Types Of Aquatic Systems Research Articles

Biodegradation of poly(butylene adipate terephthalate) and poly(vinyl alcohol) within aquatic pathway

Understanding the environmental fate of biodegradable plastics in aquatic systems is crucial, given the alarming amount of plastic waste and microplastic particles transported through aquatic pathways. In particular, there is a need to analyze the biodegradation of commercialized biodegradable plastics upon release from wastewater treatment plants into natural aquatic systems. This study investigates the biodegradation behaviors of poly(butylene adipate terephthalate) (PBAT) and poly(vinyl alcohol) (PVA) in wastewater, freshwater, and seawater. Biodegradation of PBAT and PVA assessed through biochemical oxygen demand (BOD) experiments and microcosm tests revealed that the type of aquatic system governs the biodegradation behaviors of each plastic, with the highest biodegradation rate achieved in wastewater for both PBAT and PVA (25.6 and 32.2 % in 30 d, respectively). Plastic release pathway from wastewater into other aquatic systems simulated by sequential incubation in different microcosms suggested that PBAT exposed to wastewater and freshwater before reaching seawater was more prone to degradation than when directly exposed to seawater. On the other hand, PVA displayed comparable biodegradation rate regardless of whether it was directly exposed to seawater or had passed through other environments beforehand. Metagenome amplicon sequencing of 16S rRNA genes revealed distinct community shifts dependent on the type of plastics in changing environments along the simulated aquatic pathway. Several bacterial species putatively implicated in the biodegradation of PBAT and PVA are discussed. Our findings underscore the significant influence of pollution routes on the biodegradation of PBAT and PVA, highlighting the potential for wastewater treatment to facilitate rapid degradation compared to direct exposure to pristine aquatic environments.

Challenges Regionalizing Methane Emissions Using Aquatic Environments in the Amazon Basin as Examples

Key challenges to regionalization of methane fluxes in the Amazon basin are the large seasonal variation in inundated areas and habitats, the wide variety of aquatic ecosystems throughout the Amazon basin, and the variability in methane fluxes in time and space. Based on available measurements of methane emission and areal extent, seven types of aquatic systems are considered: streams and rivers, lakes, seasonally flooded forests, seasonally flooded savannas and other interfluvial wetlands, herbaceous plants on riverine floodplains, peatlands, and hydroelectric reservoirs. We evaluate the adequacy of sampling and of field methods plus atmospheric measurements, as applied to the Amazon basin, summarize published fluxes and regional estimates using bottom-up and top-down approaches, and discuss current understanding of biogeochemical and physical processes in Amazon aquatic environments and their incorporation into mechanistic and statistical models. Recommendations for further study in the Amazon basin and elsewhere include application of new remote sensing techniques, increased sampling frequency and duration, experimental studies to improve understanding of biogeochemical and physical processes, and development of models appropriate for hydrological and ecological conditions.

Cross-continental importance of CH4 emissions from dry inland-waters

Despite substantial advances in quantifying greenhouse gas (GHG) emissions from dry inland waters, existing estimates mainly consist of carbon dioxide (CO2) emissions. However, methane (CH4) may also be relevant due to its higher Global Warming Potential (GWP). We report CH4 emissions from dry inland water sediments to i) provide a cross-continental estimate of such emissions for different types of aquatic systems (i.e., lakes, ponds, reservoirs, and streams) and climate zones (i.e., tropical, continental, and temperate); and ii) determine the environmental factors that control these emissions. CH4 emissions from dry inland waters were consistently higher than emissions observed in adjacent uphill soils, across climate zones and in all aquatic systems except for streams. However, the CH4 contribution (normalized to CO2 equivalents; CO2-eq) to the total GHG emissions of dry inland waters was similar for all types of aquatic systems and varied from 10 to 21%. Although we discuss multiple controlling factors, dry inland water CH4 emissions were most strongly related to sediment organic matter content and moisture. Summing CO2 and CH4 emissions revealed a cross-continental average emission of 9.6 ± 17.4 g CO2-eq m−2 d−1 from dry inland waters. We argue that increasing droughts likely expand the worldwide surface area of atmosphere-exposed aquatic sediments, thereby increasing global dry inland water CH4 emissions. Hence, CH4 cannot be ignored if we want to fully understand the carbon (C) cycle of dry sediments.

