Effects of differential hillslope‐scale water retention characteristics on rainfall–runoff response at the Landscape Evolution Observatory

Hillslopes turn precipitation into runoff and thus exert important controls on various Earth system processes. It remains difficult to collect reliable data necessary for understanding and modeling these Earth system processes in real catchments. To overcome this problem, controlled experiments are being conducted at the Landscape Evolution Observatory at Biosphere 2, The University of Arizona. Previous experiments have revealed differences in hydrological response between 2 landscapes within Landscape Evolution Observatory, even though both landscapes were designed to be identical. In an attempt to discover where the observed differences stem from, we use a fully 3‐dimensional hydrological model (CATchment HYdrology) to show the effect of soil water retention characteristics and saturated hydraulic conductivity on the hydrological response of these 2 hillslopes. We also show that soil water retention characteristics can be derived at hillslope scale from experimental observations of soil moisture and matric potential. It is found that differences in soil packing between the 2 landscapes may be responsible for the observed differences in hydrological response. This modeling study also suggests that soil water retention characteristics and saturated hydraulic conductivity have a profound effect on rainfall–runoff processes at hillslope scale and that parametrization of a single hillslope may be a promising step in modeling rainfall–runoff response in real catchments.     

Colloid transport and distribution in the hyporheic zone

Colloids moving from the stream into the hyporheic zone may have a negative impact on aquatic ecosystems as they are potential contaminants or carriers of contaminants. Moreover, retained colloids in the hyporheic zone could not only reduce the exchange flux between the stream and streambed but also change the conditions of the bed, affecting the habitats for aquatic organisms. Previous studies focused on the exchange flux across the sediment–water interface, but the colloid transport processes and distribution of retained colloids in the streambed have received little attention. We conducted experiments within a laboratory flume to examine these processes in a streambed driven by bedform‐induced hyporheic flow. Retained colloids measured in the bed at the end of the experiments revealed colloid retention mainly in the shallow layer of hyporheic zone (0–5 cm below the interface). The results demonstrated significant effects of particle trapping and settling on the colloid transport and distribution in the streambed. Retention leads to the formation of a colloid‐filled shallow layer in the bed. Particle paths based on model simulations showed that colloid settling in pore water modifies the direction of colloid transport and allows the colloid particles to move more deeply in the bed.     

Tsunami travel times to New Zealand

A table is given for the intervals between the time that a tsunami propagating radially from a distant source first reaches a position 600 nautical miles from Wellington and the times when the tsunami first reaches any of 11 selected places in New Zealand.     

Territorial behaviour in brown trout (Salmo trutta L.)

The recapture of tagged brown trout (Salmo trutta L.) in two experimental streams gave over 60% recapture in the section of stream where they were released, and over 80% when adjacent areas were included. Operation of a downstream trap showed that there was little emigration from the area above the trap and it is concluded that most of the fish which disappear die.     

Impact of overlying water velocity on ammonium uptake by benthic biofilms

The effect of the overlying water velocity on ammonium (NH₄⁺) uptake by benthic biofilms was studied in a recirculating laboratory flume (260 cm long, 29 cm wide), packed with 5 cm of silica sand arranged into bedforms. NH₄⁺ uptake was determined as the reduction in NH₄⁺ concentration in the water at average overlying water velocities of 0.8, 2, 4 and 8 cm s^?1. NH₄⁺ uptake was relatively constant under laminar flow conditions but increased when the flow regime became turbulent (>4 cm s^?1). This pattern was observed for two biofilms differing in their total biomass and in the abundance of the ammonia‐oxidizing bacteria, thus indicating that NH₄⁺ uptake was strongly controlled by mass‐transfer processes. The near stoichiometric relationship between the rates of NH₄⁺ uptake and nitrate (NO₃^?) accumulation suggests that aerobic nitrification was the main route for NH₄⁺ uptake. Microelectrode measurements showed a sharp decline of oxygen concentrations and pH values within the biofilms, thus supporting strong nitrification activity within the surficial section of the benthic biofilms. The results of this study highlight the key role of hydrodynamic conditions in regulating NH₄⁺ uptake in the transition from laminar to turbulent flow conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Environmental Factors Affecting the Occurrence and Production of the Spring Phytoplankton Bloom in Funka Bay, Japan

