Abstract:
The zebra mussel (Dreissena polymorpha) is an aquatic invasive mollusk brought
to North America via cargo ships from the Black and Caspian seas in 1986. A biofouling
species, zebra mussels not only cause damage to submerged manmade materials but also
outcompete native mussels, many of which are already critically endangered. Zebra
mussels also destroy ecosystems by disrupting native food webs. The objectives of my
study were to determine: 1) the best method for early detection of a zebra mussel
infestation; 2) the distribution pattern of zebra mussels in the Marais des Cygnes River;
and 3) stages of gametogenesis achieved by zebra mussels in the Marais des Cygnes
River and Melvern Lake, Kansas. From June–November 2013 and May–November
2014, I investigated the invasion of zebra mussels in the Marais des Cygnes River from a
source population in Melvern Lake, downstream 196 river-km. I used 30-minute
inspection of shoreline, settlement structures, cross-polarized light microscopy (CPLM)
iii
of plankton, and detection of environmental DNA (eDNA) to determine which of these
methods would provide the earliest indication of a zebra mussel infestation. I chose 12
sites of three site types (lake, free-flowing river, and lowhead dam) to determine whether
lowhead dams influenced the dispersal and distribution of zebra mussels downstream
from the source lake. I also performed histological analysis to determine whether zebra
mussels entered a mature stage of gametogenesis in the river and sought to determine
whether increased veliger densities were due to instream recruitment or simply
accumulation from the upstream source population. CPLM of water samples taken via
plankton net tows gave the earliest indication of infestation at previously non
documented sites. The density of zebra mussels (both settled recruits and veligers)
decreased with distance from the source lake, with peaks of densities at lowhead dam
sites. Zebra mussels achieved sexual maturity, with correlative likelihood of
reproduction, at both free-flowing and inundated (dammed) sites, consistent with the
downstream–march model of dispersal.
