Evaluation of passive samplers as a monitoring tool for early warning of Dinophysis toxins in shellfish

From June 2006 to January 2007 passive samplers (solid phase adsorbing toxin tracking, SPATT) were tested as a monitoring tool with weekly monitoring of phytoplankton and toxin content (liquid chromatography–mass spectrometry, LC-MS) in picked cells of Dinophysis and plankton concentrates. Successive blooms of Dinophysis acuminata, D. acuta and D. caudata in 2006 caused a long mussel harvesting closure (4.5 months) in the Galician Rías (NW Spain) and a record (up to 9246 ng·g resin-week−1) accumulation of toxins in SPATT discs. Best fit of a toxin accumulation model was between toxin accumulation in SPATT and the product of cell densities by a constant value, for each species of Dinophysis, of toxin content (average) in picked cells. Detection of Dinophysis populations provided earlier warning of oncoming diarrhetic shellfish poisoning (DSP) outbreaks than the SPATT, which at times overestimated the expected toxin levels in shellfish because: (i) SPATT accumulated toxins did not include biotransformation and depuration loss terms and (ii) accumulation of toxins not available to mussels continued for weeks after Dinophysis cells were undetectable and mussels were toxin-free. SPATT may be a valuable environmental monitoring and research tool for toxin dynamics, in particular in areas with no aquaculture, but does not provide a practical gain for early warning of DSP outbreaks

Bloom dynamics and life cycle strategies of two toxic dinoflagellates in a coastal upwelling system (NW Iberian Peninsula)

A study of Gymnodinium catenatum and Alexandrium minutum blooms on the Galician coast was conducted from 2005 to 2007 in order to increase knowledge of the mechanisms governing recurrent blooms of these species. Considerable differences in their bloom dynamics were observed. G. catenatum blooms occurred in autumn and winter, following the pattern previously reported in the literature: they began offshore and were advected to the Galician rias when a relaxation of the coastal upwelling occurred. On the other hand, A. minutum blooms developed inside embayments in spring and summer during the upwelling season and were associated with water stability and stratification. Both the vegetative population and the cyst distribution of A. minutum were related to less saline water from freshwater river outputs, which supports a saline-gradient relationship postulated herein for this species. Dinoflagellates may produce both long-term double-walled cysts (resting) and short-term pellicle cysts. Resting cyst deposition and distribution in sediments showed that seeding occurred during the blooms of both species. However, the relationship between the cyst distribution in the sediments in Baiona Bay and the intensity and occurrence of G. catenatum blooms, suggests that the latter are not directly related to resting cyst germination. Moreover, the results presented in the present study point to other difference between the two species, such as the detection of pellicle cysts only for A. minutum. Finally we discuss how the life cycle strategies of these two species may help to explain the different mechanisms of bloom formation reported herein.Versión del editor2,277

Exploring the conditions leading to an exceptional early bloom of Dinophysis acuminata in northwest Spain during 2012

In a conceptual model proposed before, the onset of the upwelling season and availability of Mesodinium rubrum prey are essential conditions for the initiation of Dinophysis acuminata blooms in the Galician Rías Baixas (NW Spain). Distribution of sexual cysts from the previous year in the top sediment layer is an important parameter in forecasting models of cyst-forming species (e.g. Alexandrium spp.). But the existence of sexual cysts of Dinophysis spp. has not been confirmed, Dinophysis planozygotes can divide and produce vegetative cells directly, and it is possible that species of this genus do not rely on sexual cysts but on some kind of overwintering planktonic form as a seeding mechanism. Here we examine winter conditions—persistence or absence of overwintering cells of Dinophysis within the rías and the adjacent shelf and time of initiation of the upwelling season—from observations in the last 20 years. Our ultimate goal was to explain the abundance and early initiation in April 2012 of an extraordinary bloom of D. acuminata, in what appeared to be a mesoscale event affecting other regions in Western Europe. The dynamics of D. acuminata populations appeared tightly coupled to the upwelling season. Our results suggest that anomalous upwelling patterns (predominance of upwelling in winter) combined with the presence of overwintering (inoculum) cells lead to early initiation of the Dinophysis acuminata growth seasonEn prens

Climate Variability and Oceanographic Settings Associated with Interannual Variability in the Initiation of Dinophysis acuminata Blooms

