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We examined the response of diatoms to naturally experienced temperatures and tested these hypotheses: (1) diatoms follow the rule that organism size decreases with increasing temperature; (2) diatom growth rate follows a [Q.sub.10]-like response; (3) diatom carbon (C) and nitrogen (N) content per unit volume (V) decrease with increasing size, and changes in temperature affect this relationship; and (4) diatom C: V is the same as that of other phytoplankton. We also present, as predictive equations, relationships between (1) growth rate, temperature, and size; (2) C content and V; and (3) N content and V. Eight diatoms and two flagellates were acclimated for approximately five generations and grown for approximately five more generations at five temperatures (9-25 [degrees] C) on a 14:10 light: dark cycle at ~50 [micro]mol photons [m.sup.-2] [s.sub.-1]. Growth rate, cell V, and C and N content per cell were measured; relationships between these parameters and temperature were determined. For five diatoms and both flagellates, cell V decreased with increasing temperature; cells decrease by ~4% of their mean V per [degrees] C. Growth rate appeared to increase linearly with temperature in all cases. The literature suggests that a linear response is the rule, not the exception. Temperature did not significantly affect C or N per V of diatom species. When all diatoms were considered, both C and N per V decreased with increasing cell size; our data support the argument that diatoms differ from other protists in this respect, but the difference is less pronounced than stated in previous reports.

The application of hydrogen peroxide (H2O2) as a management tool to control Microcystis blooms has become increasingly popular due to its short lifetime and targeted action. H2O2 increases intracellular reactive oxygen species resulting in oxidative stress and subsequently cell death. H2O2 is naturally produced in freshwater bodies as a result of photocatalytic reactions between dissolved organic carbon and sunlight. Previously, some studies have suggested that this environmental source of H2O2 selectively targets for toxigenic cyanobacteria strains in the genus Microcystis. Also, past studies only focused on the morphological and biochemical changes of H2O2-induced cell death in Microcystis with little information available on the effects of different H2O2 concentrations on growth, esterase activity and membrane integrity. Therefore, this study investigated the effects of non-lethal (40–4000 nM) concentrations on percentage cell death; with a focus on sub-lethal (50 μM) and lethal (275 μM; 500 μM) doses of H2O2 on growth, cells showing esterase activity and membrane integrity. The non-lethal dose experiment was part of a preliminary study. Results showed a dose- and time-dependent relationship in all three Microcystis strains post H2O2 treatment. H2O2 resulted in a significant increase in intracellular reactive oxygen species, decreased chlorophyll a content, decreased growth rate and esterase activity. Interestingly, at sub-lethal (50 μM H2O2 treatment), percentage of dead cells in microcystin-producing strains was significantly higher (p < 0.05) than that in non-microcystin-producing strains at 72 h. These findings further cement our understanding of the influence of H2O2 on different strains of Microcystis and its impact on membrane integrity and metabolic physiology: important to future toxic bloom control programmes. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.forsciint.2008.03.014 Byline: Daniel Franklin (a), Paul O'Higgins (b), Charles E. Oxnard (a)(c), Ian Dadour (a) Keywords: Forensic anthropology; Mandible; Sex determination; Discriminant function analysis; Skeletal biology Abstract: South Africa currently has a high homicide rate. This results in a large number of unidentified bodies being recovered each year, many of which are referred to the forensic examiner. This situation has resulted in considerable growth of forensic anthropological research devoted to devising standards for specific application in South African medico-legal investigations. The standards suitable for Black South Africans now encompass a wide variety of skeletal elements (e.g. cranium, humerus, pelvis, femur, patella, talus, calcaneus), each with differing degrees of accuracy. Apart from a preliminary investigation of the Zulu local population, however, we note that there appears to be no established metric mandible discriminant function standards for sex determination in this population. The purpose of the present study is to undertake a comprehensive analysis of sexual dimorphism in the mandible of Black South Africans, incorporating individuals from a selection of the larger local population groupings; the primary aim is to produce a series of metrical standards for the determination of sex. The sample analyzed comprises 225 non-pathological mandibles of Black South African individuals drawn from the R.A. Dart Collection. Nine linear measurements, obtained from mathematically transformed three-dimensional landmark data, are analyzed using basic univariate statistics and discriminant function analyses. All of the measurements examined are found to be sexually dimorphic; the dimensions of the ramus and corpus lengths are most dimorphic. The sex classification accuracy of the discriminant functions ranged from 70.7 to 77.3% for the univariate method, 81.8% for the stepwise method, and 63.6 to 84% for the direct method. We conclude that the mandible is a very useful element for sex determination in this population. Author Affiliation: (a) Centre for Forensic Science, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia (b) Functional Morphology and Evolution Research Unit, The Hull York Medical School, Heslington, York Y010 5DD, United Kingdom (c) School of Anatomy and Human Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, Australia Article History: Received 17 November 2006; Accepted 19 March 2008

Summary: During viral infection and growth limitation of the picoeukaryote Ostreococcus tauri, we examined the relationship between membrane permeability, oxidative stress and chlorophyll allomers (oxidation products). Chlorophyll allomers were measured in batch‐cultures of O. tauri in parallel with maximum quantum efficiency of photosystem II photochemistry (Fv/Fm), carotenoids, and reactive oxygen species and membrane permeability using fluorescent probes (CM‐H2DCFDA and SYTOX‐Green). Viral infection led to mass cell lysis of the O. tauri cells within 48 h. The concentration of the allomer hydroxychlorophyll a peaked with a 16‐fold increase (relative to chlorophyll‐a) just after the major lysis event. In contrast, cell death due to growth limitation resulted in a twofold increase in allomer production, relative to chl‐a. Two allomers were detected solely in association with O. tauri debris after viral lysis, and unlike other allomers were not observed before viral lysis, or during cell death due to growth limitation. Conversely, the component chl‐aP276 was found in the highest concentrations relative to chl‐a, in exponentially growing O. tauri. The components described have potential as indicators of mode of phytoplankton mortality, and of population growth. [ABSTRACT FROM AUTHOR]