Michael Meyer

A statistical scheme for structural analysis in marine ecosystems

Abstract A statistical analysis scheme is presented for handling comprehensive data-sets in structural analyses in ecological investigations. The program bloc for the data analysis depends on the kind of data sampling; i.e. we consider data matrices which involve different stations or different times. The results are mainly either plotted as graphical representations, or printed in symbol-matrices, to allow an extensive and rapid survey of the findings. The scheme is provided as a minimal procedure, and is suitable for most purposes in structural analysis for marine biology. Graph theoretical methods are demonstrated for the structural analysis of data from ecosystem research, and further applications are discussed.

The influence of microclimatic conditions on potential photosynthesis ofUsnea sphacelata: A model

At a boulder on a hill near Casey Station, Wilkes Land, sensors for light, temperature and humidity were installed facing the four cardinal directions. The measurements lasted for about two months of the summer season 1985/86. The data recording was carried out at intervals of 6 minutes for all probes by automatic recording instruments.Data analysis was carried out with special regard to the biological effects of the parameters analyzed. These data of the microclimatic features taken from its original place of growth were used to a regression model of potential photosynthetic activity ofUsnea sphacelata, which is a characteristic species of this area.Although the individual time courses of the above mentioned parameters show long periods of favourable conditions for possible growth and metabolic processes, the combined analysis of these variables considering threshold values for metabolism shortens these time spans drastically. Thus, cross relationships within the physical descriptors and their effects on the actual values of photosynthesis as well as respiration become evident. They are illustrated by the results of models on photosynthesis and respiration ofU. sphacelata regarding the different cardinal directions.

Structure, methyl internal rotation, centrifugal distortion, and dipole moment of 2-chloropropane

Abstract The microwave spectra of six isotopic species of 2-chloropropane have been investigated by microwave Fourier transform spectoscopy. The quartic and some sextic centrifugal distortion constants of the 35 Cl and 37 Cl species are given. The structure has been derived by various methods. The dipole moment was found to be 2.141 D. From excited torsional states the parameters V 3 and V 12 ′ of the torsional potential function were obtained.

Structuring of ecological data sets by methods of correlation and cluster analysis

The analysis of ecological field data of extensive studies in marine environments needs special adapted strategies for their analyses. Those data sets can be classified into two major categories: (a) data from stations, i.e. quasi-synoptic approaches for the description of different biotopes; and (b) data from seasonal investigations, i.e. surveys of time dependent changes in an environment. The unbiased search for the various interrelationships between parameters becomes a useful tool in describing ecological patterns of complex systems. The evaluation of main items by cluster analysis and other ordering procedures defines structural and functional units or sets local and/or seasonal boundaries. n nIt is proposed to use non-parametric statistics to overcome the inhomogeneity of the parameters and their interactions which may be assumed to be nonlinear or governed by many feed-back mechanisms. Subsequent analysis of those correlation matrices can be conducted by different cluster algorithms and shows in a holistic view on the original data set significant patterns of the structure of the system and leads to the description of interacting subsystems at different levels. Such unbiased data analysis has been adopted to various ecological data sets comprising physical, chemical and biological parameters. The analysis of data from seasonal and synoptic investigations shows the suitability of the strategy proposed: (1) An annual cycle of data concerning the microbial environment in the Kiel Fjord (Baltic Sea) revealed distinct seasonal patterns which can be attributed to the general planktonic environment. It is possible to define subunits of the total annual cycle, which may be regarded as ‘ecological situations’, their successions and boundaries based on thresholds of environmental parameters. These thresholds are regarded as ‘switches’ of the ecosystems structure or as marginal conditions of the acting subsystem. (2) The analysis of data sets from different stations showed the separation of a ‘unique’ environment into units of different structures, caused by influences of the current system or other dominating environmental conditions. These results point to a strong spatial heterogeneity of marine systems, indicate their response on different nutritional sources and reflect the change in the interrelationships. n nThe analysis of the interacting or residual (unclustered) parameters of the subunits either from seasonal of spatial data sets shows the different structures of these systems as for instance the changing ratios of nutrients, populations and environmental characters. n nThe lack of causal relationships between individual parameters of complex systems and the stochastic behaviour of their course leads to the assumption that the annual cycle of the planktonic environment is more governed by catastrophes, i.e. sudden and unpredictable events, than by continuous processes. The different states of the system as established by this method show the fluctuation of parameters according to their marginal conditions and their ranges of variability within the given situation. The effects of sudden changes in environmental conditions were tested in bioassays using containers of approximately 30 1 of waters. The results reflect the response of the microbial population and their activity on various impacts. Thus it becomes more evident to focus on features describing more overall patterns of an ecosystem in terms of stability or instability and boundary conditions than on direct interactions between individual parameters based on the concept of cause and effect.

