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Nutrient additions to wetlands in the Interlake region of Manitoba, Canada : Effects of a single pulse addition in spring / T.S. Gabor, H.R. Murkin, M.P. Stainton, J.A. Boughen, and R.D. Titman.

By: Contributor(s): Material type: TextTextSeries: Hydrobiologia. 279/280 497-510 Publication details: 1994.Description: illustrations ; 28 cmLOC classification:
  • GAB
Online resources: Summary: This study examined the responses of algae and invertebrates to a single application of N and P in a series of experimental wetland enclosures in the Interlake region of Manitoba during 1989 and 1990. N and P levels in the water, sediment and vegetation were also monitored. The 3 fertilization treatments were: dissolved inorganic (6200 g - N, 420 jtg - ' P), dissolved inorganic (3200 g - N, 210 jig 1- P) and organic (ground alfalfa meal: 6200 tg 1- 1 N, 420 tg 1- 1 p). Dissolved nutrients in the inorganic treatments were quickly depleted from the water column, but dissolved N increased in the water column of the alfalfa treatment as the alfalfa decomposed. No changes in N or P concentrations in the sediments or vegetation were detected. Phytoplankton biomass increased in all fertilized enclosures while epiphytic periphyton exhibited only minor responses. Epipelon biomass increased in the alfalfa treatment and metaphyton standing crops were highest in the high inorganic treatments. In the alfalfa treatment, high microbial respiration rapidly reduced dissolved oxygen concentrations which negatively affected invertebrates. This trend reversed as oxygen levels increased later in the experiment. Dominant nektonic and benthic invertebrates increased in the high inorganic and alfalfa treatments. Orthocladiinae emergence increased in the high inorganic and alfalfa treatments, while Chironominae and Tanypodinae increased in the alfalfa treatment. Second year responses by algae and invertebrate communities to the fertilization treatments were minimal. Annual single pulse fertilization has the potential to increase the productivity of Interlake wetlands when nutrients are applied in the spring, however it should be noted that at the levels used in this study the effects did not extend to the second year.

Includes bibliographical references (pages 509-510).

This study examined the responses of algae and invertebrates to a single application of N and P in a
series of experimental wetland enclosures in the Interlake region of Manitoba during 1989 and 1990. N
and P levels in the water, sediment and vegetation were also monitored. The 3 fertilization treatments
were: dissolved inorganic (6200 g - N, 420 jtg - ' P), dissolved inorganic (3200 g - N, 210 jig 1-
P) and organic (ground alfalfa meal: 6200 tg 1- 1 N, 420 tg 1- 1 p).
Dissolved nutrients in the inorganic treatments were quickly depleted from the water column, but
dissolved N increased in the water column of the alfalfa treatment as the alfalfa decomposed. No changes
in N or P concentrations in the sediments or vegetation were detected. Phytoplankton biomass increased
in all fertilized enclosures while epiphytic periphyton exhibited only minor responses. Epipelon biomass
increased in the alfalfa treatment and metaphyton standing crops were highest in the high inorganic
treatments.
In the alfalfa treatment, high microbial respiration rapidly reduced dissolved oxygen concentrations
which negatively affected invertebrates. This trend reversed as oxygen levels increased later in the
experiment. Dominant nektonic and benthic invertebrates increased in the high inorganic and alfalfa
treatments. Orthocladiinae emergence increased in the high inorganic and alfalfa treatments, while
Chironominae and Tanypodinae increased in the alfalfa treatment. Second year responses by algae and
invertebrate communities to the fertilization treatments were minimal. Annual single pulse fertilization
has the potential to increase the productivity of Interlake wetlands when nutrients are applied in the
spring, however it should be noted that at the levels used in this study the effects did not extend to the
second year.

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