Energy demand of larval and juvenile Cape horse mackerels, Trachurus capensis, and indications of hypoxia tolerance as benefit in a changing environment

Trachurus capensis is an important fisheries resource in the degraded Namibian upwelling ecosystem. Food supply and shoaling of hypoxic zones are hypothesised to influence the species’ recruitment success. This paper is the first to quantify energy requirements and hypoxia tolerance of larval and juvenile stages of a Trachurus species. We measured normoxic respiration rates of T. capensis with a size range from 0.001 to 20.8 g wet mass (WM) collected off Cape Town (33.9°S, 18.5°E, 12/2009) and in the northern Benguela (17–24°S, 11–15°E, 02/2011). Routine metabolic rate (RMR) and standard routine rate (SRR) (mg O₂ h^?1) followed the allometric functions RMR = 0.418 WM^0.774 and SRR = 0.275 WM^0.855, respectively. Larvae and juveniles had comparatively high metabolic rates, and the energy demand of juveniles at the upper end of the size range appeared too high to be fuelled by a copepod diet alone. T. capensis’ early life stages showed a high tolerance to hypoxic conditions. RMR in larvae did not change until 30 % O₂sat at 18 °C. In juveniles, critical oxygen saturation levels were low (P_C for SRR = 11.2 ± 1.7 % O₂sat and P_C for RMR = 13.2 ± 1.6 % O₂sat at 20 °C) and oxy-regulation effective (regulation index = 0.78 ± 0.09). A high hypoxia tolerance may facilitate the retention of larvae in near-shore waters providing favourable feeding conditions and allowing juveniles to exploit food resources in the oxygen minimum zone. These mechanisms seem to well adapt T. capensis to a habitat affected by spreading hypoxic zones and probably enhance its recruitment success.     

The value of composting in Germany – Economy,ecology, and legislation

Based on a recent survey of German composting plants an evaluation of costs and benefits of composting was attempted. In this regard, several economical, ecological and legal aspects and some interrelations are discussed in this paper. A special emphasis is placed on the fees and compost prices of composting plants. It is also shown how the legal framework provides the economic basis for composting in Germany, how economical and ecological costs and benefits could be assessed, and why it is so difficult to determine the value of composting.     

Pilot scale field test for compostable packaging materials in the City of Kassel, Germany

Biodegradable (compostable) packaging materials made from biopolymers (BP) are introduced into the market to reduce the amounts of conventional packaging materials and at the same time be recovered by the municipal organic waste collection system. The processing of this organic waste mixed with biopolymers has been tested in a commercial treatment facility. The safe use of the compost produced from these materials was demonstrated in a full-scale agricultural application test.     

Cloning and expression of a tauropine dehydrogenase from the marine sponge <Emphasis Type="Italic">Suberites </Emphasis><Emphasis Type="Italic">domuncula</Emphasis>

The cDNA sequence coding for tauropine dehydrogenase (TaDH) [belonging to the family of opine dehydrogenases] has been determined. Using the demosponge Suberites domuncula, we describe for the first time the tauropine dehydrogenase gene (of length 2,992 kb) from a eukaryote, consisting of two introns flanked by three exons. Moreover, two allelic variants have been identified, which are present in the different specimens either in a homozygotic or in a heterozygotic way; the data suggest an intermediary type of heritance. Phylogenetic analyses indicate that S. domuncula TaDH is only distantly related to the opine dehydrogenases from marine invertebrates; rather it comprises high sequence similarity to bacterial ornithine cyclodeaminases (OCD). In addition, expression studies revealed that the steady-state level of TaDH dropped drastically in animals, which had been exposed to elevated aeration. Antibodies raised against the recombinant sponge TaDH were used to demonstrate that S. domuncula expresses high levels of this enzyme in almost all cells. If tissue samples were kept under additional aeration no immuno-signals could be identified. A strong accumulation of the enzyme was seen around the bacteria, existing in bacteriocytes, indicating that under aerobic conditions the bacteria might produce taurine. These data suggest involvement of the sponge TaDH in the final step of the glycolytic pathway, more specifically, in regeneration of NAD(+) under anaerobic conditions. Furthermore, potential mutual influences between bacteria and sponge are discussed, claiming a horizontal gene transfer of the gene from a bacterium to the sponge. The following sequences from Suberites domuncula have been deposited (EMBL/GenBank): the cDNA encoding the tauropine [(carboxyethyl)-taurine/derived from sulfhydryl-amino acids] dehydrogenase (SD_TaDH) under AM712888; the corresponding gene under AM712889; and the fragments of the sponge-associated bacteria comprising the opine dehydrogenase domain: SUBDO_BAC1 (AM712890), SUBDO_BAC2 (AM712891), SUBDO_BAC3 (AM712892), SUBDO_BAC5 (AM712894), SUBDO_BAC6 (AM712895), SUBDO_BAC7 (AM712896), SUBDO_BAC8 (AM712897) and SUBDO_BAC9 (AM712898).     

Ökologische Aspekte des Phosphor-Kreislaufs

In contrast to the complex N-cycle with its high number of reactive compounds, the global P-cycle is uncomplicated. There is only one reactive compound (PO₄ ^3?), and the atmosphere is practically not involved. Nevertheless, severe ecological imbalances may be induced by anthropogenic perturbations of the P-cycle, especially in aquatic ecosystems. The present knowledge on the global P-cycle (reservoirs, fluxes, residence times) is summarized and the ecological dimension of increased phosphorus inputs into surface waters is discussed in detail. Exemplary for Germany, the role of agriculture is described in this context. The fact that the rock phosphate resources are principally limited and not renewable is of a high ecological and economical relevance. The expected lifetime of the P-reserves is calculated for different estimate-scenarios concerning the magnitude of reserves and consumption. Measures to reduce the P-surplus in agriculture, to increase the efficiency of P-fertilization, and to recycle P more consequently are therefore highly required.     

Correlates of group size in a cooperatively breeding cichlid fish (Neolamprologus pulcher)

Neolamprologus pulcher, a cooperatively breeding cichlid fish from Lake Tanganyika, lives in permanent social groups comprising one breeding pair and helpers of both sexes. Variation in group size (1-14 helpers) provides an opportunity to investigate factors that affect how many helpers remain in a group and in turn how group size affects reproductive success. This field study showed that larger groups live in larger territories with more shelter. Group size was more strongly correlated with territory quality than with breeder size. Experimental enhancement of territory quality did not affect group size but group size decreased when territory quality was reduced. Breeders living in a large group benefit because such individuals feed more often and have lower workloads and greater reproductive success. Helpers in larger groups also fed more frequently but did not have lower workloads. This is one of the first experimental studies to examine the factors influencing group size in cooperative breeders.     

?kotoxikologie soll endlich wissenschaftliches Fach werden

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