Habitat Structure Research Articles

Linking habitat and population viability analysis models to account for vegetation dynamics, habitat fragmentation, and social behavior of a metapopulation of Florida scrub-jays

Population dynamics and viability are driven by interactions among habitat and species biology. The Florida scrub-jay (Aphelocoma coerulescens) is a declining and Federally Threatened bird species that requires mid-succession habitat of partly open soil surface with mid-height vegetation. This habitat is created and sustained in a dynamic state of vegetation growth and periodic natural (e.g., fire) or managed (e.g., mechanical clearing) disturbances. Florida scrub-jays once occupied open oak scrub habitats across much of peninsular Florida but have been reduced to a few regional metapopulations and scattered isolated remnant populations. Many of these populations are undergoing continuing decline as open scrub is either converted to residential development or transitions into closed pine and oak forests due to fire suppression. Long-term field studies have shown that breeding and survival rates are determined by the quality of the scrub habitat, with the demography influenced by and in turn mediating the social structure. Prior Population Viability Analyses (PVA) that included dependencies of demographic rates on habitat and social structure indicated that the east coast Florida metapopulations were fragmented into remnant protected patches that were too small and isolated to support long-term persistence, even if the remaining habitat area and quality was sustained. Moreover, recent modeling of habitat transitions under various proposed management schemes, in conjunction with implementation of Adaptive Resource Management (ARM), projected that the proportion of optimal habitat will continue to decline. In this study, we integrated these habitat projections within the PVA and found that the Brevard County mainland metapopulation is projected to decline toward extinction unless habitat quality, extent, and connectivity can be improved. Land managers have recently implemented new innovative methods for restoring optimal scrub habitat, identifying potential improvements in habitat connectivity of nearby populations, and translocation methods to increase and reinforce the demographic and genetic integrity of local populations. Our linked habitat-population models project that the combination of such habitat and population management actions can stabilize the metapopulation and achieve long-term viability.

Variation in biodiversity and abundance of functional groups of arthropods along a tropical elevational gradient in Puerto Rico

AbstractElevational gradients represent platforms for exploring the effects of environmental variation on biodiversity. The environmental correlates of these spatial gradients are likely to be modified during the Anthropocene, as species respond to global change drivers including warming and increased frequency of extreme events. We quantified variation in the abundance of four functional groups of canopy arthropods (i.e., folivores, sap‐suckers, detritivores, and predators), as well as in aspects of biodiversity on each of six host‐plant species along two elevational transects in the Luquillo Mountains of Puerto Rico: a mixed forest transect, traversing tabonuco, palo colorado, and elfin forests, and a palm forest transect, comprising only patches dominated by sierra palm (Prestoea acuminata). We expected gradients in arthropod abundance and biodiversity to be host‐tree specific, and for gradients on palm to differ between transects due to a combination of mechanisms associated with host selection, rescue effects, habitat structure, and source pool dynamics. In general, abundance and biodiversity declined with elevation. The ways in which abundance declined with increasing elevation was contingent on host tree identity and on arthropod functional group, whereas all aspects of biodiversity declined with elevation in consistent manners regardless of host tree identity or transect. Similarly, turnover (beta components of biodiversity between sequential elevational strata) did not differ between transects. Decreases in productivity with increasing elevation may be responsible for gradients in abundance or biodiversity. However, host‐specific and functional group‐specific gradients suggest that elevational effects manifest differently depending on tree species identity and resource bases that are consumer specific.

Seafloor sediment microtopography as a surrogate for biodiversity and ecosystem functioning.

Marine soft sediments play crucial roles in global biogeochemical cycles and biodiversity. Yet, with organisms often hidden in the sediment, they pose challenges for effective monitoring and management. This study introduces a novel approach utilizing sediment microtopography as a proxy for ecosystem functioning and biodiversity. Combining field sampling, benthic chamber incubations, and advanced Structure-from-Motion photogrammetry techniques, we investigated the relationships between microtopographic features and various ecological parameters across diverse subtidal habitats. Our findings reveal strong associations between sediment microtopography and environmental variables, benthic fluxes, biodiversity metrics, and community functional traits, with microtopography consistently explaining more than 50% of the variance in the data. This research demonstrates the potential of sediment microtopography as a cost-effective and scalable tool for assessing soft-sediment ecosystem dynamics and informing conservation strategies. By providing insights into the links between habitat structure and ecological processes, this study advances our understanding of marine benthic ecology and opens new possibilities for habitat assessment applications worldwide.

