Future Blooms Research Articles

Ulva lactuca blooms through the eyes of fishers: Threats to vulnerable coastal communities

Eutrophication intensifies Harmful Macroalgae Blooms (HMBs) in coastal environments, reducing habitat suitability for organisms and creating significant challenges for small-scale artisanal fishers. Leveraging fishers' memories, we analyzed over 20 years of data on Ulva lactuca blooms and their effects on fishing activities and fish resources in a tropical semi-arid region of Brazil. We estimated the timing, seasonality, and impacts of these bloom episodes on fish catches, fishing gears, and fishery revenues. Since 2010, blooms have become more frequent, particularly during dry seasons in shallow estuaries, likely exacerbated by nutrient enrichment, extended water residence time, and inadequate wastewater treatment. Net-based gear is particularly affected, with fish catches decreasing by up to sevenfold during bloom seasons, leading to income losses of approximately 50 %. Addressing eutrophication through active public policies on effluent treatment is crucial to mitigating economic impacts on vulnerable communities and managing future blooms, which are expected to worsen with climate change.

EstuarySAT Database Development of Harmonized Remote Sensing and Water Quality Data for Tidal and Estuarine Systems.

Researchers and environmental managers need big datasets spanning long time periods to accurately assess current and historical water quality conditions in fresh and estuarine waters. Using remote sensing data, we can survey many water bodies simultaneously and evaluate water quality conditions with greater frequency. The combination of existing and historical water quality data with remote sensing imagery into a unified database allows researchers to improve remote sensing algorithms and improves understanding of mechanisms causing blooms. We report on the development of a water quality database "EstuarySAT" which combines data from the Sentinel-2 multi-spectral instrument (MSI) remote sensing platform and water quality data throughout the coastal USA. EstuarySAT builds upon an existing database and set of methods developed by the creators of AquaSat, whose region of interest is primarily larger freshwater lakes in the USA. Following the same basic methods, EstuarySAT utilizes open-source tools: R v. 3.24+ (statistical software), Python (dynamic programming environment), and Google Earth Engine (GEE) to develop a combined water quality data and remote sensing imagery database (EstuarySAT) for smaller coastal estuarine and freshwater tidal riverine systems. EstuarySAT fills a data gap that exists between freshwater and estuarine water bodies. We are able to evaluate smaller systems due to the higher spatial resolution of Sentinel-2 (10 m pixel image resolution) vs. the Landsat platform used by AquaSat (30 m pixel resolution). Sentinel-2 also has a more frequent revisit (overpass) schedule of every 5 to 10 days vs. Landsat 7 which is every 17 days. EstuarySAT incorporates publicly available water quality data from 23 individual water quality data sources spanning 1984-2021 and spatially matches them with Sentinel-2 imagery from 2015-2021. EstuarySAT currently contains 299,851 matched observations distributed across the coastal USA. EstuarySAT's primary focus is on collecting chlorophyll data; however, it also contains other ancillary water quality data, including temperature, salinity, pH, dissolved oxygen, dissolved organic carbon, and turbidity (where available). As compared to other ocean color databases used for developing predictive chlorophyll algorithms, this coastal database contains spectral profiles more typical of CDOM-dominated systems. This database can assist researchers and managers in evaluating algal bloom causes and predicting the occurrence of future blooms.

Control of Cyanobacterial Algal Blooms and Soluble Reactive Phosphorus Using PAK-27 and Phoslock®

