Algal Abundance Research Articles

Habitat and Features of Development of Plankton Communities in Salt Lakes (South-Eastern Transbaikalia, Russia)

Results of studies of plankton algae and invertebrates in salt lakes of the territory of a closed runoff in the south of South-Eastern Transbaikalia (Russia) carried out in 2021–2022 are presented. Phyto- and zooplankton of sixteen saline lakes were studied during the maximum vegetation period from July to August. Lakes are different in chemical type: chloride, soda and sulfate. For chloride, sulfate and some soda lakes, data on plankton have been obtained for the first time. Fifty-four taxa of phytoplankton and twenty-seven species of zooplankton were found in soda lakes; twenty-three taxa of phytoplankton and four species of zooplankton were found in the chloride lakes; fifteen phytoplankton species and five zooplankton species were found in the sulfate lakes. For phytoplankton in soda lakes, green algae, cyanobacteria and diatoms were dominant. Green algae dominated in species composition in sulfate lakes; cryptophyte algae and cyanobacteria dominated in chloride lakes. For zooplankton, in all types of lakes, Brachionus plicatilis, Moina brachiata and Metadiaptomus asiaticus dominated. The abundance and biomass of algae and invertebrates in the surveyed lakes varied widely. Based on the results of the correlation analysis, total dissolved solids (TDS) are a key factor in the formation of planktonic communities in soda lakes; depth, transparency and temperature—in chloride lakes and pH—in sulfate lakes.

Testing the impact of Remotely Operated Vehicle (ROVs) camera angle on community metrics of temperate mesophotic organisms: A 3D model-based approach

While Remotely Operated Vehicle (ROV) technologies have rapidly increased our understanding of deeper water mesophotic ecosystems, there are some inherent problems in their use when estimating the abundance of sessile benthic organisms. Specifically, for rocky and coral reefs there has been recent debate about the importance of the angle of the ROV camera to the substrate, which is difficult to standardise, and how variation in this angle might impact abundance estimates and therefore our ability to detect change in mesophotic ecosystems. Here we simulated a series of 3D rocky temperate mesophotic communities based on real data with three different levels of habitat complexity (high, medium, and low). We ‘sampled’ these communities in a virtual space varying the angle of the camera to the substrate, to assess the influence of camera angle on percent cover estimates and overall benthic community composition. We found that increases in the ROV to substrate angle overestimated the percent cover (per degree of camera angle) of gorgonians (large: R2 = 0.16; small: R2 = 0.18), tubular sponges (R2 = 0.11), and ascidians (R2 = 0.05–0.13), and underestimated the abundance of Crustose Coraline Algae (R2 = 0.1, likely due to shading) in the most complex habitats. While we also found some significant differences in the overall benthic community and data dispersion for the more complex habitats, angle explained only a small amount of total variation (<6%) and significant dispersion was only found between 0- and 50-degree angles in high and medium complexity habitats. We conclude that while ROV to surface angle should be a consideration when sampling deep water reefs, its influence on standard measurements that we estimate with photography is likely to be low, and restricted to errors in the abundance of organisms with a high ratio of height to planar projection area (e.g., gorgonians).

Assessment of macroalgae coverage in a scarcely studied deep rocky reef in the tropical eastern Mexican Pacific

The biodiversity of epibenthic communities in rocky reefs in the Mexican tropical Pacific has been studied minimally during the past three decades. This study describes the abundance and distribution of algae and invertebrates in a deep rocky reef from this region. Samples were taken at 20 m depth in 2012 by randomly placing 50×50 cm quadrats. Also, photographs were taken of each quadrat to quantify the coverage of organisms. Throughout the study, the algae were the most abundant group (17748.5 cm m-2), of which encrusting calcified (6350.9 cm m-2), turf (3040.3 cm m-2), and larger-sized articulated corallines (2700.9 cm m-2) had the highest coverage. Regarding invertebrates, zoanthids (1153.3 cm m-2) and corals (746.7 cm m-2) had high coverage. All of the algal groups were found on vertical and horizontal substrates. The detrended correspondence analysis showed that larger-sized articulated corallines and encrusting not calcified groups were prevalent on the horizontal substrate and corals on the vertical substrate. These abundance and distribution patterns represent the first quantitative study of rocky reefs from the region. Considering the rapid influence of human activities in this coastal zone and the fact that rocky reefs have been minimally studied, there is a clear need for long-term monitoring programs to establish reef communities' patterns and processes, which are useful in conservation programs.

