Search Results (13)

Submerged macrophytes play an important role in maintaining the structure and function of shallow lakes. Under eutrophication, the community of submerged macrophytes shows a shift of growth forms from rosette-like to canopy-forming macrophytes and a further decline due to the increasing shading from epiphyton and phytoplankton. However, at the early phase of eutrophication, the population of submerged macrophytes may increase due to increased nutrient availability, and the responses of submerged macrophytes to eutrophication are expected to be growth-form dependent. To explore the direct effects of nutrient enrichment on the submerged macrophytes of both growth forms, we constructed a mesocosm study with rosette-like macrophytes (Vallisneria denseserrulata and V. spinulosa) and canopy-forming macrophytes (Potamogeton lucens and P. wrightii) under two nutrient levels but maintained low phytoplankton and epiphyton biomass. Nutrient enrichment had a positive effect on the plant size for both macrophyte growth forms under low algal shading. Based on the 21 plant traits determined, the same growth form responded similarly to the increase in nutrient availability with few exceptions. Interestingly, increased nutrient levels induced different allocation strategies between canopy-forming (especially for ‘magnopotamid’) and rosette-like submerged macrophytes. The increased nutrients promoted leaf growth in rosette-like macrophytes and ramet production in canopy-forming macrophytes. These results provide a case study on the direct effects of increased nutrient levels on submerged macrophytes during the early phase of eutrophication in shallow lakes. Full article

Cyanobacterial biodiversity and potential toxicity in coastal lagoons have barely been studied despite these transitional water systems being very important in conservation and for the preservation of economic resources. Most of these transitional systems have been affected by eutrophication, and climate change will severely affect them by promoting cyanobacteria growth, especially in Mediterranean areas. This study aims to characterize the diversity of epipelic and epiphytic cyanobacteria species in a Mediterranean coastal lagoon and their potential for toxins production (microcystins and saxitoxins). Strains were isolated and genetically identified. Toxins were extracted and quantified by LC/MS-MS. All the taxa belong to the former Oscillatoriales. The presence of Nodosilinea and Toxifilum is reported for the first time for Spanish waters, but Pseudanabaena, Phormidium, Geitlerinema and Synechococcus also formed part of benthic mats. All the strains contained Microcystin-YR (MC-YR), but saxitoxin (STX) was present only in the extracts of Nodosilinea and Pseudanabena. MC-LY, MC-LW and [D-Asp³] MC-LR were detected in the extracts of Synechococcus and MC-LF in Toxifilum, but at concentrations that did not permit quantification. Toxins production by epipelic and epiphytic strains in coastal lagoons may represent a hazard, but also an opportunity to obtain potentially interesting compounds that should be further studied. Full article

This article is about the diversity of diatoms in the benthos of the upper sublittoral near Kazantip Cape, located on the shore of the Sea of Azov in the northeastern part of Crimea. The study was conducted in 2022 and 2023 at a depth of 0.1 to 1 m at temperatures from 3.7 °C to 29 °C and salinity from 13.6 to 15.6 psu on the following 11 species of macroalgae: Phaeophyta of Ericaria crinita, Gongolaria barbata, and Cladosiphon mediterraneus; Chlorophyta—Bryopsis hypnoides, Cladophora liniformis, Ulva intestinalis, and Ulva linza; and Rhodophyta—Callithamnion corymbosum, Ceramium arborescens, Polysiphonia denudata, and Pyropia leucosticta. A total of 97 taxa of Bacillariophyta belonging to 3 classes, 21 orders, 30 families, and 45 genera were found. The highest number of diatom species was found on U. linza (61 species), P. denudata (45), E. crinita (40), the lowest number was recorded on thalli P. leucosticta (9). On macroalgae were found of 80% benthic diatoms, 50% marine species, 36% brackish-marine, 9% freshwater, 5% brackish, and 36% cosmopolites. The maximum abundance of the diatom community was 243.4 × 10³ cells/cm² (P. denudata in September at 23.9 °C and 15.0 psu) with dominance by the diatom of Licmophora abbreviata, and the minimum was 3.8 × 10³ cells/cm² (P. leucosticta in January at 3.7 °C and 15.0 psu). The presence in the epiphyton of diatoms—indicators of moderate organic water pollution (32 species), which developed in masse in late summer—indicate a constant inflow of organic matter into the coastal waters of the Kazantip Cape. The bioindicator and statistical studies indicate the effectiveness of the conservation regime, especially at stations within the IUCN reserve, despite relatively high saprobity rates at stations exposed to recreational pressure and poorly treated domestic wastewater. Full article