Designing environmental DNA surveys in complex aquatic systems: Backpack sampling for rare amphibians in Sierra Nevada meadows

Abstract Surveys for environmental DNA (eDNA) can provide an efficient and effective means of detecting aquatic organisms in various types of aquatic systems. In the summer of 2017, the efficacy of a new, integrated eDNA backpack sampler to detect two native amphibians (Rana sierrae and R. cascadae) at risk was tested in complex mountain meadows in California. Samples were collected at 65 locations in 15 meadows where the target species were known to be present or were historically present. Collection and preservation of individual samples took less than 10 min on average. Environmental DNA analysis methods detected each species at all meadows with visual detections (N = 11) except one with one frog seen away from sampling sites. Bayesian multi‐scale occupancy modelling indicated that conditional detection probabilities at the sample level ranged from 0.30 (CL 0.07–0.65) at meadow heads where no frogs were observed during visual surveys to 0.93 (CL 0.77–1.00) at the meadow foot with at least one frog observed in the vicinity. Compared with visual surveys, eDNA methods more frequently detected amphibians at the sampling‐location scale. The improvement in detection using eDNA methods was most pronounced for samples collected at the downstream ends of meadows where water converges, where eDNA methods detected target species at 10 of 11 occupied meadows. These results suggest that the addition of eDNA sampling to visual surveys in mountain meadows will improve survey accuracy and increase the probability of detecting rare frogs.

Global scanning of cylindrospermopsin: Critical review and analysis of aquatic occurrence, bioaccumulation, toxicity and health hazards

Cylindrospermopsin (CYN), a cyanotoxin produced by harmful algal blooms, has been reported worldwide; however, there remains limited understanding of its potential risks to surface water quality. In the present study, we critically reviewed available literature regarding the global occurrence, bioaccumulation, and toxicity of CYN in aquatic systems with a particular focus on freshwater. We subsequently developed environmental exposure distributions (EEDs) for CYN in surface waters and performed probabilistic environmental hazard assessments (PEHAs) using guideline values (GVs). PEHAs were performed by geographic region, type of aquatic system, and matrix. CYN occurrence was prevalent in North America, Europe, and Asia/Pacific, with lakes being the most common system. Many global whole water EEDs exceeded guideline values (GV) previously developed for drinking water (e.g., 0.5 μg L−1) and recreational water (e.g., 1 μg L−1). GV exceedances were higher in the Asia/Pacific region, and in rivers and reservoirs. Rivers in the Asia/Pacific region exceeded the lowest drinking water GV 73.2% of the time. However, lack of standardized protocols used for analyses was alarming, which warrants improvement in future studies. In addition, bioaccumulation of CYN has been reported in mollusks, crustaceans, and fish, but such exposure information remains limited. Though several publications have reported aquatic toxicity of CYN, there is limited chronic aquatic toxicity data, especially for higher trophic level organisms. Most aquatic toxicity studies have not employed standardized experimental designs, failed to analytically verify treatment levels, and did not report purity of CYN used for experiments; therefore, existing data are insufficient to derive water quality guidelines. Considering such elevated exceedances of CYN in global surface waters and limited aquatic bioaccumulation and toxicity data, further aquatic monitoring, environmental fate and mechanistic toxicology studies are warranted to robustly assess and manage water quality risks to public health and the environment.

Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters.

Land-use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland and creek), offsetting measure (e.g., enhancement, restoration, and creation), and an assessment of the projects' compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.

Behavior of gray triggerfish Balistes capriscus around baited fish traps determined from fine-scale acoustic tracking

