Nutrient additions to wetlands in the Interlake region of Manitoba,Canada: effects of a single pulse addition in spring

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 µg 1^–1 N, 420 µg 1^–1 P), dissolved inorganic (3200 µg 1^–1 N, 210 µg 1^–1 P) and organic (ground alfalfa meal: 6200 µg 1^–1 420 µg 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.     

Serologic evidence of influenza A infection in marine mammals of arctic Canada.

A serologic survey of influenza A antibodies was undertaken on 1,611 blood samples from five species of marine mammals collected from Arctic Canada from 1984-98. Sampling was done in 24 locations throughout the Canadian Arctic encompassing Sachs Harbor (72 degrees N, 125 degrees W), Northwest Territories in the west to Loks Land (63 degrees N, 64 degrees W), Nunavut in the east, to Eureka (80 degrees N, 86 degrees W), Nunavut in the north to Sanikiluaq (56 degrees N, 79 degrees W), Nunavut in the south. A competitive ELISA using a monoclonal antibody (Mab) against influenza A nucleoprotein (NP) was used. Five of 418 (1.2%) belugas (Delphinapterus leucas) and 23 of 903 (2.5%) ringed seals (Phoca hispida) were serologically positive. None of the 210 walruses (Odobenus rosmarus rosmarus), 76 narwhals (Monodon monoceros) and four bowhead whales (Balaena mysticetus) had detectable antibodies to influenza A. Positive belugas were identified from communities on southeast Baffin Island while positive ringed seals came from communities in the eastern, western and high Arctic. Virus isolation attempts on lung tissue from a seropositive beluga were unsuccessful. We believe that influenza A infection in marine mammals is sporadic, the infection is probably self-limiting, and it may not be able to be maintained in these animals. Although the predominant hemagglutinin (H) type was not determined and therefore the pathogenicity of the strains to humans is unknown, the hunting and consumption of marine mammals by the Inuit, may put them at risk for influenza A infection.     

Nutrient additions to wetlands in the Interlake region of Manitoba,Canada: effects of periodic additions throughout the growing season

The Interlake region of central Manitoba is characterized by numerous shallow, relatively unproductive wetlands. Typically, these wetlands are poorly utilized by breeding waterfowl in spite of generally reliable water conditions during spring and summer. Nutrient additions were made throughout the growing season to 18 PVC enclosures installed in a low productivity wetland near Lundar, Manitoba. Inorganic phosphorus (as H₃PO₄) and nitrogen (as NH₄NO₃) were added at bi-weekly intervals during the summer of 1988 at target rates of 0 and 0, 30 and 800, and 60 and 1600 µg 1^–1 (P and N respectively). Algal and invertebrate communities were monitored from mid-June to September, 1988. Phytoplankton, epiphytic periphyton and metaphyton communities demonstrated significant increases in biomass over the treatment period. No significant differences in epipelon community biomass were noted. An examination of several indicators of nutrient deficiency indicated that algal productivity was moderately to severely limited in all enclosures, with little or no mitigative effects noted due to nutrient addition treatment. No significant differences in numbers or biomass of total invertebrates or invertebrate functional groups attributed to fertilization were observed. Nutrient additions did increase community productivity, however the levels used in this study were insufficient to yield a sustained increase in primary or secondary productivity.