Distribution Of Phytoplankton Species Research Articles

Ecological patterns of phytoplankton across lake cross-section: insights into co-evolution of physicochemical conditions in Chashma Lake on Indus River.

Physicochemical properties of water influence planktonic diversity and distribution, which is essential in obtaining basic knowledge of aquatic biodiversity. Thus current study aims to investigate the spatiotemporal diversity, abundance ratio, and distribution of phytoplankton species and their association with water quality parameters of Chashma Lake, Pakistan. During the study period from 2018 to 2019, we measured 13 physicochemical parameters across three selected sampling sites (S1, S2, and S3) in Chashma Lake, revealing both spatial and temporal variability. Dissolved oxygen (DO) was higher in S3, while S1 exhibited higher alkalinity levels, carbon dioxide, phosphorus, and chloride levels. The study identified 77 phytoplankton species grouped into five taxonomic categories, with Cyanobacteria dominating (39.90%), followed by Chlorophyta (33.4%) and Bacillariophyta (24.88%). Euglenozoa and Ochrophyta were less abundant (1.3% and 0.41%, respectively). Spatial variations in phytoplankton distribution were noted, with Chlorophyta being more abundant at S2, Bacillariophyta and Cyanobacteria at S1, and Euglenozoa dominating at S3. Canonical Correspondence Analysis (CCA) revealed the influence of various physicochemical parameters on phytoplankton distribution. This comprehensive study provides valuable insights for the ecological assessment and monitoring of water bodies. It is recommended that continuous monitoring is required to capture long-term trends, further explore the specific environmental drivers impacting phytoplankton dynamics, and consider management strategies for maintaining water quality and biodiversity in Chashma Lake.

Diversity and Distribution of Harmful Algal Bloom Species from Seamount to Coastal Waters in the South China Sea.

Mount Xianbei is one of the largest shallow seamounts located in the middle of the South China Sea (SCS), which might play a role in shaping the biodiversity of surrounding continental coastal waters, particularly the diversity of phytoplankton species causing frequent harmful algal blooms (HABs) in northern SCS. However, the diversity, composition, and distribution of phytoplankton species in the seamount regions of Xianbei remain largely unexplored. In this study, samples around and outside the seamount regions were collected during a late summer cruise of 2021 to test whether seamounts play a role in HAB species propagation. In total, we identified 19 HAB species across all samples using the ASV-based DNA metabarcoding approach, 6 of which had not been reported previously in the SCS, suggesting a diverse HAB species in the SCS. Specifically, 16 HAB species were found in the seamount region of Xianbei, and 5 of them were also found in the coastal waters, indicating a close connection between seamount and coastal waters. This study was the first attempt to explore HAB species' spatial diversity and vertical distribution in the seamount region of Xianbei at single-nucleotide resolution, which provides a novel explanation for the coastal HAB occurrence in the northern SCS. IMPORTANCE There are a number of seamounts under the water of the South China Sea (SCS). The seamounts might play a role in shaping the biodiversity of surrounding continental coastal waters. However, there is no direct evidence revealing the relationship of the biodiversity of phytoplankton between seamounts and coastal waters in the SCS, especially those species having the potential to form harmful algal blooms (HABs). Some HAB species might proliferate in certain geographic locations, while others may be broadly distributed across oceanic provinces. In this study, we provided a detailed analysis of phytoplankton composition and molecular detection of HAB species from seamount to coastal waters in the SCS, which suggested a strong interaction in the HAB species between the two areas. This finding provides new insights into the diversity and distribution of HABs in seamounts and their role in shaping the composition and the occurrence of HABs in coastal water.

