Primary Environmental Variables Research Articles

Spatial patterns in pelagic ciliate community responses to various habitats in the Amundsen Sea (Antarctica)

To investigate the impacts of climate change on environmental conditions and pelagic biodiversity, spatial patterns in pelagic ciliate communities were studied at 18 stations from five habitats in the Amundsen Sea (western Antarctic) during austral summer from December 2010 to January 2011. Clear spatial patterns were observed in community structure, and significant differences were found among the various habitats. The species number, abundance, biomass and biodiversity indices (Shannon diversity H′, Pielou’s evenness J′, and Margalef richness D) also showed clear spatial trends. Pelagic ciliate community structure accurately reflected environmental variability. Alone or in combination, several primary environmental variables were found to affect community spatial patterns in specific habitats. Shannon H′ and Margalef D showed strong relationships with spatial changes in chlorophyll a and might be better predictors in future Antarctic studies. This study presents the first detailed description of spatial patterns in pelagic ciliate communities and their correlations with environmental variability in habitats in the Amundsen Sea during early austral summer. Our findings provide detailed and basic data on the composition, distribution, and variation of ciliate communities in the Amundsen Sea, and will help answer important questions about polar ecosystems.

Modern distribution of ostracodes and other limnological indicators in southern Lake Malawi: implications for paleocological studies

This modern distribution study from the southwest arm of Lake Malawi quantitatively relates variables of the lake environment to surficial assemblages of ostracodes and other paleoenvironmental indicators (molluscs, Botryococcus, fish, and charcoal) from 102 sites, across a gradient of littoral to shallow profundal conditions. The goal of this research is to use the resultant relationships to help quantify paleoecological interpretations of the fossil record from sediment cores. Site locations varied by depth (1–60 m) and adjacent shoreline environment. Thirty-three ostracode species are identified from 54 sites including four new, undescribed species of Cypridopsinae (2) and Limnocythere (2). Ostracodes are extremely abundant between 1 and 25 m water depth, but are rare to absent between 30 and 60 m. This disappearance is probably taphonomically controlled, with carbonate dissolution in the death assemblage since abundant live ostracodes have been found in the lake at greater than 30 m depth, where bottom sediments lack calcium carbonate. Constrained correspondence analysis (CCA) of ostracode species abundance suggests depth and dissolved oxygen (DO) content to be the primary environmental variables affecting their distribution. Additional CCA models using all biological indicators suggest limnologic variables correlated with depth (e.g., bottom water temperature and DO) and adjacent shoreline environment were most significant.

Functional Traits Reveal Processes Driving Natural Afforestation at Large Spatial Scales

An understanding of the processes governing natural afforestation over large spatial scales is vital for enhancing forest carbon sequestration. Models of tree species occurrence probability in non-forest vegetation could potentially identify the primary variables determining natural afforestation. However, inferring processes governing afforestation using tree species occurrence is potentially problematic, since it is impossible to know whether observed occurrences are due to recruitment or persistence of existing trees following disturbance. Plant functional traits have the potential to reveal the processes by which key environmental and land cover variables influence afforestation. We used 10,061 survey plots to identify the primary environmental and land cover variables influencing tree occurrence probability in non-forest vegetation in New Zealand. We also examined how these variables influenced diversity of functional traits linked to plant ecological strategy and dispersal ability. Mean annual temperature was the most important environmental predictor of tree occurrence. Local woody cover and distance to forest were the most important land cover variables. Relationships between these variables and ecological strategy traits revealed a trade-off between ability to compete for light and colonize sites that were marginal for tree occurrence. Biotically dispersed species occurred less frequently with declining temperature and local woody cover, suggesting that abiotic stress limited their establishment and that biotic dispersal did not increase ability to colonize non-woody vegetation. Functional diversity for ecological strategy traits declined with declining temperature and woody cover and increasing distance to forest. Functional diversity for dispersal traits showed the opposite trend. This suggests that low temperatures and woody cover and high distance to forest may limit tree species establishment through filtering on ecological strategy traits, but not on dispersal traits. This study shows that ‘snapshot’ survey plot data, combined with functional trait data, may reveal the processes driving tree species establishment in non-forest vegetation over large spatial scales.

