Changes In Habitat Conditions Research Articles

Untangling multi‐scale habitat relationships of an endangered frog in streams to inform reintroduction programs

AbstractSuccessful reintroductions of endangered species rely on comprehensive knowledge of habitat requirements across spatial and temporal scales. To inform designs of reintroduction programs, we studied habitat selection of the federally endangered Sierra Nevada yellow‐legged frog (Rana sierrae) in streams in its northern range. We quantified multi‐scale habitat use across diverse streams, habitat types within streams, and seasonal flows. In one intermittent stream, we compared habitat selection between wild and captive‐reared frogs that were released as a population augmentation. We analyzed habitat selection of seasonal habitat unit types (e.g., pool, riffle, cascades) and dimensions, and microhabitat hydrology and cover. R. sierrae appeared able to meet its ecological requirements in a variety of habitats. Study streams ranged from third‐order perennial streams to first‐order intermittent headwater creeks. Perennial streams retained a variety of habitats across flows whereas intermittent streams dried to just a few pools. Frogs used all seasonal habitat types but selected deeper pools most often relative to available habitats in intermittent streams and selected riffles or showed no preference in perennial streams. Frogs avoided fast deep‐water microhabitats, but, otherwise, preferred flowing water or deeper water without flow. Our results suggest that diverse streams can be considered candidates for reintroductions. Within intermittent streams, deeper perennial pools may provide more stable release sites, whereas non‐pool habitats may be safer in perennial streams with fish. Importantly, captive‐reared frogs selected similar habitats as wild frogs, suggesting that captivity does not alter habitat selection behaviors post‐release and that reintroduction designs for this species can be based on wild frog preferences. By improving our understanding of how habitat use varies among different types of streams and differs seasonally in response to changing habitat conditions, our results inform the design of effective reintroduction programs for frogs in streams.

Synthesizing and analyzing long-term monitoring data: A greater sage-grouse case study

Long-term monitoring of natural resources is imperative for increasing the understanding of ecosystem processes, services, and how to manage those ecosystems to maintain or improve function. Challenges with using these data may occur because methods of monitoring changed over time, multiple organizations collect and manage data differently, and monetary resources fluctuate, affecting many aspects of data. Because many species respond to changes in habitat conditions and predator-prey relationships across different spatial scales that span management boundaries, greater efforts for collaborating are essential. We demonstrate the challenges and methods for standardizing greater sage-grouse (Centrocercus urophasianus) long-term monitoring data across the species range in the western United States to inform population modeling needs identified by the Western Association of Fish and Wildlife Agencies. We used automated and repeatable methods of standardizing data via custom open-source software (grsg_lekdb) to improve the scientific integrity of future sage-grouse population assessments within and among states. Data standardization included reconciling uses of different terminology and expunging unusable data, resulting in the removal of 26% of data records due to database insertion errors and modifications to >1 million values to correct formatting and typing errors. Our approaches maximized the inclusion of usable data and identified data that could inform detection probabilities, population trends, and monitoring guidelines. Using sage-grouse databases as an example, we identified the importance of data management and how quality assurance and quality control measures can improve the usefulness of these data for future research needs. Our methods of using informatics and concluding recommendations can support similar endeavors of flora and fauna monitoring programs, whether those efforts are to use existing data or support new monitoring programs.

Forest management can mitigate negative impacts of climate and land-use change on plant biodiversity: Insights from the Republic of Korea