Cyanobacterial harmful algal blooms (cHABs) can pose a threat to human health and aquatic ecosystems when they release cyanotoxins in water. This research used samples from two northeastern reservoirs in Ohio and assessed (i) the effectiveness of two PAK-27 dosages, (ii) the potential interference of natural organic matter (NOM) on PAK-27 effectiveness, and (iii) the ability of Phoslock® to adsorb phosphorus released during cell lysis to prevent future bloom formation. PAK-27 was applied in either a quarter (15 mg) or full (58 mg) dose in 1.6 L. Two sets of jars were amended with 200:1 Phoslock®:phosphorus 24 h after PAK-27 application to assess the adsorption of phosphorus released upon cell lysis. A final set of jars was amended with 5 mg NOM to evaluate if NOM would interfere with PAK-27 effectiveness. Quarter and full doses of PAK-27 significantly decreased total phycocyanin content within 2 days of application (p < 0.05). However, the addition of 5 mg NOM influenced nutrient availability and algal response. All jars that received algaecide had increased extracellular microcystin levels (p < 0.05). Although Phoslock® adsorbed soluble reactive phosphorus (SRP), jars treated with only PAK-27 or amended with 5 mg NOM reduced more SRP than Phoslock®.Graphical

Continuous Sargassum monitoring across the Caribbean Sea and Central Atlantic using multi-sensor satellite observations

Recurrent transnational Sargassum blooms across the Caribbean Sea and Atlantic Ocean have received growing attention. Different multispectral sensors, including Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imager Radiometer Suite (VIIRS), and Ocean and Land Color Instrument (OLCI), have been used to map their distributions. However, the synergistic use of multi-sensor observations for high temporal resolution Sargassum monitoring is lacking. Here, by combining MODIS (on Aqua and Terra), VIIRS (on JPSS1 and SNPP), and OLCI (on Sentinel-3A and -3B) observations, 3-day mean Sargassum distributions were mapped across the Caribbean Sea and Central Atlantic. The Sargassum biomass densities were derived using the sensor-specific Alternative Floating Algae Index (AFAI)-biomass model, and the consistency between the six sensors was examined using MODIS Aqua as the reference sensor. Comparison of the Sargassum biomass derived from different sensors shows that they have strong linear correlations (R2 ≥ 0.95), demonstrating high consistency and continuity between the six-sensor observations. On average, the combined six-sensor datasets provide ∼1.6 times more valid observations compared to the MODIS-only dataset in 2021, enabling the generation of the 0.5° 3-day mean products over ∼90% of the study region. Such 0.5° 3-day mean products detected ∼10-20% more biomass in the bloom peak month (June 2021) compared to the monthly mean counterpart. Increasing the spatial resolution to 0.1°, the 3-day mean products can continuously monitor Sargassum dynamics with eddies and tropical cyclones, which cannot be well captured by single sensors. This study highlights that combining multiple polar-orbiting satellite observations can achieve 3-day gap-free monitoring of floating macroalgae dynamics in the Caribbean Sea and tropical Atlantic, thus facilitating the analyses of the bloom response to different environmental conditions and the prediction of future bloom events.

Fusing remote sensing data with spatiotemporal in situ samples for red tide (Karenia brevis) detection.

We present a novel method for detecting red tide (Karenia brevis) blooms off the west coast of Florida, driven by a neural network classifier that combines remote sensing data with spatiotemporally distributed in situ sample data. The network detects blooms over a 1-km grid, using seven ocean color features from the MODIS-Aqua satellite platform (2002-2021) and in situ sample data collected by the Florida Fish and Wildlife Conservation Commission and its partners. Model performance was demonstrably enhanced by two key innovations: depth normalization of satellite features and encoding of an in situ feature. The satellite features were normalized to adjust for depth-dependent bottom reflection effects in shallow coastal waters. The in situ data were used to engineer a feature that contextualizes recent nearby ground truth of K. brevis concentrations through a K-nearest neighbor spatiotemporal proximity weighting scheme. A rigorous experimental comparison revealed that our model outperforms existing remote detection methods presented in the literature and applied in practice. This classifier has strong potential to be operationalized to support more efficient monitoring and mitigation of future blooms, more accurate communication about their spatial extent and distribution, and a deeper scientific understanding of bloom dynamics, transport, drivers, and impacts in the region. This approach also has the potential to be adapted for the detection of other algal blooms in coastal waters. Integr Environ Assess Manag 2024;20:1432-1446. © 2024 SETAC.

