Chapter 1: Submergent Wetlands

Submergent Wetlands

Submergent wetlands are often referred to as ponds or open water wetlands. They are large, relatively deep, and flooded for most or all of the year.39 Approximately 260 km² (64,375 ac) of Great Salt Lake (GSL) wetland habitat is classified as submergent. Most of these submergent wetlands occur in large impoundments or wetland units where deep flooding can be accomplished through diking, diversion, and water level management.14 Submergent wetlands are characterized by an abundance of submerged aquatic vegetation (SAV) that grows while submerged within the water column or floating on the water’s surface.39 Most SAV are well adapted in constantly flooded environments because of tuberous roots and large, floating seeds.10

Plants

Spiral ditchgrass (Ruppia cirrhosa, p. 24) and sago pondweed (Stuckenia pectinata, p. 23) are two of the most common and valuable GSL submergent species. Both tolerate elevated salinity and are high-quality food sources for migratory birds; however, sago pondweed is considered the cornerstone SAV species.7 Its presence in a submergent wetland indicates the wetland’s productivity for birds. The entire plant is edible and highly nutritious, including the leaves, tubers, and large seeds.8; 39 Spiral ditchgrass is also highly nutritious but less productive; its importance to bird diets increases significantly during the winter months when other food sources are rare.62

Wetland water level management is a key tool for maintaining the appropriate levels of salinity and depth necessary for SAV growth and reproduction. In GSL wetlands, a flush of freshwater in the spring is important for maintaining optimal water and salinity levels.10 Freshwater inflow varies throughout GSL wetlands, so managing SAV is easier in areas with a consistent supply of freshwater than in areas that experience frequent summertime drought.50 To stimulate the most plant production and therefore create the highest food availability for birds, 38–45 cm (15–18 in) of water with brackish salinity (9–15 ppt) is optimal for sago pondweed.44 Spiral ditchgrass thrives best in shallow wetlands where water depth is often less than 30 cm (12 in) and salinity is between 10–21 ppt.35 Submergent vegetation provides habitat for macroinvertebrates and fish, but the physical disturbances from these species tend to alter SAV.15 Sago pondweed is especially intolerant of disturbances created by carp (Cyprinidae family).16 Carp are invasive bottom-feeding fish that uproot plants and increase water turbidity while searching for food in the mud.10 Managers can use pesticides or hydrologic drawdowns to control carp populations and decrease physical disturbances in submergent wetlands. Native SAV need nutrients like nitrogen and phosphorus to grow, but when water nutrient levels are too high, SAV can be negatively impacted. High levels of nitrogen or phosphorous cause algal blooms that block sunlight and inhibit the growth of SAV. At their thickest, algal blooms prevent birds from accessing food in the water column. To deal with excess nutrients, managers can draw down their wetlands, allowing nutrients to bind to soil particles, then managers can dredge and remove the soil.27