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1

Measurements of chlorophyll content in freshwater phytoplankton

Chechelska Agnieszka, Ściężor Tomasz

Technical Transactions

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2026

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Vol. 123, iss. 1

art. no. e2026011

EN

This study investigates eutrophication in Kraków’s urban freshwater bodies by analysing chlorophyll-α concentrations, which indicate phytoplankton biomass. We measured chlorophyll-α using fluorescence in four lakes: Staw Płaszowski, Zalew Nowohucki, the pond in Park Lotników, and Staw Dąbski and applied the Trophic State Index (TSI) to evaluate their eutrophication levels. Staw Płaszowski showed stable, low chlorophyll-α levels, suggesting resistance to significant phytoplankton blooms. In contrast, Zalew Nowohucki exhibited notable chlorophyll-α fluctuations and peaks, indicating variable conditions and nutrient inputs. The pond in Park Lotników and Staw Dąbski also displayed variability with rapid chlorophyll-α peaks, indicating increased susceptibility to eutrophication. Cyanobacteria content varied, no cyanobacterial blooms reached critical levels. TSI classifications were: Staw Płaszowski as mesotrophic, Zalew Nowohucki as eutrophic, and the pond in Park Lotników as mesotrophic. Staw Dąbski showed seasonal fluctuations between mesotrophic and eutrophic states. Effective management requires a comprehensive approach, integrating multiple environmental factors and extensive sampling. Future research should focus on long-term monitoring and broader watershed considerations, including urban lakes, for effective eutrophication management.

2

Seasonal variations in phytoplankton community of Manyas Reservoir (Balıkesir, Turkey) in relation to certain physical and chemical variables

Çelik Kemal, Karasakal Mahide Balaban

Oceanological and Hydrobiological Studies

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2026

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Vol. 55, No. 1

62--72

EN

This study investigates the seasonal shifts in phytoplankton communities in the Manyas Reservoir (Balıkesir, Turkey) and their relationships with key physicochemical variables. A total of 59 taxa belonging to Heterokontophyta, Chlorophyta, Cyanobacteria, Euglenozoa, Charophyta and Miozoa were identified. The dominant species were Cyclotella meneghiniana, Fragilaria capucina, Nitzschia lorenziana, Navicula radiosa and Ulnaria acus from Heterokontophyta; Desmodesmus communis, Desmodesmus protuberans and Pediastrum simplex from Chlorophyta; and Trachelomonas volvocina from Euglenozoa. The analysis of the data clearly showed that electrical conductivity (EC), dissolved oxygen (DO), nitrate-nitrogen, total nitrogen (TN) and pH significantly shaped phytoplankton species distributions. The findings highlight the importance of hydrodynamics driving diatom dominance in turbulent zones contrary to the previous studies showing that high flow rates cause low diversity and abundance of phytoplankton in turbulent waters.

3

Seasonal exploration of water quality and bioindicators of an agricultural irrigation and drinking water reservoir: Armağan Dam Lake, Kırklareli, Türkiye

Aydin Gazel Burcu, Elipek Belgin, Güher Hüseyin, Öterler Burak

Oceanological and Hydrobiological Studies

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2025

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Vol. 54, No. 3

212--226

EN

This study aims to examine the water quality and dynamics of bioindicators (phytoplankton, zooplankton, and benthic macroinvertebrates) in the Armağan Dam Lake, a major freshwater reservoir that serves the drinking, domestic, irrigation, and industrial water needs of Turkey’s Thrace region. To achieve this, water and sediment samples were collected seasonally from three stations over 1 year. Results show that the water quality generally remains within acceptable limits, as defined by the World Health Organization (WHO) and the Surface Water Quality Management Regulation (SWQMR) standards for dam water. Regarding irrigation suitability, the sodium absorption rate (SAR) and magnesium rate (MgR) indices indicate that the lake is appropriate for irrigation. However, the Kelly index (KI) values are only marginally suitable, and the %Na Index suggests that it is unsuitable for irrigation. The Heavy Metal Pollution Index (HPI) indicates that the lake is free from heavy metal pollution (maximum of 98.72) and is safe for drinking. Based on the Metal Index (MI), Class II results were observed in autumn, while Class I results appeared in the other seasons. The Shannon– Wiener diversity index displayed low values (maximum H′ = 1.354) for the aquatic groups. Overall, the water quality parameters and biodiversity data suggest that the lake exhibits oligotrophic characteristics.