The emergence and dominance of Planktothrix rubescens as an hypolimnetic cyanobacterium in response to re‐oligotrophication of a deep peri‐alpine lake

AbstractToxic cyanobacteria, such as Planktothrix rubescens, came to dominate temperate lakes in the mid‐to‐late 20th century, as a result of eutrophication. Even after decades of re‐oligotrophication, where phosphorus levels were reduced by 1–2 orders of magnitude, P. rubescens remains present in various lakes. In this study, we examine the persistence and changes of P. rubescens deep chlorophyll maximum (DCM) in Lake Hallwil (Switzerland) over 35 yr of steadily decreasing phosphorous concentrations. Although lake transparency increased and the euphotic layer deepened during this period, the P. rubescens population maximum moved even deeper. It is now found ca. 7.7 m deeper than its shallowest position in the 2000s, and this depth no longer coincides with the depth of maximal water column stability. P. rubescens neutral buoyancy has now driven it beneath the stable metalimnion into the hypolimnion, where buoyancy regulation is restricted due to reduced metabolic activity at low light and low temperature. If P. rubescens DCM continues to deepen each year, it will eventually reach a region of lower stability in the hypolimnion where turbulent conditions are strong enough to disperse the DCM. We also explore the mechanisms that ensure P. rubescens ongoing presence in peri‐alpine lakes despite strong re‐oligotrophication and ongoing climate change. We find that P. rubescens in the lake is mainly sustained by growth during fully mixed conditions in winter, not during stratification in summer. This may contradict another commonly made prediction that periods of longer stratification will promote future blooms of this cyanobacterium.

Unusual blooming of invasive ctenophore Beroe ovata (Bruguière, 1789) and geographical range expansion based on morphology and molecular analysis

The neritic ctenophore Beroe ovata (Bruguière, 1789) is a Beroida species frequently found along the western coast of the Atlantic, from northeastern USA to central Argentina. Here we report the geographical range expansion of Beroe ovata and its blooming from the Arabian Sea. In ctenophore the use of molecular tools to support conventional (morphological) identification offers a new perspective in the field of biogeography. The identification of this species is critical for both monitoring future blooms in the area and gaining a better knowledge of the genus diversity on a global scale. The density of the reported blooming was 189 ± 9 ind. m−3. The reported places for this taxon show that it has a subtropical and tropical affinity.

Storm-induced coastward expansion of Margalefidinium polykrikoides bloom in Chesapeake Bay.

An unusual coastward expansion of the toxic dinoflagellate species Margalefidinium polykrikoides was observed in 2020 summer after a tropical storm passing Chesapeake Bay. Such coastward expansion was only recorded in 2007. A newly developed coupled Lagrangian particle tracking and harmful algal bloom model driven by environmental variables was used to investigate the underlying mechanisms and successfully reproduced the expansion patterns. Persistent pre-storm southerly winds favored the delivery of bloom source water originated inside the bay to the coast. Storm-induced strong upwelling of denser subsurface water interacted with the after-storm outflow plume (steered southward as the storm's impacts waned), forming a transport barrier to accumulate algae and delineate the coastwide bloom extent. Algal diel vertical migrations and transport barrier enable algae to stay in the nearshore regions. The storm-induced coastward expansion of M. polykrikoides might increase future bloom possibility in the coastal area.

Co-occurrence patterns and environmental factors associated with rapid onset of Microcystis aeruginosa bloom in a tropical coastal lagoon