Metal complexation, FT-IR characterization, and plankton abundance in the marine surface microlayer of coastal areas in the Eastern Mediterranean

Barely any data exist on metal speciation in the marine surface microlayer (SML), a rather complex environment, the study of which contributes to enhancement of knowledge on metal speciation and its effect to the ocean. Metal speciation is significant since life requires a wide variety of trace metals that are essential for the growth of the organisms. Ligand concentrations (L) of copper (Cu), zinc (Zn), and cadmium (Cd) were studied by anodic stripping voltammetry (ASV) in the SML of coastal areas within the Aegean Sea in the Eastern Mediterranean. Complexing capacities in the SML in decreasing order ranged for Cu from 29 to 201 nM (median 101 nM), for Zn 24–149 nM (45 nM), and for Cd 1.0–1.5 nM (1.4 nM). Average enrichment factors (EFs) of SML samples compared to subsurface ones (SSW) were calculated equal to 0.9 ± 0.8, 1.2 ± 0.5, and 1.7 ± 1.6 for LZn, LCu, and LCd, respectively. In five out of the six total paired samples of SML and SSW, lower concentrations of LZn were measured in the SML, which is not the case for LCu and LCd. Due to elevated dissolved Zn concentrations in the SML, its complexation is incomplete, contrary to those of Cu and Cd, which are fully complexed. These trace metals are essential nutrients for biological functions, hence any differences on their concentration and chemical speciation may directly influence the distribution of phytoplankton species in the upper water column and neuston. EFs of SML relatively to subsurface water ranged in average between 1.2 and 2.4 for total organic carbon (TOC), chlorophyll a (Chla), and plankton, being generally >2 for most of the amino acids detected, demonstrating a relative enrichment of the SML in organic matter. A significant correlation was found between Cu ligands and dinoflagellates <20 μm, confirming older findings supporting that marine dinoflagellates of Gymnodinium genera produce Cu ligands. New insights are provided in the study and the importance of investigating bio-essential metal ions (Cu, Zn, Cd) and their organic complexes in the SML is pointed. Data on Zn and Cd complexing capacities in the SML are the first published so far.

Sources of polyamines in coastal waters and their links to phytoplankton

Polyamines are key components of labile dissolved organic nitrogen in coastal waters. They are found in all living organisms, which are the sources of dissolved organic matter in marine environments. The concentrations of dissolved polyamines are generally low and are controlled as much by production as by consumption. Understanding the dynamics of intracellular pools of polyamines could provide insight to their dynamics in the environment and their potential contribution to ecosystem processes. We measured the concentrations of 6 common polyamines (putrescine, cadaverine, norspermidine, spermidine, norspermine and spermine) extracted from particles in water samples collected on the continental shelf of the South Atlantic Bight (SAB). The total concentrations of extractable polyamines (EPs) decreased from inshore to the shelf-break of the SAB, following a pattern similar to chlorophyll a and opposite to salinity. The composition of EPs was highly correlated with the distribution of phytoplankton species assessed as the abundance of diatom 18S rRNA genes, and with densities of picoeukaryote, Synechococcus and Prochlorococcus cells, suggesting that phytoplankton are the primary source of EPs, followed by a freshwater or nearshore source. Our data suggest that putrescine, norspermidine and spermidine are released primarily from diatoms and picoeukaryotes, while Synechococcus and dinoflagellates are the likely sources of norspermine and spermine.

AN INVESTIGATION OF PHYSICOCHEMICAL PARAMETERS AND PHYTOPLANKTON COMMUNITY STRUCTURE OF EKO-NDE RESERVOIR IN OSUN STATE, NIGERIA

