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The analysis of the mesozooplankton community from the Romanian Black Sea waters revealed variations both from quantitative and qualitative point of view. A decrease in the number of identified taxa according to the season was observed, with a maximum of 25 taxa in the warm season and a minimum of 15 taxa in the cold season. The nonfodder component represented by Noctiluca scintillans recorded the highest density and biomass values in the warm season, in the cold season being less represented, fact highlighted by Simper analysis. The mesozooplanktonic fodder component showed variations of density and biomass, copepods and the meroplanktonic component representing the bulk of the community in the warm season. In the warm season, the group of Cladocera's recorded high density and biomass values, unlike in the cold season where they were very poorly represented. Other groups were better represented also in the warm season, showing a decrease in terms of abundance and biomass in the cold season. [ABSTRACT FROM AUTHOR]

This article attempts to trace a deeper history of a 'dead zone'--the term for areas of the ocean with lower than normal amounts of dissolved oxygen--in the Gulf of Oman. Due to the paucity of oceanographic data before the late twentieth century, this article reviews a range of British imperial travelogues and fisheries records with an eye to knowledge gleaned from contemporary scientific knowledge of the phenomenon. Although imperial sources do not discuss the issue directly (the science of dead zones was not articulated until the mid-twentieth century), they serve as sources of valuable indirect data pointing to the presence of accompanying phenomena of low-oxygen waters--large-scale blooms of the bioluminescent plankton Noctiluca scintillans and fluctuations in fish stocks--long before the 'discovery' of 'the world's largest dead zone' in 2018. This approach yields a deeper view of the sea's changes through time instead of accepting the sensationalist immediacy of contemporary journalistic accounts, and impels us to take seriously the wisdom of local fishers as a counterweight to scientific knowledge. In doing so, it hopes to advance a scholarly conversation about mixed methods in environmental history and Indian Ocean studies, and about the paradoxes and contradictions of life in the 'Anthropocene'. [ABSTRACT FROM AUTHOR]

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Green Noctiluca scintillans (Noctiluca) is an unusually large mixotrophic dinoflagellate that forms widespread blooms in tropical coastal marine ecosystems. Its recent emergence as the dominant winter-monsoon bloom-forming organism in the Arabian Sea has been attributed to the unique ability of its endosymbionts, Protoeuglena noctilucae, present within its symbiosome to photosynthesize more efficiently under suboxic conditions. What also distinguishes green Noctiluca from most mixotrophs and other bloom-forming organisms is its ability to persist and thrive as large blooms, even under the most unfavorable nutrient conditions. In this study, we report the results of 1) nitrogenous nutrient enrichment experiments undertaken with a laboratory strain of green Noctiluca isolated from the Arabian Sea, and 2) nitrogenous nutrient uptake experiments undertaken with natural populations of green Noctiluca sampled off the coast of Oman. Both investigations revealed that this organism has a greater preference for regenerated nitrogenous nutrients, i.e., urea and ammonium (NH4), as compared to new nitrogen, nitrate (NO3). What was particularly surprising about this mixotroph, however, was its ability to grow and survive for extended periods, even in the absence of nitrogenous nutrients. In the field, green Noctiluca bloom outbreaks were invariably preceded by extremely high concentrations of urea and NH4. We also observed that irrespective of the nitrogenous nutrients available to them, green Noctiluca cells always accumulated large amounts of NH4 within their symbiosome, which resulted in sharp increases in seawater NH4 concentrations (30 to 200 μM) following their demise. [ABSTRACT FROM AUTHOR]

Using data collected by the Hyperspectral Imager for the Coastal Ocean (HICO) on the International Space Station between 2010 – 2014, hyperspectral reflectance of various floating matters in global oceans and lakes are derived for the spectral range of 400 – 800 nm. Specifically, the entire HICO archive of 9,411 scenes is first visually inspected to identify suspicious image slicks. Then, a nearest-neighboring atmospheric correction is used to derive surface reflectance of slick pixels. Finally, a spectral unmixing scheme is used to derive the reflectance spectra of floating matters. Analysis of the spectral shapes of these various floating matters (macroalgae, microalgae, organic particles, whitecaps) through the use of a Spectral Angle Mapper (SAM) index indicates that they can mostly be distinguished from each other without the need of ancillary information. Such reflectance spectra from the consistent 90-m resolution HICO observations are expected to provide spectral endmembers to differentiate and quantify the various floating matters from existing multi-band satellite sensors and future hyperspectral satellite missions such as NASA's Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) mission and Surface Biology and Geology (SBG) mission. [ABSTRACT FROM AUTHOR]

Climate driven changes and anthropogenic pressures on the marine environment have been shown to favor the increase in certain potentially harmful species. Among them, Noctiluca scintillans, a common dinoflagellate, often blooms during warm summers and is known to affect plankton communities. In this study, we assessed the dynamics in abundance and cell size of N. scintillans as well as the relationship between N. scintillans and small soft-bodied zooplankton in the Belgian part of the North Sea (BPNS), since negative correlations between these plankton groups have been previously reported for nearby regions. This study is the first to present consistently counted N. scintillans cell numbers and measured cell lengths, through the analysis of ZooScan images from samples taken monthly at stations throughout the coastal zone of the BPNS. The results show that N. scintillans demonstrated clear seasonal dynamics with both high densities and large cell sizes in spring/summer (May-July). The occurrence of N. scintillans in the analyzed plankton samples and the abundance of N. scintillans at the observed peak intensities nearly tripled over a period of 5 years. A zero-inflated model showed a correlation of N. scintillans abundance with temperature as well as with phosphate concentrations, suggesting that anthropogenic influences such as climate change and riverine nutrient inputs could affect the temporal dynamics of the species. The results, on the other hand, did not show any negative impact of N. scintillans on the soft-bodied plankton community.

Gradual decadal changes have taken place in the Western Arabian Sea over the last 50 years. These changes have affected wind speeds, atmospheric and sea surface temperature, thermohaline stratification, shoaling of the oxycline, and dust/iron inputs. A decrease in nitrate supply of the photic layer have caused an increase in annual frequency of harmful algal blooms and fish kills. Along with that, a decrease in diatom biomass and a shift from red Noctiluca to green Noctiluca during the northeast monsoon was observed during the last two decades, Even though these are the same species they have very different nutritional modes. The red one is a heterotroph with a preference for grazing diatoms, while the green one has a symbiont and thus it is a mixotroph. Recent results suggest that this shift may be caused by the shoaling oxycline since the green one grows better under low oxygen because the symbiont produces oxygen for its host. The western Arabian Sea is temporally and spatially complex. With the recent advances in remote sensing of the ocean, a further understanding of these temporal and spatial changes can be gained through analyzing frequent images with opportunistic ground-truthing.