Over the past century, the decline in biodiversity due to climate change and habitat loss has become unprecedentedly serious. Multiple drivers, including climate change, land-use/cover change, and qualitative change in habitat need to be considered in an integrated approach, which has rarely been taken, to create an effective conservation strategy. The purpose of this study is to quantitatively evaluate and map the combined impacts of those multiple drivers on biodiversity in the Republic of Korea (ROK). To this end, biodiversity persistence (BP) was simulated by employing generalized dissimilarity modeling with estimates of habitat conditions. Habitat Condition Index was newly developed based on national survey datasets to represent the changes in habitat quality according to the land cover changes and forest management, especially after the ROK's National Reforestation Programme. The changes in habitat conditions were simulated for a period ranging from the 1960s to the 2010s; additionally, future (2050s) spatial scenarios were constructed. By focusing on the changes in forest habitat quality along with climate and land use, this study quantitatively and spatially analyzed the changes in BP over time and presented the effects of reforestation and forest management. The results revealed that continuous forest management had a positive impact on BP by offsetting the negative effects of past urbanization. Improvements in forest habitat quality also can effectively reduce the negative impacts of climate change. This quantitative analysis of successful forest restoration in Korea proved that economic development and urbanization could be in parallel with biodiversity enhancement. Nevertheless, current forest management practices were found to be insufficient in fully offsetting the decline in future BP caused by climate change. This indicates that there is a need for additional measures along with mitigation of climate change to maintain the current biodiversity level.

Екологічні наслідки негативного впливу несанкціонованого видобутку бурштину на лісові ділянки Житомирщини

Amber mining has already led to an environmental catastrophe on a regional scale. According to official data, more than a thousand hectares of land, mostly located in the Central Polissya region (Zhytomyr region), have suffered very severe damage and need to be restored. The conservation value of such areas is lost, and further use for forestry or agriculture is very risky. To develop norms of anthropogenic loads on landscapes, it is mandatory to study anthropogenic transformation by identifying their current ecological status, establishing the dependence of changes on the intensity of anthropogenic loads individually for each natural region. The source materials for obtaining the results are the materials of field research, taxonomic descriptions of plantations, satellite and aerial photographs, as well as the establishment of temporary test areas according to the generally accepted methodology in forestry. The problem that arose in the Zhytomyr region as a result of unauthorized amber mining contributes to the rapid growth of anthropogenic pressure on forestry landscapes, causes them irreparable damage, leads to environmental and economic crisis, imbalances in the social situation of the population, environmental problems, there are significant changes in the structure and mineral composition of the soil layer of forest lands, completely or partially destroyed the living above-ground cover and undergrowth, undergrowth undergoes significant changes in habitat conditions and anthropogenic pressure. Violation of the ecological balance of the forest at different stages of biological development can lead to irreversible consequences in the forestry sector. The obtained results are promising for further development of own methods of ecological and economic assessment of the damage caused by the consequences of illegal amber mining.

Morphology and Physicochemical Properties of Alluvial Soils in Riparian Forests after River Regulation

The elimination of flooding and lowering of the groundwater table after large-scale river regulation allow deep penetration of soils by plant roots, soil fauna, and microorganisms, thus creating favorable conditions for advanced pedogenesis. Although the changes of the morphology and properties of agriculturally used drained alluvial soils in Central Europe have been well characterized, studies in riparian forests remain insufficient. An analysis of 21 profiles of forest soils located on the Holocene river terrace (a floodplain before river regulation and embankment) in SW Poland confirmed a noticeable pedogenic transformation of soil morphology and properties resulting from river regulation. Gleyic properties were in most profiles replaced with stagnic properties, testifying to a transition from dominant groundwater supply to precipitation-water supply. The development of a diagnostic mollic and cambic horizons, correlated with the shift in soil classification from Fluvisols to Phaeozems, and in the majority, to Cambisols, demonstrated a substantial change in habitat conditions. The transformation of alluvial soils may result in an inevitable modification of forest management in the river valley, including quantitative alteration in species composition of primarily riparian forests.

Linking variability in early life growth of Sardinella lemuru to changes in habitat conditions in Zamboanga upwelling system, Sulu Sea, the Philippines