This research was carried out to determine the relationship between physicochemical variables and phytoplankton community of the Eko-Nde reservoir. Changes in physicochemical parameters of aquatic ecosystems have significant impact on the species that live therein. Eko-Nde reservoir is of socio-economic significance to communities that surround it, which necessitates a proper study of the phytoplankton composition and environmental status of the reservoir. Water samples were collected from two stations in the reservoir from January 2019 to August 2019. The physicochemical parameters that were determined include but not limited to temperature, total hardness, pH and biochemical oxygen demand. The composition and diversity of phytoplankton were analyzed. A total of 2039 cells ml-1 belonging to four (4) major divisions were dominant in the order; Bacillariophyta (898 cells ml-1) > Charophyta (788 cells ml-1) > Chlorophyta (302 cells ml-1) > Cyanophyta (51 cells ml-1). Principal Component Analysis and Canonical Corresponding Analysis showed that certain physicochemical variables such as temperature, pH and total hardness were key drivers of the phytoplankton community structure of the reservoir. Diversity indices showed moderate abundance and distribution of phytoplankton species, with the highest diversity of species in the months associated with the rainy season. The appearance of pollution tolerant species such as Anabaena circinalis, Oscillatoria limosa, Nitzschia gracilis, Cymbella mexicana, Pediastrum boryanum, Synedra ulna, Cyclotella meneghiniana and Gomphonema spp. suggest that the reservoir was on the verge of pollution. Anthropogenic activities around the reservoir should be closely monitored to avoid health risks to humans and endangerment of aquatic organisms.

Spatial and temporal variations of phytoplankton composition and biomass in Lake Bunyonyi, South-Western Uganda.

The purpose of this study was to examine the spatial and temporal variations of phytoplankton species composition and biomass in Lake Bunyonyi, South-Western Uganda. Samples were collected monthly from nine fixed stations in the lake from October 2019 to September 2020. Based on the morphological characterization, 52 different species of phytoplankton were recorded. These were dominated by cyanobacteria (21 species) and chlorophytes (15 species) followed by diatoms (10 species), euglenophytes (4 species), dinoflagellates (2 species), and cryptophytes (1 species). The biomass (Chl-a concentration) ranged from 0.019 ± 0.009mg/L at Heissesero station to 0.045 ± 0.013mg/L obtained at Nyombe station. On a temporal basis, the highest mean Chl-a concentration of 0.044 ± 0.03mg/L was recorded in March 2020while the least concentration of 0.015 ± 0.011mg/L was obtained in September 2020. Significant differences existed in the Chl-a concentration values between stations and across sampling months. Chl-a concentration was significantly positively correlated with dissolved oxygen (DO), turbidity but negatively correlated with temperature. The Shannon-Wiener index and evenness put it clear that the distribution of phytoplankton species in the lake is inequitable. Besides, 94.2% of the phytoplankton species revealed had never been reported by the previous studies in the study area. The dominance of species cyanobacteria (such as Microcystis spp., Cylindrospermopsis raciborskii, Anabaenopsis sp., and Anabaena sp.) presents potential future challenges to water quality management. Therefore, the establishment of a strong and committed committee dubbed "Lake Bunyonyi Water Management Committee" to oversee the activities and avert potential water quality challenges is strongly recommended. The existence of some toxic phytoplankton species calls for regular monitoring and careful use of the lake and its food products.

Climate change in the Baltic Sea region: a summary

Abstract. Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge of the effects of global warming on past and future changes in climate of the Baltic Sea region is summarised and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focuses on the atmosphere, land, cryosphere, ocean, sediments, and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in palaeo-, historical, and future regional climate research, we find that the main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, for Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution, and new scenario simulations with improved models, for example, for glaciers, lake ice, and marine food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth system have been studied, and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication, and climate change. New datasets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal timescales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first palaeoclimate simulations regionalised for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA), and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics are dominated by tides, the Baltic Sea is characterised by brackish water, a perennial vertical stratification in the southern subbasins, and a seasonal sea ice cover in the northern subbasins.

Таксономический состав и численность планктонных водорослей в водах Западной Антарктики (февраль–март 2020 г.)

Diversity, quantitative development and distribution of phytoplankton species were investigated. The study area included southeastern part of the Ross Sea (near Roosevelt Island) (station 3), transect 1 along the 156°W (Ross Sea at Cape Colbeck), near Russkaya station (transect 2) along the 138°W and the Bransfield Strait (transect 3) in February-March 2020, based on the data of 65th Russian Antarctic Expedition. 49 algae taxa from 7 divisions with a predominance of diatoms were identified in the phytoplankton. The spatial distribution of phytoplankton was characterized by heterogeneity which is associated with currents in the study areas, ice conditions, climatic and thermohaline factors. Development of diatoms is typical to the entire studied area. The dominant species (more than 10% of the algae population) were representatives of the genera Fragilariopsis, Chaetoceros, Actinocyclus, Corethron and Phaeocystis. The highest phytoplankton abundance (up to 264×103 cells/l) were obtained for transect 2 stations.

