广东省入库河口N2O分布和通量的时空变化

本研究于2011年7月(丰水期)和12月(枯水期)分别对广东省13个水库的入库河口进行调查,使用吹扫捕集-气相色谱法测定了水中N2O的浓度并用Liss&Merlivat公式估算出入库河口向大气释放N2O的水-气交换通量。结果表明,河口丰水期N2O溶存浓度范围为15.37～175.22 nmol/L,平均值为(73.77±43.58)nmol/L;N2O水-气交换通量范围为0.26～5.40μmol/(m2.d),平均值是(2.53±1.94)μmol/(m2.d)。河口枯水期N2O溶存浓度范围为44.26～366.11 nmol/L,平均值是(126.61±102.74)nmol/L;N2O水-气交换通量范围是0.86～21.88μmol/(m2.d),平均值是(7.50±6.65)μmol/(m2.d)。河口丰水期N2O溶存浓度和水-气交换通量明显低于枯水期。与其他研究相比,本研究区N2O溶存浓度和水-气交换通量偏低。     

Size variability of juvenile Atlantic salmon: links to environmental conditions

Climate change models predict a 2 to 6° C increase in air temperature within the next 100 years in the Maritime Provinces of eastern Canada. Higher air temperatures are expected to contribute to increased water temperatures, alterations in stream flow conditions, and ultimately reductions in fish growth. Mean annual size-at-age of juvenile Atlantic salmon Salmo salar decreased in the Northwest Miramichi and Southwest Miramichi Rivers between 1971–1999. Lengths-at-age of juveniles were significantly correlated between the two rivers. For Atlantic salmon parr, stronger associations between inter-cohort fork length ( L _F) than intra-cohort L _F were observed, suggesting that environmental conditions in the current year of growth have the more significant effects on size of age 2 year parr than conditions encountered the previous year by age 1 year parr of the same cohort. Fork lengths of parr were significantly and negatively associated with spring air and water temperatures. In the Miramichi River, increases in air and water temperature as predicted from climate change models may adversely affect growth of juvenile Atlantic salmon parr, reducing the overall productivity of the Atlantic salmon populations in this region.     

Projected climate changes threaten ancient refugia of kelp forests in the North Atlantic

Intraspecific genetic variability is critical for species adaptation and evolution and yet it is generally overlooked in projections of the biological consequences of climate change. We ask whether ongoing climate changes can cause the loss of important gene pools from North Atlantic relict kelp forests that persisted over glacial–interglacial cycles. We use ecological niche modelling to predict genetic diversity hotspots for eight species of large brown algae with different thermal tolerances (Arctic to warm temperate), estimated as regions of persistence throughout the Last Glacial Maximum (20,000 YBP), the warmer Mid‐Holocene (6,000 YBP), and the present. Changes in the genetic diversity within ancient refugia were projected for the future (year 2100) under two contrasting climate change scenarios (RCP2.6 and RCP8.5). Models predicted distributions that matched empirical distributions in cross‐validation, and identified distinct refugia at the low latitude ranges, which largely coincide among species with similar ecological niches. Transferred models into the future projected polewards expansions and substantial range losses in lower latitudes, where richer gene pools are expected (in Nova Scotia and Iberia for cold affinity species and Gibraltar, Alboran, and Morocco for warm‐temperate species). These effects were projected for both scenarios but were intensified under the extreme RCP8.5 scenario, with the complete borealization (circum‐Arctic colonization) of kelp forests, the redistribution of the biogeographical transitional zones of the North Atlantic, and the erosion of global gene pools across all species. As the geographic distribution of genetic variability is unknown for most marine species, our results represent a baseline for identification of locations potentially rich in unique phylogeographic lineages that are also climatic relics in threat of disappearing.     

Variability in the mean latitude of the Atlantic Intertropical Convergence Zone as recorded by riverine input of sediments to the Cariaco Basin (Venezuela)