Benthic diatoms have been studied in different areas of the Mediterranean Sea, but no data have been available for Israeli coastal waters until the present time. In this work, the composition, ecology, and phytogeography of diatoms of the macrophytes epiphyton are presented for the first time. Altogether, 85 diatom taxa were found among the epiphyton of 25 species of green, brown, and red macroalgae from the Israeli coast between March and May of 2021. These diatoms represent three classes, 17 orders, 26 families, and 41 genera. The taxonomic composition, ecology, and phytogeography of species are discussed. The distribution of diatoms are compared to that of other macrophytes and anthropogenic loads across the shoreline. The dominant species are given. Ecological characteristics and abundance in communities of revealed species are represented and statistically analyzed. The index of saprobity S varies between 1.69–2.71. Sites that stressed aquatic communities are indicated. The influence of the anthropogenic loads on the coastal territories is defined as a major factor that stimulated diatom species richness. Sites with anthropogenic stress for aquatic communities are indicated. Based on the composition of bioindicators, it is concluded that the section of the Israeli coast studied is oligo-mesotrophic compared to the eutrophic Gulf of Tartus. Full article

As the production of cultured bivalve mollusks is increasing worldwide, there is a growing need to study the biodiversity and ecology of microalgae in the mariculture zones. This study presents multiannual data (obtained in 2015–2016 and 2018–2020) on the species composition, abundance, biomass, and community structure of microphytobenthos from three mussel farm ecotopes (mussel shells, the epiphyton of twenty macroalgal species, and sediments under collectors). In total, 150 microalgal taxa were found, including 135 diatom species with a predominance of benthic (76%), marine (65%), and cosmopolite (30%) ones. In all habitats, 10 potentially harmful species and 44 indicators of organic pollution were noted. The maximum values on the mussel shells (abundance N = 119 × 10³ cells/cm² and biomass B = 0.0489 mg/cm²) were recorded in winter with the dominance of Tabularia fasciculata; in summer, the epiphyton was on the brown alga Nereia filiformis (N = 1001 × 10³ cells/cm² and B = 2.06 mg/cm²) with the dominance of toxic Pseudo-nitzschia seriata, on the red alga Phyllophora crispa (N = 1118 × 10³ cells/cm² and B = 3.24 mg/cm²) with the dominance of T. fasciculata, and in sediments (N = 104 × 10³ cells/cm³ and B = 0.046 mg/cm³) with the dominance of T. fasciculata and Bacillaria paxillifer. Statistically significant effects of the ecotope and sampling season on the diatom composition were noted. The strongest effect of temperature is observed for the mussel shell diatoms, for which the trend of abundance and biomass increase in winter and their decrease in summer is most noticeable. But in sediments, the effect of the season is reflected only in the permanent changes of the microalgae species composition. For the epiphyton, it was shown that it is temperature, rather than substrate macrophyte species, that affects its numerical structure. Full article

Rotifers represent an important component of freshwater zooplankton. The high richness of taxa, particularly in littoral macrophyte zones of water bodies in tropical and subtropical flood-prone areas, is a repeatedly reported fact. However, studies on the composition of periphytic rotifers in the Neotropics are reduced and almost non-existent in some regions. A qualitative study on rotifers (Monogononta) associated with littoral aquatic vegetation and their seasonal variation was carried out in three flood-prone ponds in the “Esteros de Camaguán Fauna Reserve” in the Venezuelan plains. For the selection of the collection sites, the two-stage stratified method with proportional affixation was used. Samples of macrophytes and the water associated with them were taken in littoral zones. The percentages of occurrence and numerical frequency were calculated for each rotifer taxa. The faunal similarities and correlations within and between ponds in the same and different climatic seasons were estimated using the Jaccard and Spearman coefficients (α = 0.05), respectively. In total, 102 rotifer taxa associated with 11 species of aquatic macrophytes were identified. The genus Taphrocampa with two taxa plus ten other taxa, are new records for Venezuela and one of them for South America. The taxocenosis and the geographic distribution of the reported taxa reflect a typical composition of the littoral zones of tropical regions. The total richness of both planktonic associated with aquatic vegetation and periphytic assemblages were similar. The highest richness of rotifer taxa coincided with the rainy season and the lowest with the early rainy season. The rotifer fauna presented low similarity values within and between ponds according to seasonality and, with some exceptions, between planktonic and periphytic environments. The importance of sampling periphytic rotifers and the influence of the flood cycle, and the degree of macrophyte development in the structuring of periphytic rotifer communities, were confirmed. Full article

