Benthic Algal Communities Research Articles

Strong large‐scale structure–function coupling in benthic bacteria is mediated by algae in a geodiverse river network

AbstractBenthic bacteria in stream ecosystems drive organic matter mineralization. However, knowledge on how this ecosystem function is driven by bacterial community composition in interaction with environmental conditions and organic matter resources is poor. This is especially true when considering the regional scale of river networks, at which environmental conditions vary in a scale‐dependent manner and are spatially structured due to asymmetrical water flow. Similarly, organic matter resources may have a terrestrial origin in remote headwaters or be sourced locally from algae living in close proximity to bacteria in benthic biofilms. We investigated benthic biofilm meta‐community structure and function across the > 6700 km2 river network of the near‐natural Vjosa in Albania and Greece and found a strong control of the benthic algal community on bacterial community composition (13.4% of variability explained). In addition, bacterial community composition has linkages to water chemistry, which itself is strongly shaped by the diverse geology in the catchment, and to dispersal, shaping metacommunity structure as a neutral process. Notably, bacterial community composition explained the largest single fraction of variability (31.5%) in extracellular enzymatic activities, while there was no dependency of enzyme ratios on organic matter nor environmental conditions. Synergistic effects between bacteria and algae accounted for additional 47.3% of variability in heterotrophic functioning, emphasizing the importance of algal–bacterial interactions in benthic biofilms. Our findings shed new light on bacterial structure–function coupling highlighting the importance of algal–bacterial interactions at the river network scale.

Investigating the impact of watershed and local environmental variables on the spatial distribution, composition and functional diversity of benthic algal communities in the upper Red River Basin, China

Investigating the impact of watershed and local environmental variables on the spatial distribution, composition and functional diversity of benthic algal communities in the upper Red River Basin, China

The effect of habitat on benthic diatoms in subarctic ponds – differences between rock and sediment

Subarctic ecosystems represent a vulnerable environment for their biota and studying their habitats provides a better understanding of ongoing and accelerated environmental change. Literature suggests that habitat and environmental variables such as water chemistry jointly influence benthic algal species richness and assemblage composition. However, the combined effects of habitat and water chemistry on benthic algal communities are poorly understood especially in subarctic freshwaters. This study compared benthic diatom assemblages on rocks and on sediment and examined if environmental variables affect diatoms similarly in these habitats. A total of 20 subarctic ponds were sampled for diatoms on sediment and rock in summer 2022 in northern Fennoscandia. Differences in species richness and Pielou evenness between habitats were analysed by a paired Wilcoxon signed-rank test. The most significant environmental variables influencing diatom species richness were determined by generalized linear models. Differences in diatom assemblage compositions were analysed using non-metric multidimensional scaling, analysis of similarities, and Jaccard similarity index. Finally, to study how environmental variables shape diatom compositions on rock and sediment, a redundancy analysis was performed. According to our results species richness and evenness were significantly higher on sediment than on rock, and water pH was the major determinant for diatom richness in both habitats. Diatom assemblage composition did not differ between rocks and sediment, and composition was shaped by the same environmental variables such as pond surface area and water pH in both habitats. Our results support the prevailing conception that sediment habitat contains higher diatom species richness than rocks, while assemblage composition does not differ between these habitats. This study highlights the role of water pH on benthic diatoms regardless of their habitat. Given that global warming is expected to affect water pH levels, such a change will probably have a notable influence also on subarctic diatom communities in the future decades.

Peculiarities of the Formation of Benthic Algae Communities in the Kyiv Reservoir (Ukraine)

Peculiarities of the Formation of Benthic Algae Communities in the Kyiv Reservoir (Ukraine)

Anticipated impacts of climate change on the structure and function of phytobenthos in freshwater lakes