Changes in the strength and position of the Intertropical Convergence Zone (ITCZ) are an important component of climate variability in the tropical Atlantic. The Cariaco Basin, located on the northern margin of Venezuela, is sensitive to tropical Atlantic climate change and its sediments provide a record of past ITCZ behavior. Today, the Cariaco Basin experiences two distinct seasons that reflect the annual migration of the Atlantic ITCZ. Between January and March, when the ITCZ lies south of the equator, northeasterly trade winds sit directly over Cariaco Basin and strong coastal upwelling and dry conditions dominate. Beginning in June-July, as the ITCZ moves north, local rainfall reaches a maximum and the upwelling diminishes or disappears. Here we summarize new and previously published data on the river-derived terrigenous fraction of Cariaco Basin sediments, as well as comparisons to other paleoclimate records, which together suggest a coherent climatologic response in the tropical Atlantic triggered by a pattern of ITCZ migration that mimics the seasonal cycle. During periods of cooler North Atlantic SSTs, on time-scales ranging from the Little Ice Age to the Younger Dryas to the cold stadials of the last glacial, decreased detrital delivery to Cariaco Basin from local rivers suggests a southward shift in the mean latitudinal position of the ITCZ. During warm interstadials and periods of Holocene and deglacial warmth, northward shifts in ITCZ position and its belt of convective rainfall are inferred from increased detrital delivery to the basin. Whether the rapid shifts in ITCZ position and precipitation recorded by Cariaco Basin sediments and other regional records reflect a response to forcing originating in the high latitude Atlantic or to forcing potentially sourced in the tropics is a key question yet to be fully answered.     

Dietary variations within a family of ambush predators (Platycephalidae) occupying different habitats and environments in the same geographical region

This study has determined the extents and basis for variations in the composition of the prey ingested by the abundant species of a family highly adapted for ambush predation, i.e. Platycephalidae, in a region (south‐western Australia) where that family is found in different habitats and environments. Dietary data were thus collected for Leviprora inops and Platycephalus laevigatus from seagrass in marine embayments and for Platycephalus westraliae from over sand in an estuary. These were then collated with those recorded previously for Platycephalus speculator from over sand and in seagrass in an estuary and for Platycephalus longispinis from over sand in coastal marine waters. While crustaceans and teleosts together dominated the diet of all five species, their percentage volumetric dietary contributions varied greatly, with those of crustaceans ranging from 7% for L. inops to 65% for P. speculator and those of teleosts ranging from 29% for P. longispinis to 91% for L. inops. For analyses, the data were separated into two sets. The first comprised the 17 dietary categories of invertebrates and all identified and unidentified teleosts collectively, while the second consisted of the 23 identified teleost families, both of which were subjected to permutational analysis of variance (PERMANOVA), analysis of similarities (ANOSIM) and a new (two‐way) version of the RELATE procedure. The diets of three species changed seasonally, when using invertebrate dietary categories and teleosts collectively, but with only one species, when employing identified teleost families, probably reflecting a greater tendency for invertebrate than teleost prey abundance to change during the year. On the basis of dietary data for invertebrate taxa + teleosts collectively, the diets of three of the five species changed serially with body size, with a fourth species feeding, throughout life, predominantly on the carid Palaemonetes australis. Based on identified teleost families, the diets of the three species that fed predominantly on teleosts underwent serial size‐related changes. Although L. inops and the co‐occurring P. laevigatus both consume large volumes of teleosts, the former ingests larger, less demersal and more mobile prey, e.g. the labrids Haletta semifasciata and Neoodax balteatus, than the latter, e.g. the scorpaenid Gymnapistes marmoratus, reflecting the possession by L. inops of a far longer head and larger buccal cavity. Circumstantial evidence suggests that the large differences in the volumes of crustaceans and teleosts consumed by each platycephalid species are related to differences in the relative availability of these prey in the different habitats or environments of each species.     

Climate-driven range expansion of a critically endangered top predator in northeast Atlantic waters

Global climate change is driving rapid distribution shifts in marine ecosystems; these are well established for lower trophic levels, but are harder to quantify for migratory top predators. By analysing a 25-year sightings-based dataset, we found evidence for rapid northwards range expansion of the critically endangered Balearic shearwater Puffinus mauretanicus in northeast Atlantic waters. A 0.6 degrees C sea surface temperature increase in the mid-1990s is interpreted as an underlying controlling factor, while simultaneous northward shifts of plankton and prey fish species suggests a strong bottom-up control. Our results have important conservation implications and provide new evidence for climate-driven regime shift in Atlantic ecosystems.     

Genetic variation at enzyme loci in the southernmost European populations of Atlantic salmon

Genetic variation was studied at 8 allozyme loci in six severely endangered wild Spanish populations of Salmo salar located at the southernmost geographical limit of European Atlantic salmon. Low levels of variation were detected and no significant deviations from Hardy–Weinberg equilibrium were found.     

