The genus Pseudo-nitzschia (Bacillariophyceae) in continental shelf waters of Argentina (Southwestern Atlantic Ocean, 38–55°S)

The distribution pattern of Pseudo-nitzschia species, associated phytoplankton flora and its relationships with main environmental factors were studied for the first time in continental shelf surface waters of the Argentine Sea (Southwestern Atlantic Ocean, 38–55°S). Both qualitative and quantitative samples, collected during summer and fall 2003, were examined using light and scanning electron microscopy. Results indicated that the genus Pseudo-nitzschia has a wide distribution along the studied area. It was present at low densities, with infrequent peak abundances and appeared most frequently as a minor component of the diatom populations that typically develop on the continental shelf of the Argentine Sea. Moreover, phytoplankton communities were numerically dominated by unidentified phytoflagellates (≤5 μm) throughout almost all samples analyzed. Eight Pseudo-nitzschia species were identified in our study: P. australis, P. fraudulenta, P. heimii, P. lineola, P. pungens, P. cf. subcurvata, P. turgidula and P. turgiduloides. Of these, P. heimii, P. lineola and P. turgiduloides are new records for the Argentine Sea. Their presence in the area is attributable to the influence of southerly cold water masses. Spatial and temporal variations of the environmental parameters recorded in the study area generally determined the distribution of Pseudo-nitzschia species. P. pungens and P. australis were widely distributed and reached high densities, especially in waters with elevated temperatures and salinities (around 15 °C, 33.8 psu) and low nutrients concentrations. On the other hand, P. heimii, P. lineola, P. turgidula and P. turgiduloides showed a more restricted distribution, with lower densities in relatively cold, less saline (8 °C, 32.45 psu) and nutrient-rich waters. From the Pseudo-nitzschia species found throughout this survey, P. australis, P. fraudulenta, P. pungens and P. turgidula are known as domoic acid (DA) producers around the world, but there is little information on the potential toxicity of these species in Argentina.     

Climate change enhances primary production in the western Antarctic Peninsula

Intense regional warming was observed in the western Antarctic Peninsula (WAP) over the last 50 years. Here, we investigate the impact of climate change on primary production (PP) in this highly productive region. This study is based on temporal data series of ozone thickness (1972–2010), sea ice concentration (1978–2010), sea‐surface temperature (1990–2010), incident irradiance (1988–2010) and satellite‐derived chlorophyll a concentration (Chl‐a, 1997–2010) for the coastal WAP. In addition, we apply a photosynthesis/photoinhibition spectral model to satellite‐derived data (1997–2010) to compute PP and examine the separate impacts of environmental forcings. Since 1978, sea ice retreat has been occurring earlier in the season (in March in 1978 and in late October during the 2000s) while the ozone hole is present in early spring (i.e. August to November) since the early 1990s, increasing the intensity of ultraviolet‐B radiation (UVBR, 280–320 nm). The WAP waters have also warmed over 1990–2010. The modelled PP rates are in the lower range of previously reported PP rates in the WAP. The annual open water PP in the study area increased from 1997 to 2010 (from 0.73 to 1.03 Tg C yr^?1) concomitantly with the increase in the production season length. The coincidence between the earlier sea ice retreat and the presence of the ozone hole increased the exposure to incoming radiation (UVBR, UVAR and PAR) and, thus, increased photoinhibition during austral spring (September to November) in the study area (from 0.014 to 0.025 Tg C yr^?1). This increase in photoinhibition was minor compared to the overall increase in PP, however. Climate change hence had an overall positive impact on PP in the WAP waters.     

Impact of yellow fever outbreaks on two howler monkey species (Alouatta guariba clamitans and A. caraya) in Misiones,Argentina

Two yellow fever outbreaks (YFOs) ocurred in northeastern Argentina between November 2007 and October 2008, seriously affecting populations of two howler monkey species: the brown howler Alouatta guariba clamitans and the black howler Alouatta caraya. Both howlers live syntopically in El Piñalito Provincial Park, Misiones, where four groups (36 individuals) were studied since January 2005. The first dead howlers were found on January 20, 2008, in El Piñalito. Systematic searches found 14 dead howlers within the area (12 from the study groups and two from neighboring groups), with only two young seen on January 25, 2008, and none found since up to December 2008. In October 2008, another YFO hit howler monkey populations from El Soberbio, Misiones. Overall, 59 howlers were found dead in Misiones from November 2007 to December 2008. Thanks to the alert of the howler's death in El Piñalito, a prompt human vaccination campaign started in the area. Wild howler monkey populations from both species are in a delicate situation in Misiones, especially the brown howler, an already endangered species in Argentina and endemic to the Atlantic Forest. If we add the recurrence of YFOs to the reduction of suitable habitat to small fragments, it could be only a matter of time until howler populations disappear from the Upper Paraná Atlantic Forest in Misiones. Am. J. Primatol. 72:475–480, 2010. © 2010 Wiley‐Liss, Inc.     

