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The article discusses a study on the concentration levels of polychlorinated biphenyls (PCBs), HCB and dichlorodiphenyl trichloroethane (DDT) and derivatives, aldrin, heptachlor and its epoxide in clams, cockles and oysters from the Khnifiss Lagoon ecosystem on the South Atlantic coast of Morocco. Samples of mussels, clams and oysters were chosen as sentinel bivalve species due to their economic interest and conditions of life. The bivalve samples were then freeze-dried and crushed to determine the concentrations of organochlorine pesticides and polychlorinated biphenyl. The study confirms the occurrence of the main compounds of the organochlorine pesticides in Khnifiss Lagoon and cites atmospheric contamination as the possible reason for chlorinated compounds pollution in the lagoon.

The lethal and sublethal effects of the xenoestrogen 4-nonylphenol (NP) were evaluated in the cockle Cerastoderma glaucum. In a 96-h lethality test, bivalves were exposed to 0, 0+ acetone, 0.19, 0.38, 0.75, 1.5 and 3.0mg NP/l. The 96-h LC50 value was 0.3mg NP/l. No mortality was observed at 0.1mg NP/l. The potential estrogenicity of NP was studied in both sexually undifferentiated (resting phase) and differentiated (pre-spawning phase) cockles, exposed for 7 and 14days to 0, 0+ acetone, 0.0125, 0.025, 0.05, and 0.1mg NP/l. Vitellogenin (Vg)-like protein levels were determined in both haemolymph and digestive gland by the alkali-labile phosphate (ALP) assay. In the resting phase, exposure for 7days to 0.1mg NP/l resulted in significant increases in ALP in both haemolymph and digestive gland, compared with controls. A significant increase was also observed in digestive gland of animals exposed to 0.0125mg NP/l-exposed animals. After 14days of exposure, haemolymph ALP levels were significantly increased in exposed animals at all NP concentrations tested, whereas no difference was recorded in digestive gland. In the pre-spawning phase, exposure for 7days to NP significantly increased ALP levels in haemolymph from males exposed at all NP concentrations tested, whereas no significant variations were found in haemolymph from females. NP (0.05 and 0.1mg/l) was also shown to increase ALP concentrations significantly in digestive gland of males, but not in those of females. Likewise, after 14 days’ exposure, ALP levels significantly increased in haemolymph from males only at 0.1mg NP/l. Conversely, NP caused significant increases in ALP levels in digestive gland from both males (at all NP concentrations tested) and females (at 0.025 and 0.1mg NP/l). These results demonstrate that NP induces Vg synthesis in C. glaucum. Interestingly, males were more responsive to NP than females. [Copyright &y& Elsevier]

The in vivo effects of 4-nonylphenol (NP) on functional responses of haemocytes from the cockle Cerastoderma glaucum were investigated after 7 days exposure to sublethal NP concentrations (0, 0+acetone, 0.0125, 0.025, 0.05 and 0.1mg/lNP). Haemocytes from both controls and exposed cockles were collected, and the effects of NP on total haemocyte count (THC) and volume of circulating cells, intracellular superoxide anion () levels, acid phosphatase and lysozyme-like activities in both haemocyte lysate (HL) and cell-free haemolymph (CFH) were evaluated. Exposure of cockles to 0.1mg/lNP significantly increased THC (p <0.05) with respect to controls. Analysis of haemocyte size frequency distribution showed that the haemocyte fraction of about 7–8μm in diameter and 250femtolitres in volume increased markedly in cockles exposed to the highest NP concentration tested. Apoptosis resulting in cell volume reduction in NP-exposed animals cannot be excluded. No statistically significant variation in intracellular levels was observed. Conversely, significant increases (p <0.05) in acid phosphatase activity were observed in CFH from 0.05 and 0.1mg/l NP-exposed animals; no significant differences in enzyme activity were recorded in HL. Lysozyme-like activity also increased significantly in CFH from cockles exposed to 0.05mg/l NP (p <0.05) and 0.1mg/l NP (p <0.001). Instead, lysozyme-like activity decreased significantly (p <0.05) in the HL of animals exposed to 0.05mg/lNP. Our results suggest that NP induces variations in the functional responses of haemocytes of C. glaucum, mainly by reducing cell membrane stability and promoting cell degranulation. [Copyright &y& Elsevier]

Gymnodimine A has been found in mollusks obtained along the whole northern coast of Spain from April 2017 to December 2019. This is the first time that this toxin is detected in mollusks from the Atlantic coast of Europe. The prevalence of the toxin was, in general, low, being detected on average in approximately 6% of the obtained samples (122 out of 1900). The concentrations recorded were also, in general, low, with a median of 1.3 μg kg−1, and a maximum value of 23.93 μg kg−1. The maxima of prevalence and concentration were not geographically coincident, taking place the first at the easternmost part of the sampled area and the second at the westernmost part. In most cases (>94%), gymnodimine A and 13-desmethyl spirolide C were concurrently detected, suggesting that Alexandrium ostenfeldii could be the responsible producer species. The existence of cases in which gymnodimine A was detected alone suggests also that a Karenia species could also be involved. The geographical heterogeneity of the distribution suggests that blooms of the producer species are mostly local. Not all bivalves are equally affected, clams being less affected than mussels, oysters, and razor clams. Due to their relatively low toxicity, and their low prevalence and concentration, it seems that these toxins do not pose an important risk for the mollusk consumers in the area. [Display omitted] • Gymnodimine A is present in mollusks from the Atlantic Coast of Europe. • Gymnodimine A in North Spain has low prevalence and concentration. • 13-desmethyl spirolide C was present in most samples which contained gymnodimine A. • Alexandrium ostenfeldii is the most likely producer of gymnodimine A in the area. • Gymnodimine A had its lowest prevalence in clams and its highest one in oysters. Main findings: Gymnodimine A was found in mollusks for the first time on the Atlantic coast of Europe. It has low concentration and prevalence and seems to be mostly associated to Alexandrium. [ABSTRACT FROM AUTHOR]