SPECTRAL ANALYSIS OF TIDAL FLUCTUATIONS IN GROUND WATER LEVEL1

ABSTRACT: Water level data at 16 ground water wells and two sea water gauging stations, coupled with barometric measurements in an alluvial plain in the central‐west region of Taiwan, are analyzed using spectral analysis in the time and frequency domains. The semi‐diurnal component from water level station is observed to be the most noticeable signal while the diurnal component is the less distinct signal recorded at the water level stations. Both semidiurnal and diurnal components are coupled with atmospheric pressure measurements. From the atmospheric pressure data, spectral analysis indicates that both the raw and the pressure adjusted water levels are almost in phase and retain the same amplitude in this area. It implies that the effect of pressure variations is not significant for the sea water and ground water level nearby; the astronomical tidal components, as expected, are the main factor causing fluctuation of ocean water and ground water levels in the Choshuihsi alluvial plain.     

植物N/P与土壤pH值对湿地植物物种丰富度的影响

通过人工控制模拟试验,研究了植物中全氮与全磷之比(植物N/P)和土壤pH值与湿地植物物种丰富度的关系.结果表明,湿地物种丰富度与植物N/P之间呈单峰变化关系,当2.09.5时,氮、磷供应平衡系统可能被破坏,湿地物种逐渐减少.物种丰富度与土壤pH值表现为显著的正相关关系(R²=0.526),当pH值为5.6～6.8时,物种丰富度随着土壤pH值增加而增加.通过方差分析,土壤pH值和植物N/P对物种丰富度的影响分别为37.96%和15.29%.     

大型海藻栽培及其在近海环境的生态作用

作为重要自然资源的大型海藻可食用、作为饲料、工业原料和有机肥料,是具有较高价值的商品。因此,世界上许多国家都在大力发展大型海藻栽培业。当前,近海水域营养超负荷是世界上普遍存在的环境问题。一些栽培的大型海藻,生产力很高,在生长过程中可大量吸收N、P营养物质,是海洋环境中重要的生物过滤器。此外,大型海藻在碳循环研究、赤潮控制和维持健康的复合养殖系统方面也有很重要的作用,是非常重要的生态环境材料。为保障近海水安全和生态系统健康,大规模栽培大型海藻是重要的生态对策。     

Contribution of Spartina maritima to the reduction of eutrophication in estuarine systems

Salt marshes are among the most productive ecosystems in the world, performing important ecosystem functions, particularly nutrient recycling. In this study, a comparison is made between Mondego and Tagus estuaries in relation to the role of Spartina maritima in nitrogen retention capacity and cycling. Two mono-specific S. maritima stands per estuary were studied during 1 yr (biomass, nitrogen (N) pools, litter production, decomposition rates). Results showed that the oldest Tagus salt marsh population presented higher annual belowground biomass and N productions, and a slower decomposition rate for litter, contributing to the higher N accumulation in the sediment, whereas S. maritima younger marshes had higher aboveground biomass production. Detritus moved by tides represented a huge amount of aboveground production, probably significant when considering the N balance of these salt marshes. Results reinforce the functions of salt marshes as contributing to a reduction of eutrophication in transitional waters, namely through sedimentation processes.     

CHemical and Biological Assessment of an Urban, Estuarine marsh in Northeastern New Jersey USA

Oritani Marsh in the Hackensack Meadowlands of urbanized northeastern New Jersey USA was assessed in 2000 for vegetation, soil/sediment chemistry, abundance/diversity of benthic invertebrates, and bird and mammal usage. Vegetatively, both marsh and uplands are dominated by tall, dense Phragmites australis. Small patches (less than 2 hectares total) dominated by Spartina spp. were found at the lowest elevations. Soil/sediment cores were sliced into 5 intervals and analyzed for metals, pesticides and volatile/semivolatile organic compounds. Thirteen locations had at least one chemical above Long et al.’s [Environmental Management, 19, 1995, 81--97] “Effects Range-Median” (ERM). Seven metals and nine organics exceeded ERM in at least one sample, with mercury showing the most exceedances. The surface 15 cm interval was generally more contaminated with metals than the 15 to 30 cm interval; the reverse was true for semivolatile organic compounds. Twenty taxa of benthic macroinvertebrates were collected, with each location producing from 1 to 9 taxa. Abundance ranged from 11 to 3,889 individuals/m². Number of taxa was moderately (r ² between 0.40 and 0.70) negatively correlated with zinc, beryllium, nickel and arsenic concentrations; no other chemical’s r ² was above 0.25. Diversity was moderately negatively correlated with arsenic and beryllium. These correlations were unexpected: zinc, beryllium, nickel and arsenic were not the chemicals found at the highest concentrations relative to benchmarks. Number of taxa, abundance and diversity were moderately (negatively) correlated with elevation; organic carbon was moderately (positively) correlated with abundance. All other correlations were weak (r ² < 0.35). Live traps captured only one mammal species, the meadow jumping mouse. Bird observations revealed 39 species, dominated by a few common species.     

