Shorter Food Chain Length in Ancient Lakes: Evidence from a Global Synthesis

Food webs may be affected by evolutionary processes, and effective evolutionary time ultimately affects the probability of species evolving to fill the niche space. Thus, ecosystem history may set important evolutionary constraints on community composition and food web structure. Food chain length (FCL) has long been recognized as a fundamental ecosystem attribute. We examined historical effects on FCL in large lakes spanning >6 orders of magnitude in age. We found that food chains in the world’s ancient lakes (n = 8) were significantly shorter than in recently formed lakes (n = 10) and reservoirs (n = 3), despite the fact that ancient lakes harbored much higher species richness, including many endemic species. One potential factor leading to shorter FCL in ancient lakes is an increasing diversity of trophic omnivores and herbivores. Speciation could simply broaden the number of species within a trophic group, particularly at lower trophic levels and could also lead to a greater degree of trophic omnivory. Our results highlight a counter-intuitive and poorly-understood role of evolutionary history in shaping key food web properties such as FCL

Acute toxicity of polybrominated diphenyl ethers (PBDEs) for turbot (Psetta maxima) early life stages (ELS)

Background, aim and scope The environmental presence of polybrominated diphenyl ethers (PBDEs), among which BDE-47 and BDE-99 are particularly abundant, makes toxicity data necessary to assess the hazard risk posed by PBDE to aquatic organisms. This study examines the effects of BDE-47 and BDE-99 on embryo-larval stages of the marine flatfish turbot. Materials and methods The turbot embryos were exposed at nominal concentrations of BDE-47 and BDE-99 for 6 days. Selected dose levels were relevant for investigating sublethal and lethal effects. Results Both tested compounds caused lethal toxicity as well as non-lethal malformations during embryo development. We found a high toxic potency of BDE-47 compared to BDE-99 (LC50 values for embryos and larvae, respectively, BDE-47: 27.35 and 14.13 μg L−1; BDE-99: 38.28 and 29.64 μg L−1). Discussion The present study shows high sensitivity of fish early life stages (ELS) to PBDE compounds. Based on environmental concentrations of dissolved PBDEs from various aquatic ecosystems, waterborne BDE-47 and BDE- 99 pose little risk of acute toxicity to marine fish at relevant environmental concentrations. Conclusions Turbot fish ELS proved to be an excellent model for the study of ecotoxicity of contaminants in seawater. The results demonstrate harmful effects of PBDE on turbot ELS at concentrations in the range of parts per billion units. Recommendations and perspectives In the perspective of risk assessment, ELS endpoints provide rapid, costeffective and ecologically relevant information, and links should be sought between these short-term tests and effects of long-term exposures in more realistic scenarios.MAE-PCI CTM2009-10908Versión del editor2,651