Continental Aquatic Ecosystems Research Articles

A holistic perspective on species delimitation outperforms all methods based on single data types in freshwater gastropods (Caenogastropoda: Hydrobiidae: Pseudamnicola)

Abstract Freshwater gastropods are one of the most species-rich and severely threatened animal groups in continental aquatic ecosystems. Unfortunately, understanding their species diversity, which is key to conservation, is often hampered by their small size, simple morphology, and restricted distribution. This is particularly the case for spring snails of the genus Pseudamnicola (family Hydrobiidae), a species-rich taxon across the Mediterranean region. Contrasting species diversities derived from molecular phylogenies and traditional taxonomy call for a holistic approach, in which molecular markers are used to identify putative taxonomic units that can then be validated morphologically. We integrated DNA sequence and morphometric data from 92 populations into a species delimitation framework to assess the taxonomic status of 25 nominal and 14 informally recognized species of Pseudamnicola across its geographical range. Although seven discovery methods delimited a varying number of putative species, taking an integrative approach generally improved species support over single datasets. The statistically favoured integrative scheme corroborated 30 of the 39 initial species as separate entities, whereas nine require taxonomic re-evaluation. Six species are described here formally. Pseudamnicola exemplifies the importance of considering multiple lines of evidence to evaluate species diversity in taxonomically complex groups, with newly developed approaches providing the needed toolbox.

Estimating the Colored Dissolved Organic Matter in the Negro River, Amazon Basin, with In Situ Remote Sensing Data

Dissolved organic matter (DOM) is a crucial component of continental aquatic ecosystems. It plays a vital role in the carbon cycle by serving as a significant source and reservoir of carbon in water. DOM provides energy and nutrients to organisms, affecting primary productivity, organic composition, and the food chain. This study presents empirical bio-optical models for estimating the absorption of colored dissolved organic matter (aCDOM) in the Negro River using in situ remote sensing reflectance (Rrs) data. Physical–chemical data (TSS, DOC, and POC) and optical data (aCDOM and Rrs) were collected from the Negro River, its tributaries, and lakes and empirical relationships between aCDOM at 440 nm, single band, and the ratio bands of Rrs were assessed. The analysis of spectral slope shows no statistically significant correlations with DOC concentration or aCDOM absorption coefficient. However, strong relationships were observed between DOC and aCDOM (R2 = 0.72), aCDOM and Rrs at 650 nm (R2 > 0.80 and RMSE < 1.75 m−1), as well as aCDOM and the green/red band ratio (R2 > 0.80 and RMSE < 2.30 m−1). aCDOM displayed large spatial and temporal variations, varying from 1.9 up to 20.1 m−1, with higher values in rivers of the upper course of the Negro basin and lower values in rivers with total solids suspended > 10 mg·L−1. Environmental factors that influence the production of dissolved organic matter include soil type, dense forest cover, high precipitation, and low erosion rates. This study demonstrated that aCDOM can serve as an indicator of DOC, and Rrs can serve as an indicator of aCDOM in the Negro basin. Our findings offer a starting point for future research on the optical properties of Amazonian black-water rivers.

Exploring the Effect of Salinity as a Primary Cause of Teratology in Freshwater Diatoms

<p>Increased water conductivity levels have been proposed as a key factor to explain the occurrence of teratological forms in freshwater diatom assemblages. The current study aimed to carry out an experiment on a laboratory scale to assess the response of periphytic diatoms to artificially increased salinity levels. The obtained results show that: a) the proportion of aberrant cells increased in high conductivity treatments, b) developed teratologies were preserved in diatom populations even after being translocated to normal conditions, and c) the degree of valve outline deformation in the dominant species was proportional to the induced water conductivity. All these data support previous field observations that linked high electrolyte content and the abundance of aberrant cells among microalgal communities in continental aquatic ecosystems.</p>

Population structure and dynamics of the Mediterranean Pond Turtle Mauremys leprosa (Schweigger, 1812) in contrasted polluted aquatic environments

