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Von Waldegge T.H.,Institute for Marine Resources GmbH Imare | Von Waldegge T.H.,Alfred Wegener Institute for Polar and Marine Research | Schnars H.,Fraunhofer Institute for Wind Energy and Energy System Technology
European Wind Energy Conference and Exhibition 2010, EWEC 2010

Biofouling constitutes a problem for the technical reliability of offshore farms, because of corrosion, damages by boring organisms and increased frictional drag by waves. It is in debate if lab tests and single-site deployment fulfill the requirements to forecast fouling and corrosion at future offshore wind farms. One way to increase evidence might derive from the greater number in test sites. In order to contribute to this discussion, 14 products used in the marine energy industry as coating or adhesive were deployed for long-term exposure at four test sites in the North Sea. Focusing on the first 6 months of deployment, it was evident that the mussel-aquaculture of Mytilus edulis influenced the fouling community at Wilhelmshaven located in the Jade estuary. These site specific communities showed the deterioration potential indicated by increasing weight load (up to 375%). Furthermore surface damages, indentions and sub-surface migration in a continuum with a physical displacement up to the removal of materials due to biofouling could be detected within the first six months. The site lighthouse "Alte Weser" exhibiting the highest wave force was also affected by macrofouling. Sylt was influenced by highly abundances of the pacific oysters (Crassostrea gigas). The biofouling community of the samples at Helgoland was dominated by biofilms. The results obtained show that the matrix of test sites chosen was suitable to increase the variability of fouling communities and therefore provide options to model biofouling at offshore sites where new hard substrates will be placed to substrate-free environments in future. The variability in succession helps to continue the study regarding the deterioration potential of fouling and corrosion. Source

Beltran-Gutierrez M.,Leibniz Center for Tropical Marine Ecology | Beltran-Gutierrez M.,University of Bremen | Ferse S.C.,Leibniz Center for Tropical Marine Ecology | Kunzmann A.,Leibniz Center for Tropical Marine Ecology | And 5 more authors.
Aquaculture Research

Commercially valuable sea cucumbers are potential co-culture species in tropical lagoon environments, where they may be integrated into established aquaculture areas used for seaweed farming. In the current study, wild-caught juvenile sea cucumbers, Holothuria scabra, and red seaweed Kappaphycus striatum were co-cultured on Zanzibar, United Republic of Tanzania. Sea cucumbers (97 g ± 31 SD, n = 52) were cultured in mesh enclosures at initial cage stocking densities of 124 ± 21 SD and 218 ± 16 SD g m-2 under seaweed culture lines. Over 83 days, individual growth rate (1.6 g d-1 ± 0.2 SD) of sea cucumbers at low stocking density was significantly higher (χ2 = 8.292, d.f. = 1, P = 0.004) than at high-stocking density (0.9 g d-1 ± 0.1 SD). Seaweed individual growth rates [6.27 (±0.3 SE) g d-1] were highest in co-culture with sea cucumber at low density but did not differ significantly from high sea cucumber density or seaweed monoculture treatments (χ2 = 3.0885, d.f. = 2, P = 0.2135). Seaweed growth varied significantly (χ2 = 35.6, d.f. = 2, P < 0.0001) with sampling period, with the final sampling period resulting in the highest growth rate. Growth performance for seaweed and sea cucumbers (χ2 = 3.089, d.f. = 2, P = 0.21 and χ2 = 0.08, d.f. = 1, P = 0.777 respectively), did not differ significantly between monoculture and co-culture treatments, yet growth in co-culture was comparable with that reported for existing commercial monoculture. Results indicate H. scabra is a highly viable candidate species for lagoon co-culture with seaweed. Co-culture offers a more efficient use of limited coastal space over monoculture and is recommended as a potential coastal livelihood option for lagoon farmers in tropical regions. © 2016 John Wiley & Sons Ltd. Source

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