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Phaeocystis pouchetii is an ecologically important colony-forming marine phytoplankton species in northern hemisphere cold waters. It plays a central role in the processing of biogeochemically important elements in the upper ocean during spring blooms. Here, we report highly significant quantitative relationships among colony size, cell number and particulate carbon and nitrogen contents of field populations of P. pouchetii, which provide the means to quantitatively convert its biological expression into units of biogeochemical significance. Populations were sampled from mesocosms incubated in situ in western Norway and either fertilized with nitrate and phosphate or left unamended. Phaeocystis colony blooms developed in both scenarios, but were much greater in fertilized treatments. Colonies from the latter treatments were larger, contained higher concentrations of cells and more particulate carbon and nitrogen than those in the unfertilized mesocosm. Considering all data, log cell number increased linearly with log colony volume with a slope of 0.54. Log carbon and nitrogen increased with log colony volume, with respective slopes of 0.92 and 1.22, indicating a significant component of non-cellular carbon and nitrogen within the colonies. Carbon and nitrogen contents of colonies were linearly related, and fertilized colonies contained more nitrogen relative to carbon than unfertilized colonies. These equations are particularly applicable to contemporary studies of P. pouchetii because they represent colonies growing in environments that mimic a continuum from natural to eutrophicated ecosystems.

Flagellates of Phaeocystis globosa were observed inside colonies in North Sea samples in 1992. Field data suggest that low phosphate concentrations (less than or equal to0.5 muM) and, as a consequence of sedimentation, a 20- to >100-fold reduction of daily irradiance (to m), (ii) the haploid mesoflagellate (4.2 +/- 0.1 mum), (iii) the diploid macroflagellate (6-7 mum) which is Kornmann's (Kornmann, 1955) 'Makrozoospore', and (iv) the diploid non-flagellate colonial cell (6.1 +/- 0.2 mum). A life cycle for Phaeocystis is presented, and the life-cycle transitions still to be tested are identified.

The objective of the study was to determine the role of microzooplankton in the fate of primary production and progression of the spring phytoplankton bloom in high latitude fjords. The 3 fjords, Balsfjord, Malangen and Ullsfjord (Norway), varied in oceanic influence and in the rate of development of the spring bloom. The abundance of Phaeocystis pouchetii was relatively low in the spring of 1997 compared to previous years, and diatoms dominated the biomass of the phytoplankton assemblage in all 3 fjords. The mean biomass of microzooplankton in the top 20 m averaged 72, 66 and 80 mg C m -3 and values integrated to 170 m averaged 4560, 4450 and 6820 mg C m -2 in Balsfjord, Malangen and Ullsfjord, respectively. The composition of the microzooplankton was consistent among the fjords and over time, with the proportion of biomass split evenly between nanoflagellates, dinoflagellates and ciliates. Grazing rates of the microzooplankton community were measured with the dilution technique. The impact of microzooplankton grazing was similar among the fjords, accounting for on average 68, 63 and 55% of the production of the < 200 µm phytoplankton in Bals- fjord, Malangen and Ullsfjord, respectively. When integrated to 20 m, based on a microzooplankton biomass-specific ingestion rate, microzooplankton grazing accounted for an estimated 12 to 26% of the gross primary production. However, this does not account for the carbon requirements of a sub- stantial proportion of the microzooplankton that occurred below 20 m. Clearance rates by ciliates of nanophytoplankton cells of a similar size to the single cells of P. pouchetii were determined from the uptake rates of fluorescently labelled algae (FLA). Generally, the taxa of ciliates that were found to ingest FLA accounted for ♢ 50% of the abundance of the ciliate population in each fjord. Taxon-spe- cific ciliate clearance rates of FLA in surface waters varied with ciliate size from 5.6 to 1.3 µl cell -1 h -1 . The FLA-consuming ciliate population cleared a total of 27 〈 10 3 to 141 〈 10 3 µl l -1 d -1 in surface waters. The ingestion rates of the FLA-consuming ciliates were equivalent to between 11 and 29% of the total microzooplankton consumption. It is possible that the grazing pressure exerted by the micro- zooplankton on single cells and small colonies was high enough to decrease the overall competitive- ness of the P. pouchetii populations and contribute to their low abundance.

Two cell types of the same clone of Phaeocystis globosa, solitary non-flagellate cells and flagellates, were grown in batch cultures under identical conditions. The non-flagellate cells had a shorter lag phase (1.4 versus 2.8 days) and a higher growth rate (0.72 versus 0.65 day(-1)) than flagellate cells. The flagellates had a longer stationary phase (15.6 versus 9.5 days) and a lower death rate (0.07 versus 0.52 day(-1)) than non-flagellate cells. All differences were statistically significant. Biomass yield did not differ between the two cell types. The short lag phase and high growth rate of non-flagellate cells corresponds to field observations of rapidly developing non-flagellate Phaeocystis blooms that are typically observed in nutrient-rich environments such as temperate seas in spring. The flagellate cell type, with its longer stationary phase and lower death rate than non-flagellate cells, is better equipped for survival in oligotrophic environments. This explains why the flagellates of Phaeocystis are abundant after the spring phytoplankton bloom in temperate seas and in other nutrient-poor environments such as the open ocean.