The paper aims to develop and test a semi-quantitative method that generates scenarios for the zooplankton community development under salinity and nutrients fluctuations. First, we identified the relationships between the mesozooplankton component and the environmental factors by analyzing data (N=2566) collected within the warm season (May-September) of a decade (2008-2018). The biotic and abiotic parameters were investigated at 37 stations within the monitoring network of the Romanian Black Sea waters, covering all three marine reporting units (waters with variable salinity, coastal and marine) according to Marine Strategy Framework Directive (MSFD). We identified 32 mesozooplankton species belonging to ten taxonomic classes, copepods representing the bulk of the community. In waters with variable salinity and coastal waters, the fodder component of the mesozooplanktonic community was dominant, while in marine waters the nonfodder component was better and exclusively represented by Noctiluca scintillans. Physicochemical parameters that showed significant correlations with the mesozooplankton species were S (salinity) and nutrients - NO2- (nitrite), NO3-(nitrate), PO43-(phosphate) and NH4+(ammonium). The number of species significantly correlated with the physicochemical parameters showed variations generally correlated with the increasing salinity gradient: in waters with variable salinity nine species being correlated, in coastal waters ten species, and in marine waters five species. [ABSTRACT FROM AUTHOR]

The annual episodes of high-biomass algal bloom are a known phenomenon in the northern Arabian Sea. In the present study, we demonstrate growth and decay of bloom using long-term satellite-retrieved parameters such as chlorophyll-a (chl-a), sea surface temperature (SST), phytoplankton absorption (aph), detritus–coloured dissolved organic matter absorption (adg) and model-derived mixed layer depth (MLD). Chl-a, the index of phytoplankton biomass, showed an inverse relationship with SST with a lag of 2–8 days between lowest SST and highest chl-a. The deepening of MLD associated with high chl-a and low SST indicated a role of convective mixing in the formation of bloom. The average SST of ~ 25 °C was found to be a favourable condition for such open ocean bloom. The lag was more towards eastern boundary of the basin, indicating variable intensities of convective mixing influencing spatial extent of bloom. The positive correlation between aph and adg indicated simultaneous production and degradation showing delay of 3–10 days from peak production to degradation. [ABSTRACT FROM AUTHOR]

Seasonal dynamics of microzooplankton and changes in environmental condition were analysed during a one-year field sampling campaign in the Sea of Oman at two different stations. Monsoon winds in this region cause distinct seasonality patterns with high primary productivity during the south-west monsoon in summer (June to October) and north-east monsoon periods in winter (November to March). Microzooplankton in the Sea of Oman showed several biomass peaks throughout the year. In general, higher biomass occurred during the south-west monsoon when compared to the north-east monsoon period with maxima of 190 µg C l−1at the inshore station Bandar Al-Khyran at 1m and 308 µg C l−1 at 10m water depth. At the offshore-station, peaks of 372 µg C l−1 (1m) and 256 µg C l−1 (20m) occurred during the south-west monsoon. A strong coupling between phytoplankton and microzooplankton was observed during monsoon periods but some microzooplankton peaked during inter-monsoon periods when chlorophyll concentration was low (Bandar Al-Khyran: 372 µg C l−1 at 1m and 196 µg C l−1, 10m; Offshore-station: 419 µg C l−1, 20 m). The initiation of phytoplankton blooms in the Sea of Oman was bottom-up controlled due to strong seasonal nutrient influx during south-west and north-east monsoon periods. Highest microzooplankton biomass occurred during monsoon periods with a dominance of Noctiluciphyceae and peaks of 7596 µg C l−1 at Bandar Al-Khyran (1m) and 5942 µg C l−1 (10m). Copepod nauplii, Amoebozoa and Larvacea contributed substantially to microzooplankton biomass throughout the year. Ciliophora contributed low proportion to the total microzooplankton biomass peaking both during monsoon and inter-monsoon periods. During the spring inter-monsoon, choreotrich ciliates (tintinnids) showed distinct peaks of 15.9 µg C l−1 at Bandar Al-Khyran (1m) and 17.7 µg C l−1 (10m) as well as 18.2 µg C l−1 at Offshore-station (20m). The interplay between bottom-up controlled primary production and top-down control mechanisms regulates the phenology patterns of specific microzooplankton groups in the Sea of Oman thus pointing at complex trophodynamic interactions at the lowermost foodweb level in this low-latitude ecosystem. [ABSTRACT FROM AUTHOR]

Abstract Weekly field observations were conducted in Harima-Nada in the eastern part of the Seto Inland Sea, Japan from 21 August to 26 October 2015 to investigate the role of heterotrophic dinoflagellate Noctiluca scintillans on a coastal ecosystem. We observed a rapid N. scintillans growth just after increasing Chl. a , of which the dominant species were Chaetoceros spp., Thalassionema spp., Thalassiothrix spp., Coscinodiscus spp., Thalassiosira spp., and Stephanopyxis spp. We also observed under a microscope that N. scintillans cells grazed on these species of diatoms. The biomass of N. scintillans was estimated to increase from 4.50 to 470 mgC m−2 in 7 days. On the other hand, phytoplankton biomass drastically decreased from 2110 to 725 mgC m−2. The increase in N. scintillans biomass could account for 33.6% of the decrease in phytoplankton biomass. If we assume all the decrease in phytoplankton biomass was due to the N. scintillans grazing of diatoms, the 33.6% indicates the apparent gross growth efficiency of N. scintillans under a sufficient source of feed. Our results indicated the active feeding of N. scintillans on diatoms ends a diatom bloom in coastal water. Highlights • The rapid increase of Red Noctiluca scintillans just after the diatom bloom was observed at the coastal water in Japan. • Some diatom species which constituted the diatom bloom was observed in the food vacuoles of N. scintillans. • The apparent gross growth efficiency was calculated from the changes of N. scintillans and the phytoplankton biomass. • The apparent gross growth efficiency estimated in this study was almost the same level as that of zooplankton. • Our results indicated that N. scintillans ends the diatom bloom in the coastal water. [ABSTRACT FROM AUTHOR]

