Regional climate and patterns of phytoplankton annual succession in the open waters of the Black Sea

Mikaelyan, Alexander S.; Kubryakov, A. A.; Силкин, В. А.; Паутова, Л. А.; Часовников, В. К.

doi:10.1016/j.dsr.2018.08.001

Cited by 52 publications

(50 citation statements)

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“…CC BY 4.0 License. productivity not only during winter-spring bloom of phytoplankton, but also in the following months in agreement with the results of previous investigators (Burenkov et al, 2011;Finenko et al, 2014;Mikaelyan et al, 2015Mikaelyan et al, , 2018Kubryakova et al, 2018). In particular, this effect is a probable reason for the unusually strong coccolithophore bloom in May-July 2017, which was documented on the base of satellite and Bio-Argo measurements by Kubryakov, Mikaelyan, et al (2019).…”

Section: Bio-optical Characteristics In Years With Cold and Warm Wintersupporting

confidence: 93%

“…The intensity of winter convection in the Black Sea, impact on the phytoplankton concentration in both cold and warm period of the year, as well as on its yearly-averaged characteristics. The most intense winter-early spring bloom of diatoms (Mashtakova, 1985;Sorokin, 2002;Mikaelyan et al, 2018) and the following early-summer bloom of coccolithophores (Mikaelyan et al, 2015;Silkin et al, 2014Silkin et al, , 2019 in the Black Sea are observed after cold winters and are both related to the entrained in winter nutrients. The biomodelling study by Kubryakova et al (2018) shows that the peak values of the subsurface phytoplankton maximum in summer in the Black Sea also depend on the winter convection.…”

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confidence: 99%

“…Satellite data demonstrated that the variability of surface concentration of chlorophyll-а (Chl) on interannual time scales is correlated with winter sea surface temperature Finenko et al, 2014). Moreover, long-term analysis of in-situ data (Mikaelyan et al, 2018) showed that winter temperature significantly affects the taxonomic composition and seasonal succession of phytoplankton in the Black Sea throughout the whole warm period of the year.…”

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confidence: 99%

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Warmer winters causes an increase of chlorophyll-a concentration in deeper layers: the opposite role of convection and self-shading on the example of the Black Sea

Kubryakova

Kubryakov

2020

Preprint

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Abstract. Winter vertical entrainment of deep waters determines not only the amount of nutrients in the upper layers, but also the light conditions in it, through the self-shading mechanism. In this paper, we use Bio-Argo data to demonstrate significant differences in the vertical distribution of chlorophyll-a concentration (Chl) in the Black Sea between a year with cold winter (2017) and a year with warm winter (2016). Stronger vertical entrainment of nutrient-rich waters from deeper isopycnal layers in cold 2017 caused an increase of Chl in winter up to 0.6–0.7 mg/m3 compared to a warm winter of 2016, when Chl was only 0.4–0.5 mg/m3. Further, during almost the whole year from February to October Chl in the upper 0–40 m layer of cold 2017 year was on 0.1–0.2 mg/m3 higher than in 2016. This rise of Chl in 2017 led to an increase in light attenuation due to the self-shading effect. In contrast, in warm 2016 with a lower amount of nutrients light attenuation decreased and the irradiance reached deeper isopycnals layers with a higher amount of nutrients. As a result, in warm 2016 the subsurface chlorophyll maximum deepens and the values of Chl in 40–60 m layers were significantly higher than in 2017. The maximum positive difference in this layer (0.5 mg/m3) was observed during a summer seasonal peak of irradiance due to the largest increase of light attenuation in the summer of 2017. As a result, the column-averaged yearly values of Chl in warm 2016 and cold 2017 were comparable. However, in the year with intense winter mixing upper layers are more productive, while in the year with low winter vertical mixing, subsurface chlorophyll maximum widens and reaches deeper layers. These results show that the observed long-term warming may lead to the continuous deepening of the subsurface chlorophyll maximum in the ocean.