Giant Kelp Forest Resilience to Ocean Warming; Historical and Modern Systems

Giant kelp forests of the North Pacific are iconic among cool temperate marine communities. They are also amongst the most productive marine ecosystems, harboring significant biodiversity and supporting coastal economies. The fate of these systems over the next eight decades is uncertain, given the variance of outcomes for global warming scenarios and the complexities of ecological forecasting. There is a growing consensus that giant kelp will be susceptible to warming, leading to a decline of the communities. Kelp forest dynamics, however, are also controlled by biotic interactions. In the North Pacific, the main biotic factors today are kelp herbivory, especially by grazing sea urchins, and predatory control of the urchins, particularly by sea otters and sunflower sea stars. A recent study demonstrated that as late as the 18th century, the now extinct mega herbivore Steller’s sea cow, an obligate kelp browser, had a significant impact on North Pacific kelp forest dynamics. Mathematical models comparing the historical community to modern ones indicated that the sea cow would have increased forest resilience against reductions of predation of urchins caused by multiple types of perturbation. In addition to epidemics and temperature anomalies, it is expected that global temperatures will increase 2-4 degrees Celsius by the year 2100. Here we use the mathematical models to explore forest dynamics under various warming scenarios, including the changing impacts of epidemics and the frequency and intensity of warming anomalies. Preliminary results suggest that in contrast to a stable temperature regime, warming to 4 degrees increases chaotic dynamics, extinction of both sea urchins and sunflower sea stars, and abundance of understory algae. Those results also suggest that chaos and algal increase would be lessened in the presence of the extinct herbivore. These findings bear implications for future kelp forest management, conservation, and human economic exploitation.

Community Abundance and Environmental Monitoring to Support Coral Reef Management in East Portland Special Fishery Conservation Area, Jamaica

Global warming and human impacts continue to be devastating for coral reef systems. Jamaican reefs have been adversely affected by a variety of threats including hurricanes, coral bleaching, disease, and algal overgrowth, the impact of which has been exacerbated by global climate change, overfishing, and urchin disease. Despite the dire situation, with proper protection, algal coral phase shifts can be reversed. One area that is being protected is the East Portland Special Fishery Conservation Area (EPSFCA). The EPSFCA is monitored by the Alligator Head Foundation (AHF), which houses a coral nursery, mangrove nursery, and leads monitoring and restoration practices. Although reefs in Jamaica, such as Discovery Bay, were well studied in the 1970s-early 2000s, many ecological studies have not extended to other regions around the island. In particular, the unique reefs of Northeast Jamaica lack data necessary for conservation efforts; no baseline information on community composition had been collected until the establishment of the AHF. To obtain an ecological baseline, this project synthesizes environmental data (nutrient levels, temperature, light) with community assemblage data (fish counts, benthic substrate assessments, and invertebrate counts) from EPSFCA reefs. These sites will be compared using ordinations. To address a longer timeframe of reef evolution, this project will use similar techniques on a fossil reef to see how Caribbean reefs have changed over thousands of years. An analysis of EPSFCA reefs from 2017-2019 found that many sites are distinct, but most reefs show signs of degradation (e.g., high algal cover). Much of the variation between sites can be explained by the abundance of turf algae and the corals Colopophyllia natans, Agaricia grahamae, and Acropora cervicornis. The goal of this project is to combine the EPSFCA data with environmental information to provide a road map for where conservation efforts are likely to support recovery.

