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ArticleImplications of improved representations of plant respiration in a changing climate(Nature Publishing Group, 2017-11-17) Huntingford, Chris ; Atkin, Owen K. ; Martinez-de la Torre, Alberto ; Mercado, Lina M. ; Heskel, Mary ; Harper, Anna B. ; Bloomfield, Keith J. ; O'Sullivan, Odhran S. ; Reich, Peter B. ; Wythers, Kirk R. ; Butler, Ethan E. ; Chen, Ming ; Griffin, Kevin L. ; Meir, Patrick ; Tjoelker, Mark ; Turnbull, Matthew H. ; Sitch, Stephen ; Wiltshire, Andrew J. ; Malhi, YadvinderLand-atmosphere exchanges influence atmospheric CO2. Emphasis has been on describing photosynthetic CO2 uptake, but less on respiration losses. New global datasets describe upper canopy dark respiration (Rd) and temperature dependencies. This allows characterisation of baseline Rd, instantaneous temperature responses and longer-term thermal acclimation effects. Here we show the global implications of these parameterisations with a global gridded land model. This model aggregates Rd to whole-plant respiration Rp, driven with meteorological forcings spanning uncertainty across climate change models. For pre-industrial estimates, new baseline Rd increases Rp and especially in the tropics. Compared to new baseline, revised instantaneous response decreases Rp for mid-latitudes, while acclimation lowers this for the tropics with increases elsewhere. Under global warming, new Rd estimates amplify modelled respiration increases, although partially lowered by acclimation. Future measurements will refine how Rd aggregates to whole-plant respiration. Our analysis suggests Rp could be around 30% higher than existing estimates.
ArticleEndocrine-disrupting alkylphenols are widespread in the blood of lobsters from southern New England and adjacent offshore areas(National Shellfisheries Association, 2012-06) Jacobs, Molly W. ; Laufer, Hans ; Stuart, James ; Chen, Ming ; Pan, XuejunEndocrine-disrupting pollutants in rivers and oceans represent a poorly understood but potentially serious threat to the integrity of aquatic and coastal ecosystems. We surveyed the hemolymph of lobsters from across southern New England and adjacent offshore areas for 3 endocrine-disrupting alkylphenols. We found all 3 compounds in hemolymph from every year and almost every region sampled. Prevalence of contamination varied significantly between regions, ranging from 45% of lobsters from southern Massachusetts to 17% of lobsters from central Long Island Sound. Mean contamination levels varied significantly as a function of region, year sampled, and collection trip, and were highest overall in lobsters from western Long Island Sound and lowest in lobsters from central Long Island Sound. Surprisingly, lobsters from offshore areas were not less contaminated than lobsters from inshore areas. Contamination levels also did not vary as a function of lobster size or shell disease signs. Contaminated lobsters held in the laboratory did not retain alkylphenols, suggesting that hemolymph contamination levels represent recent, rather than long-term, exposure. Our data set is the first, to our knowledge, to survey endocrine-disrupting contaminants in a population across such a broad temporal and spatial scale. We show that alkylphenol contamination is a persistent, widespread, but environmentally heterogeneous problem in lobster populations in southern New England and adjacent offshore areas. Our work raises serious questions about the prevalence and accumulation of these endocrine-disrupting pollutants in an important fishery species.
ArticleThe effect of alkylphenols on lobster shell hardening(National Shellfisheries Association, 2012-06) Laufer, Hans ; Chen, Ming ; Johnson, Michael ; Demir, Neslihan ; Bobbitt, James M.Alkylphenols, anthropogenic estrogenic endocrine disruptors in vertebrates, have been found in lobsters (Homarus americanus) in New England sites. We hypothesize that alkylphenols interfere in the shell hardening during molting. We used an in vitro cuticle bioassay to investigate the effects of 2 alkylphenolic compounds—2,4-bis-(dimethylbenzyl) phenol (compound 3) and bisphenol A (BPA; 4,4′-dihydroxy-2,2-diphenylpropane (also referred to as 4,4′-(propan-2-ylidene) diphenol)) on tyrosine incorporation during the hardening of new cuticle following lobster molting. During sclerotization, both alkylphenols and cold tyrosine competed with C14-tyrosine incorporation in a concentration-dependent manner. This process was also phenoloxidase dependent, as treatment with phenylthiourea (PTU; a phenoloxidase inhibitor) significantly decreased C14-tyrosine incorporation. We also found that incorporation of C14-2,4-bis-(dimethylbenzyl) phenol during the shell hardening process was inhibited by cold alkylphenol, cold tyrosine, or PTU, and competition was concentration dependent. Furthermore, incorporation of tyrosine and derivatives into new cuticle decreased with time after molting from 27% incorporation 1 day after a molt to 6% by 4 days after a molt. In nonmolting cuticles, there was no incorporation of alkylphenol or tyrosine derivatives. When lobsters were injected with 2,4-bis-(dimethylbenzyl) phenol during the premolt stage, it took the shells 12 ± 1 days to harden sufficiently to resist deflection by 5 lb pressure exerted by a pressure gauge, compared with 7 ± 1 days for control shells. Thus, shell hardening is delayed significantly by the presence of 2,4-bis-(dimethylbenzyl) phenol. The effects of this compound on shell hardening may result in lobsters' susceptibility to microbial invasion and, therefore, may contribute to the onset of shell disease.