The environmental factors contributing to the Microcystis aeruginosa bloom (hereafter referred to as Microcystis bloom) are still debatable as they vary with season and geographic settings. We examined the environmental factors that triggered Microcystis bloom outbreak in India's largest brackish water coastal lagoon, Chilika. The warmer water temperature (25.31–32.48 °C), higher dissolved inorganic nitrogen (DIN) loading (10.15–13.53 μmol L−1), strong P−limitation (N:P ratio 138.47–246.86), higher water transparency (46.62–73.38 cm), and low-salinity (5.45–9.15) exerted a strong positive influence on blooming process. During the bloom outbreak, M. aeruginosa proliferated, replaced diatoms, and constituted 70–88% of the total phytoplankton population. The abundances of M. aeruginosa increased from 0.89 × 104 cells L−1 in September to 1.85 × 104 cells L−1 in November and reduced drastically during bloom collapse (6.22 × 103 cells L−1) by the late November of year 2017. The decrease in M. aeruginosa during bloom collapse was associated with a decline in DIN loading (2.97 μmol L−1) and N:P ratio (73.95). Sentinel-3 OLCI-based satellite monitoring corroborated the field observations showing Cyanophyta Index (CI) > 0.01 in September, indicative of intense bloom and CI < 0.0001 during late November, suggesting bloom collapse. The presence of M. aeruginosa altered the phytoplankton community composition. Furthermore, co-occurrence network indicated that bloom resulted in a less stable community with low diversity, inter-connectedness, and prominence of a negative association between phytoplankton taxa. Variance partitioning analysis revealed that TSM (16.63%), salinity (6.99%), DIN (5.21%), and transparency (5.15%) were the most influential environmental factors controlling the phytoplankton composition. This study provides new insight into the phytoplankton co-occurrences and combination of environmental factors triggering the rapid onset of Microcystis bloom and influencing the phytoplankton composition dynamics of a large coastal lagoon. These findings would be valuable for future bloom forecast modeling and aid in the management of the lagoon.

Metabarcoding of harmful algal bloom species in sediments from four coastal areas of the southeast China.

In the past three decades, harmful algal blooms (HAB) have become more frequent and widespread in southeast Chinese sea areas. Resting stages are regarded as the “seed bank” of algal blooms, and play an important role in initiating HABs. The distribution of resting stages in sediments especially those of HAB species can make good predictions about the potential risk of future blooms, however with limited reports. In this study, surface sediment samples were collected in the four sea areas along the southeast Chinese coasts, including Dafeng Port (DF) in the southern Yellow Sea, Xiangshan Bay (XS), Funing Bay (FN), and Dongshan Bay (DS) in the East China Sea. Diversity and community structure of eukaryotic microalgae in surface sediments were assessed by metabarcoding V4 region of the 18S rDNA, focusing on the distribution of HAB species. Biogenic elements including total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), biogenic silicon (BSi), and moisture content (MC) were analyzed. A total of 454 eukaryotic algal OTUs were detected, which belonged to 31 classes of 9 phyla. Altogether 149 algal species were detected in this study, and 59 taxa have been reported to form resting stages. Eukaryotic algal community was similar in XS, FN and DS of the East China Sea, which were predominated by dinoflagellates. However, algal community was different in DF of the Yellow Sea, and characterized by the dominance of chrysophytes and low OTU richness. The distribution of most abundant HAB species showed positive correlations with TN, BSi, and TOC, suggesting that eutrophication and consequent increase in diatom productivity may have a significant influence on the distribution of HAB species and facilitate the occurrence of HABs. Furthermore, HAB species occurred more abundantly and widely in FN. Our results suggest high potential risks of HABs in the southeast Chinese coast especially in Funing Bay.

Dolichospermum blooms in Lake Superior: DNA-based approach provides insight to the past, present and future of blooms

Cyanobacterial blooms are increasing in frequency, duration, and severity globally in freshwater ecosystems. The Laurentian Great Lakes are prone to toxin-producing cyanobacterial blooms and have experienced annually recurring blooms. Because of its oligotrophic nature, Lake Superior has been relatively free of bloom occurrences. However, in recent years, Dolichospermum blooms have occurred with increasing frequency, especially in the western arm. During a Dolichospermum bloom in 2018, opportunistic samples were collected from the offshore bloom and investigated with shotgun metagenomics. We identified a near-complete Dolichospermum genome that is highly similar to genomes from cultures recovered in Lakes Erie and Ontario. The genomes from the Laurentian Great Lakes are typified by their putative ability to produce a suite of secondary metabolites like anabaenopeptin, but not toxins like microcystin. Additionally, we recovered a Dolichospermum lemmermannii 16S rRNA gene from the bloom and using datasets collected from the epilimnion and sediments in Lake Superior show this organism is ubiquitous and that several strains may exist. While there is much to learn about Lake Superior cyanobacterial bloom development and triggers, understanding this organism is endemic to the region, what its genome is capable of and that specific strains may have provenance within the lake provides a distinct ecological basis for understanding and working towards a predictive framework for future blooms.

