Improving Sweden's oysters
Oyster farming is a relatively new industry in Sweden. Therefore, the LARVDEVOPTI (Larval quality in oyster hatcheries: Effects of ocean acidification, temperature change and food availability on reproductive success and survival of the European flat oyster) project was established to support development of the aquaculture industry for O. edulis. Researchers investigated the causes of instability in broodstock conditioning and larval development. They also optimised conditions in a commercial-scale hatchery and identified suitable coastal sites for rearing O. edulis until they reach marketable size. Studies of environmental stressors provide important information regarding the best conditions for growth and survival during the vulnerable early stage of the oyster's life cycle. Many of the problems associated with new hatcheries are the result of poor seasonal water quality. Results indicated that the high mortality rates observed in Swedish commercial hatcheries were due to the fluctuating pH of the seawater intake. Other factors responsible for high mortality rates included toxic metabolites and bacterial pathogens from the breakdown of plankton blooms related to highly eutrophic conditions in the Baltic Sea. Modifications were carried out at the hatchery to treat all intake water for low pH, as any drop in pH below 7.8 can compromise development of the oyster larvae. The presence of bacterial pathogens was linked to stress caused by low pH, low salinity and poor feed quality. Experiments were also conducted to scan the transcriptomes of juvenile oysters for genes involved in adaptation to ocean acidification. In addition, genotypes were identified for oysters that are more tolerant to low calcium carbonate saturation states. These results provided insights into genotype-phenotype interactions in O. edulis exposed to high levels of carbon dioxide stress by combining behavioural and genetic data.
Keywords
European flat oysters, oysters, ocean acidification, reproductive success, salinity
