Development Of Phytoplankton Community Research Articles

Development of phytoplankton communities in various ecotopes of the Sumka River (Republic of Tatarstan, Russia)

In summer, phytoplankton community of the small river Sumka located in the Republic of Tatarstan Russia, comprised 119 alga taxa, with a rank below the genus. Chlorophyta were the most diverse group. There were no significant differences in the structure of microalgae communities in different ecotopes of the small river; Sørensen similarity index was 67%. The dominant complex of algal species was mainly represented by Cyanophyta, belonging to the M- and H1-types. However, in August, the dominant complex included the S1-type representatives. The degree of organic pollution of the watercourse may be estimated as transitional from oligo- to mezotrophic type considering the phytoplankton biomass and the composition of the dominant complex of algal species.

Interactions between suspended particulate matter and algal cells contributed to the reconstruction of phytoplankton communities in turbulent waters

The effect of turbulence on phytoplankton growth has been widely studied; however, its effects with respects to suspended particulate matter (SPM) on the development of phytoplankton communities and the behavioral responses of phytoplankton to turbulence and SPM are poorly understood. Here, an approximately homogeneous turbulence simulation system (AHTS, mainly consisting of an oscillating-grid apparatus) was established to gain insight into the mechanisms underlying phytoplankton community responses in turbid, well-mixed waters. The results revealed that maintaining the turbulence dissipation rates (Ɛ) of 2.25 × 10−3 and 1.80 × 10−2 m2/s3 caused significant reductions in algal density, and the effects could be substantially enhanced when 500 mg/L of SPM were added before day 12. In contrast to the constant decrease of algal density for the Ɛ of 2.25 × 10−3 m2/s3, a dramatic increase in the phytoplankton density occurred after 16 days of incubation for a Ɛ of 1.80 × 10−2 m2/s3, irrespective of SPM. Addition of SPM in the Ɛ of 1.80 × 10−2 m2/s3 treatments did not considerably affect the algal density profile compared to that without SPM, of which unicellular algae decreased and colonial algae dominated the phytoplankton community. On the other hand, the phytoplankton can regulate the SPM properties. During the 18 days’ coincubation, extracellular polymeric substances (EPS) released from algal cells induced larger particle sizes and round surfaces of SPM, which can reduce the damage received to algal cells. Here we demonstrated that the phytoplankton communities could actively counteract the effects of turbulence + SPM and adapt the couple stress, jointly through the release of EPS, the modification of SPM surface properties and the conversion of their assemblage pattern, thereby contributing to rebalance the ecosystem. These findings highlight the strategies employed during the reconstruction of phytoplankton under the dual effects of turbulence and SPM for the first time, consequently enabling the forecasting of the dominant species of phytoplankton in turbulent waters.

Development of phytoplankton communities: Implications of nutrient injections on phytoplankton composition, pH and ecosystem production

The development of a marine phytoplankton community was studied in a series of mesocosm tanks exposed to different levels of nutrient inputs. Key ecosystem variables such as phytoplankton species development, ecosystem net production (NEP), pH and bacteria production were measured. The overall aim was to mimic the consequences of extreme weather events by applying nutrients in either repeated (pulse treatment) versus a single inputs (full treatment). Regardless of treatment type, pH increased steadily, until nutrients became exhausted. During the experiment, potentially nuisance dinoflagellates developed and became dominant whereas diatoms became rare as compared to the parallel controls. At pH>9, a shift from the presence of the potential nuisance Alexandrium pseudogonyaulax towards high pH tolerant Prorocentrum species was observed. Diatoms disappeared when A. pseudogonyaulax became dominant. The NEP was significantly higher (ca. 2500μg CL−1d−1) in the nutrient amended tanks than in the control tanks (ca. 500μg CL−1d−1). NEP dropped substantially as nutrients became depleted whereas bacterial communities maintained a high production likely driven by easy access to carbohydrates, turning the ecosystem net heterotrophic. This study suggests that a single nutrient dose drives pH higher than multiple smaller nutrient doses injected albeit the total amount of nutrient injected to the treatments was similar. Such changes affect pH, species composition and rates of pelagic production ultimately uncoupling high bacterial production from primary production, leading to severe oxygen consumption following ephemeral blooms.

Dynamics of extracellular enzyme activities in seawater under changed atmospheric pCO2: a mesocosm investigation