In 2012, there were exceptional blooms of D. acuminata in early spring in what appeared to be a mesoscale event affecting Western Iberia and the Bay of Biscay. The objective of this work was to identify common climatic patterns to explain the observed anomalies in two important aquaculture sites, the Galician Rías Baixas (NW Spain) and Arcachon Bay (SW France). Here, we examine climate variability through physical-biological couplings, Sea Surface Temperature (SST) anomalies and time of initiation of the upwelling season and its intensity over several decades. In 2012, the mesoscale features common to the two sites were positive anomalies in SST and unusual wind patterns. These led to an atypical predominance of upwelling in winter in the Galician Rías, and increased haline stratification associated with a southward advection of the Gironde plume in Arcachon Bay. Both scenarios promoted an early phytoplankton growth season and increased stability that enhanced D. acuminata growth. Therefore, a common climate anomaly caused exceptional blooms of D. acuminata in two distant regions through different triggering mechanisms. These results increase our capability to predict intense diarrhetic shellfish poisoning outbreaks in the early spring from observations in the preceding winter

Dysregulation of Macrophage-Secreted Cathepsin B Contributes to HIV-1-Linked Neuronal Apoptosis

Chronic HIV infection leads to the development of cognitive impairments, designated as HIV-associated neurocognitive disorders (HAND). The secretion of soluble neurotoxic factors by HIV-infected macrophages plays a central role in the neuronal dysfunction and cell death associated with HAND. One potentially neurotoxic protein secreted by HIV-1 infected macrophages is cathepsin B. To explore the potential role of cathepsin B in neuronal cell death after HIV infection, we cultured HIV-1ADA infected human monocyte-derived macrophages (MDM) and assayed them for expression and activity of cathepsin B and its inhibitors, cystatins B and C. The neurotoxic activity of the secreted cathepsin B was determined by incubating cells from the neuronal cell line SK-N-SH with MDM conditioned media (MCM) from HIV-1 infected cultures. We found that HIV-1 infected MDM secreted significantly higher levels of cathepsin B than did uninfected cells. Moreover, the activity of secreted cathepsin B was significantly increased in HIV-infected MDM at the peak of viral production. Incubation of neuronal cells with supernatants from HIV-infected MDM resulted in a significant increase in the numbers of apoptotic neurons, and this increase was reversed by the addition of either the cathepsin B inhibitor CA-074 or a monoclonal antibody to cathepsin B. In situ proximity ligation assays indicated that the increased neurotoxic activity of the cathepsin B secreted by HIV-infected MDM resulted from decreased interactions between the enzyme and its inhibitors, cystatins B and C. Furthermore, preliminary in vivo studies of human post-mortem brain tissue suggested an upregulation of cathepsin B immunoreactivity in the hippocampus and basal ganglia in individuals with HAND. Our results demonstrate that HIV-1 infection upregulates cathepsin B in macrophages, increases cathepsin B activity, and reduces cystatin-cathepsin interactions, contributing to neuronal apoptosis. These findings provide new evidence for the role of cathepsin B in neuronal cell death induced by HIV-infected macrophages

Noctiluca scintillans may act as a vector of toxigenic microalgae

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The growth season of Dinophysis acuminata in an upwelling system embayment. A conceptual model based on in situ measurements

The distribution and physiological condition of the DSP-toxin producerDinophysis acuminata, its relation with accompanying microplankton populations and coupling with upwelling events are described based on weekly sampling at afixed station in Ría de Pontevedra, Galician Rías Baixas, NW Spain between March and December 2007.D. acuminatawas detected from 18 June to 01 October. The appearance of D. acuminatain the Ría coincided with an upwelling-relaxation event and a short-lived maximum (up to 27 000 cells L −1 ) of its potential prey, the phototrophic ciliateMesodiniumcfrubrum. An increase in the proportion of vacuolatedDinophysiscells (72%) observed one week later suggests that the bloom was triggered by heterotrophic feeding on a co-occurring peak of Mesodiniumcoupled with advection of Dinophysiscells into the ría. Elevated frequencies of cells with starch and vacuoles were closely associated with the presence ofM.cfrubrum during the entire bloom season. However, peaks in the frequency of vacuolated cells were only recorded on a few occasions, suggesting that D. acuminatais prey-limited most of the time but does not require a constant supply of prey for long term survival. Infection of D. acuminataby the parasite dinoflagellateAmoebophryasp., a potential loss factor in the population dynamics of dinoflagellate populations, was observed (1–17% prevalence) immediately prior to the decline of the bloom. A conceptual model is presented of the mechanisms by whichD. acuminata blooms develop in a ría influenced by upwelling which utilizes a combination of physics (upwellingpromoted shoreward transport ofDinophysisinoculum) and the match–mismatch of predator–prey (DinophysisandMesodinium) populations.Versión del editor

New life-cycle stages of Gymnodinium catenatum (dinophyceae): laboratory and field observations

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