4

Effect of pollutants on phytoplankton biodiversity in the Tigris and Diyala Rivers in Baghdad Province

Alfalahi Hiba Adil, Aldhamin Ahmed S.

Journal of Ecological Engineering

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2025

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Vol. 26, nr 3

264--273

EN

The Tigris River is the second longest river in West Asia. It passes through densely populated areas, especially in the city of Baghdad. As a result of the demand for water that become at its highest levels. In contrast, the discharge of the Tigris River has decreased, in addition to the poor quality of the water of the Diyala River, which is one of the tributaries of the Tigris River on the Baghdad side, due to the increasing amounts of wastewater in it. In addition, the deficiency and poor quality of wastewater treatment plants, which in turn affects the life balance of living organisms, including phytoplankton, which is considered one of the components of the food chain for living organisms in the ecosystem. Wide differences exist among algal species in their requirements for nutrient metals or in their sensitivity to pollutants and thus the predominant effect of pollutants may well be on species composition of phytoplankton communities. Five sites were chosen (Saeda on the Tigris, Al-Multaqa on Diyala, Al-Tuwaitha on Tigris, Al-Jaara on the Tigris, and Jesr Enbopy on Diyala) from which samples were taken to measure heavy metals (Zn, Cu, Fe), chemical oxygen demand COD, pH, and phytoplankton were diagnosed in quantity and quality for three seasons (October, January, and March) Statistical techniques were applied and Shannon-Wiener diversity index (H) to evaluate the changes during the three seasons, and the results that the phytoplankton species showed a dominance of Cyanophyceae in quantity and quality in the study seasons, which is followed by Chlorophyceae and then Baciliariophyceae in quantity. As for quality, Cyanophyceae is followed by Baciliariophyceae and then Chlorophyceae with low specific density and high diversity according to the Shannon-Wiener index only in autumn with a high diversity of 3.39 at site 2 of the Diyala River, followed by spring with a diversity of 3.115 at site 1 of the Tigris River., The highest biomass of phytoplankton occurred in autumn, whereas the lowest biomass was in spring.

5

Potential carbon content by mangrove forest along the coastline of Trenggalek regency

Fahmi Muhammad Yunan, Muttaqin Andik Dwi, Ardiansyah Rizqi Eka, Anggreini Retno, Widyawati Syafira Salma Luna

Ecological Engineering & Environmental Technology

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2025

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Vol. 26, iss. 1

41--57

EN

This study focuses on estimating carbon stocks in Trenggalek’s forest and coastal areas, assessing their contributions to carbon sequestration and climate change mitigation. The study was conducted in two phases. First, a field-based estimation of carbon stocks was carried out for both mangrove and plantation forests, with 72 sample plots (10 × 10 m) laid out systematically. Above-ground biomass was calculated using an allometric model, while below-ground biomass was based on ratios of above-to-below ground biomass. Results showed that mangrove forests had an average carbon stock of 12.80, 23.45, and 76.15 tons/ha in above-ground biomass, below-ground biomass, and soil organic carbon, respectively, while plantation forests had higher values of 77.05, 114.2, and 75.76 tons/ha. The potential CO2 absorption also varied, with mangrove forests showing lower values due to their smaller biomass compared to plantation forests, though the mangroves had higher soil organic carbon storage. In parallel, the study evaluated the carbon uptake potential of coastal waters in Trenggalek Regency, based on primary productivity from phytoplankton. Sampling was done purposively, and carbon sequestration potential was calculated using the dark-light bottle method. The waters exhibited a mesotrophic state with primary productivity values ranging from 150–950 mgC/m³/day. The carbon uptake potential varied across stations from 3.69 to 23.35 tonsC/m²/year, indicating that coastal waters in Trenggalek Regency acts as a carbon sink, driven by a positive net primary productivity (NPP). Additionally, remote sensing techniques were used to analyze changes in land cover and carbon stock in Trenggalek’s coastal areas over time, using temporal Landsat data and Google Earth Engine. From 2001 to 2023, the carbon stock declined from 4,126,833.64 tons to 3,769,725.32 tons, but a slight increase is predicted by 2034 to 3,778,537.21 tons. These findings highlight the importance of field data in accurately predicting future carbon stock estimates, enhancing the understanding of forest and marine ecosystems roles in climate change mitigation and the importance of sustainable land use management to preserve carbon stock potential in Trenggalek’s ecosystems. The current research provides new insights into carbon stock estimation in the mangrove and plantation forests of Trenggalek, Indonesia. One of the key findings revealed for the first time is that, while mangrove forests have lower aboveground and belowground biomass compared to plantation forests, they possess significantly higher soil organic carbon content. This is primarily due to mangroves’ ability to trap carbon for longer periods in the soil due to anaerobic conditions. Moreover, the study highlights the carbon uptake potential of Trenggalek’s coastal waters, which act as a carbon sink, with primary productivity driven by phytoplankton. This is among the first studies to quantify the combined carbon sequestration from both forest ecosystems and coastal waters in Trenggalek, showing how these ecosystems contribute collectively to climate change mitigation .

