pigment concentrations for each sample were calculated. The accessory pigments other than chlorophyll a contribute to absorption mainly in the blue - to - green region of the spectrum and their absorptions account for about 44%, 43% and 53% on the average of the total phytoplankton absorption at 440 nm for the ZR, CWGD and NSCS regions. Among the accessory pigments, the photosynthetic carotenoids （noted PSC） play a dominant role in the ZR and CWGD waters, while in the NSCS the nonphotosynthetic carotenoids （noted PPG） as well as PSC have important contributions. Because the variations of both the size structure and accessory pigments in algal populations contributed to the variability of the specific absorption coefficient in the study regions, these factors may be considered explicitly in future bio - optical algorithms to derive chlorophyll a concentration more accurately.

Phytoplankton composition and its ecological effect in subsurface cold pool of the northern Bering Sea in summer as revealed by HPLC derived pigment signatures

CHEMTAX analysis of high-performance liquid chromatography （HPLC） pigment was conducted to study phytoplankton community structure in the northern Bering Sea shelf, where a seasonal subsurface cold pool emerges. The results showed that fucoxanthin （Fuco） and chlorophyll a （Chl a） were the most abundant diagnostic pigments, with the integrated water column values ranging from 141 to 2160 μg/m2 and 477 to 5 535 μg/m2, respectively. Moreover, a diatom bloom was identified at Sta. BB06 with the standing stock of Fuco up to 9214 μg/m3. The results of CHEMTAX suggested that the phytoplankton community in the northern Bering Sea shelf was dominated by diatoms and chrysophytes with an average relative contribu- tion to Chl a of 80% and 12%, respectively, followed by chlorophytes, dinoflagellates, and cryptophytes. Dia- toms were the absolutely dominant algae in the subsurface cold pool with a relative contribution exceeding 90%, while the contribution of chrysophytes was generally higher in oligotrophic upper water. Additionally, the presence of a cold pool would tend to favor accumulation of diatom biomass and a bloom that occurred beneath the halocline would be beneficial to organic matter sinks, which suggests that a large part of the phytoplankton biomass would settle to the seabed and support a rich benthic biomass.

Gaussian decomposition and component pigment spectral analysis of phytoplankton absorption spectra

The absorption spectrum of phytoplankton is an important bio-optical parameter for ocean color hyperspectral remote sensing;its magnitude and shape can be aff ected considerably by pigment composition and concentration. We conducted Gaussian decomposition to the absorption spectra of phytoplankton pigment and studied the spectral components of the phytoplankton, in which the package effect was investigated using pigment concentration data and phytoplankton absorption spectra. The decomposition results were compared with the corresponding concentrations of the five main pigment groups (chlorophylls a , b , and c , photo-synthetic carotenoids (PSC), and photo-protective carotenoids (PPC)). The results indicate that the majority of residual errors in the Gaussian decomposition are <0.001 m^-1 , and R 2 of the power regression between characteristic bands and HPLC pigment concentrations (except for chlorophyll b) was 0.65 or greater for surface water samples at autumn cruise. In addition, we determined a strong predictive capability for chlorophylls a , c , PPC, and PSC. We also tested the estimation of pigment concentrations from the empirical specific absorption coeffi cient of pigment composition. The empirical decomposition showed that the Ficek model was the closest to the original spectra with the smallest residual errors.The pigment decomposition results and HPLC measurements of pigment concentration are in a high consistency as the scatter plots are distributed largely near the 1:1 line in spite of prominent seasonal variations. The Wozniak model showed a better fit than the Ficek model for Ch1 a , and the median relative error was small. The pigment component information estimated from the phytoplankton absorption spectra can help better remote sensing of hyperspectral ocean color that related to the changes in phytoplankton communities and varieties.

Response of phytoplankton community to different water types in the western Arctic Ocean surface water based on pigment analysis in summer 2008

