Quantifying and Evaluating Ecosystem Health: A Case Study from Moreton Bay, Australia

As part of the program monitoring the ecosystem health of Moreton Bay, Queensland, Australia, we developed a means for assessing ecosystem health that allows quantitative evaluation and spatial representations of the assessments. The management objectives for achieving ecosystem health were grouped into ecosystem objectives, water quality objectives, and human health objectives. For the first two groups, aspects of the ecosystem (e.g., trophic status) were identified, and an indicator was chosen for each aspect. Reference values for each indicator were derived from management objectives and compared with the mapped survey values. Subregions for which the indicator statistic was equal to or better than the assigned reference value are referred to as “compliant zones.” High-resolution surface maps were created from spatial predictions on a fine hexagonal grid for each of the indicators. Eight reporting subregions were established based on the depth and predicted residence times of the water. Within each reporting subregion, the proportion that was compliant was calculated. These results then were averaged to create an integrated ecosystem health index. The ratings by a team of ecosystem experts and the calculated ecosystem health indices had good correspondence, providing assurance that the approach was internally consistent, and that the management objectives covered the relevant biologic issues for the region. This method of calculating and mapping ecosystem health, relating it directly to management objectives, may have widespread applicability for ecosystem assessment.     

DRY AND WET WEATHER FLOW NUTRIENT LOADS FROM A LOS ANGELES WATERSHED1

Effective watershed management requires an accurate assessment of the pollutant loads from the associated point and nonpoint sources. The importance of wet weather flow (WWF) pollutant loads is well known, but in semi‐arid regions where urbanization is significant the pollutant load in dry weather flow (DWF) may also be important. This research compares the relative contributions of potential contaminants discharged in DWF and WWF from the Ballona Creek Watershed in Los Angeles, California. Models to predict DWF and WWF loads of total suspended solids, biochemical oxygen demand, nitrate‐nitrogen, nitrite‐nitrogen, ammonia‐nitrogen, total Kjeldahl nitrogen, and total phosphorus from the Ballona Creek Watershed for six water years dating from 1991 to 1996 were developed. The contaminants studied were selected based on data availability and their potential importance in the degradation of Ballona Creek and Santa Monica Bay beneficial uses. Wet weather flow was found to contribute approximately 75 percent to 90 percent of the total annual flow volume discharged by the Ballona Creek Watershed. Pollutant loads are also predominantly due to WWF, but during the dry season, DWF is a more significant contributor. Wet weather flow accounts for 67 to 98 percent of the annual load of the constituents studied. During the dry season, however, the portion attributable to DWF increases to greater than 40 percent for all constituents except biochemical oxygen demand and total suspended solids. When individual catchments within the watershed are considered, the DWF pollutant load from the largest catchment is similar to the WWF pollutant load in two other major catchments. This research indicates WWF is the most significant source of nonpoint source pollution load on an annual basis, but management of the effects of the nonpoint source pollutant load should consider the seasonal importance of DWF.     

BASE FLOW TRENDS IN URBANIZING WATERSHEDS OF THE DELAWARE RIVER BASIN1

Rapid land development is raising concern regarding the ability of urbanizing watersheds to sustain adequate base flow during periods of drought. Long term streamflow records from unregulated watersheds of the lower to middle Delaware River basin are examined to evaluate the impact of urbanization and imperviousness on base flow. Trends in annual base flow volumes, seven‐day low flows, and runoff ratios are determined for six urbanizing watersheds and four reference watersheds across three distinct physiographic regions. Hydrograph separation is used to determine annual base flow and stormflow volumes, and nonparametric trend tests are conducted on the resulting time series. Of the watersheds examined, the expected effects of declining base flow volumes and seven‐day low flows and increasing stormflows are seen in only one watershed that is approximately 20 percent impervious and has been subject to a net water export over the past 15 years. Both interbasin transfers and hydrologic mechanisms are invoked to explain these results. The results show that increases in impervious area may not result in measurable reductions in base flow at the watershed scale.     

