Predicting the effects of shade on water temperature in small streams

A computer model for stream water temperature was developed, and tested in a small pasture stream near Hamilton, New Zealand. The model quantifies shading by riparian vegetation, hillsides, and stream banks using three coefficients: canopy angle, topography angle, and canopy shade factor. Shade was measured directly and found to vary significantly along the channel. Using the maximum measured shade, a close match was achieved between observed and predicted daily maximum and minimum water and bed sediment temperature. Model predictions of incoming and outgoing long‐wave radiation flux closely matched measurements, but there were unexplained discrepancies in short‐wave radiation flux. Model predictions indicate that moderate shade levels (c. 70%) may be sufficient in temperate climates to restore headwater pasture stream temperatures to 20°C, an estimate of the thermal tolerance for sensitive invertebrates.     

Consistency of Geoid Models,Radar Altimetry,and Hydrodynamic Modelling in the North Sea

Radar altimetry, when corrected for tides, atmospheric forcing of the sea surface, and the effects of density variations and mean and time-variable currents, provides an along-track realization of the marine geoid. In this study we investigate whether and how such an ‘altimetric-hydrodynamic’ geoid over the North Sea can serve for validating satellite-gravimetric geoids. Our results indicate that, using ERS-2 and ENVISAT along-track altimetry and water levels from the high-resolution operational circulation model BSHcmod, we do find distinct differences in RMS fits for various state-of-the art satellite-only models (beyond degree 145 for GRACE-only, and beyond degree 185 for GOCE models) and for combined geoid models, very similar as seen in GPS-levelling validations over land areas. We find that, at spectral resolution of up to about 200, an RMS fit as low as about 7 cm can be obtained for the most recent GOCE-derived models such as GOCO05S. This is slightly above what we expect from budgeting individual errors. Key to the validation is a proper treatment of the spectral mismatch between satellite-gravimetric and altimetric-hydrodynamic geoids. Comparison of data fits and error budget suggests that geoid truncation errors residual to EGM2008 (i.e. EGM2008 commission and omission error) may amount up to few cm.     

Modelling multi-species interactions in the Barents Sea ecosystem with special emphasis on minke whales and their interactions with cod, herring and capelin

The Barents Sea ecosystem, one of the most productive and commercially important ecosystems in the world, has experienced major fluctuations in species abundance the past five decades. Likely causes are natural variability, climate change, overfishing and predator–prey interactions. In this study, we use an age-length structured multi-species model (Gadget, Globally applicable Area-Disaggregated General Ecosystem Toolbox) to analyse the historic population dynamics of major fish and marine mammal species in the Barents Sea. The model was used to examine possible effects of a number of plausible biological and fisheries scenarios. The results suggest that changes in cod mortality from fishing or cod cannibalism levels have the largest effect on the ecosystem, while changes to the capelin fishery have had only minor effects. Alternate whale migration scenarios had only a moderate impact on the modelled ecosystem. Indirect effects are seen to be important, with cod fishing pressure, cod cannibalism and whale predation on cod having an indirect impact on capelin, emphasising the importance of multi-species modelling in understanding and managing ecosystems. Models such as the one presented here provide one step towards an ecosystem-based approach to fisheries management.     

Modelling the effects and economics of managed realignment on the cycling and storage of nutrients, carbon and sediments in the Blackwater estuary UK

A hydrodynamic model is developed for the Blackwater estuary (UK) and used to estimate nitrate removal by denitrification. Using the model, sediment analysis and estimates of sedimentation rates, we estimate changes in estuarine denitrification and intertidal carbon and nutrient storage and associated value of habitat created under a scenario of extensive managed realignment. We then use this information, together with engineering and land costs, to conduct a cost benefit analysis of the managed realignment. This demonstrates that over a 50–100 year timescale the value of the habitat created and carbon buried is sufficient to make the large scale managed realignment cost effective. The analysis reveals that carbon and nutrient storage plus habitat creation represent major and quantifiable benefits of realignment. The methodology described here can be readily transferred to other coastal systems.     

