Ecological impacts of an exotic benthivorous fish, the common carp (Cyprinus carpio L.), on water quality, sedimentation, and submerged macrophyte biomass in wetland mesocosms / Pascal H.J. Badiou and L. Gordon Goldsborough.

Includes bibliographical references (pages 120-121)

We examined the interactions of the
common carp (Cyprinus carpio L.) and nutrient
additions on water quality, sedimentation rates, and
submerged macrophyte biomass in mesocosms in
Delta Marsh, Manitoba, Canada. We wanted to
determine if carp and nutrients interacted synergistically
to increase phytoplankton biomass. A two-bythree
duplicated, factorial design had the following
treatments: (1) control mesocosms with no carp or
nutrient additions; (2) low carp density and no nutrient
additions; (3) high carp density and no nutrient
additions; (4) no carp and nutrient additions; (5) low
carp density and nutrient additions; and (6) high carp
density and nutrient additions. The presence of carp
increased ammonia concentrations, turbidity, and
phytoplankton biomass as expected but did not
increase total reactive phosphorus concentrations.
The presence of carp did not appear to interact
synergistically with nutrient additions to increase
phytoplankton as has been suggested by others. In
mesocosms with high carp density and receiving
nutrient enrichment, phytoplankton appeared to be
suppressed relative to mesocosms receiving nutrient
enrichment only, and nutrient enrichment and low carp
density. Overall, the presence of carp appears to mimic
the effects of eutrophication. Our results demonstrate
that carp can cause a shift from a clear, macrophytedominated
state to a turbid phytoplankton-dominated
state at a biomass of less than 600 kg ha-1.