Salinity and temperature tolerances of Neomysis americana (Crustacea: Mysida) sub adults: Perspectives on vulnerability, and distribution in South America

Mysid Neomysis americana links the benthic and pelagic food webs of numerous estuaries of the Western Atlantic. Aim was to understand the vulnerability of one of their recruitment stages i.e. sub adults to realistic ranges of salinity and temperature. Such may help to understand their present and predict future latitudinal distribution. Sub adults of N. americana were collected from Laguna de Rocha estuary, Uruguay and exposed to salinities 5, 10, 15, 20, 25, and 30 at each of four experimental temperatures: 10 °C, 20 °C, 25 °C and 30 °C, for 72 h. Irrespective of temperature, survival was lowest in salinity 5. Survival was overall high in salinity 15 but in higher salinities such as 25, 30 mysids struggled to survive. Survival was particularly low in 10 °C, highest in 20 °C; and did not improve significantly in 25 °C and 30 °C. Results indicate that the recruits of N. americana can only withstand intermediate salinities and temperatures. Their vulnerability during seasonal anomalies, floods and droughts cannot be ruled out. Narrow range of temperature tolerance of the recruits may be a reason of absence of N. americana in cold temperate and warm tropical Atlantic coasts of South America. In the context of climatic warming, N. americana may extend its distribution along the southern coasts of Argentina but not towards northern Brazil.