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 606:133-150 (2018) - DOI: https://doi.org/10.3354/meps12780 Behavior of gray triggerfish Balistes capriscus around baited fish traps determined from fine-scale acoustic tracking Nathan M. Bacheler1,*, Kyle W. Shertzer1, Jeffrey A. Buckel2, Paul J. Rudershausen2, Brendan J. Runde2 1Southeast Fisheries Science Center, National Marine Fisheries Service, Beaufort, North Carolina 28516, USA 2Department of Applied Ecology, Center for Marine Sciences and Technology, North Carolina State University, Morehead City, North Carolina 28557, USA *Corresponding author: nate.bacheler@noaa.gov ABSTRACT: Most reef fish surveys use bait to attract individuals to bite hooks, enter traps, or be counted on underwater video. The behavior of fish around baited gears, however, is poorly understood despite its importance for estimating catchability. We used a fine-scale acoustic positioning system to elucidate the movement behaviors of 11 telemetered gray triggerfish Balistes capriscus around 54 baited fish traps deployed at a 37 m deep site in Raleigh Bay, North Carolina, USA. Median positional error rates from a reference transmitter were 1-2 m, suggesting fish positions were accurate and precise. Overall, 104170 spatial positions were determined for gray triggerfish over the 42 d study. There were 27 instances of telemetered gray triggerfish responding to baited fish traps. These fish responded from initial distances up to 312 m (mean = 68 m) from traps and spent 4-95% (mean = 35%) of their time within 20 m of traps. Using generalized additive models, we determined that telemetered gray triggerfish were most likely to respond to baited traps when they were initially located close to (<100 m), and down-current from, baited traps. There were substantial differences in gray triggerfish responses and water clarity across the 3 recapture periods, suggesting gray triggerfish use vision, olfaction, and perhaps sound to locate bait. Our modeling approach is general, and could be used to quantify the behavior of myriad organisms around sampling gears in various types of aquatic systems. KEY WORDS: Animal behavior · Bait · Telemetry · Vemco positioning system · Movement · Baited remote underwater video station · BRUVS · Trap · Reef Full text in pdf format PreviousNextCite this article as: Bacheler NM, Shertzer KW, Buckel JA, Rudershausen PJ, Runde BJ (2018) Behavior of gray triggerfish Balistes capriscus around baited fish traps determined from fine-scale acoustic tracking. Mar Ecol Prog Ser 606:133-150. https://doi.org/10.3354/meps12780 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 606. Online publication date: November 15, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

A comparison of the larvivorous habits of exotic Poecilia reticulata and native Aplocheilus parvus

BackgroundThe exotic fish Poecilia reticulata is promoted in the tropics as a biological control agent for aquatic pathogenic carriers, such as mosquitoes. Such control measures are often adopted blindly, ignoring the potential of native species and the adverse effects of introduced species. The present study was conducted to assess the diet composition of two species of fish, the native Aplocheilus parvus and exotic P. reticulata, and to assess the availability of food items in their natural environment in four types of aquatic systems. Diet composition was estimated using 24 h gut contents analysis, in a clay quarry pit and a perennial reservoir for A. parvus, and in a man-made canal and a second-order natural stream for P. reticulata. Food items in these environments were quantified by analyzing water samples collected every 2 h.ResultsThe diet of A. parvus in the clay quarry pit and reservoir consisted of adult or larval stages of Insecta, Maxillopoda and Malacostraca. In both habitats, A. parvus selectively fed on insect parts and insect larvae. The diet of P. reticulata consisted of filamentous algae, diatoms and detritus. The diet of A. parvus showed active selection of insectivore food items against their low availability. In contrast, the diet of P. reticulata showed consumption of food items in accordance with their availability in the environment. The highest mean number of food items in the gut for A. parvus was recorded around mid-day in the clay quarry pit, but no peak feeding time was identified in the perennial reservoir. For P. reticulata, peak feeding was recorded around mid-day in both the habitats.ConclusionIrrespective of the type of environment and rate of occurrence, A. parvus preferred insect and insect larvae, whereas P. reticulata consumed the most readily available food items. The active selection of insects by A. parvus suggests they may have value as a biological control agent.

Applying High-Resolution Imagery to Evaluate Restoration-Induced Changes in Stream Condition, Missouri River Headwaters Basin, Montana

Degradation of streams and associated riparian habitat across the Missouri River Headwaters Basin has motivated several stream restoration projects across the watershed. Many of these projects install a series of beaver dam analogues (BDAs) to aggrade incised streams, elevate local water tables, and create natural surface water storage by reconnecting streams with their floodplains. Satellite imagery can provide a spatially continuous mechanism to monitor the effects of these in-stream structures on stream surface area. However, remote sensing-based approaches to map narrow (e.g., &lt;5 m wide) linear features such as streams have been under-developed relative to efforts to map other types of aquatic systems, such as wetlands or lakes. We mapped pre- and post-restoration (one to three years post-restoration) stream surface area and riparian greenness at four stream restoration sites using Worldview-2 and 3 images as well as a QuickBird-2 image. We found that panchromatic brightness and eCognition-based outputs (0.5 m resolution) provided high-accuracy maps of stream surface area (overall accuracy ranged from 91% to 99%) for streams as narrow as 1.5 m wide. Using image pairs, we were able to document increases in stream surface area immediately upstream of BDAs as well as increases in stream surface area along the restoration reach at Robb Creek, Alkali Creek and Long Creek (South). Although Long Creek (North) did not show a net increase in stream surface area along the restoration reach, we did observe an increase in riparian greenness, suggesting increased water retention adjacent to the stream. As high-resolution imagery becomes more widely collected and available, improvements in our ability to provide spatially continuous monitoring of stream systems can effectively complement more traditional field-based and gage-based datasets to inform watershed management.