Mowers versus growers: Riparian buffer management in the Southern Blue Ridge Mountains,USA

Despite long-standing knowledge of the benefits of riparian buffers for mitigating nonpoint source pollution, many streams are unprotected by buffers. Even landowners who understand ecological values of buffers mow riparian vegetation to the streambank. Do trends in rural riparian conditions reflect the development of riparian forest science? What motivates residential riparian management actions? Using high-resolution orthoimagery, we quantified riparian conditions and trends between 1998 and 2015 in the rural upper Little Tennessee River basin in Macon County, North Carolina and explored how landowners view riparian zone management and riparian restoration programs. Buffer composition in 2015 was as follows: no buffer (32.5%), narrow (19.3%), forested (26.7%), shrub (7.2%), and intermediate (7.0%). Relative to 1998, the greatest decrease occurred in the no buffer class (−17.7%, 46 km) and the largest increases occurred in the shrub (+72.5%, 20 km) and narrow (12.6%, 14 km) classes. Forested buffer marginally increased. Semi-structured interview data suggest that landowners prioritize recreational and scenic aspects of riparian buffers over ecological functions such as filtration and bank stabilization. Riparian restoration programs might be made more enticing to non-adopters if outreach language appealed to landowner priorities, design elements demonstrated intentional management, and program managers highlighted areas where ecological goals and landowner values align.     

Targeted Application of Seasonal Load Duration Curves Using Multivariate Analysis in Two Watersheds Flowing Into Lake Houston1

Teague, Aarin, Philip B. Bedient, and Birnur Guven, 2011. Targeted Application of Seasonal Load Duration Curves Using Multivariate Analysis in Two Watersheds Flowing Into Lake Houston. Journal of the American Water Resources Association (JAWRA) 47(3):620‐634. DOI: 10.1111/j.1752‐1688.2011.00529.x Abstract: Water quality is a problem in Lake Houston, the primary source of drinking water for the City of Houston, Texas, due to pollutant loads coming from the influent watersheds, including Spring Creek and Cypress Creek. Statistical analysis of the historic water quality data was developed to understand the source characterization and seasonality of the watershed. Multivariate analysis including principal component, cluster, and discriminant analysis provided a custom seasonal assessment of the watersheds so that loading curves may be targeted for season specific pollutant source characterization. The load duration curves have been analyzed using data collected by the U.S. Geologic Survey with corresponding City of Houston water quality data at the sites to characterize the behavior of the pollutant sources and watersheds. Custom seasons were determined for Spring Creek and Cypress Creek watersheds and pollutant source characterization compared between the seasons and watersheds.     

桑沟湾表层沉积物性质及对磷的吸附特征

通过研究桑沟湾表层沉积物对磷的吸附动力学曲线和吸附等温线,并结合沉积物的表面电荷性质及磷的形态分析,考察了沉积物对磷的吸附性能和吸附机制.结果表明,桑沟湾表层沉积物对磷的吸附过程包括快吸附过程和慢吸附过程,可用快慢二段一级动力学方程描述,等温线符合Langmuir交叉式模型.夏季沉积物样品的最大吸附量高于春季样品,粒级较小的沉积物吸附能力较强.沉积物样品对磷的最大吸附量Qm在0.047 1~0.123 0 mg·g-1之间,吸附/解吸平衡磷浓度(EPC0)范围在0.059 6~0.192 7 mg·L-1,沉积物充当"磷源"的作用.不同站位表层沉积物中无机磷(IP)是磷在沉积物中的主要赋存形态,吸附后的沉积物样品中弱吸附态磷(Ex-P)、铁结合态磷(Fe-P)明显增加.吸附过程包括物理吸附和化学吸附,以物理吸附为主.     

