Geese as vectors for zooplankton dispersal: An example of undergraduate research at a small liberal arts college

Background/Question/Methods

Freshwater zooplankton occur in many aquatic ecosystems, yet natural dispersal is problematic because these animals cannot fly.  Floods disperse zooplankton, yet many aquatic ecosystems are too isolated to experience these connecting events.  Passive movement of diapausing eggs via bird intestines and wind are known dispersal methods, but evidence that living adult zooplankton disperse is often anecdotal.  Ecologists often assume a decades-old hypothesis that dispersal occurs via passive attachment to waterfowl, yet little documentation exists.  Research specifically designed to test passive attachment to migrating waterfowl must occur.  Two groups of undergraduates tested the hypothesis that migrating geese transport living adult zooplankton – specifically Daphnia and Cyclops.  Group one tested attachment by exposing cultured zooplankton to goose feather, and then to a domestic goose flock.  They rinsed 200ml of osmotically-balanced water, with known number of cultured zooplankton, on ten geese by holding a bird over a collecting tub, and then counted the total number of “recaptured” zooplankton.  Group two used the surviving recapture numbers to create four replicated aquatic systems that simulated the dispersed location.  They used 200ml of osmotically-balanced water per bird for a total of 50 wild Canada geese, from three wetlands, to collect and count living zooplankton.

Results/Conclusions

Group one documented zooplankton attachment to feathers, and living birds.  Total recapture numbers of living zooplankton were seven out of 1762 Daphnia and three out of 378 Cyclops.  These results represented 0.4% and 0.8% survival, respectively, for a simulated dispersal.  Although small, these numbers were sufficient for group two to establish lab colonies.  Seven Daphnia, and three Cyclops colonies, as well as one single Daphnia, and two Cyclops, colonies successfully reproduced for a minimum of five weeks.  The one Daphnia and two Cyclops simulations represented the minimum number necessary to theoretically establish a colony. The wild goose roundups collected five living Daphnia and seven living Cyclops from 50 geese over the course of three days.  Considering that hundreds of zooplankton can exist within a few cubic meters the numbers were small.  Yet, small numbers sufficiently established lab colonies.  The hypothesis that wild geese can passively transport attached adult Daphnia and Cyclops was supported, but more field work is necessary to document wild colony establishment.  This research produced new information and demonstrated that undergraduates at a small liberal arts college can conduct research with important information for ecology.