6

Dynamics of phytoplankton functional communities in the South China Sea in response to multiple simultaneous stressors and ENSO-related climate anomalies

Ndah Anthony Banyouko, Di Pane Julien

Oceanologia

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2024

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No. 66 (4)

Art. no. 66404

EN

Phytoplankton is crucial in maintaining the functional integrity of marine ecosystems, shaping the delicate balance between the food web base and higher trophic levels. However, these organisms are also susceptible to environmental changes, with fundamental ecological implications. We investigated the response of four phytoplankton communities (diatoms, coccolithophores, chlorophytes, and cyanobacteria) to hydroclimatic parameters in the South China Sea (SCS) between 1998 and 2012, and ascertained the effects of El Niño and La Niña climatic anomalies on the niche preferences of these communities at interannual timescales. Overall, changes in temperature and NO3 jointly explained 51% of phytoplankton variability. Cyanobacteria was the most generalist taxon, displaying tolerance to both El Niño and La Niña conditions, justifying its relatively high abundance, increasing trend, and spatial expansion. Coccolithophore, the second most abundant community mainly in northern SCS was associated with La Niña-related conditions while diatoms were primarily associated with El Niño but displayed tolerance to both climatic regimes and a strong positive response to iron. Finally, chlorophytes were marginal under both El Niño and La Niña conditions indicating that inherent hydrographic constraints and competition limit their niche breadth and abundance. We concluded that non-linear interactions linked to El Niño drive interannual microbial dynamics in the SCS by modifying hydrographic and geochemical characteristics. Hence, we surmised that under accelerated ocean warming, cyanobacteria, and most likely dinoflagellates will dominate phytoplankton community structure with significant impacts on the food web and regional marine biogeochemistry.

7

Causes of eutrophication in small water reservoirs in urban areas

Ziółek Marta, Mięsiak-Wójcik Katarzyna, Kończak Magdalena, Pliżga Mariusz, Siwek Krzysztof, Chmiel Stanisław

Journal of Water and Land Development

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2024

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no. 63

208--221

EN

The aim of the study was to determine the causes of eutrophication in small urban water reservoirs located in the UMCS Botanical Garden in Lublin, supplied via surface and groundwater. The research (hydrological, hydrobiological, and hydrochemical), which included both field and laboratory work, was conducted during the growing season in the years 2022-2023. These ponds are fed by waters from the Czechówka River and, to a lesser extent, by groundwater (seepage). Both river and groundwater are characterised by high concentrations of mineral forms of nitrogen and phosphorus, ranging from 1.49 to 12.0 mg N∙dm-3 and 0.07 to 0.21 mg P∙dm-3, respectively. This contributes to the intensive development of phytoplankton, especially during the summer period, with diatoms dominating the phytoplankton structure. The trophic state of the ponds ranges from eutrophic to hypertrophic. The study showed that the high degree of eutrophication was due to the load of nutrients delivered by the waters of the Czechówka River. Despite having several times higher concentrations of mineral and total nitrogen than in the river water, the spring water feeding the ponds had a negligible impact on the quality of the pond water due to low flow rate (<0.5 dm3 ∙s-1). Therefore, the construction of urban ponds as part of green-blue infrastructure should consider the possibility of reducing nutrients through biogeochemical barriers and suspended sedimentation. It is also advisable to partially shade the water surface by planting trees in the shoreline zone to limit water heating and phytoplankton development.