Abstract The northeastern Arabian Sea (NEAS) experiences convective mixing during winter, but this mixing does not reach up to the silicicline, resulting in the limited supply of silicate (Si) compared to nitrate (N) and phosphate (P) to the mixed layer (ML) and formation of non-diatom blooms. The poleward advection of waters of low surface salinity by the West India Coastal Current (WICC) to the NEAS weakens the vertical mixing and reduces the Si input to the mixed layer, resulting in occurrence of Noctiluca scintillans blooms. The saturation of dissolved oxygen in the NEAS varied between 88 and 98%, suggesting N. scintillans blooms occur in oxic conditions. Enhanced cell abundance of N. scintillans was observed in the bloom region in the upper 10 m. Phytoplankton pigments data revealed higher contribution of Chlorophytes, Prasinophytes, Prymnesiophytes and Prochlorophytes in the bloom than non-bloom region. The isotopic composition of nitrogen and carbon of particulate organic matter indicated that natural and in situ processes contributed to both nutrients and organic carbon pool in the NEAS in supporting the massive occurrence of N. scintillans blooms than hitherto hypothesized to anthropogenic sources. This study further suggests that the effect of anthropogenic pollutants released into the NEAS from the mega-cities is limited to the neighbourhood of these cities and does not affect the open ocean. Highlights • Massive Noctiluca scintillans blooms occur through natural, in situ processes under oxic conditions. • Noctiluca scintillans blooms are associated with weak vertical mixing and low silicate supply than nitrate and phosphate. • Noctiluca scintillans blooms are not caused by pollutants released from the bordering countries. [ABSTRACT FROM AUTHOR]

Intense blooms of the heterotrophic dinoflagellate, green Noctiluca scintillans, have been reported annually in the Northern Arabian Sea since the early 2000s. Although not known to produce organic toxins, these blooms are still categorized as a harmful due to their association with massive fish mortalities. Recent work has attributed these blooms to the vertical expansion of the oxygen minimum zone, driven by cultural eutrophication from major coastal cities in western India. As diatoms are preferred prey of green Noctiluca scintillans, more frequent blooms of this mixotroph will likely impact the productivity of important fisheries in the region. The present study uses a satellite algorithm to determine the distribution of both diatom and green Noctiluca blooms in the Northeastern Arabian Sea from 2009 to 2016. The results from shipboard microscopy of phytoplankton community composition were used to validate the satellite estimates. The satellite algorithm showed 76% accuracy for detection of green Noctiluca and 92% for diatoms. Shipboard measurements and data from biogeochemical-Argo floats were used to assess the relationship between oxygen concentrations and green Noctiluca blooms in the Northeastern Arabian Sea. Regardless of the presence of a Noctiluca bloom, the dissolved oxygen in the photic zone was always >70% saturated, with an average oxygen saturation >90%. The variability in the relative abundance of diatoms and green Noctiluca is not correlated with changes in oxygen concentration. These findings provide no evidence that cultural eutrophication has contributed to the decadal scale shifts in plankton composition in the Northeastern Arabian Sea oceanic waters. Conversely, the climatic warming of surface waters would have intensified stratification, thereby reducing net nutrient flux to the photic zone and decreasing silicate to nitrate ratios (Si:N); both factors that could increase the competitive advantage of the mixotroph, green Noctiluca , over diatoms. If so, the decadal-scale trajectory of phytoplankton community composition in the Northeastern Arabian Sea may be a harbinger of future climate-driven change in other productive oceanic systems. [ABSTRACT FROM AUTHOR]

A comprehensive analysis on the phytoplankton ecology with special reference to different phytoplankton size classes was carried out at green Noctiluca scintillans (hereafter Noctiluca ) bloom and non-bloom locations in offshore waters of the northern Arabian Sea. At the bloom locations, green Noctiluca represented a dense mono-specific proliferation with average cell density of 10.16 ± 5.806 × 10 4  cells-L −1 and relative abundance share of 98.63%. Active photosynthesis through prasinophytic endosymbiont was depicted from net community production magnitude reaching 85.26 mgC/m 3 /Day under low prey abundance. Parallel swarming of Porpita porpita , a voracious copepod feeder signified the competitive advantage of Noctiluca to have the phytoplankton prey. Average concentration of picophytoplankton biomass was eleven times lower in surface waters of non-bloom stations in comparison to bloom. Higher N:P ratio in subsurface waters of non-bloom stations signified non-utilization of nitrogenous nutrients. Green Noctiluca bloom onset subsequent to diatom rich conditions was evident from spatio-temporal ocean colour satellite imageries. [ABSTRACT FROM AUTHOR]

Abstract: Friction generally happening among all moving material interfaces wastes nearly one‐third of total mechanical energy in the world each year, although different kinds of lubricants are adopted. Particle additives, like diamond, inorganic fullerene, and graphene, can enter tribological contacts to reduce friction and protect surfaces from wear. However, the growth of such additives with spherical morphology and high dispersibility in oil without molecular ligands is a major problem. Inspired by the impressive dispersion stability of Noctiluca scientillans in ocean, one novel core–shell composite constructed with superhard SiC sub‐microsphere as core and exclusive floating flat‐blade graphene sheet as shell (SiC@G) is designed. These core–shell SiC@G sub‐micropheres are synthesized for the first time by in situ pulsed laser irradiating commercial SiC powders in liquid at ambient conditions. Both laser‐stimulated surface tension energy release and photothermal decomposition involved in the laser irradiation process assure the reshaping of SiC particles and the formation of graphene sheets derived from SiC surface. Due to the synergistic effect of SiC spheres changing effectively sliding friction into rolling friction and flexible self‐lubricating graphene forming a tribofilm easily, such composites as additives remain well dispersed in lubricating oil and exhibit enhanced antiwear and friction‐reduction performance. [ABSTRACT FROM AUTHOR]

Bioluminescent seas caused by blooms of the dinoflagellate Noctiluca scintillans are a famous scenic attraction in the Matsu archipelago near the Chinese coast in the northern part of the Taiwan Strait. The relationship between the abundance of N. scintillans and various environmental factors was examined in the subtropical coastal waters of these islands from April to December, 2016. N. scintillans disappeared after June 20th, when the sea water temperature exceeded 27 °C. A strong inverse correlation between N. scintillans and diatoms in PCA analysis indicated that diatoms suffer high grazing pressure from N. scintillans . N. scintillans appeared most abundantly during the flood season, when diatoms are most abundant. Strong inverse correlations between N. scintillans and the wind speed and wind direction in PCA further point to the effect of wind on the accumulation of cells. [ABSTRACT FROM AUTHOR]

