Aquatic Invasive Species

Elser from Arizona State University and his team conducted a study examining the distribution and competitive effects of the invasive zooplankton Daphnia lumholtzi in Arizona. First detected in Texas in 1990, this species indigenous to Africa, Australia, and India has spread throughout the midwestern and southern United States.

Elser conducted a field sampling of 12 reservoirs in central Arizona and a competition experiment involving water from Canyon Lake. The samplings demonstrated that D lumholtzi was dispersed across central Arizona in various watersheds, some with a greater percentage of the exotic zooplankton than others (ranging from none to more than the native species). This proves the persistence of this specie’s invasion in Arizona. The competition experiments found that the production of both species (D lumholtzi and native D pulex) decreased when both were present at the lake. Also, D lumholtzi reduced total zooplankton production. Therefore, communities dominated by D lumholtzi are expected to be less fertile and retain lower biomass.

Research on this detrimental species will continue because it impacts plankton communities and fish production since their spination renders them inedible.

Resource: Journal of the Arizona-Nevada Academy of Science Vol. 34(2): pp 89-94. (2002)

Water heating has been determined to be an effective ballast water treatment method; however the method has major limitations one in particular being the heating time required for efficiency.  Laboratory results have showed that conventional water heating requires a temperature of at least 35 ⁰C for 20-80 hours to be effective. However a novel technique, short-time technique, only requires temperatures between (40- 65 ⁰ C ) for 15 hours has been effective.

Quilez-Badia from the University of Newcastle upon Tyne, et al.(2008)  conducted  a  field study short-time high temperature under operational conditions, with the aim of monitoring the method’s effectiveness at removing bacteria, phytoplankton and zooplankton.

According to Badia et al.(2008) the results indicate that running the water through the pump system installed in the short-time method increased the  mortality rate of the microorganisms, but increasing the temperature above 55⁰C did not improve the efficiency of the short-time heat treatment.

Source: Marine Poll Bull 2008, 56(09) 1093-1097 DOI:   10.1016/j.marpolbul.1037.2007.09.036