Nitrogen uptake characteristics of Chordaria flagelliformis (Phaeophyta) in batch mode and continuous mode experiments

The uptake of NH ₄ ⁺ and urea by Chordaria flagelliformis was measured in a perturbed system (batch mode) and in an apparent steady-state system (continuous mode). The maximum uptake rates (V_max) measured in short-term depletion experiments greatly exceeded those determined under a steady nutrient supply. C. flagelliformis briefly exposed to high nutrient concentrations has an impressive capacity for rapid uptake (high V_max)_which is uncoupled from growth. In contrast, under continous, homogenous low N concentrations the alga appears well equipped (low half-saturation constant, K_m) to take up the available N. The results show that previous work based on batch mode uptake experiments probably overestimated the N requirements for the growth of many seaweeds.     

Seasonal growth of Laminaria solidungula in the Canadian High Arctic in relation to irradiance and dissolved nutrient concentrations

Pontomyia is a genus of tiny flightless marine midges, with 4 described species, found on tropical or subtropical sea shores of the western Pacific Ocean. They are rarely noticed because of their small size (about 1.5 mm) and ephemeral adult life (1 to 3 h). They usually occur in association with seagrasses and seaweeds on which the larvae feed. The oar-like wings of adult males propel them over the water surface, but do not enable them to fly. Adult females are not only wingless but virtually legless. Emergence of the adults in the field may occur either during the day or at night. In a laboratory aquarium population of P. cottoni Womersley, maintained for about 18 months in a 12 h light-12 h dark cycle, males began to emerge at the end of the light period, whereas females emerged only after the onset of darkness. Field observations suggest that emergence times are probably influenced also by tides.     

How an introduced seaweed can affect epibiota diversity in different coastal systems

Invasions by non-indigenous species have the potential to alter the biodiversity of recipient systems. The magnitude of this effect often depends on the nature of the invaded communities and the ecology of the invader. We investigated the impacts of the Japanese seaweed Sargassum muticum (Phaeophyceae, Fucales) on biodiversity in a rocky and sedimentary environment on two islands in the North Sea. In each case, we compared the epibiota of non-indigenous S. muticum with epibiota communities on taxonomically related and structurally similar native seaweed hosts. Total and average species richness on S. muticum were similar on the rocky shore (60 species and 22±6 species, respectively) and the sandy shore (64 species and 20±3 species, respectively). However, community structure and species composition differed significantly between the environments. On the rocky shore, another native fucoid seaweed, Halidrys siliquosa, supported an epibiota community very similar to that of the invader. On the sandy shore, the only other abundant native habitat-providing algal species was Fucus vesiculosus. This species supported a different and less diverse assemblage of associated taxa. We conclude that S. muticum enhances epibiota diversity in the sedimentary environment, probably by increasing the substratum availability and habitat heterogeneity. In contrast, it has negligible impacts on epibiota diversity in the rocky shore environment, where it does not represent a fundamentally new habitat component. We conclude that even within the same region, the consequences of non-indigenous species on biodiversity cannot be generalised but depend on the composition and structural complexity of the species in the recipient community. This paper is dedicated to Udo Schilling, Chief Diving Officer, Alfred Wegener Institute who trained all of the authors in the waters off Helgoland to be scientific divers. The work reported here and in previous publications has been made possible through Udo’s training and support. We remain grateful for his enthusiasm, effort and patience.     

Towards an ecological solution to the folivore paradox: patch depletion as an indicator of within-group scramble competition in red colobus monkeys (Piliocolobus tephrosceles)

A number of socioecological models assume that within-group food competition is either weak or absent among folivorous primates. This assumption is made because their food resources are presumed to be superabundant and evenly dispersed. However, recent evidence increasingly suggests that folivore group size is food-limited, that the primates prefer patchily distributed high-quality foods, and display some of the expected responses to within-group scramble competition. To investigate this apparent contradiction between theoretical models and recent empirical data, we examined the foraging behaviour of red colobus monkeys (Piliocolobus tephrosceles) in Kibale National Park, Uganda. We found that red colobus monkeys foraged in a manner that suggests they deplete patches of preferred foods: intake rate slowed significantly during patch occupancy while movement rate, an index of foraging effort, increased. Furthermore, patch occupancy was related to the size of the feeding group and the size of the patch. These results suggest that within-group scramble competition occurs, may limit folivore group size, and should be considered in models of folivore behavioural ecology.     

