Time filter

Source Type

Cyclic outbreaks of accumulation of paralytic shellfish poisoning (PSP) toxins in mussels attributed to Gymnodinium catenatum blooms displayed several of the highest inter-annual maxima coincidental with the minima of the 11-year solar sunspot number (SSN) cycle. The monthly distribution of PSP was associated with low levels of the solar radio flux, a more quantitative approach than SSN for fluctuations in solar activity. Comparison between monthly distribution of PSP and other commons biotoxins (okadaic acid, dinophysistoxin-2, and amnesic shellfish poisoning toxins) demonstrated that only PSP was significantly associated with low levels of radio flux (p < 0.01). PSP occurrence suggests a prior decline in solar activity to be required as a trigger, similarly to a photoperiodic signal. The seasonal frequency increased towards autumn during the study period, which might be related to the progressive atmospheric cutoff of deleterious radiation associated with the seasonal change in solar declination, and might play an additional role in seasonal signal-triggering. PSP distribution was also associated with low levels of the geomagnetic index Aa. Comparison between monthly distributions of PSP and other common biotoxins also demonstrated that only PSP was significantly associated with low levels of the Aa index (p < 0.01). In some years of SSN minima, no significant PSP outbreaks in mussels were detected. This was attributed to a steady rise in geomagnetic activity that could disrupt the triggering signal. Global distribution patterns show that hotspots for G. catenatum blooms are regions with deficient crustal magnetic anomalies. In addition to the variable magnetic field mostly of solar origin, static fields related to magnetized rocks in the crust and upper mantle might play a role in restricting worldwide geographic distribution. © 2013 Pleiades Publishing, Inc. Source

Diaz P.A.,FARO | Diaz P.A.,Austral University of Chile | Ruiz-Villarreal M.,Spanish Institute of Oceanography | Pazos Y.,Instituto Tecnoloxico Para O Control Do Medio Marino Of Galicia Intecmar | And 2 more authors.
Harmful Algae

Dinophysis acuta is a frequent seasonal lipophilic toxin producer in European Atlantic coastal waters associated with thermal stratification. In the Galician Rías, populations of D. acuta with their epicentre located off Aveiro (northern Portugal), typically co-occur with and follow those of Dinophysis acuminata during the upwelling transition (early autumn) as a result of longshore transport. During hotter than average summers, D. acuta blooms also occur in August in the Rías, when they replace D. acuminata. Here we examined a 30-year (1985-2014) time series of D. acuta from samples collected by the same method in the Galician Rías. Our main objective was to identify patterns of distribution and their relation with climate variability, and to explain the exceptional summer blooms of D. acuta in 1989-1990. A dome-shaped relationship was found between summer upwelling intensity and D. acuta blooms; cell maxima were associated with conditions where the balance between upwelling intensity and heating, leading to deepened thermoclines, combined with tidal phase (3 days after neap tides) created windows of opportunity for this species. The application of a generalized additive model based on biological (D. acuta inoculum) and environmental predictors (Cumulative June-August upwelling CUIJJA, average June-August SSTJJA and tidal range) explained more than 70% of the deviance for the exceptional summer blooms of D. acuta, through a combination of moderate (35,000-50,000 m3 s-1 km-1) summer upwelling (CUIJJA), thermal stratification (SSTJJA > 17 °C) and moderate tidal range (~2.5 m), provided D. acuta cells (inoculum) were present in July. There was no evidence of increasing trends in D. acuta bloom frequency/intensity nor a clear relationship with NAO or other long-term climatic cycles. Instead, the exceptional summer blooms of 1989-1990 appeared linked to extreme hydroclimatic anomalies (high positive anomalies in SST and NAO index), which affected most of the European Atlantic coast. © 2015 The Authors. Source

Sonderblohm C.P.,University of Algarve | Pereira J.,Instituto Portugues Do Mar e da Atmosfera IPMA | Erzini K.,University of Algarve
ICES Journal of Marine Science