Pollution contributes to the degraded state of continental aquatic ecosystems and biodiversity. Some species appear to be tolerant to aquatic pollution, yet little is known about the effects of such pollution on population structure and dynamics. Here, we investigated how wastewater treatment plant (WWTP) effluents of the Cabestany City, in southern France, contribute to the pollution levels of the Fosseille River, and we tested how they could affect population structure and medium-term dynamics of the native freshwater turtle, the Mediterranean Pond Turtle Mauremys leprosa (Schweigger, 1812). Amongst the 68 pesticides surveyed from water samples collected along the river in 2018 and 2021, a total of 16 pesticides were detected, among which eight were found in the upstream section of the river, 15 in the river section located downstream of the WWTP, and 14 in the outfall of the WWTP, exhibiting the contribution of effluents to the river pollution. From 2013 to 2018 and in 2021, capture-mark-recapture protocols were carried out on the freshwater turtle population living in the river. Using robust design and multi-state models, we showed a stable population throughout the study period, with high year-dependent seniority, and a bidirectional transition occurring primarily from the upstream to the downstream river sections of the WWTP. The freshwater turtle population consisted mostly of adults, with a male biased sex ratio detected downstream of the WWTP neither related to sex-dependent survival, recruitment, nor transition, suggesting a male bias in the hatchlings or primary sex ratio. Also, the largest immatures and females were captured downstream of the WWTP, with females having the highest body condition, whereas no such differences were observed in males. This study highlights that population functioning of M. leprosa is driven primarily by effluents induced resources, at least over the medium-term.

Identification, Abundance, and Distribution of Microplastics in Surface Water Collected from Luruaco Lake, Low Basin Magdalena River, Colombia

There are few studies on microplastic (MP) contamination in Colombia, and little is known about its impacts on continental aquatic ecosystems. This study evaluated, for the first time, the identification, abundance, and distribution of MP particles in the surface water of Luruaco Lake, in the low basin of the Magdalena River, Colombia, included in national programs in marine sciences and hydrobiological resources. Six stations and four samplings were established in the dry and rainy seasons. A total of 72 water samples were collected for microplastic extraction using hydrogen peroxide (H2O2) digestion, density separation with sodium chloride solution (NaCl), and filtration. The abundance of MPs ranged from 0 to 3.83 MPs·L−1, with an average of 1.90 MPs·L−1 in the rainy season and 0.25 MPs·L−1 in the dry season. According to the calculated coefficient of microplastics impact, the contamination in the surface water of Luruaco Lake is “maximum” to “extreme” for fibers with an average length of 2.05 mm and “minimum” to “average” for fragments that are 0.35 mm in size on average. Polyester (PES, 57.9%), polystyrene (PS, 47.0%), and polyethylene terephthalate (PET, 35.3%) polymers were more abundant in surface water. The temporal variation of the MPs indicates contamination related to the discharges of the tributary streams to the lake in the rainy season.

Early adaptations of true flies (Diptera) to moist and aquatic continental environments

AbstractInsect colonization of continental aquatic ecosystems and their immediate surroundings was paramount for the establishment of complex trophic nets and organic‐matter recycling in those environments. True flies and other insects such as mayflies developed crucial ecological roles in early continental aquatic ecosystems, as early as the Triassic. However, the mode and tempo of these processes remain poorly known, partly due to a critical fossil record gap before the Middle Triassic. Here we study the dipterans from the early Middle Triassic Konservat‐Lagerstätte of Pedra Alta (Aegean, early Anisian, Spain), which yields the oldest records of the order. Protoanisolarva juarezi gen. et sp. nov., based on an exceptionally preserved larva, shares key features with the extant nematoceran family Anisopodidae. Developing in inferred moist terrestrial environments contiguous with pools inhabited by aquatic organisms, it represents the only known Triassic dipteran larva with terrestrial affinities indicating that the amphipneustic respiratory system of insect larvae extends back to c. 247 Ma. Two nematoceran aquatic pupae are also described: one classified as Voltziapupa cf. cornuta, and the other as an indeterminate taxon. Finally, an egg cluster belonging to the ootaxon Clavapartus latus is likely to have been produced by chironomids. These eggs were included in a mucilaginous matrix, a probable adaptation against predation and/or changing conditions, including desiccation. These new findings provide key data on the early evolutionary history of the mega‐diverse order Diptera, the ecology of their ancestral pre‐adult forms, and the functioning of early Middle Triassic continental aquatic ecosystems.

