Subtidal macrozoobenthos communities from northern Chile during and post El Niño 1997–1998

Despite a large amount of climatic and oceanographic information dealing with the recurring climate phenomenon El Niño (EN) and its well known impact on diversity of marine benthic communities, most published data are rather descriptive and consequently our understanding of the underlying mechanisms and processes that drive community structure during EN are still very scarce. In this study, we address two questions on the effects of EN on macrozoobenthic communities: (1) how does EN affect species diversity of the communities in northern Chile? and (2) is EN a phenomenon that restarts community assembling processes by affecting species interactions in northern Chile? To answer these questions, we compared species diversity and co-occurrence patterns of soft-bottoms macrozoobenthos communities from the continental shelf off northern Chile during (March 1998) and after (September 1998) the strong EN event 1997–1998. The methods used varied from species diversity and species co-occurrence analyses to multivariate ordination methods. Our results indicate that EN positively affects diversity of macrozoobenthos communities in the study area, increasing the species richness and diversity and decreasing the species dominance. EN represents a strong disturbance that affects species interactions that rule the species assembling processes in shallow-water, sea-bottom environments

Time-Frequency Analysis of Chemosensory Event-Related Potentials to Characterize the Cortical Representation of Odors in Humans

BACKGROUND: The recording of olfactory and trigeminal chemosensory event-related potentials (ERPs) has been proposed as an objective and non-invasive technique to study the cortical processing of odors in humans. Until now, the responses have been characterized mainly using across-trial averaging in the time domain. Unfortunately, chemosensory ERPs, in particular, olfactory ERPs, exhibit a relatively low signal-to-noise ratio. Hence, although the technique is increasingly used in basic research as well as in clinical practice to evaluate people suffering from olfactory disorders, its current clinical relevance remains very limited. Here, we used a time-frequency analysis based on the wavelet transform to reveal EEG responses that are not strictly phase-locked to onset of the chemosensory stimulus. We hypothesized that this approach would significantly enhance the signal-to-noise ratio of the EEG responses to chemosensory stimulation because, as compared to conventional time-domain averaging, (1) it is less sensitive to temporal jitter and (2) it can reveal non phase-locked EEG responses such as event-related synchronization and desynchronization. METHODOLOGY/PRINCIPAL FINDINGS: EEG responses to selective trigeminal and olfactory stimulation were recorded in 11 normosmic subjects. A Morlet wavelet was used to characterize the elicited responses in the time-frequency domain. We found that this approach markedly improved the signal-to-noise ratio of the obtained EEG responses, in particular, following olfactory stimulation. Furthermore, the approach allowed characterizing non phase-locked components that could not be identified using conventional time-domain averaging. CONCLUSION/SIGNIFICANCE: By providing a more robust and complete view of how odors are represented in the human brain, our approach could constitute the basis for a robust tool to study olfaction, both for basic research and clinicians

ANCA-associated vasculitis.

The anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are a group of disorders involving severe, systemic, small-vessel vasculitis and are characterized by the development of autoantibodies to the neutrophil proteins leukocyte proteinase 3 (PR3-ANCA) or myeloperoxidase (MPO-ANCA). The three AAV subgroups, namely granulomatosis with polyangiitis (GPA), microscopic polyangiitis and eosinophilic GPA (EGPA), are defined according to clinical features. However, genetic and other clinical findings suggest that these clinical syndromes may be better classified as PR3-positive AAV (PR3-AAV), MPO-positive AAV (MPO-AAV) and, for EGPA, by the presence or absence of ANCA (ANCA+ or ANCA-, respectively). Although any tissue can be involved in AAV, the upper and lower respiratory tract and kidneys are most commonly and severely affected. AAVs have a complex and unique pathogenesis, with evidence for a loss of tolerance to neutrophil proteins, which leads to ANCA-mediated neutrophil activation, recruitment and injury, with effector T cells also involved. Without therapy, prognosis is poor but treatments, typically immunosuppressants, have improved survival, albeit with considerable morbidity from glucocorticoids and other immunosuppressive medications. Current challenges include improving the measures of disease activity and risk of relapse, uncertainty about optimal therapy duration and a need for targeted therapies with fewer adverse effects. Meeting these challenges requires a more detailed knowledge of the fundamental biology of AAV as well as cooperative international research and clinical trials with meaningful input from patients

Living on Cold Substrata: New Insights and Approaches in the Study of Microphytobenthos Ecophysiology and Ecology in Kongsfjorden