8

Identification of Environmental Factors Determining the Diversity and Abundance of Phytoplankton in Menjer Lake, Wonosobo, Indonesia

Piranti Agatha Sih, Widyartini Dwi Sunu, Usr Diana Retna, Noviana Fariza

Ecological Engineering & Environmental Technology

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2024

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Vol. 25, iss. 2

272--280

EN

Phytoplankton are primary producers in aquatic ecosystems, their abundance is determined by environmental changes, so phytoplankton are often used as bioindicators of waters. The aim of this research was to determine the diversity and abundance of phytoplankton in Menjer Lake, to measure the environmental factors that determine the diversity and abundance of phytoplankton, and to determine the environmental factors that most influence the diversity and abundance of phytoplankton in Menjer Lake. This research uses a survey method in 5 areas (inlet, middle of the lake, aquaculture using floating net cage, tourism, and outlet). The parameters observed were the diversity and abundance of phytoplankton as well as the concentration of water quality parameters that determine the presence of phytoplankton (temperature, light penetration, pH, DO, TSS, TDS, PO4 and NO3). To determine the environmental factors that most influence the diversity and abundance of phytoplankton were analyzed using the principal component analyses method with Past 4.10 software. The community structure of phytoplankton in Menjer Lake was dominated by Bacillariophyta (83%). The factors determining the development of phytoplankton in Menjer Lake are influenced most by light penetration and PO4 concentration. The input of PO4 concentration from the water catchment area must be controlled to prevent phytoplankton blooming in Menjer Lake.

9

Application of geostatistical methods in the study of algae in water reservoirs: a review

Zawadzki Jarosław, Fabijańczyk Piotr

Ecological Chemistry and Engineering. S

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2024

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Vol. 31, nr 4

473--491

EN

The growing pollution of aquatic environments, primarily of anthropogenic origin, combined with global climate change, has led to significant increases in eutrophication. This process often results in harmful algal blooms (HABs) of phytoplankton and algae in various water bodies, including inland lakes, marshes, rivers, seas, and oceans. These blooms pose a serious threat not only to aquatic ecosystems but also to human health. Understanding phytoplankton and algal blooms is inherently complex, as these phenomena manifest on multiple spatial and temporal scales. Comprehensive studies of phytoplankton and algae require the collaboration of scientists from diverse scientific disciplines, including biology, ecology, and environmental science. One of the critical tools in this multidisciplinary approach is geostatistics, an advanced and continuously evolving branch of statistics that specialises in analysing spatial and temporal phenomena. Geostatistics is particularly well-suited for the study of phytoplankton and algal blooms due to its ability to handle data that varies across different scales and locations. This review presents and discusses selected studies that employ geostatistical methods to investigate plankton and algae in various water bodies. It highlights the most significant scientific works that, in the authors’ opinion, represent milestones in the application of these studies. Furthermore, various geostatistical methods are explored, ranging from variography to spatiotemporal modelling, providing insights into spatial and temporal patterns and their variability of phytoplankton and algal blooms in aquatic ecosystems.

10

Palynology of Carboniferous deposits (Zaręby Beds) from the Jabłonna IG 1 core and the Kowala Quarry (Holy Cross Mountains, Poland), Poland

