Ecosystem response to changes in water level of Lake Ontario marshes: lessons from the restoration of Cootes Paradise Marsh

Abstract

A general understanding of how aquatic vegetation responds to water-level fluctuations is needed to guide restoration of Great Lakes coastal wetlands because inter-annual and seasonal variations often confound effects of costly remedial actions. In 1997, common carp (Cyprinus carpio) was removed from Cootes Paradise Marsh (L. Ontario) to reduce sediment resuspension and bioturbation, and thus regenerate marsh plants that had declined dramatically since the 1930s. Data from 1934 to 1993 were re-assembled from the literature to relate percentage cover of emergent vegetation to mean summer water level. A non-linear regression equation explained close to 90% of the variation compared with 80% for a non-linear equation, and this trend was confirmed for the dominant species, Typha latifolia. A modest recovery of emergent vegetation in 1999 following carp exclusion could have been predicted from declining water level alone, without invoking any effects of the biomanipulation. An unusually cool spring in 1997 delayed the migration of spawning planktivores into the marsh. This resulted in a grazer-mediated clear-water phase that coincided with a resurgence of the submersed aquatic vegetation (SAV) community in 1997, which declined again in 1999 when low water levels occurred. Even though decrease in water level was significantly related to increased suspended solids and greater light attenuation, light conditions appeared to have been adequate in marsh embayments to support SAV growth, according to a published relationship between maximum depth of SAV colonization and light extinction coefficient. I suggest that wave disturbance and propagule burial associated with shallow water depths may have been the main reasons for the decline of the SAV in 1999 and 2000.

Investigation into potential impacts of implementation of water sensitive urban design components

“…It is, therefore, recommended that further study be conducted to see whether this change in water volume reaching receiving waters over time will impact on the ecological environment as the studies presented by Chow-Fraser [2] and Papastergiadou et al [3] have shown that even slight changes over time can make an impact on the ecological environment. As this study only presents hypothetical scenarios of the application of WSUD to a catchment, further validation of the study in functional catchments with varying ranges of WSUD implemented should be considered.…”

“…This has the potential to adversely impact the ecosystem. Undesirable ecological and environmental impacts of reductions in water flow have already been established [2,3]. However, the potential adverse impacts of WSUD implementations have yet to be fully explored.…”

Migrating and breeding bird use of restored shallow lakes in Iowa

“…had their greatest frequencies in older restorations, particularly in 2017. This variation and decline could be due to grazing from waterfowl (Lauridsen et al 1993), water level fluctuations (Chow-Fraser 2005), changes in light conditions (Bini et al 1999), temperature (Minc 1997, Smith andMoelyowati 1998), or changes in nutrient inputs (Lougheed et al 2001). …”

“…In an effort to remedy the degradation of shallow lakes, several restoration projects have focused on implementing this wet-dry cycle as a management tool (Chow-Fraser 2005, Giesthardt et al 2013). Many of these projects focus on maintaining conditions that favor abundant vegetation, particularly emergent vegetation and submersed aquatic plants, and may result in a shift to a clear water state , Chow-Fraser 2005, Søndergaard et al 2007).…”

“…Many of these projects focus on maintaining conditions that favor abundant vegetation, particularly emergent vegetation and submersed aquatic plants, and may result in a shift to a clear water state , Chow-Fraser 2005, Søndergaard et al 2007). While this effort has proved to be successful for some wetlands, several factors may prevent a project from persisting in this desired state for long periods of time (e.g., >10 years) and continuous management, such as fish removal and water level manipulations, may be necessary (Søndergaard et al 2007, Hanson et al 2017.…”