Distribution of dinoflagellate cysts in the modern sediments from the coastal aquaculture area and its adjacent oceanic shelf in southeast China

Changes in nutrient loading due to coastal aquaculture and the targeted expansion of monitoring programs over the past few decades have amply demonstrated a marked increase in harmful algal blooms (HABs). In this study, viable dinoflagellate cyst composition and assemblages were investigated by evaluating and classifying their distribution patterns in surface sediments of the Fujian aquaculture coastal region of southeast China. The surface sediment at 5 stations during the spring and summer of 2019 to classify the dinoflagellate cysts present and identified 36 species representing six known and three uncertain taxa groups. The highest cyst was recorded at coastal station P11 in the spring (744.7 cysts g−1 DW), while the lowest cyst was observed at coastal station P5 in spring (50.9 cysts g−1 DW). The number and abundance of the heterotrophic species were greater than the autotrophic species, with the highest species volume belonging to the protoperidinioid group. We also detected potentially harmful algae bloom cysts that hold the potential to form their initial blooms in the sediments. It is important to note that six dinoflagellate cysts were found in the waters along the Fujian coast, as compared to historical data. Although the abundance of these cysts was not high, their presence indicates a potentially grave risk for toxic red tides. More alarmingly, these results suggest that seedbeds may trigger future blooms and outbreaks of toxic species in the present study area.

Dinoflagellate Cyst Distribution in Relation to the Sediment Composition and Grain Size in the Coastal Area of Pangkajene, South Sulawesi, Indonesia

Dinoflagellate cysts have an important role for their bloom dynamics, which are commonly deposited along fine sediment grains and become the source of the next bloom. This study aimed to describe the cyst banks species composition, and their relationship with the sediment particles size and plankton composition in the coast of Pangkajene, South Sulawesi. Cysts observed in this study were extracted from seabed sediments collected from 9 sites. A potential cyst bank, with a cyst density of 240 cysts.g-1 sediment wet weight was found at PK-19, located in proximity to a large harbour complex. Although unusual, cyst density was significantly and positively correlated with the percentage of gravel. In contrast, the diversity of cysts seems to be affected by the percentage of fine sediments, such as silt and clay. None of the sediment composition was found strongly and significantly affecting both cyst density and diversity. A southward increase in cyst density was similar to the trend in the cell density of its planktonic form. Cysts of Protoperidinium spp., Scrippsiella spp., and Pheopolykrikos hartmannii were common and abundant in the sediment. Aside from Protoperidinium spp., most dinoflagellate species found in cyst form were absent from the water column. The occurrence of cysts of harmful dinoflagellates with records of devastating blooms in other coastal areas in Indonesia, such as Margalefidinium polykrikoides, Pyrodinium bahamense, and Gymnodinium catenatum, signifies a need to regularly monitor the area around Pangkajene coast to mitigate impacts of future blooms.

Record‐setting algal bloom in polymictic Lake Balaton (Hungary): A synergistic impact of climate change and (mis)management

