Nutrient (C, N, and P) concentration changes were measured in surface runoff and shallow groundwater as they moved through a small agricultural (cropland) watershed located in Maryland. During the study period (March 1981 to March 1982), dramatic changes in water-borne nutrient loads occurred in the riparian forest of the watershed. From surface runoff waters that had transited : 50 m of riparian forest, an estimated 4.1 Mg of particulates, 1I kg of particulate organic-N, 0.83 kg of ammonium-N, 2.7 kg of nitrate-N and 3.0 kg of total particulate-P per ha of riparian forest were removed during the study year. In addition, an estimated removal of 45 kg ha- yr-t of nitrate- N occurred in subsurface flow as it moved through the riparian zone. Nutrient uptake rates for the cropland and riparian forest were estimated. These systems were then compared with respect to their pathways of nutrient flow and ability to retain nutrients. The cropland appeared to retain fewer nutrients than the riparian forest and is thought to incur the majority of its nutrient losses in harvested crop. The dominant pathway of total-N loss from the riparian forest seemed to be subsurface flux. Total phosphorus loss from the riparian forest appeared almost evenly divided between surface and subsurface losses. Nutrient removals in the riparian forest are thought to be of ecological significance to receiving waters and indicate that coupling natural systems and managed habitats within a watershed may reduce diffuse-source pollution.

Nutrient dynamics in an agricultural watershed: Observations on the role of a riparian forest

Early diagenesis in a reducing fjord, Saanich Inlet, British Columbia—I. chemical and isotopic changes in major components of interstitial water

Vertical distribution of chlorophyll and phaeo-pigments : Baja California

Observations in Lake Nitinat, an anoxic fjord on Vancouver Island, British Columbia, indicate that the large accumulations of ammonia, carbonates, phosphates, silicates, and sulfides in the deep water are the result of oxidative and fermentative decomposition of organic matter of planktonic origin, the reduction of sulfate ions, hydrolytic or other non-oxidative release (in the case of silicates), and the solution of carbonates (which also increases the alkalinity). Ammonia, sulfides, and silicates accumulate in the sulfide zone in direct proportion to each other, but some of the phosphate is probably released from the organic matter earlier than the other components, and some of the phosphate may be precipitated onto the bottom. Methane was observed in the anoxic waters, suggesting that some decomposition takes place by anaerobic fermentation. The concentrations of ferrous and sulfide ions are probably controlled by the solubility of ferrous sulfide. The vertical distribution of sulfides can be described by a mathematical model that can be simplified to one dimension because horizontal advective and diffusive terms can be neglected.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1965.10.suppl2.r185

Some consequences of the decomposition of organic matter in lake nitinat, an anoxic fjord1

Mean surface concentrations of nitrogenous nutrients and phosphate are reported for various areas in the northcastcrn tropical Pacific Ocean. Except at the Costa Rica Dome, an area of upwelling, nitrate concentrations were very low. NOs: Poe’ratios were also generally low and phytoplankton might remove all of the nitrate while appreciable concentrations of phosphate were still present. Measurements of nitrate during growth of batch cultures of Gymnodinium simplex showed that concentrations below approximately 5 pg-at./ liter probably limited the rate of growth of this dinoflagellate. Since surface nitrate concentrations were generally lower than this value, the rate of growth of G. simplex would be limited over much of the arca, unless sources of nitrogen other than nitrate were available. Ammonia and labile amino nitrogen were measured as one nitrogen fraction in one offshore water mass northwest of the Dome. The ammonia concentration was greater than that of nitrate and the N : P ratio was increased threefold to fourfold if ammonia was included with nitrate, The growth of three phytoplankton cultures was supported by ammonia and by various amino compounds. Ammonia may be a relatively important nitrogen source in the northeastern tropical Pacific Ocean, and should be included with nitrate as a measure of the total nitrogen available to phytoplankton. Ammonia may moderate the extreme nitrogen deficiency which would be expected if nitrate were considered the only source of nitrogen.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1966.11.3.0393

Surface nitrogenous nutrients and phytoplankton in the northeastern tropical pacific ocean 1

: A new method has been developed for the determination of small concentrations of ammonia and labile amino compounds in distilled, fresh, and seawater. It employs the oxidation of these compounds to nitrite by sodium hypochlorite in strongly basic solution. The excess sodium hypochlorite is reduced with sodium arsenite solution, and the nitrite is then determined by a calorimetric method. Bromide and iodide ions catalyze the oxidation. The precipitation of calcium and magnesium hydroxide from seawater samples by the base does not interfere with the determination. (Author)

Richard A. Kletsch

Papers

The spectrophotometric determination of ammonia and labile amino compounds in fresh and seawater by oxidation to nitrite

Spectrophotometric determination of fluoride in seawater