Seasonal variations in colonization dynamics of periphytic protozoa in coastal waters of the Yellow Sea, northern China

Use of a broad β-diversity for bioassessment of salinity stress on community homogeneity in marine environments

To determine the feasibility of β-diversity measures to evaluate the impact of salinity stress on community homogeneity in marine environments, a 1-month bioassay was conducted using the protozoan assemblage as the test community. The test samples were collected using the slide method in coastal waters of the Yellow Sea, northern China. Five treatments were designed according to a salinity gradient of 9, 19, 29, 39, and 49 PSU. The homogeneity of the test community showed significant variability in both composition and abundance patterns among five treatments. The multivariate dispersion measure on compositional data was linearly associated with the salinity stress compared to those on abundance alone or in combination with occurrence. The traditional β-diversity index represented a different behavior from that of the multivariate dispersion measures. These findings suggest that the composition-based multivariate dispersion may be a useful tool to evaluate the global salinity stress on community homogeneity in marine ecosystems.

Can microplastics variability drive the colonization dynamics of periphytic protozoan fauna in marine environments?

In recent years, microplastics have become a global environmental hot topic of concern. To explore the effects of different concentrations of microplastics on colonization dynamics of periphytic protozoan fauna, a 21-day study was conducted in temperature-controlled circulation systems. Periphytic protozoan communities were used as test organisms and exposed to five concentrations of MPs: 0, 1, 5, 25, and 125 mg l-1, identification and enumeration were conducted on days 3, 5, 7, 10, 14 and 21. The results showed that the colonization dynamics were driven by MPs and significantly shifted at concentrations over 5 mg l-1. However, a notable decline in maximum species richness and abundance was observed in the high concentrations of microplastic, along with significant deviations in colonization patterns from the control group (0 mg l-1). Therefore, it is suggested that the colonization dynamics of periphytic protozoa can serve as a bioindicator for assessing microplastic concentrations in marine environments.

Vertical variations and environmental heterogeneity drove the symphony of periphytic protozoan fauna in marine ecosystems

Periphytic protozoa are esteemed icons of microbial fauna, renowned for their sensitivity and role as robust bioindicators, pivotal for assessing ecosystem stress and anthropogenic impacts on water quality. Despite their significance, research exploring the community dynamics of protozoan fauna across diverse water columns and depths in shallow waters has been notably lacking. This is the first study that examines the symphony of protozoan fauna in different water columns at varying depths (1, 2, 3.5 and 5 m), in South China Sea. Our findings reveal that vertical changes and environmental heterogeneity plays pivotal role in shaping the protozoan community structure, with distinct preferences observed in spirotrichea and phyllopharyngea classes at specific depths. Briefly, diversity metrics (i.e., both alpha and beta) showed significantly steady patterns at 2 m and 3.5 m depths as well as high homogeneity in most of the indices was observed. Co-associations between environmental parameters and protozoan communities demonstrated temperature, dissolved oxygen, salinity, and pH, are significant drivers discriminating species richness and evenness across all water columns. Noteworthy variations of the other environmental parameters such as SiO3-Si, PO4--P, and NO2--N at 1 m and NO3--N, and NH4+-N, at greater depths, signal the crucial role of nutrient dynamics in shaping the protozoan communities. Moreover, highly sensitive species like Anteholosticha pulchara, Apokeronopsis crassa, and Aspidisca steini in varying environmental conditions among vertical columns may serve as eco- indicators of water quality. Collectively, this study contributes a thorough comprehension of the fine-scale structure and dynamics of protozoan fauna within marine ecosystems, providing insightful perspectives for ecological and water quality assessment in ever-changing marine environments.

An approach to evaluating seasonal responses to acute toxicity of antibiotic nitrofurazone on periphytic ciliated protist communities in marine environments

Periphytic protists including ciliates are the primary components of microbial communities in which they play a vital role in the progression of food webs by moving resources from lower to higher trophic levels. However, the toxic effects of veterinary antibiotics on periphytic protists across four seasons are minimally understood. Therefore, in this study, a 1-year survey was conducted with the antibiotic nitrofurazone (NFZ) applied at concentrations of 0.0, 1.5, 3.0, 6.0, and 12.0 mg/L. Samples of protist communities were collected using microscope glass slides during four seasons in the coastal waters of the Yellow Sea, Qingdao, northern China. The abundance of protists dropped with an increase in NFZ concentrations, and almost all species were dead at a concentration of 12.0 mg/L. The 12 h-LC50 values of NFZ for the protist biota were similar among the four seasons, despite significant seasonal variability in the community structure. The present results suggest that the periphytic protist biota may be used as a biomarker for assessing the ecotoxicity of NFZ in marine environments regardless of the year season.