The concentration of nutrients was measured during the spring phytoplankton bloom in Funka Bay over a 5-year period (1988–92). During the winter mixing period, nutrient concentrations were similar in every year except in 1990 when a high concentration of silicate was observed. There was interannual variation in the onset of the bloom, presumably depending on the stability of the water column. The bloom developed in early March when the Oyashio water (OW), which has a lower density than the existing winter water, flowed into the bay and the pycnocline formed near the bottom of the euphotic zone. In this case, high chl a was found only in the euphotic zone and nutrient utilization was limited to this zone. In the year when the inflow of OW was not observed by April, the bloom took place at the end of March without strong stratification and high chl a was found in the whole water column, accompanied by a decrease in nutrients. Interannual differences were found not only at the beginning of the decrease, but also in the thickness of the layer which showed a decrease in nutrients. Primary production from the beginning to the end of the spring bloom was estimated from the nutrient budget before and after the spring bloom. The integrated production over the spring bloom period ranged from 25 to 73 g C m^-2, which accounts for 19–56% of the annual production in this bay. We found that the timing of the bloom was strongly dependent on the inflow of OW, but the amount of production was not clearly related to this timing.     

防城湾水质特征及营养状况趋势研究

根据1983—1984年度、1990年度及1996——1997年度3个不同时期的调查研究资料，分析研究了防城湾的水质特征及其营养状况。结果表明：该湾水体中的盐度、pH呈明显下降趋势，而有机污染物含量则呈上升趋势，其余因子无明显规律性变化；但相关分析显示，陆源输入对各化学因子具有主导控制作用，生物同化作用次之。N、P、Si营养盐中，N为1983—1984年度初级生产力的限制因子：1990年度演化为P和Si;1996—1997年度N、P、Si均呈充足状态，尤以Si最为显著。通过污染指数A及营养状态指数E的统计分析，该湾水质具有向污染型及富营养型演化的明显趋势。     

海脉冲营养素营养成分的分析

对利用扇贝边研制成的新的海洋保健品—海脉冲营养素的营养成分进行分析。结果表明,海脉冲营养素富含氨基酸,无机元素,微量元素和维生素等;糖元,VB12等含量丰富。本实验的分析结果可为海脉冲营养素的临床应用提供科学依据。     

The Irish Sea: Is it eutrophic?

The question of whether the Irish Sea is eutrophic is addressed by reviewing the evidence for anthropogenic nutrient enrichment, elevated phytoplankton production and biomass and undesirable disturbance in the context of the EU and OSPAR definitions of eutrophication. Winter concentrations of dissolved available inorganic phosphate (DAIP), nitrogen (DAIN as nitrate and nitrite) and silicate (Si) in coastal waters and concentrations of DAIP and Si in offshore waters of the Irish Sea are elevated relative to winter Celtic Sea shelf break concentrations (0.5 μM DAIP, 7.7 μM DAIN and 2.7 μM Si). Significant, negative nutrient salinity relationships and analysis of the Isle of Man nutrient time-series indicate that the elevated Irish Sea levels of DAIP and DAIN are the result of anthropogenic enrichment with highest concentrations (≈2.0 μM DAIP, 30 μM DAIN and 17 μM Si) measured in near shore eastern Irish Sea waters.     

Open Ocean Originated Phosphorus and Nitrogen in the Seto Inland Sea,Japan

The ratios of phosphorus and nitrogen originating from land and the open ocean in the Seto Inland Sea, which is the largest semi-enclosed coastal sea in Japan, have been estimated from data on total phosphorus and nitrogen loads and observed concentrations of total phosphorus and nitrogen. The ratios of land-origin and open-ocean-origin total phosphorus and nitrogen in the Seto Inland Sea are 0.28:0.72 and 0.19:0.81, respectively.