Mechanisms of regulation of invasive processes in phytoplankton on the example of the north-eastern part of the Black Sea

Abstract

In the north-eastern part of the Black Sea, the seasonal complexes of dominant species of phytoplankton were fixed: small-celled diatom (spring), coccolithophores (late spring, early summer) and large diatoms (summer and autumn). In May-June 2005 and 2006, two invasive species of marine diatoms Chaetoceros throndsenii (maximal abundance 1.92 9 10 5 cells/l) and Chaetoceros minimus (1.6 9 10 5 cells/l) were recorded. These species have been incorporated in the complex of the late spring and early summer and grew simultaneously with the coccolithophore Emiliania huxleyi. The coccolithophore was dominant species, whose abundance had reached the level of a bloom. C. throndsenii was observed over the entire area from the coast to the centre of the sea; C. minimus were recorded at coastal stations and only at two stations of the open sea. Stratification of the water mass and the low (below the Redfield) ratio of nitrogen to phosphorus were observed at this time. Then, C. throndsenii was not marked even once, and C. minimus has been registered once on a shelf in June 2011. Experimental studies (2005) have shown that intensive growth C. throndsenii requires the simultaneous addition of nitrogen and phosphorus in a ratio close to the Redfield ratio. C. minimus shows the intensive growth only at high concentrations of phosphorus and at low nitrogento-phosphorus ratio (the experiment was carried out in June 2011). Mathematical modelling shows that C. throndsenii and Emiliania huxleyi form a stable couple whose growth is limited by different factors: the diatoms by nitrogen and the coccolithophores by phosphorus. C. minimus might not be able to form a stable couple with coccolithophores because they have the same limiting factor, i.e. phosphorus. However, this species could become the dominant one, if low (0.5-1) nitrogen-tophosphorus ratio conditions were stable for more than 2 months. However, this scenario is improbable in natural circumstances since the existence of this complex seasonal rarely exceeds 1.5 months.

Modeling of Photosynthesis Process and Assessing Of Phytoplankton Dynamics Based On Droop Model

“…Выбор параметров для расчетов осуществлялся на основе литературных данных, приводимых в [19][20][21]. Упомянутые в работах данные преобразованы с расчетом временного шага, равного одному часу.…”

“…Из параметров модели самыми слабо определяемыми, «уязвимыми», оказываются параметры , , . Из экспериментально определяемых самым «чувствительным» оказывается нижняя граница Q0 для внутриклеточной квоты биогенов q [19]. Численный анализ показывает, что параметры  и  не влияют на свойства устойчивости, а ключевыми оказываются параметры  и Q0.…”

A plankton community: a zooplankton effect in phytoplankton dynamics

“…Существенное влияние на развитие фитопланктона оказывает зоопланктон, для которого фитопланктон является пищей. С другой стороны, рост биомассы фитопланктона определяется рядом иных факторов абиотической природы, в частности внутривидовой конкуренцией за ресурсы [Silkin et al, 2016]. Некоторые примеры зависимости скорости роста фитопланктона от обилия ресурсов и освещенности представлены в монографии [Митчел, 1976].…”

“…Эти изменения не сильно различаются для разных видов. Мы предполагаем, что изменение плотности фитопланктонного сообщества можно описать моделью Рикера, позволяющей учитывать процессы саморегуляции [Митчел, 1976;Silkin et al, 2016;Chattopadhyay et al, 2002;Жданова, Абакумов, 2015]. Также явно учитывается убыль фитопланктона в результате выедания зоопланктоном.…”

Numerical Simulation on the Diffusion of Alien Phytoplankton in Bohai Bay

“…At present, most studies on alien phytoplankton in the world stay on their own biological characteristics (Goes et al, 2013;Cristian et al, 2016;Silkin et al, 2016;Belyaeva, 2019), and there are few studies on their transport and diffusion under the influence of hydrodynamic conditions; the relevant studies on phytoplankton in Bohai Bay are also based on the research of Chinese scholars.…”