Temperature, organic matter and the sustainability of aquatic systems

Changes in sustainability of aquatic ecosystems are likely to be brought about by the global warming that has been widely predicted. In this article, the effects of water temperature on water-bodies (lakes, oceans and rivers) are reviewed followed by the effects of temperature on aquatic organisms. Almost all aquatic organisms require exogenous heat before they can metabolise efficiently. An organism that is adapted to warm temperatures will have a higher rate of metabolism of food organisms and this increases feeding rate. In addition, an increase in temperature raises the metabolism of food organisms, so food quality can be altered. Where populations have a different tolerance to temperature the result is habitat partitioning. One effect of prolonged high temperature is that it causes water to evaporate readily. In the marine littoral this is not an important problem as tides will replenish water in pools. Small rain pools are found in many tropical countries during the rainy season and these become incompletely dried at intervals. The biota of such pools must have resistant stages within the life cycle that enable them to cope with periods of drying. The most important potential effects of global warming include (i) the alteration of existing coastlines, (ii) the development of more deserts on some land masses, (iii) higher productivity producing higher crop production but a greater threat of algal blooms and (iv) the processing of organic matter at surface microlayers

Studies on blackflies (Diptera: Simuliidae) breeding in bog streams in upper Teesdale

This study, on the immature stages of the Simuliidae, was undertaken in streams draining bogs in Upper Teesdale. There were four parts to the investigation: Firstly, a qualitative survey of fourteen sites showed eleven of the thirty-five British species of Simuliids to be present. Secondly, quantitative programmes showed streams to have three types of population structure: those with larvae present mainly in winter; mainly in summer; and throughout the year. Most streams were in the latter two categories, larval numbers being lower in winter at the higher altitudes. In summer 1972, absolute population estimates were obtained from two streams by removal trapping. More larvae occurred in the lower sections of the streams and, in the streams where the winter populations were low, larval numbers were larger early in summer; this was not true of the lower altitude stream. Thirdly, cumulative frequency x size-measurement plots were made on probability paper from which the modal size-classes corresponding to the larval instars of each species could be determined. All species had seven larval instars and percentage frequency distributions for each sampling date were constructed. The detailed population biology could then be determined. Larval life was much shorter in summer at 30-40 days than in winter. Two generations were distinguished, that in winter commonly having two cohorts and that in summer often as many as four

Pathways for the uptake of dissolved organic matter (DOM) by aquatic animals

In this article, pathways from freshwater and marine environments are described. DOM is defined operationally as all the organic compounds which pass through a filter of pore size 0.45 microm., those retained on the surface of the filter being particulate organic matter (POM). DOM can be taken up directly by animals by transfer across the body wall, but more commonly DOM is obtained from ingested food. Once ingested POM from food particles are broken down in the gut, small molecules of DOM are released for transfer across the gut wall. Some ingested particles are attacked by micro-organisms living in the gut, thereby making the DOM available to the host animal. The importance of the microbial loop is discussed, as well as aggregation processes between the fractions of DOM which are more obviously particulate in nature. (DBO

Design of a Base-Board for arrays of closely-packed Multi-Anode Photo-Multipliers

We describe the design of a Base-Board to house Multi-Anode Photo-Multipliers for use in large-area arrays of light sensors. The goals, the design, the results of tests on the prototypes and future developments are presented.Comment: 16 pages, 5 figures, submitted to Nucl. Instrum. and Meth.

Pathways for the uptake of dissolved organic matter (DOM) by aquatic animals

Life on Earth began after biochemical changes in, and the aggregation of,some of the dissolved organic materials (DOM) in the earliest seas. Withtime, the aggregations of molecules developed an integrity, the ability tocopy themselves, and thus life appeared

Temperature, organic matter and the sustainability of aquatic systems

Temperature has many effects on aquatic systems and this essay will,inevitably, make a broad sweep rather than take an "in depth" approach.The focus is on aquatic systems (i.e. all those where water is the medium)because many of the direct, and indirect, effects of temperature aresimilar both in marine and fresh waters. The article thus provides anotheropportunity to combine the two branches of aquatic science. Primaryliterature sources are deliberately omitted. Readers interested in the topicscovered will find full bibliographies in the books cited

Quantitative system drift compensates for altered maternal inputs to the gap gene network of the scuttle fly Megaselia abdita.

Published onlineJournal ArticleThis is the final version of the article. Available from eLife Sciences Publications via the DOI in this record.The segmentation gene network in insects can produce equivalent phenotypic outputs despite differences in upstream regulatory inputs between species. We investigate the mechanistic basis of this phenomenon through a systems-level analysis of the gap gene network in the scuttle fly Megaselia abdita (Phoridae). It combines quantification of gene expression at high spatio-temporal resolution with systematic knock-downs by RNA interference (RNAi). Initiation and dynamics of gap gene expression differ markedly between M. abdita and Drosophila melanogaster, while the output of the system converges to equivalent patterns at the end of the blastoderm stage. Although the qualitative structure of the gap gene network is conserved, there are differences in the strength of regulatory interactions between species. We term such network rewiring 'quantitative system drift'. It provides a mechanistic explanation for the developmental hourglass model in the dipteran lineage. Quantitative system drift is likely to be a widespread mechanism for developmental evolution.Ministerio de Economía y Competitividad MEC/EMBL Agreement/ BFU2009-10184/ BFU2012-33775/ SEV-2012-0208 Agència de Gestió d'Ajuts Universitaris I de Recerca SGR Grant 406 European Commission FP7-KBBE-2011-5/289434 National Science Foundation IOS-0719445/IOS-112121