Steller’s Sea Cow and Kelp Forest Regeneration in the North Pacific

Modern ecosystems are almost universally degraded relative to their past counterparts, from the Pleistocene to the present day. Thus, modern ecosystems may serve as poor guides to conservation actions. Conservation paleobiology is well-suited to address this challenge through enhanced understanding of systems dynamics during past periods of greater species and functional diversity, abundances, and resilience. However, past and present ecosystem dynamics must be integrated to model the future impacts of conservation actions. Here we propose a three-step, Past-Present-Future (PPF) methodology rooted in mathematical modeling. First, construct a model of primary species and interactions of the present-day ecosystem, including biotic and abiotic components. Second, integrate historical and/or paleontological data into the model to investigate past states and processes of the ecosystem, with an emphasis on critical elements (e.g., ecological engineer species) that are no longer present. Third, integrate analyses from the first two steps to predict putative future dynamics and states, and use these to make testable predictions regarding specific conservation interventions. We illustrate this approach with a study investigating impacts of the now-extinct Steller’s sea cow on north Pacific giant kelp forests. The model indicates that the historical system was distinct from the modern, with differing abundances of giant kelp and understory algae. Furthermore, the familiar kelp-dominated state is metastable, capable of rapid transitions to an urchin-dominated state if perturbed by extreme hydrodynamic events, disease-driven reductions of seastar predation, or disease coupled to extreme warming events. We explore the possibility of increasing the resilience of modern forests by artificially recreating at least some of the ecological impacts of sea cows, accounting for metabolic requirements, estimates of abundance based on recent analyses of ancient DNA, and trophic impact.

Green route synthesis of antimicrobial nanoparticles using sewage alga bloom

Nanoparticles have a large surface area for their size and interact effectively with other particles. AgNPs may be created chemically, physically, or biologically. Biological techniques are considered the safest and cleanest since they use no toxic chemicals. Biological synthesis involves plant extracts, bacteria, fungus, algae, and other organisms. The algal production of AgNPs is of major interest. The abundance of algae and the ease with which it can be grown in a lab are two of the many reasons why it has become so popular as a nanoparticle production source. In this study, algae were employed as nanoparticles and antibacterial inhibitors against microbes.

Water Quality and Plankton Population Abundance Affected by Earthen Ponds Management

The study was conducted in two earthen ponds fish farming systems located at (El-Rayed area- Kafer El-Shiak governmentEgypt); namely, feed and fertilizer fish farming systems. Each system was replicated in four ponds (8000m2 each), to determine water quality, phytoplankton and zooplankton abundance. Nile tilapia (Orechromis niloticus); mullet (Mugil cephalus) and catfish (Clarias garipinus) were cultured in each pond at initial weight of 2, 30 and 50 g, respectively. The present study aimed to evaluate two fish farming systems differing in pond management procedures in the Nile Delta regions. Results apparent insignificant differences between the two fish farming systems in terms of water temperature (ranged 12.7 to 30.9°C from winter to summer months), salinity, EC and total hardness. Whilst, fertilizer fish farm had significantly high levels of pH, DO, secchi disc, total alkalinity, orthophosphate, TAN, NO2, NO3, algal abundance and chlorophyll “a” n water compared to those of feed fish farm. Significant increase (P&lt;0.05) in phytoplankton and zooplankton abundance were observed in fertilizer fish farm compared to feed fish farm, this was due the high organic manure inputs to pond water during all seasons including winter at one ton per feddan every 10 days.

Metabolomics Unravels Grazing Interactions under Nutrient Enrichment from Aquaculture

Our goal was to understand the mechanisms behind the impact of nutrient enrichment at intermediate distances from aquaculture on the interactions of a subtidal macroalgae community with its main grazer, the sea urchin Paracentrotus lividus. We assessed the diversity and cover of the macroalgal community, the abundance and biometrics of the sea urchins, the carbon and nitrogen elemental and isotopic compositions, and their metabolome in two stations, at an intermediate distance (station A) and away (station B) from a fish cage facility in the Aegean Sea (Greece), during the warm and cold seasons. The nutrient input at station A favored a shift to a macroalgal assemblage dominated by turf-forming species, depleted of native-erected species and with a higher abundance of invasive algae. A stable isotope analysis showed fish-farm-associated nitrogen enrichment of the macroalgae and trophic transfer to P. lividus. A decrease in metabolites related to grazing, reproduction, and energy reserves was found in P. lividus at station A. Furthermore, the metabolomic analysis was able to pinpoint stress in P. lividus at an intermediate distance from aquaculture. The chosen combination of traditional ecology with omics technology could be used to uncover not only the sublethal effects of nutrient loading but also the pathways for species interactions.