Changes in age composition and growth characteristics of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) over 400 years

Populations of sturgeon (Acipenseridae) have experienced global declines, and in some cases extirpation, during the past century. In the current era of climate change and over-harvesting of fishery resources, climate models, based on uncertain boundary conditions, are being used to predict future effects on the Earth''s biota. A collection of approximately 400-year-old Atlantic sturgeon spines from a midden in colonial Jamestown, VA, USA, allowed us to compare the age structure and growth rate for a pre-industrial population during a ‘mini-ice age’ with samples collected from the modern population in the same reach of the James River. Compared with modern fish, the colonial population was characterized by larger and older individuals and exhibited significantly slower growth rates, which were comparable with modern populations at higher latitudes of North America. These results may relate to higher population densities and/or colder water temperatures during colonial times.     

Evaluating regional resiliency of coastal wetlands to sea level rise through hypsometry‐based modeling

Sea level rise (SLR) threatens coastal wetlands worldwide, yet the fate of individual wetlands will vary based on local topography, wetland morphology, sediment dynamics, hydrologic processes, and plant‐mediated feedbacks. Local variability in these factors makes it difficult to predict SLR effects across wetlands or to develop a holistic regional perspective on SLR response for a diversity of wetland types. To improve regional predictions of SLR impacts to coastal wetlands, we developed a model that addresses the scale‐dependent factors controlling SLR response and accommodates different levels of data availability. The model quantifies SLR‐driven habitat conversion within wetlands across a region by predicting changes in individual wetland hypsometry. This standardized approach can be applied to all wetlands in a region regardless of data availability, making it ideal for modeling SLR response across a range of scales. Our model was applied to 105 wetlands in southern California that spanned a broad range of typology and data availability. Our findings suggest that if wetlands are confined to their current extents, the region will lose 12% of marsh habitats (vegetated marsh and unvegetated flats) with 0.6 m of SLR (projected for 2050) and 48% with 1.7 m of SLR (projected for 2100). Habitat conversion was more drastic in wetlands with larger proportions of marsh habitats relative to subtidal habitats and occurred more rapidly in small lagoons relative to larger sites. Our assessment can inform management of coastal wetland vulnerability, improve understanding of the SLR drivers relevant to individual wetlands, and highlight significant data gaps that impede SLR response modeling across spatial scales. This approach augments regional SLR assessments by considering spatial variability in SLR response drivers, addressing data gaps, and accommodating wetland diversity, which will provide greater insights into regional SLR response that are relevant to coastal management and restoration efforts.     

Plankton response to weakening of the Iberian coastal upwelling

Coastal upwelling regions, which are affected by equatorward‐wind variability, are among the most productive areas of the oceans. It has been suggested that global warming will lead to a general strengthening of coastal upwelling, with important ecological implications and an impact on fisheries. However, in the case of the Iberian upwelling, the long‐term analysis of climatological variables described here reveals a weakening in coastal upwelling. This is linked to a decrease of zonal sea level pressure gradient, and correlated with an observed increase of sea surface temperature and North Atlantic Oscillation. Weakening of coastal upwelling has led to quantifiable modifications of the ecosystem. In outer shelf waters a drop in new production over the last 40 years is likely related to the reduction of sardine landings at local harbors. On the other hand, in inner shelf and Ria waters, the observed weakening of upwelling has slowed down the residual circulation that introduces nutrients to the euphotic layer, and has increased the stability of the water column. The drop in nutrient levels has been compensated by an increase of organic matter remineralization. The phytoplankton community has responded to those environmental trends with an increase in the percentage of dinoflagellates and Pseudonitzschia spp. and a reduction in total diatoms. The former favors the proliferation of harmful algal blooms and reduces the permitted harvesting period for the mussel aquaculture industry. The demise of the sardine fishery and the potential threat to the mussel culture could have serious socio‐economic consequences for the region.     

A novel approach to quantify and locate potential microrefugia using topoclimate,climate stability,and isolation from the matrix

Ecologists are increasingly recognizing the conservation significance of microrefugia, but it is inherently difficult to locate these small patches with unusual climates, and hence they are also referred to as cryptic refugia. Here we introduce a new methodology to quantify and locate potential microrefugia using fine‐scale topoclimatic grids that capture extreme conditions, stable climates, and distinct differences from the surrounding matrix. We collected hourly temperature data from 150 sites in a large (200 km by 300 km) and diverse region of New South Wales, Australia, for a total of 671 days over 2 years. Sites spanned a range of habitats including coastal dune shrublands, eucalypt forests, exposed woodland ridges, sheltered rainforest gullies, upland swamps, and lowland pastures. Climate grids were interpolated using a regional regression approach based on elevation, distance to coast, canopy cover, latitude, cold‐air drainage, and topographical exposure to winds and radiation. We identified extreme temperatures on two separate climatic gradients: the 5th percentile of minimum temperatures and the 95th percentile of maximum temperatures. For each gradient, climatic stability was assessed on three different time scales (intra‐seasonal, intra‐annual and inter‐annual). Differences from the matrix were assessed using a moving window with a 5 km radius. We averaged the Z‐scores for these extreme, stable and isolated climates to identify potential locations of microrefugia. We found that our method successfully predicted the location of communities that were considered to occupy refugia, such as rainforests that have progressively contracted in distribution over the last 2.5 million years, and alpine grasslands that have contracted over the last 15 thousand years. However, the method was inherently sensitive to the gradient selected and other aspects of the modelling process. These uncertainties could be dealt with in a conservation planning context by repeating the methodology with various parameterizations and identifying areas that were consistently identified as microrefugia.     