Biodiversity in the occurrence of different species of phytoplankton along the Chennai coast

Phytoplankton is the major food of zooplankton and small pelagic occurring along the Chennai coast. The distribution of phytoplankton vary from place to place and the occurrence of different species decides the biodiversity of the ecosystem. This paper describes the occurrence and the characteristics of most common phyto organisms along the Chennai coast using primer 6.0 software. The phytoplankton distribution consists of dissolved volume, Ceratium species, Navicula, Bidulphia, Nitzschia, Gyrosigma and Chlorella during the year’2011. The occurrence of the phytoplankton, Chaetoceros, 38.01%, followed by Thalasirrothrix is 11.95%, Nitzschia is 8.94%, Navicula, 8.19%, Gyrosigma is 7.22%, Bidulphia is 6.57%, Coscinodiscus, 5.85%, Pleurosigma, 5.81%, Ceratium species, 4.58%, Chlorella is 2.74% and dissolved volume is 0.03% of the total phytoplankton distribution. The primer graphs for eclidean distance of different months for different species of phytoplankton were drawn. From the bray Curtis similarity graph it is evidenced that the distribution of phytoplankton component. Chaetocerus is far from the other species since its occurrence is more during the month of Jan’11. From the similarity graph, it is found that Chaetoceros and Coscinodiscus are closely related, Ceratium species and Pleurosigma are closely related, Navicula and Bidulphia are closely related. The occurrence of Chlorella is not closely related to any species. Bubble plots displays the individuals species abundances in relation to the overall community pattern. Funnel graphs are drawn for the number of phytoplankton. As the temperature increases during the summer month the phytoplankton decreases. The environmental variables, temperature, pH, salinity, TSS, TDS, dissolved oxygen, chlorophyll a, b and c, primary productivity, gross and net, nutrients, phosphate and ammonia vary significantly with the phytoplankton occurrence. The correlation coefficient of occurrence of Ceratium-Nitzschia (0.78), Ceratium- Thalassirothrix-(0.98), Ceratium- Pleurosigma (0.90), Navicula-Bidulphia (0.57), Navi cula-Nitzscia (0.10), Navicula -Gyrosigma (0.95), Navicula- Chaetoceros (0.93), Navicula- Coscinodiscus (0.57), Navicula-Pleurosigma (0.19), Bidulphia-Nitzschia (0.50), Bidulphia - Gyrosigma (0.31), Bidulphia- Chaetoceros (0.25), Bidulphia- Coscinodiscus (0.94), Nitzschia-Thalassirothrix (0.82), Nitzschia-Coscinodiscus (0.34), Nitzschia-Pleuro -sigma (0.64), Gyrosigma-Chaetoceros (0.99), Gyrosigma- Coscinodiscus (0.33), Gyro sigma-Pleurosigma (0.26), Chaetoceros-Coscinodiscus (0.26), Chaetoceros –Pleurosigma (0.30), Gyrosigma-Chlorella (0.09), Chaetoceros-Chlorella (0.05). The species richness, d varies from 0-2.40, Pielous’s index of evenness (J') varies from 0-0.97, Shannon–Wiener’s diversity index (H'), 0-2.32, simpson’s dominance index, , 0-0.9. The species richness, species evenness, species diversity and dominance index are all significant at p  0.05. The correlation between the environmental variables and the phytoplankton species distribution were worked out.

