Interspecific competition between Microcystis aeruginosa and Pseudanadaena and their production of T&O compounds

Authors

Kejia Zhang, Renjie Pan, Zhang Luo, Tuqiao Zhang, Jiajia Fan

Microcystis aeruginosa and Pseudanabaena are two common cyanobacterial species/genus and they can occur coincidently in many eutrophic lakes globally. These two cyanobacteria could produce Taste & Odor (T&O) compounds, and their production of T&O compounds might be changed when they are present coincidently. The amounts of T&O compounds and their producers may influence the effectiveness of water treatment processes. Therefore, the mutual interactions between Microcystis aeruginosa (FACHB-905, M) and Pseudanabaena sp. (FACHB-1277, P) on T&O compounds in co-cultures were evaluated in this study. Different initial cell concentrations of M and P, with ratios of M:P = 1:1, M:P = 1:2 and M:P = 2:1 were applied in the co-cultures. The growth of M was enhanced under all of the cyanobacterial cell ratios. The growth of P was enhanced under the ratio of M:P = 1:1, while it was inhibited under the ratios of M:P = 1:2 and M: P = 2:1. In addition, the growth of the two cyanobacteria and their production of β-cyclocitral and 2-methylisoborneol (2-MIB) in the filtrate of P were higher than those in the filtrate of M, which may be attributed to their associated secondary metabolites. The cell integrity and photosynthetic capacity of the two studied cyanobacteria are greatly affected by exposure to β-cyclocitral and 2-MIB. The results showed that β-cyclocitral and 2-MIB had the allelopathic effects on the two cyanobacteria species which might influence the composition of co-existing cyanobacteria and their production of T&O compounds.

Allelopathic activity of the picocyanobacterium Synechococcus sp. on unicellular eukaryote planktonic microalgae

Authors

Sylwia Śliwińska-Wilczewska, Aldo Barreiro Felpeto, Jakub Maculewicz, Amanda Sobczyk, Vitor Vasconcelos and Adam Latała

The production and release of allelopathic compounds is an important adaptation by which some species of cyanobacteria can achieve a competitive advantage over other primary producers. In the present study we tested the allelopathic activity of the picocyanobacterium Synechococcus sp. against the following coexisting unicellular eukaryote microalgae: Porphyridium purpureum, Stichococcus bacillaris, Prymnesium parvum and Nitzschia dissipata. With these species, we covered a wide range of taxonomic groups. We demonstrated that both the addition of Synechococcus sp. cell-free filtrate and coculture inhibited the growth, chlorophyll content and photosynthetic rate of P. purpureum and S. bacillaris. Conversely, P. parvum, a well-known mixotroph, was positively affected by both Synechococcus sp. treatments. In contrast, N. dissipata was not affected by either the picocyanobacterial filtrate or coculture. These results suggest that the negative allelopathic effect is related to a reduction in the photosynthetic rate, and that Synechococcus sp. allelopathy should be taken into account in the interactions between picocyanobacteria and eukaryote competitors coexisting in a planktonic system.

Coastal eutrophication and freshening: Impacts on Pseudo-nitzschia abundance and domoic acid allelopathy

Authors

Elise Van Meerssche, Dianne I. Greenfield, James L. Pinckney

Species of the diatom genus Pseudo-nitzschia can produce domoic acid (DA), a neurotoxin responsible for amnesic shellfish poisoning. This release of DA by toxic Pseudo-nitzschia species in the water column may be a way to help the cells to outcompete other phytoplankton species (i.e. allelopathy). In this study, the influence of salinity and nutrient inputs on the effect of DA on natural phytoplankton community compositions was investigated using bioassays to measure phytoplankton responses to 400 ng DA ml⁻¹. Dissolved DA (dDA) was added to natural phytoplankton assemblages from a low salinity site dominated by river runoff and from a relatively pristine, high salinity site in which nutrients were added simultaneously with dDA. At the low salinity site, the percent inhibition of cryptophytes and diatoms induced by the addition of dDA was negatively correlated with salinity. However, at the high salinity site with nutrients added, no correlation with salinity was observed. This study highlights how environmental factors such as salinity and nutrients can play important roles on toxin allelopathy by alleviating or exacerbating its effect.