Effect of eutrophication on the functional diversity of zooplankton in shallow ponds in Northeast Brazil

Abstract Eutrophication is a process characterized by the enrichment of a given aquatic environment with nutrients, triggering a serious and growing ecological problem in continental aquatic ecosystems, including effects on the biodiversity and ecosystem functioning. For this, we predicted that eutrophication decreases zooplankton functional richness, evenness, divergence and dispersion, and changes the functional composition of zooplankton. Zooplankton and water features were sampled in sixteen shallow ponds in northeastern Brazil. Functional diversity aspects were calculated for each assembly (rotifers, cladocerans, and copepods) using multidimensional indexes and functional groups. Principal component analysis, multiple linear regression, hierarchical cluster analysis and distance-based redundancy analysis were performed to characterize the environmental variation, and to identify associations with functional zooplankton diversity. We observed that turbidity and increased nutrients influenced the functional composition and functional diversity indices of zooplankton due to aquatic pollution. Eutrophic environments favored more specialized species, with greater selectivity in food capture and greater ability to escape predators. We suggest that eutrophic conditions lead to changes in the functional composition of the assemblies decreasing differentiation and variability of functional traits. Such changes lead to a loss of ecosystem processes and make these ecosystems more vulnerable.

Ecosistemas acuáticos continentales y sus servicios: Enfoques y escenarios de aplicación en el mundo real

Continental aquatic ecosystems (CAE) constitute elements of great natural, social and cultural value. They are also natural sinks of different processes that involve the water-land-atmosphere interface and, therefore, the first ones at a territorial level to show symptoms of environmental degradation. In this article, we analyze the ecosystem services (ES) approach and its application to CAE. Our primary objective is to provide an introduction and critical review of the approach and its practicalities for scientists, technicians and officials interested in water problems. We present the approach in general and carry out a breakdown of the main elements of the analysis, particularly those that we consider most relevant to promote an environmental and comprehensive view of the CAE. We also review the more contentious aspects of the ES approach and discuss the extent to which they represent practical nuances rather than conceptual divides. We then characterize different scenarios that provide opportunities for their application from an environmental stewardship perspective, including a review of nature-based solutions compared to their gray infrastructure-based counterparts. Beyond all the positive characteristics that could be attributed to the approach, we recognize that its effective incorporation into the traditional decision-making spheres of our country’s water resources will not be automatic. In this sense, we propose that it is necessary to align the ES approach with that of the integrated management of water resources, which is the basis of the ‘Guiding principles of water policy of the Argentine Republic’ adopted by the nation and the provinces. Ph: Microsoft Argentina

Adapting the dynamic LakeMab model to simulate seasonal variations of phosphorus concentration in reservoirs: a case study of Lake Bultière (France)

Controlling phosphorus is fundamental to limit the risk of eutrophication of continental aquatic ecosystems. Integrated modelling of its concentration in the aquatic continuum requires specific tools for water bodies. However, although simple static empirical models and complex biogeochemical models are numerous, there are few relatively simple and flexible models able to simulate seasonal variations in phosphorus concentrations in water bodies and particularly in reservoirs. In this study, the two-layer dynamic model, LakeMab, simulating phosphorus variations in water bodies, was enhanced to consider some tributary characteristics and reservoir specificities. It was then applied to the case of a reservoir in western France, Lake Bultiere. Without any calibration, the modified model reproduced reasonably well seasonal variations in phosphorus concentration in the lake. A sensitivity analysis showed the importance of improvements related to reservoir functioning (outlet depth, water level fluctuations) and the smaller importance of those related to tributaries (variable concentrations, depth of riverine inputs). The model can easily be applied to diverse lentic systems and could be coupled to stream models, thereby making it a useful tool for managing water quality in lakes and reservoirs.