Tundra ecosystems observed to be CO2 sources due to differential amplification of the carbon cycle

Are tundra ecosystems currently a carbon source or sink? What is the future trajectory of tundra carbon fluxes in response to climate change? These questions are of global importance because of the vast quantities of organic carbon stored in permafrost soils. In this meta‐analysis, we compile 40 years of CO₂ flux observations from 54 studies spanning 32 sites across northern high latitudes. Using time‐series analysis, we investigated if seasonal or annual CO₂ fluxes have changed over time, and whether spatial differences in mean annual temperature could help explain temporal changes in CO₂ flux. Growing season net CO₂ uptake has definitely increased since the 1990s; the data also suggest (albeit less definitively) an increase in winter CO₂ emissions, especially in the last decade. In spite of the uncertainty in the winter trend, we estimate that tundra sites were annual CO₂ sources from the mid‐1980s until the 2000s, and data from the last 7 years show that tundra continue to emit CO₂ annually. CO₂ emissions exceed CO₂ uptake across the range of temperatures that occur in the tundra biome. Taken together, these data suggest that despite increases in growing season uptake, tundra ecosystems are currently CO₂ sources on an annual basis.     

Adapting a patch model to simulate the sensitivity of Central-Canadian boreal ecosystems to climate variability

Aim To investigate effects of within-season and interannual climate variability on the behaviour of boreal forest ecosystems as simulated by the FORSKA2 patch model. Location Eleven climate station locations distributed along a transect across the boreal zone of central Canada. Methods FORSKA2′s water balance submodel was modified to enable it to behave more realistically under a varying climate. Long-term actual monthly time-series of temperature and precipitation data were detrended and used to drive the modified model. Long-term monthly averages of the same detrended data were used to drive the unmodified model. Results Modifications created significant improvements when simulating species composition at sites in boreal Canada. Simulated forest biomass values were slightly higher than those obtained from the unmodified model using averaged climate records, but resembled the observed distribution of vegetation more closely. Main conclusions Modified FORSKA2 suggests that boreal forest composition and distribution may be more sensitive to changes in monthly rainfall data than to changes in temperature. Climate variability affects seasonal water balances and should be considered when using patch models to forecast vegetation dynamics during and following a period of climate transition. The modified model provided improved representation of the latitudinal trend in spatially averaged biomass density in this region.     

Coastal heathland vegetation is surprisingly resistant to experimental drought across successional stages and latitude

In the last decade, several major dwarf-shrub dieback events have occurred in northern European coastal heathlands. These dieback events occur after extended periods with sub-zero temperatures under snow-free conditions and clear skies, suggesting that coastal heathlands have low resistance to winter drought. As climate projections forecast increased drought frequency, intensity, and duration, coastal heathlands are likely to experience more such diebacks in the future. There are, however, few empirical studies of drought impacts and responses on plant communities in humid oceanic ecosystems. We established a drought experiment with two distinct levels of intensified drought to identify responses and thresholds of drought resistance in coastal heathland vegetation. We repeated the experiment in two regions, separated by five degrees latitude, to represent different bioclimatic conditions within the coastal heathlands' wide latitudinal range in Europe. As coastal heathlands are semi-natural habitats managed by prescribed fire, and we repeated the experiment across three post-fire successional phases within each region. Plant community structure, annual primary production, and primary and secondary growth of the dominant dwarf-shrub Calluna vulgaris varied between climate regions. To our surprise, these wide-ranging vegetation- and plant-level response variables were largely unaffected by the drought treatments. Consequently, our results suggest that northern, coastal heathland vegetation is relatively resistant to substantial intensification in drought. This experiment represents the world's wettest (2200 mm year⁻¹) and northernmost (65°8'N) drought experiment to date, thus filling important knowledge gaps on ecological drought responses in high-precipitation and high-latitude ecosystems across multiple phases of plant community succession.     