Semiempirical and ab initio study of closed and open shell derivatives of 10-methylisoalloxazine: a model of flavin redox states

Abstract The structures of a series of neutral and charged derivatives of 10-methylisoalloxazine in three different redox states have been optimized with the semiempirical PM3 method and with ab initio methods at Hartree-Fock level. The isoalloxazine ring is planar in the oxidized and one electron reduced state, except for the cations with a proton at N1, and it is folded in the two electron reduced state. Single point MP2 and self consistent reaction field calculations have been used for the analysis of the energies in the gas phase and in a polar medium. The energy difference between the cations with a proton at N1 and O2 is small for each redox state and depends on the solvent. Protonation and deprotonation energies have been calculated.

Density functional study of isoalloxazine and C4a-hydroperoxidihydroisoalloxazine

Abstract The structures of isoalloxazine and C4a-hydroperoxidihydroisoalloxazine have been computed at B3LYP/6-31G ∗ level. Solvent effects on relative energies of tautomers and protonation equilibria have been investigated using the SCI-PCM model. The results have been discussed in relation to biochemical properties of flavin coenzymes.

Internal rotation of molecules with two equivalent tops: The microwave spectrum of 2-fluoropropane

Abstract The microwave spectrum of 2-fluoropropane in the three lowest torsional states has been investigated to determine parameters V 3 and V ′ 12 of the torsional potential function and the angles between the principal axes of inertia and the internal rotation axes. This required the development of a computer program taking into account the top-top coupling. The energy levels and linestrength are calculated using a stepwise procedure of diagonalization of appropriately truncated matrices.

The Sandy Beach Area of Kiel Fjord and Kiel Bight (Western Baltic Sea) — A Structural Analysis of a Shallow Water Ecosystem

The ecosystem of sandy beaches shows a high complexity of interrelationships between physical, chemical and biological properties and may be regarded as a special biotope at the boundary between the pelagic environment, the sediments and adjacent terrestrial zones. A review on such interactions with special regard to biological features has been given recently by McLachlan et at. (1981), lending support to the description of these niches as autonomous systems.

Computational study of novel catechol-type siderophore analogs

Abstract A series of catechol-type siderophores has been proposed using the ligand design program LUDI. Semiempirical PM3 calculations have been carried out for gallium siderophore complexes including enterobactin, TRENCAM and the myxochelin series with an alkyl chain backbone. The tris(catechol) gallium group of both diasteromeric [Ga(ent)]3− complexes can be overlaid closely with [Ga(cat)3]3−. This indicates an energetically favourable conformation without any strain. The energy difference between both [Ga(ent)]3− diastereomers having a Δ- and Λ-configuration is very small. A similar optimal geometry of the chelatligand is only possible for special chain lengths of the alkyl backbone. Short chains connecting the catechol groups lead to serious deformations of the complex structure and therefore it is impossible that metal ions are ligated by the six catechol oxygens of a single siderophore with a short alkyl chain backbone.

Methyl internal rotation, dipole moment, and nuclear quadrupole coupling of 2-bromopropane

Abstract The microwave spectrum of 2-bromopropane has been investigated to determine nuclear quadrupole and spin-rotation coupling constants of bromine for the 79 Br and 81 Br species by microwave Fourier transform spectroscopy. The dipole moment was found to be 2.194 D. From excited torsional states the parameters V 3 and V ′ 12 of the torsional potential function were obtained.