Filipiak Paweł, Kondas Marcelina

Annales Societatis Geologorum Poloniae

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2024

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Vol. 94, No. 3

241--253

EN

Palynological samples from the Zaręby Beds (lower Carboniferous, Holy Cross Mountains) were investigated for palynostratigraphy and palynofacies. Samples, obtained from the Jabłonna IG 1 drill core (21 samples) and the Kowala Quarry (46 samples), allowed determinations of age, ranging from the HD (Cristatisporites hibernicus–Claytonispora disticta) miospore zones in the Kowala Quarry section, to the PC (Spelaeotriletes pretiosus–Raistrickia clavata) Miospore Zone in the Jabłonna section, which corresponds to middle and late Tournaisian. This confirmed the diachronism of these sediments. Land microflora and plant remains predominated over marine phytoplankton. The sections are diachronous; the palynofacies record is rather uniform at both sites, with a small difference in age between the investigated areas. The palynofacies study reveals the deposition close to the source area for the land material. Moreover, the presence of amorphous organic matter, obtained from black shales and cherts, suggests a relatively deep and anaerobic sea bottom conditions.

11

Effects of the tide on the temporal and spatial physicochemical structure of the Kienké river estuary (South Atlantic Coast of Cameroon, Kribi) and its phytoplankton

Mama Anselme Crépin, Ghepdeu Gisele Flodore Youbouni, Fossi Tankoua Olivia, Bonga Manfred Desire, Abouga-Bodo Willy Karol, Mandeng Thérésa Irma, Owona-Edoa François Désiré, Tangko Noel Chuye, Ngoupayou-Ndam Jules Rémi

Oceanological and Hydrobiological Studies

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2023

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Vol. 52, No. 1

20--40

EN

The present work aimed to understand the physicochemical and phytoplanktonic structure of the Kienke estuary water in the urban area of Kribi town in relation to human activities and fluvial or oceanic influences. Field investigations and laboratory work were devoted to the sampling and measurement of some physicochemical and biological parameters, specific treatments and classical statistics (descriptive, multidimensional) of variables. Estuary water is characterised by an instability and spatio-temporal variations in its physicochemical parameters. The most sensitive parameters are as follows: a temperature ranging between 22.6°C and 31°C under the influence of atmospheric variations, electrical conductivity and salinity that are relatively high (0.22 < C. E < 49.70 mS cm-1; avg =16.56 mS cm-1; 0 < Sal < 29.32 PSU; avg = 11.51 PSU), and a pH that is overall acidic to basic (6 < pH < 8.86; avg = 7.75 ± 0.82). The nutrients variation (ammonium, nitrite, nitrate and orthophosphate) is very low in space and time, with a longitudinal distribution controlled by tidal flows, river flows and the biological pump. For the 64 samples collected, 167 phytoplankton taxa were identified. The most abundant (36.36%) were Chrysophyta Division, followed by Chlorophyta. Species richness is marked by brackish water taxa. According to this structure and the combination of both gradients, mineratilisation and organic matter enrichment is of a physicochemical typology, and the biotypology is hydrotypologically dependent.

12

The influence of biochemical parameters on primary production in the Gulf of Gdańsk region : A model study

Janecki Maciej, Dybowski Dawid, Dzierzbicka-Głowacka Lidia

Oceanologia

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2023

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No. 65 (4)

517--533

EN

Understanding the changing levels of biochemical parameters and the factors that influence them throughout the seasons is crucial for comprehending the dynamics of marine ecosystems. It also helps us identify potential threats that could harm their condition, aiding decision-making processes related to their protection. This study focuses on examining the variations in nutrients (such as nitrates, phosphates, and silicates), dissolved oxygen, and phytoplankton within the Gulf of Gdańsk. Additionally, we analyze the primary production process at three representative locations. To achieve this, we used data from the EcoFish biochemical numerical model. To ensure the model's accuracy, we compared its results with in situ data from the ICES database. The comparison revealed high correlations and minimal errors. Furthermore, we investigated how limiting factors impact primary phytoplankton production and demonstrated how the intensity of spring diatom blooms influences the nature of cyanobacterial blooms in the summer.