Variaciones entre especies de anfibios en sus respuestas morfológicas a la presencia de depredadores nativos e introducidos

Vazquez, L.A., Rendon, M.A., Diaz-Paniagua, C., Gomez-Mestre, I. 2017. Among-species variation in the morphological responses of larval amphibians to native and invasive species. Ecosistemas 26(3): 32-38. Doi.: 10.7818/ECOS.2017.26-3.05 Amphibian larvae are common prey to various types of predators, according to the type of aquatic system they develop in. When they detect water-borne chemical cues from predators (kairomones), amphibian larvae often produce inducible defenses. An important component of such defenses is the alteration of the shape of the larvae, which often consists in producing rounder bodies, shorter tails and deeper tail fins in the presence of predators. However, the activation of these inducible defenses critically depends on the accurate recognition of predator cues. In that context, the human introduction of alien predators with whom local prey species have not shared a joint evolutionary history may pose a grave threat in part because the native prey may fail to recognize the cues of the novel predators and hence fail to trigger the corresponding antipredator phenotype. In this study we analyze the morphological responses of larvae of four amphibian species to two different types of predators: native dragonfly larvae and introduced red-swamp crayfish. We find that three out of the four species readily respond altering their morphology to the presence of dragonflies, but they all fail to respond to introduced crayfish. Moreover, the effect size of the morphological response seems to be congruent with the duration of the larval period of each species so that faster developing species show lesser responses to dragonflies whereas slower developing species show greater responses to them. This is congruent with faster developing species occupying temporary or even ephemeral ponds which typically have lower predator abundance.

Manned submersible „JAGO“

The manned submersible „JAGO“ is a human occupied underwater vehicle (HOV) designed for personal exploration and research in all types of aquatic systems and habitats. The seafloor along the continental shelf and slopes within the ocean twilight zone is JAGO’s main target area. The DNV-GL classed 2-person submersible has a maximum operating depth of 400 m. The two occupants, the pilot and one observer, are seated at 1 Atmosphere in a steel pressure hull with two large acrylic windows. The submersible’s small size and lightweight construction (3 T) allows worldwide operations from on board a wide variety of vessels as well as transport in a single standard 20-foot container together with all support equipment. Typical applications include personal observation of the sea bed and water column, video and photo documentation, selective non-intrusive sampling, placement of sensors and experiments, underwater inspection, as well as location and recovery of objects

Ecosystem classification and mapping of the Laurentian Great Lakes

Owing to the enormity and complexity of the Laurentian Great Lakes, an ecosystem classification is needed to better understand, protect, and manage this largest freshwater ecosystem in the world. Using a combination of statistical analyses, published knowledge, and expert opinion, we identified key driving variables and their ecologically relevant thresholds and delineated and mapped aquatic systems for the entire Great Lakes. We identified and mapped 77 aquatic ecological units (AEUs) that depict unique combinations of depth, thermal regime, hydraulic, and landscape classifiers. Those 77 AEU types were distributed across 1997 polygons (patches) ranging from 1 to &gt;48 000 km2in area and were most diverse in the nearshore (35 types), followed by the coastal margin (26), and then the offshore (16). Our classification and mapping of ecological units captures gradients that characterize types of aquatic systems in the Great Lakes and provides a geospatial accounting framework for resource inventory, status and trend assessment; research for ecosystem questions; and management and policy-making.