Continuous warming drives the colonization dynamics of periphytic ciliate fauna in marine environments

In order to evaluate the influence of global warming on the ecosystem processes in marine environments, the changes in colonization dynamics of periphytic microbiota were studied using the periphytic ciliate communities as the test organism fauna under a continuous warming gradient of 22℃ (control), 25℃, 28℃, 31℃, and 34 ℃. The results demonstrated that (1) the test ciliate communities generally showed a similar temporal pattern in within the colonization process under the water temperatures from 22 up to 28℃; however, (2) the colonization dynamics were significantly changed, and the fitness of colonization curves to the MacArthur-Wilson model equation was failed under the temperature increased by 6 ℃, and (3) the loading or assimilative capacity of the test aquatic ecosystem was decreased with the increase of water temperature. Therefore, this study suggests that continuous warming may significantly drive the colonization dynamics of periphytic ciliates in marine ecosystems.

Effects of continuous warming on homogeneity of periphytic protozoan fauna in marine ecosystems

As a powerful biological indicator, multivariate dispersion in a community is widely used to evaluate the biological evaluation of environmental heterogeneity. To investigate the effects of persistent warming on microbial fauna in marine environments, the periphytic protozoan communities were used as test organisms and incubated in five temperature-controlled circulation system at 22 (control), 25, 28, 31 and 34 °C, respectively. The results showed that (1) there was a clear variation in species occurrence, and the α-/γ-diversity measures decreased with the increase of temperatures; (2) the compositional pattern was significantly driven by the persistent warming compared to community pattern from species-abundance data; and (3) both traditional β-diversity and multivariate dispersion measures on species compositional matrix were significantly correlative with changes in the temperature. Therefore, it is suggested that continuous temperature fluctuations have a greater impact on homogeneity of species composition of protozoan communities than that of their community structure.

Can salinity variability drive the colonization dynamics of periphytic protozoan fauna in marine environments?

To investigate effects of salinity variability on colonization dynamics of periphytic protozoan fauna, a 21-day study was conducted in temperature-controlled circulation systems (TCCSs). Periphytic protozoan communities were incubated using glass slides as artificial substrata in five TCCS aquaria with a large-scale salinity gradient of 9, 19, 29 (control), 39, and 49 PSU, respectively. The colonization dynamics were observed on days 3, 5, 7, 10, 14, and 21. The colonization dynamics were well fitted to the MacArthur-Wilson and logistic model equations in colonization and growth curves in all five treatments, respectively. However, the maximum species richness and abundance were reduced, and the colonization patterns were significantly shifted in four treatments with salinity changed by 20 PSU compared to the control (29 PSU). Thus, it is suggested that the large-scale salinity variability may reduce the species richness significantly and affect colonization dynamics of periphytic protozoan fauna in marine environments.

Microbial Community Colonization Process Unveiled through eDNA-PFU Technology in Mesocosm Ecosystems

Microbial communities are essential components of aquatic ecosystems and are widely employed for the detection, protection, and restoration of water ecosystems. The polyurethane foam unit (PFU) method, an effective and widely used environmental monitoring technique, has been improved with the eDNA-PFU method, offering efficiency, rapidity, and standardization advantages. This research aimed to explore the colonization process of microbial communities within PFUs using eDNA-PFU technology. To achieve this, we conducted ten-day monitoring and sequencing of microbial communities within PFUs in a stable and controlled artificial aquatic ecosystem, comparing them with water environmental samples (eDNA samples). Results showed 1065 genera in eDNA-PFU and 1059 in eDNA, with eDNA-PFU detecting 99.95% of eDNA-identified species. Additionally, the diversity indices of bacteria and eukaryotes in both methods showed similar trends over time in the colonization process; however, relative abundance differed. We further analyzed the colonization dynamics of microbes in eDNA-PFU and identified four clusters with varying colonization speeds. Notably, we found differences in colonization rates between bacteria and eukaryotes. Furthermore, the Molecular Ecological Networks (MEN) showed that the network in eDNA-PFU was more modular, forming a unique microbial community differentiated from the aquatic environment. In conclusion, this study, using eDNA-PFU, comprehensively explored microbial colonization and interrelationships in a controlled mesocosm system, providing foundational data and reference standards for its application in aquatic ecosystem monitoring and beyond.