Nutrients and photosynthesis pigments were investigated in the western Arctic Ocean during the 3rd Chinese Arctic Research Expedition Cruise in summer 2008. The study area was divided into five provinces using the K- means clustering method based on the physical and chemical characteristics of the sea water, and to discuss the distribution of the phytoplankton community structure in these provinces. CHEMTAX software was performed using HPLC pigments to estimate the contributions of eight algal classes to the total chlorophyll a （TChl a）. The results showed that on the Chukchi Shelf, the Pacific Ocean inflow mainly controlled the Chl a biomass and phytoplankton communities by nutrient concentrations. The high nutrient Anadyr Water and Bering Shelf Water （AnW and BSW） controlled region have high Chl a levels and the diatom dominated community structure. In contrast, in the region occupied by low-nutrient like Alaska Coastal Water （ACW）, the Chl a biomass was low, with pico- and nano-phytoplankton as dominated species, such as prasinophytes, chrysophytes and cryptophytes. However, over the off-shelf, the ice cover condition which would affect the physical and nutrient concentrations of the water masses, in consequence had a greater impact on the phytoplankton community structure. Diatom dominated in ice cover region and its contribution to Chl a biomass was up to 75%. In the region dose to the Mendeleev Abyssal Plain （MAP）, controlled by sea-ice melt water with relatively high salinity （MW-HS）, higher nutrient and Chl a concentrations were found and the phytoplankton was dominated by pico- and nano-algae, while the diatom abundance reduced to 33%. In the southern Canada Basin, an ice-free basin （IfB） with the lowest nutrient concentrations and most freshened surface water, low Chl a biomass was a consequence of low nutrients. The ice retreating and a prolonged period of open ocean may not be beneficial to the carbon export efficiency due to reducing the Chl a biomass or intriguing smaller size algae growth.

Comparison of photosynthetic pigments and phytoplankton assemblages in two types of coastal regions in Southeast Asia-Indonesian Throughflow and river estuary

Water samples were collected in order to study the spatial variation of photosynthetic pigments and phytoplankton community composition in the Lembeh Strait(Indonesia) and the Kelantan River Estuary(Malaysia)during July and August 2016, respectively. Phytoplankton photosynthetic pigments were detected using high performance liquid chromatography combining with the CHEMTAX software to confirm the Chl a biomass and community composition. The Chl a concentration was low at surface in the Lembeh Strait, which it was 0.580–0.682 μg/L, with the average(0.620±0.039) μg/L. Nevertheless, the Chl a concentration fluctuated violently at surface in the Kelantan River Estuary, in which the biomass was 0.299–3.988 μg/L, with the average(0.922±0.992) μg/L. The biomass at bottom water was higher than at surface in the Kelantan River Estuary, in which the Chl a concentration was 0.704–2.352 μg/L, with the average(1.493±0.571) μg/L. Chl b, zeaxanthin and fucoxanthin were three most abundant pigments in the Lembeh Strait. As a consequence, phytoplankton community composition was different in the two study areas. In the Lembeh Strait, prasinophytes(26.48%±0.83%) and Synechococcus(25.73%±4.13%) occupied ～50% of the Chl a biomass, followed by diatoms(20.49%±2.34%) and haptophytes T8(15.13%±2.42%). At surface water in the Kelantan River Estuary, diatoms(58.53%±18.44%)dominated more than half of the phytoplankton biomass, followed by Synechococcus(27.27%±14.84%) and prasinophytes(7.00%±4.39%). It showed the similar status at the bottom water in the Kelantan River Estuary,where diatoms, Synechococcus and prasinophytes contributed 64.89%±15.29%, 16.23%±9.98% and 8.91%±2.62%,respectively. The different phytoplankton community composition between the two regions implied that the bottom up control affected the phytoplankton biomass in the Lembeh Strait where the oligotrophic water derived from the West Pacific Ocean. The terrigenous nutrients supplied the diatoms growing, and pico-phytoplankton was grazed through top down control in the Kelantan River Estuary.

Assessing the uncertainties of phytoplankton absorption-based model estimates of marine net primary productivity

Satellite-derived phytoplankton pigment absorption （aph） has been used as a key predictor of phytoplankton photosynthetic efficiency to estimate global ocean net primary production （NPP）. In this study, an aph-based NPP model （AbPM） with four input parameters including the photosynthetically available radiation （PAR）, diffuse attenuation at 490 nm （Ka（490））, euphotic zone depth （Zeu） and the phytoplankton pigment absorption coefficient （aph） is compared with the chlorophyll-based model and carbon-based model. It is found that the AbPM has significant advantages on the ocean NPP estimation compared with the chlorophyll-based model and carbon- based model. For example, AbPM greatly outperformed the other two models at most monitoring sites and had the best accuracy, including the smallest values of RMSD and bias for the NPP estimate, and the best correlation between the observations and the modeled NPPs. In order to ensure the robustness of the model, the uncertainty in NPP estimates of the AbPM was assessed using a Monte Carlo simulation. At first, the frequency histograms of simple difference （fi）, and logarithmic difference （~LOG） between model estimates and in situ data confirm that the two input parameters （Zeu and PAR） approximate the Normal Distribution, and another two input parameters （aph and Ka（490）） approximate the logarithmic Normal Distribution. Second, the uncertainty in NPP estimates in the AbPM was assessed by using the Monte Carlo simulation. Here both the PB （percentage bias）, defined as the ratio of ANPP to the retrieved NPP, and the CV （coefficient of variation）, defined as the ratio of the standard deviation to the mean are used to indicate the uncertainty in the NPP brought by input parameter to AbPM model. The uncertainty related to magnitude is denoted by PB and the uncertainty related to scatter range is denoted by CV. Our investigations demonstrate that PB of NPP uncertainty brought by all parameters with an annual mean of 5.5% covered a range of -5%-15% for the global ocean. The PB uncertainty of AbPM model was mainly caused by aph; the PB of NPP uncertainty brought by aph had an annual mean of 4.1% for the global ocean. The CV brought by all the parameters with an annual mean of 105% covered a range of 98%-134% for global ocean. For the coastal zone of Antarctica with higher productivity, the PB and CV of NPP uncertainty brought by all parameters had annual means of 7.1% and 121%, respectively, which are significantly larger than those obtained in the global ocean. This study suggests that the NPPs estimated by AbPM model are more accurate than others, but the magnitude and scatter range of NPP errors brought by input parameter to AbPM model could not be neglected, especially in the coastal area with high productivity. So the improving accuracy of satellite retrieval of input parameters should be necessary. The investigation also confirmed that the SST related correction is effective for improving the model accuracy in low temperature condition.