Habitat management interventions for a specialist mid- successional grassland butterfly, the Lulworth Skipper

Evidence-based management is needed to reverse declines in insect abundance. The Lulworth Skipper Thymelicus acteon is a range-restricted and declining species in the UK and northern Europe associated with mid-successional grassland, which presents management challenges because interventions are necessary to prevent long-term habitat deterioration but can result in short-term reductions in quality. In addition, site management should be compatible for the focal species and for wider plant and insect diversity. We conducted factorial experimental management trials to understand effects of cutting and rotovation on the height and structure of vegetation containing the larval host plant Tor-grass Brachypodium rupestre. We monitored vegetation height, B. rupestre cover and plant diversity, and T. acteon larval presence over four years. Rotovation and cutting differed in their effects on habitat structure and larval occupancy relative to controls. Vegetation height and host plant cover, the most important components of habitat quality for T. acteon, were faster to recover to suitable levels on cut plots. However, larval occupancy increased more quickly on rotovated plots, where plant species diversity was also higher. Results suggest that due to initial negative impacts of interventions on T. acteon occupancy, low frequency or low-intensity management, such as managing sections of a site every three years, is advisable. Our results show that rotovation or cutting the sward can be suitable for mid-successional grassland species such as Lulworth Skipper on sites where grazing might be problematic. Rotational grazing or rotovation can maintain suitable conditions for habitat specialist insects requiring a range of different grassland conditions, serving wider conservation goals.

Spatio-temporal patterns of fish acoustic communities in Western Mediterranean coralligenous reefs: optimizing monitoring through recording duration

In this study, we explored the fish acoustic community at two coralligenous sites in Sardinia (Tavolara and Santa Teresa, western Mediterranean Sea) during the summer 2023. Our goal was to understand spatial and temporal patterns of fish acoustic activity on different temporal scales to offer insights for optimizing acoustic monitoring of this crucial ecosystem. We identified seventeen distinct sound types, revealing a diverse acoustic community. Tavolara had higher acoustic richness and abundance compared to Santa Teresa, which may be attributed to site-specific factors such as habitat structure, species composition, or levels of protection. Temporal analysis revealed clear diel patterns, with certain sounds associated with nocturnal or diurnal periods, reflecting the daily rhythms of different species. The study also examined how recording duration influenced acoustic richness, finding that longer recordings (15 minutes per hour and 15 minutes per hour at night) provided a more comprehensive detection of acoustic activity. Additionally, the number of recording days required to detect species richness varied depending on the site. While extended recordings improve the likelihood of detecting rare or sporadic sounds, they also present challenges in data management and equipment maintenance. The study underscores the importance of carefully planning sampling strategies to optimize acoustic monitoring and ensure effective and sustainable ecological research in coralligenous ecosystems.

Grassland bird responses to bison and prescribed fire in restored tallgrass prairies

AbstractGrazing from megaherbivores such as bison (Bison bison) and periodic fire are 2 important disturbance regimes in grassland ecosystems. In restored tallgrass prairies where these processes were previously removed, prescribed fire application and bison reintroduction are tools used by managers to recreate habitat heterogeneity formed by these disturbances. Tallgrass prairie bird communities may be indirectly affected by these disturbances, as bison and prescribed fire alter the structure of critical breeding habitat for grassland birds. The objectives of this research were to determine the effects of bison and prescribed fire on grassland breeding birds in 2 tallgrass prairie preserves in the Midwest region of the United States. We surveyed bird communities, vegetation structure, and bison activity at an Illinois preserve (n = 20 sites) and an Indiana preserve (n = 27 sites) in 2020 and 2021 and compiled a history of restoration activities (e.g., prescribed fire, planting year) at these sites. Grazing and fire disturbances affected grassland bird diversity and abundances, whereas we found little to no evidence that restoration planting age and spatiotemporal factors affected grassland bird populations. Disturbance effects often corresponded to species‐specific responses to changes in vegetation structure. Grassland‐obligate bird diversity was lower in recently burned and ungrazed management units, in comparison to unburned‐ungrazed and unburned‐grazed sites. Henslow's sparrow (Centronyx henslowii), a species known to be sensitive to recent prescribed fire, exhibited increased abundance with time since fire, an increase that was further amplified with bison presence. These results highlight the importance of applying varying levels of grazing and fire disturbance to provide variable vegetation structure to accommodate the habitat preferences of a diversity of grassland bird species. Moreover, our results indicate that bison may play a role in mediating the differing effects of variable prescribed fire frequencies on grassland bird species of concern.

