The key to dinoflagellate (Noctiluca scintillans) blooming and outcompeting diatoms in winter off Pakistan, northern Arabian Sea

Chen, Xiang; Tan, Yehui; Zhang, Huangchen; Liu, Jiaxing; Ke, Zhixin; Li, Gang

doi:10.1016/j.scitotenv.2019.07.202

Cited by 31 publications

(21 citation statements)

References 39 publications

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“…Since they were first detected in the early 2000s 29,31,32,35,36 green Noctiluca blooms have become increasingly more pervasive over diatoms ( Fig. S5) and more widespread, occurring every winter with predictable regularity 33,[35][36][37][38][39][40] .…”

Section: Resultsmentioning

confidence: 99%

Ecosystem state change in the Arabian Sea fuelled by the recent loss of snow over the Himalayan-Tibetan Plateau region

Goés

Tian

Gomes

et al. 2020

Sci Rep

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The recent trend of global warming has exerted a disproportionately strong influence on the Eurasian land surface, causing a steady decline in snow cover extent over the Himalayan-tibetan plateau region. Here we show that this loss of snow is undermining winter convective mixing and causing stratification of the upper layer of the Arabian Sea at a much faster rate than predicted by global climate models. over the past four decades, the Arabian Sea has also experienced a profound loss of inorganic nitrate. in all probability, this is due to increased denitrification caused by the expansion of the permanent oxygen minimum zone and consequent changes in nutrient stoichiometries. these exceptional changes appear to be creating a niche particularly favorable to the mixotroph, Noctiluca scintillans which has recently replaced diatoms as the dominant winter, bloom forming organism. Although Noctiluca blooms are non-toxic, they can cause fish mortality by exacerbating oxygen deficiency and ammonification of seawater. As a consequence, their continued range expansion represents a significant and growing threat for regional fisheries and the welfare of coastal populations dependent on the Arabian Sea for sustenance. The Arabian Sea (AS) is a unique, low-latitude oceanic ecosystem because it is influenced by monsoonal winds that reverse their direction seasonally 1. These reversing winds cause dynamic shifts in surface currents and alterations in the pycnocline, which help fertilize its normally nutrient-depleted surface layers. However, the mechanisms that drive water-column mixing, the upward transport of nutrients and the consequent upsurge of phytoplankton biomass during the summer (Jun.-Sep.) and the winter (Nov.-Feb.) monsoons are different 2-6. During the summer monsoon, nutrient enrichment is via coastal upwelling, which begins when the adjacent land mass becomes warmer relative to the AS, and low pressure develops over the Arabian Peninsula 3,7,8. During this time of the year, strong topographically-steered southwesterly winds blowing over the AS form a low-level atmospheric jet called the Findlater Jet 9. This jet induces a northeastwardly flow of the surface currents, leading to strong upwelling of deep, nutrient-rich waters, causing large phytoplankton blooms along the coasts of Somalia, Yemen, and Oman 3,5,6,10,11. In contrast, during winter, when the Eurasian continent cools, nutrient enrichment is via deep penetrative convective mixing as a result of excessive heat loss from the AS surface layer caused by cold and dry northeasterly winds blowing from the snow-covered Himalayan-Tibetan Plateau (HTP) 4,5. The erosion of the thermocline, and entrainment of deep (100-150 m) nutrient-rich waters into the surface layer of the AS, begins as early as Dec., and has a major influence on winter phytoplankton blooms observable as far south as 14°N 4,11,12 .

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Section: Resultsmentioning

confidence: 99%

Ecosystem state change in the Arabian Sea fuelled by the recent loss of snow over the Himalayan-Tibetan Plateau region

Goés

Tian

Gomes

et al. 2020

Sci Rep

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“…In nature, phytoplankton live as deep as 200 m (euphotic zone) of the water column in the oceans and evolve various strategies to exist therein through, e.g., chain-forming and setae-own [14]. They can also be exposed occasionally or constantly to low O 2 and even hypoxia that often vertically expands from thousands of meters to a few meters of seawater column [15]. The low O 2 /hypoxia phenomena even expands to shallower than 5 m in the Pearl River estuary [16] or less than 30 m in the Changjiang River estuary [17].…”

Section: Introductionmentioning

confidence: 99%

“…The low O 2 /hypoxia phenomena even expands to shallower than 5 m in the Pearl River estuary [16] or less than 30 m in the Changjiang River estuary [17]. In these areas, phytoplankton cells usually vertically live from surface to deeper than 50 m depth [16,17]; they even live as deep as 150 m in the Arabia Sea, where the O 2 -deficient zone can expand to shallower than 50 m [15]. This means that most of phytoplankton cells in hypoxic areas experience a low O 2 /hypoxia status.…”

Section: Introductionmentioning

confidence: 99%

Lowering pO2 Interacts with Photoperiod to Alter Physiological Performance of the Coastal Diatom Thalassiosira pseudonana