The year-class success of small pelagic fish is strongly modulated by the growth and survival of early life stages. Determining how environments control growth is critical to understanding processes influencing annual production. We provide the first measurements of larval growth in Sardinella lemuru, the most abundant and exploited tropical sardine species in the Philippines. Growth rates of larvae were examined across a 2 yr period (2011-2012 and 2012-2013 spawning seasons) using otolith microstructure analysis. Transition to the juvenile stage occurred within 25 to 37 d. Mean growth rate of the 2011 year-class was significantly lower than the 2012 year-class despite significant intra-annual (batch) differences in growth trajectories. In both years, larvae that hatched and developed in the cooler yet prey-rich period in the middle of the spawning season (January) displayed the fastest growth, while those spawned early (September-October 2012) and late (February-March 2012) showed the slowest growth rates. Peak hatch-months (December 2011 and October 2012) were just prior to periods of upwelling, with mean prey concentrations of 0.24 ± 0.13 mg m-3 at 26.35 ± 2.56°C sea surface temperature (SST) and 0.23 ± 0.15 mg m-3 at 26.26 ± 1.79°C, respectively. The SST during upwelling was 0.01 to 1.23°C cooler accompanied by a 0.07 to 0.45 mg m-3 increase in prey concentration. In both years, differences in growth rate were strongly linked to oceanographic conditions. Moderate winds during a ‘neutral’ El Niño-Southern Oscillation year resulted in upwelling conditions favoring faster overall growth in larvae which was associated with stronger recruitment. In contrast, slower growth and weaker recruitment were associated with weak upwelling conditions in the 2011-2012 La Niña year. While temperature may be important, larval growth rates appear to be driven more by prey abundance.

Application of biomonitoring technology in environmental engineering based on model groups of amphibiontic organisms (insecta: odonata)

The paper presents the results of the analysis of the use of amphibiontic organisms as bioindicators of the ecological environment, as model groups in ecological engineering. The solution to the conceptual problem of ecological engineering in the conservation of biological diversity is to take an inventory of natural, urbanized and agroecosystems. Among amphibiotic insects, the order Odonata stands out, with morphological plasticity, biological progress, adults and dragonfly larvae actively colonize aquatic and terrestrial ecosystems of various types. When moving to habitat in mountain biotopes, the linear body dimensions of dragonfly larvae of the species L. depressa L., S. meridionale Selys, C. puella L. decrease, which indicates unfavorable, contrastingly changing habitat conditions in mountain ecosystems. The taxonomic composition of dragonflies in lowland water bodies is represented by the suborders Anizoptera (7 species), Zygoptera (5 species), Caloptera (1 species). In the foothill water bodies - Anizoptera (5 species), Zygoptera (4 species), Caloptera (1 species), in mountain water - Anizoptera (4 species), Zygoptera (2 species). Most of the dragonfly taxa are characteristic of the plains and foothills with eutrophied biotopes characteristic of polysaprobic reservoirs with heavy pollution. In oligosaprobic biotopes, with little or no organic pollution in the water, dragonflies Ae. cyanea Müller and C. splendens Harris. The confinement of species to certain habitats, characterized in varying degrees of pollution by organic substances and their oxidation products, makes it possible to use dragonflies as bioindicators and organize background monitoring of ecosystems in the Central Caucasus.

Application of Bayesian networks in evaluation of current status and protection of Pulsatilla patens (L.) Mill.

AbstractUnderstanding of the impact of environmental factors on endangered plant species provides a basis for assessment of the risk of their extinction in the near future. Of particular importance is the search for optimal environmental conditions to preserve the continued existence of endangered taxa. Thus, there is a need for a method based on mathematical modeling to connect the current status of an endangered plant species with changing environmental conditions. Using the basics of decision theory, we developed a mathematical model to assess the influence of changing habitat conditions on the current status and protection of Pulsatilla patens (L.) Mill., an endangered plant species in Europe, as an example. The mathematical model was based on the data from 43 sites in the 3 largest forest complexes in NE Poland from 2011 to 2014 (29 attributes, 1566 records). The graphical model showing significant cause‐and‐effect relations between morphological‐developmental features of individuals, demographic features of the populations, and physicochemical properties of the soil was built using the Bayesian networks in GeNIe 2.0 (University of Pittsburgh, Pittsburgh, Pennsylvania, USA). In the process of modeling with the Bayesian Search Algorithm, we also performed simulation, prediction, and optimization of the effects of selected environmental factors on growth and development of the endangered taxon. The diagnostic testing and sensitivity analysis revealed that the degree of soil acidification is the major variable determining the size of populations (number of individuals), developmental phase (juvenile, vegetative, flowering), and size of the individuals (height and diameter of ground rosette). Using the approach presented in this work, it was possible to identify a new habitat factor not known to be important at multiple scales for growth, development, and population dynamics of P. patens. The validation showed that the developed model is the most effective for evaluation of the impact of habitat conditions on the population features important for reproduction of this taxon. Therefore, the model proposed is recommended as a tool to support decision‐making aimed at conservation planning of the endangered plant species.

