Lotic Habitats Research Articles

Abundance-based dissimilarity measurements reveal higher heterogeneity of fish communities in the lotic habitats of the Yangtze-Caizi transitional floodplain

Abstract Driven by seasonal flood pulses, fish species inhabiting floodplains migrate between lotic and lentic habitat patches to complete their life histories, which can result in the severely species turnover or nestedness. However, these spatiotemporal dynamics of fish metacommunities (beta diversity) were barely quantified. Previous studies either based on species incidence data in calculating beta diversity or solely focus on partial habitat (lotic or lentic) were widely criticized for their misleading results. Here, we addressed the issue by comparing the taxonomic and functional differences in beta diversity and the turnover and nestedness components between wet and dry seasons in the Yangtze-Caizi transitional floodplain. The calculating of beta diversity based on both incidence and abundance data were also compared respectively to test their sensitivity in revealing fish metacommunity dynamics triggered by flood pulses. Regionally in the studied transitional floodplain, we detected significantly taxonomic and functional homogenization of fish assemblages triggered by floods in the high-water period. Then locally within the lotic habitats, our results demonstrated significantly higher overall beta diversity and the turnover components in both the high and low waters. Meanwhile, the significantly higher Local Contributions to Beta Diversity (LCBD) also indicated the higher uniqueness of lotic habitats. These findings highlighted remarkably heterogeneous fish assemblages in lotic habitats, thus deserving higher conservation priority in contrast with lentic habitats. Comparing with classic incidence-based measurements, our results exhibited higher sensitivity of abundance-based approaches in revealing homogeneous or heterogeneous patterns of fish metacommunities influenced by floods. Our results highlighted the importance of employing abundance-based data to measure beta diversity within small spatial extents.

Microalgal diversity as an indicator of the state of the environment of water bodies of Doon valley in Western Himalaya, India

Abstract The management of biodiversity is of utmost importance for environmental sustainability and conservation. Microalgal diversity/assemblage serves as the biological indicators of water bodies’ environment. In the present study, water samples were collected from ten rivers, three lakes and a stream within Doon valley of Western Himalayas, India. This is the first complete and holistic study of microalgal diversity of Doon valley. Different physico-chemical parameters of the water samples like pH, temperature, turbidity, odour and colour were studied. Microalgal diversity was evaluated to serve as bioindicators of the natural riverine and lacustrine habitats. In addition, ArcGIS software tool was applied to create prediction maps for depicting the physico-chemical characteristics of water samples and microalgal diversity. A geostatistical analysis was devised to make these prediction maps. Further, the microalgal diversity was confirmed using PAST tool through diversity indices. The study confirmed the microalgal biodiversity with Shannon (2.59–2.76) and Simpson’s (0.91–0.93) indices. The microalgal diversity has been also confirmed with the parametric data (pH, temperature, turbidity) and non-parametric data (colour, odour) of collected water samples. The study recorded a total of 33 taxa belonging to 27 genera of microalgae. The microalgal species found in the lentic and lotic habitats belonged to the Chlorophyta, Myxophyta, Bacillariophyta, Euglenophyta and Dinophyta divisions. Three microalgal species belonging to Chlorophyta division were newly reported for Doon valley. Multivariate cluster analysis, non-metric multidimensional scaling and canonical correspondence analysis were appropriately employed to correlate the microalgal diversity with sampling sites and environmental variables. Further, microalgal diversity data was collated and used as specific indicators for pollution status of the sampled sites. Algal Genus Pollution Index (bearing algal indicator genus) has been employed to assess the organic pollution status of the water bodies. The results indicated rivers Rispana and Bindal as the most organically polluted while River Nun as the least polluted among all the lentic and lotic water bodies of Doon valley.