As part of the PeECE II mesocosm project, we investigated the effects of pCO2 levels on the initial step of heterotrophic carbon cycling in the surface ocean. The activities of microbial extracellular enzymes hydrolyzing 4 polysaccharides were measured during the development of a natural phytoplankton bloom under pCO2 conditions representing glacial (190 µatm) and future (750 µatm) atmospheric pCO2. We observed that (1) chondroitin hydrolysis was variable throughout the pre-, early- and late-bloom phases, (2) fucoidanase activity was measurable only in the glacial mesocosm as the bloom developed, (3) laminarinase activity was low and constant, and (4) xylanase activity declined as the bloom progressed. Concurrent measurements of microbial community composition, using denaturing-gradient gel electrophoresis (DGGE), showed that the 2 mesocosms diverged temporally, and from one another, especially in the late-bloom phase. Enzyme activities correlated with bloom phase and pCO2, suggesting functional as well as compositional changes in microbial communities in the different pCO2 environments. These changes, however, may be a response to temporal changes in the development of phytoplankton communities that differed with the pCO2 environment. We hypothesize that the phytoplankton communities produced dissolved organic carbon (DOC) differing in composition, a hypothesis supported by changing amino acid composition of the DOC, and that enzyme activities responded to changes in substrates. Enzyme activities observed under different pCO2 conditions likely reflect both genetic and population-level responses to changes occurring among multiple components of the microbial loop.

Development of phytoplankton communities and common off-flavors in a biofloc technology system used for the culture of channel catfish (Ictalurus punctatus)

The use of biofloc technology production systems continues to increase in the aquaculture industry worldwide. Recent research demonstrated that outdoor biofloc systems can be used to produce high yields of channel catfish (Ictalurus punctatus). However, studies have not yet been performed to determine the development and composition of phytoplankton communities and related off-flavor problems in these biofloc production systems. In this study, water samples were collected biweekly from May to November and channel catfish samples were collected during harvest in November from nine 18.6m2 biofloc culture tanks. Water and fillet samples were analyzed for levels of the common off-flavor compounds geosmin and 2-methylisoborneol (MIB). The development and composition of phytoplankton communities in each culture tank was also monitored. In addition, water and biofloc samples were evaluated to assess the microbial sources of geosmin and MIB within the culture tanks. Phytoplankton (including algae and cyanobacteria attached to bioflocs) biomass, as determined by concentrations of chlorophyll a in the water, gradually increased in all tanks over time. Phytoplankton communities that developed in the culture tanks were dominated by fast-growing, unicellular and small colonial types of green algae (chlorophytes) and diatoms (bacillariophytes) and slower growing, small colonial types of cyanobacteria (cyanophytes). A positive correlation (p<0.05) between cumulative feed addition and chlorophyll a concentration was found. Although geosmin and MIB were present in the culture water of each tank during most of the study, levels were typically low and only one tank yielded catfish with geosmin and MIB in their flesh at levels high enough to be designated as off-flavor. A positive correlation (p<0.05) between cumulative feed addition and MIB concentrations in the water of culture tanks indicates a greater potential for MIB-related off-flavor problems at high feed application rates. The microbial sources responsible for production of geosmin and MIB in the culture tanks remain unknown.

Impact of ultraviolet-B radiation on the development of phytoplankton communities in the eastern Atlantic sector of the Southern Ocean—results from on-deck model ecosystem experiments

Abstract Two model ecosystem experiments to assess the effects of UVB radiation (UVBR, 280–320 nm) on phytoplankton communities were performed on-deck during the SWEDARP 97/98 expedition to the eastern Atlantic sector of the Southern Ocean in January 1998. The first experiment was run in the Spring Ice Edge, around 60°S, and the second at the Antarctic Polar Front, around 50°S. The duration of the experiments were 12 and 10 days, respectively. Ambient UVBR was modified to three levels (i.e. treatments): NoUVB—shielded from UVBR (mylar foil); AMB—ambient UVBR; UVB+—enhanced UVBR. The development of the phytoplankton communities was followed by measuring primary production and composition of pigments and diatom species. At the start of the first experiment UVB+ had lower primary production per volume, but not when normalised to chlorophyll a. At the end there were no differences between treatments in primary production per volume but there were differences when normalised to chlorophyll a. In addition, a significant increase in the stimulation of primary production for UVB+ when excluding UVBR and in chlorophyll a concentration was found. These changes, together with changes in species composition, are assumed to be the result of an adaptation to the enhanced UVBR. During the second experiment, the effects from changes in UVBR were generally smaller but resembled to some extent the first experiment. The chlorophyll a concentration increased significantly in the UVB+ treatment at the end of the experiment and there was a strong tendency towards a reduction in primary production per chlorophyll a, but not per volume. The results are important when estimating the effects of increased UVBR as they show variability in short-term sensitivity, and also the capacity of phytoplankton communities to adapt to UVBR and retain primary production even in enhanced UVBR.

Competition for nutrients and light among phytoplankton species in a mixed water column: theoretical studies

A brief overview is given of modelling studies that aim to analyse the effects of nutrient and light limitations on the development of phytoplankton communities and lead to a qualitative understanding of the competitive interactions involved.

Competition for nutrients and light among phytoplankton species in a mixed water column: Theoretical studies

A brief overview is given of modelling studies that aim to analyse the effects of nutrient and light limitations on the development of phytoplankton communities and lead to a qualitative understanding of the competitive interactions involved.

Development of phytoplankton community in a restored eutrophic lake — A multivariate analysis

Development of phytoplankton community in a restored eutrophic lake — A multivariate analysis