Seasonal variation of biochemical composition of Noah's ark shells (Arca noaeL. 1758) in a Tunisian coastal lagoon in relation to its reproductive cycle and environmental conditions

Abstract

The seasonal changes in biochemical composition of the edible bivalve Arca noae harvested from a Mediterranean coastal lagoon (Bizerte lagoon, Tunisia) were investigated from October 2013 to September 2014. Potential food sources and nutritional quality indices (NQI) were determined by analyzing the fatty acid profiles of their tissues during an annual reproductive cycle. Results showed that A. noae had moisture (73.8–82%) and protein (24.1–58.6% dry weight) as major components, followed by lipid (10.4–28.8% dry weight) and glycogen (4.05–14.6% dry weight). A. noae accumulated lipid and glycogen for gonadal development during both maturation periods (late autumn/late spring–summer) to be used during spawning periods (winter/late summer–early autumn). However, proteins were mainly used to support reproductive allocation and played an important role on the energetic maintenance. Lipid and glycogen were found to be significantly related to temperature, salinity and chlorophyll a (p < 0.05). An increase of condition index (CI) was observed during spring and early summer when both temperature and food supply increased. The total fatty acid (TFA) profile of Ark shells was dominated by polyunsaturated fatty acids (PUFA) (33.8–49.6%), followed by saturated (SFA) (29.1–43.1%) and monounsaturated fatty acids (MUFA) (20.77–28.3%). A. noae soft tissues were also rich in macro-minerals (Na, Ca and Mg). The analysis of fatty acid trophic markers revealed that the diet of A. noae during the year of study was based on mixture food mainly on phytoplankton followed by zooplankton and other sources (bacteria, seagrass and macroalgae). Furthermore, the nutritional quality indices have revealed that A. noae is an excellent source of nutrients and a healthy food for human consumption. These data are useful to the conservation of natural stocks of A. noae and the development of sustainable aquaculture production of this shellfish species in the Bizerte lagoon.

Trace elements and oxidative stress in the Ark shell Arca noae from a Mediterranean coastal lagoon (Bizerte lagoon, Tunisia): are there health risks associated with their consumption?

“…In our previous research, we reported that A. noae body dry weight (BDW) is relatively constant during the first reproductive phase (from October to March), while it increased significantly during the second phase from April to reach its maximum in July indicating a rapid increase in biomass caused by growth of gonadal and somatic tissues (see Ghribi et al 2017). This increase coincided with high food uptake (Chl a) in the lagoon waters and important reserve materials accumulation (Ghribi et al 2018). The use of the gonad index (GI), as a descriptor of the ecophysiological and health status of marine organisms, reflected in part the evolution of the sexual cycle of A. noae in the Bizerte lagoon (Fig.…”

Geographic variation in fatty acid composition and food source of the commercial clam (<em>Venerupis decussata</em>, Linnaeus, 1758), from the Tunisian Coast: Trophic links

“…On the other hand, the fatty acid composition of V. decussata from the Tunisian Coast presented a prevalence of unsaturated fatty acids (UFA) throughout the study sites. According to many investigations, this higher amount of UFA was specific to a healthy marine species (Ghribi et al, 2018). In fact, the PUFA levels in clam tissues reached their highest values, which coincided with an important amount of Chl a and lower T °C.…”

Annual variation of the biochemical composition, energy reserves and physiological indices in Mactra stultorum tissues from the Tunisian coasts

“…In the Mediterranean Sea, mainly in Tunisia, bivalves are considered as a rich food source and a healthy proportionate diet [3,42]. Since, they are known for their nutritious and essential energy reserves (e.g., protein, vitamins and minerals).…”