Effects of epiphytic algae on biomass and physiology of Myriophyllum spicatum L. with the increase of nitrogen and phosphorus availability in the water body

Interspecific Differences in Carbon and Nitrogen Metabolism and Leaf Epiphytic Bacteria among Three Submerged Macrophytes in Response to Elevated Ammonia Nitrogen Concentrations

Submerged macrophytes in eutrophic aquatic environments adapt to changes in ammonia nitrogen (NH4-N) levels by modifying their levels of free amino acids (FAAs) and soluble carbohydrates (SCs). As symbionts of submerged macrophytes, epiphytic bacteria have obvious host specificity. In the present study, the interspecific differences in the FAA and SC contents of Hydrilla verticillata (Linn. f.) Roylep, Vallisneria natans Hara and Chara braunii Gmelin and their leaf epiphytic bacterial communities were assessed in response to increased NH4-N concentrations. The results revealed that the response of the three submerged macrophytes to NH4-N stress involved the consumption of SCs and the production of FAAs. The NH4-N concentration had a greater impact on the variation in the FAA content, whereas the variation in the SC content was primarily influenced by the species. At the phylum level, the relative abundance of Nitrospirota on the leaves exhibited specific differences, with the order H. verticillata > V. natans > C. braunii. The dominant genera of epiphytic bacteria with denitrification effects on V. natans, H. verticillata and C. braunii leaves were Halomonas, Acinetobacter and Bacillus, respectively. When faced with NH4-N stress, the variation in epiphytic bacterial populations associated with ammonia oxidation and denitrification among submerged macrophytes could contribute to their divergent responses to heightened nitrogen levels.

Snail communities increase submerged macrophyte growth by grazing epiphytic algae and phytoplankton in a mesocosm experiment

The relationships between producers (e.g., macrophytes, phytoplankton and epiphytic algae) and snails play an important role in maintaining the function and stability of shallow ecosystems. Complex relationships exist among macrophytes, epiphytic algae, phytoplankton, and snails. We studied the effects of snail communities (consisting of Radix swinhoei, Hippeutis cantori, Bellamya aeruginosa, and Parafossarulus striatulus) on the biomass of phytoplankton and epiphytic algae as well as on the growth of three species of submerged macrophytes (Hydrilla verticillata, Vallisneria natans, and one exotic submerged plant, Elodea nuttallii) in a 90-day outdoor mesocosm experiment conducted on the shore of subtropical Lake Liangzihu, China. A structural equation model showed that the snail communities affected the submerged macrophytes by grazing phytoplankton and epiphytic algae (reduction in phytoplankton Chl-a and epiphytic algal abundance), enhancing the biomass of submerged macrophytes. Highly branched macrophytes with high surfaces and morphologies and many microhabitats supported the most snails and epiphytic algae (the biomass of the snail communities and epiphytic algae on H. verticillata was greater than that on V. natans), and snails preferred to feed on native plants. Competition drove the snails to change their grazing preferences to achieve coexistence.

Nitrate application decreased microbial biodiversity but stimulated denitrifiers in epiphytic biofilms on Ceratophyllum demersum

Among nitrogen species, nitrate is more stable than ammonium and nitrite, and it is an important nitrogenous pollutant in surface water. However, little is known about the characterization of epiphytic microbial communities on submersed macrophytes under nitrate loading. In this study, we investigated the co-occurring pattern and response of bacteria and microeukaryotes in epiphytic biofilms under nitrate loading. Nitrate loading significantly affected bacterial and eukaryotic communities, and turnover played greater contribution to the total dissimilarity than nestedness by partitioning beta-diversity analysis. Cyanobacteria, α-proteobacteria, β-proteobacteria, Actinobacteria, Planctomycetes, Bacteroidetes, and γ-proteobacteria were dominant bacterial phyla/classes. Metazoan (phylum Arthropoda, Rotifera, Gastrotricha, Annelida, and Nematoda) and algae (phylum Bacillariophyta, Chlorophyta, and Streptophyta) were dominated in eukaryotic communities. The abundances of denitrifying bacteria (Rhodobacter, Acinetobacter, Bacillus, Flavobacterium, and Pseudomonas) and genes (nirS, cnorB, and nosZ) increased with nitrate loading. The network analysis showed there were complex interactions among photosynthetic microbes, metazoan, and bacteria (including denitrifiers) that they were potentially interrelated via photosynthesis, predation or feeding. This study provides new perspectives into understanding the factors affecting nitrate removal mechanisms in wetlands with submersed macrophytes.

