Science Inventory

Autonomous underwater glider observations in southern Lake Ontario and Niagara River plume

Citation:

McKinney, P., T. Hollenhorst, AND J. Hoffman. Autonomous underwater glider observations in southern Lake Ontario and Niagara River plume. Aquatic Ecosystem Health and Management. Taylor & Francis, Inc., Philadelphia, PA, 25(1):102-113, (2022). https://doi.org/10.14321/aehm.025.01.102

Impact/Purpose:

This article presents autonomous glider observations of water quality parameters from the 2018 Lake Ontario Cooperative Science and Monitoring Initiative (CSMI) focused on the southern shore of the lake between the Niagara River and Rochester, NY. A better characterization of spatio-temporal dynamics of the Niagara river plume, the deep chlorophyll maximum, and the characteristics of nearshore and offshore water quality zones is needed to address ongoing ecological change. To address this gap, we evaluated vertical and horizontal gradients of basic water quality parameters in nearshore and offshore areas of southern Lake Ontario and the Niagara River plume using observations gained in two autonomous glider deployments.

Description:

The nearshore areas of the Laurentian Great Lakes provide valuable ecosystem services including habitat for a variety of species and water for surrounding communities. Recent declines in nearshore water quality have increased the need for understanding the connectivity between nearshore and offshore areas; however observing water quality variability across the dynamic nearshore to offshore transition zone poses logistical challenges for traditional observing systems. Here we evaluate cross-shore and along-shore water quality gradients using observations from two three-week deployments of a Slocum autonomous glider in southern Lake Ontario. The glider was deployed between the Niagara River mouth and Rochester, NY during early and late summer 2018, and each deployment resulted in over 3000 vertical profiles of the water column and several transects between 2 km and 20 km from shore. In early summer, the cross-shore chlorophyll gradient was characterized by highest values just below the surface, at the frontal zone between weakly stratified conditions closer to shore and unstratified conditions offshore. In late summer, stratified conditions extended across the entire survey area. The depth of the thermocline was deeper and chlorophyll values were lower within 10 km of shore than offshore, where the highest chlorophyll values were observed in a distinct layer below the thermocline. In both early and late summer, the frontal boundary indicated by the cross-shore chlorophyll gradient was located below the surface and well offshore of what is typically considered the nearshore zone but was within the width of the coastal boundary layer. The high-resolution glider observations provide a detailed view of patterns of variability across a dynamic coastal zone and pinpoint the cross-shore frontal boundary that may be important for biologists to differentiate biological communities.