Seasonal and Spatial Variations in Proximate Composition, Fatty Acid Profiles, and Lipid Nutritional Quality of Meretrix lyrata in Relation to Water-Quality Parameters in the Coastal Ecosystems of Cox’s Bazar, Bangladesh

Abstract

The study was done to address the gap on the seasonal nutritional difference of Meretrix lyrata in Bangladesh. The experiment involved comparison of proximate composition, fatty acid and lipid nutritional indices of the samples at Chowfaldandi and Rejukhal in different seasons and how water-quality parameters affected the values. These findings are relevant due to their baseline data on the nutritional value of lyrata, its potential to be a cheap protein and omega-3 fatty acid source, and the impact that the environment has on the quality of seafoods. The findings will be applicable in food security, ecosystem surveillance and future fisheries or aquaculture in the coastal region of Bangladesh. Temperature, salinity, dissolved oxygen, pH, and turbidity had high seasonality (p < 0.05), and they had a considerable impact on the biochemical composition of the clams. The highest level of protein was found in the post-monsoon in Chowfaldandi (10.60 ± 1.67%) and in Rejukhal in the pre-monsoon (10.67 ± 0.62%), and the lowest level was found in winter in both locations (Chowfaldandi: 8.64 ± 1.27%; Rejukhal: 8.69 ± 0.74%). During the post-monsoon season, protein was strongly positively correlated with turbidity. Conversely, it was weakly correlated with temperature in pre-monsoon and not correlated with turbidity in pre-monsoon in Chowfaldandi and Rejukhal, respectively. Comprehensively, these seasonal variations in protein were not statistically significant (p > 0.05). At Chowfaldandi and Rejukhal, the lipid results ranged between 0.76±0.01% and 1.98±0.62% respectively with weak correlation with temperature and turbidity; the seasonal variations were not significant (p > 0.05). The highest moisture content was found in the monsoon and winter at Chowfaldandi (86.99 ± 1.14%) and Rejukhal (87.28 ± 0.14%), whereas the lowest was found in the pre-monsoon at Chowfaldandi (79.25 ± 3.77%) and the post-monsoon at Rejukhal (80.32 ± 8.06%), with no significant seasonal or spatial variation (p > 0.05). The composition of fatty acids was found to be significantly varying according to season and location (p < 0.05). In monsoon, clam contained the lowest levels of saturated fatty acids (SAFA) of 51.87±3.21% and winter had the highest levels of 51.01±1.39% with palmitic (C16:0), stearic (C18:0), and myristic (C14:0) acids. Peak of palmitic acid (12.43±0.09%) was in pre-monsoon at Chowfaldandi and peak of heneicosanoic acid (C21:0) was in post-monsoon at Rejukhal (37.32±0.86%). MUFA were predominately high in winter (Chowfaldandi: 28.81±2.12%; Rejukhal: xvi 40.42±5.18%), and were mostly dominated by palmitoleic (C16:1n7) and erucic (C22:1n9) acid, and had a negative or weak correlation with temperature and turbidity in pre-monsoon. n-3 PUFA had highest value during the monsoon (Chowfaldandi: 80 The dominating fatty acids were linoleic (C18:2n6), eicosatrienoic (C20:3n6), and arachidonic (C20:4n6), with the highest value of the linoleic acid occurring in monsoon (Chowfaldandi: 79.79±2.12%; Rejukhal: 81.90±0.33%). There were significant differences in lipid nutritional quality indices (atherogenicity AI, and thrombogenicity TI) by season (p < 0.05) with winter having higher levels of saturated and thrombogenic fatty acids. These results indicate that seasonal and spatial changes in environmental factors have a strong impact on the proximate composition, fatty acid profile, and lipid nutritional quality of Meretrix sp., and the environmental conditions are highly valuable in defining its nutritional value and influencing the sustainable management practices.