Reproduction Of Algae Research Articles

Comparative Aspects on the Metallic and Organic Contaminants Content of the Red Alga Pyropia Leucosticta (Thuret) Neefus & J. Brodie, 2011 Obtained under Laboratory-Controlled Conditions and Natural Environment

"Macroalgal cultures, a new domain for the Romanian Black Sea coast, provide interesting information on the intermediate stages of development and reproduction of algae, and also raw algal material with exploitable potential in most of diverse fields (industrial, cosmetic, pharmaceutical). Porphyra and Pyropia species are considered the world most valuable mariculture algal products. The aim of the paper was to present the comparative aspects regarding the chemical composition (heavy metals, lipids and organic contaminants, respectively, polycyclic aromatic hydrocarbons, organochlorine pesticides and polychlorinated biphenyls) of the specimens obtained in laboratory culture with those collected from the natural environment. The analyzed biological material consisted of P. leucosticta tissue harvested from both laboratory culture and natural environment. After 5 months of experimental culture, the obtained wet biomass was 44.23 g, while the lyophilization dried biomass was 4.94 g. In the specimens obtained through reproductive elements manipulation, under laboratory-controlled conditions, 7 organic compounds were detected, which represent a much smaller number compared with the 20 compounds detected in specimens collected from natural environment. Meanwhile, the presence of all chlorinated organic pollutants was identified in the algal material collected from natural environment. Also, the lipids content was higher in cultured organisms. Heavy metal concentrations (20.72 - 31.91 µg/g d.w. Cu; 0.01-0.21 µg/g d.w. Cd; 12.14-18.69 µg/g d.w. Ni; 0.01-9.56 µg/g d.w. Cr) were comparable with the ranges reported for various macroalgae species from Black Sea region. Key-Words: macroalgae culture, chemical composition, organic contaminants, heavy metals "

Seasonal Variations in Nitrogen and Phosphorus Concentration and Stoichiometry of Hanfeng Lake in the Three Gorges Reservoir Area

Based on the seasonal changes in the nitrogen and phosphorus concentrations in Hanfeng Lake from March 2017 to February 2018, the nutrient limitation status was evaluated by the stoichiometric molar ratio of nitrogen and phosphorus. The results showed that the average concentrations of TN, DN, and NO3--N were 1.60, 1.25, and 0.91 mg·L-1 in Hanfeng Lake, respectively. The seasonal changes of those indicators were similar, showing the highest concentration in winter and lowest in summer. NO3--N accounted for TN significantly in the water body, and the concentrations of NH4+-N and NO2--N remained at low levels and changed steadily. The average concentrations of TP, DP, and PO43--P were 0.13, 0.09, and 0.06 mg·L-1, respectively. The changes in the concentrations of TP and DP were similar, showing a trend of increasing in spring and summer, and then decreasing in autumn and winter, while the PO43--P concentration showed the trend of fluctuated decrease. TN/TP varied from 11.07 to 56.02, with an average value of 29.23. TN/TP changed seasonally, with the highest value occurring in winter and the lowest value in summer. The conditions of the water body were conducive to growth and reproduction of algae for most of the time during sampling months. The water body was occasionally nitrogen limited and rarely phosphorus limited. The seasonal variation in TN/TP ratio was affected by several factors such as rainfall runoff, fertilizer use, sewage discharge, and aquatic biological activities. Further, protection strategies were proposed for the improvement of the water body in terms of present water quality characteristics in Hanfeng Lake.