Greater risk-taking by non-native than native shrimp: an advantage in a human-disturbed environment?

BackgroundThe invasion of non-native species into ecosystems is a growing human-induced problem. To control their spread and population growth, knowledge is needed on the factors that facilitate or impede their invasions. In animals, traits often associated with invasion success are high activity, boldness, and aggression. However, these traits also make individuals susceptible to predation, which could curb population growth. We investigated if a recent invader into the Baltic Sea, the shrimp Palaemon elegans, differs in risk-taking from a native shrimp, P. adspersus. We recorded activity, habitat choice, and response to perceived predation threat of both species.ResultsWe found the invading shrimp to take greater risks than the native one; while the native shrimp adjusted its behaviour to habitat structure and exposure to a perceived predator, the non-native shrimp did not, and it resumed normal activity sooner after a perceived predation threat. Despite the greater risk taking by the non-native shrimp, its population has grown rapidly during the last two decades in the investigated area and is now larger than that of the native shrimp.ConclusionsWe discuss plausible explanations for the population growth of the invader, including the recent decline in predatory fishes that could have reduced the cost of risk-taking, and anthropogenic eutrophication that has increased food abundance could have allowed the population growth. These results stress the need to assess the optimality of the behaviours of both native and non-native species when investigating the factors that influence invasion success in human-disturbed environments.

Under cover: the nuanced influence of functional properties of cover on resource selection by pygmy rabbits (Brachylagus idahoensis)

Abstract Animals at risk of predation select habitat that enhances security from predators. Two properties of cover related to security are concealment (i.e., habitat structure that blocks an individual from detection by others) and visibility (i.e., visual information accessible relative to habitat structure). Although these properties are often negatively correlated, they are not always inverse; animals in habitat with heterogeneous structure may be able to select for both. We investigated habitat use by pygmy rabbits (Brachylagus idahoensis) at 2 scales (patch and microsite) to evaluate the influence of both structural properties of cover and visual properties (concealment and visibility) on habitat use by prey. We contrasted vegetation structure at paired used and unused patches. At each patch, we measured concealment and viewshed (i.e., visibility) in 3 orientations (i.e., aerial, terrestrial, and overall) and structural density using lidar. We also measured heights of the 3 tallest shrubs. Additionally, within used patches, we assessed the density of fecal pellets as an index of intensity of use and also measured distance to nearest burrow. At the patch scale, rabbits selected for structural properties of cover (dense vegetation and tall shrubs), but not visual properties of cover. Pygmy rabbits more intensively used microsites associated with high terrestrial concealment and in proximity to burrows. Our results suggest that pygmy rabbits may perceive greater threat from terrestrial as opposed to aerial predators at both scales, and they also indicate a nuanced relationship between properties of cover and habitat use.

Interpopulation and seasonal variations in habitat and microhabitat use of Vipera ammodytes (Linnaeus, 1758)

Despite the abundant data on habitat use of Vipera ammodytes, most studies are purely descriptive, merely listing the habitats in which the species is most often found. More complete studies evaluating the habitat preference of the species are lacking. The intraspecific variation (i.e., interpopulation or seasonal) in habitat and microhabitat utilization of the species also remains a poorly studied topic. In the current study, we assessed the general patterns of habitat and microhabitat use of V. ammodytes and their interpopulation and seasonal variations, based on habitat/microhabitat availability. To achieve that, we studied five different populations along a latitudinal gradient in western Bulgaria. In all of the studied areas, V. ammodytes showed a clear preference for various stony and rocky habitats and microhabitats, overgrown with herbaceous and shrub vegetation, while it avoided bare habitats, dark deciduous forests as well as cultivated agricultural lands. There were clear interpopulation and seasonal variations in habitat and microhabitat preference and spatial niche utilization. Our results suggest that habitat and microhabitat use of V. ammodytes depends on a combination of many factors such as season, locally specific characteristics like habitat structure and availability, population dynamics, food availability, physical and microclimatic conditions, and possibly on the extent of the interspecific competition

Landscape metrics predict habitat redundancy of restored oyster reefs for recruitment enhancement of dominant estuarine fish

