Environmental Stability and Long-term Variability of Harpacticoid Copepod Assemblages

Harpacticoid copepods of the Chernaya Bay (White Sea) intertidal zone were collected in 45 surveys carried out from spring to autumn over a 25-year period (1996-2020) at three sites that differed in sediment properties. There were no significant long-term trends or seasonal cycles in total abundance. Regarding the species composition, the differences between sites were the most important source of variability over the whole period while the fine-scale (within-habitat) variability was low. Epibenthic species prevailed in fine silty sand, both burrowing and epibenthic species prevailed in medium sand, and interstitial and burrowing species prevailed in coarse sand. A comparison of the data on harpacticoid assemblages from a number of geographically remote loci corroborated the generality of this pattern. In the temporal dimension, the structure of each community was stable until the early 2000s, when the proportion of epibenthic, burrowing and interstitial species changed following changes in sediment properties (increasing siltation at sandy sites and decreasing siltation at the silty site). At each site, there was an increasing long-term trend in diversity (both in total richness and in expected species number). This increase was particularly apparent at sandy sites because of the appearance of epibenthic species. We suggest that sediment composition is the key factor determining the composition of harpacticoid assemblages in space and time. The “ecomorphological profile”, i.e., the proportion of species with different lifestyle and morphological traits, is a useful and informative indicator for describing and typifying these assemblages.

Impact of habitat variability on growth dynamics of Bergenia ciliata (Haw.) Sternb. along an altitudinal gradient in Kashmir Himalaya

Bergenia ciliata (Haw.) Sternb. is an important medicinal plant of the Himalayan region. Phenotypic attributes of a particular plant species varies along different altitudes in order to adapt and to overcome the changeable and stressful conditions. A number of environmental factors such as mean temperature, precipitation, soil characteristics, radiation intensity etc. changes with altitudinal gradient and thereby affect the morphological pattern of a plant species. The present study was undertaken to reveal the impact of the elevational gradient and habitat variability on the morphological features of the selected species. Under different environmental conditions the species exhibited enormous variability in its phenotypic traits. The plants were shorter at high altitude site, Gulmarg while the plants of low altitude site, Kashmir University Botanical Garden (KUBG) were taller and more vigorous. A significant decrease in the plant height, inflorescence length, leaf length, leaf breadth and petiole length occurred with increasing altitude. Principal component analysis (PCA) revealed that the habitat of KUBG and Ferozpora (Tangmarg) proved relatively better for the growth of B. ciliata. The regression analysis revealed positive correlation between plant height and traits like inflorescence length, leaf length, leaf number and thus predicting a direct impact of plant height on other traits. Our findings present a comprehensive account on the variability of phenotypic characteristics, in relation to the environmental conditions of this valuable medicinal plant species.

CONTRIBUTION TO KNOWLEDGE ON THE VARIABILITY OF AROLLA PINE WOODLANDS OF THE NORTH-EASTERN TATRA MOUNTAINS

Knowledge of the overall syntaxonomic and habitat variability of forest communities with Arolla pine (Pinus cembra) within the Tatra Mountains (Western Carpathians) is still insufficient as field research was hindered by their hardly accessible localities and deforestation for high mountain grazing. Arolla pine woodlands were traditionally classified within the association Pino cembrae-Piceetum Myczkowski et Lesinski 1974, but recent surveys recognize more numerous units. Hitherto unpublished releves from the north-eastern part of the Tatra Mountains document the occurrence of several floristically and ecologically distinct Arolla pine communities: (1) acid woodland of Homogyno alpinae-Pinetum cembrae on nutrient-poor habitats over quartzitic bedrock, and (2) calcareous woodlands of species-poor Pyrolo rotundifoliae-Pinetum cembrae of sites with a well-developed, tangled humus soil horizon, Cystopterido montanae-Pinetum cembrae on habitats influenced by both limestones and quartzites, Primulo elatioris-Pinetum cembrae bound to sites with the most favourable humidity, and Seslerio tatrae-Pinetum cembrae with the most pronounced calcareous character.

A Process-Based Model with Temperature, Water, and Lab-derived Data Improves Predictions of Daily Mosquito Density

While the number of human cases of mosquito-borne diseases has increased in North America in the last decade, accurate modeling of mosquito population density has remained a challenge. Longitudinal mosquito trap data over the many years needed for model calibration is relatively rare. In particular, capturing the relative changes in mosquito abundance across seasons is necessary for predicting the risk of disease spread as it varies from year to year. We developed a process-based mosquito population model that captures life-cycle egg, larva, pupa, adult stages, and diapause for Culex pipiens and Culex restuans mosquito populations. Mosquito development through these stages is a function of time, temperature, daylight hours, and aquatic habitat availability. The time-dependent parameters are informed by both laboratory studies and mosquito trap data from the Greater Toronto Area. The model incorporates city-wide water-body gauge and precipitation data as a proxy for aquatic habitat. This approach accounts for the nonlinear interaction of temperature and aquatic habitat variability on the mosquito life stages. We demonstrate that the full model predicts the yearly variations in mosquito populations better than a statistical model using the same data sources. This improvement in modeling mosquito abundance can help guide interventions for reducing mosquito abundance in mitigating mosquito-borne diseases like the West Nile virus.

