Is Microtox R toxicity related to potentially harmful algae proliferation in Mediterranean salt marshes?

Mediterranean salt marshes are ecosystems that are highly influenced by sea changes and freshwater inputs from runoff. In these ecosystems, toxic and non-toxic algae blooms often produce large and unpredictable biomasses of phytoplankton. The Microtox R test has been described as a successful, quick method for detecting toxicity in various phytoplankton taxa. Ourstudy sought to test the efficiency of Microtox R in detecting toxic HAB in Mediterranean salt marshes. The results showed that the Microtox R test was able to detect toxic substances in the particulate matter of several lagoons in the Empordà salt marshes. This Microtox R toxicity coincided with periods when potentially harmful cyanobacteria, dinoflagellates andhaptophytes had a high biomass. The results suggest that potentially harmful phytoplankton cannot be ruled out as a source of Microtox R

Toxic phytoplankton response to warming in two Mediterranean bays of the Ebro Delta

The analysis of the phytoplankton and environmental parameters of the time series in Alfacs and Fangar bays (north western Mediterranean) from 1990 to 2009 shows some trends. There is an increase in the average water column temperature, 0.11, 0.01, 0.80 and 0.23 ºC for spring, summer, fall and winter respectively in Alfacs Bay and 1.76, 0.71, 1.33, 0.89 ºC for spring, summer, fall and winter in Fangar Bay. The trends in phytoplankton populations show a shift in the timing of occurrence of Karlodinium spp. blooms and an increase of the Pseudo-nitzschia spp. abundances. There is a lack of correlation between the average seasonal temperatures and the toxic phytoplankton abundances.

Levels of PSP toxins in bivalves exposed to natural blooms of Alexandrium minutum in Catalan harbours

The development, validation, comparison and evaluation of analytical methods for marine toxins rely on the availability of toxic material. Within the project JACUMAR PSP, our interest is mainly focused on autochthonous bivalve species with the toxic profile of Alexandrium minutum, since this is the principal species involved regionally in PSP outbreaks. Mussels and oysters were exposed during few days in the harbor of Vilanova i la Geltrú, to blooms reaching a maximum A. minutum concentration of 200,000 cells L-1 in 2008, and 40,000 and 800,000 cells L-1, in 2009. Mussels, oysters and clams were exposed to one bloom of 22,000 cells L-1 in the harbor of Cambrils in 2009. In all situations higher toxic levels analyzed by HPLC-FD with postcolumn oxidation were observed in mussels (i.e. 1,200-2,500 μg eq. STX kg-1) than in oysters (i.e. 60-800 μg eq. STX kg-1) exposed to the same bloom. Blooms with higher concentrations of A. minutum did not correspond to higher levels of PSP toxins in bivalves. These differences may be explained by differences in A. minutum population dynamics, toxin production or in the physiological state or behaviour of shellfish. These results confirm that mussels concentrate more PSP toxins from A. minutum than oysters and clams.

Experimental exposure of the blue mussel (Mytilus edulis, L.) to the toxic dinoflagellate Alexandrium fundyense: Histopathology, immune responses, and recovery

Mussels (Mytilus edulis) were exposed to cultures of the toxic dinoflagellate Alexandrium fundyense or the non-toxic alga Rhodomonas sp. to evaluate the effects of the harmful alga on the mussels and to study recovery after discontinuation of the A. fundyense exposure. Mussels were exposed for 9 days to the different algae and then all were fed Rhodomonas sp. for 6 more days. Samples of hemolymph for hemocyte analyses and tissues for histology were collected before the exposure and periodically during exposure and recovery periods. Mussels filtered and ingested both microalgal cultures, producing fecal pellets containing degraded, partially degraded, and intact cells of both algae. Mussels exposed to A. fundyense had an inflammatory response consisting of degranulation and diapedesis of hemocytes into the alimentary canal and, as the exposure continued, hemocyte migration into the connective tissue between the gonadal follicles. Evidence of lipid peroxidation, similar to the detoxification pathway described for various xenobiotics, was found; insoluble lipofuchsin granules formed (ceroidosis), and hemocytes carried the granules to the alimentary canal, thus eliminating putative dinoflagellate toxins in feces. As the number of circulating hemocytes in A. fundyense-exposed mussels became depleted, mussels were immunocompromised, and pathological changes followed, i.e., increased prevalences of ceroidosis and trematodes after 9 days of exposure. Moreover, the total number of pathological changes increased from the beginning of the exposure until the last day (day 9). After 6 days of the exposure, mussels in one of the three tanks exposed to A. fundyense mass spawned; these mussels showed more severe effects of the toxic algae than non-spawning mussels exposed to A. fundyense. No significant differences were found between the two treatments during the recovery period, indicating rapid homeostatic processes in tissues and circulating hemocytes.

