Strength and uncertainty of phytoplankton metrics for assessing eutrophication impacts in lakes

Phytoplankton constitutes a diverse array of short-lived organisms which derive their nutrients from the water column of lakes. These features make this community the most direct and earliest indicator of the impacts of changing nutrient conditions on lake ecosystems. It also makes them particularly suitable for measuring the success of restoration measures following reductions in nutrient loads. This paper integrates a large volume of work on a number of measures, or metrics, developed for using phytoplankton to assess the ecological status of European lakes, as required for the Water Framework Directive. It assesses the indicator strength of these metrics, specifically in relation to representing the impacts of eutrophication. It also examines how these measures vary naturally at different locations within a lake, as well as between lakes, and how much variability is associated with different replicate samples, different months within a year and between years. On the basis of this analysis, three of the strongest metrics (chlorophyll-a, phytoplankton trophic index (PTI), and cyanobacterial biovolume) are recommended for use as robust measures for assessing the ecological quality of lakes in relation to nutrient-enrichment pressures and a minimum recommended sampling frequency is provided for these three metrics.     

Peroxisome proliferation in Norway spruce induced by ozone

Summary Catalase (EC 1.11.1.6) activity (both total and specific activity) of particulate fractions of needles of Norway spruce [Picea abies (L.) Karst.] was elevated approximately 2-fold following exposure of trees to 60–70 g/m³ of ozone during the growing season compared to trees receiving charcoal filtered air (about 15 g/m³ ozone). Measurements were from homogenates fractionated into particulate and soluble (supernatent) activities. In contrast, the catalase activity of the supernatant was unchanged in response to ozone treatment. Catalase activity declined as the needles aged comparing current, 1-, and 2-year needles but the ozone-induced increment remained constant. Electron microscope cytochemistry using peroxidatic coupling with 3,3-diaminobenzidine carried out in parallel, revealed catalase-containing peroxisomes both in situ and in the particulate fractions analyzed for catalase activity. The tissue volume occupied by peroxisomes in response to needle age and ozone appeared to vary approximately in proportion to the measured catalase activity. Overall cytochemical reactivity for catalase declined with needle age, but, for all years, was greater in needles of trees receiving air supplemented with ozone compared to those of trees receiving charcoal filtered air.Abbreviations DAB 3,3-diaminobenzidine tetrahydrochloride     

Joint disorder; a contributory cause to reproductive failure in beef bulls?

The lame sire, unsound for breeding, can cause substantial economic loss due to reduced pregnancies in the beef-producing herd.