Survival of a threatened salmon is linked to spatial variability in river conditions

Extirpation of the Central Valley spring-run Chinook Salmon ESU (Oncorhynchus tshawytscha) from the San Joaquin River is emblematic of salmonid declines across the Pacific Northwest. Habitat restoration and fish reintroduction efforts are ongoing, but recent telemetry studies have revealed low outmigration survival of juveniles to the ocean. Previous investigations have focused on modeling survival relative to river discharge and geographic regions, but have largely overlooked the effects of habitat variability. To evaluate the link between environmental conditions and survival of juvenile spring-run Chinook Salmon, we combined high spatial resolution habitat mapping approaches with acoustic telemetry along a 150 km section of the San Joaquin River during the spring of 2019. While overall outmigration survival was low (5%), our habitat-based classification scheme described variation in survival of acoustic-tagged smolts better than other candidate models based on geography or distance. There were two regional mortality sinks evident along the longitudinal profile of the river, revealing poor survival in areas that shared warmer temperatures but that diverged in chlorophyll-α, fDOM, turbidity and dissolved oxygen levels. These findings demonstrate the value of integrating river habitat classification frameworks to improve our understanding of survival dynamics of imperiled fish populations. Importantly, our data generation and modeling methods can be applied to a wide variety of fish species that transit heterogeneous and diverse habitat types.

Confluences and Land Cover As Agents of Change: Temporal Habitat Variability Modifies the Movement and Assemblage Change of Headwater Fishes

Interspersed inputs of wood and sediment brings about morphological change at confluences and the extent to which these processes are modified by anthropogenic disturbance has ramifications for stream fish assemblages. In this study, we use three functional groups of headwater fishes to assess the influences of confluence size and land cover on habitat stability, distance moved, movement rate, and assemblage change in a Gulf Coastal Plain drainage in the southeastern United States using a 2X2 design. Our results suggest that differences in habitat stability were described by a hydrogeomorphic gradient, and urban reaches characterized by a confluence size > 0.6 displayed the greatest habitat instability. Water-column specialists in urban reaches were more likely to move when habitat change was limited, whereas movement by this functional group in forested reaches was more likely in response to greater habitat instability. Therefore, the distance moved by water-column specialists was related to land cover. Assemblage change also occurred at a more constant rate in urban reaches in response to habitat instability. There was little evidence that confluence size influenced movement or assemblage stability in these headwater assemblages. Our understanding of the extent to which land cover alters the geomorphic and ecological gradients associated with headwater confluences will be critical to ensure the conservation of sensitive species whose fitness is dependent on the integrity of these habitats.

Riparian and in-channel habitat properties linked to dragonfly emergence

In freshwater ecosystems, habitat alteration contributes directly to biodiversity loss. Dragonflies are sentinel species that are key invertebrate predators in both aquatic (as larvae) and terrestrial ecosystems (as adults). Understanding the habitat factors affecting dragonfly emergence can inform management practices to conserve habitats supporting these species and the functions they perform. Transitioning from larvae to adults, dragonflies leave behind larval exoskeletons (exuviae), which reveal information about the emergent population without the need for sacrificing living organisms. Capitalizing on Atlantic Canada’s largest freshwater wetland, the Grand Lake Meadows (GLM) and the associated Saint John/Wolastoq River (SJWR), we studied the spatial (i.e., across the mainstem, tributary, and wetland sites) and temporal (across 3 years) variation in assemblages of emergent dragonflies (Anisoptera) and assessed the relative contribution of aquatic and terrestrial factors structuring these assemblages. The GLM complex, including the lotic SJWR and its tributaries and associated lentic wetlands, provided a range of riparian and aquatic habitat variability ideal for studying dragonfly emergence patterns across a relatively homogenous climatic region. Emergent dragonfly responses were associated with spatial, but not temporal, variation. Additionally, dragonfly communities were associated with both aquatic and terrestrial factors, while diversity was primarily associated with terrestrial factors. Specific terrestrial factors associated with the emergence of the dragonfly community included canopy cover and slope, while aquatic factors included water temperature, dissolved oxygen, and baseflow. Our results indicate that management of river habitats for dragonfly conservation should incorporate riparian habitat protection while maintaining aquatic habitat and habitat quality.

Inter-Habitat Variability in Parrotfish Bioerosion Rates and Grazing Pressure on an Indian Ocean Reef Platform

Parrotfish perform a variety of vital ecological functions on coral reefs, but we have little understanding of how these vary spatially as a result of inter-habitat variability in species assemblages. Here, we examine how two key ecological functions that result from parrotfish feeding, bioerosion and substrate grazing, vary between habitats over a reef scale in the central Maldives. Eight distinct habitats were delineated in early 2015, prior to the 2016 bleaching event, each supporting a unique parrotfish assemblage. Bioerosion rates varied from 0 to 0.84 ± 0.12 kg m−2 yr−1 but were highest in the coral rubble- and Pocillopora spp.-dominated habitat. Grazing pressure also varied markedly between habitats but followed a different inter-habitat pattern from that of bioerosion, with different contributing species. Total parrotfish grazing pressure ranged from 0 to ~264 ± 16% available substrate grazed yr-1 in the branching Acropora spp.-dominated habitat. Despite the importance of these functions in influencing reef-scale physical structure and ecological health, the highest rates occurred over less than 30% of the platform area. The results presented here provide new insights into within-reef variability in parrotfish ecological functions and demonstrate the importance of considering how these interact to influence reef geo-ecology.