Surface Water Habitats Research Articles

Flexible migration and habitat use strategies of an endangered waterbird during hydrological drought

AbstractWildlife species confront threats from climate and land use change, exacerbating the influence of extreme climatic events on populations and biodiversity. Migratory waterbirds are especially vulnerable to hydrological drought via reduced availability of surface water habitats. We assessed how whooping cranes (Grus americana) modified habitat use and migration strategies during drought to evaluate their resilience to changing conditions and adaptive capacity. We categorized >8000 night‐roost sites used by 146 cranes from 2010 to 2022 and examined relative use during non‐drought, moderate drought, and extreme drought conditions. We found cultivated and uncultivated palustrine and lacustrine wetlands were generally used less during droughts than non‐drought conditions. Conversely, impounded palustrine and lacustrine systems and rivers served more frequently as drought refugia (i.e., used more during drought than non‐drought conditions). Night roosts occurred primarily on private lands (86% overall); public land use decreased with latitude and increased with drought severity, with greatest use (56%) occurring during severe autumn drought in the southern Great Plains. Quantifying use of identified critical habitats in the United States indicated that Cheyenne Bottoms State Waterfowl Management Area and Quivira National Wildlife Refuge were used less during drought, and the Central Platte River and Salt Plains National Wildlife Refuge received similar use during drought compared to non‐drought conditions. Our findings provide insights into compensatory use of habitats, where impounded surface water may function in a complementary fashion with natural wetlands. Collectively, these and other types of wetlands distributed across the migration corridor provided a reliable network of habitat available across the Great Plains. A diversity of wetlands available during variable environmental conditions would be useful in supporting continued recovery of whooping cranes and likely have benefits for a wide array of migratory birds.

Using Springs as Sentinels of Climate Change in Nature Parks North and South of the Alps: A Critical Evaluation of Methodological Aspects and Recommendations for Long-Term Monitoring

Spring ecosystems are diverse transition zones between ground- and surface-water habitats. Due to their characteristics and vulnerable species assemblages, springs are considered indicator systems for monitoring environmental change. In particular, climate change is expected to alter spring-ecosystem features, such as water temperature and discharge, affecting otherwise typically stable biotic and abiotic conditions. However, reliable trend-development recognition and analysis require a uniform methodology and comparable data series over long periods of time. Spring research findings in the Berchtesgaden National Park and the Adamello-Brenta Nature Park have been consolidated to develop methodological recommendations to create lasting societal-added value. The successful transfer of the methodology to the Bavarian Forest National Park and the experienced contribution of the Bavarian Association for the Protection of Nature (Bavarian Climate Alliance) strongly improved method validations. Our resulting, newly developed recommendations for long-term spring monitoring have a focus on climate change impacts and aim at providing a decision-making basis for establishing programs in similar ecological and climatic zones. Uniform site-selection criteria and selected climate-sensitive parameters are indicated. This includes documenting the spring’s environment and structure, measuring abiotic parameters, and determining selected floristic and faunistic groups. We recommend measurement and sampling-survey intervals ranging from 3(4) times yearly to every 5 years, depending on the parameter. We further suggest a database system that integrates all monitoring parameters to ensure consistent data management and storage. Analysing the data resulting from our new holistic spring monitoring methodology should provide critical knowledge about putatively changing ecosystems that can then be used as evidence of climate-change impact on spring ecosystems.

First observations and early life-history aspects of lake rearing galaxiid larvae in the lower Waikato River Basin, New Zealand

ABSTRACT Larval behaviour for many of New Zealand’s diadromous freshwater fish is inadequately described. Diadromy for many amphidromous species is not obligatory however, and where conditions are suitable, freshwater larval rearing may be facilitated. Where this occurs in lakes, opportunities to document the composition and conditions supporting larval rearing exist. Boat trawling was undertaken across nine lowland lakes in the Lower Waikato over four consecutive winters with a focus on larval galaxiids. Galaxiid larvae were captured in surface water habitats in all but one lake, with banded kōkopu (Galaxias fasciatus) and giant kōkopu (Galaxias argenteus) the most common species detected. One lake, Lake Waahi, consistently resulted in the most galaxiid captures for effort expended. Analyses of larvae from this and other lakes indicated that two sizes predominated in catches and that larger, older larvae were predominantly G. fasciatus while smaller, younger larvae were predominantly G. argenteus. Stomach contents indicated that two non-native zooplankton species predominated in the diet of larvae, the Holarctic daphnia, Daphnia galeata, and the Australian calanoid copepod Boeckella symmetrica. This study provides new information regarding the timing, movement and predicted recruitment of native fish species in this river basin that has important implications for lake and river management.