Impact of the Paleoclimate, Paleoenvironment, and Algae Bloom: Organic Matter Accumulation in the Lacustrine Lucaogou Formation of Jimsar Sag, Junggar Basin, NW China

Shale oil exploration has been a key area of onshore oil and gas exploration in China in recent years. In this study, organic geochemistry and element geochemistry are united to study the shale oil and source rock in the Lucaogou formation of Jimusar sag, in order to reveal the paleoclimate, paleoenvironment, source of organic matter, and factors affecting organic matter accumulation and shale oil generation. The shale oil in the study area is mainly accumulated in two strata with good reservoir properties and oiliness, known as the upper sweet spot and lower sweet spot. Indexes of biomarkers and sensitive elements revealed the warm and semi-arid paleoclimate during Lucaogou formation, and the water column was brackish to salty. Water stratification caused a suboxic to anoxic environment in the deep-water column and coincided with the anoxic photic zone phenomenon. Compared with the lower sweet spot, the more humid climate, deeper and fresher water, and stronger water stratification characterize the upper sweet spot during sedimentation. This made the photic zone with freshwater more suitable for the reproduction of algae in the upper sweet spot. Meanwhile, the organic matter was well-preserved in the anoxic zone. Volcanic ash caused algae bloom, which promoted primary productivity and ensured the supply of organic matter. The composition and distribution pattern of biomarkers prove that phytoplankton is the most important source of organic matter in the study area and the contribution of higher plants is insignificant. The relationship between parameters of paleoproductivity and the redox condition versus total organic carbon (TOC) suggests that compared with the preservation conditions, the input of organic carbon is the most important controlling factor of organic matter accumulation in the study area.

Hypochlorite and visible-light irradiation affect the transformation and toxicity of graphene oxide

Graphene oxide (GO) that has many advanced properties, has been applied in various fields, such as water treatments and removal of contaminations. Hypochlorite is widely used in water treatments. However, the effects of hypochlorite on the transformations and risks of GO, and the toxicological responses remain largely unknown, especially under visible-light irradiation. The present work found that visible-light irradiation promoted the breakdown of sp2 structures of GO by hypochlorite, producing alkanes and arenes with short carbon skeletons. Compared to oxygen-containing radicals, chlorine-related radicals contributed to the breakdown of carbon atomic rings of GO. Compared to pristine GO, the transformed GO inhibited algal reproduction, reduced photosynthesis, and promoted oxidative stress and membrane permeability. Substantial plasmolysis and increased numbers of starch grains were observed in the exposure groups. Metabolomics analysis found that oxidative stress and increased membrane permeability linked to downregulated proline. The downregulated pathways of alanine, aspartate and glutamate metabolism were associated with the inhibition of algal reproduction. The downregulated pathways related to protein synthesis and the secondary metabolism explained the strong toxicity induced by GO with hypochlorite and visible-light irradiation. The above results provide insight into the safety assessment of GO.

Ecotoxicological effects of atmospheric particulate produced by braking systems on aquatic and edaphic organisms

Vehicles generate particulate matter (PM) in significant amounts as their brake systems wear. These particles can influence air quality and their transport/deposition may affect the edaphic and aquatic ecosystems. As part of the LOWBRASYS H2020 project, new more eco-friendly brake disc and pad formulations were developed. PMs generated from traditional (FM1-BD1) and innovative (FM4-BD2, FMB-BD7) brake systems in bench tests were studied. The PMs’ physical/chemical characteristics were preliminarily investigated. To study the possible environmental impact of the nano-micro particulate, we used a battery of ecotoxicological tests. We employed the microalga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the bacteria Vibrio fischeri as aquatic bioindicators, while for the edaphic ecosystem we used the seeds of Lepidium sativum and Sorghum saccharatum, the nematode Caenorhabditis elegans, the earthworm Eisenia andrei and the ameba Dictyostelium discoideum. The results showed a higher sensitivity of the freshwater organisms exposed to the soluble PM fraction, with respect to the edaphic ones. FM4-BD2 brake formulation was slightly more toxic for algae (200 mg/L) than FM1-BD1 (500 mg/L). The new system FMB-BD7 particulate was not harmful for crustacean survival, and resulted weakly toxic for algal reproduction only at 500 mg/L. The particulate material per se was found to affect the algal reproduction. No toxic effects were found on nematodes, earthworms and seeds up to 1000 mg/L. However, in D. discoideum the reproduction rate was significantly reduced starting from 100 mg/L; and the lysosomal membrane stability showed a relevant alteration also at minimal concentration (0.1 mg/L). The results demonstrated a minimal risk for biodiversity of the particulates from the different brake systems and highlighted a more eco-friendly performance the new brake-pad FMB-BD7. However, the occurrence of sublethal effects should be considered as a possible contribution of the particle toxicity to the biological effects of the environmental pollution.

