Environmental Factors Flashcards
Define poikilotherm
Cold-blooded, rely on external sources for temperature regulation.
As a general rule, a change in temperature should be limited to what? Can fish tolerate larger shifts? How do ZF compare?
+/- 1.5C/day, although many aquatic organisms can tolerate later shifts in temp well after an initial shock and brief period of acclimation. Zebrafish among most eurythermal, with an acclimated thermal tolerance of 6.7-41.7C.
How does temperature impact metabolism and oxygen demand?
Increased temp speeds up metabolism and increases oxygen demand. Metabolic rate doubles for each 10C increase in temperature. ZF larvae less tolerant.
What is the outcome of maintaining life support systems at slightly lower temperatures?
Increase available oxygen, reduce need for food, and minimize losses due to accidental temp increases. Lower temps decrease rate of growth and development.
How does temperature impact reproductive/hormonal induced activity?
Temp change (usually an increase) is a factor in initiation of repro activity or other hormonal induced activity.
At what temperature should the ambient room be maintained? Why? Room temperatures should not be maintained above what temperature? Why?
At least 1-2 degrees above that of the containment system water to prevent condensation of water on the external surface of the aquaria, walls, and floors, which can serve as a medium for mold or fungi and negatively impact air quality. Do not exceed room temperatures of 80F (27C) due to cost, lower dissolved oxygen saturation, higher metabolic rate of fish, and lab worker discomfort.
Describe the oxygen content at the air-water interface.
Slightly higher, thus why fish gasp or sip at the water surface with low oxygen concentration.
What can result in supersaturation of water?
Massive aeration, rapid heating of cold water, cavitating water pumps, air stones placed too close to the water pump inflow lines
In general, sufficient aeration can be provided by what? Oxygen diffusion is adequate to what depth?
Maintaining appropriate circulation. Oxygen diffusion adequate up to 4 inches.
As a general rule for recirculating aquaculture systems, how often should the tank water be turned over?
One complete turnover per hour.
Compressed air may be added to the recirculating system, usually at what point?
Within the filtration zone.
What is a disadvantage of providing compressed air to water?
Is often hot and dry, which accelerates evaporation. Air bubbling into aquaria can produce a fine mist that acts as a fomite and aids in transmission of pathogens. Mists can also corrode metal components, resulting in scale that can build up and drop into tanks resulting in increased levels of toxic metals.
How can the introduction of scale or rust from metallic components of an aquaculture system be prevented?
Regularly evaluate components. Seal with an appropriate protectant or paint. Replace components or scrape routinely.
What pH range do ZF prefer? What are negative outcomes of higher and lower pH?
7-8. pH > 8 = Higher concentrations of toxic unionized ammonia. pH <5 = Inhibits activity of nitrifying bacteria, increasing total ammonia levels due to accumulation
In closed recirculating systems, how does the pH normally trend?
Gradually decrease due to production of acids during nitrification process as ammonia is converted to nitrate. Also decreases in poorly aerated systems due to production and accumulation of CO2 by respiring fish.