海洋二甲基硫观测技术及其海-气通量分析研究进展

二甲基硫(DMS)海-气交换是全球硫循环的主要参与者,对全球气候变化产生重要影响。有关海洋DMS排放及其海-气交换过程研究已引起人们的广泛关注,并成为现今国际上的研究热点之一。从海洋DMS观测技术及海-气通量估算两方面进行了系统总结,并指出了它们的最新进展和发展趋势,具体包括:虽然遥感技术在获取DMS时空分布及大面数据方面具有独特优势,但气相色谱法是目前应用最为广泛的观测技术,而质谱也越来越受到研究者们的青睐;直接观测技术在提升分析性能的同时朝着自动化、智能化现场实时观测的方向发展;观测对象从单一DMS扩展至其前体、二甲基亚砜等其他物质,同时所获数据呈多元化趋势,准确度也逐渐提升;以滞膜模型为代表的模型估算和以涡旋相关法为代表的直接测量法是目前DMS海-气通量分析的主要方法,而多元化数据则促进了两种或两种以上通量分析方法的联合及对比;深入探究海洋环境因素对海-气交换过程的影响,进一步完善速率常数计算和通量估算方法,是获得适用性更广、准确度更高的DMS传输率常数及提高通量估算准确度的重要途径;将直接观测技术和遥感卫星观测技术相结合,开展时间、空间维度上的全球海域DMS大数据调查研究,并深入评估DMS对海洋环境及气候变化的影响将是未来研究的重要内容;基于大数据基础构建海洋DMS排放趋势模型,实现未来DMS排放的准确预测是DMS观测及其海-气通量分析研究的重要目标。     

A new genus of <Emphasis Type="Italic">Monimiaceae</Emphasis> from the Atlantic Coastal Forest in South-Eastern Brazil

Summary  A new monotypic genus and a new species of Monimiaceae, Grazielanthus arkeocarpus from the Brazilian Atlantic coastal forest are described, illustrated and compared with morphologically related taxa. The new taxon occurs in the State of Rio de Janeiro in the central coastal plain and was collected in the Po?o das Antas Biological Reserve, municipality of Silva Jardim (22°30′– 22°33′S; 42°14′– 42°19′W). The new taxon is represented by dioecious climbing shrubs of the sub-canopy that have urceolate, four-lobed flowers and a fleshy hypanthium that is closed until the fruit ripens. When ripe, the hypanthium ruptures irregularly and the fruitlets are exposed. The relationships between the new genus and other neotropical (Hennecartia J. Poiss. and Macrotorus Perkins) and paleotropical (Palmeria F. Muell.) genera are discussed.     

Thermal variation near the thermal optimum does not affect the growth,metabolism or swimming performance in wild Atlantic salmon Salmo salar

Typically, laboratory studies on the physiological effects of temperature are conducted using stable acclimation temperatures. Nonetheless, information extrapolated from these studies may not accurately represent wild populations living in thermally variable environments. The aim of this study was to compare the growth rate, metabolism and swimming performance of wild Atlantic salmon exposed to cycling temperatures, 16–21°C, and stable acclimation temperatures, 16, 18.5, 21°C. Growth rate, metabolic rate, swimming performance and anaerobic metabolites did not change among acclimation groups, suggesting that within Atlantic salmon's thermal optimum range, temperature variation has no effect on these physiological properties.     

From silk to satellite: half a century of ocean colour anomalies in the Northeast Atlantic

Changes in phytoplankton dynamics influence marine biogeochemical cycles, climate processes, and food webs, with substantial social and economic consequences. Large‐scale estimation of phytoplankton biomass was possible via ocean colour measurements from two remote sensing satellites – the Coastal Zone Colour Scanner (CZCS, 1979–1986) and the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS, 1998–2010). Due to the large gap between the two satellite eras and differences in sensor characteristics, comparison of the absolute values retrieved from the two instruments remains challenging. Using a unique in situ ocean colour dataset that spans more than half a century, the two satellite‐derived chlorophyll‐a (Chl‐a) eras are linked to assess concurrent changes in phytoplankton variability and bloom timing over the Northeast Atlantic Ocean and North Sea. Results from this unique re‐analysis reflect a clear increasing pattern of Chl‐a, a merging of the two seasonal phytoplankton blooms producing a longer growing season and higher seasonal biomass, since the mid‐1980s. The broader climate plays a key role in Chl‐a variability as the ocean colour anomalies parallel the oscillations of the Northern Hemisphere Temperature (NHT) since 1948.