Compounding effects of co-occurring disturbances on populations of a harmful bloom-forming mixotrophic protist
Anthropogenic activity is leading to increasing frequency and magnitude of disturbance in freshwater systems throughout the world. In turn, disturbance events are more likely to co-occur, compounding effects. Here we present a case study in which we investigated how the effects of co-occurring disturbances might interact to influence the abundance of a harmful algal bloom-forming species, Prymnesium parvum. The disturbances applied here included increased salinity, community composition change via the removal of large zooplankton, and elevated propagule pressure of P. parvum. We also examined the role that historical exposure to one of the disturbances played in influencing the effect of the co-occurring disturbances. We show that these types of disturbances can lead to synergistic or compounded effects, here influencing the abundance of a harmful algal species, and that historical exposure to a disturbance can influence this effect. These findings highlight the important role of increased and co-occurring disturbance in aquatic ecosystems and the role it may play in the formation of harmful algae blooms as the frequency of these occurrences increases.
KeywordsPrymnesium parvum Co-occurring disturbance Salinification Grazing Propagule pressure
The Texas Water Resource Institute Mills Scholarship, The J.H. Benedict, Sr. Memorial Graduate Student Scholarship and the William Roach Scholarship, all administered through Texas A&M University are acknowledged for tuition support.
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