Pollution Sources and the Stratification Effects on Water Quality in Lijiahe Reservoir

An in-depth understanding of the source of pollutants and the evolution of water quality is a prerequisite for water pollution control in source water reservoirs. Lijiahe Reservoir is an important water source for Xi'an. To strengthen the protection of Lijiahe Reservoir, water quality monitoring was carried out monthly from December 2016 to December 2017. The results showed that the main pollutant source was upstream water, and its percentage contribution to the bulk pollutants was 99.52% for permanganate index, 99.41% for TN, and 99.23% for TP. The main source of pollution in the upstream Dongcaiyu was the upper reach with Gepai Primary School and the turf service area. The main source of pollution in Xicaiyu was the upper reach with a chicken farm and fishery. In summer and autumn, Lijiahe Reservoir exhibited thermal stratification. During the stable stratification period, the maximum concentrations of TN, TP, permanganate index, TOC, Fe, and Mn in the water body were as high as 3.32, 0.177, 5.21, 3.01, 0.21, 0.235 mg·L-1, respectively, under the dual effects of exogenous pollution and bottom anaerobic release. The maximum concentrations of TN, TP, Fe, and Mn exceeded the Class Ⅲ water limit of Surface Water Environmental Quality Standards (GB 3838-2002). The higher nutrient levels promoted large-scale reproduction of algae. The density of algae in the upper water reached 2.18×108 cells·L-1, and the dominant algae species were Microcystis aeruginosa and Aphanizomenon flosaquae, which pose a significant threat to water quality. Therefore, the primary goal for water pollution control in Lijiahe Reservoir is to take effective measures to control algae blooms, and at the same time, reduce the input of upstream pollutants.

Algal Sex Determination and the Evolution of Anisogamy.

Algae are photosynthetic eukaryotes whose taxonomic breadth covers a range of life histories, degrees of cellular and developmental complexity, and diverse patterns of sexual reproduction. These patterns include haploid- and diploid-phase sex determination, isogamous mating systems, and dimorphic sexes. Despite the ubiquity of sexual reproduction in algae, their mating-type-determination and sex-determination mechanisms have been investigated in only a limited number of representatives. These include volvocine green algae, where sexual cycles and sex-determining mechanisms have shed light on the transition from mating types to sexes, and brown algae, which are a model for UV sex chromosome evolution in the context of a complex haplodiplontic life cycle. Recent advances in genomics have aided progress in understanding sexual cycles in less-studied taxa including ulvophyte, charophyte, and prasinophyte green algae, as well as in diatoms.

Gcd Gene Diversity of Quinoprotein Glucose Dehydrogenase in the Sediment of Sancha Lake and Its Response to the Environment.

Quinoprotein glucose dehydrogenase (GDH) is the most important enzyme of inorganic phosphorus-dissolving metabolism, catalyzing the oxidation of glucose to gluconic acid. The insoluble phosphate in the sediment is converted into soluble phosphate, facilitating mass reproduction of algae. Therefore, studying the diversity of gcd genes which encode GDH is beneficial to reveal the microbial group that has a significant influence on the eutrophication of water. Taking the eutrophic Sancha Lake sediments as the research object, we acquired samples from six sites in the spring and autumn. A total of 219,778 high-quality sequences were obtained by DNA extraction of microbial groups in sediments, PCR amplification of the gcd gene, and high-throughput sequencing. Six phyla, nine classes, 15 orders, 29 families, 46 genera, and 610 operational taxonomic units (OTUs) were determined, suggesting the high genetic diversity of gcd. Gcd genes came mainly from the genera of Rhizobium (1.63–77.99%), Ensifer (0.13–56.95%), Shinella (0.32–25.49%), and Sinorhizobium (0.16–11.88%) in the phylum of Proteobacteria (25.10–98.85%). The abundance of these dominant gcd-harboring bacteria was higher in the spring than in autumn, suggesting that they have an important effect on the eutrophication of the Sancha Lake. The alpha and beta diversity of gcd genes presented spatial and temporal differences due to different sampling site types and sampling seasons. Pearson correlation analysis and canonical correlation analysis (CCA) showed that the diversity and abundance of gcd genes were significantly correlated with environmental factors such as dissolved oxygen (DO), phosphorus hydrochloride (HCl–P), and dissolved total phosphorus (DTP). OTU composition was significantly correlated with DO, total organic carbon (TOC), and DTP. GDH encoded by gcd genes transformed insoluble phosphate into dissolved phosphate, resulting in the eutrophication of Sancha Lake. The results suggest that gcd genes encoding GDH may play an important role in lake eutrophication.