Colonization dynamics in body-size spectrum of protozoan periphytons for marine bioassessment using two modified sampling systems

The body-size spectrum of microperiphytons has been proved to be a powerful tool for bioassessment. To explore colonization dynamics in body-size spectrum of periphytic protozoa in two modified sampling systems of both glass slide (mGS) and polyurethane foam unit (mPFU), a 28-day colonization survey was conducted in coastal waters of the Yellow Sea, China. A total of 7 body-size ranks were identified from 62 species, with 7 ranks (60 species) in the mGS and 6 ranks (37 species) in the mPFU system. The stable pattern with similar body-size spectra was found earlier in the mGS system than mPFU system during the colonization period. Both the trajectory and bootstrapped average analyses revealed that the colonization dynamics were significantly different in the body-size spectrum between the two methods. Based on our data, it suggests that the mGS system might be a better choice than the mPFU system for bioassessment in marine ecosystems.

Use of protozoan periphytons for evaluating of environmental heterogeneity in intertidal zones of marine ecosystems

As an important biological indicator, multivariate dispersion in homogeneity of an observed community is a useful parameter for bioassessment of environmental heterogeneity. To identify the influence of tidal events on homogeneity of protozoan periphyton fauna from the highest tideline to the lowest, a 1-month baseline survey was carried out along five tidelines (sites A-E) in an intertidal zone of the Yellow Sea, northern China. There was a significant influence of tidal events on the homogeneity in both compositional and community structure among five tidelines. The β-diversity measures generally decreased from the highest tideline to the lowest. The biodiversity indices of the protozoans dropped sharply from the highest to the middle tidelines, followed by an increase until to the lowest tideline. These findings suggest that the homogeneity of protozoan periphyton in both species composition and relative abundance was significantly shaped by the environmental heterogeneity in intertidal zones of marine ecosystems.

A community-based approach to analyzing the ecotoxicity of nitrofurazone using periphytic protozoa

The ecotoxicity of nitrofurazone was analyzed based on a community-based approach using periphytic protozoa. Median lethal concentrations (LC₅₀) within an exposure time of 30 min were determined by an acute toxicity test at 0, 1.5, 3, 6 and 12 mg ml^-1 nitrofurazone. Toxicity curve tests demonstrated a decreasing trend with increasing exposure time and was well fitted to the toxicity equation LC₅₀ = 32.85e^-0.8143t (t = exposure time; R² = 0.91; P < 0.05). Median inhibition concentrations (IC₅₀) for periphytic protozoan growth rates were obtained by chronic tests at 0, 1, 2, 4 and 8 mg ml^-1 nitrofurazone within 10 days exposure and were well fitted to the equation r_% = 0.3686e^-0.35Cnit (C_nit is the concentration of nitrofurazone; R² = 0.92 and P < 0.05). These findings suggest that the LC₅₀ and IC₅₀ values of nitrofurazone can be predicted for any exposure time using periphytic protozoan communities as a bioassay model.

Taxonomy and Molecular Phylogeny of Two New Species of Prostomatean Ciliates With Establishment of Foissnerophrys gen. n. (Alveolata, Ciliophora)

Prostomatean ciliates play important roles in the flow of material and energy in aquatic microbial food webs, and thus have attracted wide attention for over a century. Their taxonomy and systematics are, however, still poorly understood because of their relatively few taxonomically informative morphological characters. In this study, two new prostomateans, Lagynus binucleatus sp. n. and Foissnerophrys alveolata gen. n., sp. n., collected from a freshwater pool and the intertidal zone of a sandy beach, respectively, in Qingdao, China, are investigated using living observation, protargol staining, and SSU rRNA gene sequencing methods. The genus Lagynus is redefined, and the new species L. binucleatus sp. n. is established based on significant morphological differences with similar forms. Furthermore, a new genus, Foissnerophrys gen. n., is established based on a combination of morphological and molecular data with F. alveaolata sp. n. the type species by monotypy. The identities of intracellular prokaryotes of these two new species are discussed based on fluorescence in situ hybridization (FISH) data and newly obtained 16S rRNA gene sequences.

Insights into β-diversity of periphytic protozoan fauna along the water column of marine ecosystems

It has been increasingly recognized that there is high relevance in determining the β-diversity of communities along an environmental gradient for bioassessment of environmental quality status. To evaluate the vertical variations in β-diversity of periphytic protozoan fauna, in response to environmental heterogeneity in marine ecosystems, a baseline survey was conducted at the four water depths in the coastal waters of the Yellow Sea, northern China. Results demonstrated that (1) the species distribution presented different patterns at four water depths; (2) both compositional and community structure showed a significant vertical variation in multivariate dispersions from surface layer to the deeper layers; and (3) β-diversity measures generally increased from depths of 1 m to 5 m. These findings suggest that the homogeneity in the periphytic communities are of a high variability along the water column of marine ecosystems.