13

Phytoplankton Dynamics and Its Relation to Physicochemical Parameters in the Dry Season of Maninjau Lake, West Sumatra, Indonesia

Komala Puti Sri, Silvia Shinta, Windi Sherina

Journal of Ecological Engineering

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2023

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Vol. 24, nr 9

218--231

EN

Physicochemical parameters play a significant role in determining phytoplankton structure and dynamics in the lake. The present study investigated the phytoplankton dynamics and their correlation with physicochemical parameters in the dry season of Maninjau Lake. The parameters measured, including temperature, transparency, pH, DO, TN, and TP concentrations, were collected from seven lake locations, i.e., in the middle of the lake, near domestic, hydropower, endemic fisheries, and aquaculture cage areas, and inlet-outlet rivers. Phytoplankton samples were collected from the middle of the lake, near domestic and aquaculture cage areas. TSI analysis shows that Maninjau Lake was hypereutrophic, with an average TSI of 101.15. The phytoplankton community comprises six classes and 22 species dominated by Microcystis aeroginosa and Synedra acus. Bacillariophyceae had the highest phytoplankton concentration, while Cyanophyceae had the highest density. The diversity and equity index of the phytoplankton community structure were low and less evenly distributed, confirming that the lake was hypereutrophic. The highest diversity index was found in the middle of the lake or the most profound part, while the lowest was near the domestic area. Among the physicochemical parameters, transparency has a strong correlation with dominant phytoplankton.

14

Impact of Water Stress on the Planktonic Biodiversity of the Youssef Ben Tachafine Dam (Souss Massa, Morocco)

Boudarfa Fatima, Gallouli El Mahjoub, El Hafa Mohamed, Aamiri Ahmed, Oulad Ali Hassan

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 8

97--106

EN

Drought is a large-scale disturbance that affects freshwater ecosystems worldwide. This recurrent phenomenon in Morocco, has experienced severe episodes during the last decade and has caused water stress in several aquatic ecosystems including the Youssef Ben Tachafine dam. Indeed, the volume of this reservoir has experienced its lowest historical hydrological level (12%) during the study period. To study the effects of water stress on water quality and planktonic community structure, water samples were collected from January 2019 to December 2020 at nine depths. The physicochemical parameters of the water were measured in parallel with the qualitative and quantitative study of the phytoplankton and zooplankton communities. The results obtained show a low planktonic diversity with only 43 phytoplanktonic species and 27 zooplanktonic species. The phytoplankton showed an almost permanent predominance of Chlorophyceae (85%), dominated by Closterium pronum, followed by Diatomophyceae (9.5%), dominated by Cyclotella ocellata. Rotifers represent the most abundant zooplanktonic group during the study period with two dominant species (Keratella tecta and Polyarthra vulgaris). Statistical analysis of the data from this study, using R software, revealed a negative correlation between Cladoceran species, Copepods and the diatom Cyclotella ocellata on the one hand and the decrease in water level, temperature and enrichment of the environment in nutrients and phytoplanktonic biomass on the other. This study shows that the effect of the extreme drought, which the Youssef Ben Tachafine dam has experienced, has altered the diversity and structure of planktonic communities, which threatens the sustainability of ecological services of this ecosystem.

15

Correlation Between Surface Water Quality and Plankton Composition in Water Bodies in Hau Giang Province, Vietnam

Quang Truong Chi, Giao Nguyen Thanh

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 4

1--14

EN

The study was carried out to assess surface water quality in water bodies in Hau Giang province, Vietnam using individual surface water quality parameters and water quality index. In addition, the correlation of phytoplankton and zooplankton composition with surface water quality was also examined. The results showed that surface water quality in Hau Giang province was contaminated with organic matters, nutrients, iron and microorganisms. The water quality index (WQI= 37-84) showed that surface water ranged from moderate to good. A total of 164 species belonging to five phyla of phytoplankton were recorded with the density from 370–2260 individuals/L and 91 species belonging to five phyla of zooplankton with a density of 11,332–121,600 individuals/L. The predominance of the phytoplankton species Oscillaroria, Euglena, Phacus and the predominance of zooplankton species of the Nauplius, Rotifera and Protozoa signalize an aquatic environment rich in organic matters and nutrients. The correlation results showed that BOD, COD, NH4+-N, NO3--N and PO43--P were closely related to the density of phytoplankton while pH, DO, BOD, NH4+-N and coliform play an important role in determining the density of zooplankton species.

