Description: Optic technologies and methods/procedures are established across all areas and scales in limnic and marine research in Germany and develop further continuously. The working group “Aquatic Optic Technologies” (AOT) constitutes a common platform for knowledge transfer among scientists and users, provides a synergistic environment for the national developer community and will enhance the international visibility of the German activities in this field. This document summarizes the AOT-procedures and -techniques applied by national research institutions. We expect to initiate a trend towards harmonization across institutes. This will facilitate the establishment of open standards, provide better access to documentation, and render technical assistance for systems integration. The document consists of the parts: Platforms and carrier systems outlines the main application areas and the used technologies. Focus parameters specifies the parameters measured by means of optical methods/techniques and indicates to which extent these parameters have a socio-political dimension. Methods presents the individual optical sensors and their underlying physical methods. Similarities denominates the common space of AOT-techniques and applications. National developments lists projects and developer groups in Germany designing optical high-technologies for limnic and marine scientific purposes.

Description: I developed a new model for estimating annual production-to-biomass ratio P/B and production P of macrobenthic populations in marine and freshwater habitats. Self-learning artificial neural networks (ANN) were used to model the relationships between P/B and twenty easy-to-measure abiotic and biotic parameters in 1252 data sets of population production. Based on log-transformed data, the final predictive model estimates log(P/B) with reasonable accuracy and precision (r2 = 0.801; residual mean square RMS = 0.083). Body mass and water temperature contributed most to the explanatory power of the model. However, as with all least squares models using nonlinearly transformed data, back-transformation to natural scale introduces a bias in the model predictions, i.e., an underestimation of P/B (and P). When estimating production of assemblages of populations by adding up population estimates, accuracy decreases but precision increases with the number of populations in the assemblage.

Description: Optic technologies and methods/procedures are established across all areas and scales in limnic and marine research in Germany and develop further continuously. The working group “Aquatic Optic Technologies” (AOT) constitutes a common platform for knowledge transfer among scientists and users, provides a synergistic environment for the national developer community and will enhance the international visibility of the German activities in this field. This document summarizes the AOT-procedures and -techniques applied by national research institutions. We expect to initiate a trend towards harmonization across institutes. This will facilitate the establishment of open standards, provide better access to documentation, and render technical assistance for systems integration. The document consists of the parts: Platforms and carrier systems outlines the main application areas and the used technologies. Focus parameters specifies the parameters measured by means of optical methods/techniques and indicates to which extent these parameters have a socio-political dimension. Methods presents the individual optical sensors and their underlying physical methods. Similarities denominates the common space of AOT-techniques and applications. National developments lists projects and developer groups in Germany designing optical hightechnologies for limnic and marine scientific purposes.

Description: On the high Antarctic shelf, as well as in other marine coastal regions, fish play a central role in the food web as they provide a major trophic link between small sized low trophic level organisms and large vertebrate predators. Marine living communities in the Antarctic are increasingly threatened by alterations of the abiotic and biotic environment due to climate change. The impact of environmental changes on fish not only operates directly, but also indirectly through the food chain. The vulnerability of a particular fish species to such indirect effects and its risk to get lost due to alterations in food web structure are mainly determined by (i) the species plasticity to respond to resource fluctuations, and (ii) predator induced mortality. Species vulnerability decreases with increasing prey diversity (generalist vs. specialist consumers) and decreasing predator diversity. Whether or to which degree fish species loss indirectly affects overall food web structure and ecosystem functioning, depend on the communities or populations capacity for functional compensability (species redundancy), i.e. the degree to which coexisting species can compensate for one another within the food web. Based on data on fish species composition and a large dataset on who eats whom we evaluate the functional role of fish species in the food web of the high Antarctic Weddell Sea shelf, the vulnerability of particular species to food web alterations, and the potential for functional compensability in case of species loss. Fish fauna on the shelf is composed of 50 different fish species, with one plankton feeding species, Pleuragramma antarcticum, distinctly dominating the fish community. Most other fish species inhabiting the Weddell Sea shelf are feeding on benthos or a mixture of benthos and plankton. Vulnerability of species is positively related to the amount of planktonic prey items in the diet, as plankton consumers are mostly specialized on few prey items and are additionally preyed upon by a multitude of higher trophic level predators in the water column. Benthos feeders, in contrast, are generalist consumers with a low number of predators. Vulnerability is consequently low in these species and functional redundancy buffers the effect of eventual species loss. Plankton consumers, mainly represented by P. antarcticum, are highly sensitive to alterations in trophic structure. Due to the lack of functional redundancy within this trophic group, extinction of P. antarcticum might have severe consequences for overall food web structure and ecosystem functioning. On the high Antarctic shelf, P. antarcticum represents a wasp-waist, and thus plays a similar role as sardines and anchovies in tropical upwelling systems.