Abstract Structured biogenic habitats in estuarine and coastal landscapes (or seascapes) augment nekton species' production; yet, landscape setting may make restored habitats functionally redundant to co‐occurring habitats for some species. Few relationships between recruitment enhancement and continuous landscape metrics have been quantified, limiting our ability to incorporate functional redundancy into restoration practice. To address this gap, we quantified two landscape metrics, per cent structure of proximal habitat and near distance to co‐occurring structured habitats, for experimentally restored oyster reefs in an intertidal landscape in Middle Marsh, North Carolina, USA. We then examined relationships between each landscape metric and recruitment enhancement of juvenile pinfish (Lagodon rhomboides), a species that uses multiple biogenic habitats and has high site fidelity as juveniles. We estimated that reefs with <33% proximal structured habitat within 15 m and <59% within 50 m contributed to recruitment enhancement, as defined by greater juvenile pinfish abundances at reefs than controls and no overlap in 95% confidence intervals. Additionally, functional redundancy, assigned according to per cent structure of proximal habitat within 15 or 50 m of restored reefs, reduced estimates of nekton recruitment enhancement in this experimental landscape by 58.3% or 33.3%, respectively. Estimates of nekton production augmented by restoration may be inflated if they have not been adjusted to account for habitat redundancy. Synthesis and applications. Landscape metrics offer some predictive capacity to help restoration practitioners avoid habitat redundancy for recruitment enhancement and extend beyond considering individual habitats toward integrating landscape scale processes into predictions and restoration practice. We demonstrated a straightforward process for restoration practitioners to identify where habitats may be redundant and incorporate the landscape into restoration siting decisions: delineate co‐occurring structured habitat with publicly accessible orthoimagery and model juvenile nekton relationships with proximal percent structure and near distance to other structured habitats.

A Simple Neural Network for Estimating Fine Sediment Sources Using XRF and XRD

Suspended sediment (SS) has a wide range of negative effects such as increased water turbidity, altered habitat structures, sedimentation, and effects on hydraulic systems and environmental engineering projects. Nevertheless, the methods for accurately determining SS sources on a basin-scale are poorly understood. Herein, we used a simplified neural network analysis (NNA) model to identify the sources of SS in Japan’s Oromushi River Catchment Basin. Fine soil samples were collected from different locations of the catchment basin, processed, and separately analysed using X-ray fluorescence (XRF) and X-ray diffraction (XRD). The sampling stations were grouped according to the type of soil cover, vegetation type and land-use pattern. The geochemical components of each group were fed into the same neural network layer, and a series of equations were applied to estimate the sediment contribution from each group to the downstream side of the river. Samples from the same sampling locations were also analysed by XRD, and the obtained peak intensity values were used as the input in the NNA model. SS mainly originated from agricultural fields, with regions where the ground is covered with volcanic ash identified as the key sources through XRF and XRD analysis, respectively. Therefore, based on the nature of the surface soil cover and the land use pattern in the catchment basin, NNA was found to be a reliable data analytical technique. Moreover, XRD analysis does not incorporate carbon, and also provides detailed information on crystalline phases. The results obtained in this study, therefore, do not depend on seasonal uncertainty due to organic matter.

Comparative analysis of habitat structure and macroinvertebrate assemblages in headwater streams of Odzi sub-catchment, Chimanimani District, Zimbabwe, post Cyclone Idai-induced flooding

