Tolerance of early life-stages in Ciona intestinalis to bubble streams and suspended particles.
There is an urgent need to develop and test potential eradication agents to prevent biofouling by ascidian tunicates in sheltered harbor's before they can spread to, and subsequently, disrupt benthic ecosystems and aquaculture ventures. We test the effects of bubble streams and suspended particles on two key stages in the early life cycle of Ciona intestinalis (Linnaeus, 1767); (i) Larval settlement 3 d after introducing free swimming larvae, and (ii) juvenile survival following exposure of ∼21 d old juvenile recruits to the tested treatments for the first time. Larval settlement was effectively prevented after exposure to bubble streams at >10 l min-1 or ≥25 Nephelometric Turbidity Units (NTU) of suspended particles. Suspended particles settling as a layer ≥0.3 mm thick onto the test substrate also reduced larval settlement by over 90%. None of the treatments were effective at eradicating juvenile C. intestinalis which proved more resistant to the tested treatments. Body size in juvenile recruits was also not significantly different across bubble stream rates. Juvenile recruits exposed to suspended particles were, however, significantly smaller than in the control treatment. In conclusion, as C. intestinalis settled, and grew, it became progressively more resilient to the tested treatments. Thus, continuous treatment is required during the spawning season to target larval settlement and prevent fouling by Ciona intestinalis.