Gradual decadal changes have taken place in the Western Arabian Sea over the last 50 years. Here we syntheses available evidences and reveal the trends pronounced in directly measured and remotely sensed parameters. We show that decadal changes have affected wind speeds, atmospheric and sea surface temperature, thermohaline stratification, shoaling of the oxycline, and dust/iron inputs. A decrease in nitrate supply of the photic layer have caused an increase in annual frequency of harmful algal blooms and fish kills. Along with that, a decrease in diatom biomass and a shift from red Noctiluca to green Noctiluca during the northeast monsoon was observed during the last two decades, Even though these are the same species they have very different nutritional modes. The red one is a heterotroph with a preference for grazing diatoms, while the green one has a symbiont and thus it is a mixotroph. Recent results suggest that this shift may be caused by the shoaling oxycline since the green Noctiluca grows better under low oxygen because the symbiont produces oxygen for its host. The western Arabian Sea is temporally and spatially complex. With the recent advances in remote sensing of the ocean, a further understanding of the mesoscale spatial-temporal variability of Noctiluca blooms can be gained through analyzing frequent images with opportunistic ground-truthing. [ABSTRACT FROM AUTHOR]

In 2015, a Noctiluca scintillans bloom and associated water column properties were studied in the northern Arabian Sea. Our observations showed photic depth limited to 30 m with uniform oxygen concentration of ~223 μM. In general, the dissolved oxygen ranged between 180 and 223 μM within the top 80 m indicating saturated mixed layer. Chlorophyll a varied between 0.24 and 2.4 mg m-3 within the core of the bloom and <0.1 mg m-3 outside. We further examined Argo oxygen data from 2006 to 2013 to delineate possible surface water hypoxia associated with the initiation of N. scintillans bloom. Oxygen profiles from Argo data suggest oxic upper water column (~ 50 m) with strong seasonal shoaling. Our results do not indicate any mixed layer oxygen depletion associated with the N. scintillans bloom or any evidence of surface water hypoxia in the past. However, examination of silicate/nitrate (Si/N) climatology suggests strong longitudinal variation. The silicate in the surface waters in the northwestern Arabian Sea is depleted much earlier (Si/N < 1) compared with the eastern part, resulting in a strong spatial trend. This presumably facilitates easy community transition to a N. scintillans bloom. This is supported by the heterotrophic nature of the species which, under detectable and belowdetectable nitrate conditions, gives it a competitive advantage over other phytoplankton communities. [ABSTRACT FROM AUTHOR]

A regionally tuned three component “abundance” model of Brewin et al. (2012) has been used to discriminate satellite ocean color derived fields of phytoplankton biomass observable as Chlorophyll-a (Chl-a), into three size classes, i.e. microplankton (> 20 μm), nanoplankton (> 2 to < 20 μm) and picoplankton (< 2 μm). The model has been applied to MODIS-Aqua and Oceansat-2, Ocean Color Monitor (OCM) derived fields of Chl-a data between Nov. and Mar. In the Arabian Sea, during the evolution of blooms of the large (> 800 μm sized) green mixotrophic dinoflagellate Noctiluca scintillans . A comparison of shipboard measured and model derived values of phytoplankton size classes (PSCs) show the superiority of the regionally tuned model over parameterizations used in the original model of Brewin et al. (2012). A total number of 39 in situ data points have been used for the tuning of the regional model and 5 different in-situ data points have been used for the comparison with in situ data in this remote region of data paucity. The absolute mean and the maximum absolute errors for all size fractions are 4.7% and 17.2% respectively, as compared to the values of 9.6% and 26% respectively obtained using Brewin et al. (2012).When applied to a weekly time series of Chl-a images, the regionally tuned model is able to capture the seasonal cycle of PSC in the Arabian Sea associated with the tail end of the fall inter-monsoon (Nov.), the winter monsoon (Dec. to Feb.) and the transition to the spring inter-monsoon Although ocean color remote sensing is a useful tool for studying phytoplankton processes in regions like the Arabian Sea that suffer from a paucity of in-situ observations, enhancing the validity and confidence in satellite ocean color derived products such as PSC, will require additional shipboard datasets. [ABSTRACT FROM AUTHOR]

An ecosystem disruptive bloom of red Noctiluca scintillans (hereafter Noctiluca) was observed in coastal waters of the north-western Bay of Bengal during April 2014. Based on the principle of phytoplankton group/species specific remote sensing reflectance (R), a technique of detecting green Noctiluca and diatom was developed earlier using R at 443, 488, and 531 nm of Moderate Imaging Spectroradiometer-Aqua (MODIS). This was appropriately modified to detect bloom of red Noctiluca in coastal waters of the Bay of Bengal. Additional R data at longer wavelengths viz. 667 and 678 nm were included in the existing algorithm, and the spectral shapes were accounted to detect the bloom of red Noctiluca. The classification scheme discriminates red Noctiluca from the green form of the same species and diatom. Phytoplankton group/species products were generated using the modified approach and validated with the reported events of red and green Noctiluca blooms in the Indian coastal waters. The present study also highlights two specific results based on MODIS retrieved time-series phytoplankton group/species image analysis: first, the observation of coexistence of diatom, red, and green Noctiluca in coastal waters of the north-western Bay of Bengal, and the second, phytoplankton community shift resulting in red/green Noctiluca proliferation following diatom. [ABSTRACT FROM AUTHOR]