Effects of Kaduna Refining and Petrochemical Corporation Effluents on the Abundance and Distribution of Phytoplankton Community along River Rido, Kaduna, Nigeria

The effects of effluent discharged from Kaduna Refining and Petrochemical Corporations (KRPC) on the Phytoplankton species distribution and abundance was studied along river Rido for a period of twelve months from February 2013 to January 2014. A total of Ninety-three (93) species of phytoplankton distributed in five divisions were recorded from four different study stations (A, B, C and D) along the river. Random sequential sampling was employed for selecting a sampling station. Physicochemical parameters were determined in accordance with the standard procedure for wastewater assessment guidelines of American Public Health Association (APHA). Phytoplankton identification was done using appropriate reference materials. The phytoplankton community was dominated by Bacillariophyta9 constituting 78.98% with 41 species, followed by Chlorophyta (6.67%) having 25 species, and then Cyanophyta (6.46%) having 12 species, while 10 species of Dinophyta and 5 species of Euglenophyta constituting 5.42% and 2.49% respectively were observed. The results from the study revealed low density of phytoplankton in station B, while high density of phytoplankton was observed in stations A and D. The physicochemical parameters showed both seasonal and spatial variations. Values of some parameters studied were observed to be above Federal Environmental Protection Agency (FEPA) limits at station B. Thus, effluent from KRPC is a source of contamination of water quality and adversely affects phytoplankton community along river Rido. Therefore, effluent retention facility should be established for long term treatment of effluent before discharge into the river

Bafa Gölü'nün (Türkiye) ekolojik ve trofik durumunun fitoplankton bazlı değerlendirilmesi

Phytoplankton groups are one of the major quality element to be used in the evaluation of the trophic and ecological state of freshwater ecosystems according to the EU Water Framework Directive. This research was made to assess the trophic and ecological status of Lake Bafa in Turkey, on the basis of phytoplankton communities. Büyük Menderes River is one of the most important factor that carries pollutants to Lake Bafa. The eight sampling station were assigned to evaluate the ecological and trophic state of the lake. Phytoplankton species were collected monthly for 2 years study period. Most commonly used phtoplankton indices Q index and Carlson’s Trophic State Index (TSI), and different versions of diversity indices were used to estimate trophic and ecological state of the lake. Similarities between the sampling stations were clustured by using the unweighted pair group method using arithmetic average (UPGMA), based on phytoplankton communities. Correlations between the applied indices were determined by using Pearson Correlation. After the identification of collected phytoplanktons, total of 63 taxa which belong to classis of Cyanophyceae (11.2%), Bacillariophyceae (49.2%), Chlorophyceae (23.8%), Xanthophyceae (1.5%), Euglenophyceae (11.2%) and Dinophyceae (3.1%) were detected. The 1st and 2nd stations were the most similar stations to each other (88%) according to phytoplankton communities. Secchi disc depth (SD) and TP played an important role in the distribution of phytoplankton species in Lake Bafa. The highest significant positive correlation was determined between Q and TSI (r = 0.987, p˂0.01). Considering the TDI values in the phytoplankton composition of the lake, it can be said that although the productivity status of the studied lake is still “mesotrophic”, it has a tendency towards “eutrophic” state. According to the Q values, the first five stations reflect the moderate ecological state, while the 6th, 7th and 8th stations represent the poor ecological state.

Phytoplankton species distribution around the fishing ground of Oma waters, Central Maluku, Indonesia

