The influence of spatial processes on fish community structure: using a metacommunity framework for freshwater bioassessment

The use of biological indicators in a bioassessment approach is important for inferences of anthropogenic stress in routine monitoring programs. One of the primary assumptions of bioassessment is that biological indicators observed at specific sampling sites will allow for inferences of local environmental quality; however, this assumption requires a reliable understanding of dispersal processes, which is particularly relevant in river systems due to their dendritic network. Inter-stream dispersal between different points of the river network could bias bioassessment, especially for highly mobile organisms like fish. Here, we examine standard biological metrics used in routine biomonitoring to determine how spatial variables, including dispersal, influence inferences between fish populations and environmental gradients. Using redundancy analysis (RDA) and variation partitioning, we tested the relative influence of both environmental and spatial variables on fish community structure and related community metrics. Fish were collected from 99 sampling sites distributed across 44 rivers and streams of the Great Morava River Basin, Serbia. Electroconductivity, the percentage of agricultural areas, dissolved oxygen, ammonia, and nitrate-nitrogen were found to be significant environmental variables, while ten spatial predictors from broad- to small-scales were found to influence fish community structure and community metrics. Our results suggest that contemporary dispersal among streams influences fish community composition, but that trait-based metrics are less sensitive than basic measures of diversity to spatial processes. Our results highlight the need for spatially independent sampling, as well as the need to consider dispersal-based processes in routine biomonitoring.

Progress in understanding the vulnerability of freshwater ecosystems

The ability to collect and synthesize long-term environmental monitoring data is essential for the effective management of freshwater ecosystems. Progress has been made in assessment and monitoring approaches that have integrated routine monitoring programs into more holistic watershed-scale vulnerability assessments. While the concept of vulnerability assessment is well-defined for ecosystems, complementary and sometimes competing concepts of adaptive management, ecological integrity, and ecological condition complicate the communication of results to a broader audience. Here, we identify progress in freshwater assessments that can contribute to the identification and communication of freshwater vulnerability. We review novel methods that address common challenges associated with: 1) a lack of baseline information, 2) variability associated with a spatial context, and 3) the taxonomic sufficiency of biological indicators used to make inferences about ecological conditions. Innovation in methods and communication are discussed as a means to highlight meaningful cost-effective results that target policy towards heuristic ecosystem-management.

Implications of local niche- and dispersal-based factors that may influence chironomid assemblages in bioassessment

Local environmental factors and dispersal-based processes can both influence the structure of metacommunities in freshwater ecosystems. Describing these patterns is especially important for biomonitoring approaches that are based on inferences made from benthic macroinvertebrate assemblages. Here, we examine the metacommunity structure of chironomid assemblages collected from 28 sampling stations along the Southern Morava River, Serbia. We examined the extent of dispersal-based processes along a temporal scale. We obtained 8 models for the different sampling seasons that determined the spatial variables that best explained variability in chironomid assemblages. Spatial processes were found to be a significant predictor of variation for chironomids during the late winter/spring (March and May) and autumn (October and November), concordant with the known phenology of common taxa. Species sorting and mass effects were found to be significant processes that structured the chironomid metacommunity. In addition, biological interactions, inferred from fish biomass, and habitat traits, demonstrated by macrophyte and riparian vegetation, were found to influence species sorting. A high variability of chironomid metacommunity structure across sampling seasons suggests that monitoring programs that include macroinvertebrates in bioassessment should avoid months with pronounced spatial processes, and consequently maximize a correlation between community structure and local environmental factors.

The application of Uniform Manifold Approximation and Projection (UMAP) for unconstrained ordination and classification of biological indicators in aquatic ecology

The analysis of community structure in studies of freshwater ecology often requires the application of dimensionality reduction to process multivariate data. A high number of dimensions (number of taxa/environmental parameters × number of samples), nonlinear relationships, outliers, and high variability usually hinder the visualization and interpretation of multivariate datasets. Here, we proposed a new statistical design using Uniform Manifold Approximation and Projection (UMAP), and community partitioning using Louvain algorithms, to ordinate and classify the structure of aquatic biota in two-dimensional space. We present this approach with a demonstration of five previously published datasets for diatoms, macrophytes, chironomids (larval and subfossil), and fish. Principal Component Analysis (PCA) and Ward's clustering were also used to assess the comparability of the UMAP approach compared to traditional approaches for ordination and classification. The ordination of sampling sites in 2-dimensional space showed a much denser, and easier to interpret, grouping using the UMAP approach in comparison to PCA. The classification of community structure using the Louvain algorithm in UMAP ordinal space showed a high classification strength for data with a high number of dimensions than the cluster patterns obtained with the use of a Ward's algorithm in PCA. Environmental gradients, presented via heat maps, were overlayed with the ordination patterns of aquatic communities, confirming that the ordinations obtained by UMAP were ecologically meaningful. This is the first study that has applied a UMAP approach with classification using Louvain algorithms on ecological datasets. We show that the performance of local and global structures, as well as the number of clusters determined by the algorithm, make this approach more powerful than traditional approaches.

