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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.

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Factors responsible for the sudden outburst of Noctiluca scintillans in the Chennai coastal waters, southeast coast of India – a case study

Mishra Pravakar, Begum Mehmuna, Gera Anitha, Kumar B. Charan, Garlapati Deviram, Pradhan Uma Kanta, Vashi Athan, Bandyopadhyay Debasmita, Naik Subrat J., Panda Uma Sankar, Ramana Murthy Mallavarapu Venkata

Oceanologia

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2022

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No. 64 (4)

781--788

EN

The paper discusses the factors associated with the sudden outbreak of the nocturnal heterotrophic bioluminescent dinoflagellate Noctiluca scintillans along the Chennai coast. The bloom occurred along a stretch of 16 km following a spell of heavy rain in August 2019. The density of N. scintillans varied from 1000 to 19000 cells/L, with a distinguished distribution pattern. High N. scintillans abundance was recorded at Panaiyurkuppam and Kovalam, with 19000 cells/L and 18000 cells/L, recorded respectively. Adequate nutrients brought by substantial rainfall and a high abundance of the diatom Thalassiosira sp. triggered the N. scintillans bloom. The low wind speed (5 m/sec), lowering of atmospheric temperature (from 24.00 to 31.00°C, 27.5 ± 1.17°C), high rainfall (6 mm within one day), and low sea surface temperature (SST) (from 25.20 to 31.00°C, 29.37± 1.17°C) are probable environmental cues. Local hydrodynamics and the diverging currents governed the presence and dispersion of the bloom in the region.

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Low-active high-density Noctiluca scintillans cells in surface seawater

Tada Kuninao, Asahi Toshimasa, Kitatsuji Saho, Nomura Mika, Yamaguchi Hitomi, Ichimi Kazuhiko

Oceanologia

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2020

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No. 62 (3)

402--407

EN

Noctiluca scintillans is an important member of the mesozooplankton in terms of biomass and production in the Seto Inland Sea, Japan. The densities and adenosine triphosphate (ATP) contents of N. scintillans cells were measured. Vertical profiles of N. scintillans cellular activity in the coastal water were determined and the ATP contents were high at middle layers, with a maximum depth of 10 m. ATP contents were low in the surface and lower layers. These results suggest that active N. scintillans cells in subsurface layers with low density play an important role in the coastal ecosystem, and high-density cells in the surface water are not active.

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Characterization of light absorption coefficient of red Noctiluca scintillans bloom in the South Eastern Arabian Sea

Shaju S. S., Akula R. R., Jabir T.

Oceanologia

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2018

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No. 60 (3)

419--425

EN

The red Noctiluca scintillans bloom was observed off Cochin in the South Eastern Arabian Sea (SEAS), affecting a very large area during July-August 2016. The surface water samples from the bloom region were collected to study the physical, biological and light absorption characteristics. The bloom affects the food chain by their voracious predation on the species of both first and second trophic levels. The N. scintillans cell density during the bloom was estimated at 4.73 × 105 cells l−1. In the phytoplankton absorption coefficient spectra, the accessory pigments displayed peaks in the 488-558 nm regions, which represent the characteristic carotenoid pigment (red colored pigment) for the bloom of red Noctiluca. Signature of the coastal upwelling was found from the salinity and temperature distribution, which was measured prior to the bloom occurrence. From the sea surface temperature (SST), it is also confirmed the presence of fresh water from the Cochin estuary. Increased productivity near coastal region, along with episodic events of strengthening of the upwelling, favors the proliferation of smaller diatoms. The plankton succession from smaller diatoms to larger diatoms and dinoflagellates, favors the proliferation of the red Noctiluca. The occurrence of blooms of red N. scintillans, which feed on phytoplankton, mainly diatoms, and other dinoflagellates, could be a threat to larvae of oil sardine during the upwelling period, and may negatively impact on the commercially important fishery of oil sardine, in this region.

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Red tides of the dinoflagellate Noctiluca scintillans associated with eutrophication in the Sea of Marmara (the Dardanelles, Turkey)

Turkoglu M.

Oceanologia

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2013

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No. 55 (3)

709--732

EN

This investigation focused on weekly variations in cell density and volume of the dinoflagellate Noctiluca scintillans between March 2001 and January 2004 in the Dardanelles. March-June and October-December periods were excessive bloom periods. During the bloom periods the density of N. scintillans reached 2.20 × 105 cells L-1 with a volume of 1.32 × 1012 µm3 L-1. In addition to the high surface density, there was an increase in subsurface waters during the blooms. The bloom of N. scintillans, like that of diatom and other dinoflagellate blooms, was associated not only with eutrophication, but also with stable temperatures and salinities.

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First report on Noctiluca scintillans blooms in the Red Sea off the coasts of Saudi Arabia: consequences of eutrophication

Mohamed Z.A., Mesaad I.

Oceanologia

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2007

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No. 49 (3)

337-351

EN

Blooms of Noctiluca scintillans are reported for the first time in the Red Sea off the south-western coasts of Saudi Arabia. During the present study, surface water samples were collected weekly on the coasts of the Al Shuqayq region from February to April 2004-2006. The abundance of N. scintillans correlated negatively with most nutrients, as well as the cell densities of diatoms and dinoflagellate species. Microscopic examination of live cells from Noctiluca blooms showed the presence of some species of diatoms and dinoflagellates within the Noctiluca body - confirmation of its grazing on these microalgae. The presence of a Noctiluca bloom in the coastal waters off south-western Saudi Arabia could be linked indirectly to water eutrophication by an increase in prey abundance. The physico-chemical properties of Red Sea coastal waters should therefore be monitored regularly in order to minimize the formation of harmful algal blooms, which may affect all food web levels, including the human level.