Climate change threatens surface waters worldwide, especially shallow lakes where one of the expected consequences is a sharp increase in their water temperatures. Phytobenthos is an essential, but still less studied component of aquatic ecosystems, and it would be important to learn more about how global warming will affect this community in shallow lakes. In this research, the effects of different climate change scenarios (SSP2-4.5 and SSP5-8.5, as intermediate and high emission scenarios) on the structure and function of the entire phytobenthos community using species- and trait-based approaches were experimentally investigated in an outdoor mesocosm system. Our results show that the forecasted 3 °C increase in temperature will already exert significant impacts on the benthic algal community by (1) altering its species and (2) trait composition (smaller cell size, lower abundance of colonial and higher of filamentous forms); (3) decreasing Shannon diversity; and (4) enhancing the variability of the community. Higher increase in the temperature (+5 °C) will imply more drastic alterations in freshwater phytobenthos by (1) inducing very high variability in species composition and compositional changes even in phylum level (towards higher abundance of Cyanobacteria and Chlorophyta at the expense of Bacillariophyta); (2) continuing shift in trait composition (benefits for smaller cell volume, filamentous life-forms, non-motile and weakly attached taxa); (3) further reducing the functional diversity; (4) increasing biofilm thickness (1.4 μm/°C) and (5) decreasing maximum quantum yield of photosystem II. In conclusion, already the intermediate emission scenario will predictably induce high risk in biodiversity issues, the high emission scenario will imply drastic impacts on the benthic algae endangering even the function of the ecosystem.

Hydrological disturbances enhance stochastic assembly processes and decrease network stability of algae communities in a highland floodplain system

Floodplains are hotspots for biodiversity research and conservation worldwide. Hydrological disturbances can profoundly influence the ecological processes and functions of floodplain systems by altering key biological groups such as algae communities. However, the impacts of flood disturbance on the assembly processes and co-occurrence patterns of algae communities in floodplain ecosystems are still unclear. To ascertain the response patterns of algae communities to flood disturbance, we characterized planktonic and benthic algae communities in 144 water and sediment samples collected from the Tibetan floodplain during non-flood and flood periods based on 23S ribosomal RNA gene sequencing. Results showed that planktonic algae exhibited higher diversity and greater compositional variations compared with benthic communities after flood disturbance. Flooding promoted algae community homogenization at horizontal (rivers vs. oxbow lakes) and vertical levels (water vs. sediment). Stochastic processes governed the assembly of distinct algae communities, and their ecological impacts were enhanced in response to flooding. In the non-flood period, dispersal limitation (81.78 %) was the primary ecological process driving algae community assembly. In the flood period, the relative contribution of ecological drift (72.91 %) to algae community assembly markedly increased, with dispersal limitation (22.61 %) being less important. Flooding reduced the interactions among algae taxa, resulting in lower network complexity and stability. Compared with the planktonic algae subnetworks, the benthic subnetworks showed greater stability in the face of flooding. Findings of this study broaden our understanding of how algae communities respond to hydrological disturbances from an ecological perspective and could be useful for the management of highland floodplain ecosystems.

Reducing the Risk of Benthic Algae Outbreaks by Regulating the Flow Velocity in a Simulated South-North Water Diversion Open Channel.

The reduction in open-channel flow velocity due to China's South-to-North Water Diversion Project (SNP) increases the risk of benthic algal community blooms resulting in drinking water safety issues. Consequently, it has attracted attention from all walks of life. However, regulatory measures to mitigate the risk of algal blooms and the main risk-causing factors are unclear. This study simulated the river ecosystem of the SNP channel through water diversion. Simulated gradient-increasing river flow velocity affects environmental factors and benthic algal alterations, and can be used to explore the feasibility of regulating the flow velocity to reduce the risk of algal blooms. We found that the algal biomasses in the velocity environments of 0.211 and 0.418 m/s decreased by 30.19% and 39.88%, respectively. Community structure alterations from diatoms to filamentous green algae were 75.56% and 87.53%, respectively. We observed significant differences in biodiversity, especially in terms of richness and evenness. The α diversity index of a species is influenced by physical and chemical environmental factors (especially flow velocity). Our study revealed that flow velocity is the main factor affecting the growth and outbreak of benthic algae. The risk of algal blooms in open channels can be effectively mitigated by regulating the flow velocity. This provides a theoretical basis for ensuring the water safety of large-scale water conservancy projects.