Flooding results in short and long-term modifications of aquatic ecosystem structure and biodiversity. Cyclone Idai, which ravaged through Zimbabwe in 2019, had devastating consequences on aquatic ecosystems. However, the extent of habitat modification and consequent biodiversity shifts are unknown. This study focuses on the comparative analysis of (i) habitat structure and (ii) macroinvertebrate assemblages in headwater streams of the Odzi sub-catchment, Chimanimani District, Zimbabwe, specifically examining the conditions post-Cyclone Idai-induced flooding. Field sampling was conducted in the dry season (September−November) 2019 and wet season (January−March) 2020. Headwater streams of the Murare (first order), Umvumvumvu (first and second order) and Nyanyadzi (first and second order) rivers were sampled. Habitat assessment was done following the Benthic Macroinvertebrate Monitoring Protocol Implementation Plan. Selected water variables were measured using appropriate probes. Macroinvertebrate assemblage data were collected using the South African Scoring System (SASS 5) protocol. Spatiotemporal variations in water quality, habitat structure and macroinvertebrate metrics were assessed using two-way ANOVA, ANOSIM and SIMPER. Significant spatiotemporal heterogeneity (p < 0.05) was detected in temperature, turbidity, conductivity and total dissolved solids, velocity and depth regimes, channel flow status, sediment deposition, channel alteration and frequency of riffles for the three rivers. Habitat quality ascending hierarchical order was: Umvumvumvu > Murare > Nyanyadzi after Cyclone Idai induced flooding. The highest macroinvertebrate composition diversity was detected in Murare River, the least flood-affected stream. The largest dissimilarity (ANOSIM, 75.3%) was between the Umvumvumvu and Nyanyadzi rivers. Macroinvertebrate community structure differed significantly because of species uniqueness and heterogenous tolerance to changes in environmental conditions after flooding. Flooding intensity and duration induces dissimilar environmental tolerances and persistent macroinvertebrates communities in lotic systems across local catchment scales. Long-term assessment of water quality impairment, resilient functional feeder groups and rifflescale physical habitat structure are imperative for optimised micro-scale conservation of macroinvertebrates in headwater streams prone to flash flooding.

Impact of Climate Deviation on Reproductive Profile of Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758) from the Tons River, India

Nile tilapia, Oreochromis niloticus is among the leading farmed species around the world as well as a powerful invader in many countries globally. Studies were undertaken during the period from February 2019 to January 2020 from the lower stretch of the Tons River at Prayagraj, Uttar Pradesh, India. During the sampling period, 683 fish specimens of Nile Tilapia, Oreochromis niloticus (336 males and 347 females) were collected and studied for evaluation of sex ratio and sex structure. The sex ratios of male and female fishes were very close and reported 1.0:1.03 in the stock. The male ratio was higher in the small size group of fish with 81 to 200 mm size groups and 411 to 470 mm size group. The sex structure of males and females was observed at 49.19% and 50.81%, respectively in the case of stock. The female proportion was recorded as a minimum with 37.50% in the 441-470 cm size group and highest with 54.84% in the 381-410 mm size group. However, the male proportion was reported lowest at 45.16% in the 381-410 mm size group and highest at 62.50% in the 441-470 mm size group. In the present findings, O. niloticus was found to reach maturity starting below 138 mm of total length, taking individual fish. The fishes breed in the months of March to June and September to November of the year. The number of eggs per individual ranged from 393 to 4338 in the size of fish varied from 138-452 mm. The reported fecundity and sex ratio of O. niloticus indicated that the climatic condition or environmental condition of the Tons River was most suitable. The environmental condition (especially temperature) of the Tons River at Prayagraj is slightly warm compared to the Ganga River which is very favourable for O. niloticus. The water current velocity of the Tons River is very poor. Both parameters are very helpful for the stability of O. niloticus in the Tons River at Prayagraj. The high fecundity of O. niloticus in the Tons River at Prayagraj could probably be a result of a combination of different causes such as climatic conditions, habitat structure, food abundance, water quality, and quality of food. Therefore, the present study aimed to update the information on the sex ratio, sex structure, and fecundity of O. niloticus with respect to climate from the Tons River, India.

Clonality contributes to the spread of Avrainvillea lacerata (Bryopsidales, Chlorophyta) in Hawai'i.

The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, asexual reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblages since its discovery in 1981 offshore of O'ahu, Hawai'i. Field observations suggest this species is spreading via vegetative reproduction. To characterize the reproductive system of A. lacerata in Hawai'i, we developed seven microsatellite loci and genotyped 321 blades collected between 2018 and 2023 from three intertidal sites at Maunalua Bay and 'Ewa Beach. We observed one to four alleles at multiple loci, suggesting A. lacerata is tetraploid. Each site was characterized by high genotypic richness (R > 0.8). However, clonal rates were also high, suggesting the vegetative spread of A. lacerata plays a significant role. The importance of clonal reproduction for the persistence of A. lacerata in Hawai'i is consistent with the ecological data collected for this species and observations of other abundant macroalgal invaders in Hawai'i and other regions of the world. These data demonstrate the necessity for implementing appropriate population genetic methods and provide insights into the biology of this alga that will contribute to future studies on effective management strategies incorporating its reproductive system. This study represents one of the few that investigate green algal population genetic patterns and contributes to our understanding of algal reproductive system evolution.

