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Filter-feeding silver carp (Hypophthalmichthys molitrix) has been extensively used to control algae blooms in Chinese lakes. However, the benefit of stocking silver carp to restore eutrophic lakes remains controversial and the reasons for the different responses observed are unclear.In this study, we conducted an outdoor experiment to assess the impact of the biomass level of four silver carp (c. 0, 25, 50, and 100 g/m(3)) on phytoplankton through direct grazing and fish-mediated nutrient recycling, respectively. We used a nested design with nutrient-permeable chambers with or without fish placed inside ponds. In this way, the phytoplankton incubated outside the chambers was affected by both consumer grazing and nutrient recycling, whereas the phytoplankton inside the fish-free chambers was only affected by consumer-mediated nutrient recycling.Outside the chambers, the concentrations of total nitrogen, dissolved total nitrogen, and total phosphorus did not differ significantly among the treatments, whereas the dissolved total phosphorus level was significantly higher in the fishless treatment. The concentration of chlorophyll a (Chl a), phytoplankton biomass and the ratio of nanophytoplankton Chl a to total phytoplankton Chl a in the fish-present treatments were significantly higher than in the fishless treatment and the phytoplankton was dominated by small-sized species. While the zooplankton biomass and zooplankton:phytoplankton biomass ratio were significantly lower in the fish-present treatments, indicating a strong fish predation on zooplankton. As for the water inside the chambers, there was no significant difference among the four treatments for any of the measured variables except total phosphorus.Our results suggest that silver carp indirectly stimulated phytoplankton growth by reducing the zooplankton grazing rather than through nutrient recycling, and that fish grazing on phytoplankton could not compensate for the loss of grazing by zooplankton, leading to higher phytoplankton biomass when silver carp was present. The benefit of using filter-feeding fish as a biomanipulation tool to create clear water is therefore questionable unless control of nanophytoplankton can be achieved.

RATIONALE Studies on diet or trophic interactions of organisms based on stable isotopes require accurate estimates of how quickly stable isotope ratios change in the investigated tissues. However, rates of isotope turnover in fish tissues, especially in omnivorous species, are poorly understood. METHODS We conducted a diet-shift study using juvenile tilapia to (i) empirically estimate the isotopic turnover rates of nitrogen in the dorsal muscle, liver, fin and backbone; (ii) model the relative contributions of metabolism and growth to the total isotopic turnover in each tissue; and (iii) develop a non-lethal approach for estimating body nitrogen stable isotope ratios for threatened or endangered species. Isotopic analyses were performed using a Flash EA CN elemental analyser coupled to a ThermoFinnigan Delta Plus mass spectrometer. RESULTS Nitrogen isotopic turnover rates were consistently ranked in the order backbone > liver > muscle > fin due to the relatively lower metabolic rates of muscle and fin tissue. Backbone tissue turned over significantly faster than other tissues, suggesting the potential for a multiple-tissue stable isotope approach to the study of movement and trophic position over different time scales for omnivorous fish. However, fin tissue had the longest half-life, at 57.81 days, indicating that this tissue is more useful than muscle as a long-term dietary indicator. CONCLUSIONS The change in nitrogen isotope ratios in dorsal muscle was mainly regulated by somatic growth, but metabolic activity markedly stimulated the turnover rate of backbone. This study is one of a few to demonstrate significant variation in the δ(15) N turnover rates among multiple tissues of a single organism, especially for omnivorous fish. Our results, to some extent, also indirectly contribute to the conservation of threatened or endangered species. Copyright © 2016 John Wiley & Sons, Ltd.

This paper proposes four companding transforms to reduce the peak-to-average power ratio in orthogonal frequency division multiplexing systems. The four companding transforms are obtained by transforming signal statistics into four trigonal distributions. Computer simulations show that the proposed schemes can effectively improve the PAPR performance and bit error rate performance of OFDM systems. Copyright © 2010 John Wiley & Sons, Ltd.

Phase contrast techniques in the transmission electron microscope are used to measure electrostatic potentials at 24° [001] tilt boundaries in nominally undoped and Nb-doped SrTiO3 bicrystals. All of the boundaries are found to have lower scattering potentials than the surrounding bulk crystal. Origins for the measured changes in potential are investigated through the application of high-resolution transmission electron microscopy, diffuse dark-field imaging, energy dispersive X-ray spectroscopy, and parallel electron energy loss spectroscopy. Significantly, we show that space charge is not the dominant contribution to the potential because the magnitudes of the potentials seen cannot be explained on the basis of ionic space charge theory alone.