Environmental Fate and Bioaccumulation of Antibiotic Xenobiotics in Aquatic Ecosystems: Ecotoxicological Risks and Bioremediation Approaches

Introduction: Pharmaceutical antibiotics are ubiquitous emerging contaminants in surface waters due to incomplete removal in wastewater treatment and runoff from aquaculture/agriculture. Reported concentrations span <1 ng/L to tens of µg/L in water and up to hundreds of ng/g in sediment. This study assesses the environmental fate of representative antibiotics in water, sediment, and biota, quantifies bioaccumulation and ecological risk, and explores biological remediation strategies.

Methods: Water, sediment, and aquatic organism samples were collected from effluent-impacted streams and aquaculture sites. Target antibiotics were quantified by LC–MS/MS. Bioaccumulation factors (BCF) were estimated for target compounds in fish/invertebrates, and risk quotients were calculated per EU guidelines. Controlled lab studies tested bioremediation: batch and pilot tests using microbial consortia, algal reactors, and constructed wetlands, monitoring antibiotic removal over time.

Results: All three antibiotic classes were detected in water and sediment (tens–hundreds ng/g) at impacted sites. Fish and invertebrates bioaccumulated drugs: calculated BCFs reached O(10^2). Computational modeling confirmed that sulfonamides have high biomagnification potential, whereas tetracyclines degrade more readily. Ecological RQs were generally <1, but some values approached approx. 0.5–0.6. Sediments acted as long-term reservoirs of antibiotics, posing a risk of remobilization. In pilot treatments, bioremediation removed substantial fractions of pollutants, and algal consortia degraded approx. 77% of sulfamethoxazole (10 ppb spiked) in 7–10 days, and constructed wetland systems have shown 28–100% removal of various antibiotics depending on design.

Conclusions: Aquatic environments are chronically contaminated by antibiotic xenobiotics, leading to measurable bioaccumulation and sub-lethal ecological stress. Although acute risk quotients are moderate, the persistence and trophic transfer of certain antibiotics imply long-term hazards and promotion of AMR. Integrated biological treatments show promise: microbial/plant-based systems can significantly remove antibiotics.