Distribution of planktonic microcrustaceans (Cladocera and Copepoda) in lentic and lotic environments from the semiarid region in northeastern Brazil

Abstract The present study aimed to inventory the biodiversity of planktonic microcrustaceans (Cladocera and Copepoda) in 44 environments from the semiarid region of Brazil, increasing the knowledge about zooplankton community, including phytophilous species. Between 2011 and 2017, organisms were collected in a non - systematic way in the states of Rio Grande do Norte, Pernambuco, Ceará and Paraíba. A total of 60 species of planktonic microcrustaceans were identified, of which 52 were cladocerans and eight were copepods. The basin that presented the highest richness was Pajeú River with 41 species. Nevertheless, the extrapolated number of species shows an increasing tendency for this basin. The genus composition was different between the basins, with Moxotó basin (Pernambuco) being isolated from the others, probably since lagoons were the only type of environment sampled in this basin. Richness and abundance patterns were higher for the basins where sampling was mainly performed in lentic environments, such as Pajeú and Moxotó. Microcrustacean inventories and long-term studies need to be conducted more frequently to better understand the biodiversity of continental aquatic ecosystems in the semiarid region of Brazil.

ORGANIC MATTER COMPOSITION RELATED TO METHANE EBULLITIVE FLUX OF AN URBAN COASTAL LAGOON, SOUTHEASTERN BRAZIL

In 2016, Brazil emitted 18.25 Tg of methane. Some of these emissions occur through continental aquatic ecosystems, locations of fate and accumulation of organic and inorganic matter. Thus, the aim of this study is to evaluate the origin of organic matter in Rodrigo de Freitas Lagoon, an eutrophic, coastal and chocked lagoon in Rio de Janeiro, Brazil, through the determination of n-alkanes and sterols compounds in the upper two centimeters of sediment and compare these data with methane ebullitive flux. The concentrations of n-alkanes varied between 2.43 and 25.82 µg g-1. C29 was predominant compound in most sites, but also with important petrogenic source evidenced by the occurrence of Unresolved Complex Misture. The total concentration of sterols ranged from 2.76 to 56.01 µg g-1. β-sitostanol was the most abundant compound and coprostanol was the most relevant at the sites under influence of domestic effluents. CH4 ebullitive flux averaged 199 mg m-2 d-1 in the dry period and 9.3 mg m-2 d-1 during the wet season. We conclude that the organic matter reaching Rodrigo de Freitas Lagoon through the rivers discharge added or enriched with irregular sewage input and petroleum derivates are the main source of eutrophication and generate higher methane emissions to the atmosphere.

Acetate and sulphate as regulators of potential methane production in a tropical coastal lagoon

We evaluated the influence of acetate and sulphate addition on methanogenesis in sediment layers of cores of different carbon and sulphate concentrations from the littoral region colonized by Typha domingensis Pers. (area 1) and from the limnetic region (area 2) of a tropical coastal lagoon separated from the sea by a sandbar. We hypothesized that area 1 presents a proportionally smaller potential methane production (PMP) on sulphate addition than area 2. We further hypothesized that acetate addition stimulates proportionally greater PMP in area 2 sediment layers than in area 1. The PMP rates were measured in sediment samples from three depths (0–2, 2–6, and 6–10 cm) in areas 1 and 2 for 89 days. The sediment incubations were prepared with additions of acetate (1 mM), sulphate (10 mM), and acetate plus sulphate (1 and 10 mM, respectively); the control treatment had no addition of acetate and/or sulphate. We also measured dissolved organic carbon (DOC), carbohydrates, and sulphate in the interstitial water. PMP responded differently to acetate and sulphate addition. In general, PMP in area 2 was proportionally more stimulated by the addition of acetate and less inhibited by the addition of sulphate. In the 0–2-cm layer, the addition of acetate did not stimulate PMP in relation to the control in area 1, reaching a rate of 376.11 nmol CH4 g−1 day−1. In area 2, PMP was 5-fold higher in relation to the control, reaching 5.4 nmol CH4 g−1 day−1. Contrarily, in the 6–10-cm layer, sulphate addition inhibited PMP by 127.8-fold in relation to the control in area 1, reaching 0.6 nmol CH4 g−1 day−1. In area 2, PMP decreased 3.2-fold in relation to the control, reaching a value of 3.7 nmol CH4 g−1 day−1. These results agreed with the higher amounts of carbohydrates and lower amounts of sulphate in area 1 in the experiment beginning. Acetate and sulphate are effective PMP regulators in the sediment of two areas of a tropical coastal lagoon. Acetate increased PMP more in area 2, due to the lower sediment carbon availability. In contrast, sulphate decreased PMP more in area 1, due to the lower sulphate availability. The metabolic responses of methanogens and sulphate-reducing bacteria to natural and anthropogenic changes in carbon and sulphate availability are important for understanding the functioning of continental aquatic ecosystems, especially in scenarios of global climate change.

