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

Frank Melzner,Sofie Bjørnholt Binzer,Bent Vismann,Per Juel Hansen,Regitze Benedicte Carlstedt Lundgreen,Terje Berge

doi:10.1371/journal.pone.0199306

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.

Highlights

In Alfacs Bay, Ebro Delta, Spain, in the Mediterranean, Karlodinium veneficum and K. armiger
Lower K. armiger concentrations resulted in reduced mortalities of the mussels after 48 h, with 91% mortality for mussels exposed to 1.45Á104 ± 1.59Á104 cells ml-1, 76% mortality for mussels exposed to 8.00Á103 ± 0.58Á103 cells ml-1 and 19% mortality to mussels exposed to 3.99Á103 ± 0.23Á103 cells ml-1
The mussel Lasaea rubra refused to feed on a suspension of K. veneficum during 3 h exposure, when the alga was present in low concentrations (62 cells ml-1) M. edulis were able to ingest the same strain during 6 days of exposure [27, 37]

Summary

Introduction

In Alfacs Bay, Ebro Delta, Spain, in the Mediterranean, Karlodinium veneficum and K. armiger Gyrodinium corsicum) co-occur and blooms have occurred consistently since 1994 [1,2,3,4]. These blooms may last up to 3 months with maximum cell concentrations of up to 2.0Á104 cells ml-1 and are associated with mass mortality of adult mussels in both raft cultures and natural populations [1, 2, 4]. Karlodinium veneficum produces karlotoxins (KmTx) [5,6,7,8] which have been described to possess ichthyotoxic, cytotoxic and hemolytic modes of action [9,10,11].

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Conclusion