Gone and Back—The Anthropogenic History of Coccotylus brodiei (Turner) Kützing and Furcellaria lumbricalis (Hudson) J.V. Lamouroux in the Gulf of Gdańsk (Southern Baltic Sea)

The Gulf of Gdańsk environment has supported the development and growth of the local community for centuries but has been significantly degraded as a result of the progressive eutrophication process that started in 1960, the extensive exploitation of marketable species (plants and fish) and pollution limiting the growth of marine organisms. Multistressors of the Anthropocene era have left their mark on all aspects of the ecosystem, but despite this, the gulf region has been considered to have exceptional environmental value and high biodiversity in comparison with adjacent regions. In 2004, a Natura 2000 site was created in the eastern part known as Puck Bay, and actions were taken to protect endangered habitats and species. Between 2019 and 2020, intensive field studies were conducted in Puck Bay on flora to assess biodiversity and habitat resources. The material was collected for qualitative and quantitative analysis. This allowed observation of species that have not been reported since the 1970s, i.e., Coccotylus brodiei (Turner) Kützing and Furcellaria lumbricalis (Hudson) J.V. Lamouroux. Both species co-occurred as in the period before the 1960s in the form of free-floating thalli. The rediscovery of these taxa suggests that despite very unfavourable conditions for their development due to anthropogenic pressures, they were able to survive, and their occurrence throughout Puck Bay indicates improvement in environmental quality due to declining human impact. Our results indicate that benthic algal communities have high regeneration potential, but in the case of severe environmental degradation caused by synergistic pressures of high intensity, plant recovery without measures to support remediation takes at least 30 years.

Alkalinity and diatom assemblages in lowland streams: How to separate alkalinity from inorganic phosphorus in ecological assessments?

Benthic algae are widely used as ecological indicators of the ecological status of streams because they are widely distributed, they show high species diversity and they respond rapidly to human pressures in particular eutrophication and organic pollution. Recent findings have highlighted that in addition to human pressures, alkalinity may also play a role for community composition as bicarbonate becomes an increasingly important carbon source for photosynthesis when alkalinity increases. With this study, we aimed to elucidate how alkalinity influences the distribution of diatoms in Danish lowland streams, and to explore ifdiatom assemblage patterns can be affected by alkalinity in a way that interferes with the ecological assessment using diatom-based indices. We found that alkalinity affect the benthic algae community in lowland streams and that different species of diatoms were associated with different levels of alkalinity, a finding that might indicate dissimilarities in the efficiency of their HCO3− use. Nitzschia intermedia, Synedra acus, Nitzschia recta, Diatoma tenue, and Nitzschia linearis were associated with high alkalinity, whereas Synedra rumpens, Fragilaria vaucheriae, Psammothidium bioretii, and Gomphonema parvulum were associated with low alkalinity in streams with very low levels of phosphate. We also found that the Danish indicator for ecological status in streams (a combination of two Austrian indices, the Saprobic Index (SID) and the Trophic Index (TID) may exceed levels acceptable for good ecological status in moderate to high alkaline streams despite low phosphate levels. These findings highlight the need for the development of a diagnostic method to disentangle the effects of alkalinity from eutrophication and, additionally, that we need more insight into the autecology of species to interpret ecological assessments to be able to guide management efforts.

