Biomass production,total protein,chlorophylls, lipids and fatty acids of freshwater green and blue-green algae under different nitrogen regimes

Two green algae (Chlorella vulgaris and Scenedesmus obliquus) and four blue-green algae (Anacystis nidulans, Microcystis aeruginosa, Oscillatoria rubescens and Spirulina platensis) were grown in 81 batch cultures at different nitrogen levels. In all the algae increasing N levels led to an increase in the biomass (from 8 to 450 mg/l), in protein content (from 8 to 54 %) and in chlorophyll. At low N levels, the green algae contained a high percentage of total lipids (45 % of the biomass). More than 70 % of these were neutral lipids such as triacylglycerols (containing mainly 16:0 and 18:1 fatty acids) and trace amounts of hydrocarbons. At high N levels, the percentage of total lipids dropped to about 20 % of the dry weight. In the latter case the predominant lipids were polar lipids containing polyunsaturated C₁₆ and C₁₈ fatty acids. The blue-green algae, however, did not show any significant changes in their fatty acid and lipid compositions, when the nitrogen concentrations in the nutrient medium were varied. Thus the green but not the blue-green algae can be manipulated in mass cultures to yield a biomass with desired fatty acid and lipid compositions. The data may indicate a hitherto unrecognized distinction between prokaryotic and eukaryotic organisms.     

Insights into succession processes using temporally repeated habitat models: results from a long‐term study in a post‐mining landscape

Questions: The early phases of primary succession are governed by chance events and dispersal‐related processes in an environment that is largely free of competition. Thus, the predictability of vegetation patterns using environmental site factors can be expected to be low and spatial autocorrelation to be high. We asked whether the match between vegetation and environment becomes better in the course of succession, and whether vegetation types shift their realized niche with time. Location: Lignite mining region in Central Germany, the post‐mining landscape “Goitzsche” (Saxony‐Anhalt). Methods: Vegetation types were mapped in a 10‐m grid (total area 4.8 ha), starting in 1995, at 3‐year intervals until 2007. We used a temporal comparison of habitat models. We applied: GLS regression to partition the variation in coverage of vegetation types into environmental (soil pH) and spatial components; logistic regression to model the presence/absence of vegetation types along a soil acidity gradient; and autologistic regression allowing for soil acidity and neighbourhood effects. Results: For most vegetation types, the proportion of variation explained by space was high but declined during succession. The outcome of autologistic models suggests that soil acidity often plays a minor role compared to neighbourhood effects in the earlier phase of succession than 12 years later. For four vegetation types, the pH range in which the type was expected to be dominant clearly became smaller with time. These trends support the view that the role of processes related to chance and dispersal decrease with time, while those related to environmental filtering mediated by biotic interactions increase. Conclusions: We conclude that temporal comparisons of spatially explicit habitat models provide insights into changing biotic community processes and their effects on habitat specificity of species or their communities. Thus, this approach may be particularly important for analysis of ecological systems that are not in equilibrium with their environmental drivers.     

A comparison of breeding population estimators using nest and brood monitoring data

For many species, breeding population size is an important metric for assessing population status. A variety of simple methods are often used to estimate this metric for ground‐nesting birds that nest in open habitats (e.g., beaches, riverine sandbars). The error and bias associated with estimates derived using these methods vary in relation to differing monitoring intensities and detection rates. However, these errors and biases are often difficult to obtain, poorly understood, and largely unreported. A method was developed to estimate the number of breeding pairs using counts of nests and broods from monitoring data where multiple surveys were made throughout a single breeding season (breeding pair estimator; BPE). The BPE method was compared to two commonly used estimation methods using simulated data from an individual‐based model that allowed for the comparison of biases and accuracy. The BPE method underestimated the number of breeding pairs, but generally performed better than the other two commonly used methods when detection rates were low and monitoring frequency was high. As detection rates and time between surveys increased, the maximum nest and brood count method performs similar to the BPE. The BPE was compared to four commonly used methods to estimate breeding pairs for empirically derived data sets on the Platte River. Based on our simulated data, we expect our BPE to be closest to the true number of breeding pairs as compared to other methods. The methods tested resulted in substantially different estimates of the numbers of breeding pairs; however, coefficients from trend analyses were not statistically different. When data from multiple nest and brood surveys are available, the BPE appears to result in reasonably precise estimates of numbers of breeding pairs. Regardless of the estimation method, investigators are encouraged to acknowledge whether the method employed is likely to over‐ or underestimate breeding pairs. This study provides a means to recognize the potential biases in breeding pair estimates.     

