Hydrogen peroxide production in marine bathing waters: Implications for fecal indicator bacteria mortality

Hydrogen peroxide concentrations [H(2)O(2)] have been measured over the last two decades in multiple studies in surface waters in coastal, estuarine and oceanic systems. Diurnal cycles consistent with a photochemical production process have frequently being observed, with [H(2)O(2)] increasing by two orders of magnitude over the course of the day, from low nM levels in the early morning to 10(2)nM in late afternoon. Production rates range from <10 for off-shore ocean waters to 20-60nMh(-1) for near-shore coastal and estuarine environments. Slow night-time loss rates (<10nMh(-1)) have been attributed to biological and particle mediated processes. Diurnal cycles have also frequently been observed in fecal indicator bacteria (FIB) levels in surf zone waters monitored for microbial water quality. Measured peak peroxide concentrations in surface coastal seawaters are too low to directly cause FIB mortality based on laboratory studies, but likely contribute to oxidative stress and diurnal cycling. Peroxide levels in the surf zone may be increased by additional peroxide production mechanisms such as deposition, sediments and stressed marine biota, further enhancing impacts on FIB in marine bathing waters.     

Dye dispersion in the surf zone: Measurements and simple models

To examine the spatial and temporal effect of low-volume land-based runoff on beach contamination, discrete batches of dye were released at the shoreline at three beaches in Santa Monica Bay in 2000 (Malibu Creek, Santa Monica Canyon and Pico–Kenter drain). Dye concentration was measured at the shoreline 25, 50 and 100 m alongshore from the dye release point for up to 40 min after dye release. The shoreline concentration time series are characterized either by approximately exponential decay in concentration after passage of the dye patch maximum concentration or by persistent low concentration up to 30 min after passage of the initial dye patch front. In the absence of detailed measurements of physical conditions, several simple advection–diffusion models are used to simulate shoreline concentration time series for an idealized surf zone in order to probe the roles of alongshore current shear and rip currents in producing the observed characteristics in dye concentration time series. Favorable qualitative and quantitative comparison of measured and simulated time series suggest alongshore current shear and rip currents play key roles in generating the observed characteristics of nearshore dye patch dispersion. The models demonstrate the potential effects of these flow features on the extent and duration of beach contamination owing to a continuous contamination source.     

Assessing water quality in Marine Protected Areas from Southern California, USA

Despite the regulatory mandate to maintain “natural water quality”, there are ?271 storm drain discharges that potentially threaten the 14 designated marine water quality protected areas in Southern California called Areas of Special Biological Significance (ASBS). After sampling 35 site-events, the geomean concentrations of total suspended solids, nutrients, total and dissolved trace metals, and polycyclic aromatic hydrocarbons in the ocean following storm events were similar between reference drainages and ASBS discharge sites. Concentrations of chlorinated hydrocarbons were nondetectable and no post-storm sample exhibited significant toxicity to the endemic purple sea urchin (Strongylocentrotus purpuratus) near ASBS discharge sites. A reference-based threshold was developed and, despite the similarities in average concentrations, there were some individual ASBS discharge sites that were greater than reference background. Cumulatively across all ASBS, the constituents that were most frequently greater than the reference-based threshold were nutrients and general constituents, followed by dissolved and total trace metals.     

Contaminants still high in top-level carnivores in the Southern California Bight: levels of DDT and PCBs in resident and transient pinnipeds

Highly industrialized areas, such as the Southern California Bight, often have high levels of contaminants in marine sediments, which can cause chronic exposure to organisms long after their use has ceased. tDDT and tPCB were analyzed in the blubber of 145 stranded pinnipeds that died at local marine mammal centers between 1994 and 2006. Resident species (California sea lion and Pacific harbor seal) had significantly higher concentrations of tDDT and tPCB than the transient species (northern elephant seal). Adult female California sea lions had significantly lower concentrations of tDDT and tPCB than pups, yearlings, and adult males. Concentrations of both tDDT and tPCB in California sea lions significantly declined over time, but did not change in northern elephant seals. Current concentrations of tDDT and tPCB in California sea lions and harbor seals are among the highest values reported worldwide for marine mammals and exceed those reported to cause adverse health effects.     