Chen

Liu

et al. 2021

Microorganisms

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Exacerbating deoxygenation is extensively affecting marine organisms, with no exception for phytoplankton. To probe these effects, we comparably explored the growth, cell compositions, photosynthesis, and transcriptome of a diatom Thalassiosira pseudonana under a matrix of pO2 levels and Light:Dark cycles at an optimal growth light. The growth rate (μ) of T. pseudonana under a 8:16 L:D cycle was enhanced by 34% by low pO2 but reduced by 22% by hypoxia. Under a 16:8 L:D cycle, however, the μ decreased with decreasing pO2 level. The cellular Chl a content decreased with decreasing pO2 under a 8:16 L:D cycle, whereas the protein content decreased under a 16:8 L:D cycle. The prolonged photoperiod reduced the Chl a but enhanced the protein contents. The lowered pO2 reduced the maximal PSII photochemical quantum yield (FV/FM), photosynthetic oxygen evolution rate (Pn), and respiration rate (Rd) under the 8:16 or 16:8 L:D cycles. Cellular malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were higher under low pO2 than ambient pO2 or hypoxia. Moreover, the prolonged photoperiod reduced the FV/FM and Pn among all three pO2 levels but enhanced the Rd, MDA, and SOD activity. Transcriptome data showed that most of 26 differentially expressed genes (DEGs) that mainly relate to photosynthesis, respiration, and metabolism were down-regulated by hypoxia, with varying expression degrees between the 8:16 and 16:8 L:D cycles. In addition, our results demonstrated that the positive or negative effect of lowering pO2 upon the growth of diatoms depends on the pO2 level and is mediated by the photoperiod.

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“…A recent study based on CPJE nutrient profiles (e.g., total dissolved nitrogen, total dissolved phosphorus, and dissolved silicon) infers a similar conclusion that the pumping effect of cyclonic eddies temporally promotes nutrients, especially Noctiluca scintillans , upwelling from the subsurface and blooming in surface water (Xiang et al, 2019). However, limited by the short measuring period, the CPJE observations failed to capture the propagating features of the identified isolated cyclonic eddy, which is supposed to act as slow‐moved Rossby wave.…”

Section: Resultsmentioning

confidence: 75%

Evidence of Eddy‐Enhanced Winter Chlorophyll‐a Blooms in Northern Arabian Sea: 2017 Cruise Expedition

Wang

Liao

et al. 2020

JGR Oceans

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The temperature, salinity, and chlorophyll-a (Chl-a) profiles of the upper ocean (0-200 m) were measured during the China-Pakistan Joint Expedition, 2017. The cruise track passed through an identified cyclonic eddy, and the multi-disciplinary records thus verify the eddy contributions to winter blooms in the northern Arabian Sea (AS). The records show that the strength of upper blooms within the mixed layer is mainly dominated by surface phytoplankton biomass (the Chl-a concentration), which increases simultaneously with the shallow mixed layer and uplifted thermocline. A composite analysis of eddy-tracked sea level anomalies (SLA) and Chl-a reveals the pumping and stirring effects that cyclonic eddies make to the ocean surface nutrient supply. Based on the high-resolution Ocean General Circulation Model for the Earth Simulator (OFES) outputs, a mixed layer nitrogen budget calculation was subsequently conducted to quantify the contributions of mesoscale eddies to 10-year climatological winter blooms. The results indicate that eddy flows are primary contributors to the increased nutrients in the coastal north AS during the mature period (usually in January and February) of the winter blooms, with a concentration histogram double that of convective mixing. The concentration decreases from the north to south, agreeing well with the seasonal northward nutrition gradient. This confirms that (i) the growth of nutrients over the northern AS, which is known to be triggered by convective mixing, would be further maintained by eddy-induced advection; and (ii) higher concentration of nutrients would facilitate an easier response of Chl-a to eddy dynamics.Plain Language Summary In this study, we investigated the wintertime phytoplankton blooms in the northern Arabian Sea (AS) based on the China-Pakistan Joint Expedition, 2017. As a case study, this work verifies that horizontal and vertical transports of mesoscale eddies have facilitated the regional surface winter blooms. Eddy effects primarily contribute to the increased nutrients in the coastal north AS during the mature phase of the winter blooms, giving estimate double that of convective mixing.

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The key to dinoflagellate (Noctiluca scintillans) blooming and outcompeting diatoms in winter off Pakistan, northern Arabian Sea

Cited by 31 publications

References 39 publications

Ecosystem state change in the Arabian Sea fuelled by the recent loss of snow over the Himalayan-Tibetan Plateau region

Ecosystem state change in the Arabian Sea fuelled by the recent loss of snow over the Himalayan-Tibetan Plateau region

Lowering pO2 Interacts with Photoperiod to Alter Physiological Performance of the Coastal Diatom Thalassiosira pseudonana

Evidence of Eddy‐Enhanced Winter Chlorophyll‐a Blooms in Northern Arabian Sea: 2017 Cruise Expedition

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