Variation in elemental stoichiometry and RNA:DNA in four phyla of benthic organisms from coral reefs

The elemental composition of organisms has been linked to traits such as growth rates, through investment of phosphorus (P) in RNA (called the Growth Rate Hypothesis) and through ecological processes such as susceptibility to predation and herbivory. To test the predictions of the Growth Rate Hypothesis, we assessed the elemental composition and RNA of four phyla of common, co-occurring benthic coral reef organisms, corals, and green, brown and red macroalgae, whose patterns of dominance are predicted to be strongly influenced by differences in growth and herbivory and thus elemental stoichiometry. We assessed the importance of phylogeny and functional form, two important attributes for predicting the composition of macroalgal communities, on the variation in elemental composition. Over these widely divergent taxonomic groups of organisms, we found support for links between elemental composition and RNA in tissues. The RNA:DNA in corals was positively correlated with % nitrogen (N) and negatively correlated with carbon (C):N ratios of tissues while RNA:DNA and RNA concentrations in macroalgae were positively correlated with %N, N:P ratios and negatively correlated with C:N ratios. Corals had higher concentrations of P and lower C:P ratios than macroalgae. Among the macroalgal lineages, C:P was higher in the brown algae than in red and green algae. Overall, the variation in elemental composition of macroalgae was relatively low compared with the variation reported for terrestrial plants and similar to that in corals. Analysis of phylogenetic sources of variation (family and genus) in elemental composition and RNA found that genus accounted for a significant proportion of variation in both corals and macroalgae (15-47%), but the largest source of variation (50-97%) was unexplained by our statistical model and thus likely attributable to species and environmental factors. Although elemental composition of macroalgae did not vary in a way that was consistent with functional form models, genera with larger thalli had higher tissue N than smaller forms and more lineages with greater complexity of form had lower C:P ratios than less complex brown algal lineages. Our data indicate that the despite relatively low levels of variation in elemental composition compared with terrestrial organisms, elemental stoichiometry varied significantly among coral reef taxa and with the structure of organisms and thus may have potential for predicting variation in growth rates and patterns of consumption on coral reefs

EARLINET: A European Aerosol Research Lidar Network to establish an aerosol climatology

The European Aerosol Research Lidar Network (EARLINET) has been established in 2000 to derive a comprehensive and statistically relevant quantitative data base of the aerosol vertical distribution over Europe. For this purpose, regular lidar measurements have been performed at 22 locations in 13 European countries. Most of the measurements have been taken on a fixed schedule at preselected times and days to avoid a fair weather bias in the statistics. Additional measurements have been performed to investigate special topics like Saharan dust outbreaks, temporal cycles, the modification of aerosol on its way through Europe or long range transport of aerosol to Europe. All instruments have been quality controlled in extensive intercomparison experiments. The algorithms used to derive aerosol backscatter and extinction have been tested separately using synthetic lidar data. The EARLINET quality assurance is presented in detail in MPI report 337. This report gives the main results of the EARLINET project which have been achieved up to spring 2003. Most relevant topics are - data base on aerosol vertical profiles and backtrajectories - temporal cycles of the aerosol distribution - observation of special events, e.g. Saharan dust and forest fires - impact of the aerosol vertical distribution on satellite retrievals - aerosol modification during transport over Europe - influence of orography on aerosol vertical transport - stratospheric aerosol - differences between rural and urban aerosol - effect of aerosol on UV-B radiation - statistical analysis of the aerosol vertical profiles - lidar ratio statistical analysis - long range transport of aerosol to Europe - algorithms to derive aerosol microphysics from lidar dat