하구및 연안생태Coastal management 2014 년 가을학기

Nutrient patterns with depth NH4+, PO4; increase with depth; slow upward diffusion NO3-; 0~5 cm peak; nitrification Decrease with depth; if water column is high Similar trends in water column; when sediment is a major source; mixing breaks these trends

Chemical kinetics Rates of transformation should be known Transformation between : organic-inorganic, oxidation state.

Nutrient assimilation Photosynthesis Various organisms compete for nutrients Lower Ks has greater affinity High Ks has advantage in high concentration The Ks values are similar to the ambient concentrations of summer period of peak growth !!!

Nutrient assimilation Macrophytic plants have higher Ks; transport of ions across epidermal surface; usually have roots, so high K2 is not a big problem Plants have adapted to the respective concentration

Nutrient regeneration Enzymatic decomposition by microorganisms (bacteria and fungi) Redifield ratio release of nutrients Silicate: dissolution of tests Si:P=15:1 Decomposition occurs in sediment rather than water column

Nutrient regeneration Aerobic versus anaerobic Exponentiall decreasing NH4 production with sediment depth O2 is preferable Fresh OM is readily metabolized 9 times more NH4 by O2 respiration compared to SO4 reduction Overall deficiency NH4 released compared to O2 consumed O:N ratio of 12 Benthic flux with chamber experiments; NH4: 20~300 umol m-2h-1 PO43-:0~40 umol m-2h-1 20~200 % of nutrient demands for phytoplankton assimilation

Nutrient regeneration Regeneration is correlated with temperature Arrhenius type expression; other than simple temperature kinetics are involved NH4  NO3 ; nitrification PO4: reacts with iron and manganese and hydroxides to form insoluble precipitates in oxic; when anoxic, soluble Fe(MN)-PO4-3 complex are produced and released. N:P release ratio 8.4: about half that is expected (16); N is lost through nitrification-denitrification Silicon dissolution is slow compared to N, P: late summer dominance of dinoflagellate is a result of reduced Si availability (?)

Excretion Zooplankton (phytoplankton) excretion N : ammonium and dissolved organic N(urea, uric acid, amino acid) P: dissolved organic phosphorus Si: no excretion, but uptake by zooplankton can enhance dissolution. Metazoan zooplankton excrete through gills and antennal glands Protozoa: cell wall

Excretion N, P excretion measurements Nutrient Conc. Change with zooplankters; various nutrients at the same time; can not apply in situ; what if uptake takes place at the same time? Isotopic tracers(33P, 32P, 15N) Excretion rates :Directly proportional to respiration zooplankton C:N:P=30:9:1 ; oxidation of food (phytoplankton) is not complete !! Function of temperature Feeding rates; increase in starvation and high feeding Excretion rates per unit weight of zooplankton are inversely proportional to the size of individual zoo plankton; organisms associated with particulates < 32uM accounts for most of release Excretion versus remineralization Importance vary seasonally and inshore-offshore direction Water-column regeneration in oceanic waters; and even 7~8 m Excretion is important in shallow water (benthic regeneration is also important) N, P assimilation by bacteria can be important