The relative grazing impact of Noctiluca scintillans (hereafter referred only Noctiluca) and copepods ( Acrocalanus gracilis, Paracalanus parvus, Acartia danae and Oithona similis) on the phytoplankton community in an upwelling-mudbank environment along the southwest coast India is presented here. This study was carried out during the Pre-Southwest Monsoon (April-May) to the Late Southwest Monsoon (August) period in 2014. During the sampling period, large hydrographical transformation was evident in the study area (off Alappuzha, Southwest coast of India); warmer Pre-Southwest Monsoon water column condition got transformed into cooler and nitrate-rich hypoxic waters during the Southwest Monsoon (June-August) due to intense coastal upwelling. Copepods were present in the study area throughout the sampling period with a noticeable increase in their abundance during the Southwest Monsoon. On the other hand, the first appearance of Noctiluca in the sampling location was during the Early Southwest Monsoon (mid-June) and thereafter their abundance increased towards the Peak Southwest Monsoon. The grazing experiments carried out as per the food removal method showed noticeable differences in the feeding preferences of Noctiluca and copepods, especially on the different size fractions of phytoplankton. Noctiluca showed the highest positive electivity for the phytoplankton micro-fraction (av. 0.49 ± 0.04), followed by nano-fraction (av. 0.17 ± 0.04) and a negative electivity for the pico-fraction (av. −0.66 ± 0.06). In total ingestion of Noctiluca, micro-fraction contribution (83.7%) was significantly higher compared to the nano- (15.7%) and pico-fractions (0.58%). On the other hand, copepods showed the highest positive electivity for the phytoplankton nano-fraction (av. 0.38 ± 0.04) followed by micro- (av. -0.17 ± 0.05) and pico-fractions (av. −0.35 ± 0.05). Similarly, in total ingestion of copepods, nano-fraction (69.7%) was the highest followed by micro- (28.9%) and pico-fractions (1.37%). The grazing pressure of Noctiluca on the total phytoplankton was found to be 27.7% of the standing stock and 45.6% of the production, whereas in the case of copepods, it was 9.95% of the standing stock and 16.6% of the production. The study showed that the grazing pressure of Noctiluca on the total phytoplankton as well as larger phytoplankton fraction was 2.8- and 8-folds higher than that of the copepods. This suggests the leading role of Noctiluca as an effective grazer of larger phytoplankton along the southwest west coast of India, especially during the Peak/Late Southwest Monsoon. [ABSTRACT FROM AUTHOR]

The dinoflagellate Noctiluca scintillan s ( Noctiluca ) has the ability to reproduce sexually, which may help to increase or restore its population size during periods of blooms or environmental stress. Here, we documented for the first time a marine ciliate Strombidium sp. that feeds on Noctiluca ’s progametes undergoing stages 5 to 9 of nuclear division. This ciliate frequently swam on or around gametogenic and some vegetative Noctiluca cells. The ciliates associated with gametogenic cells had significantly lower swimming speed and changed direction more frequently than those associated with vegetative cells, which overall increased their time spent around the food patches (progametes). This trophic interaction constitutes an upside-down predator-prey link, in which ciliates within the typical size range of Noctiluca prey, become the predators. Based on the phylogenetic tree (maximum-likelihood), there are 14 environmental clones similar to Strombidium sp. found in other coastal waters, where Noctiluca presence or blooms have been reported. This novel predator-prey relationship could therefore be common in other Noctiluca habitats. Additional studies are needed to assess the magnitude of its impacts on Noctiluca population dynamics and plankton bloom succession. [ABSTRACT FROM AUTHOR]

Noctiluca scintillans is a globally distributed dinoflagellate that often forms a “Red Tide” bloom, but its geographically genetic differentiation is not well understood. In this study, three loci of the rRNA cistron were analyzed for populations from China and a population from Port Aransas, Texas, USA. Both phylogenetic and haplotypes network analyses based on ITS, SSU and LSU DNA markers revealed low genetic variation within and between populations along the Chinese coast, but substantial divergence based on ITS marker between the Chinese populations and the American population. Twelve single-cells were examined for intra-cell genetic variation and high levels of polymorphism were detected. The large genetic distance among the intra-cell ITS sequences (0–0.043) can exceed the species boundary (0.02 or 0.04) previously reported for dinoflagellates. High genetic diversity of intra-genomic, with the mean genetic distance being 5.1 folds greater than mean inter-genomic distance in the China Sea region, suggests high levels of gene flow and high frequency of recombination, while the divergence between the Chinese and the American populations indicates limited gene flow between the two continents. The present study suggests that the red N. scintillans is globally ubiquitous but genetically showing inter-region differentiation. [ABSTRACT FROM AUTHOR]

In the last decade, field studies in the northern Arabian Sea showed a drastic shift from diatom-dominated phytoplankton blooms to thick and widespread blooms of the green dinoflagellate, Noctiluca scintillans . Unlike the exclusively heterotrophic red form, which occurs widely in tropical to temperate coastal waters, the green Noctiluca contains a large number of endosymbiotic algal cells that can perform photosynthesis. These symbiotic microalgae were first described under the genus Protoeuglena Subrahmanyan and further transferred to Pedinomonas as P. noctilucae Sweeney. In this study, we used the 18S rDNA, rbc L and chloroplast 16S rDNA as gene markers, in combination with the previously reported morphological features, to re-examine the phylogenetic position of this endosymbiotic algal species. Phylogenetic trees inferred from these genes consistently indicated that P. noctilucae is distantly related to the type species of Pedinomonas. The sequences formed a monophyletic clade sister to the clade of Marsupiomonas necessitating the placement of the algal symbionts as an independent genus within the family Marsupiomonadaceae. Based on the phylogenetic affiliation and ecological characteristics of this alga as well as the priority rule of nomenclature, we reinstate the genus Protoeuglena and reclassify the endosymbiont as Protoeuglena noctilucae . [ABSTRACT FROM AUTHOR]

The potential for transport of non-indigenous marine microalgae via ship's ballast water has been amply demonstrated, and nearly all known harmful algal bloom species have been documented in viable form from ship's ballast water. Ballast water uptake needs to be strongly discouraged during harmful algal bloom events. Efficacy of ballast water exchange in removing harmful microalgal cells is limited, since this nearly always leaves behind a viable inoculum. The precise location of ballast water exchange needs to be carefully chosen, and retention of dinoflagellate cysts and diatom spores in ballast tank sediments is of special concern. The only fully effective ballast water treatment for microalgae is the application of biocides, but heat treatment also offers considerable promise especially in subtropical and tropical waters. To manage harmful algal blooms, other key environmental drivers such as eutrophication and climate change also need to be addressed. Effective monitoring for harmful algal species and their toxins remains the critical tool to protect human health, fisheries, aquaculture and desalination industries. Challenges and opportunities for ballast water management in the Arabian Gulf region are discussed. [ABSTRACT FROM PUBLISHER]