Allelopathic and Bloom-Forming Picocyanobacteria in a Changing World

Authors

Sylwia Śliwińska-Wilczewska, Jakub Maculewicz, Aldo Barreiro Felpeto and Adam Latała

Picocyanobacteria are extremely important organisms in the world’s oceans and freshwater ecosystems. They play an essential role in primary production and their domination in phytoplankton biomass is common in both oligotrophic and eutrophic waters. Their role is expected to become even more relevant with the effect of climate change. However, this group of photoautotrophic organisms still remains insufficiently recognized. Only a few works have focused in detail on the occurrence of massive blooms of picocyanobacteria, their toxicity and allelopathic activity. Filling the gap in our knowledge about the mechanisms involved in the proliferation of these organisms could provide a better understanding of aquatic environments. In this review, we gathered and described recent information about allelopathic activity of picocyanobacteria and occurrence of their massive blooms in many aquatic ecosystems. We also examined the relationships between climate change and representative picocyanobacterial genera from freshwater, brackish and marine ecosystems. This work emphasizes the importance of studying the smallest picoplanktonic fractions of cyanobacteria.

Changes of the phytoplankton community as symptoms of deterioration of water quality in a shallow lake

Authors

Ewa Anna Dembowska, Tomasz Mieszczankin, Paweł Napiórkowski

Covering more than 60% of the lake surface, macrophytes determined the taxonomic composition of phytoplankton. We have found numerous indications of ecological deterioration and an increased trophic level year to year: an increased total number of taxa; a significantly increased number of species of Chlorophyta, Bacillariophyceae and Cyanoprokaryota; a decreased number of Chrysophyceae; increased Nygaard index, and high diversity and variability of phytoplankton functional groups. Within 2 years (2002 and 2003) algal biomass doubled: from 3.616 to 7.968 mg l⁻¹. An increased contribution of Chlorococcales and Cyanoprokaryota indicates progressive eutrophication of the lake. The average size of planktonic algae increased, particularly Cyanoprokaryota, where small-celled decreased dramatically and were replaced by large colonies. Cyanoprokaryota remained the dominant group of phytoplankton after 10 years, and the ecosystem of the lake remained in the turbid state. This group of algae had the average biomass 9.734 mg l⁻¹, which constituted almost 92% of the total biomass.

Use of macrophytes allelopathy in the biocontrol of harmful Microcystis aeruginosa blooms

Authors

Zakaria Tazart, Mountasser Douma, Lamiaa Tebaa, Mohammed Loudiki

In recent years macrophytes are considered promising tools in the biocontrol of harmful cyanobacteria blooms (cyanoHABs). In this study, the inhibitory effect of aqueous extracts of Ranunculus aquatilis and Nasturtium officinale on Microcystis aeruginosa growth was assessed via six treatments (0%, 0.1%, 0.25%, 0.50%, 0.75%, and 1% extracts). Chlorophyll a and carotenoid content were analyzed and changes in cells morphological of M. aeruginosa cultures were observed. Also, to reveal potential allelochemical compounds, total phenols (TPs), total flavonoids, and tannins (TTs) were analyzed in both extracts. The obtained results showed that M. aeruginosagrowth was significantly inhibited by R. aquatilis and N. officinale aqueous extracts in a concentration-dependent way. After 8 days of treatment, the highest inhibition rates reached 100% and 75.74% respectively. The Chlorophyll a and carotenoid concentrations were decreased compared to the control group. Colonial and cells morphological changes were observed under treatment group with 1% of aqueous extract accompanied by sedimentation of the cyanobacterial cells. This study shows that M. aeruginosa growth inhibition was induced by the total polyphenol, flavonoids and tannins. It was concluded that theses macrophytes may control the M. aeruginosa and may be useful to control harmful blooms in lake-reservoirs.

Succession and toxicity of Microcystis and Anabaena (Dolichospermum) blooms are controlled by nutrient-dependent allelopathic interactions

Authors

Mathias A. Chia, Jennifer G. Jankowiak, Benjamin J. Kramer, Jennifer A. Goleski, I-Shuo Huang, Paul V. Zimba, Maria do Carmo Bittencourt-Oliveira, Christopher J. Gobler

Microcystis and Anabaena (Dolichospermum) are among the most toxic cyanobacterial genera and often succeed each other during harmful algal blooms. The role allelopathy plays in the succession of these genera is not fully understood. The allelopathic interactions of six strains of Microcystis and Anabaena under different nutrient conditions in co-culture and in culture-filtrate experiments were investigated. Microcystis strains significantly reduced the growth of Anabaena strains in mixed cultures with direct cell-to-cell contact and high nutrient levels. Cell-free filtrate from Microcystis cultures proved equally potent in suppressing the growth of nutrient replete Anabaena cultures while also significantly reducing anatoxin-a production. Allelopathic interactions between Microcystis and Anabaenawere, however, partly dependent on ambient nutrient levels. Anabaena dominated under low N conditions and Microcystis dominated under nutrient replete and low P during which allelochemicals caused the complete suppression of nitrogen fixation by Anabaena and stimulated glutathione S-transferase activity. The microcystin content of Microcystis was lowered with decreasing N and the presence of Anabaena decreased it further under low P and high nutrient conditions. Collectively, these results indicate that strong allelopathic interactions between Microcystis and Anabaena are closely intertwined with the availability of nutrients and that allelopathy may contribute to the succession, nitrogen availability, and toxicity of cyanobacterial blooms.

