Detecting toxicants in aquatic ecosystems is critical for assessing the impact of pollutants on the environment. Conventional chemical analysis methods are often time-consuming and resource-intensive, and may not fully capture bioavailability or cumulative pollutant effects. Whole-cell biosensors offer a rapid, biologically relevant method for assessing environmental toxicity. Building on the previous generation of our fiber-optic biosensor, this study introduces a second-generation system that improves usability and field readiness while maintaining the core functionality of the original design. The upgraded system incorporates additional features to enhance portability and ease of deployment in remote environments such as an improved, lightproof case as well as a sustainable power supply incorporating an internal power station as well as solar panels. At its core is a photomultiplier tube (PMT) that quantitively detects low-intensity blue light emitted by bioluminescent bacterial bioreporters, that were immobilized within a calcium alginate matrix on fiber-optic tips, in response to toxicants. As a proof of concept, on-site toxicity measurements of water and sediment samples were conducted at potentially contaminated locations across Israel. Preliminary results obtained with the new configuration indicate notable improvements in operational efficiency and ease of deployment compared to earlier prototypes, while retaining its capabilities in detecting various toxicants as revealed by a complementary chemical analysis. This new configuration offers promising potential as a high-throughput versatile tool for on-site environmental toxicity screening.