Nest‐site selection by Interior Least Terns and Piping Plovers at managed,off‐channel sites along the Central Platte River in Nebraska,USA

Given the high productivity of Interior Least Terns (Sternula antillarum athalassos) and Piping Plovers (Charadrius melodus) on constructed off‐channel nesting sites along the central Platte River in Nebraska, USA, and the possibility of creating similar habitats at other locations in their breeding range, understanding how these species use off‐channel nesting habitats is important. We used data collected along the central Platte River in Nebraska, USA, over a 15‐year period (2001–2015), and a discrete‐choice modeling framework to assess the effects of physical site attributes and inter‐ and intraspecific associations on off‐channel nest‐site selection by Interior Least Terns and Piping Plovers. We found that Piping Plovers avoided nesting near each other, whereas colonial Interior Least Terns selected nest sites near those of conspecifics. In addition, the relative probability of use for both species was maximized when distance to the nearest predator perch was ≥ 150 m and elevation above the waterline was ≥ 3 m. Probability of use for nesting by Interior Least Terns increased as distance to water increased, whereas the probability of use by Piping Plovers was maximized when distance to water was ~50 m. Our results suggest that important features of constructed, off‐channel nesting sites for both species should include no potential predator perches within 150 m of nesting habitat and nesting areas at least 3 m above the waterline. Efficient site designs for Interior Least Terns would be circular, maximizing the area of nesting habitat away from the shoreline, whereas an effective site design for Piping Plovers would be more linear, maximizing the area of nesting habitat near the waterline. An efficient site design for both species would be lobate, incorporating centralized nesting habitat for Interior Least Terns and increased access to foraging areas for nesting and brood‐rearing Piping Plovers.     

CO2 gas exchange and transpiration of Welwitschia mirabilis Hook. fil. in the central Namib desert

Summary The diurnal course of CO₂ gas exchange, ¹⁴CO₂ incorporation, malate and citrate content, and traspiration of Welwitschia mirabilis were measured in one of its natural habitats, the Welwitschia-Vlakte in the central Namib desert (Namibia), in order to decide which CO₂ fixation pathway is used by this gymnosperm.The CO₂ gas exchange of Welwitschia is that of a C₃ plant under arid conditions. Younger leaf parts show a two-peaked pattern of photosynthetic CO₂ uptake whereas in older parts the morning peak is followed by net CO₂ release during the rest of the day. The maximum rates of net photosynthesis decrease from 3.4 mol m^-2 s^-1 in 1-year-old parts to 1 mol m^-2 s^-1 in 7-year-old parts. No net CO₂ uptake was detected during the night. The diurnal CO₂ balance indicates that the old leaf parts live at the expense of the younger ones. Irrigation of Welwitschia plants resulted in an increased CO₂ uptake throughout the light period with maximum rate of 4.1 mol m^-2 s^-1. ¹⁴CO₂ was only incorporated during the day.The water loss of Welwitschia by transpiration is considerable, reaching a peak value of 1.9 mmol m^-2 s^-1 around noon. Leaf conductance corresponds with the twopeaked pattern of CO₂ uptake.Although there is no sign of a crassulacean acid metabolism in Welwitschia the leaf contains rather high amounts of malate (up to 200 mol g^-1 dry matter) and citrate (up to 250 mol g^-1 dry matter), which depend on leaf age but do not show any significant day-night oscillation.In spite of all this the ¹³C values are in the range of-17.77 to-19.64. Possible reasons for such a high ¹³C content in a C₃ plant are discussed.Dedicated to Prof. H. Walter, the pioneer of ecophysiological studies in the Namib desert     

Movements of white-tailed deer in riparian habitat: Implications for infectious diseases

Movements of male white-tailed deer (Odocoileus virginianus) are of great concern with respect to spread of chronic wasting disease (CWD) across landscapes because most yearlings males disperse and adult males have higher prevalence of CWD than do females and younger deer. We radiocollared and monitored 85 male white-tailed deer in the middle Missouri River Valley of eastern Nebraska and western Iowa, USA from 2004 to 2008. Average size (±SE) of fixed-kernel annual home ranges (95%) and core areas (50%) for resident deer were 449 (±32) ha and 99 (±7) ha, respectively. Resident deer exhibited a high-degree of fidelity to their home ranges. Mean overlap between consecutive annual home ranges and core areas was 81% and 74%, respectively. Average dispersal distance was 17.7 ± 4.5 km (range = 3–121 km) for 22 radio-marked and 6 ear-tagged yearlings. Mean spring dispersal distance (25 km) was 150% greater than fall (10 km). Dispersal direction from Desoto National Wildlife Refuge (DNWR) was bimodal on a northwest to southeast axis that followed the Missouri River corridor. Of 22 yearlings that dispersed, 18 (82%) established adult home ranges within the river valley. Dispersal movements of yearling males represent the greatest risk for rapid spread of diseases from infected source populations. Disease management efforts in riparian habitats should target male fawns and yearling males for removal in areas within or immediately adjacent to river corridors. © 2011 The Wildlife Society.