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Biological Cycles in Aquaria: An Introduction

The Nitrogen Cycle. . Nitrification - the traditional scheme. . Ammonia (NH ). Nitrate (NO ). . Nitrobacter. Nitrite (NO ). Nitrosomonas. . . 3. 2 . 3. . . NOT EXACTLY --- But we will come back to this. Chemical Process. . Ammonia OxidationNH3 O2 H20 2e- ---> NH2OH H2ONH2OH H20 ---> NO2- 5H H2ONitrite OxidationNO2- H2O ---> NO3- 2H 4e- .

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Biological Cycles in Aquaria: An Introduction

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    1. Biological Cycles in Aquaria: An Introduction Timothy A. Hovanec, Ph.D. Chief Science Officer Marineland Aquatic Research Labs 6100 Condor Cr. Moorpark, CA 93021 805.553.4446 fax 805.529-0170 hovanec@marineland.com

    4. Chemical Process Ammonia Oxidation NH3 + O2 + H20 + 2e- ---> NH2OH + H2O NH2OH + H20 ---> NO2- + 5H+ + H2O Nitrite Oxidation NO2- + H2O ---> NO3- + 2H+ + 4e-

    6. Denitrification - An “Anaerobic” Process Almost all are facultative, denitrification is a second choice Researchers use various ways to measure and report oxygen conc. Ps. denitrificans < 0.2 ppm Ps. aeruginosa < 0.4 mM O2/L/min

    7. Potential Problems Incomplete denitrification stops at nitrite toxic to fish toxic to nitrifying bacteria Goes wrong way get ammonia production High levels of dissolved organic carbon promotes heterotrophic bacteria compete with the nitrifiers inhibits the nitrifiers Build-up of sulfide can be lead to H2S harmful to fish & nitrifiers

    8. “Anammox” Process Anaerobic Oxidation of Ammonium NH4+ + NO2- -----> N2 + 2H2O Nitrate reduction to nitrite and a coupling of the ammonium and nitrite by Planctomycetes Anaerobic process but organics not needed Carbon is from carbon dioxide Energetically more efficient than denitrification Offshore marine sediments dominated over denitrification Nearshore (bays) denitrification dominated Nature 400:446-449 AEM 61:1246-1251 AEM 68:1312-1318 http://www.anammox.com/research.html

    9. Silicon Always found combined with oxygen Silicon dioxide (SiO2) or Silica Presence/Absence effects composition of plankton 100x fold reduce = few diatoms and radiolaria requirement for some deep sea sponges In Ocean amorphous silica is usually the weak acid Silicic Acid Conc. ranges from <1 umol/Kg to 210 umol/kg At pH of 8.2 only about 5% ionized

    10. Choose Your Poison?? Diatoms can cover the displays Cyanobacteria can form carpets over everything Green algae can turn the water and displays into soup Since these organisms are benthic UV, ozone, etc cannot eradicate them - is there a biological solution?

    11. Relationship of N:P Dr. David Karl Univ. of Hawaii Aloha Station Research Cyanobacteria fix dinitrogen from the air so by removing all the nitrogen in water may promote cyanobacteria Redfield ratio of 16:1 N:P molar ratio If ratio greater than 16:1 - cyanobacteria will dominate However, if allow phosphorus than green algae will dominate rather than the cyanobacteria Measure TP, TN and TOC not just SRP and inorganic nitrogen

    12. Sulfate is a general concern produce hydrogen sulfide (H2S) In ocean is 2.7 g/Kg SO42- Sulfate can be an oxidant (electron acceptor) like oxygen Transformations are mediated by bacteria and usually involve oxidation of organic matter Sulfur Reduction (facultative anaerobes) - Steps reduce sulfate to sulfur to sulfide Sulfur oxidation (aerobes and anaerobes) - Steps oxidize sulfide to sulfur to sulfate Sulfur Cycle

    14. TOC Analysis

    15. What is DOC in the Ocean? The Answer - No one knows! Only about 20-30% of the TOC has been determined <5% is particulate. The rest is dissolved - DOC Contains vitamins biotin, thiamine and B12. Which are from cells in the water, can persist in the water. Volatile: carbon dioxide, dimethyl sulfide, methane, ethene Fatty acids, lipids, amino acids, sugars: less than 1% of the DOC. Does contain fructose, galactose and glucose Humic Acids - not the same as those in soils or freshwater. May be 20-40% of the total DOC but there are analytical problems. Probably mostly nonpolar and anionic.

    16. Coral Reef Carbon Production and Recycling

    17. Mahalo to the Lab Staff

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