Ingoldian fungi in terrestrial damp woody litter of five tree species

Ingoldian fungi are known to occur beyond their preferred lotic habitats. There are many reports on their occurrence in tree canopies (stemflow, through fall and tree holes) and terrestrial leaf litter. This study aimed to assess the assemblage and diversity of Ingoldian fungi in terrestrial damp woody litter of five tree species grown in scrub jungles of the southwest India, following bubble (2 days) and damp chamber (14 days) incubations of segments of bark and cambium samples. Conidia released into water were trapped using Millipore filters, stained and assessed. Total 30 fungal species were recorded, with a higher species richness in bubble chamber as compared to damp chamber incubation method (25 spp. vs. 18 spp.). The bark samples in bubble chamber incubation method yielded more species than cambium samples (19 spp. vs. 16 spp.). The bark samples in bubble chamber incubation also showed the highest number of exclusive species as compared to cambium samples (8 spp. vs. 6 spp.). Simpson and Shannon diversities were higher in bark samples than cambium samples in bubble chamber incubation with low Pielou’s equitability. The frequency of occurrence of the top three species (Anguillospora longissima, Flagellospora curvula and Triscelophorus acuminatus) and top two species (A. longissima and F. curvula) were same in both samples in bubble and damp chamber incubations, respectively. The bark samples of Terminalia paniculata and cambium samples of Ficus benghalensis showed the highest number of average species in bubble chamber incubation. The bark samples of Acacia auriculiformis as well as F. benghalensis possess the highest number of average species in damp chamber incubation, while the cambium samples of Artocarpus heterophyllus showed the highest number of average species. All tree species showed the higher number of average conidia in bark samples as compared to cambium samples in bubble chamber incubation, with a highest frequency in Anacardium occidentale. The bark of Acacia auriculiformis and cambium of F. benghalensis showed the highest average conidia in damp chamber incubation. Bubble chamber incubation served as a rapid and efficient method of assessment of Ingoldian fungi in damp woody litter.

Setting the stage for new ecological indicator species: A holistic case study on the Iberian dolphin freshwater mussel Unio delphinus Spengler, 1793

Abstract Due to their sensitivity and dramatic declines, freshwater mussels are prime targets for conservation and environmental monitoring. For this, however, information is needed on life history and ecological traits, which is lacking in many taxa, including threatened species. Species recently described or recognized as valid are of particular concern, due to the shortage of even basic knowledge. A case in point is the recently recognized and Near Threatened dolphin freshwater mussel Unio delphinus Spengler, 1793, which is endemic to the western Iberian Peninsula and has suffered marked population declines. To overcome information gaps for U. delphinus, we carried out a holistic biological study across the species range, aiming to: i) estimate the area of occupancy (AOO) and extent of occurrence (EOO) based on updated distribution data taken from the literature and recent surveys; ii) estimate growth patterns from biometrical (shell dimensions and growth annuli) measurements taken on specimens from seven populations; iii) estimate sex ratios from gonad tissue biopsies collected on specimens from eight populations; iv) estimate gametogenesis and sex ratio through histological examination of gonad and gill tissues collected monthly for a year, from a single population; and v) determine host species from infestation trials of glochidia with co-occurring fish species. We estimated an EOO of 706 km2 and an AOO of 61 km2, which together with data on declines assigns the species to the Endangered category using IUCN criteria. Unio delphinus was found to grow faster and to be shorter-lived (up to 11 years, maturity at around 2 years old) than other European freshwater mussels. Growth and life span are similar across the range in lotic habitats, but different from that in lentic habitats. The larvae of U. delphinus may attach to most co-occurring fish species, but only native species were effective hosts. Native cyprinids, especially those from the genus Squalius, seem to be the primary hosts. Overall, the information provided contributes to a better conservation status assessment, selection of conservation and rehabilitation areas, guidance for the establishment of propagation programs and better timing for specimens’ manipulation including monitoring and possible translocations. The framework presented here highlights the importance of basic biological studies to define good ecological and physiological status.

Beavers alter stream macroinvertebrate communities in north‐eastern Utah

Abstract Understanding changes in macroinvertebrate communities is important because they play a large role in stream ecosystem functioning, and they are an important food resource for fish. Beaver‐induced changes to stream morphology could alter macroinvertebrate communities, which in turn could affect food webs and ecosystem function. However, studies investigating the effects of North American beaver activities on macroinvertebrates are rare in the inter‐mountain west, an area with high potential for beaver‐assisted restoration. The aim of this study was to quantify differences in the macroinvertebrate community between unaltered segments of streams and within beaver ponds in north‐eastern Utah, U.S.A. We assessed macroinvertebrate species richness, biomass, density, functional feeding group composition, mobility group composition, and macroinvertebrate habitat characteristics to test the hypothesis that macroinvertebrate communities will differ among habitat types (undammed stream segments and beaver ponds) in beaver‐occupied streams. Beaver pond communities significantly differed from lotic reach communities in many ways. Beaver ponds were less diverse with 25% fewer species. Although there was variability among streams, in general, beaver ponds had 75% fewer individuals and 90% lower total macroinvertebrate biomass compared to lotic reaches. Regarding functional feeding groups, beaver ponds contained more engulfers, while lotic reaches contained more scrapers, filterers, and gatherers. For mobility groups, beaver ponds had more sprawlers, while lotic reaches had more clingers. Swimmers were also more prevalent in lotic reaches, although this is probably due to the abundance of Baetis within lotic reaches. More beaver pond taxa were classified as lentic‐dwelling insects, while more lotic reach taxa were categorised as preferring lotic habitats. The creation of ponds by beavers fundamentally altered the macroinvertebrate community in north‐eastern Utah streams. Such changes to stream macroinvertebrate communities suggest that recolonisation of beavers across North America may be altering stream functioning and food webs. Our study highlights the need to further investigate the effects of beaver recolonisation on stream communities.