Food web and ecological models used to assess aquatic ecosystems submitted to aquaculture activities

ABSTRACT: Continental aquatic ecosystems play a fundamental role in economic and social development; however, they are vulnerable to environmental degradation due to the various stresses to which they are submitted. Aquaculture is among the main anthropic activities that influence these environments. Mathematical modelling of aquatic ecosystems performed using a set of computational tools allows simplified representation of environment regarding its biotic and abiotic components. Some of the most used techniques are: hydrodynamic modelling, focusing on the dispersion of nutrients; nutrient-mass balance modelling, especially phosphorus; bioenergetic modelling in animal production systems, with an estimate of the generation of residues in the environment by farmed animals; and trophic and ecological modelling, focusing on aquatic communities and their interactions. These techniques help understand changes caused by aquaculture systems in aquatic environments. In this way, it is possible to estimate the magnitude and extent of the impacts of these activities by simulating the possible environmental changes over time. It can be concluded that techniques involving mathematical modelling can provide relevant information for future impacts prediction on aquatic environments, promoting the management of water resources and their multiple uses.

Global species richness of hydrobiid snails determined by climate and evolutionary history

Abstract Efforts to describe spatial patterns of freshwater diversity and to evaluate their underlying factors have traditionally been focused on some animal groups (e.g. amphibians, fish or dragonflies). Despite being a dominant component in continental aquatic ecosystems and crucial for determining priority areas for conservation, broad‐scale data on gastropod total species, endemic and threatened species richness are limited. Based on these biodiversity indices, we identify global hotspots, extinction risk along the elevational gradient and the drivers of species richness patterns in the largest group of freshwater gastropods, the family Hydrobiidae. Given the strong dependency to a nonmarine aquatic environment, the observed richness patterns of extant hydrobiid species could be significantly influenced by large‐scale geography and dispersal processes as well as climatic conditions affecting continental ecosystems. Therefore, we tested several predictions for species richness derived from ecological and evolutionary hypotheses postulated for other freshwater groups. Based on a comprehensive literature and biodiversity database review, we compiled the number of total, endemic and threatened species per freshwater ecoregion. We classified ecoregions as hotspots if each biodiversity index was in the top 25% of its range and assessed the effect of 13 environmental and evolutionary factors on species richness using generalised linear models. We identified 906 species and 157 genera of Hydrobiidae showing mainly a Nearctic–Palearctic distribution and 19 biodiversity hotspots, most located across the Mediterranean Basin. In our data set, 83% of the species were endemic to a single ecoregion. Of the 43% non‐data deficient species, we found almost three times more threatened than non‐threatened species, and extinction risk peaked at 1,500 m a.s.l. Species richness was unequally distributed over biogeographic realms, increased with higher connectivity among ecoregions, and was negatively related with annual temperature range. Latitude and precipitation seasonality explained part of the richness variation by a nonlinear relationship. The identified hotspots correspond with those of other freshwater taxa. The hump‐shaped relationship of extinction risk with elevation is likely the consequence of decreasing natural and anthropogenic perturbations at higher elevations. Global hotspots of Hydrobiidae richness represent areas of climatic stability with medium precipitation and temperature seasonality that are well connected with other hydrological basins. Our results illustrate that both evolutionary and environmental factors determine these global patterns and that future changes of the latter factors may affect hydrobiid richness.