Effect of field exposure to 38-year-old residual petroleum hydrocarbons on growth, condition index, and filtration rate of the ribbed mussel, Geukensia demissa

In September 1969, the Florida barge spilled 700,000 L of No. 2 fuel oil into the salt marsh sediments of Wild Harbor, MA. Today a substantial amount, approximately 100 kg, of moderately degraded petroleum remains within the sediment and along eroding creek banks. The ribbed mussels, Geukensia demissa, which inhabit the salt marsh creek bank, are exposed to the spilled oil. Examination of short-term exposure was done with transplantation of G. demissa from a control site, Great Sippewissett marsh, into Wild Harbor. We also examined the effects of long-term exposure with transplantation of mussels from Wild Harbor into Great Sippewissett. Both the short- and long-term exposure transplants exhibited slower growth rates, shorter mean shell lengths, lower condition indices, and decreased filtration rates. The results add new knowledge about long-term consequences of spilled oil, a dimension that should be included when assessing oil-impacted areas and developing management plans designed to restore, rehabilitate, or replace impacted areas.     

植物对沼泽湿地生态系统N2O排放的影响

利用静态暗箱/气相色谱法连续3个生长季(2003-2005年)对三江平原小叶章草甸和毛果苔草沼泽N2O排放通量进行野外对比观测试验.结果表明,植物不同生长阶段对湿地生态系统N2O排放通量的影响不尽相同.植物的参与促进了湿地生态系统N2O的排放,2003-2005年生长季小叶章草甸土壤-植物系统N2O排放通量分别是土壤表观N2O排放通量的1.58倍、2.09倍和2.34倍,同期毛果苔草沼泽土壤-植物系统N2O排放通量分别是土壤表观N2O排放通量的1.86倍、1.50倍和1.33倍.3个生长季小叶章草甸N2O排放通量均大于毛果苔草沼泽,这主要是由土壤理化性质的空间变异性以及水文情况的差异造成的.     

历史灾害资料在当前减灾工作中大有作为：—以1862年珠江三角洲的风暴潮为例

本文从历史资料中分析出1862年7月27日珠江三角洲的特大风暴潮,潮位可能高达7.6～8.5m,远远超出应用15a观测资料外推的1000a一遇潮位2.86～5.11m,证明历史灾害资料在当前减灾工作中可发挥重大作用。     

中国北黄海发生的两次海洋褐胞藻赤潮

１９９３年８月中旬和１９９５年８月中旬，中国北黄海近岸各发生一次海洋褐胞藻赤潮。调查结果为海洋褐胞藻的生物量为（１．７－１１．７）×１０＾８个／ｍ＾３，浮游植物群落生物量范围为（２．５－１５．４）×１０＾８／ｍ＾３。赤潮海区的表层水温２５．８℃，盐度１２－１７．６，ｐＨ８．５－８．６，透明度１．５－１．６ｍ。大量富含营养物质的陆源淡水入海，可能是这一海区海洋褐胞藻赤潮的主要起因。     

近岸海域叶绿素和赤潮的AVHRR波段比值探测方法研究

提供了利用NOAAAVHRR的短波波段探测近岸海域叶绿素和赤潮的方法。本方法采用AVHRR的波段1(580～680nm)和波段2(720～1100nm)之间的比值水色因子C21[C21=(R2-Ra2)/(R1-Ra1)],建立了C21与辽东湾海域现场测定的叶绿素a之间的相关关系,相关系数为0.75。叶绿素a的最小探测浓度为2.22mg/m3,探测精度为±4mg/m3,同时也讨论了叶绿素探测的影响因素。