Spatio-temporal structure of fish communities Mochokidae (Ostariophysi, Siluriformes) in the Malebo Pool, Congo River (Democratic Republic of the Congo)

At the level of Malebo Pool of the River Congo, ecological studies of Mochokidae fish communities are non-existent. This study was carried out monthly from July 2009 to October 2010, and bimonthly from March 2011 to August 2013 through experimental fishing in seven lotic and lentic stations to specify the spatio-temporal structure of these relatively abundant fish. Multivariate analysis (Canonical Redundancy Analysis) of Mochokidae stands and their habitats show segregation of species between lotic and lentic areas. The lotic habitats (Nganda Mabanga and Ile Mimosa) are colonised by species such as Chiloglanis congicus, Euchilichthys guentheri, Synodontis brichardi, Synodontis longirostris and Synodontis ornatipinnis that are located in rocky substrates with high current speed. Lentic habitats (Ngamanzo-Japon-Mipongo-Molondo-Kingabwa complex) are colonised by other species such as Synodontis acanthomias, S. decorus, S. alberti, S. notatus, S. congicus, S. caudalis, S. soloni, S. pleurops, S. nummifer and S. contractus that live in muddy and sandy substrates with submerged vegetation and weak current. The study aims to contribute towards better management and conservation of the aquatic ecosystem, specifically the habitat of the Mochokidae species, in light of the negative impacts of human developments in the Democratic Republic of the Congo.

Brook trout (Salvelinus fontinalis) movement and survival after removal of two dams on the West Branch of the Wolf River, Wisconsin

AbstractDam removals allow fish to access habitats that may provide ecological benefits and risks, but the extent of fish movements through former dam sites has not been thoroughly evaluated for many species. We installed stationary PIT antennas in 2016 and 2017 to evaluate movements and survival of brook trout Salvelinus fontinalis in the West Branch of the Wolf River (WBWR) in central Wisconsin following removal of two dams and channel modifications designed to promote fish movement. These changes provided access to lacustrine habitats that might provide suitable winter habitat or act as ecological sinks. We used multistate models to estimate transition probabilities between river sections, to determine whether brook trout: (a) moved between multiple river sections and (b) entered lacustrine habitats as seasonal refuges, but eventually returned to lotic habitat. We also used a Cormack‐Jolly‐Seber model to evaluate whether apparent survival of brook trout in the WBWR was comparable to other populations. Few fish moved among river sections or used lacustrine habitat (<5% of tagged fish); most brook trout remained in sections where they were initially tagged, potentially due to quality habitat located throughout the river. Like other studies, brook trout in the WBWR appear to experience high mortality based on low number of detections, few physical recaptures and an estimated eight‐month apparent survival rate of 0.27. In scenarios where fish can already access suitable habitat, removal of dams may not result in substantial increases in fish movement and colonisation of newly accessible habitat may not occur immediately.

Response of freshwater mussel recruitment to hydrological changes in a eutrophic floodplain lake

Although eutrophication of freshwaters is a natural process, the human impact often leads to inland waters becoming overloaded with nutrients, impoverishing many valuable and vanishing habitats, such as floodplain lakes. These changes need to be reversed if the occurrence of endangered aquatic species is to be restored. In this paper we analyse the impact of a change in the water regime of a naturally eutrophic floodplain lake, which harbours a large diversity of Unionidae (large freshwater mussels), a globally threatened taxonomic group that provides important ecosystem functions and services. We found that a slight increase in the discharge from this waterbody, following the construction of an additional outflow pipe, positively influenced recruitment in three of the five mussel species inhabiting the lake. We also found that, after the construction of this additional outflow, the niches of juveniles of Anodonta cygnea and Unio spp. changed, revealing differences in their hydrological requirements. Our results suggest that, as in lotic habitats, complex hydraulic parameters are highly significant to unionid mussels in lentic conditions.