Limited evidence for the influence of the physical structure and floristics of habitat on a boreal forest bird community

Studies conducted at regional and continental scales show that avian richness, community composition, and abundance are associated with variation in the vegetation physical structure and community composition (floristics) within broad habitat types. The relative contributions of physical structure and floristics are contested, and relationships are often taxon-specific. We used 110 microphone arrays deployed across 90 sampling locations and two breeding seasons to survey an avian community in the boreal forest in Labrador, Canada. Our objectives were (1) to describe the avian community of an underrepresented portion of the boreal forest, (2) to estimate the relationships between avian species richness and habitat characteristics, (3) to estimate if species detection at a given location was related to local habitat characteristics, and (4) to investigate the spatial and temporal patterns of the avian community composition. We detected 32 species at our sampling locations; physical structure and floristics were not related to avian species richness, although estimates of richness were higher on warmer days and lower on windier days. Habitat characteristics were associated with the detection of Boreal Chickadee (Poecile hudsonicus), Yellow-rumped Warbler (Setophaga coronata), American Robin (Turdus migratorius), and Black-throated Green Warbler (Setophaga virens). Finally, avian community composition was only moderately consistent among three categorical forest types and between audio sampling periods in two consecutive breeding seasons. Overall, we show that the structural and floristic traits measured at our study site are not related to the detection of most avian species or to species richness.

Benthic habitat mapping of the glass sponge (Vazella pourtalesii), and associated community composition on Sambro Bank, Scotian Shelf, Canada

Sponges have been identified as ecosystem engineers, providing habitat structure for many other benthic organisms, but are vulnerable to the impacts of bottom contact fishing. The Sambro Bank Sponge Conservation Area (SBSCA) protects a globally unique aggregation of the glass sponge (Vazella pourtalesii) off the east coast of Canada. Here, we present the first comprehensive, high-resolution mapping study of this site. Multispectral multibeam echosounder (MBES) mapping at three operating frequencies and benthic drop camera surveys were conducted at the SBSCA in 2022. Video data were analysed to quantify the abundance and location of V. pourtalesii and all associated benthic fauna and sediment characteristics. Using the MBES data as predictor variables, the study created a generalized linear mixed model of V. pourtalesii presence in the SBSCA, with 90.1% accuracy. Four seafloor benthoscape classes were identified from the video imagery, with statistically distinct benthic macrofaunal communities associated with each class. The study creates a baseline assessment of the current community composition and habitat characteristics of the site, which can be used for future ecological monitoring and management.

Flammulated Owls Exhibit Diel Variation in Space Use

ABSTRACT A home range determines the resources animals can access, and the size of a home range often reflects resource availability and energetic requirements of individuals. The Flammulated Owl (Psiloscops flammeolus) is a cryptic small forest owl that breeds in mixed conifer forests in western North America. The home ranges of individuals generally comprise open forests with large trees, but we have yet to fully understand temporal variation in this species’ use of space and the habitat structures that drive space use at a fine scale. During the 2017 summer breeding season (May–July), we tracked the movement of six territorial males with GPS tags to estimate temporal variation in space use and examined resource selection for fine-scale habitat characteristics within home ranges. Results suggest that individual movement was more constrained around nests early at night, but the area of space used was consistent between the incubation and nestling stages. The owls’ activity centers near their nests had denser ground cover than available habitat, indicating that the forest understory may be valuable for this species’ breeding ecology. As forested landcover rapidly changes in western North America, understanding the spatial behavior and fine scale habitat associations of this species and others is increasingly important.

Characteristics of Phytoplankton Community Structure in Lakes of Wetlands Dominated by Different Aquatic Plants and Its Driving Factors

