Chapter 4 Habitats
Invasive species . Phragmites has become established in many of the state’s natural lakes and has replaced native shoreline vegetation. Hydrilla and Lyngbya have been introduced into Lake Waccamaw and intensively managed with herbicides. Invasive vegetation is a major threat to the natural lakes within the Coastal Plain. Runoff. Surface waters, including natural lakes, often receive wastes, sediments, and pollutants from runoff because of their position in the landscape (Dudgeon et al. 2006) . Changes in hydrology and water chemistry affect water quality. High water levels can create shoreline damage (e.g., erosion, flooding), while prolonged low water levels may contribute to water quality issues and impact delivery of lake ecosystem services (Foulds 1977; Wildman et al. 2011; Crase et al. 2008; Molinos et al. 2015) . Climate. Water levels may be low during droughts and periods of high temperatures, and lakes may become stratified with little or no vertical mixing within the water column. Under these conditions, DO levels in deeper waters may be depressed and become unsuitable for many aquatic organisms. Algal blooms in the surface water can exacerbate DO depletion and result in local degradation of water quality. Such conditions are temporary and are usually alleviated by increased water flow or increased wind velocity. Water level fluctuations may also lead to changes in patterns of boundary mixing (i.e., the process of enhanced mixing near the lateral boundaries of a lake that affects sediment resuspension and vertical nutrient fluxes), induced mainly in stratified lakes by internal wave activity at the depth of the thermocline. Progressively declining water levels would be expected to lower the thermocline and therefore, displace boundary mixing (Zohary and Ostrovsky 2011; Molinos et al. 2015) . Persistence of these issues can exacerbate water quality problems by contributing to long-term eutrophication in natural lakes (Hambright et al. 2004; Molinos et al. 2015) . Water Use . Water withdrawals for irrigation during summer droughts can cause low DO availability when reduced water levels result in higher water temperatures, especially along littoral edges. Combined with extended climate-related heat spells, drought, and increased storm severity (e.g., lightning strikes), there may be an increase in wildfire occurrences that prompt the need for water withdrawals lake water to fight the fires. 4.2.12.4 Climate Change Compared to Other Threats Comparing climate change to other ecosystem threats can help define short- and long-term conservation actions and recommendations. While climate change is not the most severe threat, synergistic effects combined with other existing conditions could stress these systems to the point where several species are unable to persist. The most important effect of climate change on lakes is likely to be the occurrence of more extreme rainfall events and more frequent droughts. Table 4.2.12-1 compares climate change with other existing threats.
4 - 95
2025 NC Wildlife Action Plan
Made with FlippingBook Ebook Creator