Dynamic factor analysis was used to explore monthly landings per unit effort (LPUE) series of Octopus vulgaris and environmental variables recorded in the southwest Iberian Peninsula, south Portugal. Despite the large fluctuations in the octopus abundance series, results showed a strong aggregation pattern for the last 3 months of the year, possibly related to the input of new recruits to the fishery. The calculated common trend for the 12 months time-series presented significant correlations with autumn rainfall of the previous year (lag-1), particularly for the October, November, and December series. Other important correlations were found for the Western Mediterranean Oscillation index (lag-1), Ekman transport, summer river run-off (lag-1), horizontal and vertical component of windstress, among others. The main trend describes a moderate steady increase in LPUE during the last 10 years, suggesting that octopus abundance has increased from 1990 to 2010. The strong correlations of the monthly octopus LPUE series, together with the annual life cycle, suggest that after environmentally controlled recruitment, population dynamics is largely fishery driven, resulting in strong seasonality in the landings. © 2014 International Council for the Exploration of the Sea. All rights reserved. Source

Dos Santos A.,Instituto Portugues Do Mar e da Atmosfera IPMA | Hayd L.,State University of Mato Grosso do Sul | Anger K.,Alfred Wegener Institute for Polar and Marine Research

The neotropical species Macrobrachium amazonicum (Heller, 1862) is considered a particularly successful species, showing an extremely wide range of distribution (ca 4.000 km across). Populations assigned to this species live in estuaries along the northern and northeastern coasts of South America as well as in fresh water habitats in the Amazon, Orinoco and Paraná-Paraguay river basins. Following recent comparative studies that showed differential ecological, reproductive, developmental and physiological traits in geographically separated populations from the Amazon delta and the Pantanal region, Brazil, we examined the morphology of adult shrimps from these two regions. Based on significant differences, we conclude that the Pantanal population constitutes a new species, which is described here as Macrobrachium panta-nalense. The main differences between M. amazonicum and the new species have been found in the morphology of the second pereiopod, the telson, and in the color patterns of both males and females. A modification on the key of American species of Macrobrachium is provided to accommodate the new species. Copyright © 2013 Magnolia Press. Source

Gu H.,Third Institute of Oceanography | Liu T.,Third Institute of Oceanography | Vale P.,Instituto Portugues Do Mar e da Atmosfera IPMA | Luo Z.,Third Institute of Oceanography
Harmful Algae

Four Gymnodinium species have previously been reported to produce microreticulate cysts. Worldwide, Gymnodinium catenatum strains are conservative in terms of larger subunit (LSU) rDNA and internal transcribed spacer region (ITS) sequences, but only limited information on the molecular sequences of other species is available. In the present study, we explored the diversity of Gymnodinium by incubating microreticulate cysts collected from the Yellow Sea off China. A total of 18 strains of Gymnodinium, from three species, were established. Two of these were identified as Gymnodinium catenatum and Gymnodinium microreticulatum, and the third was described as a new species, Gymnodinium inusitatum. Motile cells of G. inusitatum are similar to those of Gymnodinium trapeziforme, but they only share 82.52% similarity in LSU sequences. Cysts of G. inusitatum are polygonal in shape, with its microreticulate wall composed of approximately 14 concave sections. G. microreticulatum strains differ from each other at 69 positions (88.00% similarity) in terms of ITS sequences, whereas all G. catenatum strains share identical ITS sequences and belonged to the global populations. Phylogenetic analyses, based on LSU sequences, revealed that Gymnodinium species that produce microreticulate cysts are monophyletic. Nevertheless, the genus as a whole appears to be polyphyletic. Paralytic shellfish toxins (PSTs) were found in all G. catenatum strains tested (dominated by 11-hydroxysulfate benzoate analogs and N-sulfocarmaboyl analogs) but not in any of the G. microreticulatum and G. inusitatum strains. Our results support the premise that cyst morphology is taxonomically informative and is a potential feature for subdividing the genus Gymnodinium. © 2013 Elsevier B.V. Source

Discover hidden collaborations