Phytoplankton community dynamics during Alexandrium blooms in 2019 off the Qinhuangdao coast,Bohai Sea,China

Alexandrium blooms in the northwest area of the Bohai Sea(Qinhuangdao coastal area),China,produce large amounts of toxins that could be enriched in shellfish and consequently harm human bodies.To understand the succession of the phytoplankton community structure during Alexandrium bloom events in the northwest area of the Bohai Sea off Qinhuangdao from April 2 to May 7,2019,microscopy observations and high-performance chromatography(HPLC)-pigment analysis were performed.Sixty species of phytoplankton were identified,mainly diatoms and dinofl agellates.The abundance of Alexandrium reached the maximum on April 16(3.3×10^(3) cells/L).HPLC-pigment CHEMTAX analysis showed that the phytoplankton community was composed mainly of diatoms,dinofl agellates,prasinophytes,and cryptophytes.Diatoms were the main contributor to the total Chl-a pool.There was a downward trend for the proportion of diatom biomass to the total Chl-a pool,followed by an upward trend.The proportion of dinoflagellate biomass showed the opposite trend,whereas that of the prasinophyte biomass presented an obvious increasing trend.Temperature,nutrients,and nutrient structures were the main factors on the distribution of different phytoplankton groups in the study area as shown in the redundancy analysis.This work illustrates the succession of phytoplankton community structures during Alexandrium blooms and provided a theoretical basis for studies on the mechanism underlying the outbreak of harmful algal blooms in sea areas.

Relationship between bacteria and phytoplankton during the giant jellyfish Nemopilema nomurai bloom in an oligotrophic temperate marine ecosystem

Bacterial abundance, phytoplankton community structure and environmental parameters were investigated to study the relationships between bacteria and phytoplankton during giant jellyfish Nemopilema nomurai blooms in the central Yellow Sea during 2013. N. nomurai appeared in June, increased in August, reached a peak and began to degrade in September 2013. Results showed that phosphate was possible a key nutrient for both phytoplankton and bacteria in June, but it changed to nitrate in August and September. Phytoplankton composition significantly changed that pico-phytoplankton relative biomass significantly increased, whereas other size phytoplankton significantly decreased during jellyfish bloom. In June, a significantly positive correlation was observed between chlorophyll a concentration and bacterial abundance（r=0.67, P0.001, n=34）.During jellyfish outbreak in August, there was no significant correlation between phytoplankton and bacteria（r=0.11, P0.05, n=25）, but the relationship（r=0.71, P0.001, n=31） was rebuilt with jellyfish degradation in September. In August, small size phytoplankton occupied the mixed layer in offshore stations, while bacteria almost distributed evenly in vertical. Chlorophyll a concentration significantly increased from（0.42±0.056） μg/L in June to（0.74±0.174） μg/L in August, while bacterial abundance just slightly increased. Additionally, the negative net community production indicated that community respiration was not entirely determined by the local primary productivity in August. These results indicated that jellyfish blooms potentially affect coupling of phytoplankton and bacteria in marine ecosystems.

Composition of algal pigments in surface freshen layer after ice melt in the central Arctic

Seasonal meltwater input creates a thin freshen layer in surface seawater under ice, which largely shifts the algae assemblages. Our recent observation of photosynthetic pigments in the high Arctic showed that ice bottom and 5 m of seawater under ice contained relatively high concentration of fucoxanthin, while chlorophyll b and lutein were the major diagnostic pigments in ice-water interface and 0 m of seawater under ice. Additionally, a notable change of dominant phytoplankton occurred in the top 5 m of seawater under ice, from chlorophytes-dominated at surface to diatoms-dominated at 5 m depth, which might attribute to the sharp salinity gradient （salinity from 12.5 to 28.1） in the surface seawater under ice. Our results imply that phytoplankton community in surface layer under ice would become more chlorophytes in the future warming Arctic Ocean.

