Oxygen microoptodes: a new tool for oxygen measurements in aquatic animal ecology

We describe two applications of a recently introduced system for very precise, continuous measurement of water oxygen saturation. Oxygen microoptodes (based on the dynamic fluorescence quenching principle) with a tip diameter of ~50 µm, an eight-channel optode array, an intermittent flow system, and online data registration were used to perform two types of experiments. The metabolic activity of Antarctic invertebrates (sponges and scallops) was estimated in respiration experiments, and, secondly, oxygen saturation inside living sponge tissue was determined in different flow regimes. Even in long-term experiments (several days) no drift was detectable in between calibrations. Data obtained were in excellent correspondence with control measurements performed with a modified Winkler method. Antarctic invertebrates in our study showed low oxygen consumption rates, ranging from 0.03-0.19 cm³ O₂ h^-1 ind.^-1. Oxygen saturation inside living sponge specimens was affected by flow regime and culturing conditions of sponges. Our results suggest that oxygen optodes are a reliable tool for oxygen measurements beyond the methodological limits of traditional methods.     

On the concept of sustainability – assessing the sustainability of large public infrastructure investment projects

Assessing the sustainability of large public investment projects within the general framework of three-pillar thinking is a complex affair. Such ventures involve multiple actors – e.g. planners from various disciplines such as engineers, economists and social scientists, in addition to politicians, users and other people affected – each carrying with them particular agendas and priorities, and corresponding understandings of the concept of sustainability. In this paper, we propose to frame the concept of sustainability assessment within the context of investment projects, in order to enable communication between the multiple actors, to assess different impacts of an investment project against one another in a meaningful way and, ultimately, to enhance the commensurability of investment project alternatives. Our main idea is that there exist different levels according to which the assessment of sustainability ought to refer – operational, tactical and strategic – and that properly addressing these levels can permit the different actors to comprehend one another, and thereby allow for more clarity and positive action.