Study of physicochemical and statistical analysis of water quality parameters in Veeranam Lake, Cuddalore district, Tamil Nadu, India

Lakes are one of the most biologically diverse and productive inland surface water habitats. Insanitary due to the integration of a drainage system and its surplus flow into lakes is the foremost origin of lake water contamination. This research aimed to figure out how to apply statistical approaches like the systematic correlation coefficient and cluster analysis. We choose water quality testing of Veeranam Lake in Cuddalore, Tamil Nadu District, to investigate water quality for public use, restoration, and other objectives. From August 2018 to July 2019, water samples were collected from 6 locations using varied seasonal incidence at three months intervals. Because of the influence of domestic and Environmental factors in the catchment areas, we found a perfect positive relationship between Total Dissolved Solids Vs. Conductivity, COD Vs. BOD, Copper Vs. BOD and Total Chromium Vs. cadmium. And the Turbidity, Ortho phosphates, Total Dissolved Oxygen, Biological oxygen demand, chemical oxygen demand, Iron, Lead were not within the permissible limit as described by the Indian traditional value.

Aquatic habitat changes within the channelized and impounded Arkansas River, Arkansas, USA

AbstractRiver‐wide changes in morphologic character following channelization and impoundment alter the occurrence and distribution of surface water and available habitats for aquatic organisms. Quantifying patterns of creation, redistribution or disappearance of habitats at river‐wide and decadal spatiotemporal scales can promote understanding regarding trajectories of different habitat types following alteration and prospects of direct habitat enhancement projects within altered alluvial rivers. Newly available remote‐sensing tools and databases may improve detection of river‐wide changes in habitat through time. We used a combination of remote‐sensing data and generalized linear models to assess changes in surface water coverage from 1984 to 2015 among aquatic habitats of 496 km of the Arkansas River within Arkansas, USA. Changes through time in surface area of permanent and episodically inundated areas — and thus the availability of aquatic habitat — were variable along the river. Overall, the river lost a total 2.1% of permanent and 12.1% of episodic water surface area. The general trend of loss of off‐main‐channel habitat and increased coverage of permanent water along main‐channel habitats may indicate a long‐term transition (i.e. ramp‐type disturbance) within areas of the Arkansas River where backwaters are transitioning to terrestrial environments, and habitat heterogeneity in the main channel is decreasing. As such, a decadal‐scale change of channel form and backwater habitats may be the dominant pattern with limited regeneration of diverse habitat types. Understanding changes to permanent and episodic water availability may aid predictions regarding ecological effects of channelization and impoundments, including both increases and decreases in riverine productivity, biotic diversity and population abundances through space and time. Water resource managers and biologists can use information regarding river‐wide changes in habitat availability obtained through remote sensing data to direct river management practices, including dredging and side‐channel construction, and to assess ecological responses to such changes.

Sublethal neurotoxicity of organophosphate insecticides to juvenile coho salmon

For decades, organophosphate (OP) insecticides have been used as chemical control agents in watersheds that support at-risk populations of Pacific salmon throughout western North America. Spray drift, runoff, and other processes transport OPs to critical surface water habitats for migratory salmonids. While most OPs share a common mechanism of action (i.e., inhibition of neuronal acetylcholinesterase, or AChE), they typically vary in toxic potency. Moreover, dose-response relationships for exposure and sublethal neurotoxicity (e.g., brain AChE inhibition) in salmonids have not been defined for many OPs. Here we exposed juvenile coho salmon (Oncorhynchus kisutch) to five common anticholinesterase insecticides (dimethoate, ethoprop, naled, phorate and phosmet) that are widely used on agricultural, commercial, residential, and public lands. Each of the five pesticides produced a concentration-dependent inhibition of AChE enzyme activity. The effective concentration for 50 % AChE inhibition (96-hr EC50) indicated the highest toxicity for phorate (EC50 = 0.57 μg/L) followed by phosmet (3.3 μg/L), naled (7.8 μg/L), ethoprop (90.6 μg/L) and dimethoate (273 μg/L). These findings can inform 1) relative hazard analyses for OP use near sensitive aquatic habitats, 2) predictions of sublethal OP mixture toxicity, and 3) ecological risk assessments for threatened or endangered species of Pacific salmon.

