Escalating Worldwide use of Urea – A Global Change Contributing to Coastal Eutrophication

While the global increase in the use of nitrogen-based fertilizers has been well recognized, another change in fertilizer usage has simultaneously occurred: a shift toward urea-based products. Worldwide use of urea has increased more than 100-fold in the past 4 decades and now constitutes >50% of global nitrogenous fertilizer usage. Global urea usage extends beyond agricultural applications; urea is also used extensively in animal feeds and in manufacturing processes. This change has occurred to satisfy the world’s need for food and more efficient agriculture. Long thought to be retained in soils, new data are suggestive of significant overland transport of urea to sensitive coastal waters. Urea concentrations in coastal and estuarine waters can be substantially elevated and can represent a large fraction of the total dissolved organic nitrogen pool. Urea is used as a nitrogen substrate by many coastal phytoplankton and is increasingly found to be important in the nitrogenous nutrition of some harmful algal bloom (HAB) species. The global increase from 1970 to 2000 in documented incidences of paralytic shellfish poisoning, caused by several HAB species, is similar to the global increase in urea use over the same 3 decades. The trend toward global urea use is expected to continue, with the potential for increasing pollution of sensitive coastal waters around the world.     

China's crop productivity and soil carbon storage as influenced by multifactor global change

Much concern has been raised about how multifactor global change has affected food security and carbon sequestration capacity in China. By using a process‐based ecosystem model, the Dynamic Land Ecosystem Model (DLEM), in conjunction with the newly developed driving information on multiple environmental factors (climate, atmospheric CO₂, tropospheric ozone, nitrogen deposition, and land cover/land use change), we quantified spatial and temporal patterns of net primary production (NPP) and soil organic carbon storage (SOC) across China's croplands during 1980–2005 and investigated the underlying mechanisms. Simulated results showed that both crop NPP and SOC increased from 1980 to 2005, and the highest annual NPP occurred in the Southeast (SE) region (0.32 Pg C yr^?1, 35.4% of the total NPP) whereas the largest annual SOC (2.29 Pg C yr^?1, 35.4% of the total SOC) was found in the Northeast (NE) region. Land management practices, particularly nitrogen fertilizer application, appear to be the most important factor in stimulating increase in NPP and SOC. However, tropospheric ozone pollution and climate change led to NPP reduction and SOC loss. Our results suggest that China's crop productivity and soil carbon storage could be enhanced through minimizing tropospheric ozone pollution and improving nitrogen fertilizer use efficiency.     

Consequences of human modification of the global nitrogen cycle

The demand for more food is increasing fertilizer and land use, and the demand for more energy is increasing fossil fuel combustion, leading to enhanced losses of reactive nitrogen (N_r) to the environment. Many thresholds for human and ecosystem health have been exceeded owing to N_r pollution, including those for drinking water (nitrates), air quality (smog, particulate matter, ground-level ozone), freshwater eutrophication, biodiversity loss, stratospheric ozone depletion, climate change and coastal ecosystems (dead zones). Each of these environmental effects can be magnified by the ‘nitrogen cascade’: a single atom of N_r can trigger a cascade of negative environmental impacts in sequence. Here, we provide an overview of the impact of N_r on the environment and human health, including an assessment of the magnitude of different environmental problems, and the relative importance of N_r as a contributor to each problem. In some cases, N_r loss to the environment is the key driver of effects (e.g. terrestrial and coastal eutrophication, nitrous oxide emissions), whereas in some other situations nitrogen represents a key contributor exacerbating a wider problem (e.g. freshwater pollution, biodiversity loss). In this way, the central role of nitrogen can remain hidden, even though it actually underpins many trans-boundary pollution problems.     

Spatial and Temporal Variations of Crop Fertilization and Soil Fertility in the Loess Plateau in China from the 1970s to the 2000s

Increased fertilizer input in agricultural systems during the last few decades has resulted in large yield increases, but also in environmental problems. We used data from published papers and a soil testing and fertilization project in Shaanxi province during the years 2005 to 2009 to analyze chemical fertilizer inputs and yields of wheat (Triticum aestivum L.) and maize (Zea mays L.) on the farmers'' level, and soil fertility change from the 1970s to the 2000s in the Loess Plateau in China. The results showed that in different regions of the province, chemical fertilizer NPK inputs and yields of wheat and maize increased. With regard to soil nutrient balance, N and P gradually changed from deficit to surplus levels, while K deficiency became more severe. In addition, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium increased during the same period. The PFP of N, NP and NPK on wheat and maize all decreased from the 1970s to the 2000s as a whole. With the increase in N fertilizer inputs, both soil total nitrogen and alkali-hydrolysis nitrogen increased; P fertilizer increased soil available phosphorus and K fertilizer increased soil available potassium. At the same time, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium all had positive impacts on crop yields. In order to promote food safety and environmental protection, fertilizer requirements should be assessed at the farmers'' level. In many cases, farmers should be encouraged to reduce nitrogen and phosphate fertilizer inputs significantly, but increase potassium fertilizer and organic manure on cereal crops as a whole.     