电厂温排水对湛江湾海水温升的数值模拟及生态影响评价

为了清晰了解温排水入海后的时空输移路径和温升范围,及其对海洋环境的影响,以湛江湾内的某电厂为例,应用ECOMSED海洋模式计算其温排水的时空输移路径及温升范围,并结合野外生态调查结果评价其对湛江湾内海洋生态环境的影响.结果表明：某电厂温排水导致湛江湾水体温升大于4℃、2℃、1℃的面积分别为0.110、0.480、1.629 km2,相对于约190 km2的湛江湾海域,影响面积很小;夏季浮游植物丰度随温度升高的变化率分别为-8.534%、-3.573%、-1.613%,浮游动物丰度随温度升高的变化率分别为-4.964%、-1.896%、-0.802%,温排水对浮游动、植物的影响夏季较冬季显著.某电厂温排水对湛江湾内海洋生态环境的影响即使在高温季节也不明显.     

厦门大嶝岛潮间带底栖微藻叶绿素荧光对温度和光照变化的响应

采用PAM叶绿素荧光技术,于2013年5月在厦门大嶝岛潮间带,对不同底质类型（泥质、泥砂质和砂质）底栖微藻的光合作用特征进行了初步研究.结果显示：底栖微藻的光合系统II最大光量子效率（Fv/Fm）呈泥质（0.33）〉泥砂质（0.28）〉砂质（0.01）;底栖微藻叶绿素a含量亦呈上述变化趋势.不同温度（15-35℃）和不同光照透射率（0-100%）的短期（0.5-2.0 h）培养实验表明,底栖微藻光合作用的最适温度（27℃左右）接近于环境温度,体现了其对生长环境的适应;过高的温度（35℃及以上）会抑制光合作用活性,进而限制其生长;此外,光照实验表明底栖微藻可通过自身的运动和变化来适应光照强度的变化,不同底质类型可能存在不同的光适应策略.     

Food webs in forest and pasture streams in the Waikato region,New Zealand: A study based on analyses of stable isotopes of carbon and nitrogen,and fish gut contents

Abstract

Stable isotopes of carbon (C) and nitrogen (N) were studied in 11 stream communities in the Waikato region of New Zealand. From comparisons of mean δ¹³C and δ¹⁵N values, food webs in the shaded, forest streams were clearly based on allochthonous material (conditioned leaf litter and terrestrial invertebrates). Autotrophs in forest streams were not a significant C source for the food webs. However, the C source of food webs in the unshaded pasture streams appeared to be a mixture of allochthonous and autochthonous material. Conditioned leaf litter appeared to contribute to the pasture stream food webs, and the δ¹³C and δ¹⁵N of some samples of epilithic diatoms indicated their consumption by invertebrates in pasture streams. Fish ate a wide range of aquatic invertebrates; longfinned eels (Anguilla dieffenbachii) and banded kokopu (Galaxias fasciatus) also had a large proportion of terrestrial invertebrates in their diet. Filamentous green algae were found only at pasture sites, where they were sometimes abundant. The wide range of δ¹³C values of filamentous green algae (‐18.8 to ‐29.7‰) complicated understanding of their role in the stream food webs. The δ¹³C values of Cladophora were related to water velocity, with more ¹³C‐enriched values in pools than in runs (‐23.2‰ in pools, mean velocity 0.12 m s^?1; ‐28.1‰ in runs, mean velocity 0.24 m s^?1). Crayfish and the gastropod mollusc Potamopyrgus appeared to be the only invertebrates to eat filamentous green algae.     

Effects of acidified seawater on calcification,photosynthetic efficiencies and the recovery processes from strong light exposure in the coral Stylophora pistillata

The aim of this study was to investigate whether coral photosynthetic efficiencies and recovery processes are affected by CO₂‐driven ocean acidification in symbiont photosynthesis and coral calcification. We investigated the effects of five CO₂ partial pressure (pCO₂) levels in adjusted seawater ranging from 300 μatm (pre‐industrial) to 800 μatm (near‐future) and strong and weak light intensity on maximum photosynthetic efficiency and calcification of a branching coral, Stylophora pistillata, as this species has often been used in rearing experiments to investigate the effects of acidified seawater on calcification and photosynthetic algae of corals. We found that, the photosynthetic efficiencies and recovery patterns under different light conditions did not differ among pCO₂ treatments. Furthermore, calcification of S. pistillata was not affected by acidified seawater under weak or strong light conditions. Our results indicate that the photosynthetic efficiency and calcification of S. pistillata are insensitive to changes in ocean acidity.     