Flow intermittence in river networks: understanding the ecohydrological diversity of aquatic–terrestrial ecosystems

Temporary streams comprise dynamic mosaics of lotic, lentic and terrestrial habitats and dominate global river networks, occurring across regions with contrasting climate types. Recent advances in our ecohydrological understanding of temporary streams have focused on systems in arid, semi-arid and mediterranean climates. In this special issue, we present new temporary stream research from underrepresented regions, primarily cool, wet temperate climates but also continental central Europe and the mediterranean-climate region of South Africa. We bring together observational case studies, laboratory experiments, and field surveys spanning surface water and groundwater habitats. Papers within the special issue explore ecological responses to flow intermittence; examine biodiversity patterns of rare and endemic species at broad spatial scales; characterize diverse responses to drying events within and among populations; demonstrate the value of long-term observational data in understanding the hydrological drivers that underpin biotic responses; and present opportunities to improve temporary stream monitoring and management. Collectively, these contributions complement dryland research to advance global understanding of temporary stream ecohydrology. However, the terrestrial communities that inhabit dry channels remain a notable research gap, which we address in a review of global literature. As global change causes an increase in their extent across climate regions, we urge researchers and stakeholders to collaborate to implement recommendations that address the challenges associated with the effective management of temporary streams as aquatic–terrestrial ecosystems.

Transboundary Environmental Governance across the World's Largest Border ed. by Stephen Brooks and Andrea Olive

Reviewed by: Transboundary Environmental Governance across the World's Largest Border ed. by Stephen Brooks and Andrea Olive Paul Todhunter Transboundary Environmental Governance across the World's Largest Border. Edited by Stephen Brooks and Andrea Olive. Winnipeg: University of Manitoba Press, 2018. vii + 248 pp. Map, tables, contributors, index. C$39.95 paper. Transboundary environmental governance concerns management of resources where "manmade boundaries . . . have been inserted against nature's will." The book provides a significant contribution to a growing literature on transboundary governance along the Canada–United States border. This international border, the world's longest border, contains 20% of the available global fresh surface water, shares numerous and diverse habitats, possesses rich and varied natural resources, and is populated by peoples with close economic ties, parallel histories, and common cultural roots. Important differences also exist, however, that lead to divergence and conflict in transboundary governance. The aim of the editors is "to help us better understand the issues, processes, and challenges that characterize transboundary environmental governance between Canada and the United States." They asked volume contributors to describe the state of existing relationships, governance structures, and processes of transboundary governance, to assess the adequacy of these structures with respect to environmental impacts, and to evaluate opportunities for reform, improved outcomes, and successful accommodation of emerging environmental concerns. The editors have splendidly met these aims. I was most impressed by the coherence of the entire volume, and how each individual chapter made a significant contribution to the whole. Each contributor focused on the editors' aims, provided an entry of similar length and depth, presented interesting case histories, and addressed common themes. Contributors had access to drafts of other chapters, and often referenced points made in other parts of the book. The volume has none of the disjointedness that can characterize edited multi-author volumes. Most chapters share a common structure, with a summary introduction, a historical perspective on the development of environmental governance, a development of those initial structures to accommodate the increasing complexity of environmental and human affairs, and selected case histories. The volume is organized along a geographical gradient cross-cut by major resource types. The editors first provide a lengthy preface that summarizes each contribution. The first chapter reviews the International Joint Commission that grew out of the Boundary Waters Treaty of 1909 and formed the basis of early Canada–United States transboundary governance, but is now overshadowed by multilayered regional agreements of varied types. The next three chapters examine the Great Lakes Basin, each focusing on a different environmental issue: water quantity, water storage, and river navigation; fisheries management; and water quality and pollution. The fifth chapter, on the Prairie Region, will be of greatest interest to this journal's readers. A historical prioritization of economic development led to full allocation of water rights in a region of scarce and unreliable water resources, but now faces challenges from new voices advocating for environmental conservation and sustainability. The St. Mary, Milk, and Souris river basins are the focus of the chapter, a decision for which rational support is given. The omission of the Red River of the North Basin is disappointing, however, given its unique properties and regional importance. A chapter on the Pacific West and two chapters on energy governance follow that are also highly relevant to the Great Plains. Here, in a unique twist, Canada has been the driver for resource development, and the US has been more resistant in its approach to resource development. The final chapter summarizes lessons learned, and looks forward to new challenges posed by invasive species, climate change, and development of the Arctic. Numerous themes emerge from the individual chapters. Multilayered governance has developed with a sharing of power between national, subnational, regional, and local levels of administration. New actors now bring their voices to the governance table, including environmentalists, nongovernmental organizations, and Indigenous, First Nation, and tribal peoples. The early dominance of economic development interests has broadened to consider environmental quality, habitat conservation, and sustainability perspectives. Common-pool resources require different governance structures and approaches depending upon the symmetry or asymmetry of regional benefits and costs of resource development. Transboundary governance has grown in complexity, often leading to institutional...