河流着生藻类多样性对城镇化的响应-以深圳市为例

PDF HTML阅读 XML下载 导出引用 引用提醒 河流着生藻类多样性对城镇化的响应——以深圳市为例 DOI: 10.5846/stxb202105271393 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 深圳市主要河流水生态监测与评价项目（NO.2019-07-233） Response of stream benthic algal diversity to urbanization: A case study in Shenzhen Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:着生藻类是河流生态状况的重要指示生物，然而关于城镇化对着生藻类多样性影响的研究还较缺乏。基于深圳市9条主要河流74个样点2020年雨、旱季的调查数据，对比了城区、郊区河流样点的着生藻类α、β多样性。两次调查共鉴定出着生藻类301个分类单元，其中硅藻门种类最多。谷皮菱形藻（Nitzschia palea）、隐头舟形藻（Navicula cryptocephala）、平庸菱形藻（Nitzschia inconspicua）等污染指示种在城区组相对丰度更高，而清洁指示种微小曲丝藻（Achnanthidium minutissimum）在郊区组相对丰度更高。城镇化对着生藻类物种丰富度、香农维纳多样性指数、Pielou均匀度指数等α多样性指数均无显著影响，但对着生藻类群落结构有显著影响。城区组样点的着生藻类β多样性（用主坐标分析质心指示）低于郊区组，城区组与郊区组藻类β多样性差异在旱季更为显著。两组样点的藻类β多样性差异主要来源于物种周转组分。与城区组着生藻类群落显著相关的环境因子包括总氮、高锰酸钾指数、电导率、pH、浊度和水深，而与郊区组着生藻类群落显著相关的是总氮、溶解性无机磷和电导率。研究发现，城市人类活动导致的总氮、溶解性无机磷、高锰酸钾指数、电导率等指标的显著增高导致着生藻类β多样性的降低。为了保护河流生物多样性，建议有效控制城区生产生活污水排放，减少人类活动对河流的干扰。 Abstract:Benthic algae are important indicators for ecological conditions of streams and rivers, but studies on effects of urbanization on benthic algal diversity is still sparse. In this study, we surveyed 74 sites from nine rivers located in Shenzhen City in the wet and dry season of 2020, and compared differences of α- and β- diversity of lotic benthic algal assemblages between urban and suburban groups. A total of 301 algal taxa were identified in the two seasons, among which the most taxa belonging to diatoms. The relative abundance of pollution indicator species such as Nitzschia palea, Navicula cryptocephala and Nitzschia inconspicua was higher in the urban groups, while the suburban groups with higher relative abundance of Achnanthidium minutissimum, which is an indicator species of clean water. We found that urbanization had no significant effects on algal α-diversity indices including richness, Shannon-Wiener's diversity index, and Pielou's index; while, algal community compositions in urban sites were significantly different from that of suburban sites. β-diversity of benthic algae, represented by centroids of the principal coordinate analysis, was lower for the urban sites than that of the suburban sites, with more significant difference in the dry season. The difference of benthic algal assemblages between the two groups mainly came from species turnover components. Total nitrogen, CODMn, conductivity, pH, turbidity and water depth were identified by the Mantel test as the environmental factors that were significantly correlated with algal community compositions in the urban group; while, TN, Dissolved inorganic Phosphorus (PO4-P) and conductivity were significantly correlated with the community compositions of benthic algae in the suburban group. We found that levels of TN, PO4-P, CODMn and conductivity were significantly increased in the urban group, which decreased β-diversity of benthic algae communities in Shenzhen rivers. To protect biodiversity of Shenzhen rivers, we therefore suggest to effectively control domestic and industrial sewage in urban areas to reduce human disturbance to rivers. 参考文献 相似文献 引证文献

Marine Benthic Algal Community in Geumodo at Dadohaehaesang National Park, Central South Coast of Korea

다도해해상국립공원 금오도지역의 해조군집에 대해서 2017년 2월부터 8월까지 3 계절동안 금오도 직포와 안도에서 조사를 실시하였다. 조사결과 총 104종(녹조류 16종, 갈조류 24종, 홍조류 64종)의 해조류가 분포하였으며, 직포에서 82종, 안도에서 72종이 출현하였다. 해조류 생물량은 직포에서 평균 203.50 g dry weight/㎡, 안도에서 평균 212.67 g dry weight/㎡ 이었다. 중요도(IV)에 따른 우점종은 구멍갈파래(Ulva australis), 지충이(Sargassum thunbergii), 돌가사리(Chondracanthus tenellus) 등으로 나타났다.