Oma water is directly related to the Banda Sea, which causes this water to have the highest diversity of fisheries resources. Oma waters is a potential fishing ground for small and big pelagic fishes. One of the most important pieces of information on the abundance of small fishes in this area is the abundance of phytoplankton. Until now, there was not any information available on phytoplankton species composition as well as its abundance. The objective of this research was to study the species composition of phytoplankton, its abundance and, some ecological indices. Sampling was carried out in April 2017 at a 14-fixed sampling station using Kitahara plankton net. Sampling was conducted vertically from 20 meters depth to the surface water. Hydrological parameters such as temperature, salinity, pH, and water transparency were measured in-situ. Nitrate and phosphate were analyzed in a chemical laboratory in LIPI-Ambon. The total of 65 phytoplankton species was identified from the study area and can be grouped into Bacillariophycea, Dinophyceae, and Cyanophyceae. Bacillariophycea has dominated this phytoplankton species composition (70.70%). A total abundance of phytoplankton in this study area varied from 1.09 × 105 cells l -1 to 5.70×105 cells l -1. The five dominant species found in this study were Guinardia flacida, Thalassionema nitzschioides. Skeletonema costatum, Thalassiosira gravida, Chaetoceros curvisetus, and The Shannon diversity index (H’) varied from 1.447 to 2.774. The evenness index (J’) was between 0.404 and 0.738. The dominance index was from 0.262 to 0.596. Phytoplankton abundance had a positive correlation with water transparency and salinity, whereas the number of phytoplankton had a positive correlation with seawater temperature and nitrate concentration

Identification of potentially harmful microalgal species and eutrophication status update in Benoa Bay, Bali, Indonesia

Harmful algal blooms (HABs) often occurred in a eutrophicated coastal areas, which causes ecological, economic, and health problems to the ecosystem and coastal communities. Benoa Bay is a coastal ecosystem in Indonesia which threatened by eutrophication and vulnerable to the occurrence of HABs in the future. This study focuses on identifying the potential harmful microalgal species and updating the trophic status in Benoa Bay. Sampling was done during the dry season in 2017 from 30 stations. Tewnty-nine species of phytoplankton were identified in Benoa Bay. Coscinodiscus spp., Pseudo-nitzschia spp., Skeletonema spp., Chaetoceros spp., Rhizosolenia spp., and Ceratium spp., were categorized as potentially harmful microalgal. Among those, Coscinodiscus spp. was the most abundant and widely distributed species in Benoa Bay. Phytoplankton cell density was highest in the area between Suwung Landfill and Floating Net Cage (16,584 cells L-1), while the lowest (20 cells L-1) was found in the Sama River estuary. The tb-RDA analysis showed salinity and dissolved oxygen percentage saturation (D%O) were two most significant factor that drives the density and distribution of phytoplankton species in Benoa Bay. In general, Benoa Bay was in the oligotrophic state based on phytoplankton abundance and chlorophyll-a concentration, while in mesotrophic states based on TRIX. The occurrence of some potentially harmful microalgal species, along with relatively high trophic levels in Benoa Bay, requires serious attention to prevent damages from any HABs event in the future.

Impact of flood regime on phytoplankton communities in the large African reservoir, Lake Nasser, Egypt

Lake Nasser is a reservoir of freshwater for drinking and irrigation in Egypt and it constitutes an important share in the fisheries sector. This study aims to acquire a better understanding of the status of phytoplankton distribution in Lake Nasser under the current flood regime and before the construction of the Grand Ethiopian Renaissance Dam (GERD). Samples were collected from fifteen sites representing different lake sectors along the main channel of the lake during 2016−2017. Approximately 103 species were recorded, belonging to six different classes, dominated by Cyanobacteria, Bacillariophyceae, Chlorophyceae, whereas Euglenophyceae, Dinophyceae and Chrysophyceae were rare. Based on the abundance of phytoplankton species, the pre-flood and post-flood seasons were very well discriminated. A major blooming of Cyanobacteria in the Tushka sector was detected during the pre-flood season, whereas this phenomenon diminished in the post-flood period when Bacillariophyceae and Chlorophyceae appeared. The results of this study indicated that the most important factors affecting phytoplankton species distribution during pre-flood and post-flood seasons are temperature, nutrients and total dissolved solids. The study confirms that flood regime substantially affects the phytoplankton abundance and distribution in Lake Nasser.