The influence of a lost society, the Sadlermiut, on the environment in the Canadian Arctic

High latitude freshwater ecosystems are sentinels of human activity and environmental change. The lakes and ponds that characterize Arctic landscapes have a low resilience to buffer variability in climate, especially with increasing global anthropogenic stressors in recent decades. Here, we show that a small freshwater pond in proximity of the archaeological site “Native Point” on Southampton Island (Nunavut, Arctic Canada) is a highly sensitive environmental recorder. The sediment analyses allowed for pinpointing the first arrival of Sadlermiut culture at Native Point to ~ 1250 CE, followed by a dietary shift likely in response to the onset of cooling in the region ~ 1400 CE. The influence of the Sadlermiut on the environment persisted long after the last of their population perished in 1903. Presently, the pond remains a distorted ecosystem that has experienced fundamental shifts in the benthic invertebrate assemblages and accumulated anthropogenic metals in the sediment. Our multi-proxy paleolimnological investigation using geochemical and biological indicators emphasizes that direct and indirect anthropogenic impacts have long-term environmental implications on high latitude ecosystems.

Bioassessment of the ecological integrity of freshwater ecosystems using aquatic macroinvertebrates: the case of Sable Island National Park Reserve, Canada

Due to ubiquitous distribution of taxa, relatively low-cost and efficient sampling procedure, and known responses to environmental gradients, macroinvertebrate indicators are often a central component of biological monitoring of freshwater resources. This study examined establishing a baseline reference of benthic macroinvertebrate indicators in a biomonitoring approach as a means for monitoring the freshwater ponds of Sable Island National Park Reserve (SINPR), Canada. We compared water quality parameters monitored from 2015 to 2019 to a biomonitoring approach deployed in May, June, and August of 2019. A total of 27 taxa were recorded from the 30,226 specimens collected, with highest abundances of Corixidae, Amphipoda, Oligochaeta, and chironomid species Polypedilum bicrenatum. We found significant variability of community structure between different months of sampling (p = 0.001) and between ponds (p < 0.0001). A high correlation was found between dissolved organic carbon, sulfate, and the diversity of macroinvertebrate indicators, while conductivity, ammonia, and calcium were found to be correlated with species richness. While we found that water chemistry parameters exhibited spatial and temporal differences, the diversity of macroinvertebrate indicators is likely to be a more resilient metric for comparison between ponds. Further, our findings demonstrate that biomonitoring can be effective in systems with a low number of small, shallow, freshwater pond ecosystems. As our study deployed a high-resolution identification of biological indicators, we were able to establish a baseline reference for future monitoring as well as identify specific associations between pond water quality and biological assemblages that can be used as a context for the management of SINPR's freshwater resources. Continued monitoring of these ecosystems in future years will help to understand long-term environmental changes on the island.

Application of deep learning in aquatic bioassessment: Towards automated identification of non-biting midges

Morphological species identification is often a difficult, expensive, and time-consuming process which hinders the ability for reliable biomonitoring of aquatic ecosystems. An alternative approach is to automate the whole process, accelerating the identification process. Here, we demonstrate an automatic machine-based identification approach for non-biting midges (Diptera: Chironomidae) using Convolutional Neural Networks (CNNs) as a means of increasing taxonomic resolution of biomonitoring data at a minimal cost. Chironomidae were used to build the automatic identifier, as a family of insects that are abundant and ecologically important, yet difficult and time-consuming to accurately identify. The approach was tested with 10 morphologically very similar species from the same genus or subfamilies, comprising 1846 specimens from the South Morava river basin, Serbia. Three CNN models were built utilizing either species, genus, or subfamily data. After training the artificial neural network, images that the network had not seen during the training phase achieved an accuracy of 99.5% for species-level identification, while at the genus and subfamily level all images were correctly assigned (100% accuracy). Gradient-weighted Class Activation Mapping (Grad-CAM) visualized the mentum, ventromental plates, mandibles, submentum, and postoccipital margin to be morphologically important features for CNN classification. Thus, the CNN approach was a highly accurate solution for chironomid identification of aquatic macroinvertebrates opening a new avenue for implementation of artificial intelligence and deep learning methodology in the biomonitoring world. This approach also provides a means to overcome the gap in bioassessment for developing countries where widespread use techniques for routine monitoring are currently limited.

Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity

Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a metadata analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric data sets overall consisting of 837 lakes. Our results indicate that in most of our data sets, summer temperature (T_jul ) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing T_jul in regions with present-day T_jul between 2.5 and 14°C. In some areas with T_jul  > 14°C, chironomid diversity stabilizes or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (~15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites.

Biomass burning and carbon monoxide patterns in Brazil during the extreme drought years of 2005, 2010, and 2015

In the 21st century, severe droughts associated with climate change will increase biomass burning (BB) in Brazil caused by the human activities. Recent droughts, especially in 2005, 2010, and 2015, caused strong socioeconomic and environmental impacts. The 2015 drought considered the most severe since 1901, surpassed the 2005 and 2010 events in respect to area and duration. Herein, based on satellite data, the 2005, 2010 and 2015 drought impacts on wildfire episodes and carbon monoxide (CO) variability during the dry and the dry-to-wet transition seasons were examined. The BB occurrences in the dry season were fewer during 2015 than during 2005 (-44%) and 2010 (-47%). Contrasting, the BB events in the dry-to-wet transition season, were higher during 2015 than during 2005 (+192%) and 2010 (+332%). The BB outbreaks were concentrated in the southern and southwestern Amazon during 2005, in the Cerrado region during 2010, and mainly in the central and northern Amazon during 2015, an area normally with few fires. The CO concentration showed positive variations (up to +30%) occurred in the southern Amazon and central Brazil during the 2005 and 2010 dry seasons, and north of 20 °S during the 2015-2016 dry-to-wet transition season. The BB outbreaks and the CO emissions showed a considerable spatiotemporal variability among the droughts of 2005, 2010, and 2016, first of them driven by local conditions in the tropical North Atlantic (TNA), characterized by warm than normal sea surface waters and the other two by the El Niño occurrences.

Unexpected differences in the population genetics of phasmavirids (Bunyavirales) from subarctic ponds

Little is known of the evolution of RNA viruses in aquatic systems. Here, we assess the genetic connectivity of two bunyaviruses (Kigluaik phantom orthophasmavirus or KIGV and Nome phantom orthophasmavirus or NOMV) with zooplanktonic hosts from subarctic ponds. We expected weak genetic structure among populations as the hosts (phantom midges) have a terrestrial winged dispersal stage. To test whether their respective viruses mirror this structure, we collected and analyzed population datasets from 21 subarctic freshwater ponds and obtained sequences from all four genes in the viral genomes. Prevalence averaged 66 per cent for 514 host specimens and was not significantly different between recently formed thaw ponds and glacial ponds. Unexpectedly, KIGV from older ponds showed pronounced haplotype divergence with little evidence of genetic connectivity. However, KIGV populations from recent thaw ponds appeared to be represented by a closely related haplotype group, perhaps indicating a genotypic dispersal bias. Unlike KIGV, NOMV had modest structure and diversity in recently formed thaw ponds. For each virus, we found elevated genetic diversity relative to the host, but similar population structures to the host. Our results suggest that non-random processes such as virus-host interactions, genotypic bias, and habitat effects differ among polar aquatic RNA viruses.

Drivers of Change in a 7300-Year Holocene Diatom Record from the Hemi-Boreal Region of Ontario, Canada