Stream Temperature Modeling Using Functional Regression Models

AbstractStream temperature is one of the most important environmental variables in lotic habitats as it has important and direct impacts on the ecosystem. Given the continuous nature of this variable, the aim of this paper was to introduce functional regression for the air‐stream temperature relation, being capable to model an entire seasonal or annual curve of temperatures as one entity, rather than multiple daily or weekly values in classical models. Three types of functional models were explored in the study and compared to two classical models (Generalized Additive Model and Logistic Model) for six rivers from the United States The results show the functional models have the best performance for all the considered rivers. When comparing functional models between them, one variant of the historical functional model performs better than the two other models and is the most parsimonious. Functional regression leads to encouraging results to model the complete annual stream temperature curve as one entity compared to other classical approaches.

Sponge spicules as indicators of paleoenvironmental changes in island deposits – Upper Paraná River, Brazil

Sediments of fluvial islands are important records for paleoenvironmental and paleoclimatic reconstruction, especially those related to the late Pleistocene and Holocene. The Upper Paraná River (UPR) has numerous paleoenvironmental studies using different approaches – e.g.: sedimentary facies analysis, geomorphological evolution, and evolution of sandbars. This is the first study to use freshwater sponge spicules preserved in fluvial sediments to characterize the environments and processes involved in the island formation. Sponge spicules analysis can be used as a complement of sedimentary facies. We studied two islands that, despite their geographical proximity and similarity, had significant differences in their paleoenvironmental evolution. We identified nineteen species of sponges of lotic and lentic habitats. The sediments from Bandeirantes Island have highly fragmented sponge spicules and species of lotic habitats from the late Pleistocene (14,620 cal yr BP). In addition, from 7380 to 1220 cal yr BP, the occurrence of spongiofacies of Tubella variabilis and Radiospongilla amazonensis indicates a lentic environment in the island. These spongiofacies suggests that Bandeirantes Island had an island-lake environment in the mid-Holocene. After 1220 cal yr BP, occurred the lake colmatation by overbank river flow. However, the sediments from Grande Island only contain lotic sponge spicule fragments. Furthermore, the fragmentation of sponge spicules is associated with transport and remobilization during the Late Pleistocene (12,430 cal yr BP). Finally, there was intermittent deposition and phases of removal of the material due to fluvial erosion after 2570 cal yr BP with rare and dispersed occurrences of freshwater sponges associated with sedimentary aggradation by overbank flow.

Morphological differences between an artificial lentic and adjacent lotic environments in a characid species

Dam constructions cause fundamental changes in the natural landscape, creating new ecological and evolutionary challenges for aquatic organisms. In some cases, such water impoundments have been related with morphological changes in organisms. Understanding how populations respond to rapid environmental changes imposed by dams is the first step to elucidate the consequences that disturbed habitats may have on species evolution. In this work, we analyzed shape and size variation in Bryconamericus iheringii Boulenger 1887 from the Chasqueiro stream basin, south of Brazil, which was recently dammed. We used linear measurements and geometric morphometrics to identify morphological differences among specimens from the reservoir (lentic habitat) compared to the habitat upstream and downstream of the dam (lotic habitats). We also tested for size- and shape-related sexual dimorphism to determine whether variations observed were the same for both sexes. We found that B. iheringii from the artificial reservoir were distinct in shape and size to those from their natural habitat in the stream. The size variation between environments was the same for both sexes, but the shape variation differed between males and females. Regarding the linear measurements, lotic populations were larger (greater body length, width, pectoral fin base length and caudal peduncle length), probably in response to increased swimming activity. Regarding body shape, we found that both sexes have a more fusiform body in lotic habitats than in the reservoir. In addition, females showed an altered mouth position that was distinct between these environments. This work indicates that the water reservoir seems to be an important factor influencing morphological variation in B. iheringii, a species with sexual shape dimorphism.

An application of PCR-RFLP species identification assay for environmental DNA detection.