The effect of epiphytic macroinvertebrates on microbial communities in different types of macrophyte-dominated shallow lakes

Authors

Tomasz Mieczan, Monika Tarkowska-Kukuryk, Diana Ȃrva, Làszló Berzni-Nagy, Zoltan Novak and Csilla Vajda

Complex interactions between epiphytic fauna and microbial food webs in periphyton are vital to the ecosystem ecology of shallow lakes. However, little is known about how different types of macrophyte dominated lakes may influence microbial and metazoan communities. The goal of the present study was to examine the impact of metazoan on microbial food web in three different types of lakes (Stratiotes-dominated, Ceratophyllum-dominated and Potamogeton-dominated). The results of this study suggest a strong correlations between chironomid larvae, small Metazoa and microbial communities in the periphyton of macrophyte-dominated lakes. Weak relations between food web components were found in the Potamogeton-dominated and Ceratophyllum-dominated lakes, where environmental variables explained the bulk of the total variance in periphyton abundance, whereas strong predator-prey relations were noted in the Stratiotes-dominated lake, where environmental variables had a minor role in the total variance in periphyton abundance. Our study contributes to knowledge of the functioning of eutrophic lakes in the current era of increasing eutrophication caused by climate change and human activity.

Allelopathy prevents competitive exclusion and promotes phytoplankton biodiversity

Authors

Aldo Barreiro Felpeto, Shovonlal Roy, Vitor M. Vasconcelos

It has been hypothesized that allelopathy can prevent competitive exclusion and promote phytoplankton diversity in aquatic ecosystems, where numerous species coexist on a limited number of resources. However, experimental proof‐of‐principle is not available to support this hypothesis. Here we present the first experimental evidence to support this hypothesis by demonstrating that allelopathy promotes the coexistence of two phytoplankton species, Ankistrodesmus falcatus and Oscillatoria sp., that compete for a single limiting nutrient. By performing long‐term competition experiments in nitrate‐limited continuous cultures, and by describing the population dynamics using a mechanistic model, we demonstrate that when allelopathy comes into play, one of the following outcomes is possible depending on the relative initial abundances of the species: dominance of the stronger competitor for nitrate (the non‐allelopathic species), oscillatory coexistence, or dominance of the weaker competitor (the allelopathic species). Our model analysis revealed that sustained oscillatory coexistence of the two species would be a common outcome of this experiment. Our study confirms for the first time, based on laboratory experiments combined with mechanistic models, that allelopathy can alter the predicted outcome of inter‐specific competition in a nutrient‐limited environment and increase the potential for the coexistence of more species than resources, thereby contributing to the identification of endogenous mechanisms that explain the extreme diversity of phytoplankton communities.

Effects of Dracontomelon duperreanum Leaf Litter on the Growth and Photosynthesis of Microcystis aeruginosa

Authors

Xiaoxiong Wang, Yim Tong Szeto, Chengchun Jiang, Xiaojun Wang, Yi Tao, Jianguo Tu, Jing Chen

This study investigated the use of Dracontomelon duperreanum leaf litter extract (DDLLE) in inhibiting the growth and photosynthesis of the algae Microcystis aeruginosa. The goal of the study was to evaluate a potential solution for cyanobacterial bloom prevention. M. aeruginosa was exposed to extract concentrations from 0.4 to 2.0 g L⁻¹. Chlorophyll-a (Chl-a) content and photosynthesis levels were assessed using pulse amplitude modulated fluorimetry phytoplankton analyzer. Results suggested that the extract could efficiently suppress M. aeruginosa growth. The content of Chl-a was only 19.0 µg L⁻¹ and achieved 96.0% inhibition rate when exposed to 2.0 g L⁻¹ on day 15. Growth rate in response to different extract concentrations were consistent with changes in the photosynthesis efficiency (alpha), maximal relative electron transport rate and maximal photochemical efficiency of photosystem II (F _v /F_m ). Furthermore, several kinds of volatile chemicals and their concentrations in DDLLE had been identified by GC–MS, which of them play major role to suppress the growth of M. aeruginosa should be further studied.