Regulation of phosphate uptake kinetics in the bloom-forming dinoflagellates prorocentrum donghaiense with emphasis on two-stage dynamic process

Phosphorus is an essential element for the growth and reproduction of algae. In recent years, the frequent outbreaks of algal blooms caused by eutrophication have drawn much attention to the influence of phosphate (P) uptake on the growth of algal cells. The previous study only considered the effect of total P pools on the P uptake process of algal cells and considered the process as one stage, which is insufficient. P uptake by algae is actually a two-stage kinetic process because in many algae species, surface-adsorbed P pools account for a large proportion of total P pools. In this paper, we fit one-stage and two-stage models of P uptake by algae to our experimental data on short-term uptake kinetics of algae Prorocentrum donghaiense under P-deplete and P-replete conditions at 24°C. According to the experimental results, P. donghaiense possesses different P uptake characteristics under different P concentrations. P. donghaiense grows faster and exponentially for longer periods of time under P-replete condition. Ranges of change of Qc (cell quota of intracellular P) and Sp (cell quota of surface-adsorbed P) during the culture time are obviously larger under P-replete condition than those under P-deplete condition. The value of Kp (represents the impact of P-starvation on P uptake rate) in one-stage model under P-deplete condition is smaller than that under P-replete condition, which is opposite to results of two-stage model and does not meet the actual biological significance of Kp. The two-stage model gives more reasonable and realistic explanations to the process of P uptake by algae no matter from the perspective of intuitive fitting effect, biological significance of parameters, statistical test results or essential dynamic process. These results, combined with long-term lab and field data in ocean, could be used to effectively predict algal blooms.

Research advance in allelopathy effect and mechanism of terrestrial plants in inhibition of Microcystis aeruginosa.

The inhibition of algae reproduction and control of harmful algal bloom are the primary challenges in the ecological restoration of eutrophicated water. It is urgent to inhibit algae over-reproduction in green and effective ways, one of which is the use of plant allelopathic effect. How-ever, few study focused on allelochemicals of terrestrial plants. Here, we introduced inhibition of Microcystis aeruginosa over-reproduction by allelochemicals from three categories of terrestrial plants, including herbaceous plants (Compositae/Papaveraceae, Liliaceae, Graminaceae), woody plants, and Chinese medicine plants. The classification, separation and identification of alleloche-micals from terrestrial plants that could be used for the inhibition of M. aeruginosa were summarized. Finally, the allelopathic mechanism to inhibit M. aeruginosa was discussed in detail to support the development of algistat. We also proposed some suggestions for the further development of algistat.

Effect of the Rainfall on Extinction of Cyanobacteria Bloom and Its Mechanism Analysis