Informing conservation units: barriers to dispersal for the yellow anaconda

AbstractAimFine‐scale population structure is often unaccounted for in the delineation of conservation units, potentially compromising long‐term species persistence. Identifying biogeographic and environmental drivers of population boundaries is therefore of key conservation concern. We aimed to explore barriers to dispersal for the harvested yellow anaconda (Eunectes notaeus) using an ecological niche model. Our secondary aim was to test the relative geographic and environmental contributions of a multisource occurrence data set in species range predictions.LocationParaguay River drainage, central South America.MethodsWe developed an ecological niche model for the yellow anaconda using Maxent and a multisource species occurrence data set. Following nine iterations of model development, nine environmental variables were selected for model inclusion. We used the models to identify potential barriers to dispersal and employed jackknifing to identify the primary environmental variables that best explain barrier presence. We assessed the geographic and environmental overlap of models built with each data subset.ResultsCharacterization of suitable habitat was found to be most powerful in northern Argentina and southern Paraguay. A persistent barrier to dispersal was identified in northern Argentina and corresponded to the presence of dry Cambisol soils. Data subsets were found to contribute different information to the final model in terms of geographic and environmental space.Main ConclusionsEcologically meaningful barriers to dispersal support recent genetic hypotheses of population subdivision. These barriers should be considered when delineating species management units to ensure sustainable harvest levels. Multisource data sets may produce more powerful niche predictions and represent a useful resource for data‐poor species. Further, model results should be interpreted alongside complementary analyses for more effective conservation strategies.

Seasonality and environmental drivers of biological productivity on the western Hokkaido coast, Ishikari Bay, Japan

We report on a 16-month time series of the primary productivity, chlorophyll biomass and environmental variables in Ishikari Bay, the western Hokkaido coast, from September 2006 to December 2007. During productive summer and autumn seasons, the average phytoplankton biomass (as chlorophyll a) and productivity were 4.7 ± 0.4 μg Chl a L−1 and 229.2 ± 113.4 μg C L−1 d−1, and 5.9 ± 6.0 μg Chl a L−1 and 138.9 ± 202.6 μg C L−1 d−1, respectively. The water column salinity profiles suggested that nutrient upwelling from bottom waters, especially in summer and autumn, when autotrophic production was at a maximum, was the major source of nutrients fueling the productivity in near-surface waters. Size-fractionation measurements showed that the micro-size fraction (>10 μm) accounted for > 80% of the total phytoplankton biomass and productivity. The strong correlation of POC with Chl a (r = 0.875; P < 0.001; n = 16) suggests that living phytoplankton in POC may outweigh detrital and bacterial biomass. Stoichiometrical analysis of inorganic nutrients revealed a seasonal low (13) and high (25) DIN-to-PO4 ratio and a seasonal low (30) and high (37) Si-to-PO4 ratio, suggesting that phytoplankton growth was possibly limited by nitrate and phosphate and not by silicic acid. We conclude that bottom-advection of nutrients resulting from wind-driven mixing may have been a significant source of nutrient input in this oligotrophic coastal system, and zooplankton grazing or other losses might be a crucial factor in controlling the phytoplankton biomass and production, particularly in spring. Also, it is probable that phytoplankton growth was not prevented by insufficient light in Ishikari Bay considering the values of both mean light intensity in the mixed layer (Im) and the mixing and euphotic depth ratio (Zmix:Zeu).

