Spring Microhabitat Oxygen Dynamics of Blue Lake, a Yazoo River Oxbow in Berclair MS

Author(s): Andrews, C.; Kröger, R.; Miranda, L.

Shallow oxbow lakes carved in rich alluvial floodplains can support multiple microhabitats that maintain aquatic diversity. Oxbow lakes have a high shoreline to surface area ratio and are often connected to or surrounded by inundated wetlands such as cypress and tupelo brakes, creating within-lake structural habitat variability that may influence biotic composition. Furthermore, these microhabitats fundamentally function in different ways. We studied microhabitat oxygen dynamics of an oxbow lake in the Mississippi Alluvial Valley. Blue Lake has over 8 km of shoreline and is permanently connected to a tupelo brake (approximately 350 ha) inundated with 0.5-1 m of water during the spring, an important time for reproduction. Using hourly diel surface dissolved oxygen (DO) data collected in April-July 2012, we investigate several descriptors of DO dynamics including mean DO, daily DO peaks, rate of DO fall, time of DO peaks, and percent of time above minimum DO thresholds (2 and 5 mg/L). We test differences in spring oxygen dynamics between three habitat types (littoral, pelagic, and brake) using a MANCOVA (p<0.001) and explore the possibility of oxygen refugia in hypoxic systems. Mean temperature along with four DO metrics: mean, minimum, maximum, and range DO showed significant (p<0.05) difference in means and slope between sites. The observed differences promote habitat diversity likely to influence biotic composition and distribution.

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