Impact of natural factors on population changes of herbaceous plants species and assessment of their state in present high-mountain conditions of the Ukrainian Carpathians

Impact of natural factors on population changes of herbaceous plants species and assessment of their state in present high-mountain conditions of the Ukrainian Carpathians

Fast responses of microbial plankton communities associated to regime shifts in vegetated wetlands (free-floating plants vs phytoplankton-dominance): An experimental cross-transplant approach

Vegetated wetlands are naturally subjected to changes in their water-level and macrophyte coverage leading to high habitat heterogeneity. The opportunistic ecological strategy of many planktic algae and bacteria makes them suitable for studying adaptive mechanisms to environmental change in wetlands at different temporal and spatial scales. In this study, we assessed the response of microbial aquatic organisms to sudden changes in habitat conditions, resulting from regime shifts involving the presence/absence of a dense floating-macrophyte cover, by means of a 72 h cross-transplant experiment using dialysis bags. Contrasting conditions imposed by the existing regime, such as light availability and dissolved oxygen concentration, accounted for the differences in phytoplankton and picoplankton compositions. Communities newly exposed to improved light and oxygen conditions exhibited a short-term (hours) response of C-strategists algae, such as small flagellated chrysophyceans. The onset of oxygen depletion and light impoverishment favoured the development of anaerobic anoxygenic photosynthetic bacteria (AnAnPB) and low-light adapted S-strategists (thin filamentous oscillatoriales) algae in few days. These results provide in-field evidence that phytoplankton and picoplankton assemblages are highly sensitive to environmental changes in a brief time scale, less than 72 h. Thus, these microbial organisms can act as sentinels to fluctuations in vegetated wetlands, also giving a quick response to sudden changes deriving from anthropogenic practices that impact on wetlands water-level and provoke fluctuations in their floating vegetation cover.

The Plant Flow Index: A new method to assess the hydroecological condition of temporary rivers and streams

Temporary streams are widespread in global river networks, and hydroecological tools are needed to assess biotic responses to changes in environmental conditions between wet and dry states.Plant communities can be abundant and diverse in temporary streams, and vary in their tolerance of changing water availability and associated habitat conditions, but globally, no indices have been developed to document community-level responses to intermittence. We present the first index developed to assess plant assemblage responses to changing habitat conditions in temporary stream channels: the Plant Flow Index (PFI). Using a regional 22-year dataset from lowland groundwater-fed headwater streams in the UK, we establish relationships between the occurrence and abundance of 34 common aquatic, semi-aquatic and terrestrial taxa and the proportion of time the channel was dry within the antecedent 12 months. Species/taxon-specific responses to channel drying were weighted and used to calculate a single score representing each community. We compare the PFI to three other plant assessment methods, which demonstrates its greater ability to reflect the effects of intermittent flow and specifically drying events. The PFI represents a flexible index that can be modified to include additional and/or different taxa and their responses to intermittence, allowing its application across regions and river types with contrasting environmental characteristics and intermittence regimes. As temporary streams increase in both space and time, this index represents a valuable tool to track ecological responses to intermittence at both broad and fine spatial and temporal scales.

Responses of humpback whales to a changing climate in the Southern Hemisphere: Priorities for research efforts

AbstractGlobally, baleen whales were severely depleted by historic whaling. Recovering populations have been observed to alter their behaviour. These changes have been attributed to climate change in some cases and raise concerns over the successful recovery of baleen whale populations. Current data‐driven statistical habitat and behavioural models have proven useful for addressing questions of whale distribution changes within their limitations. Given observed changes in oceanic conditions, a new approach to managing baleen whale population recovery is necessary. Model predictions of future whale movements and distributions under climate change scenarios are vital to enable adequate conservation management. This paper presents a new perspective on understanding the impacts of climate change on humpback whales, arguing the need for a system‐based multidisciplinary research approach. Our approach includes coupled, mechanistic models based upon robust ecological principles, and integrates key physical, biogeochemical, biological and ecological modules to address long‐term changes associated with climate change. To illustrate the need for this system‐based multidisciplinary approach, we focus on Southern Hemisphere humpback whales, the recovery of which may be impacted by rapid changes in habitat conditions brought about by anthropogenic climate change.