Oceanic waters of the Northern Arabian Sea experience massive algal blooms during winter-spring (mid Feb-end Mar), which prevail for at least for 3 months covering the entire northern half of the basin from east to west. Ship cruises were conducted during winter-spring of 2001-2012 covering different stages of the bloom to study the biogeochemistry of the region. Phytoplankton analysis indicated the presence of green tides of dinoflagellate, Noctiluca scintillans (= N. miliaris), in the oceanic waters. Our observations indicated that diatoms are coupled and often co-exist with N. scintillans, making it a mixed-species ecosystem. In this paper, we describe an approach for detection of bloom-forming algae N. scintillans and its discrimination from diatoms using Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua data in a mixed-species environment. In situ remote sensing reflectance spectra were generated using Satlantic™ hyperspectral radiometer for the bloom and non-bloom waters. Spectral shapes of the reflectance spectra for different water types were distinct, and the same were used for species identification. Scatter of points representing different phytoplankton classes on a derivative plot revealed four diverse clusters, viz. N. scintillans, diatoms, non-bloom oceanic, and non-bloom coastal waters. The criteria developed for species discrimination were implemented on MODIS data and validated using inputs from a recent ship cruise conducted in March 2013. [ABSTRACT FROM AUTHOR]

The dynamics of abundance and biomass ofNoctiluca scintillans(Dinoflagellata) andAcartia clausi(Copepoda) in the Bosphorus area of the Black and Marmara Seas during 2005–2009 has been analyzed. Despite the fact that the more abundant Black Sea zooplankton community permanently enters the Marmara Sea,A. clausiandN. scintillanshave formed independent populations in the northeast of the Marmara Sea. This may be confirmed on the one hand by the positive correlations between the numbers ofA. clausiandN. scintillansindividuals in the Marmara Sea near the Bosphorus Strait and near the Prince Islands and, on the other hand, by a lack of correlation between the abundance of these species in the Marmara Sea and in the Bosphorus area of the Black Sea. The abundance ofN. scintillanswas 6–10 times lower in the Black Sea near the Bosphorus Strait than that in the Marmara Sea. A high correlation (r = 0.84) between the abundance ofN. scintillansand the number of deadA. clausifemales near the Bosphorus Strait in the Marmara Sea suggests an important role of necrozooplankton in the development of the dinoflagellate. [ABSTRACT FROM AUTHOR]

Abstract: Nematocyst discharge and concomitant delivery of toxins is triggered to perform both defence and predation strategies in Cnidarians, and may lead to serious local and systemic reactions in humans. Pelagia noctiluca (Cnidaria, Scyphozoa) is a jellyfish particularly abundant in the Strait of Messina (Italy). After accidental contact with this jellyfish, not discharged nematocysts or even fragments of tentacles or oral arms may tightly adhere to the human skin and, following discharge, severely increase pain and the other adverse consequences of the sting. The aim of the present study is to verify if the local anesthetic lidocaine and other compounds, like alcohols, acetic acid and ammonia, known to provide pain relief after jellyfish stings, may also affect in situ discharge of nematocysts. Discharge was induced by a combined physico-chemical stimulation of oral arms by chemosensitizers (such as N-acetylated sugars, aminoacids, proteins and nucleotides), in the presence or absence of 1% lidocaine, 70% ethanol, 5% acetic acid or 20% ammonia, followed by mechanical stimulation by a non-vibrating test probe. The above mentioned compounds failed to induce discharge per se, and dramatically impaired the chemosensitizer-induced discharge response. We therefore suggest that prompt local treatment of the stung epidermis with lidocaine, acetic acid, ethanol and ammonia may provide substantial pain relief and help in reducing possible harmful local and systemic adverse reaction following accidental contact with P. noctiluca specimens. [Copyright &y& Elsevier]

Highlights: [•] 9 years of synchronous observations in the Black Sea and the northern Adriatic. [•] Cell size structure, feeding activity, seasonal and interannual dynamics were compared. [•] Correlation analysis showed a positive relationship between Noctiluca and eggs of copepods. [•] During the spring peak number of Noctiluca is top-down controlled by the wind. [•] We propose that number of Noctiluca in the early spring and the weather forecast may be used to predict outbreaks and red tide formation. [ABSTRACT FROM AUTHOR]

Dinoflagellate bioluminescence systems operate with or without a luciferin binding protein, representing two distinct modes of light production. However, the distribution, diversity, and evolution of the luciferin binding protein gene within bioluminescent dinoflagellates are not well known. We used PCR to detect and partially sequence this gene from the heterotrophic dinoflagellate Noctiluca scintillans and a group of ecologically important gonyaulacoid species. We report an additional luciferin binding protein gene in N. scintillans which is not attached to luciferase, further to its typical combined bioluminescence gene. This supports the hypothesis that a profound re-organization of the bioluminescence system has taken place in this organism. We also show that the luciferin binding protein gene is present in the genera Ceratocorys, Gonyaulax, and Protoceratium, and is prevalent in bioluminescent species of Alexandrium. Therefore, this gene is an integral component of the standard molecular bioluminescence machinery in dinoflagellates. Nucleotide sequences showed high within-strain variation among gene copies, revealing a highly diverse gene family comprising multiple gene types in some organisms. Phylogenetic analyses showed that, in some species, the evolution of the luciferin binding protein gene was different from the organism's general phylogenies, highlighting the complex evolutionary history of dinoflagellate bioluminescence systems. [ABSTRACT FROM AUTHOR]

Predation pressure of Noctiluca scintillans on diatoms and thecate dinoflagellates was investigated off the western coast of Kyushu, Japan by a comparison between the taxonomic composition of prey in the food vacuoles of N. scintillans and that in the ambient water. The ratios of total diatoms and centric diatoms in the food vacuoles were higher than those in the ambient water, while thecate dinoflagellates and pennate daitoms showed a reverse trend. These results indicate that predation pressure of N. scintillans on total diatoms is higher than on thecate dinoflagellates, and that the pressure on centric diatoms is stronger than that on pennate ones. Among the centric diatoms, Chaetoceros and Bacteriastrum were dominant in the food vacuoles and their respective ratios were higher than in the ambient water. Their chain-forming colonies with long setae appear to be easily trapped by N. scintillans tentacles and this is probably the cause of the high predation pressure of N. scintillans on centric diatoms. [ABSTRACT FROM AUTHOR]