Different types of water bodies in lowland river floodplains represent vital biodiversity havens and encompass diverse microhabitats, which are essential for structuring different macroinvertebrate communities. Chironomidae larvae (Diptera) are an inseparable part of these communities, with their high richness and abundance. In three water body types within the Danube floodplain Kopački Rit in Croatia, over the course of four sampling campaigns, we recorded 51 chironomid taxa in periphyton on macrophytes, twigs, and glass slides. The most diverse were chironomid communities on macrophytes, whilst month-old periphyton on twigs supported the least taxa. Cricotopus gr. sylvestris, Dicrotendipes lobiger, Dicrotendipes spp., Endochironomus albipennis, Glyptotendipes pallens agg., Polypedilum sordens and Polypedilum spp. were present in all studied microhabitats. The type of substrate is a very important factor influencing Chironomidae diversity and abundance, which was evident in the presence and dominance of Corynoneura gr. scutellata and Monopelopia tenuicalcar in the dense macrophyte canopy epiphyton. Finding pristine floodplains such as Kopački Rit can be very challenging, as such areas are increasingly altered by human activities. Studies of resident species and the extent to which changes in the parent river influence floodplain communities are important for the protection and restoration of the floodplains. Full article

Stream biofilms play an important role in the structure, functioning, and integrity of agricultural streams. In many lowland streams, macrophyte vegetation is abundant and functions as an important substrate for biofilm (epiphyton) in addition to the gravel and stone substrate for epilithon on the stream bed. We expect that reach-scale habitat conditions in streams (e.g., nutrient availability, hydraulic conditions) affect the epiphyton and epilithon biomass and composition, and that this effect will be substrate-specific (macrophytes and stones). The objectives of our study were (i) to describe concurrent changes in epiphyton and epilithon biomass and composition over a year in agricultural streams, and (ii) to determine the substrate specific reach-scale habitat drivers for the epiphyton and epilithon structure. We monitored epiphyton and epilithon biofilm biomass and composition at three-week intervals and reach-scale environmental conditions daily during a year for two agricultural steams. The results showed that epiphyton and epilithon communities differed in biomass, having high substrate specific biomass in epilithon compared to epiphyton. Epiphyton was mainly composed of diatom and green algae, while cyanobacteria were more important in epilithon, and the diatom species composition varied between the two biofilm types. Epiphyton structural properties were less influenced by reach-scale hydrology and nutrient availability compared to epilithon. The overall explanatory power of the measured environmental variables was low, probably due to micro-scale habitat effects and interactive processes within stream biofilms. Knowledge of biofilm control in agricultural streams is important in order to improve management strategies, and future studies should improve the understanding of micro-scale habitat conditions, interactive relationships within biofilms and between the biofilm and the substrates. Full article

Studies of tropical floodplains have shown that algae are the primary source material for higher consumers in freshwater aquatic habitats. Thus, methods that can predict the spatial variation of algal productivity provide an important input to better inform management and conservation of floodplains. In this study, a prediction of the spatial variability in algal productivity was made for the Mitchell River floodplain in northern Australia. The spatial variation of aquatic habitat types and turbidity were estimated using satellite remote sensing and then combined with statistical modelling to map the spatial variation in algal primary productivity. Open water and submerged plants habitats, covering 79% of the freshwater flooded floodplain extent, had higher rates of algal production compared to the 21% cover of emergent and floating aquatic plant habitats. Across the floodplain, the predicted average algal productivity was 150.9 ± 95.47 SD mg C m⁻² d⁻¹ and the total daily algal production was estimated to be 85.02 ± 0.07 SD ton C. This study provides a spatially explicit representation of habitat types, turbidity, and algal productivity on a tropical floodplain and presents an approach to map ‘hotspots’ of algal production and provide key insights into the functioning of complex floodplain–river ecosystems. As this approach uses satellite remotely sensed data, it can be applied in different floodplains worldwide to identify areas of high ecological value that may be sensitive to development and be used by decision makers and river managers to protect these important ecological assets. Full article