A VARIABILIDADE AMBIENTAL INFLUENCIA A COMPOSIÇÃO E BIOMASSA FITOPLANCTÔNICA DE UM RESERVATÓRIO NEOTROPICAL

Phytoplankton is an important model of the aquatic environments functioning, responding directly to environmental variability in space and time. Therefore, represents an excellent tool for the monitoring of reservoirs, which comprise highly heterogeneous ecosystems longitudinally, influencing the structure and distribution of phytoplankton species. The objective of this study was to investigate the variation in the composition and biomass of the phytoplankton in a reservoir in the Goiás state, Brazil, and how these organisms respond to environmental variability along the reservoir spatial extent in dry and rainy periods. The phytoplankton and environmental variables were collected during one dry period and other rainy, over seven sampling sites, distributed in the regions downstream of the dam, lacustrine, intermediate and lotic of the reservoir. The composition and biomass of the phytoplankton community were measured as a response to the spatial and temporal environmental variability. We recorded a spatio-temporal variation in water temperature, light, nutrients, and phytoplankton biomass. Cyanobacteria had the highest biomass in the lacustrine and intermediate regions, while diatoms in the lotic region, in both periods. The highest phytoplankton total biomass was recorded in rainy period. We recorded a clear relation between the phytoplankton biomass and the environmental variability, being that water temperature, turbidity and soluble iron the ones that showed the biggest influence on the biomass structure. Thus, the composition and biomass of the phytoplankton community can be important metrics of reservoirs functioning and, therefore, the phytoplankton study in these ecosystems it's of interest in their monitoring, since reservoirs have great ecological, economic or public health relevance

Iron and manganese co-limit growth of the Southern Ocean diatom Chaetoceros debilis.

In some parts of the Southern Ocean (SO), even though low surface concentrations of iron (Fe) and manganese (Mn) indicate FeMn co-limitation, we still lack an understanding on how Mn and Fe availability influences SO phytoplankton ecophysiology. Therefore, this study investigated the effects of Fe and Mn limitation alone as well as their combination on growth, photophysiology and particulate organic carbon production of the bloom-forming Antarctic diatom Chaetoceros debilis. Our results clearly show that growth, photochemical efficiency and carbon production of C. debilis were co-limited by Fe and Mn as highest values were only reached when both nutrients were provided. Even though Mn-deficient cells had higher photochemical efficiencies than Fe-limited ones, they, however, displayed similar low growth and POC production rates, indicating that Mn limitation alone drastically impeded the cell’s performance. These results demonstrate that similar to low Fe concentrations, low Mn availability inhibits growth and carbon production of C. debilis. As a result from different species-specific trace metal requirements, SO phytoplankton species distribution and productivity may therefore not solely depend on the input of Fe alone, but also critically on Mn acting together as important drivers of SO phytoplankton ecology and biogeochemistry.

Susceptibility of Two Southern Ocean Phytoplankton Key Species to Iron Limitation and High Light

Although iron (Fe) availability primarily sets the rate of phytoplankton growth and primary and export production in the Southern Ocean, other environmental factors, most significantly light, also affect productivity. As light availability strongly influences phytoplankton species distribution in low Fe-waters, we investigated the combined effects of increasing light (20, 200 and 500 μmol photons m−2 s−1) in conjunction with different Fe (0.4 and 2 nM Fe) availability on the physiology of two ecologically relevant phytoplankton species in the Southern Ocean, Chaetoceros debilis (Bacillariophyceae) and Phaeocystis antarctica (Haptophyceae). Fe-deficient cells of P. antarctica displayed similar high growth rates at all irradiances. In comparison, Fe-deplete C. debilis cells grew much slower under low and medium irradiance and were unable to grow at the highest irradiance. Interestingly, Fe-deficient C. debilis cells were better protected against short-term excessive irradiances than P. antarctica. This tolerance was apparently counteracted by strongly lowered growth and particulate organic carbon production rates of the diatom relative to the prymnesiophyte. Overall, our results show that P. antarctica was the more tolerant species to changes in the availability of Fe and light, providing it a competitive advantage under a high light regime in Fe-deficient waters as projected for the future.