Observations of amphibian, reptile and some mammal species in the area of Šaleška jezera near Velenje during the 2015–2017 period

In this contribution we present our observations of amphibians, reptiles and some mammals from the area of Šaleška jezera (lakes) near Velenje in northern Slovenia. This area refers to three lakes – Velenjsko jezero, Šoštanjsko jezero and Škalsko jezero, which were formed in the 20th century as a consequence of underground lignite mining. The landscape is still changing due to an ongoing subsidence of the valley caused by continuous mining, which constantly affects the surface water bodies and habitats. The changes are so apparent that they could be measured in weeks if not days. New records on the occurrence of 9 amphibian, 7 reptilian and 9 mammalian species were made in the region during our field work carried out from 2015 to 2017. Three of these species are listed on Annex II of the EU Habitats Directive – Emys orbicularis, Bombina variegata and Triturus carnifex, and additional eight on Annex IV of this directive – Bombina variegata, Hyla arborea, Rana dalmatina, Triturus carnifex, Emys orbicularis, Lacerta viridis, Podarcis muralis and Natrix tessellata. We also recorded two introduced species – Dama dama and Trachemys scripta.

Impact of extreme drought and incentive programs on flooded agriculture and wetlands in California's Central Valley.

BackgroundBetween 2013 and 2015, a large part of the western United States, including the Central Valley of California, sustained an extreme drought. The Central Valley is recognized as a region of hemispheric importance for waterbirds, which use flooded agriculture and wetlands as habitat. Thus, the impact of drought on the distribution of surface water needed to be assessed to understand the effects on waterbird habitat availability.MethodsWe used remote sensing data to quantify the impact of the recent extreme drought on the timing and extent of waterbird habitat during the non-breeding season (July–May) by examining open water in agriculture (rice, corn, and other crops) and managed wetlands across the Central Valley. We assessed the influence of habitat incentive programs, particularly The Nature Conservancy’s BirdReturns and The Natural Resources Conservation Service’s Waterbird Habitat Enhancement Program (WHEP), at offsetting habitat loss related to drought.ResultsOverall, we found statistically significant declines in open water in post-harvest agriculture (45–80% declines) and in managed wetlands (39–60% declines) during the 2013–2015 drought compared to non-drought years during the period of 2000–2011. Crops associated with the San Joaquin Basin, specifically corn, as well as wetlands in that part of the Central Valley exhibited larger reductions in open water than rice and wetlands in the Sacramento Valley. Semi-permanent wetlands on protected lands had significantly lower (39–49%) open water in the drought years than those on non-protected lands while seasonal wetlands on protected lands had higher amounts of open water. A large fraction of the daily open water in rice during certain times of the year, particularly in the fall for BirdReturns (61%) and the winter for WHEP (100%), may have been provided through incentive programs which underscores the contribution of these programs. However, further assessment is needed to know how much the incentive programs directly offset the impact of drought in post-harvest rice by influencing water management or simply supplemented funding for activities that might have been done regardless.DiscussionOur landscape analysis documents the significant impacts of the recent extreme drought on freshwater wetland habitats in the Central Valley, the benefits of incentive programs, and the value of using satellite data to track surface water and waterbird habitats. More research is needed to understand subsequent impacts on the freshwater dependent species that rely on these systems and how incentive programs can most strategically support vulnerable species during future extreme drought.

