Uptake and elimination of brevetoxin in the invasive green mussel, Perna viridis, during natural Karenia brevis blooms in southwest Florida

Abstract

Perna viridis is a recently introduced species to US coastal waters and have vigorously spread throughout the southeastern seaboard since their invasion. Little information regarding their response to local environmental factors has been reported including responses to the local HAB species, Karenia brevis. This study monitored the tissue toxin concentration of brevetoxins in P. viridis from existing populations throughout two consecutive natural K. brevis blooms. The results showed P. viridis to rapidly accumulate PbTx upon exposure to the bloom, far exceeding the peak tissue concentrations of oysters, Crassostrea virginica, sampled during the same period, 57,653 ± 15,937 and 33,462 ± 10,391 ng g(-1) PbTx-3 equivalent, respectively. Further, P. viridis retained high PbTx concentrations in their tissues post bloom remaining above the regulatory limit for human consumption for 4-5 months, significantly longer than the depuration time of 2-8 weeks for native oyster and clam species. In the second year, the bloom persisted at high cell concentrations resulting in prolonged exposure and higher PbTx tissue concentrations indicating increased bioaccumulation in green mussels. While this species is not currently harvested for human consumption, the threat for post bloom trophic transfer could pose negative impacts on other important fisheries and higher food web implications.

Potential impacts of blooms of the toxic dinoflagellate Karenia brevis on the growth, survival and juvenile recruitment of the non-native green mussel Perna viridis in southeastern United States

“…Visual observations of the populations in Estero Bay have shown high densities with no apparent mortality events in the years prior to this study (Volety et al, unpublished data) and while previous work has shown P. viridis to accumulate high levels of toxins produced by K. brevis in their tissues (McFarland et al, 2015), this study is the first to look at chronic effects on population structure during natural blooms in established populations.…”

“…The first mortality event was observed two months post-bloom dissipation (March 2012), during which time PbTx tissue concentrations were nearly 20 times the shellfish regulatory limit (McFarland et al 2015). Previous studies have indicated that local bivalves typically tolerate K. brevis blooms and toxin accumulation with high survival rates during natural exposures (Pierce et al 2004;Plakas et al 2008).…”

“…Growth was assessed using independent t-tests to detect differences in mean length between months, and linear regressions were used to detect relationships between growth rate and environmental parameters. Spearman Rank Correlations were used to detect changes in growth during months with K. brevis blooms present and months with tissue concentrations above the regulatory limit (data from McFarland et al 2015). Mortality was analyzed graphically, and Kaplan-Meier survival analysis used to calculate mean survival time for comparison between seasons.…”

“…Likewise, P. viridis showed high mortality rates compared with other bivalves during laboratory exposures to Alexandrium monilatum ) and Baker et al (2012) observed >90% P. viridis morality following a K. brevis bloom in Tampa Bay, Florida. As a recently introduced species, P. viridis may lack the adaptations to tolerate and eliminate PbTx, increasing vulnerability and physiological stress (McFarland et al, 2015).…”

“…Conversely, local bivalves have been documented to have high survival rates during red tide blooms (Pierce et al 2004;Plakas et al 2008); however, sublethal effects during short term laboratory studies have demonstrated reduced clearance rates (Leverone et al 2007), loss of muscle control (Roberts et al 1979), increased susceptibility to disease and infection (Landsberg 2002), and subcellular effects including lysosomal disruption and alterations in lipid peroxidation (Keppler et al 2006). Sessile organisms, such as marine bivalves, may be exposed to sublethal concentrations that persist for months, potentially amplifying adverse effects observed in laboratory studies and presenting greater consequences to overall health, growth, and survival of the organism due to chronic effects of prolonged exposure (Griffith et al 2013;McFarland et al 2015).…”