Phaeocystis pouchetii is an ecologically important colony-forming marine phytoplankton species in northern hemisphere cold waters. It plays a central role in the processing of biogeochemically important elements in the upper ocean during spring blooms. Here, we report highly significant quantitative relationships among colony size, cell number and particulate carbon and nitrogen contents of field populations of P. pouchetii, which provide the means to quantitatively convert its biological expression into units of biogeochemical significance. Populations were sampled from mesocosms incubated in situ in western Norway and either fertilized with nitrate and phosphate or left unamended. Phaeocystis colony blooms developed in both scenarios, but were much greater in fertilized treatments. Colonies from the latter treatments were larger, contained higher concentrations of cells and more particulate carbon and nitrogen than those in the unfertilized mesocosm. Considering all data, log cell number increased linearly with log colony volume with a slope of 0.54. Log carbon and nitrogen increased with log colony volume, with respective slopes of 0.92 and 1.22, indicating a significant component of non-cellular carbon and nitrogen within the colonies. Carbon and nitrogen contents of colonies were linearly related, and fertilized colonies contained more nitrogen relative to carbon than unfertilized colonies. These equations are particularly applicable to contemporary studies of P. pouchetii because they represent colonies growing in environments that mimic a continuum from natural to eutrophicated ecosystems.

Flagellates of Phaeocystis globosa were observed inside colonies in North Sea samples in 1992. Field data suggest that low phosphate concentrations (less than or equal to0.5 muM) and, as a consequence of sedimentation, a 20- to >100-fold reduction of daily irradiance (to m), (ii) the haploid mesoflagellate (4.2 +/- 0.1 mum), (iii) the diploid macroflagellate (6-7 mum) which is Kornmann's (Kornmann, 1955) 'Makrozoospore', and (iv) the diploid non-flagellate colonial cell (6.1 +/- 0.2 mum). A life cycle for Phaeocystis is presented, and the life-cycle transitions still to be tested are identified.

Two cell types of the same clone of Phaeocystis globosa, solitary non-flagellate cells and flagellates, were grown in batch cultures under identical conditions. The non-flagellate cells had a shorter lag phase (1.4 versus 2.8 days) and a higher growth rate (0.72 versus 0.65 day(-1)) than flagellate cells. The flagellates had a longer stationary phase (15.6 versus 9.5 days) and a lower death rate (0.07 versus 0.52 day(-1)) than non-flagellate cells. All differences were statistically significant. Biomass yield did not differ between the two cell types. The short lag phase and high growth rate of non-flagellate cells corresponds to field observations of rapidly developing non-flagellate Phaeocystis blooms that are typically observed in nutrient-rich environments such as temperate seas in spring. The flagellate cell type, with its longer stationary phase and lower death rate than non-flagellate cells, is better equipped for survival in oligotrophic environments. This explains why the flagellates of Phaeocystis are abundant after the spring phytoplankton bloom in temperate seas and in other nutrient-poor environments such as the open ocean.

Two cell types of the same clone of Phaeocystis globosa, solitary non-flagellate cells and flagellates, were grown in batch cultures under identical conditions. The non-flagellate cells had a shorter lag phase (1.4 versus 2.8 days) and a higher growth rate (0.72 versus 0.65 day(-1)) than flagellate cells. The flagellates had a longer stationary phase (15.6 versus 9.5 days) and a lower death rate (0.07 versus 0.52 day(-1)) than non-flagellate cells. All differences were statistically significant. Biomass yield did not differ between the two cell types. The short lag phase and high growth rate of non-flagellate cells corresponds to field observations of rapidly developing non-flagellate Phaeocystis blooms that are typically observed in nutrient-rich environments such as temperate seas in spring. The flagellate cell type, with its longer stationary phase and lower death rate than non-flagellate cells, is better equipped for survival in oligotrophic environments. This explains why the flagellates of Phaeocystis are abundant after the spring phytoplankton bloom in temperate seas and in other nutrient-poor environments such as the open ocean.

Розглядаються логіко-математичні конструкти теоретичної екології. Запропонований принцип переходу від кореляційної до функціональної залежності в екологічних дослідженнях. Виділене місце теореми існування, у математичному її розумінні, в теоретичній екології. Дано логіко-математичне зображення (запис) деяких екологічних законів., Рассматриваются логико-математические конструкции теоретической экологии. Предложен принцип перехода от корреляционной к функциональной зависимости в экологических исследованиях. Выделено место теоремы существования, в математическом ее соображении, в теоретической экологии. Дано логико-математическое изображение (запись) некоторых экологических законов., The paper considers logical and mathematical constituents of theoretical ecology. It also suggests the principle of transition to functional dependence in ecological investigations. The author singles out the disposition of existence theorem in its mathematical comprehension in the theoretical ecology. Logical and mathematical representation of some ecological laws is also given in the paper.