Processes,spatio‐temporal factors and measurements of current erosion in the French Southern Alps: a review

Present erosion in mountainous areas of Western Europe causes land management problems, particularly for areas located downstream of erosion zones. Except for transalpine roads and ski resorts, economic activities no longer require as much space as they did in the past. Therefore, natural reforestation has provided signi?cant protection for alpine hillslopes during the 20th century. However, extreme ?oods continue to cause severe damage in intra‐alpine valleys, as well as in piedmont and surrounding plains, making the study of present water erosion phenomena very important. Many studies have investigated the processes and factors of water erosion on slopes at both the catchment and plot scales. They have focused on rock fragmentation and transportation in different ?elds, the spatial and temporal explanatory variables, the consequences downstream (?ooding, sedimentation, river bed evolution) and the impact of ?oods. In the French Alps, present erosion has been studied in a variety of outcrops, with several recent studies conducted in ?elds such as marls, clayey deposits, molasses and moraines. These kinds of outcrops are found throughout the alpine massif, including an area of special interest on the great Jurassic black marl outcrop where badlands are frequently observable. Geomorphologists and hydrologists have been particularly interested in the strong erosion processes in marls, seeking to determine the main patterns and the impact of spatial and temporal factors on soil loss quantities. The main climatic factors of rock disaggregation were found to be the freeze–thaw and wet–dry cycles, which destroy rock cohesion, and the splash effect of rain. The principal site variables are vegetation cover, exposure and dip–slope angle. Erosion rates are two or three orders of magnitude higher on bare soils than on pastures; northern aspect slopes suffer two to four times as much soil loss as southern aspect slopes. Finally, the angle formed by the slope and the dip also determines different behaviours: erosion rates are higher when slope and dip are perpendicular than when they are parallel. The transportation agents are mostly debris ?ows and runoff caused by intense precipitation. Annual erosion depth in the marls is generally assumed to be substantial, up to 10 mm. The high value can be explained by the severity of the climatic conditions and the brittleness of the lithology, which results in numerous fractures. Copyright © 2003 John Wiley & Sons, Ltd.     

Impacts of stormwater runoff in the Southern California Bight: Relationships among plume constituents

The effects from two winter rain storms on the coastal ocean of the Southern California Bight were examined as part of the Bight ‘03 program during February 2004 and February–March 2005. The impacts of stormwater from fecal indicator bacteria, water column toxicity, and nutrients were evaluated for five major river discharges: the Santa Clara River, Ballona Creek, the San Pedro Shelf (including the Los Angeles, San Gabriel, and Santa Ana Rivers), the San Diego River, and the Tijuana River. Exceedances of bacterial standards were observed in most of the systems. However, the areas of impact were generally spatially limited, and contaminant concentrations decreased below California Ocean Plan standards typically within 2–3 days. The largest bacterial concentrations occurred in the Tijuana River system where exceedances of fecal indicator bacteria were noted well away from the river mouth. Maximum nitrate concentrations (~40 μM) occurred in the San Pedro Shelf region near the mouth of the Los Angeles River. Based on the results of general linear models, individual sources of stormwater differ in both nutrient concentrations and the concentration and composition of fecal indicator bacteria. While nutrients appeared to decrease in plume waters due to simple mixing and dilution, the concentration of fecal indicator bacteria in plumes depends on more than loading and dilution rates. The relationships between contaminants (nutrients and fecal indicator bacteria) and plume indicators (salinity and total suspended solids) were not strong indicating the presence of other potentially important sources and/or sinks of both nutrients and fecal indicator bacteria. California Ocean Plan standards were often exceeded in waters containing greater than 10% stormwater (<28–30 salinity range). The median concentration dropped below the standard in the 32–33 salinity range (1–4% stormwater) for total coliforms and Enterococcus spp. and in the 28–30 salinity range (10–16% stormwater) for fecal coliforms. Nutrients showed a similar pattern with the highest median concentrations in water with greater than 10% stormwater. Relationships between colored dissolved organic matter (CDOM) and salinity and between total suspended solids and beam attenuation indicate that readily measurable, optically active variables can be used as proxies to provide at least a qualitative, if not quantitative, evaluation of the distribution of the dissolved, as well as the particulate, components of stormwater plumes. In this context, both CDOM absorption and the beam attenuation coefficient can be derived from satellite ocean color measurements of inherent optical properties suggesting that remote sensing of ocean color should be useful in mapping the spatial areas and durations of impacts from these contaminants.     

三峡澎溪河回水区流速对藻类原位生长速率的影响

为明晰不同流速水平对三峡支流回水区库湾藻类原位生长的影响,本文采用可调速的环形实验槽,选择三峡水库不同运行状态(低水位、高水位),对三峡澎溪河高阳平湖库湾藻类生物量(用叶绿素a浓度表示)变化特征进行原位受控实验.通过流速在0(对照)、0.1、0.2和0.3 m/s的实验发现,夏季低水位阶段澎溪河水域光热充足,但流速升高(0.2m/s)对藻类原位比生长速率具有一定影响.大体上,高阳平湖水域藻类原位比生长速率与流速水平呈对数关系.冬季高水位运行期间,流速的升高将可能在一定程度上促进水柱扰动,成为维持藻类在上层水体受光生长、避免下沉的主要因素.该时期,采用调节流速、流量的方法抑制藻类生长的难度相对较大.     