Evaluation of the relationship of picoplankton and viruses to environmental variables in a lagoon system (Çakalburnu Lagoon, Turkey)

ABSTRACTLagoons are defined as wetlands separated from the sea coasts on which they are located and sit between continental and marine aquatic ecosystems. Çakalburnu Lagoon is a coastal wetland on the southern side of the Bay of İzmir. Microorganisms, which are quite sensitive to changes occurring in environmental factors, are commonly used to determine the impact of environmental effects on the functioning of the ecosystem. In this study, variations in the abundance and biomass of picoplankton (Synechococcus spp. and bacteria) and the abundance of viruses, which identify the ecological productivity of the food chain, were seasonally examined by epifluorescence microscopy. Moreover, the microbial abundance and biomass relation over time between the physical and chemical parameters was evaluated. According to our results, the maximum abundance of Synechococcus spp. and viruses was 6.7 × 104 cell/ml and 9.9 × 108 cell/ml in the summer, respectively. Otherwise, the highest level of bacteria was measured at 3.6 × 107 cell/ml in the spring. Based on the principal component analysis and Pearson correlation analysis results, we concluded that total suspended solids, Chl-a, particulate organic carbon and particulate organic nitrogen were the major parameters influencing the observed variability of the lagoon system. Overall, to protect and improve the ecological and microbiological quality of aquatic systems such as lagoons, the necessary monitoring and measurement studies should be conducted in these sensitive areas.

Physiological effects caused by microcystin-producing and non-microcystin producing Microcystis aeruginosa on medaka fish: Aproteomic and metabolomic study on liver.

Cyanobacterial blooms have become a common phenomenon in eutrophic freshwater ecosystems worldwide. Microcystis is an important bloom-forming and toxin-producing genus in continental aquatic ecosystems, which poses a potential risk to Human populations as well as on aquatic organisms. Microcystis is known to produce along with various bioactive peptides, the microcystins (MCs) that have attracted more attention notably due to their high hepatotoxicity. To better understand the effects of cyanobacterial blooms on fish, medaka fish (Oryzias latipes) were sub-chronically exposed to either non-MC-producing or MC-producing living strains and, for this latter, to its subsequent MC-extract of Microcystis aeruginosa. Toxicological effects on liver have been evaluated through the combined approach of histopathology and 'omics' (i.e. proteomics and metabolomics). All treatments induce sex-dependent effects at both cellular and molecular levels. Moreover, the modalities of exposure appear to induce differential responses as the direct exposure to the cyanobacterial strains induce more acute effects than the MC-extract treatment. Our histopathological observations indicate that both non-MC-producing and MC-producing strains induce cellular impairments. Both proteomic and metabolomic analyses exhibit various biological disruptions in the liver of females and males exposed to strain and extract treatments. These results support the hypothesis that M.aeruginosa is able to produce bioactive peptides, other than MCs, which can induce toxicological effects in fish liver. Moreover, they highlight the importance of considering cyanobacterial cells as a whole to assess the realistic environmental risk of cyanobacteria on fish.

The use of spectral responses of surface in the discrimination of soils surface by remote sensing

Quaternary formations occupy all the lower levels of large sedimentary basins, forming thus ephemeral lakes in closed salt depressions, called commonly "sebkhas." They are continental aquatic ecosystems, classified as wetlands of inland backwaters. They provide several functions; such as aquatic life, geochemical and hydrological cycles.The aim of this paper is to characterize the surface states of salty soils of sebkha Sefioune and its surroundings in the north of Ouargla (South-eastern Algeria), by linking the remote sensing data acquired by satellite, observation and exploration of land surface in order to differentiate the surface states of the study area (sebkha Sefioune and nearby).The realization of spectral signatures from the satellite image (Landsat 7 ETM +), allowed us to individualize the soil surface states of sebkha Sefioune and its surroundings (North of Ouargla-Algeria) according to the spectral responses of each surface states.This approach allows us to say that the land surface states have different spectral behaviour according to their colour, water content (humidity), structure (roughness,) mineralogical and geochemical nature.

Benthic macroinvertebrate community in the Sinos river drainage basin, Rio Grande do Sul, Brazil.