Reconstructing midge consumer-resource dynamics using carbon stable isotope signatures of archived specimens.

Population cycles can be caused by consumer-resource interactions. Confirming the role of consumer-resource interactions, however, can be challenging due to an absence of data for the resource candidate. For example, interactions between midge larvae and benthic algae likely govern the high-amplitude population fluctuations of Tanytarsus gracilentus in Lake Mývatn, Iceland, but there are no records of benthic resources concurrent with adult midge population counts. Here, we investigate consumer population dynamics using the carbon stable isotope signatures of archived T. gracilentus specimens collected from 1977 to 2015, under the assumption that midge δ13 C values reflect those of resources they consumed as larvae. We used the time series for population abundance and δ13 C to estimate interactions between midges and resources while accounting for measurement error and possible preservation effects on isotope values. Results were consistent with consumer-resource interactions: high δ13 C values preceded peaks in the midge population, and δ13 C values tended to decline after midges reached high abundance. One interpretation of this dynamic coupling is that midge isotope signatures reflect temporal variation in benthic algal δ13 C values, which we expected to mirror primary production. Following from this explanation, high benthic production (enriched δ13 C values) would contribute to increased midge abundance, and high midge abundance would result in declining benthic production (depleted δ13 C values). An additional and related explanation is that midges deplete benthic algal abundance once they reach peak densities, causing midges to increase their relative reliance on other resources including detritus and associated microorganisms. Such a shift in resource use would be consistent with the subsequent decline in midge δ13 C values. Our study adds evidence that midge-resource interactions drive T. gracilentus fluctuations and demonstrates a novel application of stable isotope time-series data to understand consumer population dynamics.

Interdisciplinary strategy to assess the impact of meteorological variables on the biochemical composition of the rain and the dynamics of a small eutrophic lake under rain forcing

Abstract. We present an interdisciplinary investigation of the links between the macro and microphysical properties of rain, the biochemical composition of rain, meteorological parameters, and their impacts on the phytoplankton dynamics of a mountain lake. In order to document this interdisciplinary scientific question, Lake Aydat in the French Massif Central mountains was fitted with a set of high-resolution atmospheric radars, a disdrometer, and a precipitation collector in 2020. In parallel, the lake was monitored via sensors and water sampling. To illustrate the potential of this novel experimental setup, we present a case study of a rain event that occurred in September 2020 and during which, three contrasting sub-periods were identified based on the type of rain (convective or stratiform). Using our high-temporal resolution monitoring, we show that the origin of the air mass mainly influences the chemical composition of the rain, which depends on the rain type. In contrast, the photosynthetic cell concentration in the rain is mainly influenced by meteorological variables, predominantly below-cloud scavenging. The very low concentrations of photosynthetic cells found in rain events cannot directly impact the lake's phytoplankton abundance. In contrast, the rain rate directly impacted the lake's thermal stratification during the convective event. The response of the phytoplankton depends on the genus and, interestingly, three cyanobacteria, Microcystis, Coelomoron, and Merismopedia, showed a systematic response to rain events with a sudden decrease in abundance at the lake surface immediately after rain events. In contrast, the abundance of green algae (Elakatothrix), picocyanobacteria (Synechocystis and Synechococcus), and diatoms (Asterionella and Melosira) gradually increased following the rain events, but with a lower intensity compared to the cyanobacteria species. These different phytoplankton responses to the same rainfall event could play a key role in phytoplankton dynamics in the temperate zone. Our results highlight the importance of high-frequency and time resolution monitoring of both atmosphere and lake to better understand the adaptive strategies of cyanobacteria following rain events.

Assessing the Impact of Chemical Algae Management Strategies on Anurans and Aquatic Communities.