Spatial and local environmental factors outweigh geo‐climatic gradients in structuring taxonomically and trait‐based β‐diversity of benthic algae

AbstractAimUnderstanding the variation in biodiversity and its underlying drivers and mechanisms is a core task in biogeography and ecology. We examined (a) the relative contributions of species replacement (i.e., turnover) and richness difference (i.e., nestedness) to taxonomically and trait‐based β‐diversity of stream benthic algae; (b) whether these two facets of β‐diversity are correlated with each other; and (c) the relative contributions of local environmental, geo‐climatic and spatial factors to the two facets of β‐diversity and their components.LocationHun‐Tai River Basin, northeastern China.TaxonStream benthic algae.MethodsA total of 157 sites were sampled. Mantel tests were used to examine the complementarities between the two facets of β‐diversity and their components. Distance‐based redundancy analysis and variation partitioning were utilized to investigate the relative contributions of local environmental, geo‐climatic and spatial factors to each facet of β‐diversity and their components.ResultsWeak correlations between taxonomically and trait‐based β‐diversity and their components were detected, which indicated complementarity of ecological information. Taxonomically based total β‐diversity was largely driven by turnover, whereas trait‐based total β‐diversity was more driven by nestedness. Variation partitioning results indicated that local environmental and spatial factors contributed more than geo‐climatic variables to the total explained variation in taxonomically and trait‐based β‐diversity.Main conclusionsDifferent facets of β‐diversity and their decomposition are important for understanding diversity patterns of benthic algae relative to abiotic factors. A high level of trait‐based convergence among benthic algae communities, despite high taxonomic divergence, demonstrated turnover of species with similar biological traits across our study region. Our study provides a trait‐based insight into stream benthic algae communities, which was less documented by previous freshwater studies that focused on regions undergoing recovery following human disturbances.

Intertidal community of fucoid seaweeds in the Yarnyshnaya Bay, the Barents Sea

The specific and spatial structure of benthic algal community on the littoral zone in the east area of Murman coast of the Barents Sea (69°11'78''N, 36°04'38''E) has been studied in the conditions of anthropogenic influence absence. As a material for studying indicators of fucoid community and populations of dominating species in connection with habitats own long-term seasonal observations and data of scientific expeditions of 1994-2017 have served. The species composition of littoral phytocenosis consists of 39 species including 18 brown, 9 red and 12 green seaweeds, with prevalence on number of annual and seasonal species, on a biomass - perennials. Ecological factors influence essentially on seaweed distribution in different sites of the littoral zone. The major abiotic factors are presence of firm substratum, surf and storms, ice motion. Seaweed littoral community had multi-level structure, in which the basic layer was occupied by brown seaweeds with numerous litophytes and epiphytes under beds and on thallus of dominant species. The community algal biomass in the littoral zone was from 2.8 ± 0.6 up to 17.7 ± 2.9 kg/m² and depended on the species structure, substratum for benthic seaweeds, surf and tides. The biomass and density of fucoid seaweeds varied over a wide range in different biotopes under a natural rigid press of seasonal changes of environmental factors (temperature, surfs, storms) during tides and under natural damages of littoral community in the arctic region. As a whole littoral fucoid phytocenosis of the bay could be considered as an example of adaptation of seaweeds populations to the conditions of the northern seas. The received results could be useful for estimating ecological status of coastal ecosystem, at stock assessment of commercial seaweeds and for algal aquaculture development in the Barents Sea.

Study of the Biological Diversity of Benthic algae in the Tigris River, Baghdad - Iraq

The present work included a study of benthic algae on two substrates: rocks and clay on a section of the Tigris River at the Al-Atifiyah site in the fall of 2018. The result of this study was recorded 89 species belong to 50 genus of benthic algae on both substrates and composed of Bacillariophyceae (59.6%, 61.2%), Chlorophyceae (25.8%, 20.4%) and Cyanophyceae (14.5%, 18.3%) respectively on epilithic and epipelic algae. The present study was recorded the highest total algae cell density (1173.2 cells *103/cm2) on epilithic algae while the lowest total algae cell density was recorded on epipelic algae (76.95 cells *103/gm). For measure diversity, four indices of diversity are used: Margalef index, Shannon and Weaver Index, Evenness Index and Simpsons Index. The study showed that benthic algal communities are of high diversity with different distribution and spread of adherent algae on different natural surfaces in the aquatic environment. 62 species of epilithic algae were recorded belonging to 39 genus, while epipelic algae were recorded 49 species belonging to 34 genus. Bacillariophyceae was recorded the highest number of species compared with other classes of benthic algae (59.6%, 61.2%) respectively on epilithic and epipelic Chlorophyceae recorded second ordered after diatoms in importance 25.8%, 20.4%, Cyanophyceae recorded third orders 14.5%, 18.3% respectively on epilithic and epipelic algae.