16

Temporal variations of phytoplankton community and their correlation with environmental factors in the coastal waters of the Çanakkale Strait in 2018

Demir Egemen ̇Inan, Turkoglu Muhammet

Oceanologia

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2022

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No. 64 (1)

176--197

EN

In order to investigate temporal variations in phytoplankton connected with hydrography, high-resolution (twice a week) samplings were carried out between January and December 2018 at a single, shallow water station in the Dardanelles. Diatoms dominated in early and mid-winter, late spring and early summer, and between August and October. Whereas dinoflagellates dominated in the period from mid-February to the end of the third week of May, mid-summer, and late autumn. Other groups were generally more abundant in the early summer and mid-autumn than any other period. Late spring and early summer, mid-autumn and middle winter were the important bloom periods. The average contribution of diatom abundance (5.00 × 105±7.80 × 105 cells L−1) to average total phytoplankton abundance (9.63 × 105±7.88 × 105 cells L−1) was above 50% (average: 51.88%) during the year except spring (34.32%). However, the average contribution of dinoflagellates (43.32±20.69%) and others (4.81±6.99%) to the total phytoplankton abundance were lower than the abundance of the diatoms (51.88±21.61%). The study revealed a decrease both in the total number of algal blooms which also included HABs and their densities in the region compared to the previous findings. These observations seem to evidence environmental status improvement of the investigated area, manifested in an average chlorophyll a concentration (0.71±0.52 µg L−1) and quantitative phytoplankton structure (103 to 105 cells L−1).

17

Size-fractionated primary production in the south-eastern Black Sea

Agirbas Ertugrul, Bakirci Mustafa

Oceanologia

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2022

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No. 64 (2)

244--266

EN

Size-fractionated primary production (PP) and chlorophyll-a (Chl-a) with phytoplankton abundance and nutrients were investigated in the south-eastern Black Sea from November 2014 to August 2015. A 14C radio-tracing technique was used to estimate phytoplankton primary production. C-14 experiments revealed that total PP ranged from 295 mgC m−2 d−1 to 5931 mgC m−2 d−1 along the study area. Size-fractionated PP varied from 84 to 1848 mgC m−2 d−1, from 96 to 3156 mgC m−2 d−1 and from 56 to 3363 mgC m−2 d−1 for pico-, nano- and microphytoplankton, respectively. Overall, winter (4163 mgC m−2 d−1) and spring (5931 mgC m−2 d−1) were the most productive seasons, which coincided with high phytoplankton abundance. Contributions of microphytoplankton and nanophytoplankton were prominent in spring with maximum PP values. Winter was the second productive season with high contributions of nano- and microphytoplankton PP. Summer and autumn were less productive seasons, which were characterised by a high contribution of pico- and nanophytoplankton PP. Dinoflagellates were represented with the highest species richness (68 species, 53.54%) and diatoms were the second group along the area. Diatoms and other phytoplankton species (mainly Emiliania huxleyi) were the most abundant groups in terms of quantitative contribution. The results show that microphytoplankton along the study area are responsible for the majority of PP. However, the measured high Chl-a against low size-fractionated PP clearly indicates that smaller groups (i.e., pico- and nanophytoplankton) were dominant during these periods. Hence, the quantification of size-fractionated PP rates together with ecological indicators will allow for a more comprehensive assessment of the Black Sea ecosystem.

18

Noctiluca blooms intensify when northwesterly winds complement northeasterlies in the northern Arabian Sea: Possible implications

Sarma Nittala Subrahmanya, Baliarsingh Sanjiba Kumar, Pandi Sudarsana Rao, Lotliker Aneesh Anandrao, Samanta Alakes

Oceanologia

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2022

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No. 64 (4)