The rare species Synura lapponica (Synurophyceae) new to the Czech Republic, local vs. global diversity in colonial synurophytes

Synura lapponica Skuja, a freshwater colonial flagellate (Synurophyceae, Stramenopila), has been reported for the first time in the Czech Republic. This study evaluates the ecological requirements of the species, and includes a survey of the literature. Although S. lapponica has been reported thus far only in the Northern Hemisphere, the probability of its bipolar distribution is relatively high (22%). Distribution is probably ecologically determined, water temperature (correlated with latitude or seasonal fluctuations), and lower pH seem to be the primary environmental variables. A local vs. global ratio reflects, to a certain extent, the degree of sampling effort expended in the studied area, but a considerable increase in the number of revealed taxa was apparent when the area was expanded.

Effects of Air Temperature, Relative Humidity, and Wind Speed on Water Vapor Transmission Rate of Fabrics

The primary environmental variables which influence the water vapor transmission rate of fabrics include air temperature, relative humidity, and wind speed. The combined quantitative effects of air temperature, relative humidity, and wind speed have been explored. The air temperature varied from 10 °C to 30 °C in 5 °C-intervals. The relative humidity ranged from 0% to 50%. The wind speed was from 0.1 m/s to 0.4 m/s. A new test method was employed to measure the water vapor transmission rate of four typical fabrics exposed under 120 conditions of combinations of relative humidity and wind speed with air temperature. The results showed that high air temperature, low relative humidity, and high wind speed led to high water vapor transmission rate. The exponential equations were obtained from the whole database based on the multiple nonlinear regression analysis, resulting in a generalized quantitative description of various effects on the water vapor permeability of fabrics. The prediction quality was good, as the regression equations provided high correlation coefficients and low standard errors of the estimate. The prediction values from the regression equations agreed well with the experimental results.

WHICH ENVIRONMENTAL VARIABLES BETTER EXPLAIN CHANGES IN ANURAN COMMUNITY COMPOSITION? A CASE STUDY IN THE RESTINGA OF MATA DE SÃO JOÃO, BAHIA, BRAZIL

Most studies of amphibian communities are restricted to aquatic environments, which precludes sound descriptions of changes in composition throughout entire habitats. Moreover, few works focus on the environmental processes that shape the composition of these communities, particularly in tropical ecosystems. In this study, we investigated which environmental variables were able to predict the main changes in anuran community composition in a shrub-to-forest Restinga on the northeastern coastline of Bahia State, Brazil. In 30 plots (60 × 25 m) along a continuous Restinga area, we determined, over two consecutive rainy seasons, the abundances of anuran species and 20 primary environmental variables. We represented the main environmental gradients of the Restinga using the first axes derived from a principal component analysis (PCA) of the matrix of environmental variables. We represented the main changes in community composition using a synthetic axis built by applying the nonmetric multidimensional scaling...

Environmental determinants of vascular plant species richness in the Austrian Alps

AbstractAim To test predictions of different large‐scale biodiversity hypotheses by analysing species richness patterns of vascular plants in the Austrian Alps.Location The Austrian part of the Alps (c. 53,500 km2).Methods Within the floristic inventory of Central Europe the Austrian part of the Alps were systematically mapped for vascular plants. Data collection was based on a rectangular grid of 5 × 3 arc minutes (34–35 km2). Emerging species richness patterns were correlated with several environmental factors using generalized linear models. Primary environmental variables like temperature, precipitation and evapotranspiration were used to test climate‐related hypotheses of species richness. Additionally, spatial and temporal variations in climatic conditions were considered. Bedrock geology, particularly the amount of calcareous substrates, the proximity to rivers and lakes and secondary variables like topographic, edaphic and land‐use heterogeneity were used as additional predictors. Model results were evaluated by correlating modelled and observed species numbers.Results Our final multiple regression model explains c. 50% of the variance in species richness patterns. Model evaluation results in a correlation coefficient of 0.64 between modelled and observed species numbers in an independent test data set. Climatic variables like temperature and potential evapotranspiration (PET) proved to be by far the most important predictors. In general, variables indicating climatic favourableness like the maxima of temperature and PET performed better than those indicating stress, like the respective minima. Bedrock mineralogy, especially the amount of calcareous substrate, had some additional explanatory power but was less influential than suggested by comparable studies. The amount of precipitation does not have any effect on species richness regionally. Among the descriptors of heterogeneity, edaphic and land‐use heterogeneity are more closely correlated with species numbers than topographic heterogeneity.Main conclusions The results support energy‐driven processes as primary determinants of vascular plant species richness in temperate mountains. Stressful conditions obviously decrease species numbers, but presence of favourable habitats has higher predictive power in the context of species richness modelling. The importance of precipitation for driving global species diversity patterns is not necessarily reflected regionally. Annual range of temperature, an indicator of short‐term climatic stability, proved to be of minor importance for the determination of regional species richness patterns. In general, our study suggests environmental heterogeneity to be of rather low predictive value for species richness patterns regionally. However, it may gain importance at more local scales.

