Eelgrass Project Data

There are several parameters that students will monitor to ensure a healthy environment for fish and eelgrass. These measurements can be made with chemical test kits or probes.

pH: Safe levels: 6-9. Measures the intensity of the acidity of the water. A normal reading for salt water is between 7.5 - 8. pH is effected by other water quality parameters such as alkalinity and CO2 levels. When pH is high, it can limit the ability of gills to transport ions essential to the fish, which can lead to osmoregulatory failure or death.

Ammonia: Safe levels: 0 - 0.1 mg/L. Ammonia is a result of fish excreting waste and metabolizing feed. It is toxic to the fish. Levels that remain high (+5ppm) for a long or short period will stress the fish and make them more susceptible to other pathogenic bacteria and viruses present in the system. Low levels of ammonia (1ppm) that persist for an extended period of time can have an overall negative effect on the fish as well. Fish will become stressed from the toxic ammonia in their water, which will allow them to be more susceptible to acquiring a disease.

Nitrite: Safe levels: 0 - 1 mg/L. Nitrite is a toxic form of nitrogen. It is the result of the nitrifying bacteria Nitrosomonas breaking down ammonia. When it is present in high concentrations, it will stress the fish and allow them to be more susceptible to pathogenic bacteria and viruses present in the system. Also, when nitrites oxidize the iron in the blood, it enables the blood to bind oxygen and carry it to the tissues.

Nitrate: Safe levels: up to 40 mg/L. Nitrate is the end result of the conversion by the nitrifying bacteria Nitrobacter and is considered to be non-toxic to fish. If nitrates are continually present in an over abundant amount (+150 mg/L), osmoregulatory failure can occur in the fish.

Dissolved Oxygen (DO): Safe levels: 7 - 9 mg/L. This is the amount of oxygen available to the fish in the water. This is an important parameter. Low DO concentration levels can have adverse effects of fish health including respiratory stress, tissue hypoxia and eventually death. The saturation point of the water is dependent on the temperature.

Alkalinity: Safe levels: 90- 150 mg/L. This is the measurement of the total concentration of basic substances dissolved in the culture water. Alkalinity serves as a buffer to the culture system and does not allow wide swings in the pH to occur.

Carbon dioxide (CO2): Safe levels: 0 - 8 mg/L. CO2 in tanks is present due to fish respiration and metabolism. Adverse effects of carbon dioxide are affected by temperature and DO. CO2 toxicity will increase when DO is low. Increased water temperatures decrease CO2 toxicity by decreasing its solubility. Also, if the fish become stressed, they respire at a high pace, which produces more CO2. If the level of CO2 in the blood rises, the oxygen carrying capacity will decrease causing respiratory distress because little oxygen is being transported to the tissues.

Salinity: Salinity should be within 2 ppt of the life history requirements for the culture fish and eelgrass.

Temperature: The temperature of your system should be maintained at +/- 1 degree of the temperature required for the fish and eelgrass that was found in the research about the species you are raising. The use of a heater or a chiller may be necessary to maintain the desired temperature throughout the year. Fluctuations of temperature will stress the system and allow the species being grown to be susceptible to pathogenic bacterial and viral infections. Having temperature control over the whole culture room is important as well. A temperature change in the culture water of more than 5 degrees in a period of 2 hours can cause fish health problems as well as hinder their growth due to stress. Continuous temperature changes to the culture water should be avoided because the fluctuating temperature will continuously stress the fish and plants.

Balance Between Humans and Nature: Eelgrass