Experimental aquaculture systems

The absence of continuous water exchange and thus the decoupling of environmental influences in closed recirculation systems allows aquatic organisms to be produced with minimal impact on the surrounding ecosystems, as hardly any dissolved nutrients are released into the receiving waters. However, with reuse rates of up to 99% of water, this leads to accumulating metabolic end products, nutrients and minerals in the farming system. The higher the water reuse rate, the higher the demands on and challenges for the water treatment technology used.

In the working group, research is being conducted on the type of accumulating substances as well as on increasing the efficiency of the filter technology from the point of view of filter performance, but also energy consumption.

In order to design sustainable and future-oriented aquacultures, the concept of integrated multitrophic aquaculture, IMTA for short, is being researched at Fraunhofer IMTE. In an IMTA, not only fish but also other aquatic organisms such as algae, mussels or worms are cultivated in the same water cycle or body. Following nature's example, an artificial ecosystem is created in which all organisms benefit from each other: Algae, mussels and worms use the nutrients that are introduced into the water via the fish to grow and at the same time biologically purify the water again. This minimises the nutrient load in the wastewater and at the same time produces more usable biomass.

This concept can be implemented in the sea and on land, both forms bringing their opportunities and challenges. On land, water quality needs to be monitored and controlled more closely, but through this control, production can be optimised at the same time. The optimisation of energy flows also plays a major role. In the open sea, the focus is primarily on not burdening the surrounding ecosystem, so the individual components must be precisely coordinated.

In a land-based IMTA at the Lübeck site, various organisms are being tested for use in such plants on a semi-industrial scale and the interaction between these organisms is being researched. Among other things, work is being done with sea bass and salmon, various indigenous macroalgae species and sea worms. This research is intended to pave the way for the IMTA concept in industry and provides valuable information for the cultivation of new species in aquacultures.  

In order to meet the challenges of our time, it is critical to develop new resources. The diversity of macroalgae species on our coasts is great, with a multitude of applications, but they are still little used in Europe. They are not only interesting as a protein-rich and healthy food, but can also be used as a raw material for bioenergy or bioplastics, for example. Various extracts from macroalgae can be used as biostimulants or are used in cosmetic and pharmaceutical products. Macroalgae can also be used as animal feed and have positive effects on animal health.

The Fraunhofer IMTE is working on making this wide range of possible applications really usable. To this end, the propagation and cultivation of different species is being optimised; there are still many challenges to be overcome here due to the complex reproductive biology. Cultivation in different systems is also being considered, for example, algae are being grown on ropes in order to grow them in the sea, but various land-based systems are also being developed and tested. Furthermore, new species are evaluated and tested in order to develop new, valuable species for aquaculture.