Factors influencing herpetofaunal assemblages of aquatic systems in a managed pine forest

Although >12 million ha of southeastern United States are intensively managed pine forest, we have little understanding of biological contributions of aquatic systems embedded in pine plantations. Further, the influence surrounding forest stand structure on assemblages of wetland-associated species in managed forests are poorly understood. To address these gaps, we investigated herpetofaunal assemblages across three ephemeral aquatic system types [unaltered sites (n=16), altered sites (n=18), and roadside ditches (n=19)] embedded in an intensively managed pine landscape in eastern North Carolina, USA. These aquatic systems varied in their disturbance intensity and landscape context. Unaltered sites were avoided by silvicultural activities (set aside), altered sites were actively managed as part of the surrounding plantation, and ditches received maintenance as part of routine forest management. We examined amphibian and reptile species richness and assemblage composition at 53 aquatic sites surrounded by early-, middle-, or late-rotation aged pine plantations. During January–July 2013 and January–June 2014, we detected 34 amphibian and reptile species with visual encounter, dipnet, and call surveys at aquatic sites. We estimated species richness and used Analysis of Similarity to assess differences in species richness and assemblage structure by aquatic system type and stand age class. Amphibian species richness was greatest in unaltered and altered sites but was similar among stand age classes. Reptile species richness was similar among aquatic system types and stand age classes. Analysis of Similarity results revealed that amphibian assemblages were similar among stand age classes but were significantly different among all aquatic systems. Reptile assemblages also were similar among stand age classes but differed between altered sites and roadside ditches. Differences between richness and assemblage results may have been related to low detections of reptiles because our non-metric multi-dimensional scaling analysis, which only included species with >1 detection, revealed less obvious differences among reptile assemblages by aquatic system type. Despite dramatic variation in disturbance intensity and site-level environmental metrics, we did not find distinct herpetofaunal assemblages among aquatic system types or stand age classes. Our results suggest that aquatic systems in reconfigured landscapes not only support a range of herpetofaunal species, but that amphibian and reptile assemblages are similar across system types.

Anuran occupancy and breeding site use of aquatic systems in a managed pine landscape

Although the southeastern United States has >12million ha of intensively managed pine forest, we have a poor understanding of how aquatic systems embedded in managed landscapes contribute to biodiversity. Further, the influence of local- and landscape-scale environmental factors on occupancy of aquatic habitat types by wetland-breeding species in managed forests is unclear. Thus, we investigated anuran occupancy across three ephemeral aquatic system types (altered sites, unaltered sites, and roadside ditches) embedded in an intensively managed pine landscape in eastern North Carolina, USA. These aquatic systems varied in management, disturbance intensity, and landscape context. Altered sites are actively managed as part of the surrounding plantation, unaltered sites are avoided by silvicultural activities (set aside), and ditches receive maintenance as part of routine forest management. We examined occupancy of anuran species at 53 aquatic sites surrounded by early-, mid-, or late-rotation aged stands. During January–July 2013–2014, we conducted repeated call surveys for anurans at aquatic sites and detected 14 species. We used single-species, multi-season occupancy models to examine associations between species occupancy and site- and landscape-scale habitat characteristics for 9 commonly encountered anurans as a function of aquatic system type and stand age class while accounting for imperfect detection. Detection probabilities by species ranged from 0.27 to 0.53 and increased seasonally through the year for most anurans. Species occupancy ranged in 2013 from 0.28 to 0.81 and in 2014 from 0.33 to 0.82. Species occupancy varied by aquatic system type, but the stand age surrounding an aquatic site had little effect on occupancy for most anurans we modeled. Our results indicate that local-scale factors commonly had a larger influence than landscape context on anuran occupancy. We detected evidence of breeding across all aquatic systems and stand age classes, suggesting at least a subset of species are calling and reproductively active. Our study highlights how novel landscape structure and reconfigured ephemeral aquatic systems embedded in intensively managed forests can support anuran occupancy across a range of disturbance intensities.