Pond management with chemical and biological agents that reduce overgrowth of algae is an important means of maintaining water quality in residential ponds, yet the effects on nontarget species are not fully understood. We assessed the impact of Aquashade (a common nontoxic pond dye) and copper sulfate (a toxic algaecide) on American toad (Anaxyrus americanus), northern leopard frog (Lithobates pipiens), and Cope's gray treefrog (Hyla chrysoscelis) metamorphosis in outdoor mesocosm experiments. We also evaluated the relative impact of tadpole grazing versus chemical treatment on phytoplankton and periphyton abundance. We found no significant effects of pond management treatment on anuran metamorphosis, suggesting that addition of Aquashade and copper sulfate at tested concentrations does not significantly impact anurans under these experimental conditions. Interestingly, we found that the presence of tadpoles more strongly reduced algal abundance than Aquashade or copper sulfate by significantly decreasing phytoplankton and periphyton abundance over time. The present study suggests that anuran tadpoles may be effective at maintaining water quality, and that Aquashade and copper sulfate may have minimal effects on amphibian metamorphosis. Environ Toxicol Chem 2023;42:213-224. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Long-term changes in benthic communities following the invasion by an alien octocoral in the Southwest Atlantic, Brazil

Invasive alien species are considered one of the main threats to marine biodiversity. We used a BACI design to investigate the changes in rocky reef benthic communities related to the invasion of the octocoral Latissimia ningalooensis in the Southwest Atlantic. Drastic changes in benthic community structure were restricted to the invaded site and associated with the growth of L. ningalooensis on turf algae. Conversely, the zoanthid Palythoa caribaeorum remained stable coverage along the 9-year study period, indicating a greater biotic resistance against the octocoral. Latissimia ningalooensis spread from large and well-established patches to new areas of the reef, increasing turf-octocoral interactions. This study warns of the great invasive potential of the octocoral, due to its high abundance, competitive and expansion ability. The decline in abundance of turf-forming algae following the emergence of L. ningalooensis threatens the structure and functioning of macroalgal-dominated rocky reefs.

Antiscalants used in the desalination industry impact the physiology of the coral Montipora capricornis

Many coral reefs are found in arid and semi-arid regions that often face severe water scarcity and depend on seawater desalination for freshwater supply. Alongside freshwater production, desalination plants discharge brine waste into the sea. Brine includes various chemicals (e.g., antiscalants) that may harm the coastal environment. Although widely used, little is known about the ecotoxicological effects of antiscalants (AS) on hard corals. This study compared the impacts of polyphosphonate-based and polymer-based ASs on the coral Montipora capricornis. After two weeks of exposure, we determined the effects of AS on coral physiology, symbiotic microalgae, and associated bacteria, using various analytical approaches such as optical coherence tomography, pulse amplitude modulated fluorometry, and oxidative stress biomarkers. Both ASs reduced polyp activity (∼25%) and caused tissue damage (30% and 41% for polymer and polyphosphonate based AS, respectively). In addition, exposure to polyphosphonate-based AS decreased the abundance of endosymbiotic algae (39%) and upregulated the antioxidant capacity of the animal host (45%). The microalgal symbionts were under oxidative stress, with increased levels of antioxidant capacity and oxidative damage (a 2-fold increase compared to the control). Interestingly, exposure to AS enhanced the numbers of associated bacteria (∼40% compared to the control seawater) regardless of the AS type. Our results introduce new insights into the effects of brine on the physiology of hard corals, highlighting that choosing AS type must be examined according to the receiving ecosystem.

Large scale seasonal forecasting of peak season algae metrics in the Midwest and Northeast U.S.

In recent decades, many inland lakes have seen an increase in the prevalence of potentially harmful algae. In many inland lakes, the peak season for algae abundance (summer and early fall in the northern hemisphere) coincides with the peak season for recreational use. Currently, little information regarding expected algae conditions is available prior to the peak season for productivity in inland lakes. Peak season algae conditions are influenced by an array of pre-season (spring and early summer) local and global scale variables; identifying these variables for forecast development may be useful in managing potential public health threats posed by harmful algae. Using the LAGOS-NE dataset, pre-season local and global drivers of peak-season algae metrics (represented by chlorophyll-a) are identified for 178 lakes across the Northeast and Midwest U.S. from readily available gridded datasets. Forecasting models are built for each lake conditioned on relevant pre-season predictors. Forecasts are assessed for the magnitude, severity, and duration of seasonal chlorophyll concentrations. Regions of pre-season sea surface temperature, and pre-season chlorophyll-a demonstrate the most predictive power for peak season algae metrics, and resulting models show significant skill. Based on categorical forecast metrics, more than 70% of magnitude models and 90% of duration models outperform climatology. Forecasts of high and severe algae magnitude perform best in large mesotrophic and oligotrophic lakes, however, high algae duration performance appears less dependent on lake characteristics. The advance notice of elevated algae biomass provided by these models may allow lake managers to better prepare for challenges posed by algae during the high use season for inland lakes.