Effect of vegetative filter strips on the dynamics of E. coli biofilm-building potential and expression of virulence factors at Mau, Kenya

Escherichia coli (E. coli) populations could become tolerant to extreme environmental temperatures to become resident in soil and surface water habitats creating public health problems. The objective of this study was to understand the interaction between dynamics of E. coli genetic diversity, physiology, and vegetative filter strips (VFS) in overland flows and soil habitats. Pulse-field gel electrophoresis was used to establish the genetic diversity of the isolates (n = 4). Genotypic analysis showed that the runoff isolates do not form a single genetic strain, but that multiple genotype strains were capable of surviving and proliferating in these habitats. High overall unique genotypic diversity was observed in VFS II (38.5%) as compared to VFS III (9.5%) and VFS I (1.5%). Approximately 8.5% E. coli genotypes observed in the surface water and 5.5% observed in soil habitat were shared between different sampling sites, suggesting diffuse sources of E. coli in these habitats. Approximately 32.5% genotypic overlap and a limited sharing (72.5%) between soil and surface water habitats were observed. These findings inferred that certain E. coli strains might have the ability to colonize and adapt to soil and runoff surface water habitats through production of biofilms. Thus, these results confirm that biofilm formation confers competitive advantage to the E. coli environmental isolates including hardiness, versatility, higher resistance to ecological and physical impacts and higher resource availability.

Surface-water dynamics and land use influence landscape connectivity across a major dryland region.

Landscape connectivity is important for the long-term persistence of species inhabiting dryland freshwater ecosystems, with spatiotemporal surface-water dynamics (e.g.,flooding) maintaining connectivity by both creating temporary habitats and providing transient opportunities for dispersal. Improving our understanding of how landscape connectivity varies with respect to surface-water dynamics and land use is an important step to maintaining biodiversity in dynamic dryland environments. Using a newly available validated Landsat TM and ETM+ surface-water time series, we modelled landscape connectivity between dynamic surface-water habitats within Australia's 1 million km2 semiarid Murray Darling Basin across a 25-yr period (1987-2011). We identified key habitats that serve as well-connected "hubs," or "stepping-stones" that allow long-distance movements through surface-water habitat networks. We compared distributions of these habitats for short- and long-distance dispersal species during dry, average, and wet seasons, and across land-use types. The distribution of stepping-stones and hubs varied both spatially and temporally, with temporal changes driven by drought and flooding dynamics. Conservation areas and natural environments contained higher than expected proportions of both stepping-stones and hubs throughout the time series; however, highly modified agricultural landscapes increased in importance during wet seasons. Irrigated landscapes contained particularly high proportions of well-connected hubs for long-distance dispersers, but remained relatively disconnected for less vagile organisms. The habitats identified by our study may serve as ideal high-priority targets for land-use specific management aimed at maintaining or improving dispersal between surface-water habitats, potentially providing benefits to biodiversity beyond the immediate site scale. Our results also highlight the importance of accounting for the influence of spatial and temporal surface-water dynamics when studying landscape connectivity within highly variable dryland environments.

Longitudinal patterns of microplastic concentration and bacterial assemblages in surface and benthic habitats of an urban river

AbstractRivers are a major source of microplastic particles (<5 mm) to oceans, but empirical measurements of microplastic movement in freshwater ecosystems are rare. The hard, buoyant surface of microplastic is a novel habitat that selects for unique microbial assemblages in rivers, especially downstream of wastewater treatment plant (WWTP) point sources. We measured microplastic in surface water and benthic habitats 50 m upstream and 50, 305, 1115, and 1900 m downstream of the effluent outfall from a large WWTP in an urban river. We used high-throughput sequencing to measure bacterial assemblages on microplastic from surface and benthic habitats and compared them to bacterial assemblages from seston, water, and sediment. Concentrations of total microplastic and microplastic types (fragment, pellet) in surface water did not change with distance downstream of the WWTP. Thus, microplastic transport showed no net deposition or resuspension. Microplastic concentrations were much higher in the benthic zone tha...

