Concentration addition and independent action assessments of the binary mixtures of four toxicants on zebra mussel (Dreissena polymorpha) mortality.

Researchers most often focus on individual toxicants when identifying effective chemical control agents for aquatic invasive species; however, toxicant mixtures may elicit synergistic effects. Synergistic effects may decrease required concentrations and shorten exposure durations for treatments. We investigated four toxicants (EarthTec QZ, Clam-Trol CT-2, niclosamide, and potassium chloride) that have been considered to control invasive zebra mussels (Dreissena polymorpha Pallas, 1771). We determined the toxicity of binary mixtures for five different mixture ratios to adult mussels. We compared our observations to predictions made with concentration addition and independent action paradigms, as based on the dose-response relationships of each individual toxicant. We calculated the model deviation ratio for each combination at the LC50 and LC90 and identified three possible interactions: synergy, antagonism, and additivity. We found that mixtures of niclosamide and Clam-Trol CT-2 were the most synergistic while mixtures that included potassium chloride were largely additive to antagonistic. The use of synergistic combinations has potential to decrease the overall volume and concentration of individual toxicants required for dreissenid mussel treatments, thereby decreasing cost.

Transoceanic dispersal of the mussel Mytilus galloprovincialis on Japanese tsunami marine debris: An approach for evaluating rafting of a coastal species at sea.

Biofouled debris from the 2011 Great East Japan earthquake and tsunami has landed in the Northeast Pacific and along the Hawaiian Islands since 2012. As of 2017, >630 biofouled debris items with >320 living species of algae, invertebrates, and fish have been examined. The invasive mussel Mytilus galloprovincialis was present on >50% of those items. Size, reproduction, and growth of this filter-feeding species were examined to better understand long-distance rafting of a coastal species. The majority of mussels (79%) had developing or mature gametes, and growth rates averaged 0.075±0.018 SE mm/day. Structural and elemental (barium/calcium) analysis of mussel shells generated estimates of growth in coastal waters (mean=1.3 to 25mm total length), which provides an indication of residence times in waters along North America and the Hawaiian Islands prior to landing. Detailed studies of individual species contribute to our understanding of debris as a transport vector and aid efforts to evaluate potential risks associated with marine debris.

Modelo preditivo de sobrevivência do Mexilhão Dourado (Limnoperna fortunei) em relação a variações de salinidade na Laguna dos Patos, RS, Brasil / Predictive model of survival of the Golden Mussel (Limnoperna fortunei) in relation to variations of salinity in the Laguna dos Patos, RS, Brazil

Limnoperna fortunei (mexilhão dourado), um bivalve de água doce do sudeste da Ásia, invadiu o sul da América do Sul em torno de 1991. Dados de ocorrência da espécie e salinidade ao longo do ano foram usados para predizer o potencial de sobrevivência de L. fortunei na Laguna dos Patos, RS. Um modelo preditivo foi construído usando regressão logística. Obtivemos na literatura 26 registros de presença (vivo, morto) de L. fortunei e valores de salinidade medidos em cada um destes registros na Laguna dos Patos entre o período de 2001 a 2004. Registros adicionais de salinidade foram utilizados para interpolar os valores por toda a Laguna dos Patos. Sobrevivência de L. fortunei diminui quando a salinidade aumenta na Laguna dos Patos. Os mapas de distribuição predita das áreas favoráveis à sobrevivência de L. fortunei indicam que durante os períodos de baixas salinidades as regiões límnica, pré-límnica e estuarina da laguna mostraram-se favoráveis para a sobrevivência da espécie. Nos períodos de altas salinidades (verão) a sobrevivência do molusco é favorável apenas na região límnica e na região pré-límnica. Estes resultados sugerem que o controle mais efetivo desta espécie deve ser feito durante o verão.

Limnoperna fortunei (golden mussel), a freshwater bivalve native to Southeast Asia, invaded southern South America around 1991. Using species' occurrence records and salinity in different seasons in Laguna dos Patos, RS, Brazil, we predict survival probabilities in different regions of the lagoon during the different seasons of the year. We fitted the data to a logistic regression model. A total of 26 presence records (live, dead) of L. fortunei and salinity at those locations were obtained from the literature for the Laguna dos Patos in the period 2001-2004. Additional data on salinity were used to interpolate salinity values to all regions of the lagoon. The logistic regression model shows that survival decreases as salinity increases. The model predicted high survival probability of the species during periods of low salinity (austral winter) in the limnic, pre-limnic and estuarine regions of the lagoon. During the high salinity period (summer), the species is able to survive only in the limnic and pre-limnic region of the lagoon. These data suggest that control measures should be carried out most effectively during the summer.