Effects of Oat Varieties and Growing Locations on Seed-Borne Fungal Communities

Many species of seed-borne fungi are closely allied with seed varieties and growing regions, including many seed-borne pathogens, but their species richness and distribution remain largely unknown. This study was conducted to explore the seed-borne fungal composition, abundance and diversity in Avena sativa (B7) and A. nuda (B2) seed samples collected from Baicheng (BB), Dingxi (DB) and Haibei (HB) city, using Illumina sequencing techniques. Our results show that a total of 543,707 sequences were obtained and these were assigned to 244 operational taxonomic units (OTUs) with 97% similarity. Oat varieties and growing locations had a significant difference on seed-borne fungal diversity. HB had a higher fungal diversity than BB and DB, Shannon diversity and ACE richness index of fungal in HB seeds was significantly higher than in BB and DB (P < 0.05). In different varieties, both taxon richness and evenness of B7 seeds was significantly higher than B2 (P < 0.05). A total of 4 fungal phyla and 26 fungal genera were detected. Ascomycota was the dominant phylum and Alternaria sp. was the most abundant genus in B2 and B7 oat seeds from different regions. Mycosphaerella sp. had a higher abundance in HB7 and DB7, respectively, Epicoccum sp. had a higher abundance in HB7 and BB7. The results of alpha and beta diversity analysis revealed the presence of different effects in fungal communities of different varieties and regions of oat, especially in seed pathogenic fungi distribution. Structural equation modeling also explained oat varieties and growing regions have significant influences on seed-borne fungal abundance, composition and diversity. This study demonstrated that the differences of varieties and regions are the main factors resulting in the changes of seed-borne fungal community of oat.

Spatial and Annual Variation in Microbial Abundance, Community Composition, and Diversity Associated With Alpine Surface Snow

Understanding microbial community dynamics in the alpine cryosphere is an important step toward assessing climate change impacts on these fragile ecosystems and meltwater-fed environments downstream. In this study, we analyzed microbial community composition, variation in community alpha and beta diversity, and the number of prokaryotic cells and virus-like particles (VLP) in seasonal snowpack from two consecutive years at three high altitude mountain summits along a longitudinal transect across the European Alps. Numbers of prokaryotic cells and VLP both ranged around 104 and 105 per mL of snow meltwater on average, with variation generally within one order of magnitude between sites and years. VLP-to-prokaryotic cell ratios spanned two orders of magnitude, with median values close to 1, and little variation between sites and years in the majority of cases. Estimates of microbial community alpha diversity inferred from Hill numbers revealed low contributions of common and abundant microbial taxa to the total taxon richness, and thus low community evenness. Similar to prokaryotic cell and VLP numbers, differences in alpha diversity between years and sites were generally relatively modest. In contrast, community composition displayed strong variation between sites and especially between years. Analyses of taxonomic and phylogenetic community composition showed that differences between sites within years were mainly characterized by changes in abundances of microbial taxa from similar phylogenetic clades, whereas shifts between years were due to significant phylogenetic turnover. Our findings on the spatiotemporal dynamics and magnitude of variation of microbial abundances, community diversity, and composition in surface snow may help define baseline levels to assess future impacts of climate change on the alpine cryosphere.

Functional Feeding Groups of Macrofauna and Detritus Decomposition along a Gradient of Glacial Meltwater Influence in Tropical High-Andean Streams