Marine Benthic Algal Community at Dadohaehaesang National Park, South-west Coast of Korea

Marine Benthic Algal Community at Dadohaehaesang National Park, South-west Coast of Korea

Rapid colonization of aquatic communities in an urban stream after daylighting

Restoring aquatic ecosystems is still at an early stage and the outcomes of the remediation techniques used are often not reported, which limit opportunities to learn and further improve these methods. One common remediation technique in urban areas is daylighting, which involves the re‐opening of once buried streams with the aim of restoring ecosystem functions and services. In this study, we monitored the colonization of two important aquatic communities, benthic algae and macroinvertebrates, and assessed the nutrient retention capacity of a recently daylighted urban stream in the city of Oslo, Norway. The approach used involved transforming a buried channel into an open stream consisting of interconnected riffles and ponds seeded with aquatic and terrestrial plants. Benthic algal and macroinvertebrate communities begun to colonize the restored stretch within a relatively short time, 9 months following daylighting. The dynamics of the two aquatic communities differed, indicating that spatial processes are influential in determining the establishment of benthic algae, whereas time is more important for macroinvertebrate communities. The observed net nutrient retention from the daylighted stretch for phosphate, total nitrogen, total phosphorus, and calcium were 226, 128, 38 and 14%, respectively. However, the efficiency of the daylighted stretch to sequester nutrients was limited by the lack of controlling nutrient inputs from diffuse sources. This highlights the importance of addressing the influence of broader‐scale processes, extending beyond the boundaries of the restored reach, which can otherwise demise the success of daylighting.

Succession pattern and phylotype analysis of microphytobenthic communities in a simulated oil spill seagrass mesocosm experiment

Microphytobenthic communities play a significant role in nutrient modulation, sediment stabilization, and primary production in seagrass beds, which provide various ecosystem services. We hypothesized that microphytobenthic communities in sediments of chronically oil-exposed seagrass beds will exhibit increased resiliency to stressors associated with oil exposure as opposed to seagrass beds never exposed to oil spills. We prepared 14-liter seawater mesocosms, each containing a submersed macrophyte Ruppia maritima collected from the Chandeleur Islands, Louisiana, and Estero Bay, Florida. Mesocosms were initially exposed to 50% water-accommodated oil fractions (WAF) and subsequently diluted by 50% with daily artificial seawater exchanges over 8 days to simulate tidal dilution. High-throughput amplicon sequencing based on 23S rRNA gene targeting cyanobacteria and chloroplasts of eukaryotic microphytobenthos was conducted to assess the impact of oiling on microphytobenthic communities with additional assessment via microscopy. High-throughput sequencing in combination with traditional microscopic analysis provided a robust examination in which both methods roughly complemented each other. Distinct succession patterns were detected in benthic algal communities of chronically oil-exposed (Louisiana) versus unexposed (Florida) seagrass bed sediments. The impact of oiling in microphytobenthos across all samples showed that benthic diatoms dominated all algal communities with sample percentages ranging from 42 to 97%, followed by cyanobacteria (2 to 50%). It is noteworthy that drastic changes in microphytobenthic community structure in terms of the larger taxonomic level were not observed, rather change occurred at the phylotype level. These results were also confirmed by microscopy. Similarity percentages (SIMPER) analysis identified seven phylotypes (Cyanobacteria, Bacillariophyceae, and Mediophyceae) in the Louisiana samples and one phylotype (Bacillariophyceae) in the Florida samples that increased in relative sequence abundance after oil exposure. The detailed phylotype analysis identifying sentinel microphytobenthic indicators provides a base for future research on benthic microalgae response to ecosystem disturbance.