Recent advancement of environmental DNA (eDNA) methods for surveying species in aquatic ecosystems has been used for various organisms and contributed to monitoring and conservation of species and environments. Amphibians are one of the promising taxa which could be monitored efficiently by applying quantitative PCR (qPCR) or next generation sequencing to eDNA. However, the cost of eDNA detection using these approaches can be quite high and requires instruments that are not usually installed in ecology laboratories. For aiding researchers in starting eDNA studies of amphibians, especially those not specialized in molecular biology, we developed a cost efficient protocol using PCR-RFLP method. We attempted to detect eDNA of three Japanese Rana species (Rana japonica, Rana ornativentris, and Rana tagoi tagoi) in various spatial scales including an area close to the Fukushima nuclear power plant where the environment is recovering after the disaster in 2011. Our PCR-RFLP protocol was successful in detecting Rana species in static water in both laboratory and field; however, it could not detect Rana species in non-static water samples from the field. Even a more sensitive detection method (standard qPCR) was unable to detect frogs in all non-static water samples. We speculate that our new protocol is effective for frogs living in lentic habitats, but not for lotic habitats which may still require the gold standard of field observation for detection approach.

Not going with the flow: Locomotor activity does not constrain immunity in a wild fish.

Immunity is a central component of fitness in wild animals, but its determinants are poorly understood. In particular, the importance of locomotory activity as a constraint on immunity is unresolved. Using a piscine model (Gasterosteus aculeatus), we combined a 25‐month observational time series for a wild lotic habitat with an open flume experiment to determine the influence of locomotor activity (countercurrent swimming) on natural variation in immune function. To maximize the detectability of effects in our flume experiment, we set flow velocity and duration (10 cm/s for 48 hr) just below the point at which exhaustion would ensue. Following this treatment, we measured expression in a set of immune‐associated genes and infectious disease resistance through a standard challenge with an ecologically relevant monogenean infection (Gyrodactylus gasterostei). In the wild, there was a strong association of water flow with the expression of immune‐associated genes, but this association became modest and more complex when adjusted for thermal effects. Our flume experiment, although statistically well‐powered and based on a scenario near the limits of swimming performance in stickleback, detected no countercurrent swimming effect on immune‐associated gene expression or infection resistance. The field association between flow rate and immune expression could thus be due to an indirect effect, and we tentatively advance hypotheses to explain this. This study clarifies the drivers of immune investment in wild vertebrates; although locomotor activity, within the normal natural range, may not directly influence immunocompetence, it may still correlate with other variables that do.

Changes to freshwater mussel assemblages after 25 years of impoundment and river habitat fragmentation

Abstract The Tennessee–Tombigbee Waterway is among the largest and most expensive environmental engineering projects of the 20th century. The waterway accommodates barge navigation between the Tennessee River Drainage and Mobile River Basin through a series of locks, dams, canals, and dredged and diverted streams. These structures have altered riverine habitat and fragmented lotic habitats resulting in isolated freshwater mussel populations in patches of streams such as the East Fork Tombigbee River, where 42 species were known historically. The first post‐waterway mussel surveys in 1987 and 1988 reported 31 taxa. During 2010 and 2011 surveys, 70 sites were sampled using both timed searches and quadrats and detected 29 extant mussel species. Between 1988 and 2010–2011 the relative abundance of nine mussel taxa decreased, whereas the abundance of 11 taxa increased. The populations of three federally listed species were detected at levels below the detection limits in 1988 as well as three non‐native unionids that appear to have colonized the East Fork Tombigbee River via the Tennessee–Tombigbee Waterway River. Although mussel abundance and total species richness were relatively unchanged, assemblage composition shifted toward animals typical of smaller streams rather than large rivers. This shift suggests that present‐day East Fork Tombigbee River habitats favour smaller‐bodied, thinner shelled taxa that are laterally compressed and lack shell sculpture. These taxa are likely to be better adapted to hydrologically and hydraulically variable habitats than are thick‐shelled, large bodied, and sculptured mussels. The results suggest that mussel assemblages are dynamic and may exhibit predictable responses to changes in hydrology, physical habitat conditions, and stream connectivity. However, examinations over broad (20+ yr) temporal scales are needed to observe these shifts. The data demonstrate the value of regular monitoring of diverse mussel assemblages and the importance of stream connectivity and flow modifications to this long‐lived group of benthic invertebrates.

