Reproduction and condition of female Octopus mimus (Mollusca: Cephalopoda)

The relationship between reproduction and condition was studied in a 15 mo sample of 919 maturing, mature and post-spawning female Octopus mimus (388 to 3714 g) caught in Iquique (North Chile). O. mimus is a semelparous species, with reproduction taking place all year round. Investment in reproductive tissues was, on average, 9.9% of mature female body weight, independent of season. However, somatic growth during maturation was dependent on season and varied between 26 and 63% of the whole-body growth in weight. The condition of females did not vary markedly until spawning, although seasonal variations were apparent, winter being the most unfavourable. Condition deteriorated dramatically after spawning, during parental care of the eggs. During this period, somatic-tissue depletion, mainly from the muscles, was >25% of the total body weight of mature females. The fecundity of O. mimus was probably limited by the costs associated with parental care of the eggs

Global change effects on a mechanistic decomposer food web model

Global change may affect the structure and functioning of decomposer food webs through qualitative changes in freshly fallen litter. We analyzed the predicted effects of a changing environment on a dynamic model of a donor-controlled natural decomposer ecosystem near Wekerom, the Netherlands. This system consists of fungi, bacteria, fungivores, bacterivores and omnivores feeding on microbiota and litter as well. The model concentrates on carbon and nitrogen flows through the trophic niches that define this decomposer system, and is designed to predict litter masses and abundances of soil biota. For modeling purposes, the quality of freshly fallen leaf litter is defined in terms of nitrogenous and non-nitrogenous components, of which refractory and labile forms are present. The environmental impacts of elevated C

Relationship between bacterial and primary production in a newly filled reservoir: temporal variability over 2 consecutive years

International audienceSeasonal and spatial variations in bacterial abundance, biomass and production in a recently flooded reservoir were followed for 2 consecutive years, in conjunction with phytoplankton biomass (chlorophyll a) and activity (primary production). Between the 2 years of the study, the mean value of primary production remained constant, while those of the chlorophyll a concentration, bacterial abundance (BA), bacterial biomass (BB) and bacterial production (BP) decreased. The observed trends of the bacterial variables were linked to changes in the relative importance of allochthonous dissolved organic matter. Moreover, this factor would explain discrepancies observed between the slope of the model II regression equations established from results of the present study and those of the predictive models from the literature, relating to bacterial and phytoplankton variables. An estimate of the carbon budget indicated that 22 and 5% of the ambient primary production in the Sep Reservoir might be channeled through the microbial loop via BP during the 1st and 2nd year of the study, respectively. We conclude that heterotrophic BP in the Sep Reservoir may, on occasion, represent a significant source of carbon for higher order consumers

Pre-exposure to simultaneous, but not individual, climate change stressors limits acclimation capacity of Irukandji jellyfish polyps to predicted climate scenarios

Researchers have investigated the immediate effects of end-of-century climate change scenarios on many marine species, yet it remains unclear whether we can reliably predict how marine species may respond to future conditions because biota may become either more or less resistant over time. Here, we examined the role of pre-exposure to elevated temperature and reduced pH in mitigating the potential negative effects of future ocean conditions on polyps of a dangerous Irukandji jellyfish Alatina alata. We pre-exposed polyps to elevated temperature (28 °C) and reduced pH (7.6), in a full factorial experiment that ran for 14 d. We secondarily exposed original polyps and their daughter polyps to either current (pH 8.0, 25 °C) or future conditions (pH 7.6, 28 °C) for a further 34 d to assess potential phenotypic plastic responses and whether asexual offspring could benefit from parental pre-exposure. Polyp fitness was characterised as asexual reproduction, respiration, feeding, and protein concentrations. Pre-exposure to elevated temperature alone partially mitigated the negative effects of future conditions on polyp fitness, while pre-exposure to reduced pH in isolation completely mitigated the negative effects of future conditions on polyp fitness. Pre-exposure to the dual stressors, however, reduced fitness under future conditions relative to those in the control treatment. Under future conditions, polyps had higher respiration rates regardless of the conditions they were pre-exposed to, suggesting that metabolic rates will be higher under future conditions. Parent and daughter polyps responded similarly to the various treatments tested, demonstrating that parental pre-exposure did not confer any benefit to asexual offspring under future conditions. Importantly, we demonstrate that while pre-exposure to the stressors individually may allow Irukandji polyps to acclimate over short timescales, the stressors are unlikely to occur in isolation in the long term, and thus, warming and acidification in parallel may prevent polyp populations from acclimating to future ocean conditions.Griffith Sciences, Griffith School of EnvironmentFull Tex