我国南方地区桉树叶浸泡对水库沉积物致黑元素分布及迁移转化的影响

我国南方地区桉树种植区周边水库冬季水体泛黑现象频发,桉树砍伐残体(尤其是叶)浸出液中富含的溶解性有机碳(DOC)、单宁酸与铁、锰、硫化物等一系列反应是其主要致黑原因,然而目前致黑物质对水库泛黑的贡献程度和途径仍不清楚.为了模拟桉树叶浸泡对水库黑水形成的影响机制,研究选取夏季水体未泛黑期(水体热分层稳定)进行室内浸泡实验,测定每6 h上覆水体溶解氧(DO)、氧化还原电位(Eh)、透光度等理化指标,分析DGT有效态铁、锰、硫和DOC、单宁酸浓度分布规律及迁移转化特征,计算沉积物-水界面处Fe²⁺、Mn²⁺、S^2-表观扩散通量.结果表明:桉树叶浸泡明显消耗水体中的DO,且显著影响水体Eh与透光度.此外,透光度与DO浓度呈显著正相关(相关系数为0.618~0.978).桉树叶浸泡释放大量DOC和单宁酸,其中单宁酸浓度远超有氧马尾松组,其上覆水中浓度分别达到23.9、26.0和34.0 mg/L,说明桉树浸泡为黑水形成提供了重要的DOC和单宁酸来源.桉树叶浸泡后上覆水和表层沉积物中DGT有效态Fe浓度均明显增加,深层沉积物间隙水中DGT有效态Fe浓度明显下降,且其表观扩散通量均为正值,说明深层沉积物中Fe向沉积物-水界面迁移,为黑水形成提供了重要的Fe来源.研究结果可为解决我国南方地区桉树人工林区水库水体突发性泛黑问题提供科学依据.     

Hemolytic activity and fatty acids composition in the ichthyotoxic dinoflagellate Cochlodinium polykrikoides isolated from Bahía de La Paz, Gulf of California

The hemolytic activity of the dinoflagellate Cochlodinium polykrikoides from Bahía de La Paz, Gulf of California was investigated as part of the ichthyotoxic mechanism of this microalga. Two different kinds of erythrocytes, fish and human, were tested for the hemolytic assay. Since fatty acids have been associated with hemolytic activity in C. polykrikoides, the composition of fatty acids of this dinoflagellate was also analyzed. The concentration of C. polykrikoides causing 50% hemolysis (HE₅₀) was 4.88 and 5.27 × 10⁶ cells L⁻¹, for fish and human erythrocytes, respectively. According to the standard curve of saponin, an equivalence between the hemolytic activity of saponin and the dinoflagellate concentration was found with 1 μg saponin mL⁻¹ equivalent to 1 × 10⁶ cells L⁻¹ of C. polykrikoides. The polyunsaturated fatty acids: hexadecaenoic (16:0), docosahexaenoic (22:6 n3) and octadecapentaenoic (18:5 n3) were found in an abundance of 62% of total fatty acids.     

Geological Observations of Damage Asymmetry in the Structure of the San Jacinto, San Andreas and Punchbowl Faults in Southern California: A Possible Indicator for Preferred Rupture Propagation Direction

We present new in situ observations of systematic asymmetry in the pattern of damage expressed by fault zone rocks along sections of the San Andreas, San Jacinto, and Punchbowl faults in southern California. The observed structural asymmetry has consistent manifestations at a fault core scale of millimeters to meters, a fault zone scale of meters to tens of meters and related geomorphologic features. The observed asymmetric signals are in agreement with other geological and geophysical observations of structural asymmetry in a damage zone scale of tens to hundreds of meters. In all of those scales, more damage is found on the side of the fault with faster seismic velocities at seismogenic depths. The observed correlation between the damage asymmetry and local seismic velocity structure is compatible with theoretical predictions associated with preferred propagation direction of earthquake ruptures along faults that separate different crustal blocks. The data are consistent with a preferred northwestward propagation direction for ruptures on all three faults. If our results are supported by additional observations, asymmetry of structural properties determined in field studies can be utilized to infer preferred propagation direction of large earthquake ruptures along a given fault section. The property of a preferred rupture direction can explain anomalous behavior of historic rupture events, and may have profound implications for many aspects of earthquake physics on large faults.     