Biological Characterization of Water in Damietta Branch of the Nile River, Egypt

BACKGROUND AND OBJECTIVE

Damietta branch is one of the two main branches of the Nile River (Egypt), that often inhabited by many aquatic organisms, which affect and reflect its water characteristics. This study examine the relation between submerged macrophytes, their epiphytic microalgae and bacterial communities as well as the variations in their distribution and species composition with respect to season and location.

MATERIALS AND METHODS

Macrophytes, epiphytes and water samples were collected from 5 sites distributed along Damietta branch. Macrophytes, epiphytes and bacterial indicators of pollution were identified using standard methods.

RESULTS

Three submerged macrophytes (Myriophyllum spicatum, Ceratophyllum demersum L. and Potamogeton crispus) and 191 epiphytic algal taxa dominated by 87 Bacillariophyta and 62 Chlorophyta were recorded with significance seasonal and spatial variations. Myriophyllum spicatum was the most frequent macrophyte (p = 100%) and represent about 100, 100, 97.4 and 64.9% kg DW m-2 of the total collected macrophytes biomass during autumn, winter, spring and summer respectively. The relation between some epiphytic algal species and specific macrophytes was evident and the high organic pollution tolerant algal species like, Melosira granulata, Nitzschia palea, Synedra ulna, Oscillatoria limosa, Microcystis aeruginosa were recorded. Results of bacteriological analysis revealed a significance difference in total viable bacterial counts developed on either 22 or 37°C, total coliform, fecal coliform, fecal streptococci and Escherichia coli attributed to the seasons and sites.

CONCLUSION

The results indicated different relations between macrophytes, epiphytes and bacteria, which is a useful biological tool for characterization of water quality in Damietta branch for different purposes.

Effects of Water Quality Adjusted by Submerged Macrophytes on the Richness of the Epiphytic Algal Community

Submerged macrophytes and epiphytic algae play significant roles in the functioning of aquatic ecosystems. Submerged macrophytes can influence the epiphytic algal community by directly or indirectly modifying environmental conditions (nutrients, light, etc.). From December to June of the following year, we investigated the dynamics of the dominant winter species Potamogeton crispus, its epiphytic algae, and water quality parameters in the shallow Liangzi Lake in China. The richness of epiphytic algae had a trend similar to that of P. crispus coverage, which increased in the first four months and then decreased in the following three months. The structural equation model (SEM) showed that P. crispus affected the richness of epiphytic algae by reducing nutrient concentrations (reduction in total organic carbon, total nitrogen and chemical oxygen demand) and enhancing water transparency (reduction in turbidity and total suspend solids) to enhance the richness of epiphytic algae. The results indicated that high amounts of submerged macrophyte cover can increase the richness of the epiphytic algal community by changing water quality.

Seasonal biodiversity and ecological studies on the epiphytic microalgae communities in polluted and unpolluted aquatic ecosystem at Assiut, Egypt

A qualitative and quantitative study on epiphytic microalgae was carried out seasonally from November 2015 to August 2016 to follow up their community structures on aquatic macrophytes related to some physico-chemical properties of two polluted and unpolluted water bodies at Assiut, Egypt. A total of 169 species related to 64 genera of epiphytic microalgae were recorded. The most dominant algal group was Bacillariophyceae (43.2%), followed by Chlorophyceae (34.91%), Cyanophyceae (20.71%) and Euglenophyceae (1.18%). The total number of epiphytic algae fluctuated between 11.1 × 104ind.g-1plant dry wt. on Phragmites australis in summer at Nazlet Abdellah (polluted site) and 10.02 × 107ind.g-1plant dry wt. on Myriophyllum spicatum in winter at El-Wasta (unpolluted site). Some epiphytic microalgae were dominant as Pseudanabaena limnetica, Calothrix braunii, Scenedesmus acutus, and Ulnaria ulna. Others were specific on certain macrophytes as Aphanocapsa thermalis and Ulothrix sp., which grow on Phragmites australis, while Synechocystis minuscula attached itself on Myriophyllum spicatum. Analysis of PERMANOVA showed that the most important factors that induced the variation in epiphytic microalgae were the temporal variation and host plant. Water temperature, pH, nitrate, chloride, phosphate and total dissolved salts were the highest abiotic factors correlated with the variation in composition of epiphytic microalgae.