Aquatic macroinvertebrate fauna is a relevant component of limnic continental aquatic ecosystems, playing an important role in several processes with relevant biocomplexity. The present study characterized the benthic macroinvertebrate fauna found in three hydric bodies in the Sinos river drainage basin regarding community structure. Sample was collected from January to December 2013 in three locations in the basin: the city of Caraá (29 °45'45.5"S/50°19'37.3"W), the city of Rolante (29°38'34.4"S/50°32'33.2"W) and the city of Igrejinha (29°36'10.84"S/50°48'49.3"W). Abiotic components (pH, dissolved oxygen and temperature) were registered and collected samples were identified up to family type. Average annual pH, dissolved oxygen and temperature were similar in all locations. A total of 26,170 samples were collected. Class Insecta (Arthropods) represented 85.5% of total sample. Platyhelmintes, Mollusca and Annelida samples were also registered. A total of 57 families were identified for the drainage basin and estimators (Chao-1, Chao-2 and jackknife 2) estimated richness varying from 60 to 72 families.

Molecular and geochemical constraints on anaerobic ammonium oxidation (anammox) in a riparian zone of the Seine Estuary (France)

To expand the limited knowledge about the ecological significance of anaerobic ammonium oxidation (anammox) in continental aquatic and terrestrial ecosystems, we studied community structure, abundance, and activity of anammox bacteria in soils and sediments in the wetland of Trou Deshayes, a riparian zone in the Seine Estuary, France. Combining (i) molecular analyses of the genes coding for anammox bacterial 16S rRNA and the enzyme hydrazine oxidoreductase (hzo), (ii) quantification of unique anammox bacterial membrane lipids (i.e. ladderanes), and, (iii) 15N-isotope label incubation experiments with intertidal sediments and irregularly flooded soils nearby, we demonstrated that anammox bacteria were ubiquitous in the studied wetland ecosystem. In both soils and sediments, detected anammox bacteria were related to Candidatus ‘Brocadia’. 16S rRNA genes were generally lower in the more oxygenated soils, but on the same order of magnitude (107–108 copies g−1 d.w.) as found for other river estuaries, riparian zones and agricultural soils. While the C20-ladderane fatty acid with five cyclobutane moieties (C20-[5]-FA) was found in both sediments and soils, other ladderane species were detected only in the wetland sediments. The observed differential ladderane distribution suggests intra-genus differences in the community composition of anammox bacteria between the sediments and the floodplain soils. While the abundance of anammox bacteria was significantly lower in the soils versus the sediments, the potential anammox rates were similar (≤15 and ≤22 nmol N2 d−1 g−1 w.w. sediment and soil, respectively), suggesting lower cell-specific anammox rates in the sediments. The observed potential rates of anammox were rather low, leaving canonical denitrification as the main fixed N removal pathway in this riparian zone. The relative contribution of anammox to the total N2 production (between 3 and 8 %) was similar at all sites, highlighting the dependence of the anammox process on nitrite supply from denitrification across environmental boundaries. Due to this coupling, the dependence of organotrophic denitrification on the quality and stoichiometry of OM also seems to affect the anammox bacterial community. Our results suggest that N removal and mitigation of N supply from agriculture in wetlands by anammox is limited, and much less important than denitrification.

A hierarchical bayesian model to quantify uncertainty of stream water temperature forecasts.

Providing generic and cost effective modelling approaches to reconstruct and forecast freshwater temperature using predictors as air temperature and water discharge is a prerequisite to understanding ecological processes underlying the impact of water temperature and of global warming on continental aquatic ecosystems. Using air temperature as a simple linear predictor of water temperature can lead to significant bias in forecasts as it does not disentangle seasonality and long term trends in the signal. Here, we develop an alternative approach based on hierarchical Bayesian statistical time series modelling of water temperature, air temperature and water discharge using seasonal sinusoidal periodic signals and time varying means and amplitudes. Fitting and forecasting performances of this approach are compared with that of simple linear regression between water and air temperatures using i) an emotive simulated example, ii) application to three French coastal streams with contrasting bio-geographical conditions and sizes. The time series modelling approach better fit data and does not exhibit forecasting bias in long term trends contrary to the linear regression. This new model also allows for more accurate forecasts of water temperature than linear regression together with a fair assessment of the uncertainty around forecasting. Warming of water temperature forecast by our hierarchical Bayesian model was slower and more uncertain than that expected with the classical regression approach. These new forecasts are in a form that is readily usable in further ecological analyses and will allow weighting of outcomes from different scenarios to manage climate change impacts on freshwater wildlife.