Abstract After 25 years of apparently successful eutrophication management, a record‐breaking mixed bloom of Ceratium furcoides and Aphanizomenon flos‐aquae developed unexpectedly in 2019 in the large, polymictic Lake Balaton. The peak concentration of chlorophyll exceeded 300 mg/m3, 1.5 times higher than the pre‐management maxima. The external load was insufficient to provide the phosphorus (P) required to support this bloom, and its taxonomic composition was radically different from blooms in the 1980s. We hypothesised: (1) that unusually long periods of intermittent stratification led to anoxic P release from the sediments, providing the required P; and (2) that the surprising bloom composition indicated a potential regime shift. To test hypothesis 1, we analysed decade‐long high‐frequency data on drivers of lake metabolism recorded at a shallow near‐shore observatory. To explore likely dissolved oxygen (DO) conditions in deep water in 2019, we performed a sensitivity analysis of a one‐dimensional DO model driven by the General Ocean Turbulence Model, the latter being calibrated against high‐frequency hydrometeorological data measured in the open water. Hypothesis 2 was examined by a sequential t‐test analysis applied to multidecadal (1976–2020) data on phytoplankton biomass and composition, nutrient loads and summer mean air temperature. We found that DO depletion (&lt;1 g/m3) was the immediate precursor of the large 2019 bloom. The synergistic impact of a climatic regime shift and multiple coincident management actions provoked a shift in phytoplankton composition in 2013 and forced the ecosystem into the state of internal eutrophication. In the present ecosystem state, similarly large blooms could develop in any summer depending on the sequence of weather events. Within the present, warmer climate regime identified here, the effectiveness of external nutrient control in eutrophication management may be limited by changes in the thermal structure. Therefore, it is vital to supplement external nutrient control with internal nutrient control strategies, such as water level regulation, to manage eutrophication and prevent future blooms. Large, continuous polymictic lakes are susceptible to small changes in water level, because the likelihood of stratification (and thus the likeliness of a eutrophication event) increases steeply and non‐linearly with increasing depth. With a climate that continues to warm, and the associated changes expected in internal lake processes, it is possible that we will see regime shifts (such as that identified in Lake Balaton) across more lakes globally. Managing these conditions will require case‐specific modifications of lake management plans.

Spatio-temporal Mapping of Cotton Blooms Appearance Using Deep Learning

In this paper, we present an approach to create spatio-temporal maps using deep learning to visualize cotton bloom appearance over time. Specifically, we manually annotate cotton flower image data and train three state-of-the-art fast deep neural network models to count cotton blooms and their frequency over time prior to harvesting. We use the detection results of the best performing model combined with traditional pixel-based image analysis methods to create a map of where past and future blooms grow on a mid-stage cotton plant. The training results of our best model show a visual understanding of how many cotton flowers grow with high F1 Score of more than 0.95, a true positive rate of 98%, false negative and false positive rates both under 10%, and millisecond-scale inference time for real-time processing.

Update on incidences of cyanobacteria (blue-green algae) in Scottish freshwaters

An update on incidences of cyanobacteria (blue-green algae) in Scottish freshwaters is provided, highlighting the number of incidences and common cyanobacteria taxa recorded, and outlining potential effects of climate change on future bloom events.

Atmospheric Stilling Promotes Summer Algal Growth in Eutrophic Shallow Lakes.

Algal blooms are environmental challenges confronting lakes worldwide and are significantly influenced by chlorophyll a yields per unit phosphorus (Chla/TP), or nitrogen (Chla/TN). Here, the influence of inter-annual hydrometeorological variations on Chla/TP and Chla/TN were evaluated in eutrophic shallow Lake Taihu, China. Our results demonstrated significant increases (p < 0.001) in both Chla/TN and Chla/TP from 2005 to 2017, and increased Chla yields during the winter months were mainly correlated with higher water temperature and longer sunshine hours, which may cause severer blooms in winter and spring. In remaining months from 2005 to 2017, typical associations between atmospheric stilling (or water level elevation) and higher Chla yields were observed. The results also indicate that atmospheric stilling and water level elevation significantly (p < 0.001) decreased background turbidity and promoted buoyant cyanobacterial biomass, alleviating phytoplankton light limitation. Given the subtropical location, eutrophic status, and high background turbidity of Lake Taihu, light may be the critical limiting factor for summer phytoplankton growth; thus, improved light availability would promote Chla yields until self-shading caused further light limitations. If the mechanism is general, promoting the effect of atmospheric stilling on annual peak Chla in shallow lakes may be greatly underestimated, and our finding will affect future bloom mitigation efforts in such systems.