Benthic Algal Community in Relationship to Perturbation in the Tiko Mangrove Estuary Cameroon

Mangrove forests are among the most productive natural ecosystems in the world and offer invaluable ecological functions, yet are seriously threatened. Anthropogenic activities within mangroves can cause alteration of physicochemical parameters of sediments which in turn affect the assemblage of biological communities. This study was designed to assess the impact of anthropogenic disturbances within the Tiko mangroves on the benthic algal community. Perturbations were assessed through questionnaires. Two sets of composite sediment samples were collected for physicochemical and algal analyses from seven sites within the mangroves following standard methods. Seven drivers of change were identified (agriculture, human settlement, logging, fuel wood collection, fishing, fish smoking and petty trading) as the main perturbations of the ecosystem. A total of 141 benthic species were identified at the different sites. The Bacillariophyta were the most abundant with 60 algal species followed by Chlorophyta with 38 algal species. The most dominant species were Chlorobotrys regularis (50) and Microcytis sp (38). Site 3 (settlement site) was the most diversed with 72 species. The mean abundance of benthic algae ranged from 0.59 ± 0.17 to 2.08 ± 0.58. High concentrations of nutrients and the presence of Bacillariophyta and Microcystis suggest pollution. There is a need to monitor activities carried out around the mangrove ecosystem with respect to quantity and quality of waste discharged into the environment since this is a highly sensitive environment.

Assessment of littoral algal diversity from the northern Gulf of Mexico using environmental DNA metabarcoding.

Traditional methods for algal biodiversity monitoring are costly and time inefficient because they rely on high-level taxonomic expertise to address species identity problems involving phenotypic plasticity and morphological convergence. These problems are exacerbated in regions such as the Gulf of Mexico, that has a limited history of phycological exploration, but that are economically important or threatened by numerous anthropogenic stressors. Given the high pace of disturbance to natural systems, there is a critical need for expedient and cost-effective tools for the study of benthic algal communities. Here we document the use of environmental DNA metabarcoding, using the partial LSU rDNA and 23S rDNA plastid molecular markers, to elucidate littoral algal diversity in the Northern Gulf of Mexico. We assigned 73.7% of algal OTUs to genus and 59.6% to species ranks. Our current study detected molecular signals for 35algal/protist species with no previous reports in the Gulf of Mexico, thus providing an important, molecular-validated, baseline of species richness for this region. We also make several bioinformatic recommendations for the efficient use of high-throughput sequence data to assess biological communities.

Low temporal dynamics of mycosporine-like amino acids in benthic cyanobacteria from an alpine lake.

Cyanobacteria are one of the oldest organisms on Earth and they originated at a time when damaging ultraviolet (UV) C radiation still reached the surface. Their long evolution led to several adaptations to avoid deleterious effects caused by exposure to solar UV radiation. Synthesis of sunscreen substances, such as mycosporine‐like amino acids (MAAs), allows them to photosynthesise with reduced risk of cell damage. The interplay of solar UV radiation and MAAs is well documented for cyanobacteria in the plankton realm, but little is known for those in the benthic realm, particularly of clear alpine lakes.Here, we assessed the temporal dynamics of MAAs in the benthic algal community of one clear alpine lake dominated by cyanobacteria during the ice‐free season and along a depth gradient using state‐of‐the‐art analytical methods (high‐performance liquid chromatography, nuclear magnetic resonance, liquid chromatography–mass spectrometry). We differentiated between the epilithic cyanobacterial community and the overlying loosely attached filamentous cyanobacteria, as we expected they will have an important shielding/shading effect on the former. We hypothesised that in contrast to the case of phytoplankton, benthic cyanobacteria will show less pronounced temporal changes in MAAs concentration in response to changes in solar UV exposure.Three UV‐absorbing substances were present in both types of communities, whereby all were unknown. The chemical structure of the dominant unknown substance (maximum absorption at 334 nm) resulted in the identification of a novel MAA that we named aplysiapalythine‐D for its similarity to the previously described aplysiapalythine‐C.Chlorophyll‐a‐specific MAA concentrations for epilithic and filamentous cyanobacteria showed a significant decrease with depth, although only traces were found in the former community. The temporal dynamics in MAA concentrations of filamentous cyanobacteria showed no significant variations during the ice‐free season.Our result on the low temporal MAA dynamics agrees with the reduced growth rates of benthic cyanobacteria reported for cold ecosystems. The permanent presence of this community, which is adapted to the high UV levels characteristic of clear alpine lakes, probably represents the most important primary producers of these ecosystems.