Monitoring Aquaculture Water Quality: Design of an Early Warning Sensor with Aliivibrio fischeri and Predictive Models

An alternative approach to assess ecotoxicological effects of agrochemical combinations used in Brazilian aquaculture farms

Agrochemicals used for treating and preventing aquaculture diseases are usually present in combination with other compounds, and the toxicity resulting from their chemical interactions presents an important reason to assess the ecotoxicity of compound mixtures in view to better understanding the joint action of chemicals and avoiding their environmental impacts. In this study, we evaluated the acute aquatic ecotoxicity of several compounds used in Brazilian fish farming (Oxytetracycline [OXT], Trichlorfon [TRC], and BioFish® [BIO]), both individually and in binary and ternary mixtures. Initial test concentrations were prepared according to the recommended concentrations for aquaculture application, and from these, a geometric dilution series was tested on two important fresh water quality indicator species, the microcrustacean Daphnia magna and the bacterium Aliivibrio fischeri. At the recommended pond application rate, TRC and BIO applied individually showed toxicity to the tested organisms in terms of the lowest-observed-effect concentration (LOEC), and D. magna was always more sensitive than A. fischeri. For the two test organisms, the results obtained with the binary mixtures showed that the TRC and BIO mixture was more toxic than TRC and OXT, which in turn was more toxic than OXT and BIO. The toxicity from all agrochemicals in the ternary mixture was more than that of the agrochemical combinations in the binary mixtures. Given the results presented in this study, it is evident that the mode of action and availability of the tested compounds undergo changes that increase toxicity when they are present in combination, and therefore, aquaculture wastewater treatment should be adopted to ensure decontamination of agrochemical residues.

Recent Advances of Smart Systems and Internet of Things (IoT) for Aquaponics Automation: A Comprehensive Overview

Aquaponics is an innovative, smart, and sustainable agricultural technology that integrates aquaculture (farming of fish) with hydroponics in growing vegetable crops symbiotically. The correct implementation of aquaponics helps in providing healthy organic foods with low consumption of water and chemical fertilizers. Numerous research attempts have been directed toward real implementations of this technology feasibly and reliably at large commercial scales and adopting it as a new precision technology. For better management of such technology, there is an urgent need to use the Internet of things (IoT) and smart sensing systems for monitoring and controlling all operations involved in the aquaponic systems. Thence, the objective of this article is to comprehensively highlight research endeavors devoted to the utilization of automated, fully operated aquaponic systems, by discussing all related aquaponic parameters aligned with smart automation scenarios and IoT supported by some examples and research results. Furthermore, an attempt to find potential gaps in the literature and future contributions related to automated aquaponics was highlighted. In the scope of the reviewed research works in this article, it is expected that the aquaponics system supported with smart control units will become more profitable, intelligent, accurate, and effective.

Recent methods and biosensors for foodborne pathogen detection in fish: progress and future prospects to sustainable aquaculture systems

The aquaculture industry has advanced toward sustainable recirculating systems, in where parameters of food quality are strictly monitored. Despite that, as in the case of conventional aquaculture practices, the recirculating systems also suffer threats from Aeromonas spp., Vibrio spp., Streptococcus spp., among other foodborne pathogens infecting farmed fish. The aquaculture pathogens are routinely detected by conventional PCR methods or antibody-based tests, with the detection protocols confined to laboratory use. Emerging assay technologies and biosensors recently reported in the literature open new opportunities to the development of sensitive, specific, and portable analytical devices to use in the field. Techniques of DNA/RNA analysis, immunoassays and other nanomolecular technologies have been facing important advances in response time, sensitivity, and enhanced power of discrimination among and within species. Moreover, the recent developments of electrochemical and optical signal transduction have facilitated the incorporation of the innovative assays to practical miniaturized devices. In this work, it is provided a critical review over foodborne pathogen detection by existing and promising methods and biosensors applied to fish samples and extended to other food matrices. While isothermal DNA/RNA amplification methods can be highlighted among the assay methods for their promising analytical performance and suitability for point-of-care testing, the electrochemical transduction provides a way to achieve cost-effective biosensors amenable to use in the aquaculture field. The adoption of new methods and biosensors would constitute a step forward in securing sustainable aquaculture systems.

A fluorimetric nitrite biosensor with polythienothiophene-fullerene thin film detectors for on-site water monitoring

A novel fluorimetric sensor for highly sensitive nitrite detection on the site is presented in this study. The proposed on-chip approach comprises the use of integrated polymer photodetectors to detect light from fluorescence reactions with a diaminofluorescein probe. The detectors were prepared with a heterostructured nanofilm of polythieno[3,4-b]thiophene/benzodithiophene and (6,6)-phenyl-C₇₁-butyric-acid methyl-ester as a photoactive layer. Prior to fluorimetric detection, the quality of the spin-coated photoactive layer was characterized via nano-morphology and current-density measurements. Nitrite assays were conducted on a poly(methyl methacrylate) microchannel chip, to which polythienothiophene-C₇₁ based detectors were aligned. Results of signal-to-noise ratio determination have indicated a detection limit below 0.55 μM, lower than the 0.1 mg L^-1 maximum limit of operation in recirculating aquaculture systems for farming Atlantic salmon Salmo salar. An increase of the nitrite concentration to toxic levels may therefore be possible to detect. The fluorimetric sensor exhibited good linearity over three orders of magnitude and acceptable detection reproducibility, which confirmed its analytical value. Further tests revealed great promise of the integrated biosensor device for detecting nitrite in aquaculture-relevant samples with high precision. The approach reported hereby may provide impetus to in situ analytical tools for monitoring water quality at aquaculture facilities, the food industries or water monitoring stations.