Polyketide synthase genes and molecular trade-offs in the ichthyotoxic species Prymnesium parvum

Prymnesium parvum is a bloom forming haptophyte that has been responsible for numerous fish kill events across the world. The toxicity of P. parvum has been attributed to the production of large polyketide compounds, collectively called prymnesins, which based on their structure can be divided into A-, B- and C-type. The polyketide chemical nature of prymnesins indicates the potential involvement of polyketide synthases (PKSs) in their biosynthesis. However, little is known about the presence of PKSs in P. parvum as well as the potential molecular trade-offs of toxin biosynthesis. In the current study, we generated and analyzed the transcriptomes of nine P. parvum strains that produce different toxin types and have various cellular toxin contents. Numerous type I PKSs, ranging from 37 to 109, were found among the strains. Larger modular type I PKSs were mainly retrieved from strains with high cellular toxin levels and eight consensus transcripts were present in all nine strains. Gene expression variance analysis revealed potential molecular trade-offs associated with cellular toxin quantity, showing that basic metabolic processes seem to correlate negatively with cellular toxin content. These findings point towards the presence of metabolic costs for maintaining high cellular toxin quantity. The detailed analysis of PKSs in P. parvum is the first step towards better understanding the molecular basis of the biosynthesis of prymnesins and contributes to the development of molecular tools for efficient monitoring of future blooms.

Cyanobacterial Akinete Distribution, Viability, and Cyanotoxin Records in Sediment Archives From the Northern Baltic Sea

Cyanobacteria of the order Nostocales, including Baltic Sea bloom-forming taxa Nodularia spumigena, Aphanizomenon flosaquae, and Dolichospermum spp., produce resting stages, known as akinetes, under unfavorable conditions. These akinetes can persist in the sediment and germinate if favorable conditions return, simultaneously representing past blooms and possibly contributing to future bloom formation. The present study characterized cyanobacterial akinete survival, germination, and potential cyanotoxin production in brackish water sediment archives from coastal and open Gulf of Finland in order to understand recent bloom expansion, akinete persistence, and cyanobacteria life cycles in the northern Baltic Sea. Results showed that cyanobacterial akinetes can persist in and germinate from Northern Baltic Sea sediment up to >40 and >400 years old, at coastal and open-sea locations, respectively. Akinete abundance and viability decreased with age and depth of vertical sediment layers. The detection of potential microcystin and nodularin production from akinetes was minimal and restricted to the surface sediment layers. Phylogenetic analysis of culturable cyanobacteria from the coastal sediment core indicated that most strains likely belonged to the benthic genus Anabaena. Potentially planktonic species of Dolichospermum could only be revived from the near-surface layers of the sediment, corresponding to an estimated age of 1–3 years. Results of germination experiments supported the notion that akinetes do not play an equally significant role in the life cycles of all bloom-forming cyanobacteria in the Baltic Sea. Overall, there was minimal congruence between akinete abundance, cyanotoxin concentration, and the presence of cyanotoxin biosynthetic genes in either sediment core. Further research is recommended to accurately detect and quantify akinetes and cyanotoxin genes from brackish water sediment samples in order to further describe species-specific benthic archives of cyanobacteria.

Report of Mauve Stinger Pelagia cf. noctiluca (Cnidaria: Scyphozoa) Bloom from Northeastern Arabian Sea (NEAS)

The jellyfish, Pelagia noctiluca is considered as one of the notorious bloom forming species in the world’s oceans due to its wide distribution, high abundance, ecological role, and also because of its negative interaction with humans. In the present study, we report the bloom of Pelagia cf. noctiluca from northeastern Arabian Sea in December 2018, identifying specimens with the use of molecular and morphological approaches. The identification of this species is important for monitoring future blooms in the area and for understanding the diversity of the genus in a global scale. Genetic data considered sequences of COI and 16S, and our sample clustered with data identified as Pelagia noctiluca and P. panopyra. Based on the analysis the closest species with confirmed records is P. noctiluca from the Mediterranean Sea. However, we prefer to be conservative and keep some level of uncertainty in species identification as Pelagia cf. noctiluca until further populational studies can embrace the whole diversity of the genus and distributions. The density of the reported bloom was 7550 ± 576 ind. m−3.