Scientific research methodology applied to aquaponics

The following case studies illustrate some of the different kinds of methodologies that can be used for research relating to aquaponics. The first case study is an example of social science research conducted using a questionnaire. A questionnaire is a tool for collecting and recording information about a particular issue of interest in a standardized manner. The information from questionnaires tends to fall into two broad categories – facts and opinions; very often they include questions about both. The questions may be unstructured or structured or, as in the case study below, a combination of both. Unstructured questions ask respondents to provide a response in their own words, while structured questions ask respondents to select an answer from a given set of choices. Structured questionnaires are usually associated with quantitative research, i.e. research that is concerned with numbers (how many? how often? how satisfied?). The responses to individual questions in a structured questionnaire may be aggregated and used for statistical analysis (Nayak & Singh 2015).

Questionnaires are one of the most affordable ways of gathering quantitative data. Online surveys in particular can have a very low cost and a generous reach, and the results can be analysed quickly and easily to highlight trends in the data. However, there are a number of drawbacks to using questionnaires. While every researcher hopes for conscientious responses, there is no way of knowing whether the respondent has really thought the question through before answering. At times, answers will be chosen before fully reading the question or the potential answers, and sometimes respondents will skip through questions, or split-second choices may be made. All of these will affect the validity of the data collected. While questionnaires may reveal patterns and trends in the data, they do not permit an understanding of their causes.

The second case study is an example of social science research using a comparative case study approach and semi-structured interviews to generate qualitative data.

Comparative case studies such as this involve the analysis and synthesis of the similarities, differences and patterns across two or more cases that share a common focus or goal. Given the focus on generating a good understanding of the cases and case context, methods such as fieldwork visits, observation, interviews and document analysis often dominate among the various data collection methods employed. Comparative case studies may incorporate both qualitative and quantitative data, and while they may be time consuming, they can generate rich detail about the context and features of two or more instances of specific phenomena.

The field of aquaponics is quite new, with the first scientific paper specifically using the term appearing in an impact journal in 2004⁴. Many advancements had been made before that, namely by James Rakocy and his group (University of the Virgin Islands) but their publications are more demonstrative and less experimental. According to the Web of Science, more than 60 peer-reviewed papers have been published on aquaponics since 2004, but many articles concentrate more on promoting the potential of aquaponics than on completing scientific trials per se. Part of the problem stems from having enough replicates and establishing proper control groups. It is usually quite difficult and time consuming to set up an aquaponic system, with its filter, bacteria, fish, and plants, let alone setting up several units or replicas per treatment. In feed trials in aquaculture, for example, it is common to have at least 3 replicas per treatment, each experimental unit usually being one tank, not the individual fish. That would mean, for example, were we to compare the effects of adding garlic extract to feed, we would need three tanks of fish to which we add garlic feed and three more tanks to which we add control feed. To do something similar using aquaponics is more complex. For example, if we want to compare the effect of water pH on fish welfare and lettuce growth, we would need six separate aquaponic units, three of which were at a specific pH and another three at another pH level, and all six units would need to have fish and lettuce in the same stocking densities. Thus, the cost of each experiment is higher than for feed trials, and the list of things that could possibly go wrong is also much higher. For this reason, when looking at the literature, we normally see very few or no replicates, or two replicates per treatment at the most.

⁴ Tokuyama, T., Mine, A., Kamiyama, K., Yabe, R., Satoh, K., Matsumoto, H., Takahashi, R.& Itonaga, K. 2004. Nitrosomonas communis strain YNSRA, an ammonia-oxidizing bacterium, isolated from the reed rhizoplane in an aquaponics plant. Journal of Bioscience and Bioengineering 98 (4), 309-312.

The third case study is an example of an experimental research methodology. The purpose of experimental research design is to enable the researcher to credibly establish a cause-and-effect relationship. An experiment is a test under controlled conditions that is carried out in order to support, refute, or validate a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular variable is manipulated. Experiments vary greatly in goal and scale, but they always rely on a repeatable procedure and logical analysis of the results. The research methodology is therefore explained in great detail in order to enable other researchers to repeat the experiment and thereby validate, or falsify, its results.

Copyright © Partners of the Aqu@teach Project. Aqu@teach is an Erasmus+ Strategic Partnership in Higher Education (2017-2020) led by the University of Greenwich, in collaboration with the Zurich University of Applied Sciences (Switzerland), the Technical University of Madrid (Spain), the University of Ljubljana and the Biotechnical Centre Naklo (Slovenia).