Priority pollutants such as polyethylene (PE) microplastic, lead (Pb²⁺), and cadmium (Cd²⁺) have attracted the interest of environmentalists due to their ubiquitous nature and toxicity to all forms of life. In this study, periphytic biofilms (epiphyton and epixylon) were used to bioremediate heavy metals (HMs) and to biodegrade PE under high (120,000 ppm) methane (CH₄) doses. Both periphytic biofilms were actively involved in methane oxidation, HMs accumulation and PE degradation. Epiphyton and epixylon both completely removed Pb²⁺ and Cd²⁺ at concentrations of 2 mg L⁻¹ and 50 mg L⁻¹, respectively, but only partially removed these HMs at a relatively higher concentration (100 mg L⁻¹). Treatment containing 12% ¹³CH₄ proved to be most effective for biodegradation of PE. A synergistic effect of HMs and PE drastically changed microbial biota and methanotrophic communities. High-throughput 16S rRNA gene sequencing revealed that Cyanobacteria was the most abundant class, followed by Gammaproteobacteria and Alphaproteobacteria in all high-methane-dose treatments. DNA stable-isotope probing was used to label ¹³C in a methanotrophic community. A biomarker for methane-oxidizing bacteria, pmoA gene sequence of a ¹³C-labeled fraction, revealed that Methylobacter was most abundant in all high-methane-dose treatments compared to near atmospheric methane (NAM) treatment, followed by Methylococcus. Methylomonas, Methylocystis, Methylosinus, and Methylocella were also found to be increased by high doses of methane compared to NAM treatment. Overall, Cd⁺² had a more determinantal effect on methanotrophic activity than Pb²⁺. Epiphyton proved to be more effective than epixylon in HMs removal and PE biodegradation. The findings proved that both epiphyton and epixylon can be used to bioremediate HMs and biodegrade PE as an efficient ecofriendly technique under high methane concentrations. Full article

The Konin lakes, heated by power stations and invaded by alien organisms, are a natural laboratory in which we can study the impact of climate change on the native communities of aquatic organisms. The aim of our study was to assess the impact of water heating and the occupation of the littoral zone of the lake by invasive species Vallisneria spiralis on changes in the species structure of rotifer communities of plankton, epiphyton and psammon. The archival material was used from the years: 1970–1975, 1978 and 1983, and compared with the results of studies conducted in Licheń and Ślesin Lakes in the years 2010–2011 and 2017–2018. It has been shown that the heating of waters of the studied lakes, combined with the shortening of their retention time, as well as the invasions of alien species, have caused significant changes in the taxonomic and trophic structure of plankton rotifers. In inhabiting Vallisneria bed epiphytic rotifer communities, the share of alien species did not increase, but relatively high densities of uncommon sessile species still persist. Psammon communities in the lakes are dominated by monogonont species relatively common in this habitat in nonheated lakes, but they are nearly devoid of bdelloids, which are abundant in psammon of Masurian lakes. Full article

Here we report the results of our decades-long study on epiphytic communities from two tributary systems of the Szigetköz section of the Danube River. The main goal of the investigation was to detect changes in the epiphytic communities at structural (core species, changes in the relative abundance of common species) and functional (trait changes) levels as a result of the most important anthropogenic effects on Szigetköz, i.e., hydro-morphological modifications. We also examined the impact of rehabilitation on the tributary systems in terms of ecological potential. We discovered that mainly motile diatom species characterized the epiphyton due to reduced water volume were introduced into the tributary system after the diversion of the Danube. The ecosystem stabilized in the rehabilitated section, while the non-rehabilitated section showed a worsening tendency, mainly in the parapotamic branches. Our long-term data sets may provide a good basis for comparisons of different aquatic ecosystems, to define changes in the abundance of core species and in the structure of community in response to different anthropogenic pressures. It is fundamental to determine adaptive traits in assessing the impact of global warming stressors on biodiversity. Full article

We carried out a first study of Lake Baikal epiphyton on six species of submerged macrophytes: Myriophyllum spicatum L., Potamogeton perfoliatus L., Potamogeton sp., Sparganium gramineum Georgi, Ceratophyllum demersum L., and Elodea сanadensis Michaux. We identified 70 epiphyton species and intraspecific taxa belonging to 3 phyla, viz. Ochrophyta, Cyanobacteria, and Chlorophyta. Nine species of Cyanobacteria were new records for Lake Baikal. Epiphyton communities differing in species composition and quantitative characteristics grew on diverse species of submerged macrophytes. High levels of species richness were recorded on Sparganiumgramineum and Potamogeton sp., whereas low diversity of epiphyton was observed on Myriophyllum spicatum and Elodea canadensis. A monodominant community was revealed on the invasive Elodea canadensis represented by Cocconeis placentula var. placentula. Specific characteristics of morphology of submerged macrophytes influenced the structural organization and quantitative development of epiphyton. Epiphyton abundance and biomass were higher on upper sections of most plants than on lower sections, probably because of canopy shading of macrophyte lower portions. Full article