Morphology and bloom dynamics of Cochlodinium geminatum (Schütt) Schütt in the Pearl River Estuary, South China Sea
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Bloom
Dinoflagellate
Abstract Dinoflagellate and diatom blooms often occur in the East China Sea (ECS) during spring and summer. Some of the dinoflagellate blooms are toxic, resulting in widespread economic damage. In order to mitigate the negative impacts, remote‐sensing methods that can effectively and accurately discriminate between bloom types are demanded for early warning and continuous monitoring of bloom events at large scales. An in situ bio‐optical data set collected from diatom and dinoflagellate blooming waters indicates that the two types of blooms exhibited distinctive differences in the shapes and magnitudes of remote‐sensing reflectance ( R rs ). The ratio of in situ measured R rs spectral slopes at two spectral ranges (443–488 and 531–555 nm, bands available with the moderate resolution imaging spectrometer (MODIS) sensor), abbreviated as BI (representing bloom index), was found effective in differentiating dinoflagellates from diatoms. Reflectance model simulations, which were carried out using in situ and algal culture data as input, provided consistent results. A classification approach for separating dinoflagellate from diatom blooms in the ECS was then developed: When fluorescence line height (FLH) is doubled over the background level and total absorption coefficient at 443 nm ≥ 0.5 m −1 , if 0.0 BI 0.3, it suggests a dinoflagellate bloom; if 0.3 BI 1.0, it suggests a diatom bloom. Finally, the approach was applied to MODIS measurements over the ECS, and a series of diatom and dinoflagellate bloom events during April–June 2005 and 2011 were successfully identified, suggesting that the proposed approach is generally valid for the ECS.
Dinoflagellate
Bloom
Red tide
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Dinoflagellate
Bloom
Dinophyceae
Red tide
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Abstract Ocean-related global changes have altered phytoplankton community structure, especially the diatom-dinoflagellate competition, which further influences ecosystem structure and functions. The pivotal ecological roles of diatoms and dinoflagellates are strongly related with their biochemical compositions, while quantitative comparisons of biochemical changes between diatoms and dinoflagellates under variable environments are still limited. We investigated responses of lipid biomarkers (sterols and fatty acids (FAs)) to different temperatures (12, 18 and 24℃), nitrogen and phosphorus concentrations and their molar ratios (N:P ratio) of 10:1, 24:1 and 63:1 in marine diatom Phaeodactylum tricornutum and dinoflagellate Prorocentrum minimum . Over these wide ranges of temperature and nutrient conditions, sterol and FA profiles were relatively stable in the two species. For C-normalized contents of major sterols and FAs, warming caused non-significant changes in the diatom but an increase (up to 153%) in the dinoflagellate; eutrophication caused an overall decrease (up to 53%) in the diatom but an overall increase (up to 77%) in the dinoflagellate; in contrast, imbalanced N:P ratios caused an overall increase (up to 64%) in the diatom but an overall decrease (up to 53%) in the dinoflagellate. Under future ocean warming, eutrophication and imbalanced N:P ratios, major sterol and polyunsaturated FA contents would increase (ca. 9% ~ 48%) in the dinoflagellate, while those in the diatom would change non-significantly. This study expands our knowledge on lipid-based indicators of phytoplankton under changing environments, which by systematically linking with several other aspects of food quality will help to understand the ecological role of diatom-dinoflagellate community changes.
Dinoflagellate
Phaeodactylum tricornutum
Marine ecosystem
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Spatial and temporal distributions of Peridinium penardii were studied during a spring bloom. Blooms developed at the mouths of tributary streams after periods of high runoff and lasted for about 3 weeks. Allochthonous inputs may be necessary for the development of dinoflagellate blooms in this reservoir.
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Population density
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Summary 1. The abundance of cysts of the bloom‐forming dinoflagellate Peridinium gatunense in the sediments of Lake Kinneret and the effects of environmental conditions on encystment were studied in relation to bloom dynamics. Peak cyst formation coincided with the highest growth rate of the population, prior to bloom peak. 2. Peridinium cysts were counted in water and sediment corer samples from 2000 to 2003 and in archived sediment trap samples collected during 1993–94. The cyst data were examined in relation to ambient temperature and nutrient records, and revealed no direct correlation. 3. In laboratory encystment experiments with Peridinium cells collected from the lake, 0.2–3% of the vegetative cells encysted. Temperature, light and cell density had no significant effect on the percentage of encystment. 4. Cysts were always present in the lake sediments but their abundance in ‘non Peridinium ’ years was much lower than after a massive bloom. Vegetative cells were always present in the water column after the collapse of the annual dinoflagellate bloom, potentially serving as the inoculum for the next bloom. We propose that the hardy cysts serve as an emergency ‘gene bank’ to initiate population build up following catastrophic die outs.
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Bloom
Sediment trap
Epiphyte
Red tide
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