Tropical Andean glaciers are retreating rapidly, with possible consequences for trophic structure and ecosystem processes in high Andean meltwater streams. Here, we measured the environmental characteristics, quantified pools of particulate organic matter (POM) and periphyton (Chl. a), sampled benthic macroinvertebrates, determined functional feeding groups (FFG), and performed mesh bag decomposition experiments with Calamagrostis grass detritus at 17 stream sites along a gradient of glacial influence (GI) with 0–23% glacier cover in the catchment at 4050–4200 m a.s.l. in the Andes of Ecuador. POM was unrelated to GI while Chl. a. showed a weak (non-significant) negative relationship to GI. The macrofauna abundance decreased while taxon richness and the number of FFGs per site showed a hump-shaped relationship with increasing GI. Taxa with an opportunistic and generalist feeding mode generally dominated benthic assemblages and were related to high GI levels and low Chl. a. Only shredders were negatively related to GI, but unrelated to POM. Decomposition rates were comparable to those found in temperate alpine streams, and for both fine (0.0010–0.0065; median 0.0028 d−1) and coarse (0.0019–0.0088; median 0.0048 d−1) mesh bags, peaked at intermediate GI values, while the difference between bag types was small and almost constant along the GI gradient. This indicates an overall minor effect of macroinvertebrate shredders compared to that of microbes, in particular at high GI. It also suggests that the relatively high average temperature of these high-altitude equatorial streams (7–10 °C) does not produce higher decomposition rates than those in comparable but colder streams at temperate latitudes. The results suggest that, at the lower end of glacier cover, tropical glacier loss will not change the dominant microbial role in detritus decomposition, but that part of the physical abrasion could be partially replaced by biological shredding.

Spatial variation in the structure of overwintering, remnant Saccorhiza polyschides sporophytes and their associated assemblages

Understanding the structure and richness of natural communities is a fundamental goal of marine ecology, and foundation species such as large macroalgae have a disproportionate role in structuring biodiversity. However, high-resolution information on assemblages associated with macroalgae is lacking for many species and regions. Saccorhiza polyschides is a warm-temperate kelp with a relatively short lifespan (12–18 months), large thallus and bulbous holdfast offering habitat for diverse assemblages. In the UK, S. polyschides populations are thought to have proliferated recently. Here, we quantified the density and habitat structure provided by S. polyschides along a gradient of wave exposure within Plymouth Sound, and examined the composition and diversity of associated faunal assemblages. Density varied significantly between sites but not by wave exposure, while biometric measurements were generally highly variable. Senescing holdfasts from sporophytes offered valuable habitat, with high abundance and richness of associated assemblages, although these varied markedly between sporophytes and sites. Faunal abundance, taxon richness and diversity were significantly higher at fully exposed sites than at moderately exposed sites. Internal volume of holdfasts was positively correlated with faunal abundance and taxon richness. We recorded more than 27 distinct taxa and up to ~600 individuals within a single holdfast. Taxa included three fish species, including a novel observation of the pipefish Nerophis lumbriciformis. Further work is needed to examine seasonality in habitat structure and associated diversity patterns but our study demonstrates that even remnant holdfasts from decaying sporophytes represent a valuable microhabitat that may provide shelter, protection and food during winter.

Ecological Responses of Macroinvertebrates to an In-Stream Ecosystem Restoration Technique in a Tropical Stream in Eastern Uganda

A field experiment was conducted to examine the ecological responses of macroinvertebrates to an in-stream ecosystem restoration technique called woody debris introduced in a stream in different arrangements to show how they (woody debris) affected the macroinvertebrate ecology, specifically assemblage composition and biometrics in River Nabongo. The experiment was carried out in two heterogeneous stream environments i.e., i) in a riffle found in the middle reaches of the river at a higher altitude and ii) a pool in the lower altitude and reaches of the river. Each of these two treatments had a control plot for comparison purposes. Four macroinvertebrate sampling campaigns were launched in experimental sites from September 2019 to April 2021. All restoration structures had more macroinvertebrates than control and pre-treatment sites. The introduction of simple structures at the riffle site led to an increase in collector-filterers from 9-128 individuals, while at the pool site all the structures increased macroinvertebrates by 1151 individuals. Taxon richness was highest in the complex plot with 14±0.41 which significantly differed from the rest of the sampling plots at P<0.05. The relative abundance of taxa at the pool site varied significantly from one sampling plot to another at P<0.05 with the highest mean abundance registered in complex and simple structures having 61.3±0.10 and 23.5±0.11 respectively. It was concluded that complex woody debris structures increase the diversity, abundance and richness of aquatic macroinvertebrates by providing hard substrates for colonization by algae and microorganisms on which macroinvertebrates feed. We recommended that other researchers should study the impact of other in-stream ecosystem restoration techniques such as floating islands, constructed wetlands, D-deflectors, a comparison of which with restored woody debris will enable ecologists to choose the most suitable technique to apply at different stream points.

