A MICROLIMNOLOGICAL STUDY OF THE FLUID HABITAT OF THE NORTHERN PITCHER PLANT, AND RELATIONSHIPS WITH ITS INSECT INHABITANTS.

D.J. Giberson and D. Blacquiere. Department of Biology, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4P3

Although the inhabitants of the northern pitcher plant have been well studied, little information is available on the physical/chemical habitat within the pitchers themselves. In this study, we evaluated water chemistry variables and temperature diurnally (every 1.5 hrs during daylight, on 3 sample dates) and throughout the season, in addition to regular biological collections. All factors were extremely variable, both seasonally and diurnally, and diurnal patterns also changed through the season. In early summer, oxygen levels were stable during the day (near 7 mg L^-1, near saturation), but later in summer, oxygen levels varied dramatically throughout the day (usually 4-8 mg L^-1). Levels never fell below 2 mg L^-1 in any pitcher, however. pH was also variable (values between 3.1 and 7.5), but was lowest early in the day and in the evenings, and early and late in the season. Alkalinity was extremely low (<5 mg L^-1 CaCO₃) so changes in CO₂ concentrations in the water relating to photosynthesis may drive the changes in pH. Water temperatures within the pitchers, though variable, were not as variable as the surrounding bog water. This study indicates that pitcher plant inhabitants are exposed to a wide range in physico-chemical conditions that could affect growth and development.