Standard Laboratory Tests

Alkalinity – Indicates the water’s buffering capacity. Good buffering capacity can limit dangerous pH swings caused by the introduction of highly acidic or basic substances, the affects of which can be compounded by the consequent loss of aquatic life.

Carbon Dioxide – CO₂ gas is a product of respiration and a necessity for photosynthesis. High levels of dissolved CO₂ in the water can stress or kill fish.

Chloride – One of the major inorganic anions in water. In coastal communities chloride levels may be high due to saltwater intrusion, and levels over 250 mg/L chloride will have a detectable salty taste. Florida turf grasses have varying tolerances for chloride and levels exceeding 600 mg/L are not suitable for irrigation.

Conductivity, salinity, and total dissolved solids – These tests determine the total concentration of the ionized substances dissolved in the water. The concentration of these dissolved substances is measured by the water sample’s ability to carry an electrical current. A significant increase in conductivity may indicate a recent increase in domestic or industrial pollution. High dissolved solids may cause irrigation water to stain vehicles and other surfaces in the general vicinity.

Color – Color in water is a result of natural iron and manganese ions, decomposing organic plant material, tannins, plankton algae, and industrial and domestic pollution. Changes in color may reflect increases in dissolved nutrient levels.

Copper – This metal is an active ingredient of certain herbicides, especially copper sulfate (bluestone), which is frequently used to control algae. High concentrations of copper ions (Cu++) can be toxic to fish, especially trout. Copper applied to ponds with soft or acidic water is more toxic to aquatic life than in ponds with hard or alkaline water.

Fluridone – Fluridone is an aquatic herbicide commonly used to control pest plants in lakes. If the lake is also used for irrigation, a fluridone test may be necessary to ensure levels are safe for turf.

Iron – When concentrations exceed 0.1 mg/L, iron precipitates on exposure to air, decreasing pond clarity and encouraging iron bacteria, which affects the flavor of both fish and water. Levels greater than 0.3 mg/L can cause staining on buildings and sidewalks when the water is used for irrigation.

Nitrogen – This element is a product of the natural metabolism of plant and animal matter, and fertilizer runoff. Organic nitrogen can take many forms in water, including Nitrate, Nitrite, and Ammonia. When available, these nutrients promote plant and algae growth. Ammonia concentrations below 0.3 mg/L significantly limit plant and algae populations. Reduced fertilizer applications near shorelines will help prevent increases in these and other nutrient levels.

pH – The pH value of a body of water expresses its tendency to donate or accept hydrogen ions on a scale of 0 (very acidic) to 14 (very basic). Natural waters range from pH 6.5 to pH 8.5 and are often slightly basic. Any major pH deviations for a given water body could indicate the intrusion of strongly acidic or basic industrial wastes.

Phosphorus – Biologically available phosphorus is found in lakes, waterways and wastewater in the form of phosphates. The discharge of treated wastewater and agricultural drainage into a lake will increase a lake’s phosphate levels. Lawn and landscape fertilizer runoff is another major source of phosphate in lakes and their use should be avoided near the water. Phosphate increase is the most common cause of undesirable growth of aquatic weeds and algae.

Total and Fecal Coliform – These bacteria are used to indicate possible sewage contamination, which can lead to illness.

Total Hardness – Total hardness is defined as the concentration of calcium and magnesium in the water. Calcium is necessary for proper fish egg and fry development. Closely related to alkalinity and pH, sufficient hardness levels can help decrease ammonia and pH toxicity.

Turbidity – Lack of clarity, known as turbidity, in natural waters is caused by the presence of suspended solids such as silt, clay, fine organic and inorganic matter, plankton and other microscopic organisms. The turbidity test measures an optical property of the water sample and is used as an index of water clarity. Turbidity values of 10 N.T.U.’s (Nephelometric Turbidity Units) or more indicate high sediment concentrations, often due to construction activity in the drainage basin.

Site Observation and Testing

Dissolved Oxygen (DO) & Temperature Profiles – Dissolved oxygen is the most critical indicator of a lake’s health and water quality. Dissolved oxygen levels in natural waters are dependent on the physical, chemical and biochemical activities prevailing in the water body. Oxygen is added to aquatic ecosystems by aquatic plants and algae through the process of photosynthesis and also by diffusion at the water’s surface and atmosphere interface. Oxygen is depleted primarily by animal and plant respiration and decomposition.

Oxygen is required for fast oxidation of organic wastes including bottom muck. When the oxygen is used up in the bottom of the lake, anaerobic bacteria continue to break-down organic materials, creating toxic hydrogen sulfide gas in the process. For a healthy game-fish population, oxygen levels in the 6-10 mg/L range are necessary. Respiration stress in most fish occurs when oxygen levels are reduced to 4-5 mg/L. Temperature must also be considered when looking at oxygen levels in lakes since warmer water cannot hold as much oxygen as cooler water. A large difference between surface temperature and temperature at depth indicates that the lake is stratified, and is therefore in danger of having low oxygen levels below the surface.

Secchi Disk – This mechanical test to judge the depth of clarity of a body of water is accomplished by lowering a black and white disk into the water and recording the point at which it disappears. Higher values of Secchi disk transparency are found in very clear lakes.

Visual Algae Identification – Algae comes in different colors and some species produce toxins and/or odor compounds, so the first step in identifying it is to see it in its natural state. If the type or quantity is a problem, further tests will be conducted in the lab.

Aquatic Plant Identification – Different plants respond differently to herbicides, so identification of problem plants is absolutely necessary before treatment and many are easily identified in the field.