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Section: Bio-optical Characteristics In Years With Cold and Warm Wintersupporting

confidence: 93%

mentioning

confidence: 99%

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confidence: 99%

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Warmer winters causes an increase of chlorophyll-a concentration in deeper layers: the opposite role of convection and self-shading on the example of the Black Sea

Kubryakova

Kubryakov

2020

Preprint

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“…Spring blooms are of smaller magnitude than the winter ones, and they attain a maximum in the second half of April for 'warm' years and at the end of April/beginning of May for 'cold' years. In summary, our results show, in agreement with the existing literature [5,55], that the lower winter nutrient supply from the storage in 'warm' years is a key factor in shaping the winter Black Sea phytoplankton bloom. In addition, our model clearly indicates the presence of both winter and spring blooms regardless of local meteorological and oceanographic conditions, and that the winter bloom in 'cold' years is more intense.…”

Section: Seasonal Variability Of Physupporting

confidence: 92%

“…We set out to investigate the processes which are responsible for these premature blooms in autumn. Erosion of the thermocline and vertical mixing, due to surface cooling and strong winds typically start at the end of November, hence, they cannot be directly responsible for the early autumn bloom observed in References [9,55,59]. Figure 12 illustrates possible mechanisms for the early autumn bloom.…”

Section: Mechanism Behind Autumn Blooms In the Black Seamentioning

confidence: 99%

Seasonal and Inter-Annual Variability of the Phytoplankton Dynamics in the Black Sea Inner Basin

Miladinova

Adolf

Moy

et al. 2020

Oceans

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We explore the patterns of Black Sea phytoplankton growth as driven by the thermohaline structure and circulation system and the freshwater nutrient loads. Seasonal and inter-annual variability of the phytoplankton blooms is examined using hydrodynamic simulations that resolve mesoscale eddies and online coupled bio-geochemical model. This study suggests that the bloom seasonality is homogeneous across geographic locations of the Black Sea inner basin, with the strongest bloom occurring in winter (February–March), followed by weaker bloom in spring (April–May), summer deep biomass maximum (DBM) (June–September) and a final bloom in autumn (October–November). The winter phytoplankton bloom relies on vertical mixing of nitrate from the intermediate layers, where nitrate is abundant. The winter bloom is highly dependent on the strength of the cold intermediate layers (CIL), while spring/summer blooms take advantage of the CIL weakness. The maximum phytoplankton transport across the North Western Shelf (NWS) break occurs in September, prior to the basin interior autumn bloom. Bloom initiation in early autumn is associated with the spreading of NWS waters, which in turn is caused by an increase in mesoscale eddy activity in late summer months. In summary, the intrusion of low salinity and nitrate-rich water into the basin interior triggers erosion of the thermocline, resulting in vertical nitrate uplifting. The seasonal phytoplankton succession is strongly influenced by the recent CIL disintegration and amplification of the Black Sea circulation, which may alter the natural Black Sea nitrate dynamics, with subsequent effects on phytoplankton and in turn on all marine life.

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Reconsideration of the phytoplankton seasonality in the open Black Sea

Yunev¹,

Carstensen

Stelmakh³

et al. 2020

Limnol Oceanogr Letters

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Phytoplankton production supports the entire food web of the open Black Sea, and it is believed that new production is sustained by inputs of nitrate from deeper waters during winter convective mixing. However, this current assertion is primarily based on analyses of chlorophyll a (Chl a) data, disregarding the large seasonal variations in cell-specific Chl a depending on the species, light intensity and nutrient concentrations. Our study shows that phytoplankton biomass in the open Black Sea primarily accumulates during late summer and autumn, when nitrate is depleted in the surface layer. The enhanced productivity could be driven by large diatoms harvesting nutrients from depths and nitrogen fixation by cyanobacteria, living in symbiotic relationship with diatoms.

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Regional climate and patterns of phytoplankton annual succession in the open waters of the Black Sea

Cited by 52 publications

References 53 publications

Warmer winters causes an increase of chlorophyll-a concentration in deeper layers: the opposite role of convection and self-shading on the example of the Black Sea

Warmer winters causes an increase of chlorophyll-a concentration in deeper layers: the opposite role of convection and self-shading on the example of the Black Sea

Seasonal and Inter-Annual Variability of the Phytoplankton Dynamics in the Black Sea Inner Basin

Reconsideration of the phytoplankton seasonality in the open Black Sea

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