Weakened casual feedback loops following intensive restoration efforts and climate changes in a large shallow freshwater lake.

Understanding how phytoplankton interacts with local and regional drivers as well as their feedbacks is a great challenge, and quantitative analyses of the regulating role of human activities and climate changes on these feedback loops are also limited. By using monthly monitoring dataset (2000-2017) from Lake Taihu and empirical dynamic modelling to construct causal networks, we quantified the strengths of causal feedbacks among phytoplankton, local environments, zooplankton, meteorology as well as global climate oscillation. Prevalent bidirectional causal linkages between phytoplankton biomass (chlorophyll a) and the tested drivers were found, providing holistic and quantitative evidence of the ubiquitous feedback loops. Phytoplankton biomass exhibited the highest feedbacks with total inorganic nitrogen and ammonia and the lowest with nitrate. The feedbacks between phytoplankton biomass and environmental factors from 2000 to 2017 could be classified into two groups: the local environments (e.g., nutrients, pH, transparency, zooplankton biomass)-driven enhancement loops promoting the response of the phytoplankton biomass, and the climate (e.g., wind speed)-driven regulatory loops suppressing it. The two counterbalanced groups modified the emergent macroecological patterns. Our findings revealed that the causal feedback networks loosened significantly after 2007 following nutrient loading reduction and unsuccessful biomanipulation restoration attempts by stocking carp. The strength of enhancement loops underwent marked decreases leading to reduced phytoplankton responses to the tested drivers, while the climate (decreasing wind speed, warming winter)-driven regulatory loops increased- like a tug-of-war. To counteract the self-amplifying feedback loops, the present eutrophication mitigation efforts, especially nutrient reduction, should be continued, and introduction of alternative measures to indirectly regulate the critical components (e.g., pH, Secchi depth, zooplankton biomass) of the loops would be beneficial.

Isolation, genomic structure and developmental expression of Fgf8 in the short-tailed fruit bat, Carollia perspicillata.

Fibroblast growth factor-8 (Fgf8) encodes a secreted protein which was initially identified as the factor responsible for androgen-dependant growth of mouse mammary carcinoma cells (Tanaka et al., 1992). Fgf8 has been subsequently implicated in the patterning and growth of the gastrulating embryo, paraxial mesoderm (somites), limbs, craniofacial tissues, central nervous system and other organ systems during the development of several vertebrate model animals. Consistent with these findings, Fgf8 is expressed in a complex and dynamic pattern during vertebrate embryogenesis. Here we report the isolation and characterization of a bat (Carollia perspicillata) Fgf8 orthologue. Compared with those of other model vertebrates, Carollia Fgf8 is conserved with respect to genomic structure, sequence and many domains of developmental expression pattern. Interestingly, the expression domain marking the apical ectodermal ridge of the developing limb shows a striking difference compared to that of mouse, consistent with evolutionary diversification of bat limb morphology.