Effect of Freshwater Influx on Phytoplankton in the Mandovi Estuary (Goa, India) during Monsoon Season: Chemotaxonomy

The Mandovi estuary is a prominent water body that runs along the west coast ofIndia. It forms an estuarine network with the adjacent Zuari estuary, connected via the Cumbharjua canal. The physico-chemical conditions seen in the Mandovi estuary are influenced by two factors: the fresh water runoff during the monsoon season (June-September) and the tidal influx of coastal seawater during the summer (October to May) season. However, the effects of monsoon related changes on the phytoplankton of the Mandovi estuary are not yet fully understood. An attempt to understand the same has been made here by applying the process of daily sampling at a fixed station throughout the monsoon season. It was noticed that the onset of the monsoon is responsible for an increase in nitrate levels upto 26 μM from a (chl a) as high as 14 μg·L-1 during the same period. The phytoplankton population was observed through both chemotaxonomy and microscopy and was found to be composed mainly of diatoms. CHEMTAX analysis further uncovers the presence of several other groups of phytoplankton, the presence of which is yet to be reported in many other tropical estuaries. It includes chrysophytes, cyanobacteria, prasinophytes, prymnesiophytes and chlorophytes. The appearance of phytoplankton groups at various stages of the monsoon was recorded, and this data is discussed in relation to environmental changes in the Mandovi estuary during the monsoon season.

Comparison of Phytoplankton Communities Between Melt Ponds and Open Water in the Central Arctic Ocean

Climate warming has a significant impact on the sea ice and ecosystem of the Arctic Ocean.Under the increasing numbers of melt ponds in Arctic sea ice,the phytoplankton communities associated with the ice system are changing.During the 7th Chinese National Arctic Research Expedition cruise in summer 2016,photosynthesis pigments and nutrients were analyzed,revealing differences in phytoplankton communities between melt ponds and open water in the central Arctic.Photosynthetic pigment analysis suggested that Fuco(5-91μg m^-3)and Diadino(4-21μg m^-3)were the main pigments in the open water.However,the melt ponds had high concentrations of Viola(7-30μg m^-3),Lut(4-59μg m^-3)and Chl b(11-38μg m^-3),suggesting that green algae dominated phytoplankton communities in the melt ponds.The significant differences in phytoplankton communities between melt ponds and open water might be due to the salinity difference.Moreover,green algae may play a more important role in Arctic sea ice ecosystems with the expected growing number of melt ponds in the central Arctic Ocean.

海洋浮游藻类的化学分类法

综述了以色素分析为基础的海洋浮游藻类化学分类法的发展过程,发现基础性数据缺乏和应用范围不够广阔是阻碍此项研究发展的主要问题。本文详细讨论了高效液相色谱(HPLC)藻类色素分析数据之数学解析技术的进展,对最近出现的分析软件(CHEMTAX)进行了重点介绍。最后,对海洋浮游藻化学分类法的发展趋势进行了分析预测。

夏季新安江水库(千岛湖)颗粒物吸收光谱特征分析

通过对2013年夏季新安江水库（千岛湖）53个站点悬浮颗粒物的吸收光谱进行研究,系统分析了总颗粒物吸收系数ap（λ）、非藻类颗粒物吸收系数ad（λ）和浮游藻类光谱吸收系数aph（λ）的变化规律以及影响因素.结果表明：总颗粒物吸收除西北河流区上游段外,其他各站点均呈现出明显的浮游藻类吸收特性,反映新安江水库总颗粒物中浮游藻类贡献较高.全库ap（440）在0.068 ～0.629 m-1之间变化,西北河流区总颗粒物吸收系数显著大于其他水域,而湖泊区与西南河流区则显著小于其他水域.非藻类颗粒物吸收光谱随着波长增加大致呈现出指数函数衰减的规律,其光谱斜率Sd均值为8.52±1.62μm-1,存在显著的空间差异,但整体偏低,与新安江水库无机颗粒物含量低有关.ad （440）与浮游藻类色素浓度存在显著的线性相关,表明夏季新安江水库非藻类颗粒物可能主要来源于浮游藻类降解.浮游藻类的光谱吸收在440和675 nm附近有明显的吸收峰.aph（440）和aph（675）存在显著的空间差异,其与浮游藻类色素浓度存在极显著的正线性关系,而与总悬浮颗粒物浓度相关性较弱.