Effects of protected areas on survival of threatened gibbons in China

Establishing protected areas (PAs) is an essential strategy to reduce biodiversity loss. However, many PAs do not provide adequate protection due to poor funding, inadequate staffing and equipment, and ineffective management. As part of China's recent economic growth, the Chinese government has significantly increased investment in nature reserves over the past 20 years, providing a unique opportunity to evaluate whether PAs can protect threatened species effectively. We compiled data from published literature on populations of gibbons (Hylobatidae), a threatened taxon with cultural significance, that occurred in Chinese reserves after 1980. We evaluated the ability of these PAs to maintain gibbon habitat and populations by comparing forest cover and human disturbance between reserves and their surrounding areas and modeling the impact of reserve characteristics on gibbon population trends. We also assessed the perspective of reserve staff concerning PA management effectiveness through an online survey. Reserves effectively protected gibbon habitat by reducing forest loss and human disturbance; however, half the reserves lost their gibbon populations since being established. Gibbons were more likely to survive in reserves established more recently, at higher elevation, with less forest loss and lower human impact, and that have been relatively well studied. A larger initial population size in the 1980s was positively associated with gibbon persistence. Although staff of all reserves reported increased investment and improved management over the past 20–30 years, no relationship was found between management effectiveness and gibbon population trends. We suggest early and emphatic intervention is critical to stop population decline and prevent extinction.     

Effects of H2O2 on growth,metabolic activity and membrane integrity in three strains of Microcystis aeruginosa

Environmental Science and Pollution Research - The application of hydrogen peroxide (H2O2) as a management tool to control Microcystis blooms has become increasingly popular due to its short...     

Fenvalerate concentrations in a mineral and an organic soil receiving multiple applications during the growing season

Abstract

Fenvalerate EC at 140 g AI/ha was applied 7 times at 2 wk intervals to duplicate plots of Plainfield sand and an organic soil contained in 2.2 x 0.9 m field microplots with and without an onion crop present in 1980 and 1981 respectively. Soil samples were taken immediately before and after each application and at 2, 4, and 6 wk after the last application in 1980. Additional samples were taken at 22 and 34 wk for the 1981 treatment. Concentrations of fenvalerate were determined by glc. In the crop‐free mineral soil, fenvalerate levels declined from. 0.07–0.11 ppm immediately after spraying to 0.01–0.03 ppm after 2 wk; in the organic soil the rate of addition of fenvalerate exceeded the rate of disappearance and the concentration in the soil gradually increased over the 14 wk treatment period to the 0.9–1.0 ppm range. This concentration decreased slowly over the next 10 wk to 0.7–0.8 ppm and was still 0.5–0.7 ppm the following spring. Results were similar for cropped soils. Concentrations in the top third of the 15 cm cores were 6x and 15x those in the middle third for sand and organic soil, respectively. Concentrations, in the onions at harvest were <0.01 ppm.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.     

The persistence of insecticidal chemicals in soils treated with granular formulations of aldicarb and their uptake by potato plants

Abstract

Potatoes were grown in Plainfield sand and muck treated, in furrow, with aldicarb (Temik 15G, 3.36 kg Al/ha). .Soils were contained in 2 m^z field plots and had not been treated previously with pesticides. Soil, seed pieces, foliage and tubers were analyzed for the insecticide and its sulfoxide and sulfone metabolites during the 12 wk following planting. The disappearance of aldicarb from the soil was accompanied by partial conversion to the sulfoxide and sulfone. After increasing rapidly during the first 2 wk, the aldicarb concentration in the seed piece declined and a similar concentration of aldicarb sulfoxide accumulated which subsequently slowly disappeared. Aldicarb sulfoxide was the major insecticidal material in the new foliage. High initial concentrations, observed at 3–4 wk, declined by about 90% after 6 wk. Aldicarb sulfoxide residues of 2–4 ppm in the first new tubers at 6 wk declined by 90% by 12 wk. Potatoes were also grown under greenhouse conditions in Plainfield sand treated with Temik 10G at rates equivalent to 1.68, 3.36 and 6.72 kg Al/ha. Maximum aldicarb sulfoxide concentrations in soil, seed piece and foliage increased with application rate. The sulfoxide was much more persistent in the soil and foliage than in the field experiment indicating the importance of environmental factors to its behaviour in both soil and potato plants.