The effects of salinity, temperature, and Pomacea maculata herbivory on

Southwest Florida aquatic vegetation by: Shannan Mcaskill and Alexandra Rodriguez

● Scientific Name: Pomacea maculata

● Native to South America 1

● Negative ecosystem impacts 3,4:

○ Competitive exclusion of native snail

○ Parasites

○ Inhibit wetland restoration

○ Agricultural pest

○ Alters macrophyte community

structure

○ High consumption/growth rate

The Island Apple Snail

Tape Grass: What is it and Why is it Important?

● Scientific name: Vallisneria americana

● Deep-rooted, freshwater macrophyte 5

○ Tolerates about 10 psu salinity

● Ecological importance 2,5:

○ food (manatees)

○ shelter (nursery)

○ water clarity

○ reduces erosion

(Doering et al., 1999)

Tape Grass in the Caloosahatchee

Feeding Trials

One-way ANOVA

● Temperature increased grazing rate (P-value: 0.0049).

One-way ANOVA (log10 transform)

● Salinity has a significant effect on grazing rate (P: <0.0001)

Monoculture Polyculture

Feeding Choice

Both

CONTROL FREE CHOICE

Two-way ANOVA

● Conclusive preference for V. americana when presented with free choice (P-value: 0.0185)

Two-way ANOVA ● Affinity for H. verticillata in monoculture, V.

americana in polyculture ● Compensatory feeding - may have eaten more

Hydrilla because it is a poorer food choice

Two-way ANOVA (square root transform)

● Conclusive preference for V. americana in monoculture and polyculture (P-

value: <0.0001)

● More evidence that Pomacea maculata is not an effective way to manage

invasive aquatic vegetation.

Mesocosm Experiment

0 psu with snails 5 psu with snails

5 psu without snails 10 psu without snails

10 psu with snails 15 psu with snails

15 psu without snails

Week 4

0 psu without snails

Two-way ANOVA (square root transform)

● Significant difference between tanks containing snails and tanks with no snails (P-value: 0.0087)

Nominal Logistic- time (weeks) vs. treatment (salinity) on percent snail mortality

● No significant interactive effect between time and treatment.

● Statistically significant difference between treatment (P-value: <0.0001).

Questions?

•1Burlakova, L.E., Padilla, D.K., Karatayev, A.Y., Hollas, D.N., Cartwright, L.D., and Nichol, K.D., 2010, Differences in population dynamics and potential

impacts of a freshwater invader driven by temporal habitat stability, Biological Invasions, Vol. 12 (4), pp.927-941

•2Doering, P. H., Chamberlain, R. H., Donohue, K. M., and Steinman, A. D., 1999, Effect of salinity on the growth of Vallisneria americana from the

Caloosahatchee Estuary (South Florida), Florida Scientist, Vol.62(2), pp.89-105

•3Horgan, F.G., Stuart, A.M., and Kudavidanage, E.P., 2014, Impact of invasive apple snails on the functioning and services of natural and managed

wetlands, Acta Oecologica, Vol.54, p.90-100

•4Karatayev, A. Y., Burlakova, L. E., Karatayev, V. A., and Padilla, D. K., 2009, Introduction, distribution, spread, and impacts of exotic freshwater

gastropods in Texas, Hydrobiologia, 619(1), pp.181-194

•5Wigand, C., Wehr, J., Limburg, K., Gorham, B., Longergan, S., and Findlay, S., 2000, Effect of Vallisneria americana (L.) on community structure and

ecosystem function in lake mesocosms, Hydrobiologia, Vol.418(1), pp.137-146

References