Effects of salinity,temperature, and light intensity on the growth rates of two halophilic phytoflagellates in mixed culture

Growth rates of two halophilic phytoflagellates, Dunaliella euchlora Lerche and D. salina Teodoresco, were studied in mixed batch cultures grown in filtered, axenic brines from Lake Grassmere, New Zealand. Forty‐five combinations of temperature, salinity, and light intensity were used. A maximum growth rate of 1.50 doublings day^‐1 was attained by D. salina at 26°C, 190 × 10^‐3S at a light intensity of 126 μE m^‐2 s^‐1. D. euchlora showed maximum growth rate of 1.16 doublings day^‐1 at 20°C, 120 × 10^‐3S at a light intensity of 180 μE m^‐2s^‐1. Predicted maximum values of 1.41 and 1.14 doublings day^‐1 respectively were obtained from regression models based on 45 replicate treatment combinations. In decreasing order of importance, temperature, salinity, and light intensity influence growth rates of brine algae. The optimum temperature for growth of both species increased as the salt concentration increased but decreased with increasing light intensity.     

驯化水温及温升速率对三门湾三种虾蟹类热耐受性的影响

作者采用动态实验法与静态实验法相结合的方法,研究了三门湾脊尾白虾(Exopalaemon carinicauda)、口虾蛄(Oratosquilla oratoria)和日本(Charybdis japonica)在不同季节的基础水温即驯化水温(8~29℃)和温升速率(0.5~15.0℃/h)下的热耐受能力。结果表明,驯化水温和温升速率对各实验动物的热耐受性均有显著影响。实验动物的热耐受性与驯化水温总体上呈显著正相关,而温升速率对热耐受性的影响具有物种特异性,并受驯化水温制约;在不同驯化水温下,各实验动物的热耐受性随温升速率增大呈不同变化趋势。各实验动物的24 h高起始致死温度受驯化水温的影响显著,随着驯化水温从8℃升高到29℃,脊尾白虾、日本和口虾蛄的24hUILT50分别从24.2、34.6、24.9℃显著增大到35.3、37.4和34.4℃。结合3种实验动物的最大临界温度分析,它们的热耐受能力依次为:日本脊尾白虾口虾蛄。研究结果可为探究三门湾水域潜在的热污染状况及其生态环境效应提供科学依据。     

Water quality and thermal regime of the Motueka River: Influences of land cover,geology and position in the catchment

We examined the effects of land use, geology, and longitudinal position within the river network on water quality and thermal regime at 23 sites within the Motueka River catchment. The concentrations of suspended solids, nitrate nitrogen, total nitrogen, Escherichia coli, and Campylobacter were higher at sites draining pastoral and horticultural land than in similar‐sized native or plantation forest streams. Average daily mean temperature and minimum temperature in summer and maximum winter temperature were higher in unshaded pastoral and horticultural streams than at native forest sites. Differences in water quality and thermal regime were also observed among sites with contrasting geology. Conductivity, pH, and minimum winter temperatures were highest at sites draining marble terrain. In contrast, longitudinal patterns in water quality and temperature regime along the 120‐km length of the river were relatively weak, although longitudinal patterns in amplitude of daily temperature fluctuation matched theoretical predictions. In this study, differences in land use appeared to have the strongest influence on most water quality and thermal variables examined. However, geology was an important factor explaining variation in certain variables (e.g., pH and conductivity). Longitudinal patterns in water quality and temperature were relatively weak and in many instances were linked with longitudinal patterns in land use and geology rather than catchment location alone.     

海洋三维温盐流数值模拟研究的有关进展和问题

就海洋三维温盐流数值模拟使用的海洋模式和数据同化方法、在中尺度数值预报和再分析中的应用,以及所需支撑条件三方面,简述了国内外研究有关进展和问题。表述了开展大范围分辨中尺度乃至次中尺度涡的高分辨率海洋三维温盐流数值模拟正在研究的有关问题,扼要说明提供相匹配的高性能计算机模拟平台的必要性。初步探讨制约该研究快速发展的有关问题。