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Desorption and bioaccumulation of Cd, Zn, and Pb were studied using naturally contaminated sediment from a brackish water pond in the Sunderban Biosphere Reserve in India. Pattern of desorption of the metals from the sediment and bioaccumulation in fingerlings of the teleost Oreochromis mossambicus and postlarvae of the shrimp Penaeus monodon were studied as a function of salinity and loading of detritus of a mangrove plant. Effects of both salinity and loading of detritus on bioaccumulation of the metals were studied under two conditions: either the animals were allowed free access to the sediment or access was denied. Ninety-six hour experiments showed that desorption of Cd and Pb from sediment into water increased with salinity of the medium while desorption of Zn decreased. Salinity of the medium also had a significant effect on the bioaccumulation of metals by fish; Cd and Pb accumulation decreased in saline medium while the accumulation of Zn increased. Conditions of access to sediment had no effect on the bioaccumulation of metals by fish; effect of interaction between salinity and access condition was also insignificant. The access conditions, however, significantly influenced accumulation of metal by the shrimp postlarvae. The effect of interaction between salinity and access condition was insignificant in influencing the bioaccumulation of all metals except Zn. The accumulation of Zn increased as a function of the salinity of the medium when shrimp postlarvae were allowed access to the sediment. Desorption of metals from sediment to water were below detection limits when detritus of a mangrove plant was added to the medium. Both the level of detritus and the conditions of access influenced accumulation of metals by fish, but the effect of interaction between the two factors were found to be insignificant. Shrimp postlarvae showed net accumulation only of Pb in the presence of detritus and the accumulation of Pb increased when the larvae were separated from the sediment. The results are important in understanding the mobility of metals between solid and aqueous phases in brackish water environments that experience periodic fluctuations in salinity and fluxes of organic load in the form of mangrove detritus. Wirkungen von Salinität und Mangrove-Detritus auf die Desorption von Metallen aus dem Sediment eines Brackwasserteiches und ihre Bioakkumulation in Fisch und Garnele

In aquatic systems, recycling of phosphorus (P) is strongly influenced by microbial metabolic responses. This study was designed to look at the generation of P (as soluble-reactive phosphate (SRP)) from organic P-enriched sediments by benthic sulfur chemolithoautotrophs. The study revealed that microbial density was greater in organic P-enriched sediments when compared to sediments without added organic P and the presence of organic P significantly influenced mobilization of SRP from sediment. Generation of SRP by sediment microbes was cumulative, dependent on time. The results indicated dissolved sulfide (S 2À ) to be necessary for initiation of the metabolism-related mobilization of P: there was no statistically significant effect of variations in ambient concentrations of sulfide (S 2À ). The results elucidate possible outcomes of addition of organic P in aquatic ecosystems.

The present-day inclination towards increased application of pesticides derived from natural sources is not without its own hazards. Such pesticides are indubitably less harmful compared to the newer classes of low persistence organophosphates; however, these pesticides may be hydrolyzed to yield secondary products which often exhibit significantly different toxicity. Additionally, studies show that the inert materials used in formulation can exhibit significant toxicity on their own. The toxicity of secondary products and inert materials are largely unknown since these molecules are largely uncharacterized. Azadirachtin is such a candidate pesticide. It is derived from the neem tree Azadirachta indica, and it ticks all the above boxes. In its pure form, formulation and crude extracts, it can generate ecotoxicological effects ranging from behavioural anomalies and physiological imbalances to growth suppression. Authors at various times have pointed out the ability of azadirachtin (or that of its metabolites’/break-down products’) to cause specific, documentable effects on growth and reproduction of non-target fauna. Since extensive reports are available on the toxicology of azadirachtin to terrestrial beneficial fauna like bees and earthworms, this review aims to present a coherent picture of the effects of azadirachtin on non-target aquatic organisms through a documentation of relevant reports published during the last three decades. It is hoped that this compilation will help sensitize public opinion about the erroneous supposition that pesticides derived from natural sources are not innately harmful to non-target biota.

Protozoan ectoparasites pose a significant threat to the health and survival of fish populations, particularly during their vulnerable early life stages. In this study, an intensive icthyoparasitological survey was conducted in Murshidabad, India, with the aim of investigating the presence and prevalence of trichodinid ciliophorans, specifically Tripartiella bulbosa (Davis 1947), on fingerlings of Labeo rohita (Hamilton 1822). Fingerlings of Labeo rohita were sampled from multiple sites within West Bengal. The gills of the fingerlings were carefully examined, and the presence of Tripartiella bulbosa was recorded. The overall prevalence rate of Tripartiella bulbosa infestation was found to be 65.67%. Notably, the highest prevalence of infestation was observed during the winter season during a study in the year 2022, indicating a seasonal pattern of occurrence for this ciliate ectoparasite. The findings of this study provide valuable insights into the prevalence and seasonal patterns of Tripartiella bulbosa infestation in Labeo rohita fingerlings in West Bengal. This information can serve as a basis for developing effective strategies for the prevention, control, and management of trichodinid ciliate ectoparasites in aquaculture systems. Further research is warranted to investigate the impact of these ectoparasites on fish health and to explore potential treatment and mitigation measures for their control.