717--734

EN

Wind systems are known as nutrient sources playing significant roles in the oceanic realm and global climate oscillations. This study explores, for the first time, the effect of winds on the winter blooms of the mixotrophic dinoflagellate, the green variant of Noctiluca scintillans (NSG) in the northern Arabian Sea. When the NSG abundance was lower (i.e., <∼10000 cells l−1), it was coupled to silicic acid (H4SiO4), on which diatoms (phytoplankton) in turn depended. At higher abundance (i.e., NSG>∼10000 cells l−1), H4SiO4 and H4SiO4:DIN (dissolved inorganic nitrogen) ratio fell. The NSG was then intensely green and chlorophyll-a richer, attributed to a change in the mode of NSG's nutrition from heterotrophy to autotrophy-dominance. The back-trajectory model revealed that the winds were mostly northeasterly (NE) initially (during February) and were north-westerly (NW) towards the end of winter (March). Separately for the NE and NW winds, the NSG abundance was 10655±18628 and 28896±46225 cells l−1, respectively. The H4SiO4:DIN ratio correspondingly reached <0.2 and ≥0.4. The NSG was modelled with high significance (p<0.001, N=33) versus the NE and NW wind speeds. Thus, while the NE winds deepened the mixed layer and caused nutrient enrichment and phytoplankton production, the NW winds facilitated the recovery of the H4SiO4:DIN ratio and economical use of H4SiO4 for phytoplankton production. It is hypothesized that this process is helped by iron input from NW desert winds during the latter part of winter when the NSG blooms intensify.

19

Multivariate approach to evaluate the factors controlling the phytoplankton abundance and diversity along the coastal waters of Diu, northeastern Arabian Sea

Kumar Ponnusamy Sathish, Venkatnarayanan Srinivas, Pandey Vikas, Ratnam Krupa, Jha Dilip Kumar, Rajaguru S., Dharani Gopal, James Rathinam Arthur, Atmanand Malayath Aravindakshan

Oceanologia

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2022

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No. 64 (2)

267--275

EN

The present study investigated the phytoplankton assemblage and diversity with physicochemical parameters of Diu coastal waters in different seasons during 2018–19. During the study period, 61 phytoplankton species comprising diatoms (50 sp.), dinoflagellates (8 sp.), and cyanophyceae (3 sp.) were recorded. Diatom was found to be a major community and contributed 79 to 99% of total phytoplankton abundance. Reduction in dinoflagellate and dominance of pennate-diatoms were observed during the monsoon. Chlorophyll-a concentration also showed a similar trend and decreased during the monsoon. However, the phytoplankton abundance was low particularly during the monsoon which might be due to the elevated total suspended solids (TSS) load. Canonical correspondence analysis revealed that diatoms were able to survive in high TSS with the support of high nutrients; while dinoflagellates were limited due to those conditions. Overall, the reduction in phytoplankton abundance, diversity, and biomass was recorded due to the elevated TSS input along the coastal waters of Diu.

20

Asterionellopsis glacialis (Family: Fragilariaceae, Class: Bacillariophyceae, Phylum: Ochrophyta) bloom and its impact on plankton dynamics at Kalpakkam (Bay of Bengal, Southeast coast of India)

Sahu Gouri, Mohanty Ajit Kumar, Sarangi Ranjit Kumar, Satpathy Kamala Kanta

Oceanologia

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2022

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No. 64 (1)

145--149

EN

An intense bloom of Asterionellopsis glacialis (Family: Flagilariaceae; Class: Bacillariophyceae; Phylum: Ochrophyta) was observed in the near-shore waters at Kalpakkam, Tamil Nadu. Proliferation was supported by the favorable temperature, salinity, and nutrient levels in the coastal waters prevailing in the post-northeast monsoon period. BIOENV analysis and PCA confirmed salinity and nitrate as the key environmental factors responsible for the A. glacialis abundance. Cluster analysis further supported the distinct state of coastal water during the bloom with respect to physicochemical properties. The bloom period was floristically and faunistically richer than the pre- and post-bloom periods. The cluster and nMDS analysis confirmed the effects of bloom on plankton dynamics in the near-shore waters at Kalpakkam. The dominance of meroplankters especially, Cirripedia nauplii and Bivalvia larvae over Copepoda during the peak bloom period, was a significant result of the study. PCA ordination plot for the quantitative aspects of phytoplankton and zooplankton groups further supported the above observation. Among Copepoda, Cyclopoida and Poecilostomatoida (mostly carnivorous) exceeded the Calanoida (mostly herbivorous) during the peak bloom period unlike the reverse trend observed during other periods. Fish eggs and larvae were available in substantial numbers during the bloom which indicated their proliferation in the presence of the blooming diatom standing stock as the food material.