Spawning Migration of Lacustrine-Adfluvial Bull Trout in a Natural Area

We investigated the spawning migration of lacustrine-adfluvial bull trout Salvelinus confluentus in the North Fork Skokomish River in Olympic National Park (Washington State) during 1996. Day-snorkeling and electrofishing were conducted to determine timing and duration of the migration and the distribution and abundance of bull trout. The primary spawning migration began in early October and was waning by December. Bull trout migrated 6 km or less up the river from Lake Cushman. Increased river discharge and decreased water temperature appeared to be the primary environmental variables corresponding to the initiation of the migration. Mean length of migratory bull trout increased from June to December. Comparisons with other lacustrine-adfluvial bull trout populations in Oregon, Montana, Idaho, and British Columbia suggested that these populations exhibit specific migratory strategies related to local environmental conditions.

Foraminifera from the continental slope off Cape Hatteras, North Carolina

Abstract The recent benthic meiofaunal foraminiferal assemblage from the continental slope (590-2 003 m) off Cape Hatteras, North Carolina exhibits high species richness and evenness, moderate diversity values, and lacks numerically dominant species. The preserved planktic assemblage has relatively low species richness, high evenness, low diversity, and a few numerically dominant species. Approximately 9% of the benthic species are those that typically live within continental shelf depth ranges. The benthic assemblage abundances and diversities do not follow depth patterns or geophysical characteristics. No biogeographic boundary can be described within the study area for meiofaunal foraminifera. Oxygen limitation does not appear to be a factor affecting the benthos of the North Carolina continental slope based upon the community structure of the benthic foraminifera, if total assemblage is assumed to reflect the recently living community. The high carbonate content of sediments in the area may be explained by foraminiferal tests. Within the study area, the foraminiferal assemblages are uniform, and probably reflect relative consistency of primary environmental variables as well as dynamic downslope transport and high influx of material from the water column in the vicinity where the Gulf Stream and the Western Boundary Undercurrent cross.

Gas exchange processes of yellow-cedar (Chamaecyparis nootkatensis) in response to environmental variables

Yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) gas exchange processes were measured in response to the following primary environmental variables: photosynthetically active radiation, vapour pressure deficit, root temperature, and soil moisture. Under nonlimiting edaphic conditions, maximum stomatal conductance and maximum CO2 assimilation increased rapidly as photosynthetically active radiation increased from 0 to 200 μmol∙m−2∙s−1 and from 0 to 500 μmol∙m−2∙s−1, respectively. Thereafter, greater photosynthetically active radiation levels only resulted in minor increases in stomatal conductance and CO2 assimilation. Maximum stomatal conductance and maximum CO2 assimilation declined in a concave manner as vapour pressure deficit increased from 1 to 5 kPa. Response surface model for stomatal conductance showed vapour pressure deficit was the primary influence after light had caused initial stomatal opening. Response surface modeling approach showed CO2 assimilation increased as photosynthetically active radiation increased, but increased vapour pressure deficit resulted in a suppression of CO2 assimilation. Response surface model showed internal CO2 concentration declined sharply as photosynthetically active radiation increased from 0 to 500 μmol∙m−2∙s−1, but it remained constant with increasing vapour pressure deficit. Decreasing root temperature resulted in a continual decline in CO2 assimilation and stomatal conductance from 22 to 1 °C, while internal CO2 concentration declined from 22 to 13 °C with little change between 13 and 1 °C. As predawn shoot water potential decreased from −0.5 to −2.0 MPa, CO2 assimilation declined in a linear manner, while stomatal conductance and internal CO2 concentration declined in a concave manner. Key words: Chamaecyparis nootkatensis, CO2 assimilation, stomatal conductance, internal CO2 concentration, photosynthetically active radiation, vapour pressure deficit, root temperature, predawn shoot water potential.