Seasonal variation in biological trait distribution of periphytic protozoa in coastal ecosystem: A baseline study for marine bioassessment

To reveal the seasonal variability in biological trait distribution for monitoring surveys based on periphytic protozoa, a baseline survey was carried out in a coastal region of Yellow Sea, northern China. A total of 40 slide samples were collected in a four season cycle after an exposure time period of 14 days. The results demonstrated that: (1) the community-weighted means (CWM) of algivores with large and medium sizes were high in spring and summer, while bacterivores with small size were high in autumn and winter; (2) there was a significant seasonal variation in the protozoan community functions, especially from spring/summer to autumn and winter; and (3) functional diversity indices generally peaked in spring or summer. Thus, there was a significant seasonal variation in protozoan community functions and this approach may be used to determine an optimal sampling strategy for monitoring programs in marine ecosystems.

Seasonal variability in biological trait pattern of biofilm-dwelling protozoa in colonization surveys for marine bioassessment

Biological trait analysis (BTA) has been proved to be a powerful tool to evaluate marine water quality. The species trait distributions of biofilm-dwelling protozoa were studied in a coastal region of the Yellow Sea, northern China, during a four-season cycle. The BTA demonstrated that: (1) the protozoa showed a significant seasonal variability in biological trait pattern during the colonization process across four seasons; (2) the colonization dynamics in species trait distribution followed different temporal models; (3) the functional dynamics in spring and summer were significantly different from those in autumn and winter (P < 0.05); and (4) functional diversity showed lower values in spring and summer than in autumn and winter. These findings suggest that BTA is subject to a high seasonal variability during colonization surveys when protozoa are used as bioindicators of marine water quality.

Seasonal variability in body-size spectrum of periphytic protozoa during colonization of artificial substrates for marine bioassessment

To identify the seasonal variability of body-size spectrum for monitoring surveys based on periphytic protozoa, a one-year baseline survey was carried out in a coastal region of Yellow Sea, northern China. A total of 240 glass slides were collected after immersion times of 3, 7, 10, 14, 21 and 28 days in a four season cycle, i.e., winter, spring, summer, and autumn. Body-size ranks S2 and S5 dominated the periphytic protozoan communities from the initial stage (from day 3) to the next periods in spring and autumn, while body-size ranks S7, S8 and S4 showed high variety at the equilibrium stages (from day 10) in summer and winter. The expectation analysis revealed that the samples had different patterns of departure from the anticipated body-size spectrum in each season. This study shows that an ideal sampling approach needs to be established when protozoa is used as bioindicators of marine water quality.

Environmental Parameters and Substrate Type Drive Microeukaryotic Community Structure During Short-Term Experimental Colonization in Subtropical Eutrophic Freshwaters

Microeukaryotes are key components of aquatic ecosystems and play crucial roles in aquatic food webs. However, influencing factors and potential assembly mechanisms for microeukaryotic community on biofilms are rarely studied. Here, those of microeukaryotic biofilms in subtropical eutrophic freshwaters were investigated for the first time based on 2,585 operational taxonomic units (OTUs) from 41 samples, across different environmental conditions and substrate types. Following conclusions were drawn: (1) Environmental parameters were more important than substrate types in structuring microeukaryotic community of biofilms in subtropical eutrophic freshwaters. (2) In the fluctuating river, there was a higher diversity of OTUs and less predictability of community composition than in the stable lake. Sessile species were more likely to be enriched on smooth surfaces of glass slides, while both free-swimming and attached organisms occurred within holes inside PFUs (polyurethane foam units). (3) Both species sorting and neutral process were mechanisms for assembly of microeukaryotic biofilms, but their importance varied depending on different habitats and substrates. (4) The effect of species sorting was slightly higher than the neutral process in river biofilms due to stronger environmental filtering. Species sorting was a stronger force structuring communities on glass slides than PFUs with more niche availability. Our study sheds light on assembly mechanisms for microeukaryotic community on different habitat and substrate types, showing that the resulting communities are determined by both sets of variables, in this case primarily habitat type. The balance of neutral process and species sorting differed between habitats, but the high alpha diversity of microeukaryotes in both led to similar sets of lifecycle traits being selected for in each case.