三峡水库消落带适生树种落羽杉(Taxodium distichum)叶片-细根碳/氮/磷生态化学计量特征

为探究三峡库区消落带落羽杉（Taxodium distichum（L.） Rich.）叶片与细根C、N、P生态化学计量特征,于2018年7月对忠县三峡库区消落带植被修复示范基地3个水淹处理组（深度水淹组,DS;中度水淹组,MS;浅淹对照组,SS）的落羽杉进行叶片与细根采集,并调查其生长特征,测定分析落羽杉叶片与细根C、N、P生态化学计量特征及相关性.结果表明：（1）各水淹处理组落羽杉叶片C含量表现为SS组 > DS组 > MS组,且SS组显著高于MS组;细根C含量在不同水淹处理组之间均无显著性差异.（2）细根N、P含量表现为DS组 < MS组 < SS组的协同增长趋势;叶片N、P含量则表现为DS组 > MS组 > SS组的协同降低趋势,且叶片N、P含量分别约为细根N、P含量的3倍和2倍.（3）各水淹处理组的叶片C/N、C/P比值均显著或极显著低于细根;叶片N/P比值均高于细根,且其比值相对恒定,均表现为SS组 > DS组 > MS组的趋势.（4）相关性分析表明,叶片P含量与细根N含量呈显著负相关关系,叶片N/P比值与细根N/P比值呈显著正相关关系.研究表明,落羽杉叶片与细根在生长和代谢过程中具有整体性,养分和光合产物在地上与地下部分之间分配权衡,以维持营养的动态平衡,使落羽杉具有内稳性,从而更好地适应和响应三峡消落带水位变化.     

基于NEB试验的不同湖泊夏季营养物投入与藻类响应关系的比较:以淀山湖、小兴凯湖和洱海为例

淀山湖、小兴凯湖和洱海分别处在不同的营养阶段,夏季都存在蓝藻水华现象,有效控制蓝藻水华应控氮还是控磷一直存在争议.本研究采用营养物加富生物测试的试验方法,研究和比较三个湖泊限制性营养元素(N和P)夏季对浮游藻类生长的刺激作用,并采用多因素方差分析和两两比较方法(LSD)检验试验结果的显著性.结果表明:淀山湖(TN/TP=10左右)、洱海(TN/TP=29左右)、小兴凯湖(TN/TP=9左右)在夏季分别表现出显著的氮响应、氮磷双重响应、氮响应;较低氮磷比的营养程度较高的湖泊(淀山湖和小兴凯湖)夏季应控制氮含量,若添加氮更容易引发蓝藻(微囊藻)水华,而高氮磷比的初期富营养化湖泊(洱海)夏季应同时控制氮磷含量,同时添加氮磷的交互作用容易引发蓝藻(微囊藻)水华.     

Diatoms from the genus Achnanthidium in flowing waters of the Appalachian Mountains (North America): Ecology, distribution and taxonomic notes

Diatoms from the genus Achnanthidium are abundant in rivers, streams, and springs of the Appalachian Mountains. They inhabit clean and polluted waters, including those affected by acid mine drainage. The identification of Achnanthidium taxa is difficult due to their small cell size and insufficient information in the diatom floras. We studied the taxonomy and ecology of Achnanthidium in Appalachian rivers by analyzing a data set of benthic diatom samples and corresponding water chemistry data collected during several water-quality surveys from 181 sampling sites. Ten species were identified using scanning electron and light microscopy: A. alpestre (Lowe & Kociolek) Lowe & Kociolek, A. atomus (Hustedt) Monnier, Lange-Bertalot, & Ector, A. deflexum (Reimer) Kingston, A. duthii (Sreenivasa) Edlund, A. eutrophilum (Lange-Bertalot) Lange-Bertalot, A. cf. gracillimum (Meister) Lange-Bertalot, A. cf. latecephalum Kobayasi, A. minutissimum (Kützing) Czarnecki (sensu lato), A. reimeri (Camburn) comb. nov., and A. rivulare Potapova & Ponader. The distribution of common taxa in relation to water chemistry was studied by fitting non-parametric regression models (generalized additive models, GAM, and non-parametric multiplicative regression models, NPMR) to species relative abundances. Studied Achnanthidium species differed considerably in their responses to water chemistry. These results suggest that species-level identifications will lead to more accurate bioassessments.     

Okadaic acid, a causative toxin of diarrhetic shellfish poisoning, in green-lipped mussels Perna viridis from Hong Kong fish culture zones: Method development and monitoring

Green-lipped mussels (Perna viridis) were collected from seven fish culture zones (FCZs) in Hong Kong and analyzed for okadaic acid (OA). A conventional HPLC method was modified by incorporating a proteinase K digestion step. Results suggest that a higher recovery (2.5 times higher) of OA was obtained from spiked samples after the addition of 1.08 mg proteinase K in comparison with samples incubated without the proteolytic enzyme. For the hepatopancreas (HP) of individual field-collected mussels, the additional digestion step can enhance OA extraction by 3.1 times. Spatial and temporal variations in OA concentrations in the mussels from various FCZs were investigated. The highest concentration of OA in mussel HP samples was 1164.9 ng/g HP wet wt. With respect to OA concentrations in whole mussel tissues from seven sites and four seasonal samplings, the concentrations were between 70.0 and 131.0 ng/g wet wt., which did not exceed the generally recognized international regulatory criteria (>200 ng/g) for OA.