Significant Shifts in Microbial Communities Associated with Scleractinian Corals in Response to Algae Overgrowth.

Microbes play a key role in reef dynamics, mediating the competition between scleractinian corals and benthic algae; however, major shifts in bacterial communities among coral species in response to increases in the abundance of algae are not well understood. We investigated the taxonomic composition of coral-associated microbial communities under algae-overgrowth conditions using 16S rRNA gene sequencing. The results showed that non-algal (i.e., healthy) tissue (HH) had lower bacterial abundance and diversity than tissue collected from the coral-algae interface boundary (HA) and areas of algae growth (AA). Specifically, the HA and AA samples had higher relative abundances of Saprospiraceae, Rhodobacteraceae, and Alteromonadaceae. Compared with Platygyra sp. and Montipora sp., the physiological response of Pocillopora sp. was more intense under algae-induced stress based on microbial gene function prediction. Our results indicate that algal pressure can significantly alter the microbial community structure and function of coral ecosystems. Our data thus provide new insight into the relationship between corals and their microbiome under environmental stress.

Biogeography of algae and invertebrates from wave-exposed rocky intertidal habitats along the Atlantic coast of Nova Scotia (Canada): Latitudinal and interannual patterns and possible underlying drivers

Biogeographic studies aim to understand species distributions and are becoming increasingly relevant to establish baselines to monitor ecological change. The NW Atlantic coast hosts a cold-temperate biota, although knowledge about its biogeography is patchy. This study documents for the first time biogeographic variation at mid-to-high intertidal elevations in wave-exposed rocky intertidal habitats along the open Atlantic coast of Nova Scotia (Canada), a hydrographically distinct subregion of this cold-temperate region. For this goal, we measured the summer abundance of algae and invertebrates at the same nine locations over four consecutive years (2014 to 2017) spanning 415 km of coastline, which allowed us to examine latitudinal and interannual patterns. In addition, we looked for mensurative evidence on possible drivers underlying these patterns, focusing on sea surface temperature, daily maximum and minimum temperature (which often happen at low tides at thus differ from sea surface temperature), pelagic food supply for intertidal filter-feeders (phytoplankton abundance and particulate organic carbon), drift sea ice during the cold season (which can cause intertidal disturbance), and species associations. Our field surveys revealed that northern locations can be severely disturbed by ice scour when drift ice is abundant and, while biological recolonization occurs over the years, it differs in pace among locations. Southern locations, instead, did not experience ice scour during our study and, thus, generally exhibited a higher species richness and abundance than northern locations. Multivariate analyses indicated that the aforementioned expressions of temperature and pelagic food supply explained together 32–55% of the variation in alongshore biogeographic pattern, depending on the year. Species association analyses suggest that algal foundation species (generally more abundant at southern locations) contribute to increase location-wise species richness. Mensurative evidence for bottom-up forcing in seaweed–herbivore and filter-feeder–predator systems differed greatly among years. Overall, in addition to its inherent value to advance NW Atlantic intertidal biogeography, our species distribution database should be valuable to assess ecological change decades into the future as climate change and other anthropogenic influences unfold.

Responses of biological soil crusts to different types of vegetation restoration on the Chinese Loess Plateau: a case study

