Water Quality Management In Lakes Dr. Philip Bedient

Control of Phosphorus in Lakes Phosphorus is usually the limiting nutrient Control of cultural eutrophication must be accomplished by reducing the input of phosphorus to the lake Phosphorus concentration is reduced as it is buried in the sediment Sources of phosphorus:  Weathering of rocks  Human activity such as municipal and industrial wastewaters, seepage from septic tanks, and agricultural runoff that contains phosphorus fertilizers

Municipal and Industrial Wastewaters Both municipal and industrial wastewaters contain phosphorus from human excrement The only way to reduce this is by advanced waste treatment processes Major source of phosphorus used to be laundry detergent These detergents were banned to help reduce phosphorus input into lakes

Septic Tank Seepage If the capacity of the soil to adsorb phosphorus is exceeded, all additional phosphorus is sent to the lake The time for phosphorus to reach the lake depends on:  Type of soil  Distance to the lake  Amount of wastewater generated  Concentration of phosphorus in wastewater To prevent phosphorus from reaching lakes, the tile field must be put far away from the lake so that the adsorption capacity of the soil is not exceeded

Agricultural Runoff Phosphorus is an important ingredient in fertilizers Phosphorus bound to soil particles is carried to lakes by soil erosion To help stop this:  Farmers can fertilize more often with smaller amounts  Actions can be taken to stop soil erosion

Acidification of Lakes Pure rainwater is slightly acidic with a pH of 5.6 Acid Rain- Acid Rain- precipitation with a pH less than 5.6 Acid rain has caused:  Complete eradication of some fish species  Acidification of more than 1350 mid- Atlantic Highland streams  Acidification of about 580 streams in the mid- Atlantic Coastal Plain  Acidification of more than 90% of streams in the New Jersey Pine Barrens

Acid Rain Low pH levels are caused by emissions of sulfur and nitrogen oxides from the combustion of fossil fuels Acid decomposition- Acid decomposition-term for acid rain because it can be deposited in both a wet and dry form Fish are often killed by low pH levels and high aluminum concentrations

Aluminum Concentrations At conventional pH levels, aluminum rarely exists Acid deposition can cause stress effects on aquatic organisms such as:  Failure to reproduce  Gill damage resulting in respiratory problems  Failure of eggs to hatch  Interference with Ca uptake (molluscs)

Acidification of Lakes Lakes have a carbonate buffer system If the buffer capacity of the lake is not exceeded, pH of the lake will not be affected by acid rain Calcareous soil- Calcareous soil- contains large quantities of calcium carbonate (CaCO 3 ) Lakes formed in this type of soil resist acidification

Acidification of Lakes Cont. Factors that affect susceptibility of a lake to acidification:  Depth of soil  Make up of bedrock  Slope and size of watershed  Type of vegetation

Water Quality in Estuaries Estuary- Estuary- formed along the coastline where freshwater from rivers and streams flows into the ocean Water transitions from fresh to salty Estuaries are:  Partially enclosed by land  Influenced by tides  Protected from the ocean’s wind, waves,etc.

Estuaries Cont. Also referred to as bays, lagoons, harbors, inlets, or sounds Complex and specialized ecosystems form out of a cycle of wetting and drying, and the submersion and reappearance of aquatic organisms There is an abundance of life-giving nutrients Many different species and habitats exist here

Functions of Estuaries Estuaries:  Provide sanctuary to nesting and spawning animals  Filter water of its sediments and pollutants and make it clean  Absorb floodwaters and dissipate storm surges  Help prevent erosion  Make shorelines more stable

Estuaries and Wildlife Estuaries have recently experienced:  Declines in fish and wildlife  Introduction of invasive species  Deterioration in water quality  Reduction in overall ecosystem health Too many nutrients can cause:  Fish disease  “Red and brown tides”  Algae blooms  Low dissolved oxygen

Estuaries and Pathogens Pathogens are harmful to swimmers, surfers, divers, and seafood consumers Sources of pathogens include:  Urban and agricultural runoff  Illegal sewer connections Faulty or leaky septic systems  Sewage treatment plant discharges  Combined sewer overflows  Boat and marina waste  Waste from wildlife

Estuaries and New Species With the global transportation system came the introduction of nonnative or exotic species The introduction of exotic species has:  Modified nutrient cycles of soil fertility  Increased erosion  Interfered with navigation  Helped develop agricultural irrigation  Introduced sport and commercial fishing  Increased boating and beach use The Chesapeake Bay Agreement and the National Estuary Program (NEP) were created to protect ecosystems

4 Aspects of an Estuary In order to understand an estuary, the following issues must be studied:  Salinity  Nutrients  Wildlife, Fish and Shellfish  Toxicants

Salinity in Galveston Bay There has been a decline in the bay’s salinity Most bayous are experiencing an increase in flow due to:  Increase in development  Increased return flows of wastewater, including groundwater  Salinity dynamics in Galveston are now more obscure, complex, and intractable

Nutrients in Galveston Bay 60% of wastewater in Texas flows to Galveston Bay Much of the upper watershed consists of cultivated and urban lands with high nutrient runoff potential There has been a decline in the loading of nutrients into the bay There has been a reduction of point source loadings The problem now is urbanized tributaries where fish kills and dissolved oxygen problems suggest nonpoint source problems

Galveston’s Wildlife, Fish and Shellfish There has been a loss in emergent wetlands The leading cause of habitat loss is converting to open water and barren flats Urban development is responsible for less than 10% of wetland loss There was a decline for only 2 out of 14 finfish and shellfish species that were analyzed Has a great effect on birds

Toxicants in Galveston Bay Toxic contamination poses a risk to individual recreational or subsistence seafood consumers The highest concentrations of toxicants are usually in the upper bay There is much need for:  Development of sediment standards  Improvement of analytical techniques  Improved risk analysis  Communication of risks to the seafood-consuming public

Galveston’s Habitats Habitats are being destroyed by human activity Much wetland loss is due to conversion to open water or mud flats seagrass Many aquatic vegetation beds (especially seagrass) have been lost due to:  Subsidence  Dredging  Hurricane Carla  Chemical spills  Shoreline development  Boat traffic  Wastewater discharges  Loss of habitat poses a threat to seafood productivity and the ability for the bay to be a healthy ecosystem