There were three rainfall events with different intensity in the Xiangxi Bay (XXB) from May 24 to June 2 in 2016. The factors such as hydrodynamics, water temperature, optical properties, and chlorophyll a concentrations during the rainfall events were analyzed. During the May 27 moderate rain period, the upstream flow of the reservoir bay increased by 1.9 times and the average mixing layer depth in the whole reservoir increased 8.2 m, compared to those before the rainfall event. During the June 1 light rain period, the average mixing layer depth in the whole reservoir increased 1.6 m and the average chlorophyll concentration reduced 2.02 μg·L-1, compared with those before the rainfall event. During the June 2 heavy rain period, the upstream flow of the reservoir bay increased by 4 times, the average mixing layer depth in the whole reservoir increased 7.9 m and the average chlorophyll concentration reduced 14.64 μg·L-1, compared with those before the rainfall event. The algae moved from the upstream to the downstream with water that reduced the concentration of algae in the XXB. The water temperature stratification weakened during the rain event and the average mixing layer depth in the whole reservoir increased, destroying the algal growth environment. After the rainfall, under suitable light and temperature conditions for 2-3 d, the water temperature stratification of the reservoir was recovered and rapid growth and reproduction of algae occurred. As a result, the chlorophyll concentrations in the reservoir increased. Rainfall has a periodic inhibitory effect on the outbreak of algal blooms; however, it cannot fundamentally solve the problem of tribal bay blooms.

Elevated atmospheric CO2 enhances grazer‐induced morphological defense in the freshwater green alga Scenedesmus obliquus

AbstractAtmospheric CO2 level is increasing and considerably influences aquatic ecosystems. Grazer‐induced defenses in phytoplankton stabilize the structures of aquatic food webs. Costs associated with defense have resulted in a situation in which the effectiveness of inducible defenses depends on environmental conditions. To investigate the grazer‐induced defense responses to elevated air CO2 levels, the algae Scenedesmus obliquus was cultured under two air CO2 concentrations (390 ppm and 750 ppm) in the absence or presence of predator‐derived cues (Daphnia filtrate). In response to Daphnia filtrate, colonial populations such as eight‐celled colony were largely formed in S. obliquus. When air CO2 was elevated to 750 ppm, the inorganic carbon contents in media increased, thereby stimulating algal reproduction and photosynthesis. Moreover, the volumes of unicells and two‐celled colonies were enlarged under elevated CO2 conditions. These physiological changes satisfied the material and energy demands for the formation of larger colonies. Based on the consistent surface area per volume of the large colony under ambient and elevated CO2 conditions, the increased inorganic carbon (by CO2 enrichment) facilitated the carbon uptake of the multi‐celled colony. Thus, the morphological defense in phytoplankton was enhanced with more eight‐celled colonies formed in populations grown in a high‐CO2 environment. The present result verified the hypothesis that inducible defense is less costly and has higher effectiveness with increasing carbon availability. The enhancement of anti‐grazer morphological defenses in phytoplankton potentially alters the trophic cascades between phytoplankton and zooplankton and contributes to the redirected energy and nutrient flow in ecosystem‐level processes under a CO2‐rising climate.

Aqueously Released Graphene Oxide Embedded in Epoxy Resin Exhibits Different Characteristics and Phytotoxicity of Chlorella vulgaris from the Pristine Form

The environmental release of nanoparticles is attracting increasing attention. Graphene oxide (GO) embedded in epoxy resin (ER) is a popular composite that has been used in various fields, but the environmental release of GO-ER composites and the effects on organisms in the environment remain unknown. The present work found that GO-ER composites in water for 2-7 days resulted in the release of 0.3-2.1% GO-ER at nanoscale (2-3 nm thickness and approximately 70-130 nm lateral length). Interestingly, pristine GO quenched 30-45% hydroxyl and 12% nitroxide free radicals, whereas this capacity was not observed for the released particles from GO-ER. At environmentally relevant concentrations (μg/L), released GO-ER particles, but not GO or ER matrix, promoted algal reproduction by 34% and chlorophyll biosynthesis by 65-127% at 96 h. Released GO-ER entered algal cells and induced a slight increase in reactive oxygen species but did not elicit notable cell structure damage. The upregulated amino acids and phenylalanine metabolism, and the downregulated fatty acid biosynthesis contributed to algal growth promoted by released GO-ER. Previous studies of pristine nanoparticles were unable to reflect the environmental effects of released nanoparticles into the environment, and our research on the exposure-toxicological continuum adds important contributions to this field.

Study on method and mechanism of deep well circulation for the growth control of Microcystis in aquaculture pond.

