Assessing the use of Viviparus georgianus snails as a means for biomanipulation of cyanobacterial species Microcystis aeruginosa
Cyanobacterial blooms can produce toxins which can be fatal to organisms, including humans. Biomanipulation of cyanobacterial harmful algal blooms (CHABs) aims to proactively prevent their formation by maintaining continuous foraging pressure on cyanobacterial populations by increasing the number of some selected foraging organisms in the affected water body. Previous successful cases are limited to small scale operations, and organisms have included only herbivorous fish and zooplankton. Freshwater gastropods are diverse and abundant, and can be used in biomanipulation because they are easily collected and transported. Specifically, the freshwater snail species Viviparus georgianus has demonstrated filter-feeding characteristics and can live at high densities in eutrophic lakes. The aim of this thesis is to assess the potential use of this snail species as a potential means for biomanipulation of the cyanobacterial species Microcystis aeruginosa. We assessed this by using chlorophyll a (chl-a) as a measure for cyanobacteria in the upper and lower water columns of an ex-situ microcosm experimental system with and without the presence of snails, over an approximate 9-day time period. Our results demonstrated that in a clearwater system, the snails were unable to reduce the amount of chl-a present by ingestion. However, with the addition of silt and clay at varying turbidity levels, greater elimination of chl-a by snail ingestion was observed. Specifically, the addition of clay provided the most promising results. Overall, it was concluded that V. georgianus is able to eliminate Microcystis cells through ingestion, under specific conditions. Therefore, the application of this potential CHABs control method would have to be used in combination with the addition of sediment (silt or clay), or in a habitat that already has the minimal required amount of sediment present for successful results.