Exposure to Deepwater Horizon weathered crude oil increases routine metabolic demand in chub mackerel, Scomber japonicus

During the 2010 Deepwater Horizon incident, the continuous release of crude oil from the damaged Macondo 252 wellhead on the ocean floor contaminated surface water habitats for pelagic fish for more than 12weeks. The spill occurred across pelagic, neritic and benthic waters, impacting a variety of ecosystems. Chemical components of crude oil are known to disrupt cardiac function in juvenile fish, and here we investigate the effects of oil on the routine metabolic rate of chub mackerel, Scomber japonicus. Mackerel were exposed to artificially weathered Macondo 252 crude oil, prepared as a Water Accommodated Fraction (WAF), for 72 or 96h. Routine metabolic rates were determined pre- and post-exposure using an intermittent-flow, swim tunnel respirometer. Routine energetic demand increased in all mackerels in response to crude oil and reached statistical significance relative to unexposed controls at 96h. Chemical analyses of bile from exposed fish revealed elevated levels of fluorescent metabolites, confirming the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in the exposure WAF. The observed increase in metabolic demand is likely attributable to the bioenergetic costs of contaminant detoxification. These results indicate that short-term exposure (i.e. days) to oil has sub-lethal toxicity to mackerel and results in physiological stress during the active spill phase of the incident.

Sorption behaviours and transport potentials for selected pharmaceuticals and triclosan in two sterilised soils

Pharmaceuticals and personal care products (PPCPs) are emerging environmental pollutants, which, in addition to direct deposition processes, can find their way into surface soils through the agricultural application of sewage sludge and irrigation practices using contaminated wastewater. Therefore, it is important to assess the extent to which soils are able to retain PPCPs and to prevent their downward migration towards groundwaters. To further our understanding in this area, batch sorption experiments and artificial rainwater leaching experiments have been performed using five compounds (bezafibrate, carbamazepine, chloramphenicol, diclofenac and triclosan) possessing a range of physicochemical properties in two soils with differing acidities and organic carbon contents. The determined K oc values for triclosan and diclofenac consistently demonstrated their lower potential mobilities in both soils. The predicted high mobility of chloramphenicol is supported by its efficient leaching potential (89–100 %) in both soils whereas bezafibrate, diclofenac and carbamazepine demonstrate slightly lower affinities for the leachate (61–96 %) for soil A and are strongly retained (>99 %) by soil B. The amount of PPCP in the leachate, the rate of leaching and the depth of soil penetration are explained in terms of the soil characteristics and the properties of the individual PPCPs (such as solubility and pKa) with soil organic content being shown to be a critical factor controlling the ability of a soil to retain a PPCP in the surface layers. The findings contribute to the scientific knowledge required by practitioners and regulators as they consider future subsoil contamination by PPCPs and subsequent possible threats to groundwater resources and surface water habitats.

Microscale vicariance and diversification of Western Balkan caddisflies linked to karstification.

The karst areas in the Dinaric region of the Western Balkan Peninsula are a hotspot of freshwater biodiversity. Many investigators have examined diversification of the subterranean freshwater fauna in these karst systems. However, diversification of surface-water fauna remains largely unexplored. We assessed local and regional diversification of surface-water species in karst systems and asked whether patterns of population differentiation could be explained by dispersal-diversification processes or allopatric diversification following karst-related microscale vicariance. We analyzed mitochondrial cytochrome c oxidase subunit I (mtCOI) sequence data of 4 caddisfly species (genus Drusus) in a phylogeographic framework to assess local and regional population genetic structure and Pliocene/Pleistocene history. We used BEAST software to assess the timing of intraspecific diversification of the target species. We compared climate envelopes of the study species and projected climatically suitable areas during the last glacial maximum (LGM) to assess differences in the species climatic niches and infer potential LGM refugia. The haplotype distribution of the 4 species (324 individuals from 32 populations) was characterized by strong genetic differentiation with few haplotypes shared among populations (16%) and deep divergence among populations of the 3 endemic species, even at local scales. Divergence among local populations of endemics often exceeded divergence among regional and continental clades of the widespread D. discolor. Major divergences among regional populations dated to 2.0 to 0.5 Mya. Species distribution model projections and genetic structure suggest that the endemic species persisted in situ and diversified locally throughout multiple Pleistocene climate cycles. The pattern for D. discolor was different and consistent with multiple invasions into the region. Patterns of population genetic structure and diversification were similar for the 3 regional endemic Drusus species and consistent with microscale vicariance after the onset of intensified karstification in the Dinaric region. Karstification may induce microscale vicariance of running surface-water habitats and probably promotes allopatric fragmentation of stream insects at small spatial scales.

