Interaction and impact of cultivated macroalgae and growing structures on faunal community assemblages and surrounding ecosystems
Creators: name: Fariñas-Franco, Jose M.
name: Jansen, Henrice
name: Santamaria Sansegundo, Jorge
name: Coca Tagarro, Ines
name: Nash, Steven
name: Nielsen, Daniele
name: Adu-Gyamfi, Anthony
name: Kennedy, Toni
name: Fort, Antoine
name: Sulpice, Ronan
Publisher: name: Zenodo
Year: 2021
Subjects: seaweed
aquaculture
environmental impacts
biodiversity
sustainability
algae
kelp

description: GENIALG aimed to study the possibilities for upscaling and streamlining seaweed production as a way not only to satisfy growing demand from industry but also to promote local economic activity and develop seaweed aquaculture in an efficient and environmentally sustainable way. This reports provides a comprehensive assessment of the impact of seaweed farms on coastal<br> ecosystems using medium sized farms in the southwest coast of Ireland (Ventry Harbour, Co.Kerry) and The Netherlands (Eastern Scheldt) growing sugar kelp (<em>Saccharina lattisima</em>) as case studies. This report presents the results of those surveys and discusses the implications for the management of current seaweed aquaculture licenses. No negative impacts were detected on abiotic seafloor condition other than seasonal variability in organic matter linked to primary production and within site spatial variability in both mean grain size, kurtosis, and skewness. Observational data from both test farms indicates that seaweed farming did not exert, at the scales and under the conditions studied, a negative influence on its surrounding environment but rather provided positive ecosystem interactions. Reduced water flow and turbidity within the seaweed farm was likely responsible for higher photosynthetically active irradiance values recorded under the longlines compared to distant controls and were linked to significantly higher seagrass shoot abundance and coverage under the farm. The role of seaweed farms coupled with their de-facto role as exclusion zones providing protection against physical disturbance from anchoring or bottom trawling is evidence of their positive effect on the environment, facilitating the conservation of benthic habitats of high conservation value such as seagrass. Biodiversity within cultivated seaweed was relatively high and similar (e.g. species numbers) to that recorded in natural kelp beds. The results showed no significant differences in the number of taxa and heir abundances between the two cultivated kelp species studied. Seeded droppers yielded significantly higher abundance of macroinvertebrates, but similar number of taxa, compared to<br> unseeded rope droppers used as controls, attracting a community dominated by amphipods <em>Jassa</em> spp.and the non-native Japanese ghost shrimp <em>Caprella mutica</em> in both the Irish and Dutch sites. In addition, both farms provided evidence for their use as nurseries by fish of commercial importance such as pollock <em>Pollachius pollachius.</em> The findings represent evidence of the role of seaweed farming in the sustainable development of coastal economies and communities, maintaining healthy ecosystems which in turn provide valuable ecosystem services. Maximising this role and ecosystem services should be incorporated in management strategies and be considered in the site selection and licensing<br> process.