Spatially Variable Effects of Artificially-Created Physical Complexity on Subtidal Benthos

In response to the environmental damage caused by urbanization, Nature-based Solutions (NbS) are being implemented to enhance biodiversity and ecosystem processes with mutual benefits for society and nature. Although the field of NbS is flourishing, experiments in different geographic locations and environmental contexts have produced variable results, with knowledge particularly lacking for the subtidal zone. This study tested the effects of physical complexity on colonizing communities in subtidal habitats in two urban locations: (1) Plymouth, United Kingdom (northeast Atlantic) and (2) Tel Aviv, Israel (eastern Mediterranean) for 15- and 12-months, respectively. At each location, physical complexity was manipulated using experimental tiles that were either flat or had 2.5 or 5.0 cm ridges. In Plymouth, biological complexity was also manipulated through seeding tiles with habitat-forming mussels. The effects of the manipulations on taxon and functional richness, and community composition were assessed at both locations, and in Plymouth the survival and size of seeded mussels and abundance and size of recruited mussels were also assessed. Effects of physical complexity differed between locations. Physical complexity did not influence richness or community composition in Plymouth, while in Tel Aviv, there were effects of complexity on community composition. In Plymouth, effects of biological complexity were found with mussel seeding reducing taxon richness, supporting larger recruited mussels, and influencing community composition. Our results suggest that outcomes of NbS experiments are context-dependent and highlight the risk of extrapolating the findings outside of the context in which they were tested.

Abundance- and biomass-based metrics of functional composition of macroinvertebrate as surrogates of ecosystem attributes in Afrotropical streams

The composition of macroinvertebrate functional feeding groups (FFGs) has been used as surrogates of ecosystem attributes in aquatic ecosystems but studies that utilize such knowledge are still limited in the tropics. This study investigated the suitability of abundance- vs. biomass-based metrics of macroinvertebrate FFGs as surrogates of ecosystems attributes of the Sosiani-Kipkaren River in western Kenya. Macroinvertebrates were sampled in wet and dry seasons, classified into five FFGs and used to derive five metrics that are surrogates of ecosystem attributes; 1) a balance between autotrophy and heterotrophy, 2) linkage between riparian inputs of coarse particulate organic matter (CPOM) and fine particulate organic matter (FPOM), 3) top-down predator control, 4) geomorphic channel stability, and 5) relative dominance of fine particulate organic matter (FPOM) in transport compared to FPOM deposited in the sediments. Taxon richness, abundance and biomass of shredders were higher in forested sites, scrapers were numerically dominant in mid-order streams, whereas collectors dominated agricultural and urban sites. Abundance-based metrics were better predictors of ecosystem attributes and displayed a greater response to changes in stream size than biomass-based metrics. Moreover, there was incongruence between abundance- and biomass-based indicators for P/R and CPOM/ FPOM. Catchment land use did not influence metric performance, suggesting that reach scale influences played a predominant role in structuring communities and determining ecosystem functioning. Although the use of FFGs as indicators of ecosystem integrity and functioning in this river show promise, the lack of agreement between abundance- and biomass-based measures suggests that more studies are needed to refine the metrics used.

Meroplankton Diversity, Seasonality and Life-History Traits Across the Barents Sea Polar Front Revealed by High-Throughput DNA Barcoding

In many species of marine benthic invertebrates, a planktonic larval phase plays a critical role in dispersal. Very little is known about the larval biology of most species, however, in part because species identification has historically been hindered by the microscopic size and morphological similarity among related taxa. This study aimed to determine the taxonomic composition and seasonal distribution of meroplankton in the Barents Sea, across the Polar Front. We collected meroplankton during five time points seasonally and used high-throughput DNA barcoding of individual larvae to obtain species-level information on larval seasonality. We found that meroplankton was highly diverse (72 taxa from eight phyla) and present in the Barents Sea year-round with a peak in abundance in August and November, defying the conventional wisdom that peak abundance would coincide with the spring phytoplankton bloom. Ophiuroids, bivalves, and polychaetes dominated larval abundance while gastropods and polychaetes accounted for the bulk of the taxon diversity. Community structure varied seasonally and total abundance was generally higher south of the Polar Front while taxon richness was overall greater to the north. Of the species identified, most were known inhabitants of the Barents Sea. However, the nemertean Cephalothrix iwatai and the brittle star Ophiocten gracilis were abundant in the meroplankton despite never having been previously recorded in the northern Barents Sea. The new knowledge on seasonal patterns of individual meroplanktonic species has implications for understanding environment-biotic interactions in a changing Arctic and provides a framework for early detection of potential newcomers to the system.

