The ecosystem engineer Crassostrea gigas affects tidal flat morphology beyond the boundary of their reef structures
Walles, B. ; Salvador de Paiva, J. ; Prooijen, B. van; Ysebaert, T. ; Smaal, A.C. - \ 2015
Estuaries and coasts 38 (2015)3. - ISSN 1559-2723 - p. 941 - 950.
wadden sea - sediment dynamics - pacific oysters - native mussels - habitat - estuary - stabilization - enhancement - communities - adaptation
Ecosystem engineers that inhabit coastal and estuarine environments, such as reef building oysters, do not only stabilise the sediment within their reefs, but their influence might also extend far outside their reefs, affecting tidal flat morphology and protecting the surrounding soft-sediment environment against erosion. However, quantitative information is largely missing, and the spatially extended ecosystem engineering effects on the surrounding soft-sediment largely unstudied. To quantify this, we measured elevations around eleven natural Crassostrea gigas reefs occurring on tidal flats in the Oosterschelde estuary (the Netherlands). These tidal flats experience strong erosion as a consequence of human interventions in the system. Various reef sizes were chosen to test the proportional effects of reefs on tidal flat morphology. Measurements were used to create 3-dimensional surface maps to obtain properties of the reefs and the surrounding soft-sediment environment. The area of the oyster reefs ranged from 2 to 1,908 m2. Reef length varied between 1 and 61 m, reef width between 1 and 45 m, and reef height between 0.20 and 1.08 m. Reefs varied in shape, going from round shape structures to more elongated ones. We observed elevated areas (>5 cm elevation from the background intertidal slope) on the lee side of all reefs, caused by the interaction between the reef’s structure and locally prevailing wave conditions. The elevated area (i.e. the spatially extended ecosystem engineering effect) affected by the reef was of the same order of magnitude as the reef area. The elevated area was related to reef properties such as reef length, width, and height. Reef length, however, appeared to be the best predictor. These findings contribute to management solutions for coastal adaptation and protection. Our study clearly showed that oyster reefs not only protect the tidal flat under their footprint, but as well an area beyond the boundary of the reef
Microcell parasites of molluscs: introduction to DAO special 7
Carnegie, R.B. ; Engelsma, M.Y. - \ 2014
Diseases of Aquatic Organisms 110 (2014)1-2. - ISSN 0177-5103 - p. 1 - 4.
oyster ostrea-edulis - denman island disease - n. sp haplosporidia - mikrocytos-mackini - bonamia-ostreae - flat oyster - crassostrea-gigas - causative agent - pacific oysters - exitiosa
First discovered decades ago, microcell protistan parasites of the genera Bonamia and Mikrocytos remain relevant today for their economic impacts on growing molluscan aquaculture industries and fisheries. Bonamia parasites have received more attention over the years in part because they are more widespread and thus of wider concern, but there has been renewed interest in Mikrocytos recently with the generation of important new findings. Among these has been the surprising observation that Mikrocytos has phylogenetic affinities to the Rhizaria, which includes the haplosporidian protists and the genus Bonamia. This Diseases of Aquatic Organisms Special, emerging from the 5th Meeting of the Microcell Working Group held at the Central Veterinary Institute, Lelystad, the Netherlands, in February 2012, presents new insights into Mikrocytos and Bonamia diversity, distributions, diagnostics, ultrastructure, and infection dynamics, and captures major developments in the field since the last review of these genera in 2004
Bivalve aquaculture transfers in Atlantic Europe. Part B: Environmental impacts of transfer activities
Brenner, M. ; Fraser, D. ; Nieuwenhove, K. van; Kamermans, P. - \ 2014
Ocean & Coastal Management 89 (2014). - ISSN 0964-5691 - p. 139 - 146.
mussel mytilus-edulis - mytilicola-intestinalis steuer - necrosis virus ipnv - cerastoderma-edule - crassostrea-gigas - polydora-ciliata - marteilia-refringens - mikrocytos-mackini - pacific oysters - ostrea-edulis
For centuries human populations have moved live shellfish around the world for consumption or aquaculture purposes; being relayed from their area of origin for growout or sale. This is in contrast to the inadvertent anthropogenic spreading of species via e.g. ballast waters. There are inherent risks associated with transfer of shellfish including introducing of alien species, diseases, pests, bacteria and viruses associated with the translocated species in addition to the potential impact on genetic integrity and biodiversity of local stocks. Many examples of severe ecological impacts have been documented worldwide owing to the intentional or unintentional translocation of animals. It is therefore important to develop risk reduction methods which have not yet been documented to be incorporated into current fish health or environmental legislation. This part of the study describes the impacts of transfer activities of cultured bivalve shellfish along the European Atlantic coast; identifies hitch hiker species, fouling organisms or infectious agents which can be translocated with a target species. Further, the study highlights the need for thorough, standard risk reduction measures designed to minimise the impact on ecosystems worldwide. In a companion paper details of actual transfer activities in Atlantic Europe are presented and all levels of legislation dealing with transfer activities on a global, regional and national scale are carefully reviewed.