Freshwater sponge (Porifera: Spongillidae) distribution across a landscape: Environmental tolerances, habitats, and morphological variation

AbstractFreshwater sponges are important to ecosystem functioning; however, information about their biogeography and interspecific variation is fragmentary, limiting our ability to assess their role. Although the specific epithets of two common species suggest that sponges found in lentic habitats are Spongilla lacustris, and those found in lotic habitats are Ephydatia fluviatilis, the number of sponge species in the UK is unresolved. We sampled sponges in a variety of habitats and used both morphological and molecular (D3 domain of 28S rDNA) methods to identify six species, including the first record of Trochospongilla horrida. We contrasted species in terms of their environmental tolerances, habitats, and variation, and we expanded on the limited information available about the geographic distributions of these sponges. In our study, most sponge species colonized a variety of substrates, but exhibited different distributions. The most widespread sponge, S. lacustris, was present at lower mean water temperatures and was more often located above a latitude of 55°N. Ephydatia fluviatilis was the most common species in rivers, but was also located in lentic habitats. Salinity in anthropogenic habitats was not a significant factor for the presence of E. fluviatilis or the more patchily distributed species Eunapius fragilis. Instead, these species occurred more frequently at sites with negative oxidation–reduction potential. Sponge biodiversity may be affected by substrate availability in anthropogenic habitats, invasive species, and improved ability to recognize sponge taxa. Crucially, we provide foundation data as a prerequisite for future ecological evaluation.

Occurrence and habitat use of European eel (Anguilla anguilla) in running waters: lessons for improved monitoring, habitat restoration and stocking

To improve the management of the European eel (Anguilla anguilla) in freshwater, it is essential to define important lotic habitats. Electrofishing data from 289 wadeable, hard-bottom sites in 69 Swedish coastal rivers and streams, originally surveyed for salmonid monitoring, were used to evaluate the effects of sampling- and habitat-related factors on eel occurrence. Probability of eel occurrence, as influenced by sampling procedure (sampled area, number of consecutive runs and ambient water temperature) and habitat characteristics (size of catchment, dominating bottom substrate, shade, water velocity, mean depth), was evaluated for small (total length ≤ 150 mm) and large (> 150 mm) yellow eels. Data were analysed in a mixed presence/absence generalized linear model with dispersal (distance to mouth from sampled site), habitat and sampling-related variables as covariates. The two models explained variation in occurrence to 81.5% for small eel and 76.2% for large eel. Probability of eel occurrence decreased with distance from the river mouth, and increased with sampled area, number of runs, water temperature, coarser substrate and size of river. We suggest that future eel habitat restoration should focus on lower reaches of larger rivers with suitable coarse bottom habitats. Stocking of young eel should be carried out in comparable accessible habitats in the upper reaches where eel densities are low. The results also strongly indicate that eel may be sampled together with young salmonids with DC electrofishing in wadeable habitats.

The genus Dixa (Diptera, Dixidae) in Croatian lotic habitats, with a checklist of species and relationships with the fauna of neighbouring countries.

Invertebrate surveys in Croatia conducted between 2005 and 2018 included 39 sampling sites yielding bycatch samples of Dixidae (Diptera). All records of this family from the territory of Croatia are summarized, including previously unpublished data. Collections contained six species of Dixa Meigen – D. dilatata Strobl, D. maculata Meigen, D. nebulosa Meigen, D. nubilipennis Curtis, D. puberula Loew, and D. submaculata Edwards, with Dixa dilatata reported from Croatia for the first time. Information relating to the ecoregions in which species were found and specific species traits are provided. Compared to neighbouring countries, the Croatian species assemblage is most similar to the fauna of Italy and least similar to that of Serbia and Montenegro.

The use of palaeoecological and contemporary macroinvertebrate community data to characterize riverine reference conditions