The impact of climate change on flow conditions and wetland ecosystems in the Lower Biebrza River (Poland).

Water plays a key role in the functioning of wetlands and a shortage or contamination of it leads to changes in habitat conditions and degradation of ecosystems. This article scrutinizes the impact of climate change on the hydrological characteristics of floods (maximum flow, duration, volume) in the River Biebrza wetlands (North-East Poland). We analysed the trends in duration and volume of flood and maximum discharges in the historical period 1970–2000 and predicted these for the future periods 2020–2050 and 2070–2100, respectively. Next we assessed the impact on the wetland ecosystems. The basis of our assessments consists of statistical analyses of hydrographs and calculations by the Soil and Water Assessment Tool hydrological model and considering nine bias-corrected climate models. The results indicate that both volume and duration of winter floods will keep increasing continuously under Representative Concentration Pathways 4.5 and 8.5. The reduction in peak annual floods is expected to decline slightly in both scenarios. On the other hand, the analysis of trends in mean and standard deviation revealed negligible tendencies in the datasets for summer and winter hydrological seasons within the three time frames analysed (1970–2000; 2020–2050; 2070–2100). We foresee several future implications for the floodplain ecosystems. Shifts in transversal ecosystem zonation parallel to the river will likely take place with more highly productive flood tolerant vegetation types. Nutrient availability and algal blooms during spring inundations will likely increase. Slowdown of organic matter turnover later in summer will lead to a higher peat accumulation rate. Logistical problems with summer mowing and removal of bushes in winter may enhance shrub encroachment.

Impact of informal timber harvesting on habitat structure and bird assemblages in a coastal forest of the Eastern Cape, South Africa

SummaryAfrican forests are under increasing pressure to supply local, regional, and international demand for timber. Much of this trade is unregulated, such that there is increasing concern regarding the ecological sustainability of this resource use. However, there is a lack of studies investigating the ecological impact of informal timber harvesting in African forests. While forest species have adapted to natural canopy gap dynamics, harvesting may alter natural disturbance regimes, with adverse effects on biodiversity. Information regarding harvest gaps, and concomitant impacts on habitat and biodiversity is thus essential to inform sustainable management. This study compared the frequency and nature of harvest gaps and natural gaps in a coastal forest in the Eastern Cape, South Africa, where informal selective timber harvesting occurs. Habitat condition and bird species richness and composition were compared across intact forest, natural gaps, and harvest gaps. Harvest-created gaps increased the number of canopy gaps by 30%, but were comparable with natural gaps in size. Habitat conditions in harvest gaps represented an intermediate state between intact forest and natural gaps, thereby increasing forest-scale habitat heterogeneity. While bird species richness was not affected, species composition differed across intact forest, harvest gaps and natural gaps, driven by changes in habitat condition, and mediated by species’ feeding and nesting traits. Specifically, insectivores, cavity- and ground-nesting species, and hawking and arboreal probing species were negatively affected by the habitat gradient from intact sites to canopy gap conditions, while nectarivores, omnivores and ball/cup nesting species were positively affected. Thus, while the single-tree selective harvesting method used by informal harvesters largely emulated natural canopy disturbances, the harvest-mediated increase in the frequency of canopy gaps may reduce the abundance of certain bird species sensitive to canopy gap conditions and reduce forest-scale beta-diversity.