香溪河沉积物-水界面的营养盐交换特征

为研究香溪河库湾沉积物-水界面的营养盐交换特征,于2016年6月采集香溪河库湾上覆水和沉积物间隙水样品,分析不同形态氮、磷的空间分布特征并进行相关性分析,计算沉积物-水界面氮、磷的释放通量.结果表明:香溪河库湾上覆水和沉积物间隙水中ρ（TP）的变化范围分别为0.484~0.927和0.511~2.220 mg/L,ρ（TN）的变化范围分别为0.739~4.302和3.571~14.011 mg/L;上覆水和沉积物间隙水中氮、磷质量浓度在沿程和垂向上具有一定的变化规律,上游区域沉积物间隙水中氮、磷质量浓度大于下游区域,沉积物间隙水中氮、磷质量浓度明显大于上覆水;香溪河沉积物总体上表现为PO₄3--P和NH₄+-N的"源",中下游区域沉积物表现为NO₃--N的"源",而中上游区域表现为NO₃--N的"汇";PO₄3--P的释放通量范围为0.129~0.339 mg/（m2·d）,NH₄+-N的释放通量范围为0.213~1.415 mg/（m2·d）,NO₃--N的释放通量范围为-1.109~3.446 mg/（m2·d）.研究显示,上覆水的环境条件对于沉积物-水界面营养盐交换存在一定的影响,但影响程度各有不同.      

梁平县境内高滩河水质的空间分布及其对土地利用方式的响应

以梁平县境内高滩河流域为研究对象,综合应用GIS空间分析、Pearson相关分析和RDA冗余分析方法,研究在子流域尺度上COD、BOD5、氨氮和总磷4种水质要素对土地利用方式的生态响应。结果表明:高滩河流域土地利用类型对水质要素有着重要影响,林地能够改善河道水环境,旱地和城镇村和工矿用地是COD、BOD5和氨氮的主要污染来源,园地、交通运输用地以及水域对污染物的影响较弱,说明农业面源污染和农村居民生活污染是高滩河水质恶化的主要原因。     

杭州湾表层海水营养盐分布特征及富营养化状况研究

根据2015年3月和8月杭州湾的海水质量监测数据,分析了该海域的营养盐分布特征以及富营养化状况,结果表明:杭州湾表层海水无机氮变化范围为0.36~4.22 mg/L,活性磷酸盐的含量范围为0.014~1.51 mg/L,化学需氧量含量范围为0.56~3.18 mg/L.该海域无机氮和活性磷酸盐超标严重,表层海水已处于重度富营养化状态,调查站位EI均大于1.该海域表层海水无机氮、活性磷酸盐、化学需氧量和富营养化指数高值区均与陆源入海口、养殖区、排污口等人类活动影响较大的区域有关.     

太湖贡湖湾水域抗生素污染特征分析与生态风险评价

为评估太湖贡湖湾水域抗生素污染程度与生态风险,利用高效液相色谱-串联质谱检测分析了4类抗生素(四环素类、喹诺酮类、磺胺类、大环内酯类)在贡湖湾表层水的污染特征.结果表明,16种目标抗生素中,有13种在贡湖湾水体中检出,质量浓度范围为0.005~4.720μg·L-1,其中土霉素(oxytetracycline,OTC)检出浓度最高.抗生素在南北两湖湾的检出水平也互有高低,其中四环素类抗生素北部湾要高于南部湾,而喹诺酮类和磺胺类抗生素的检出量南部湾要高于北部湾.采用风险商值法进行风险评估,初步评估结果为贡湖湾水域中检出的抗生素中,处于高风险的有5种:四环素类土霉素(OTC)及喹诺酮类诺氟沙星(norfloxacin,NOR)、氧氟沙星(ofloxacin,OFL)、环丙沙星(ciprofloxacin,CIP)和恩诺沙星(enrofloxacin,ENR),占检出种类38.5%;中风险有4种:四环素(tetracycline,TC)、金霉素(chlortetracycline,CTC)、罗红霉素(roxithromycin,ROX)和磺胺甲基异噁唑(sulfamethoxazole,SMX),占检出种类30.8%;其余4种磺胺甲基嘧啶(sulfamerazine,SMR)、磺胺甲氧哒嗪(sulfamethoxypyridazine,SMP)、磺胺喹噁啉(sulfaquinoxaline,SQX)和甲氧苄氨嘧啶(trimethoprim,TMP)为低风险.评估结果表明贡湖水域抗生素存在一定生态风险,其中四环素类和喹诺酮类尤为突出,应引起足够的注意,并采取相应防范措施.