Seagrass meadows improve inflowing water quality in aquaculture ponds

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By Milthon Lujan

Portugal – This new study published in the journal Aquaculture and led by our researchers Carmen Santos and Rui Santos from the ALGAE research group showed that seagrass-dominated water reservoir contributed to improving the quality of the inflowing water in an aquaculture system through the provision of three ecosystem services: water filtration, regulation of the dissolved oxygen in the water, and bacterial control. This study is part of the RIAVALUE project and was conducted in partnership with the Portuguese Institute for Sea and Atmosphere (IPMA), in the framework of their project DIVERSIAQUA – Diversification, Innovation and Development of Aquaculture in Portugal. 

How to make water quality in aquaculture systems less expensive?


Water quality is the most important factor affecting the health and development of farmed fish in aquaculture production systems. Water quality can be defined by a range of physical, chemical and biological parameters that affect the survival, reproduction, growth and welfare of cultivated fish. Aquaculture aims to keep these parameters at an optimum level to get a high fish production at low costs. However, water quality control and maintenance may involve expensive solutions that require high investments in water treatment processes.

As a way to overcome these challenges, aquaculture research is constantly looking for new solutions to increase yield per unit of water consumption. Nature-based solutions are increasingly growing to address environmental, social and economic challenges through the services provided by ecosystems, from which aquaculture systems could benefit. Based on services provide by seagrass meadows, marine plants that are well-acknowledge for their role in water purification, our researchers hypothesised that the quality of the inflowing water to aquaculture ponds can be naturally improved if it is previously channelled through reservoirs colonised by seagrass meadows.

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Advantages of using seagrass to improve water quality in aquaculture systems

The study was conducted at the Aquaculture Research Station from the Institute for the Sea and Atmosphere (EPPO-IPMA), in the Natural Park of Ria Formosa. The station’s water reservoir extends over 1.45 ha and is filled with water from the Ria Formosa, which also supplies other tanks, where several species of fish and bivalves are cultured.

The reservoir is naturally covered with seagrass, mostly by the species Cymodocea nodosa. In this study, our researchers showed that these seagrasses act as biofilters, retaining high quantities of suspended solids and nutrients from the seawater, making the water clearer and cleaner. The removal of these particles from the water is very important for aquaculture production because suspended solids can cause sub-lethal stress in fish over long periods of exposure and can be associated with the appearance of parasites that cause serious diseases in these animals. Furthermore, researchers have a shown that seagrasses can contribute to reducing the levels of pathogenic bacteria in the water and that seagrass oxygenate the system during the day, keeping it above the minimum oxygen requirements for the optimal growth of farmed fish, even during the night.

Seagrass meadows as a natural solution in water treatment in aquaculture


The findings of our researchers showed that the presence of seagrass in the water reservoirs of aquaculture systems contribute to improve the quality of the inflowing water in the aquaculture tanks by providing three services: water filtration, oxygen regulation and bacterial control. Seagrass meadows could, therefore, be used as a nature-based solution to help improve water quality in aquaculture ponds. This solution decreases the costs of water treatments necessary to attain the water quality requirements for fish growth.

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Carmen B. de los Santos, Irene Olivé, Márcio Moreira, André Silva, Cátia Freitas, Ravi Araújo Luna, Hugo Quental-Ferreira, Márcio Martins, Monya M. Costa, João Silva, Maria Emilia Cunha, Florbela Soares, Pedro Pousão-Ferreira, Rui Santos, Seagrass meadows improve inflowing water quality in aquaculture ponds, Aquaculture, Volume 528,
2020, https://doi.org/10.1016/j.aquaculture.2020.735502 

Source: CCMAR-UAlg

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