A Holocene lake sediment record spanning the past 7300 years from Wishart Lake in the Turkey Lakes Watershed in the Hemi-Boreal of central Ontario, Canada, was used to evaluate the potential drivers of long-term change in diatom assemblages at this site. An analysis of diatom assemblages found that benthic and epiphytic taxa dominated the mid-Holocene (7300–4000 cal yr BP), indicating shallow, oligotrophic, circum-neutral conditions, with macrophytes present. A significant shift in diatom assemblages towards more planktonic species (mainly Cyclotella sensu lato, but also several species of Aulacoseira, and Tabellaria flocculosa) occurred ~4000 cal yr BP. This change likely reflects an increase in lake level, coincident with the onset of a more strongly positive moisture balance following the drier climates of the middle Holocene, established by numerous regional paleoclimate records. Pollen-inferred regional changes in vegetation around 4000 yrs BP, including an increase in Betula and other mesic taxa, may have also promoted changes in diatom assemblages through watershed processes mediated by the chemistry of runoff. A more recent significant change in limnological conditions is marked by further increases in Cyclotella sensu lato beginning in the late 19^th century, synchronous with the Ambrosia pollen rise and increases in sediment bulk density, signaling regional and local land clearance at the time of Euro-Canadian settlement (1880 AD). In contrast to the mid-Holocene increase in planktonic diatoms, the modern increase in Cyclotella sensu lato likely indicates a response to land use and vegetation change, and erosion from the watershed, rather than a further increase in water level. The results from Wishart Lake illustrate the close connection between paleoclimate change, regional vegetation, watershed processes, and diatom assemblages and also provides insight into the controls on abundance of Cyclotella sensu lato, a diatom taxonomic group which has shown significant increases and complex dynamics in the post-industrial era in lakes spanning temperate to Arctic regions.

Limnological regime shifts caused by climate warming and Lesser Snow Goose population expansion in the western Hudson Bay Lowlands (Manitoba, Canada)

Shallow lakes are dominant features in subarctic and Arctic landscapes and are responsive to multiple stressors, which can lead to rapid changes in limnological regimes with consequences for aquatic resources. We address this theme in the coastal tundra region of Wapusk National Park, western Hudson Bay Lowlands (Canada), where climate has warmed during the past century and the Lesser Snow Goose (LSG; Chen caerulescens caerulescens) population has grown rapidly during the past ∽40 years. Integration of limnological and paleolimnological analyses documents profound responses of productivity, nutrient cycling, and aquatic habitat to warming at three ponds ("WAP 12", "WAP 20", and "WAP 21″), and to LSG disturbance at the two ponds located in an active nesting area (WAP 20, WAP 21). Based on multiparameter analysis of (210)Pb-dated sediment records from all three ponds, a regime shift occurred between 1875 and 1900 CE marked by a transition from low productivity, turbid, and nutrient-poor conditions of the Little Ice Age to conditions of higher productivity, lower nitrogen availability, and the development of benthic biofilm habitat as a result of climate warming. Beginning in the mid-1970s, sediment records from WAP 20 and WAP 21 reveal a second regime shift characterized by accelerated productivity and increased nitrogen availability. Coupled with 3 years of limnological data, results suggest that increased productivity at WAP 20 and WAP 21 led to atmospheric CO2 invasion to meet algal photosynthetic demand. This limnological regime shift is attributed to an increase in the supply of catchment-derived nutrients from the arrival of LSG and their subsequent disturbance to the landscape. Collectively, findings discriminate the consequences of warming and LSG disturbance on tundra ponds from which we identify a suite of sensitive limnological and paleolimnological measures that can be utilized to inform aquatic ecosystem monitoring.

Respiratory mechanics and lung histology in normal rats anesthetized with sevoflurane

Respiratory system, lung, and chest wall mechanical properties were subdivided into their resistive, elastic, and viscoelastic/inhomogeneous components in normal rats, to define the sites of action of sevoflurane. In addition, we aimed to determine the extent to which pretreatment with atropine modified these parameters. Twenty-four rats were divided into four groups of six animals each: in the P group, rats were sedated (diazepam) and anesthetized with pentobarbital sodium; in the S group, sevoflurane was administered; in the AP and AS groups, atropine was injected 20 min before sedation/anesthesia with pentobarbital and sevoflurane, respectively. Sevoflurane increased lung viscoelastic/inhomogeneous pressures and static elastance compared with rats belonging to the P group. In AS rats, lung static elastance increased in relation to the AP group. In conclusion, sevoflurane anesthesia acted not at the airway level but at the lung periphery, stiffening lung tissues and increasing mechanical inhomogeneities. These findings were supported by the histological demonstration of increased areas of alveolar collapse and hyperinflation. The pretreatment with atropine reduced central and peripheral airway secretion, thus lessening lung inhomogeneities.

Prevalence of intranasal ectopic teeth in children with complete unilateral and bilateral cleft lip and palate

OBJECTIVE

The objective of this study was to determine the prevalence of ectopic eruption of intranasal teeth.

DESIGN

This was a retrospective study, where records of children with repaired cleft lip and palate were analyzed.

SETTING

The study was conducted at a large craniofacial center, the Hospital for Rehabilitation of Craniofacial Anomalies, USP, Bauru, São Paulo, Brazil.