Characteristics of Liparis loeselii (L.) Rich. populations in selected Natura 2000 areas in eastern Poland

In view of the sensitivity of Liparis loeselii to changes in habitat conditions, we carried out a study with the aim to monitor population numbers, identify the individual features of the Liparis loeselii population, analyse habitat conditions, identify threats and propose conservation measures to preserve the species. The investigations were conducted in seven unmanaged objects located in three Natura 2000 areas in eastern Poland. The results of this study provide a new insight into Liparis loeselii ecology. The analysed populations inhabited some habitat types: extremely poor fen, transitional mire, rich fen, calcareous fen, spring-fed fen. The content of nutrients was similar in all the habitats. A CCA analysis revealed that the total carbon content, pH, and redox potential of the substrate determine differences between the habitats analysed. Juvenile individuals represented a maximum of 12% of the analysed populations and were the least abundant group of these plants. The flowering was primarily influenced by hydrological conditions. Based on the long-term observations reported in this article, it can be assumed that the species stands a chance of surviving at the localities analysed, provided that the habitat conditions do not change dramatically.

Parasitological Survey of Cichlidae in the Sea-of-Galilee

The results of a parasitological survey conducted since January 2012 till January 2014 in the littoral zone of the Sea-of-Galilee are presented. The parasites were identified, and their prevalence, density, and geographic distribution were studied. Wet-preparations were used for detection and identification of the parasites. In the described time period, a total of 200 adults and 200 fingerlings of the following fish species Sarotherodon galiaeus (68%), Tilapia zillii (20%) and Oreochromis aureus (12%). The fish were collected from four dispersed coasts of the lake. The primary results of the survey indicate that 30% of examined fish were infected with ciliates. The prevalence of myxozoa was 18% in adults, mostly in the spleen, and was lower in fingerlings, exhibiting prevalence of only 8%. High prevalence of trematode metacercaria was found in fingerlings, (85%), significantly higher than in adults (36%). The most common trematode metacercaria found were Neascus sp. and Bolbophorus sp. These parasites were found mostly in the brain and eyes. Surprisingly, the following trematodes: Clinostomum, Euclinostomum, Neascus and Bolbophorus, which were missing in the previous study conducted on 1999- 2002, were commonly found in the current study. In light of the findings of the present study as compared to previous ones, it seems that there is a change in metacercaria species throughout the years. It is likely that the changes in the composition of the parasites population found in this survey are related to changes in habitat conditions that affected the survival of the intermediate host communities.

Development of a modified floristic quality index as a rapid habitat assessment method in the northern Everglades.

Floristic quality assessments (FQA) using floristic quality indices (FQIs) are useful tools for assessing and comparing vegetation communities and related habitat condition. However, intensive vegetation surveys requiring significant time and technical expertise are necessary, which limits the use of FQIs in environmental monitoring programs. This study modified standard FQI methods to develop a rapid assessment method for characterizing and modeling change in wetland habitat condition in the northern Everglades. Method modifications include limiting vegetation surveys to a subset of taxa selected as indicators of impact and eliminating richness and/or abundance factors from the equation. These modifications reduce the amount of time required to complete surveys and minimizes misidentification of species, which can skew results. The habitat characterization and assessment tool (HCAT) developed here is a FQA that uses a modified FQI to detect and model changes in habitat condition based on vegetation communities, characterize levels of impact as high, moderate, or low, provide predictive capabilities for assessing natural resource management or water management operation alternatives, and uniquely links a FQI with readily accessible environmental data. For application in the northern Everglades, surface water phosphorus concentrations, specific conductivity, distance from canal, and days since dry (5-year average) explained 67% of the variability in the dataset with > 99.9% confidence. The HCAT approach can be used to monitor, assess, and evaluate habitats with the objective of informing management decisions (e.g., as a screening tool) to maximize conservation and restoration of protected areas and is transferable to other wetlands with additional modification.