Temperature and nutrient concentrations were measured during a mixed bloom of Noctiluca scintillans and Gymnodinium catenatum in La Paz Bay, Gulf of California. Under laboratory conditions, we offered three concentrations of G. catenatum (312, 625, or 1015 cells mL-1) to 0.53 N. scintillans cells mL-1 to study predation rates. Experiments were carried out with 750 mL of culture during a fiveday period. Sea surface temperature clearly showed a transitional period from colder to warmer water during the bloom. Field and laboratory data showed that N. scintillans fed on G. catenatum. During the trial, more than 70% of N. scintillans cells contained G. catenatum cells in their vacuoles. Ingestion rates varied; the highest ranged from 30 to 40 G. catenatum cells h-1 in each N. scintillans cell. A clear relation to the concentration of the diet was not evident. Low values of 1 to 3 G. catenatum cells h-1 in each N. scintillans cell were typical at the end of the trial. Noctiluca scintillans doubled in concentration about every 48 h; however, numerous trophonts were observed leaving the cytoplasmic membrane, suggesting cell damage. These data indicate that N. scintillans ingests G. catenatum cells but the prey appears to damage predator cells in a relatively short time. [ABSTRACT FROM AUTHOR]

Mesozooplankton are key components of coastal ecosystems, linking the microbial food web to the classic food chain. In this study, species composition and abundance of mesozooplankton is studied for the Daya Bay in April (spring) and October (fall), 2006. A total of 27 species of mesozooplankton were identified in spring and 58 species in fall. Dominant species were Oithona tenuis, Flaccisagitta enflata, Penilia avirostris and Centropages tenuiremis in spring, shifting to Microsetella norvegica, Oithona tenuis and Parvocalanus crassirostris in fall. Higher mesozooplankton abundance was found at Aotou Cove and Dapeng'ao Cove compared to other stations, indicating the influence of eutrophication on mesozooplankton community in the Daya Bay. The outbreak of Noctiluca scintillans bloom in spring reduced the species diversity and abundance of mesozooplankton. [ABSTRACT FROM AUTHOR]

Studies were conducted at the end of June 2011 in the coastal region of the northeastern part of the Black Sea. The bulk of the Noctiluca scintillans population was observed in the thermocline and reached a density of 40000 ind./m. Analysis of digestive vacuoles content showed that Noctiluca could consume cells of Neoceratium tripos and N. furca, which had been considered inedible for Black Sea zooplankton, as well as temporary cysts of dinoflagellates, presumably of the toxic genus Alexandrium. The Noctiluca population consumed in total 10-30% of the abundance of temporary cysts, 2-29% of primary production, and 2-9% of potential Calanus euxinus egg production. For the first time, the excretion rates of ammonium nitrogen and mineral phosphorus were measured for N. scintillans. Our calculations showed that in summer, excretion by Noctiluca contributed from 4 to 18% and from 15 to 53% of phytoplankton total nitrogen and phosphorus requirements, respectively. The specific growth rate of Noctiluca (0.17-0.35) in summer, estimated from data on the daily food intake and respiration rate, was close to the values obtained in spring. [ABSTRACT FROM AUTHOR]

We investigated the haemolytic capacity of the crude venom extracted from isolated nematocysts ofPelagia noctiluca(Cnidaria: Scyphozoa), and evidenced the proteic fractions responsible for this activity. The nematocyst venom was used at various concentrations to evaluate the haemolytic activity and the lysosomal membrane stability of red blood cells of two teleostean species treated with the extract. The nematocyst extract was assayed against erythrocytes of the two teleostean species living in different environments,Carassius auratusas a common freshwater species, andLiza aurataas a representative of seawater species. Experiments on the haemolytic activity ofP. noctilucain the presence of lipid components of erythrocyte membranes showed that sphyngomyelin strongly inhibited this activity. The crude venom was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis SDS-PAGE and high performance liquid chromatography (HPLC) to detect the proteic composition, and it was found that the active haemolytic components of this venom are distributed in at least four protein fractions. The results of our experiments indicated thatPelagia noctilucavenom induces haemolysis and lysosomal membrane destabilisation in both species and thatCarassius auratuswas more susceptible to jellyfish venom than wasLiza aurata. No significant differences in glutathione (GSH) levels were observed between control and treatments; consequently the toxins do not cause the oxidative stress but likely recognize specific targets (i.e. sphyngomyelin) in the plasmatic membrane of red blood cells. [ABSTRACT FROM PUBLISHER]

Abstract: Jellyfish blooms are generally attributed to a biological response to the environment, neglecting the role of transport patterns in redistributing existing populations. Here, we use high-resolution (1.25km) ocean modeling to examine the role of transport in the onshore arrival and abundance of the pelagic stinging jellyfish Pelagia noctiluca on the Ligurian Sea coast. Jellyfish are modeled as Lagrangian particles with a 0–300-m diel vertical migration typical of P. noctiluca. Over the course of a year, onshore arrivals are not restricted to the summer. Arrivals are concentrated at capes, but abundance can reach maxima in bays and in the lee of capes. Two factors impact jellyfish arrivals at the coast: the position of the Northern Current and the wind. A comparison of summer 2006 and available onshore jellyfish observations suggests a correct capture of the main stranding events by the model. These results have implications for understanding long-term fluctuations. [Copyright &y& Elsevier]

A massive algal bloom of the dinoflagellate Noctiluca miliaris (green) was located in the Northern Arabian Sea by IRS-P4-2 (OCM-II) for microbiological studies, during two consecutive cruises of February-March 2009. Culturable bacterial load during bloom were ∼2-3-fold higher in comparison to non-bloom waters and ranged from 3.20 × 10 to 6.84 × 10 cfu ml. An analysis of the dominant heterotrophs associated with Noctiluca bloom resulted in phylogenetic and a detailed metabolic characterization of 70 bacterial isolates from an overlapping active and declining bloom phase location near north-central Arabian Sea. The active phase flora was dominated by Gram-positive forms (70.59 %), a majority of which belonged to Bacillus (35.29 %) of Firmicutes. As the bloom declined, Gram-negative forms (61.11 %) emerged dominant, and these belonged to a diverse γ-proteobacterial population consisting of Shewanella (16.67 %) and equal fractions of a Cobetia-Pseudomonas-Psychrobacter-Halomonas population (36.11 %). A Unifrac-based principal coordinate analysis of partial 16S rDNA sequences showed significant differences among the active and declining phase flora and also with reported endocytic flora of Noctiluca (red). A nonparametric multidimensional scaling (NMDS) of antibiogram helped differentiation among closely related strains. The organic matter synthesized by N. miliaris appears to be quickly utilized and remineralized as seen from the high efficiency of isolates to metabolize various complex and simple C/N substrates such as carbohydrates, proteins/amino acids, lipids, sulfide production from organic matter, and solubilize phosphates. The ability of a large fraction of these strains (50-41.67 %) to further aerobically denitrify indicates their potential for nitrogen removal from these high-organic microniches of the Noctiluca bloom in the Arabian Sea, also known for high denitrification activity. The results indicate that culturable euphotic bacterial associates of Noctiluca are likely to play a critical role in the biogeochemical ramifications of these unique seasonally emerging tropical open-water blooms of the Northern Arabian Sea. [ABSTRACT FROM AUTHOR]

