The blue mussel Mytilus edulis is vulnerable to the toxic dinoflagellate Karlodinium armiger-Adult filtration is inhibited and several life stages killed

Abstract

Blooms of the toxic dinoflagellates Karlodinium armiger and K. veneficum are frequently observed in Alfacs Bay, Spain, causing mass mortality to wild and farmed mussels. An isolate of K. armiger from Alfacs Bay was grown in the laboratory and exposed to adults, embryos and trochophore larvae of the blue mussel, Mytilus edulis. Adult mussels rejected to filter K. armiger at cell concentrations >1.5·103 cells ml-1. Exposure of adult mussels (23-33 mm shell length) to a range of K. armiger cell concentrations led to mussel mortality with LC50 values of 9.4·103 and 6.1·103 cells ml-1 after 24 and 48 h exposure to ~3.6·104 K. armiger cells ml-1, respectively. Karlodinium armiger also affected mussel embryos and trochophore larvae and feeding by K. armiger on both embryos and larvae was observed under the microscope. Embryos exposed to low K. armiger cell concentrations suffered no measurable mortality. However, at higher K. armiger cell concentrations the mortality of the embryos increased significantly with cell concentration and reached 97% at 1.8·103 K. armiger cells ml-1 after 29 h of exposure. Natural K. armiger blooms may not only have serious direct effects on benthic communities, but may also affect the recruitment of mussels in affected areas.

Fig 1. Clearance rate of Mytilus edulis exposed to Karlodinium armiger and Rhodomonas salina.

The mussels were exposed to a low and high bio-volume equivalent concentration of each algal species. Data presented as mean values with SE bars.

Fig 2. Mortality of Mytilus edulis exposed to six Karlodinium armiger concentrations for 24 and 48 h.

LC₅₀ values of 9.4·10³ ± 2.7·10³ cells ml^-1 and 6.1·10³ ± 0.3 ·10³ cells ml^-1 were found after 24 and 48 h, respectively. Data presented as mean values with SE bars.

Fig 3. Karlodinium armiger tube feeding on Mytilus edulis embryos and trochophore larvae.

Initial tube feeding by K. armiger on a mussel embryo (A). Karlodinium armiger cells attached to a mussel embryo causing the vitelline coat to disrupt and release of egg content (B). Karlodinium armiger attracted to egg content released from a disrupted embryos (C). Karlodinium armiger tube feeding on a mussel trochophore larva (D).

Fig 4. Mortality of Mytuilus edulis embryos and trochophore larvae after exposure to Karlodinium armiger at four different concentrations.

Mortalities of embryos and trochophore larvae, separately and when pooled as a function of K. armiger cell concentrations. Data presented as mean values with SE bars.