Effects of Temperature on the Survival and Larval Development of Deiratonotus Japonicus (Brachyura, Camptandriidae) as a Biological Indicator

Deiratonotus japonicus (D. japonicus) inhabits isolated locations and upstream brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. This species faces the threat of extinction because of changing habitat conditions. Our previous studies have shown that its complete larval development from hatching to metamorphosis consists of five zoeal stages and one megalopal stage. In this study, the effect of temperature on the survival and growth of larval development in D. japonicus under controlled laboratory conditions of 13, 18, 23, 24, 25, and 26 °C was investigated by rearing larvae (30 PSU; 12:12 h light/dark cycle; fed a diet of Brachionus plicatilis rotundiformis and Artemia sp. nauplii). The survival rates and developmental periods were measured for each larval stage. The highest survival rates were obtained at 18–24 °C. Metamorphosis to megalopa occurred at 23–25 °C. There were rapid and synchronous developments at 25–26 °C but delayed and extended developments at 13 °C. The molting period decreased with increasing temperature. With decreasing temperature, the beginning of the development and duration of molting was prolonged. In addition, there were very low survival rates at 13 °C and 26 °C in all zoeal stages. Our results indicate that the early larval stages of D. japonicus are well adapted to 18–24 °C, the range observed in the estuarine marine environment of the Kita River during the breeding season. Optimum larval survival and growth were obtained at 23 °C. Temperature significantly affected the survival rate, developmental period, and molting of the larvae. The relationship between the cumulative periods of development from hatching through individual larval stages (y) and temperatures (T) was described as a power function (y = a × Tb).

Diel patterns in spatial distribution of fish assemblages in lentic and lotic habitat in a regulated river

AbstractFish assemblages in large rivers are governed by spatio‐temporal changes in habitat conditions, which must be accounted for when designing effective monitoring programmes. Using boat electrofishing surveys, this study contrasts species richness, catch per unit effort (CPUE), total biomass, and spatial distribution of fish species in the Saint John River, New Brunswick, Canada, sampled during different diel periods (day and night) and macrohabitats (hydropower regulated river and its reservoir) in the vicinity of the Mactaquac (hydropower) Generating Station. Taxa richness, total CPUE, and total biomass were significantly higher during night surveys, resulting in marked differences in community composition between the two diel periods. Furthermore, the magnitude of diel differences in catch rate was more pronounced in lentic than in lotic macrohabitats. The required sampling effort (i.e., number of sites) to increase accuracy and precision of CPUE estimates varied widely between fish species, diel periods, and macrohabitats and ranged from 15 to 185 electrofishing sites. Determining a correction factor to contrast accuracy and precision of day‐ with night‐time surveys provide useful insights to improve the design of long‐term monitoring programmes for fish communities in large rivers. The study also shows the importance of multihabitat surveys to detect differences in the magnitude of diel changes in fish community metrics.

Succession Characteristics and Water Quality Responsiveness Evaluation of FG and MBFG in Yanlong Lake Water Source Ecological Purification System

To explore the water purification efficiency and phytoplankton control efficiency of the water source ecological purification system, and evaluate the effectiveness of the functional group (FG) and morphology-based functional group (MBFG) in response to the internal environment and water quality of the water source ecological purification system, in the summer of 2018, the water quality and phytoplankton functional groups of each unit of the Yanlong Lake ecological purification system were monitored and analyzed. The results showed that the Yanlong Lake water source ecological purification system can effectively purify the water. The average values of total phosphorus, total nitrogen, dissolved oxygen, and turbidity in the influent water were 0.20 mg·L-1, 1.91 mg·L-1, 2.88 mg·L-1, and 60.23 NTU, respectively; after system treatment, these were 0.09 mg·L-1, 0.95 mg·L-1, 6.26 mg·L-1, and 39.53 NTU, respectively. Simultaneously, the spatial distribution of water quality within the system was heterogeneous, with significant spatial differences in dissolved oxygen (DO), pH, and turbidity (P<0.001). The Yanlong Lake water source ecological purification system could effectively control the density of phytoplankton (4.42×105-4.32×106 cells·L-1) when the effluent was in a mild eutrophication state. This reduced the risk of algal blooms. There were five absolute advantage FG:B, P, TC, J, and W1. There were six absolute advantage MBFG:GroupⅠ, GroupⅢ, GroupⅣ, GroupⅤ, GroupⅥ, and GroupⅦ. Both absolute dominant functional groups were effective in indicating changes in habitat conditions. The results of RDA analysis found that the environmental interpretation of the MBFG was higher than that of the FG. The results suggested that it is more appropriate to study the dynamics of phytoplankton in the Yanlong Lake ecological purification system in summer by selecting the MBFG classification method.