Enhanced primary production at the plume/oceanic interface of the Mississippi River

Mechanistic and empirical models were used to examine relationships between primary production and environmental variables along the Mississippi River plume/oceanic gradient off Southwest Pass, Louisiana. A large proportion of variation in primary production could be explained on the basis of light and biomass ( r 2 > 0.857, N > 25). However, comparison of observed chlorophyll concentrations with those predicted using a steady-state light limitation model suggested factors in addition to light availability constrained maximum biomass levels in the plume. Factors which may have contributed to low observed biomass included growth limitation or inhibition by substances not measured, losses due to grazing and sinking, and a short residence time for plume waters, which may have prevented populations from reaching steady state. The dissipative effects associated with plume/oceanic mixing may have been enhanced by potential inhibitory effects of large and varying salinity gradients. Nutrient-salinity distributions, in conjunction with approximate calculations of primary consumption of riverine nutrient sources by phytoplankton, led to the conclusion that biomass and production were controlled by nutrient supply at salinities above 30.

Primary Production in a Tidally Energetic Fjord: Evidence of Seasonal and Inter-annual Tidal Forcing

A long term data set collected from a tidally energetic sill fjord was analyzed for its statistical relationships between primary production indices and several represented environmental variables. The analysis identified variance and covariance structure in these variables implicating changes in water column clarity, in inter-annual variability of phytoplankton carbon uptake rate, and the static stability of basin surface water in phytoplankton standing stock. The biomass–stability relationship was found to be seasonally dependent, with biomass positively correlated with stability in the summer and negatively correlated in the spring/fall, and restricted to waters under the direct mixing influence of the tidal inflow jet. These statistical patterns are discussed in terms of a possible control of primary production by seasonal and inter-annual variations in tidal inflow buoyancy.

Regional patterns of polymorphisms in natural populations of Avena barbata

A detailed survey of polymorphisms at two morphological marker loci (B/b for lemma color and Ls/ls for leafsheath hairiness) was carried out in natural populations of Avena barbata from California. Based on the degrees of polymorphisms at both loci, four major regions (I, II, III, IV) were recognized. The central-north coastal region I was highly polymorphic at both loci, whereas the south-coastal region IV was monomorphic for genotype BB lsls. Inland valley region III was also largely monomorphic for the same genotype. Except region II in which founder effects seemed to have played a significant role leading to low amounts of polymorphism and large differentiations among isolated small populations, temperatures on the east–west axis, and precipitation on the north–south axis appeared to be the primary environmental variables associated with the regional patterns of polymorphisms.Key words: Avena barbata, polymorphism, environmental associations

Denaturation studies on prostatic acid phosphatase

The heat denaturation of prostatic acid phosphatase has been studied in a controlled system, as a function of a number of primary environmental variables. The factors of ionic strength and variations in protein concentration were shown to be negligible or controllable. The nature of anion in the buffer system profoundly affects the denaturation rate. The multivalent anions accelerate the rate rapidly for increasing low molarities, whereas the rates decrease after passing through a maximum for higher concentrations. Ions of lower valency give rates increasing with concentration, with no maxima. The activation energy is constant regardless of buffer or pH used.