Microbial Changes in the Fluorescence Character of Natural Organic Matter from a Wastewater Source

Natural Organic Matter (NOM) is a mixture of aromatic and aliphatic organic compounds of natural origin in any type of aquatic system. Human activities impact the constituents of NOM, from its production to its fate, particularly in the treatment of domestic waste waters. In this work, the impact of microorganisms isolated from a Waste Water Treatment Plant (WWTP) was investigated to determine the fate of NOM fractions in raw sewage, using fluorescence spectroscopy. Wastewater samples were taken at three different times from a WWTP, and incubated for 4 days under two treatments: 1) “raw sewage”, and 2) “spiked”, i.e., the same raw sewage, spiked with bacteria previously isolated from the WWTP. The incubated waters were analyzed by fluorescence spectroscopy, digitally resolved into NOM components: humic- and fulvic-like, and two types of protein-like, i.e., tryptophan- and tyrosine-like, using a Parallel Factor Analysis routine (PARAFAC). The results demonstrate that the “spiked” samples showed the largest changes with incubation time. The signals of the tryptophan- and tyrosine-like components decreased, suggesting a net microbial digestion of proteinaceous material. In contrast, the fulvic-like signals, and to some extent, the humic-like signals increased, suggesting the production of the associated molecular materials during the incubation period. This study provides direct evidence of human impact on the make-up of NOM: the cultures of microbes found at a WWTP consume the proteinaceous material, whereas humic-like and fulvic-like materials are produced.

Modern to millennium-old greenhouse gases emitted from ponds and lakes of the Eastern Canadian Arctic (Bylot Island, Nunavut)

Abstract. Ponds and lakes are widespread across the rapidly changing permafrost environments. Aquatic systems play an important role in global biogeochemical cycles, especially in greenhouse gas (GHG) exchanges between terrestrial systems and the atmosphere. The source, speciation and emission rate of carbon released from permafrost landscapes are strongly influenced by local conditions, hindering pan-Arctic generalizations. This study reports on GHG ages and emission rates from aquatic systems located on Bylot Island, in the continuous permafrost zone of the Eastern Canadian Arctic. Dissolved and ebullition gas samples were collected during the summer season from different types of water bodies located in a highly dynamic periglacial valley: polygonal ponds, collapsed ice-wedge trough ponds, and larger lakes. The results showed strikingly different ages and fluxes depending on aquatic system types. Polygonal ponds were net sinks of dissolved CO2, but variable sources of dissolved CH4. They presented the highest ebullition fluxes, 1 or 2 orders of magnitude higher than from other ponds and lakes. Trough ponds appeared as substantial GHG sources, especially when their edges were actively eroding. Both types of ponds produced modern to hundreds of years old (&lt; 550 yr BP) GHG, even if trough ponds could contain much older carbon (&gt; 2000 yr BP) derived from freshly eroded peat. Lakes had small dissolved and ebullition fluxes, however they released much older GHG, including millennium-old CH4 (up to 3500 yr BP) from lake central areas. Acetoclastic methanogenesis dominated at all study sites and there was minimal, if any, methane oxidation in gas emitted through ebullition. These findings provide new insights on GHG emissions by permafrost aquatic systems and their potential positive feedback effect on climate.

Abiotic variability among different aquatic systems of the central Amazon floodplain during drought and flood events.

This paper examines water properties from lakes, (depression lakes, sensu Junk et al., 2012), channels (scroll lakes with high connectivity, sensu Junk et al., 2012) and paleo-channels (scroll lakes with low connectivity-sensu Junk et al., 2012, locally called ressacas) located in Mamirauá Sustainable Development Reserve, in Central Amazon floodplain, Amazonas, Brazil. We analysed surface temperature, conductivity, pH, dissolved oxygen, turbidity, transparency, suspended inorganic and organic matter, chlorophyll-a, pheophytin, total nitrogen, total phosphorus, organic and inorganic carbon in 2009 high water phase, 2009 and 2010 low water phases. Multivariate statistical analyses of 24 aquatic systems (6 ressacas, 12 lakes and 6 channels, 142 samples) were applied to the variables in order to: 1) quantify differences among aquatic system types; 2) assess how those differences are affected in the different phases of the hydrological year. First, we analysed the entire set of variables to test for differences among phases of the hydrological year and types of aquatic systems using a PERMANOVA two-way crossed design. The results showed that the all measured limnological variables are distinct regarding both factors: types of aquatic systems and hydrological phases. In general, the magnitude and amplitude of all variables were higher in the low water phase than in the high water phase, except for water transparency in all aquatic system's types. PERMANOVA showed that the differences between aquatic system's types and hydrological phases of all variables were highly significant for both main factors (type and phase) and for the type x phase interaction. Limnological patterns of Amazon floodplain aquatic systems are highly dynamic, dependent on the surrounding environment, flood pulse, main river input and system type. These patterns show how undisturbed systems respond to natural variability in such a diverse environment, and how distinct are those aquatic systems, especially during the low water phase. Aquatic systems in Mamirauá floodplain represent limnological patterns of almost undisturbed areas and can be used as future reference for comparison with disturbed areas, such as those of the Lower Amazon, and as a baseline for studies on the effects of anthropogenic influences and climate change and on Amazon aquatic ecosystem.