AbstractDefining reference conditions is a crucial element in quantifying the extent of anthropogenic modification and for identifying restoration targets in riverine ecosystems. Despite palaeoecological approaches being widely applied in lakes to establish reference conditions, their use in lotic ecosystems remains limited. In this study, we examine contemporary, historical (1930 and 1972), and palaeoecological macroinvertebrate biodiversity and biomonitoring scores in Eastburn Beck, a headwater tributary of the River Hull (UK) to determine if palaeoecological approaches can be used to characterize lotic system reference conditions. Palaeoecological samples comprised a greater gamma diversity (18 taxa) than contemporary samples (8 taxa), samples taken in 1972 (11 taxa) and 1930 (8 taxa). Palaeoecological samples supported taxonomically different Gastropoda, Trichoptera, and Coleoptera (GTC) communities compared with contemporary and historical samples (1930 and 1972). Results from biomonitoring indices using the GTC community indicated that the palaeochannel had (a) similar invertebrate biological quality, (b) a less energetic flow regime, and (c) increased fine sediment deposits compared with the contemporary channel. The results clearly illustrate that palaeoecological data can provide a suitable method to characterize reference conditions for lotic habitats. However, it is important to recognize that faunal data from palaeochannel deposits provide a short‐term “snapshot” of the conditions within the river immediately prior to its hydrological isolation. River restoration activities should therefore draw on multiple lines of evidence, including palaeoecological information where possible, to characterize a range of reference conditions to reflect the highly dynamic nature of lotic ecosystems.

Trophic status of a non-native crayfish in an oligotrophic lake: bottom-up view of a mixed warmwater and coldwater sport fishery food web

Loffredo JR, Moore BC, Lee RW, Katz SL, Cross BK. 2019. Trophic status of a non-native crayfish in an oligotrophic lake: Bottom-up view of a mixed warmwater and coldwater sport fishery food web. Lake Reserv Manage. 35:396–414.Numerous studies in recent decades have observed variable trophic status for freshwater crayfish among endemic and exotic populations in lentic or lotic habitats. In this study, we used stable isotope analyses (SIA) to explore trophic status of an introduced population of northern crayfish (Faxonius virilis) in Buffalo Lake, Washington. Northern crayfish are an important prey item for introduced warmwater and coldwater fish species in this lentic system and may buffer competitive interactions between largemouth bass (Micropterus salmoides), rainbow trout (Oncorhynchus mykiss), and kokanee (Oncorhynchus nerka). In 2017, the δ13C and δ15N values of liver samples from 208 crayfish informed proportional diet estimates. Crayfish diets were comprised of 8 littoral sources and were examined for cannibalism, temporal, spatial, and ontogenetic trophic shifts. There was no significant spatial or temporal trophic shift detected in this crayfish population. Seasonal δ15N values among all crayfish size classes mirrored seasonal abundance shifts of littoral macroinvertebrates. A multiple-source stable isotope mixing model and relative trophic positions provided evidence for an ontogenetic trophic shift between juvenile and adult crayfish, from a generalist detritivore to a predatory diet dominated by Chironomidae and Ephemeroptera. The trophic status of Buffalo Lake crayfish may affect salmonid management goals if interspecific competition for food between crayfish and sport fish is biologically significant. Our research is an important first step to understanding crayfish trophic status in a lentic food web, and should inform fish stocking regimes and fishery regulations in management efforts to achieve long-term sustainability of this diverse fishery.

Decay and persistence of empty bivalve shells in a temperate riverine system

Bivalve shells can persist over a geological time, acting as important physical resources to the associated fauna. However, few studies have investigated their relevance as persistent long-term ecological attributes to the ecosystem. As such, it is relevant to investigate the shell decays in riverine systems subjected to different environmental conditions. Towards this end, shells of four bivalve species (Anodonta anatina, Corbicula fluminea, Potomida littoralis and Unio delphinus) were made available individually and in clusters of different sizes. The effects of river flow and seasonality were assessed by recording the decay rates of shells in lentic and lotic habitats throughout the year. Our results evidenced that the decays varied among species and depend on shell size, water flow and season. Thin shelled species (A. anatina and U. delphinus) showed the highest mean percentage of decay per month, 3.17% (lotic) and 2.77% (lotic), respectively, and thick shelled species (C. fluminea and P. littoralis) the lowest, 2.02% (lotic) and 1.83% (lotic), respectively. Size was a relevant variable explaining decays, with the smallest shells presenting the highest values, 1.2–2.0 times higher compared to the other size classes. Also, robustness showed to be the most relevant feature explaining the decays in thick shelled species. River flow was also a relevant descriptor of the decays, with higher decays observed in the lotic compared to the lentic habitats. Furthermore, lower decays were observed mainly during summer (lentic site), and autumn (lotic site) associated to the burial effect of leaves. In summary, shells of the native species A. anatina and U. delphinus are expected to persist and contribute less as habitat engineering species, than shells of the native P. littoralis and invasive C. fluminea species. This is especially valid to lotic habitats where the decays were up to 2.13 times higher than in lentic habitats.