-The diversity of Pseudo-nitzschia (Bacillariophyceae) and accumulation of the neurotoxin domoic acid (DA) in two types of shellfish; tuberculate cockles (Acanthocardia tuberculata) and sweet clams (Challista chione) was explored in M'diq Bay, Morocco during 2007. The highest abundances of Pseudo-nitzschia were found during the period from March to October, with peaks occurring in May and September. Toxin analysis showed an accumulation of domoic acid in shellfish sampled during spring and autumn. The maximum toxin concentration was 4.9 mg DA g -1 of the whole tissue recorded in sweet clam during spring. Using transmission electron microscopy, thirteen Pseudo-nitzschia species were identified, eight of which are known as producers of domoic acid: P. multistriata, P. cuspidata, P. galaxiae, P. multiseries, P. pseudodelicatissima, P. pungens var. aveirensis, P. calliantha and P. fraudulenta. The five non-toxic species observed were P. subpacifica, P. arenysensis, P. dolorosa, P. subfraudulenta, and P. cf. caciantha.

No abstract

No abstract

No abstract

No abstract

No abstract

The present study aimed at studying ecological interaction between a fish farm cages located in M’diq bay, in western Moroccan Mediterranean coast, and its local environment. It was carried out in 2013 and 2016 through seabed analysis in terms of organic matter and some nutrients parameters such as Nitrogen and Phosphorus, as well as through monitoring macro-fauna assemblages. The results showed recorded values relatively stable in three years’ interval and have a well-integrated fish farming activity within its ecosystem. Sediment was sandy to sandy shelly types and macro-benthic fauna were composed of six groups, Gastropods, Bivalves, Scaphopoda, Amphipods, Nematoda and Polychaeta. Organic matter and Total Organic Carbon were respectively less than 3.2% and 1.87% and very low comparing with others Mediterranean fish farms sites. Estimation of Nitrogen, Phosphorus and Carbon potential releases of M’diq fish farm gave low data related to its production capacity not exceeding 200 tons by year. Influenced with open sea location and high current state, dispersion pattern of these fish farm discharges seemed to play a key role in keeping lower values. ANOVA analysis showed no significant difference between studied parameters in the five sampling stations comparing with the reference station both on geographical and temporal levels (seasons and years).

No abstract