Non-Thermal Plasmas Affect Plant Growth and DNA Methylation Patterns in Glycine max

Journal of Plant Growth Regulation - Non-thermal plasmas (NTP) are partially ionized gases that represent a promising technology for seed treatment to enhance seed health while promoting...     

Ultraviolet-B effects on photosystem II efficiency of natural phytoplankton communities from Antarctica

The impact of UVB on the Antarctic phytoplankton photosystem II repair cycle, involving the rapidly cycled D1 protein, was studied during summer 2002. On sunny and overcast days, phytoplankton (from 1-m depth) were exposed to natural light (+UVB) and Mylar-screened (–UVB) conditions. Half of the samples from each treatment were inoculated with lincomycin, an inhibitor of synthesis of chloroplast-encoded proteins including the D1 protein. Blocking D1 repair caused significant F_v/F_m depressions on sunny days but had not effect on the overcast day. Most of the F_v/F_m depression was caused by PAR and UVA with a non-significant contribution from UVB. In the presence of D1 repair, suppressing UVB had no effect on F_v/F_m when the samples originated from a weakly stratified water column with no defined upper mixed layer (UML) while it alleviated F_v/F_m depression when the phytoplankton samples originated from within an UML deeper than the depth of UVB penetration. These results suggest that UVB had more effect on the D1 repair process than on the damage process itself but that phytoplankton sensitivity to surface UVB exposure was influenced by their previous light history, partly determined by the vertical structure of the water column.     

Signaling in the mammalian circadian clock: the NO/cGMP pathway

Mammalian circadian rhythms are generated by a hypothalamic suprachiasmatic nuclei (SCN) clock. Light pulses synchronize body rhythms by inducing phase delays during the early night and phase advances during the late night. Phosphorylation events are known to be involved in circadian phase shifting, both for delays and advances. Pharmacological inhibition of the cGMP-dependent kinase (cGK) or Ca2+/calmodulin-dependent kinase (CaMK), or of neuronal nitric oxide synthase (nNOS) blocks the circadian responses to light in vivo. Light pulses administered during the subjective night, but not during the day, induce rapid phosphorylation of both p-CAMKII and p-nNOS (specifically phosphorylated by CaMKII). CaMKII inhibitors block light-induced nNOS activity and phosphorylation, suggesting a direct pathway between both enzymes. Furthermore, SCN cGMP exhibits diurnal and circadian rhythms with maximal values during the day or subjective day. This variation of cGMP levels appears to be related to temporal changes in phosphodiesterase (PDE) activity and not to guanylyl cyclase (GC) activity. Light pulses increase SCN cGMP levels at circadian time (CT) 18 (when light causes phase advances of rhythms) but not at CT 14 (the time for light-induced phase delays). cGK II is expressed in the hamster SCN and also exhibits circadian changes in its levels, peaking during the day. Light pulses increase cGK activity at CT 18 but not at CT 14. In addition, cGK and GC inhibition by KT-5823 and ODQ significantly attenuated light-induced phase shifts at CT 18. This inhibition did not change c-Fos expression SCN but affected the expression of the clock gene per in the SCN. These results suggest a signal transduction pathway responsible for light-induced phase advances of the circadian clock which could be summarized as follows: Glu-Ca2+-CaMKII-nNOS-GC-cGMP-cGK-->-->clock genes. This pathway offers a signaling window that allows peering into the circadian clock machinery in order to decipher its temporal cogs and wheels.     

Mating system parameters in species of genus Prosopis (Leguminosae)

The section Algarobia of genus Prosopis involves important natural resources in arid and semiarid regions of the world. Their rationale use requires a better knowledge of their biology, genetics and mating system. There are contradictory information about their mating system. Some authors claim they are protogynous and obligate outcrosser. However, some evidence have been shown indicating that they might not be protogynous and that they might be somewhat self-fertile. The current paper analyses genetic structure and mating system parameters in populations of seven species of this section from South and North America based on isozyme data. In all species a significant homozygote excess was found in the offspring population but not in mother plant genotypes. Multilocus and mean single locus outcrossing rates (tm, ts) indicated that about 15% selfing can occur in the studied populations. The heterogeneity between pollen and ovule allele frequencies was low suggesting population structuration, in agreement with the estimates of correlation of tm within progeny (rt) and correlation of outcrossed paternity (rp). The difference of FIS estimates between offspring and mother plants suggest some selection favouring heterozygotes between seedling and adult stages.