World Aquaculture September 2018

WWW.WA S.ORG • WORLD AQUACULTURE • SEP TEMBER 2018 33 useful in the class are provided for independent study by the students, and one or more graduate students (who are studying aquaculture water quality) teach a review session weekly. The students typically enter the water quality course with the be- lief that they have at least a “talking knowledge” of the subject. I give a basic, preliminary test (see text box) to ascertain their water quality knowledge. The best score ever on this test was nine correct out of 20 questions. I have provided the answers to the test for reference by any readers willing to assess their general water quality knowledge. Memorization of important factors about a subject is desirable, but memorization does not assure an ability to use facts and principles to reach logical answers to questions or to solve problems. Therefore, tests in the course are “open book” and students must use informa- tion presented in the lectures to arrive at solutions to test questions. Calculations are necessary for answering about half of the questions. Because test questions cannot be answered by recalling lecture infor- mation frommemory, many students do poorly on the first test despite having been advised that logic and problem solving will be required. The course has always been attended by a mixture of 30-40 percent undergraduates and 60-70 percent graduate students and, as would be expected, most graduate students make higher scores than most undergraduates, and scores are ranked separately. Many interna- tional graduate students have studied aquaculture at Auburn Universi- ty, and a large percentage of them took the general water quality class. Declining Enrollment of Students inWater Science A total of 1,341 fisheries and aquaculture students took theWater Science class at Auburn University between 1972 and 2017. This number is approximately 80 percent of the fisheries and aquaculture graduates over that 46-yr period. However, enrollment has been declining, for reasons that are unclear. The emphasis today is on “cutting-edge” science (whatever that is supposed to mean) and “novel” science (that seems even harder to define) that is published in “high impact” journals. Water science and water quality are neither “cutting-edge” nor “novel” courses. Graduate programs typically do not have specific course requirements, and courses are selected according to the desires of the student, the major professor and graduate committee members. Researchers on graduate committees have become very specialized, reflecting the current trend in science. Thus, many committees overlook the importance of fisheries and aquaculture students taking courses related to water quality and environmental management. The upshot is that there appears to be a declining interest in teaching water quality and environmental topics in aquaculture. Note Claude E. Boyd, Professor Emeritus, 131 Aquatic Resource Management Building, Auburn University, AL 36849; boydce1@ auburn.edu General Water Quality Knowledge Assessment 1. Which water quality variable is defined as the total concentration of bases expressed as equivalent CaCO 3 ? 2. Which water quality variable is defined as the total concentration of divalent cations expressed as equivalent CaCO 3 ? 3. What is the numerical value of the dissociation constant of water (K w ; H 2 O = H + + OH - ) at 25°C? 4. Above what pH does water not contain free carbon dioxide? 5. What is the average salinity of seawater in milligrams per liter? 6. What is the percentage saturation of molecular oxygen in water at equilibriumwith atmospheric air? 7. At what temperature does 1 m 3 of freshwater weigh 1.0000 metric ton (tonne)? 8. Name the biological process in which ammonia is oxidized to nitrate. 9. Estimate the weight in kilograms of residue remaining after evaporation of 1 m 3 of water that contains 1 part per thousand (ppt) of total dissolved solids. 10. List the pH above which freshwater may contain measurable carbonate (CO 3 2- ). 11. What is the approximate dissolved oxygen concentration at saturation (in milligrams per liter) for freshwater at mean sea level and at 20 o C? 12. Humic substances in water trace metals. 13. List a major cation found in natural water: 14. List a major anion found in natural water: 15. 1 mg/L NO 3 -N contains a. more, b. less, c. same amount of nitrogen as 1 mg/L NO 3 . 16. Name one of the two nutrients most commonly associated with eutrophication: 17. In aerobic respiration, howmany grams of molecular oxygen are necessary to completely oxidize 1.00 g of organic carbon? 18. What is the numerical value of the factor relating the total amount of organic carbon produced in photosynthesis to the total amount of oxygen released? 19. What is the pH belowwhich water is often said to contain mineral acidity? 20. Aluminum ion in water releasing H + . Answers in order: total alkalinity; total hardness; 10 -14 ; 8.3; 34,500; 100 percent; »4°C; nitrification; 1.0; 8.3; 9.08; chelate Ca, Mg, K. or Na ac- ceptable; SO 4 , Cl, HCO 3 - acceptable; more; nitrogen or phosphorus; 2.67; 0.375 (12/32); 4.5; hydrolyzes.