Abstract: To identify some of the possible environmental factors stimulating the increasingly frequent outbreaks of the scyphomedusa Pelagia noctiluca in the Straits of Messina, we investigated its abundance, growth, reproduction and feeding over a 4-year period, from 2007 to 2011, at two coastal sites. Using either field investigations and manipulative experiments we show that, among the various factors considered, shifts in water temperature (influencing medusae metabolism, growth and reproduction rates) and the size structure of the zooplankton community (their natural preys) can promote the proliferation of P. noctiluca. In particular, we show that increased temperature let jellyfishes to grow more rapidly and reach exceptional sizes. We also report a peculiar opportunistic behavior of P. noctiluca, which makes this species a potentially strong competitor in the pelagic trophic web of the Straits ecosystem. We therefore propose that more frequent P. noctiluca outbreaks stimulated by increasing sea surface temperature and shifts in their prey availability and composition would become, in the near future, a major cause of ecosystem shift. [Copyright &y& Elsevier]

In recent years, seasonal blooms of the dinoflagellate Noctiluca miliaris have appeared in the open-waters of the northern Arabian Sea (NAS). This study provides the first characterization of bacteria from a seasonal bloom of green Noctiluca of NAS (20°N−17°N and 64°E-70°E), during the spring-inter-monsoon cruise of Sagar Sampada 253, in March 2007. Bacterial growth as assessed by most-probable number (MPN) and plate counts, revealed 'variable-physiotypes' over a wide range of salinities (0%-25% w/v NaCl), pH levels (5-8.5), and organic nutrient strengths, in comparison to non-bloom waters. MPN indices of bacteria in surface waters of bloom stations *DWK and *PRB, corresponded to (3.08-4.41)×10 cells/mL at 3.5% NaCl (w/v), and (2.82-9.49)×10 cells/mL at 25% (w/v) NaCl in tryptone-yeast extract broth (TYE). Plate counts were (1.12-4)×10 CFU/mL at 0% (w/v) NaCl, (1.28-3.9)×10 CFU/mL at 3.5% (w/v) NaCl, and (0.4-7)×10 CFU/mL at 25% NaCl (w/v) on TYE. One-tenth-strength Zobell's gave (0.6-3.74)×10 CFU/mL at pH 5 to (3.58-7.5)×10 CFU/mL at pH 8.5. These bacteria were identified to the genera Bacillus, Cellulomonas, Staphylococcus, Planococcus, Dietzia, Virgibacillus, Micrococcus, Sporosarcinae, Leucobacter, and Halomonas. The identity of three strains (GUFBSS253N2, GUFBSS253N30, and GUFBSS253N84) was confirmed through 16S rDNA sequence homology as Bacillus cohnii, Bacillus flexus, and Bacillus cereus. The ∼2-3-fold higher plate counts of culturable bacteria from the open-waters of the NAS indicate that these bacteria could critically determine the biogeochemical dynamics of the bloom and its milieu. The role of these bacteria in sustaining/terminating the bloom is under evaluation. [ABSTRACT FROM AUTHOR]

The invasive ctenophore Mnemiopsis leidyi, which now may be established in the NW Mediterranean, is a voracious predator of zooplankton and ichthyoplankton. Pelagia noctiluca, an abundant scyphomedusa there, eats other gelatinous species. We measured predation, digestion and escape when different sizes of medusae fed on ctenophores. Clearance rates increased with predator size and ingestion rates increased with prey concentration. Digestion times were longer when medusae were smaller than the ctenophores. All large ctenophores escaped from the medusae, but small ctenophores were ingested completely. Pelagia noctiluca is potentially an important predator of M. leidyi that may help control populations of this ctenophore. [ABSTRACT FROM AUTHOR]

Algal blooms have been documented along the west and east coasts of India. A review of bloom occurrences in Indian waters from 1908 to 2009 points out that a total of 101 cases have been reported. A comparison of the bloom cases reported before and after the 1950s reveals that there is an increase in the number of bloom occurrences. The reports of algal blooms indicate their predominance along the west coast of India especially the southern part. Majority of the blooms reported along the west coast of India are caused by dinoflagellates, whereas diatom blooms prevail along the east coast. There have been 39 causative species responsible for blooms, of which Noctiluca scintillans and Trichodesmium erythraeum are the most common. Reporting of massive fish mortality in Indian waters has been associated with the blooming of Cochlodinium polykrikoides, Karenia brevis, Karenia mikimotoi, N. scintillans, T. erythraeum, Trichodesmium thiebautii and Chattonella marina. Most of the blooms occurred during withdrawal of the south-west monsoon and pre-monsoon period. In Indian waters, this process is mainly influenced by seasonal upwelling and monsoonal forcing that causes high riverine discharge resulting in nutrient-enriched waters that provides a competitive edge for blooming of phytoplankton species. [ABSTRACT FROM AUTHOR]

Pelagia noctiluca is thought to have a global distribution, yet our understanding of genetic connectivity across the range of this problem animal is poor. Here, we investigate the genetic structure of populations off southern Africa using mitochondrial COI and nuclear ITS1 and ITS2 genes, and compare the results to recent work conducted in the North-East Atlantic. Analyses showed significant differentiation between the southern and northern Atlantic population groups (COI Φ st = 0.72, ITS2 Φ st = 0.23, p < 0.001), which suggests historical rather than contemporary gene flow. Southern African samples showed high haplotypic (h = 1) and low nucleotide (π = 0.008) diversity, similar to those from Europe. Phylogenetic analyses suggest South African samples to have diverged earlier than those from the northern Atlantic. [ABSTRACT FROM AUTHOR]