The response of spring phytoplankton assemblage to diluted water and upwelling in the eutrophic Changjiang (Yangtze River) Estuary

A comprehensive study on the phytoplankton standing stocks, species composition and dominant species in the eutrophic Changjiang (Yangtze River) Estuary (CE) was conducted to reveal the response of phytoplankton assemblage to Changjiang Diluted Water (CDW) and upwelling in the spring. Phytoplankton presented peak standing stocks (13.03 μg/L of chlorophyll a, 984.5×103 cells/L of phytoplankton abundance) along the surface isohaline of 25. Sixty-six species in 41 genera of Bacillariophyta and 33 species in 19 genera of Pyrrophyta were identified, as well as 5 species in Chlorophyta and Chrysophyta. Karenia mikimotoi was the most dominant species, followed by Prorocentrum dentatum, Paralia sulcata, Pseudo-nitzschia delicatissima and Skeletonema costatum. A bloom of K. mikimotoi was observed in the stratified stations, where the water was characterized by low nitrate, low phosphate, low turbidity, and specific ranges of temperature (18–22 °C) and salinity (27–32). K. mikimotoi and P. dentatum accumulated densely in the upper layers along the isohaline of 25. S. costatum was distributed in the west of the isohaline of 20. Benthonic P. sulcata presented high abundance near the bottom, while spread upward at upwelling stations. CDW resulted in overt gradients of salinity, turbidity and nutritional condition, determining the spatial distribution of phytoplankton species. The restricted upwelling resulted in the upward transport of P. sulcata and exclusion of S. costatum, K. mikimotoi and P. dentatum. The results suggested that CDW and upwelling were of importance in regulating the structure and distribution of phytoplankton assemblage in the CE and the East China Sea.

Correction to 'A hypervariable mitochondrial protein coding sequence associated with geographical origin in a cosmopolitan bloom-forming alga, Heterosigma akashiwo'.

Geographical distributions of phytoplankton species can be defined by events on both evolutionary time and shorter scales, e.g. recent climate changes. Additionally, modern industrial activity, including the transport of live fish and spat for aquaculture and aquatic microorganisms in ship ballast water, may aid the spread of phytoplankton. Obtaining a reliable marker is key to gaining insight into the phylogeographic history of a species. Here, we report a hypervariable mitochondrial gene in the cosmopolitan bloom-forming alga, Heterosigma akashiwo . We compared the entire mitochondrial genome sequences of seven H. akashiwo strains from Japanese and North American coastal waters and identified a hypervariable segment. The region codes for a hypothetical protein with no defined function, and its variations between Japanese and North American isolates were prominent, while the sequences were more conserved among Japanese strains and North American isolates. Comparison of the sequence in isolates obtained from different geographical points in the Northern Hemisphere revealed that the sequence variations largely correlated with latitude and longitude (i.e. Pacific/Atlantic oceans). Our results demonstrate the usefulness of the sequence in determining the phylogeographic history of H. akashiwo .

A hypervariable mitochondrial protein coding sequence associated with geographical origin in a cosmopolitan bloom-forming alga, Heterosigma akashiwo.

Geographical distributions of phytoplankton species can be defined by events on both evolutionary time and shorter scales, e.g. recent climate changes. Additionally, modern industrial activity, including the transport of live fish and spat for aquaculture and aquatic microorganisms in ship ballast water, may aid the spread of phytoplankton. Obtaining a reliable marker is key to gaining insight into the phylogeographic history of a species. Here, we report a hypervariable mitochondrial gene in the cosmopolitan bloom-forming alga, Heterosigma akashiwo We compared the entire mitochondrial genome sequences of seven H. akashiwo strains from Japanese and North American coastal waters and identified a hypervariable segment. The region codes for a hypothetical protein with no defined function, and its variations between Japanese and North American isolates were prominent, while the sequences were more conserved among Japanese strains and North American isolates. Comparison of the sequence in isolates obtained from different geographical points in the Northern Hemisphere revealed that the sequence variations largely correlated with latitude and longitude (i.e. Pacific/Atlantic oceans). Our results demonstrate the usefulness of the sequence in determining the phylogeographic history of H. akashiwo.