A new cyclopoid copepod from Korean subterranean waters reveals an interesting connection with the Central Asian fauna (Crustacea: Copepoda: Cyclopoida)

Monchenkocyclops gen. nov. was erected to accommodate M. changi sp. nov. from South Korea (type species), M. mirabdullayevi sp. nov. from Kazakhstan, M. biarticulatus (Monchenko, 1972) comb. nov. from Uzbekistan, and M. biwensis (Ishida, 2005) comb. nov. from Japan. The latter species was originally described from surface-water habitats of the ancient Lake Biwa in the genus Diacyclops Kiefer, 1927, while two Central Asian species were previously collected from groundwater habitats and assigned to the genus Acanthocyclops Kiefer, 1927. Monchenkocyclops changi is also found in subterranean waters, and described here in detail. It is morphologically most similar to its Uzbek congener (not to the Japanese one), which rises some interesting zoogeographical questions about the disjunct distribution of this genus. Range fragmentation is a more plausible explanation for this distribution pattern than range expansion, and we emphasize four lines of evidence that support this hypothesis. Four species of Monchenkocyclops share not only the same segmentation of the swimming legs, but also the exact same armature formula of all swimming legs, in addition to many other morphological characters, such as the caudal rami shape and armature, absence of exopod on the antenna, similar shape of the seminal receptacle, fifth leg, etc. They can be distinguished mostly by the relative length of different armature elements, such as the innermost terminal caudal setae, and inner setae and apical spines on the third endopodal segment of the fourth leg. A dichotomous key to species is provided.

Visual spectral sensitivity of photopic juvenile Pacific bluefin tuna (Thunnus orientalis)

Although Pacific bluefin tuna is a species that relies on vision, its photopic visual function is not well known; we therefore recorded electroretinograms to investigate photopic spectral sensitivity in juveniles of this species (49-81days post-hatch; standard length 74-223mm). The peak spectral sensitivity wavelength was 505nm. We estimated that two (λ(max)=512-515nm and 423-436nm) or three (λ(max)=512-515nm, 423-436nm, and 473nm) types of cone visual pigments contribute to photopic vision; these spectral sensitivities are adapted to surface water habitats in clear ocean and coastal water.

Tissue nutrient concentrations in aquatic macrophytes: comparison across biophysical zones, surface water habitats and plant life forms

Aquatic plant tissue (nitrogen) N and phosphorus (P) concentrations, together with the N:P ratio in general, respond poorly to ambient nutrient supply. The variability in plant tissue nutrient concentrations appears to be highly conditioned by taxonomic (mostly species) effects. The significant role that other attributes of the surrounding environment may have in modifying the degree of taxonomic dependence on plant nutrient concentration is yet to be tested with a broader characterisation of plant life forms (bryophytes, helophytes, hydrophytes), so as to investigate implications for ecosystem processes. Plant samples (378) were collected across 65 sites spanning a wide range of aquatic habitats (lotic and lentic) and biophysical zones (floodplain, glacial terraces, mountains) located in NE Scotland. Significant differences in plant tissues N, P and the N:P were found after grouping sampling sites by either habitat or biophysical zones; the latter even after removing the largest taxonomic effect. The range in plant tissue N and P was relatively wide within habitats and zones, reflecting the high species diversity of the studied area. As a group, bryophytes had smaller N and P concentrations, and consequently wider biomass C:N and C:P ratios, a situation which may impose constraints on the flow of energy through food-webs of the mountain and bog areas where they dominate.

Water dissolved nitrous oxide from paddy agroecosystem in China

Although nitrous oxide emission from agricultural leaching and runoff is thought to constitute a globally important source of this greenhouse gas, water dissolved N 2O in paddy ecosystems is poorly understood and scarcely reported where large amounts of fertilizer nitrogen are applied. This paper gives the results of a study assessing variability of the relationships between N 2O and NO 3 − concentration in leachates from packed soil mesocosms, monolith lysimeters, and in wells, rivers and lakes in a region of China where land use is dominated by rice agriculture. Mesocosm and monolith experiments involved different application rates and types of fertilizer. From repetitive observations for each treatment in laboratory and field experiments and the results of the field surveys, we found that the average N 2O/NO 3 − ratios in groundwater varied across space and were much lower than the current IPCC default value. Riparian zones may be hotspots of N 2O production in the Taihu Valley and significant loss of NO 3 − occurs in riparian and surface water habitats. These findings are useful for calculating N 2O emissions from aquatic ecosystems and lowland paddy agroecosystems.