In wetland ecosystems, small shallow lakes are critical transition zones of land and water, which are usually dominated by aquatic plants with different growth forms. However, the differences and key influencing factors of phytoplankton communities in shallow lakes dominated by different aquatic plants are unclear. On this basis, nine surveys were conducted at five sampling sites of three lakes in Zhangye National Wetland Park from June to November in 2022, which were respectively dominated by the emergent Phragmites australis （LL）, the submerged Potamogeton perfoliatus （CL）, and the floating-leaved Nymphaea tetragona （SL）. During the study period, the three lakes showed obvious habitat differences. A total of 237 species of phytoplankton in seven phyla and 93 genera were identified in the three lakes, including 189 species, 151 species, and 147 species in the LL, CL, and SL lakes, respectively. Among them, Ulnaria acus, Scenedesmus quadricauda, Achnanthidium minutissimum, Nitzschia stagnorum, Navicula radiosa, and Gymnodinium aeruginosum were shared dominant species of all three lakes, indicating that they had strong environmental adaptability, whereas Navicula lanceolala, Encyonopsis cesatii, and Eunotia diodon and Cymbella aequalis were only dominant in the CL, LL, and SL lakes, respectively. Simultaneously, these dominant algae appeared with obviously distinct statuses of niche width, niche overlap, and interspecific correlation among the three lakes. Using principal coordinate analysis （PCoA） and permutational multivariate analysis of variance （PERMANOVA）, significant differences were found in algal community composition among the three lakes （P<0.001）. Multiple regression on （dis）similarity matrices analysis （MRM） showed that the heterogeneity of phytoplankton communities among the three lakes was positively affected by NO3--N and pH and negatively affected by dissolved oxygen （DO） and was closely positively correlated with the abundance of six dominant species, namely, S. quadricauda, U. acus, N. stagnorum, Pseudoanabaena sp., Merismopedia punctata, and A. minutissimum. These results indicate that aquatic plants with different growth types could affect the composition, structure, and stability of phytoplankton communities in the same habitat with them by shaping their habitat heterogeneity. Therefore, selecting specific growth types of aquatic plants for aquatic ecosystem restoration in wetland construction and management will be conducive to regulate the state of water habitat and phytoplankton community structure effectively.

Habitat structure and an introduced predator limit the abundance of an endangered ground-nesting bird.

Understanding the factors that limit the abundance of threatened species is critical for the development of effective conservation strategies. However, gaining such knowledge from monitoring programs and using it to inform decision-making for rare species can be difficult due to methodological issues posed by the problems of distinguishing true absences from false absences and the analysis of datasets dominated by zero counts. The plains-wanderer (Pedionomus torquatus) is a critically endangered ground-nesting bird that occurs in grasslands of southeastern Australia. Decline of the plains-wanderer has been attributed to habitat modification but little emphasis has been placed on the role of introduced predators, such as the red fox (Vulpes vulpes), which have had a devastating effect on small ground-dwelling vertebrates in dryland regions of Australia. Here, we use a 9-year time series of spotlight counts to investigate the impact of vegetation structure and fox presence on plains-wanderer occupancy and abundance. We used distance sampling to determine the effective strip width for sighting plains-wanderers during spotlight surveys. We then used a hurdle model approach whereby binomial generalized additive models were fitted to presence/absence data within the effective strip-width across all sites and negative-binomial models were fitted to an index of abundance at sites where plains-wanderers were observed. Plains-wanderer occupancy and abundance fluctuated markedly through time. Where foxes were absent, occupancy (but not abundance) of plains-wanderers showed a humped relationship with grass height with an optimal height between 50 and 150 mm. Where foxes were present however, this relationship broke down and plains-wanderers were rarely recorded. Our results suggest that plains-wanderers should benefit from management strategies that maintain grass height at optimal levels and exclude foxes or effectively suppress their populations. A key message from this study is that if statistical analyses of data generated by monitoring programs for rare species are intended to inform management decisions by identifying relationships between threatened species and drivers of their abundance, there should be consideration of analytic approaches that account for true and false zeroes, high prevalence of zeroes, and the possibility of nonlinear responses.

Water Quality Modeling of Wastewater Discharges for Prediction of Sediment Transport and Deposition in Surface Water

Sediment deposition in surface water bodies can have a range of significant impacts, affecting everything from the aquatic ecosystem to water quality and infrastructure. It can affect the availability of food sources for aquatic organisms; and change the physical structure of habitats, such as riverbeds and lake bottoms. It can equally smother aquatic plants and animals, leading to a decline in biodiversity. A model of the governing equations of particle motion and fluid flow was developed with COMSOL Multiphysics 5.3a. With a coefficient of determination of 0.99, the model result demonstrated good agreement after result validation using experimental data. According to study findings, sediments in the study area, Ele River move more slowly than sediments in the midstream which causes a high deposition of sediments at the river banks. This sediment deposition affects the irrigation system for crop production considering the ability of the sediments to block sprinkler nozzles which limits it from supplying sufficient water for the production of crops.