First record of Lopescladius Oliveira, 1967 (Chironomidae: Orthocladiinae) in the Piranhas-Açu River basin, Brazil, with ecological notes on its habitat use

The present study describes a new site of occurrence for the genus Lopescladius in Brazil and reports the first record for the Piranhas-Açu River basin, in the state of Rio Grande do Norte, northeastern Brazil. This new occurrence expands the distribution of the genus and adds to the knowledge of the chironomid fauna. The presence of this genus in an intermittent stream highlights the importance of future research on this type of aquatic system as well as ecological aspects related to Lopescladius.

Environmental determinants of leech assemblage patterns in lotic and lenitic habitats

Leeches (Clitellata: Hirudinida) are abundant predators or ecto-parasites inhabiting various freshwater habitats; however many biotic and abiotic drivers of their assemblage patterns have been deduced rather than directly tested. To study species richness and composition changes in leech assemblages, 109 sites of running and stagnant water bodies were sampled in three regions of the Czech Republic in 2007–2010, together with several explanatory variables that are known or expected to be important predictors of leech distribution. In total, 17 species of leeches were recorded, varying between 0–7 and 0–9 species in lotic and lenitic sites, respectively. These differences in species richness of lotic and lenitic sites were highly significant, contrary to the abundances, which varied between 0–283 and 0–295 individuals. The main change in species composition was controlled by water temperature and morphological characteristics (e.g. substrate and cover of macrophytes), mostly reflecting the differences between lotic and lenitic habitats. We found the density of benthos (i.e. prey availability) to be the best predictor of species composition in both lotic and lenitic sites, together with the percentage of canopy cover. However, the other significant predictors (i.e. the substrate and water conductivity found to be significant in lotic sites, and the mean annual temperature and PO 4 3− in lenitic sites), differed between these habitats. Other than mean annual temperature and water temperature, which had different effects on species richness in lotic and lenitic sites, there were no other differences between lotic and lenitic sites in terms of how species richness and abundance responded to all other analyzed predictors. Our results stress the importance of prey availability and canopy for leech distribution patterns. Differences in the significant predictors of leech assemblage patterns between lotic and lenitic sites raise fundamental questions about the underlying mechanisms and ecological constraints to leech distribution in these main types of aquatic systems.

Changing restoration rules: Exotic bivalves interact with residence time and depth to control phytoplankton productivity

Non‐native species are a prevalent ecosystem stressor that can interact with other stressors to confound resource management and restoration. We examine how interactions between physical habitat attributes and a particular category of non‐native species (invasive bivalves) influence primary production in aquatic ecosystems. Using mathematical models, we show how intuitive relationships between phytoplankton productivity and controllable physical factors (water depth, hydraulic transport time) that hold in the absence of bivalves can be complicated—and even reversed—by rapid bivalve grazing. In light‐limited environments without bivalves, shallow, hydrodynamically “slow” habitats should generally have greater phytoplankton biomass and productivity than deeper, “faster” habitats. But shallower, slower environments can be less productive than deeper, faster ones if benthic grazing is strong. Moreover, shallower and slower waters exhibit a particularly broad range of possible productivity outcomes that can depend on whether bivalves are present. Since it is difficult to predict the response of non‐native bivalves to habitat restoration, outcomes for new shallow, slow environments can be highly uncertain. Habitat depth and transport time should therefore not be used as indicators of phytoplankton biomass and production where bivalve colonization is possible. This study provides for ecosystem management a particular example of a broad lesson: abiotic ecosystem stressors should be managed with explicit consideration of interactions with other major (including biotic) stressors. We discuss the applicability and management implications of our models and results for a range of aquatic system types, with a case study focused on the Sacramento‐San Joaquin Delta (California, USA). Simple mathematical models like those used here can illuminate interactions between ecosystem stressors and provide process‐based guidance for resource managers as they develop strategies to augment valued populations, restore habitats, and manipulate ecosystem functions.