In order to control the growth of Microcystis in aquaculture ponds and reduce its adverse effect on water quality and aquaculture, a production-scale experiment of deep well circulation treatment was carried out in an aquaculture pond with water surface area of 63,000 m2 and water depth of 1.6-2.0 m. Compared with the control pond, the experiment pond had better water quality as indicated by 64.2% reduction in chlorophyll a, and 81.1% reduction in algal cells. The chemical oxygen demand, total nitrogen, and total phosphorus concentration were reduced by 55.1%, 57.5%, and 50.8%, respectively. The treatment efficiency is mainly due to the growth control of Microcystis (i.e. cell reduction of 96.4%). The gas vesicles collapsing because of the water pressure was suggested to be the mechanism for Microcystis suppression by the deep well circulation treatment. The Microcystis lost its buoyancy after gas vesicles collapsed and it settled to the bottom of the aquaculture pond. As a result, the algae reproduction was suppressed because algae could only grow in the area with enough sunlight (i.e. water depth less than 1 m).

Effect of salinity on vegetative growth and sexual reproduction of algae from the genus Ardissonea de Notaris (Bacillariophyta)

Effect of salinity on vegetative growth and sexual reproduction was investigated in laboratory cultures of a benthic diatom Ardissonea crystallina (C. Agardh) Grunow from the Black Sea and vegetative growth of Ardissonea sp. from the coast of Martinique, the Atlantic Ocean. Typical water salinity in the places where the populations inhabit differs two times. It was shown that the clones of both populations have a broad tolerance and great ability to adapt to changes in salinity. Cells of different size (i.e., in different stages of the life cycle) responded differently to desalination. Salinities optimal for vegetative growth of these species were not the same. Ardissonea from the coast of Martinique was more sensitive to low levels of salinity as compared with A. crystallina from the Black Sea. It was surprising that salinity optimal for vegetative growth and sexual reproduction of the Black Sea species did not coincide with the real salinity level of the Black Sea. Position of physiological optimums indicates an oceanic (or Mediterranean) origin of the Black Sea population of A. crystallina.

Effects of Fe 2+ and Fe 3+ on Algal Proliferation in a Natural Mixed Algal Colony in Algae-Rich Raw Water in Southern China

As a necessary micronutrient for algal growth, iron (Fe) has importanteffects on the physiological metabolism and enzymatic reactions of algae. There arevarious forms of iron in nature, and soluble iron exists mainly in two forms: Fe2+ andFe3+. In this study, a series of experiments were designed to compare the effects ofFe2+ and Fe3+ on the growth of natural mixed algal colonies and single-species coloniesof Scenedesmus quadricauda. The results show that Fe2+ and Fe3+ have different effectson the reproductive processes of these two algal populations. The optimal growthconcentration of both Fe2+ and Fe3+ for natural mixed algae is 0.3 mg/L; at that concentration,algal biomass reaches its peak, with values of 1.74 × 106 cells/L and 6.82× 105 cells/L for the two iron forms, respectively. At the same time, the average growthrates of these algae also reach their maximum, which are 0.3620 d–1 and 0.3398 d–1,respectively. The optimal growth concentrations of Fe2+ and Fe3+ for S. quadricaudaare about 0.4 mg/L. We propose that Fe2+ exhibits higher biological time-effectivenessthan Fe3+ for algal reproduction, and while Fe2+ and Fe3+ exhibit similar facilitation in thegrowth of both natural mixed algae and S. quadricauda, differences exist between theirfacilitation effects. The results of the study further suggest that problems involving ironuptake priority and inter-specific competition could arise during the reproductive processin mixed algal colonies.

