Study of strandings of the jellyfish Pelagia noctiluca in the Mediterranean coastline of Tetouan (NW of the Morocco)

Trabajo presentado en el 2nd Scientific Workshop PERSEUS, celebrado en Marrakesh del 2 al 4 de diciembre de 2014.For a decade, we noticed outbreaks of jellyfish strandings in the coastline of Tetouan especially during heat waves. To examine factors that may be responsible for the stranding of the jellyfish Pelagia noctiluca (Forsskål, 1775) in the coastline of Tetouan (occidental Mediterranean part of Morocco), a monthly monitoring was done at 2 sites (M'diq and Martil) in the years 2011 and 2012. In this study the appearance of these organisms is studied in relation with the tidal currents, wind currents (East wind), weather conditions of the area and physic-chemical parameters of seawater. The appearance of this jellyfish began in June (22.1° C) and reached the maximum of abundance or density in September (24.7° C) to disappear in October. This density fluctuation is correlated with changes in ambient temperature. Analysis of the structure of the population size (umbrella diameter) of the jellyfish shows a size range between 10 mm and 90 mm and an average of 49 mm. Other studies have also observed that the outbreak of the Medusa seems to be related to warm temperatures. Nevertheless, the different processes that are involved in the appearance of jellyfish in a specific coastal area operate at diverse time and spatial scales, which demand to take into account an wide perspective in order to analyze their population dynamics.N

Contamination and depuration of Paralytic Shellfish Poisoning by Acanthocardia tuberculata cockles and Callista chione clams in Moroccan waters

International audienceThis study of Gymnodinium catenatum was conducted across two sampling stations; M'diq bay and Oued Laou estuary during the period from July 2007 to May 2009. Gymnodinium catenatum blooms occurred after a rainfall event in autumn and early winter. Statically analyses showed a positive correlation with rainfall. During January 2008, the G. catenatum bloom resulted in contamination of tuberculate cockles and sweet clam by Paralytic Shellfish Poisoning (PSP) toxins. In the Oued Laou estuary, the levels of these toxins in shellfish went beyond the normative threshold for consumption of shellfish, (80 µg SXTeq. /100g of meat) and reached (710 ± 82.07) and (198 ± 6.56) µg SXTeq. /100g of meat in cockles and sweet clam respectively. In M'diq bay, concentrations of PSP toxins in the meat of these two shellfish were lower (256.57 ± 12.22 µg SXTeq. /100g and 80.66 ± 8.14 µg SXTeq. /100g of meat in tuberculate cockles and sweet clam respectively. An experimental test of depuration of tuberculate cockles and sweet clam contaminated by the PSP toxins was conducted in laboratory conditions in the first week of January 2008. The results showed partial and progressive elimination of PSP toxins in two shellfish species over time. In the tuberculate cockle, the elimination of PSP appears to be slower compared with the sweet clam; it took 120 days to reach levels of 80 µg SXTeq. /100g of meat, on the other hand only 3 days were needed to reach this safe concentration in the sweet clam