Organisms in shallow waters at high latitudes are under pressure due to climate change. These areas are typically inhabited by microphytobenthos (MPB) communities, composed mainly of diatoms. Only sparse information is available on the ecophysiology and acclimation processes within MPBs from Arctic regions. The physico-chemical environment and the ecology and ecophysiology of benthic diatoms in Kongsfjorden (Svalbard, Norway) are addressed in this review. MPB biofilms cover extensive areas of sediment. They show high rates of primary production, stabilise sediment surfaces against erosion under hydrodynamic forces,and affect the exchange of oxygen and nutrients across the sediment-water interface. Additionally, this phototrophic community represents a key component in the functioning of the Kongsfjorden trophic web, particularly as a major food source for benthic suspension- or deposit-feeders. MPB in Kongsfjorden is confronted with pronounced seasonal variations in solar radiation, low temperatures, and hyposaline (meltwater) conditions in summer, as well as long periods of ice and snow cover in winter. From the few data available, it seems that these organisms can easily cope with these environmental extremes. The underlying physiological mechanisms that allow growth and photosynthesis to continue under widely varying abiotic parameters, along with vertical migration and heterotrophy, and biochemical features such as a pronounced fatty-acid metabolism and silicate incorporation are discussed. Existing gaps in our knowledge of benthic diatoms in Kongsfjorden, such as the chemical ecology of biotic interactions, need to be filled. In addition, since many of the underlying molecular acclimation mechanisms are poorly understood, modern approaches based on transcriptomics, proteomics, and/or metabolomics, in conjunction with cell biological and biochemical techniques, are urgently needed. Climate change models for the Arctic predict other multifactorial stressors, such as an increase in precipitation and permafrost thawing, with consequences for the shallow-water regions. Both precipitation and permafrost thawing are likely to increase nutrient-enriched, turbid freshwater runoff and may locally counteract the expected increase in coastal radiation availability. So far, complex interactions among factors, as well as the full genetic diversity and physiological plasticity of Arctic benthic diatoms, have only rarely been considered. The limited existing information is described and discussed in this review

Population dynamics and reproduction biology of Donax marincovichi (Coan 1983) from Playa Jahuay (Peru)

Bivalves of the genus Donax are commonly dominating the macrofauna of exposed sandy beaches (Ansell 1983). The family is worldwide distributed and comprises 64 species. At Playa Jahuay (S13°2433, W76°1149) located 180km south of Lima a dense population of D. marincovichi is present since decades. During a one year study monthly samples are taken to analyse the population dynamic. First results indicate distinct cohorts. Histology carried out will be carried out to analyse the reproduction cycle of this species showed separate sexes and no hermaphrodites

In situ breathing and filtration rates of Gari solida (Gray, 1828) in Paracas Bay.

Gari solida is an economically important sub tidal bivalve that inhabits shallow waters of Peru and Chile. Its respiration (RR) and filtration (FR) rates were analyzed in situ on individuals belonging to three ranges of size (45-55mm, 72-87mm and 92-97mm) in Paracas Bay. Experiments were conducted during the months of March 2007, August 2007 and February 2008 and consisted in the installation of twelve acrylic chambers, placed on the seabed at a depth of 4 m, fitted with electric submersible pumps for the recirculation of water, so the individuals could stayed in a closed system through a specific time. The RR and FR per gram of individual were about 4 times bigger in smaller individuals (RR = 0.22 mg h ̅ 1.g ̅ 1, FR = 0.38 L.h ̅ 1.g ̅ 1) compared to the larger size ranges (RR = 0.05 mg h ̅ 1.g ̅ 1, FR=0.08 L.h ̅ 1.g ̅ 1), which could be due to the increase in tissues of low metabolism as the animals grow. Furthermore, we found no relationship between the levels of dissolved oxygen (5 - 9 mg/L) and chlorophyll-a (2 5 μg/L) present during the evaluations and the physiological rates obtained, however, a seasonal change in the respiration rates was observed obtaining higher averages for the larger individuals during the winter (0.17 mg h ̅ 1.g ̅ 1) when compared with the summer (0.12 mg h ̅ 1.g ̅ 1). Finally, after analyzing the composition of phytoplankton on filtered water, G. solida showed a clear preference for phytoflagellates organisms (75%) in its diet

The effect of hydrozoan fouling on the burrowing of Donax marincovichi (Bivalvia, Donacidae) at Chinchorro beach, Northern Chile

Surf clams Donax marincovichi inhabit the intertidal zone of high-energy sandy beaches from southern Peru to northern Chile. These bivalves are well adapted to their dynamic environment by being able to quickly borrow into the sediment, once the clams are washed out or undergo their tidal migration. This behaviour is necessary to escape predators. At reflected beaches north of Arica, the posterior end of the bivalves is commonly monospecifically fouled by hydrozoans (Clytia sp.), an epibiosis that has not been described before. This study investigated the effect of these epibionts on the burrowing performance of D. marincovichi. Burial time and burrowing intensity were obtained from 64 individuals, of which 32 were colonized by Clytia sp. and 32 were macroscopically clean. The burial times of the tested individuals did not correlate with shell length (25 to 33 mm). Burial times were not significantly different between fouled and clean D. marincovichi. However, significantly more fouled individuals completed burrowing, while more clean clams stopped just before the valves were covered with sediment. Burrowing time averaged at 25.7 seconds and is therefore within the range of swash periods on Chinchorro beach (10 to 32 seconds) enabling the clams to hide from fish, crab and birds