Multiple stressor effects in Chlamydomonas reinhardtii – Toward understanding mechanisms of interaction between effects of ultraviolet radiation and chemical pollutants

The effects of chemical pollutants and environmental stressors, such as ultraviolet radiation (UVR), can interact when organisms are simultaneously exposed, resulting in higher (synergistic) or lower (antagonistic) multiple stressor effects than expected based on the effects of single stressors. Current understanding of interactive effects is limited due to a lack of mechanism-based multiple stressor studies. It has been hypothesized that effect interactions may generally occur if chemical and non-chemical stressors cause similar physiological effects in the organism. To test this hypothesis, we exposed the model green alga Chlamydomonas reinhardtii to combinations of UVR and single chemicals displaying modes of action (MOA) similar or dissimilar to the impact of UVR on photosynthesis. Stressor interactions were analyzed based on the independent action model. Effect interactions were found to depend on the MOA of the chemicals, and also on their concentrations, the exposure time and the measured endpoint. Indeed, only chemicals assumed to cause effects on photosynthesis similar to UVR showed interactions with UVR on photosynthetic yield: synergistic in case of Cd(II) and paraquat and antagonistic in case of diuron. No interaction on photosynthesis was observed for S-metolachlor, which acts dissimilarly to UVR. However, combined effects of S-metolachlor and UVR on algal reproduction were synergistic, highlighting the importance of considering additional MOA of UVR. Possible mechanisms of stressor effect interactions are discussed.

Pheromone signaling during sexual reproduction in algae

Algae are found in all aquatic and many terrestrial habitats. They are dominant in phytoplankton and biofilms thereby contributing massively to global primary production. Since algae comprise photosynthetic representatives of the various protoctist groups their physiology and appearance is highly diverse. This diversity is also mirrored in their characteristic life cycles that exhibit various facets of ploidy and duration of the asexual phase as well as gamete morphology. Nevertheless, sexual reproduction in unicellular and colonial algae usually has as common motive that two specialized, sexually compatible haploid gametes establish physical contact and fuse. To guarantee mating success, processes during sexual reproduction are highly synchronized and regulated. This review focuses on sex pheromones of algae that play a key role in these processes. Especially, the diversity of sexual strategies as well as of the compounds involved are the focus of this contribution. Discoveries connected to algal pheromone chemistry shed light on the role of key evolutionary processes, including endosymbiotic events and lateral gene transfer, speciation and adaptation at all phylogenetic levels. But progress in this field might also in the future provide valid tools for the manipulation of aquaculture and environmental processes.

Effects of Water Flow on Growth of the <i>Microcystis aeruginosa</i> in early Summer and Autumn

The experiment was conducted by small perspex ring groove, which generated infinitely long water flow, under axenic condition and constant temperature and light, to understand the effects of water flow onMicrocystis aeruginosagrowth in early summer and autumn raw water. The results showed that the algae growth was promoted and the specific growth rate was accelerated by water flow. The maximum biomass ofM. aeruginosain autumn raw water was higher than in early summer raw water at every flow rate. The optimum flow rate ofM. aeruginosain early summer and autumn raw water were 25 cm·s-1and 35cm·s-1, respectively. The phenomenon may be the interaction of the colloid produced by death and decomposition of algae, and colony formation inM. aeruginosaunder fluid motion. Therefore, The decomposition and morphology ofMicrocystishave an important role to growth and reproduction of algae, the results provided the scientific basis for revealing algal blooms.

Modeling the spring blooms of ciliates in a deep lake

In contrast to the macro/mesozooplankton, microzooplankton has received much less attention in ecosystem models. In many modeling studies, microzooplankton has been either entirely neglected, or else, data were often not available for validation, or agreement between the observed and the simulated abundances was rather poor. In this study, we compare the simulation results from several alternative models considering different formulations of ciliate growth in a hydrodynamically driven 1D nutrient-phytoplankton–multiple zooplankton model, with long-term datasets from the deep, monomictic Lake Constance. We show that the parameterization of the limitation of ciliate growth with a constant specific mortality rate and/or predation by copepods leads to uncontrolled ciliate blooms. In contrast, implementation of a density-dependent mortality rate enables reproduction of algae–ciliate dynamics over a variety of environmental settings encompassed by the 14-year dataset spanning 21 years in a lake undergoing oligotrophication. Considering the numerous processes that can be responsible for the dampening of ciliate blooms, our findings suggest that employing a simple density-dependent mortality term offers a pragmatic solution for the challenge of including the microzooplankton, characterized by an overwhelming complexity of trophic interactions, in ecosystem models.