Toxic neurofilamentous axonopathies accumulation of neurofilaments and axonal degeneration

A number of neurotoxic chemicals induce accumulation of neurofilaments in axonal swellings that appear at varying distances from the cell body. This pathology is associated with axonal degeneration of different degrees. The clinical manifestation is most commonly that of a mixed motor-sensory peripheral axonopathy with a disto-proximal pattern of progression, as in cases of chronic exposure to n-hexane and carbon disulphide. It has been demonstrated that protein adduct formation is a primary molecular mechanism of toxicity in these axonopathies, but how this mechanism leads to neurofilament accumulation and axonal degeneration remains unclear. Furthermore, little is known regarding the mechanisms of neurofilamentous axonopathy caused by 3,3′-iminodipropionitrile, an experimental toxin that induces proximal axon swelling that is strikingly similar to that found in early amyotrophic lateral sclerosis. Here, we review the available data and main hypotheses regarding the toxic axonopathies and compare them with the current knowledge of the biological basis of neurofilament transport. We also review recent studies addressing the question of how these axonopathies may cause axonal degeneration. Understanding the mechanisms underlying the toxic axonopathies may provide insight into the relationship between neurofilament behaviour and axonal degeneration, hopefully enabling the identification of new targets for therapeutic intervention. Because neurofilament abnormalities are a common feature of many neurodegenerative diseases, advances in this area may have a wider impact beyond toxicological significance

Cyanobacterial diversity and a new Acaryochloris-like symbiont from Bahamian sea-squirts

Symbiotic interactions between ascidians (sea-squirts) and microbes are poorly understood. Here we characterized the cyanobacteria in the tissues of 8 distinct didemnid taxa from shallow-water marine habitats in the Bahamas Islands by sequencing a fragment of the cyanobacterial 16S rRNA gene and the entire 16S-23S rRNA internal transcribed spacer region (ITS) and by examining symbiont morphology with transmission electron (TEM) and confocal microscopy (CM). As described previously for other species, Trididemnum spp. mostly contained symbionts associated with the Prochloron-Synechocystis group. However, sequence analysis of the symbionts in Lissoclinum revealed two unique clades. The first contained a novel cyanobacterial clade, while the second clade was closely associated with Acaryochloris marina. CM revealed the presence of chlorophyll d (chl d) and phycobiliproteins (PBPs) within these symbiont cells, as is characteristic of Acaryochloris species. The presence of symbionts was also observed by TEM inside the tunic of both the adult and larvae of L. fragile, indicating vertical transmission to progeny. Based on molecular phylogenetic and microscopic analyses, Candidatus Acaryochloris bahamiensis nov. sp. is proposed for this symbiotic cyanobacterium. Our results support the hypothesis that photosymbiont communities in ascidians are structured by host phylogeny, but in some cases, also by sampling location.

Characterization and Control Strategies of an Integrated Chemical-Biological System for the Remediation of Toxic Pollutants in Wastewater: A case of study

In a previous work, a hybrid system consisting of an advanced oxidation process (AOP) named Photo-Fenton (Ph-F) and a fixed bed biological treatment operating as a sequencing batch biofilm reactor (SBBR) was started-up and optimized to treat 200 mg·L-1 of 4-chlorophenol (4-CP) as a model compound. In this work, studies of reactor stability and control as well as microbial population determination by molecular biology techniques were carried out to further characterize and control the biological reactor. Results revealed that the integrated system was flexible and even able to overcome toxic shock loads. Oxygen uptake rate (OUR) in situ was shown to be a valid tool to control the SBBR operation, to detect toxic conditions to the biomass, and to assess the recovery of performance. A microbial characterization by 16S rDNA sequence analysis reveals that the biological population was varied, although about 30% of the bacteria belonged to the Wautersia genus.