SUBJECTS

The sample consisted of 815 records from patients with bilateral cleft lip and palate (BCLP) and 1,495 records from patients with unilateral cleft lip and palate (UCLP). The age of the subjects was 5 to 10 years old and the groups included both males and females.

RESULTS

The results showed that 0.61% of the children with BCLP and 0.40% of those with UCLP had an intranasal tooth. The prevalence of an intranasal tooth for the whole group was 0.48%, and it appeared to be more common in females.

Effects of halothane on respiratory mechanics and lung histopathology in normal rats

It is generally accepted that halothane reduces airway and tissue resistance in lungs with preexisting airway tone. However, under conditions of resting airway tone, pulmonary resistance remains unaltered. In this study, we have determined the effects of halothane on respiratory system, pulmonary and chest wall resistive, elastic and viscoelastic mechanical properties, and related the results to findings from lung histology in intact normal rats. Sixteen adult male Wistar rats were allocated randomly to one of two groups (n = 8 in each group): control or halothane group. In the control group, animals were sedated with diazepam 5 mg i.p. and anaesthetized with pentobarbital 20 mg kg-1 i.p. In the halothane group, the anaesthetic was administered at an end-tidal concentration of I MAC throughout the study. Rats were paralysed and underwent mechanical ventilation. Halothane decreased airway resistance but increased the tissue component of resistance (caused by viscoelastic elements and lung inhomogeneity). Static and dynamic elastance also increased with halothane anaesthesia. Pulmonary resistance remained unchanged. Lung histopathology demonstrated airway dilatation and a greater degree of lung collapse and hyperinflation in the halothane group. We conclude that halothane anaesthesia acts both on airway and lung tissue. In airway tissue, dilatation occurs but the lung periphery stiffens. Consequently, these opposing effects result in no overall apparent change in mechanical properties, although changes are observed during halothane anaesthesia in normal animal and subjects.

Pulmonary morphofunctional effects of acute myocardial infarction

Acute myocardial infarction (AMI) may yield several respiratory changes. Nevertheless, no comprehensive pulmonary morphological/physiological correlation has been performed under this condition. The aims of the present investigation were: 1) to determine the respiratory parameters in an experimental model of coronary artery occlusion, 2) to relate these results to findings from lung histopathology, and 3) to evaluate the effects of propranolol used prior to AMI. Twenty-eight rats were anaesthetized and mechanically ventilated. In the control group (C), a suture line was passed around the left anterior descending coronary artery (LADCA). The infarct group (I) was similarly prepared but the LADCA was ligated and infarct resulted. In the control/propranolol (CP) and infarct/propranolol (IP) groups, propranolol was intravenously injected 5 min before surgery as performed in groups C and I, respectively. Lung static (EL,st) and dynamic (EL,dyn) elastances, airway resistance (RL,int), and viscoelastic/inhomogeneous pressure (deltaP2L) were determined before and 30, 60 and 120 min after surgery. In group I, EL,st, EL,dyn, RL,int and deltaP2L increased progressively throughout the experiment, and were higher than those found in groups C, CP and IP. All respiratory parameters but EL,st remained unaltered in group IP. Lung histopathological examination demonstrated alveolar, interstitial and intrabronchial oedema in group I. Group IP showed only interstitial oedema. Acute myocardial infarction yields lung resistive, elastic and viscoelastic changes. The last two results from alveolar and interstitial oedema, respectively. The previous use of propranolol diminishes respiratory changes.

Effects of prosthetic reconstruction of the abdominal wall on respiratory mechanics in rats

Respiratory mechanics and thoracoabdominal morphometry were determined in four sets of animal experiments before and after surgery. In group RRA the rectus abdominus muscles were removed; in RRAH rats the muscle resection was followed by lung hyperinflation; in PPM animals the defect was repaired by suturing a polypropylene mesh (Marlex); and in PPMH lung hyperinflation was performed after abdominal wall reconstruction. Lung and chest wall elastances, and chest wall viscoelastic/inhomogeneous pressures increased in RRA, RRAH and PPM groups. Static lung elastance was progressively smaller in the following order: RRA, PPM, and PPMH. In conclusion, removal of the rectus abdominus muscles and abdominal wall reconstruction could account for higher energy losses against viscoelastic and elastic forces acting on the chest wall, and these are related to a cephalad deviation of the diaphragm. Furthermore, hyperinflation reverses lung elastic modification after abdominal wall reconstruction with PPM, without beneficial effects in the presence of abdominal wall defect.