Development of potential yield loss indicators to assess the effect of seaweed farming on fish landings

Nils Préat, Marleen De Troch, Sonja van Leeuwen, Sue Ellen Taelman, Steven De Meester, Florent Allais, Jo Dewulf
2018 Algal Research  
In recent years, several indicators have been proposed to assess the effect of human activities on ecosystems provisioning capacity. Some of these methods focus on the Net Primary Production (NPP) available for ecosystem functioning through the comparison between the Human Appropriated Net Primary Production (HANPP) and the ecosystem's initial NPP at a given reference year. While some approaches have been proposed for marine ecosystems, most of the HANPP studies focus on terrestrial systems.
more » ... s study highlights the relation between the HANPP methods and the production of natural resources in marine ecosystems. The linkage between current overfishing and future fish provisioning (ecosystem service) is well known. However, less studied before, is the relation between seaweed aquaculture and fish provisioning through the marine food web. Seaweed growth requires nutrients and light that will consequently be no longer available for natural phytoplankton production. As seaweed is periodically harvested, a fraction of the ecosystem's NPP (HANPP) is no longer available for ecosystem production. The HANPP of aquaculture reduces the ecosystem carrying capacity and thus affects commercial fish stocks. Therefore, an integrative approach is proposed in this study to assess the potential effect of seaweed farming on fish landings in the Greater North Sea. Three indicators are proposed to assess the Lost Potential Yield (LPY) in fish landings: LPY B , LPY V and LPY E , accounting respectively for reduction in biomass, monetary value and eco-exergy. For these three aspects, the LPY results remains smaller than the seaweed production, meaning that the overall natural resources balance for seaweed farming is positive. Sea to grow the sugar kelp Saccharina latissima (Linneaus) (Laminariales, Phaeophyceae), a brown seaweed widely distributed in the European Atlantic [6] [7] [8] . The kelp is found on subtidal rocky substrates and is composed of a large frond, a stipe and a holdfast. Nevertheless, the large-scale cultivation of seaweed affects the properties of the surrounding ecosystem by shading [6], artificial reef creation [9] and nutrients uptake [3, 4] . Even in the eutrophic coastal areas, the phytoplankton productivity is limited by nutrients availability during the growth season, when light is not a constraint for growth [10] . Therefore, seaweed farming without the addition of nutrients is expected to reduce the magnitude of phytoplankton blooms in spring and summer. In other words, the production of seaweed biomass replaces a fraction of the phytoplankton biomass. While phytoplankton productivity has been proven to affect fisheries yield [11] [12] [13] , largehttps://doi.
doi:10.1016/j.algal.2018.08.030 fatcat:py7yk5irzjbvhe276idxszktgu