Diversity Metrics Are Robust to Differences in Sampling Location and Depth for Environmental DNA of Plants in Small Temperate Lakes

Environmental DNA (eDNA) analysis methods permit broad yet detailed biodiversity sampling to be performed with minimal field effort. However, considerable uncertainty remains regarding the spatial resolution necessary for effective sampling, especially in aquatic environments. Also, contemporary plant communities are under-investigated with eDNA methods relative to animals and microbes. We analyzed eDNA samples from six small temperate lakes to elucidate spatial patterns in the distributions of algae and aquatic and terrestrial plants, using metabarcoding of the Internal Transcribed Spacer-1 (ITS1) genomic region. Sampling locations were varied across horizontal and vertical space: sites in each lake included a mixture of nearshore and offshore positions, each of which was stratified into surface (shallow) and benthic (deep) samples. We detected the expected community variation (beta diversity) from lake to lake, but only small effects of offshore distance and sampling depth. Taxon richness (alpha diversity) was slightly higher in nearshore samples, but displayed no other significant spatial effects. These diversity metrics imply that plant eDNA is more evenly distributed than its generating organisms in these small lake environments. Read abundances were heavily weighted toward aquatic macrophytes, though taxon richness was greatest in the algae and other non-vascular plants. We also identified representatives of many phylogenetically and ecologically varied plant taxa, including terrestrial species from surrounding areas. We conclude that freshwater plant eDNA surveys successfully capture differences among lake communities, and that easily accessible, shore-based sampling may be a reliable technique for informing research and management in similar ecosystems.

Structure of aquatic macroinvertebrate communities in streams of a sub-basin in the Pampa Biome, Southern Brazil

The Piratinim River is located in the northwest of Rio Grande do Sul, and represents an important effluent from the Uruguay River, with streams located far from urbanized areas, in conditions similar to those of environmental integrity, but under the influence of agricultural activities. In this study, we aim at investigating the structure of the aquatic macroinvertebrate community in streams of the Piratinim river basin by observing both spatial and local scales. The sampling was carried out in six streams distributed in three regions (upper, middle and lower) of the basin, thus exploring its upstream, intermediate and downstream stretches, during spring and autumn. Macroinvertebrates were collected using aquatic dipnets and were identified at the family level; trophic-functional categories were established according to the classification adapted to the state of Paraná. The spatial and temporal variations of the groups and of the biotic attributes (density, richness, diversity and equitability) were subjected to Kruskal-Wallis non-parametric tests and a posteriori Dunn’s tests. The abiotic variables were obtained to verify possible influence on the composition of the macroinvertebrate community, evaluated through a Canonical Correspondence Analysis. We sampled 11,564 macroinvertebrate individuals from 72 taxa, and found a predominance of the collector-filter trophic group. Abundance and richness were different between streams; the highest densities were found in the streams located in the upper region of the watershed (Chuní and Itú). The highest taxon richness was found in the lower region of the watershed (Guaracapa stream), and the lowest richness was found in the two streams for the intermediate region (Santana and Ximbocu). Diversity and equitability did not vary; temporal variations were not found. Canonical correspondence analysis explained 31.7% of the data variability. The main environmental variables that influenced macroinvertebrates distribution were temperature, electrical conductivity, dissolved oxygen, altitude and extension of the riparian forest. Seasonality and the longitudinal gradient along the basin represented determining factors for the structure and distribution of the macroinvertebrate community in the tributary streams of the Piratinim River.