Biological soil crusts (biocrusts) are important components of dryland ecosystems. Vegetation strongly affects the distribution of biocrusts by influencing the soil stability, moisture and light availability. The Loess Plateau has been subjected to large‐scale restoration efforts; however, the type, coverage, and biomass of biocrusts responses to different types of vegetation restoration remain uncertain. Here, we investigated the biocrust characteristics (type, coverage, thickness, biomass, dominant cryptogam species, and relative abundance of major cyanobacteria and algae) in areas restored with different types of vegetation (Caragana korshinskii, Platycladus orientalis, Armeniaca sibirica, Populus hopeiensis, Pinus tabuliformis, Tamarix chinensis) and in a natural grassland on the Loess Plateau. Our results showed that the coverage, thickness, and biomass of the biocrusts were higher in the natural grassland than in the afforested areas, which suggests that the natural grassland is more suitable than the afforested areas for biocrust distribution. The biocrusts were composed mainly of mosses in the Pi. tabuliformis area and of cyanobacteria and algae in most of the other vegetation restoration areas. However, no biocrusts were observed in the T. chinensis area, probably because the dense canopy prevented light from reaching the soil. In addition, soil properties influenced by vegetation restoration may also affect the characteristics of biocrusts. Overall, our study suggests that natural grassland recovery, rather than afforestation, is likely the most suitable method for the development of biocrusts and provides suggestions for restoration and reconstruction on the Loess Plateau.

Biomarker metaproteomics for relative taxa abundances across soil organisms

Soil organisms are often classified using methods targeting individual groups of taxa (e.g., bacteria, fungi and invertebrates), which hampers our ability to directly compare the relative abundance of different groups across environmental gradients. We posit that the use of protein biomarkers could help to provide a more real representation of the cross-kingdom soil microbial populations. Here, we tested if the abundant proteins ATP synthase F(0) complex (ATPS), elongation factors (EF), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), GroEL, pyruvate dehydrogenase (PyrDH), RNA polymerase beta chain (RNAP), and translation initiation factor 2 (TIF) could be used to describe the taxonomic composition of microbial communities. As positive control, we used a mock community with different relative abundances of algae, archaea, bacteria, and viruses. We tested this approach on a previously published soil metaproteomes from which we randomly selected samples from forests, grasslands, and shrublands (each n = 10). Unfortunately, the biomarker approach is not feasible for viruses as these organisms do not share single genes. All biomarkers showed decent accuracy to determine the relative abundances of archaea, bacteria, and eukaryota in the mock community. However, false positive hits dominated on phylum level probably due to sequence homology. Archaeal proteins were only detected in the soil samples when EF was used as biomarker at an abundance of 0.7%. Bacteria dominated the EF-metaproteome and were most abundant in shrublands (64.4%) while eukaryotes were more abundant in forests (25.6%). In compliance with previously published results, the correlation analysis revealed the impact of mean annual temperature and pH on both bacteria and eukaryota. Our approach not only shows the potential to use biomarker metaproteomics to unveil the relative taxa abundances across soil organisms but also the need to create mock communities comprising members of all soil taxa.

Environmental DNA metabarcoding reveals the impacts of anthropogenic pollution on multitrophic aquatic communities across an urban river of western China

Anthropogenic activities are intensively affecting the structure and function of biological communities in river ecosystems. The effects of anthropogenic pollution on single-trophic community have been widely explored, but their effects on the structures and co-occurrence patterns of multitrophic communities remain largely unknown. In this study, we collected 13 water samples from the Neijiang River in Chengdu City of China, and identified totally 2352 bacterial, 207 algal, 204 macroinvertebrate, and 33 fish species based on the eDNA metabarcoding to systematically investigate the responses of multitrophic communities to environmental stressors. We observed significant variations in bacterial, algal, and macroinvertebrate community structures (except fish) with the pollution levels in the river. Network analyses indicated a more intensive interspecific co-occurrence pattern at high pollution level. Although taxonomic diversity of the multitrophic communities varied insignificantly, phylogenetic diversities of fish and algae showed significantly positive and negative associations with the pollution levels, respectively. We demonstrated the primary role of environmental filtering in driving the structures of bacteria, algae, and macroinvertebrates, while the fish was more controlled by dispersal limitation. Nitrogen was identified as the most important factor impacting the multitrophic community, where bacterial composition was mostly associated with NO3−-N, algal spatial differentiation with TN, and macroinvertebrate and fish with NH4+-N. Further partial least-squares path model confirmed more important effect of environmental variables on the relative abundance of bacteria and algae, while macroinvertebrate and fish communities were directly driven by the algae-mediated pathway in the food web. Our study highlighted the necessity of integrated consideration of multitrophic biodiversity for riverine pollution management, and emphasized the importance of controlling nitrogen inputs targeting a healthy ecosystem.