Brown Tide blooms in Long Island's coastal waters linked to interannual variability in groundwater flow

There has been a widespread increase in the reporting of harmful and ‘nuisance’ algal blooms in the coastal ocean over the past few decades. On the global scale this is suspected to be a consequence of coastal eutrophication, however, on a case-by-case basis there is usually insufficient evidence to discriminate between the effects of human and natural causal factors. Intense blooms of the ‘Brown Tide’ unicellular algae (Aureococcus anophagefferens) have occurred sporadically since 1985 in coastal waters of Eastern Long Island and have devastated the local commercial scallop fishery. Analysis of an 11-year time-series dataset from this region indicates that bloom intensity is correlated with higher salinities and inversely correlated with the discharge of groundwater. Laboratory and field studies suggest that whereas salinity is unlikely to represent a direct physiological control on Brown Tide blooms, the addition of inorganic nitrogen tends to inhibit Brown Tide blooms. Budget calculations indicate that the inorganic nitrogen supply from groundwater is 1–2 orders of magnitude higher than any other external source of nitrogen for this ecosystem. Biweekly time series data collected in 1995 demonstrate that Brown Tide blooms utilize dissolved organic nitrogen (DON) for growth, as evidenced by a large decrease in DON parallel with an increase in cell abundance. On an interannual basis, bloom intensity was also positively correlated with mean DON concentrations. We hypothesize that bloom initiation is regulated by the relative supply of inorganic and organic nitrogen, determined to a large extent by temporal variability in groundwater flow. The 1980s and 1990s were characterized by exceptionally high and interannually variable groundwater discharge, associated with a large-scale climate shift over the North Atlantic. This, coupled with the time-lagged discharge of groundwater with high nitrate concentrations resulting from increased fertilizer use and population increase during the 1960s and 1970s, may have been a key factor in the initiation of Brown Tide blooms in 1985.     

Can the EU agri-environmental aid program be extended into the coastal zone to combat eutrophication?

Eutrophication of coastal waters is a serious environmental problem with high costs for society globally. This is a development which demands immediate environmental action along many coastal sites. Since the 1980s, mussel farming has been recognized by Swedish environmental authorities as a possible measure to improve coastal water quality. Concepts and management strategies on how to increase mussel farming and thus combat coastal marine eutrophication has recently been developed in Sweden. The main principle of this development has been the implementation of nutrient trading as a management tool. This imposes demands on those who emit the pollution through the establishment of emission quotas, which are traded and bought by the emitter. The seller is a nutrient harvesting enterprise, e.g., a mussel farmer. This principle is particularly straightforward when the nutrients are discharged from a point source. When examining the nutrient supply from all diffuse sources, the situation is more complex. However, since the major part of the nutrient supply to coastal waters in many areas of Europe has its origin in agricultural operations, we suggest that the EU agro-environmental aid program could be extended into the coastal zone in order to combat eutrophication. In practice, this should involve support paid to mussel farming enterprises through their harvest of mussels (and thus their harvest of nutrients) in the same way as support is paid to agricultural farmers for operations that reduce nutrient leakage from their farmland. This is a simple, cost-effective and straightforward way of improving coastal water quality at many coastal sites that will, at the same time, provide coastal jobs. However, this eutrophication combat method depends on the EU agro-environmental aid program being extended beyond the shoreline. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

施用纳米碳对烤烟氮素吸收和利用的影响

为明确纳米碳在提高烤烟氮素吸收利用方面的效果,在盆栽条件下,研究了纳米碳不同用量对烤烟根系生长发育、干物质积累和氮素吸收利用的影响。结果表明,在常规肥料中添加纳米碳能够促进烤烟根系生长发育,明显提高烟株根系活力和单株根系生物量,增加植株干物质积累量。施用纳米碳增加了烤烟植株成熟期各器官氮素含量和积累量,而未明显影响氮素在植株不同器官的分配。施用纳米碳不仅增加了植株对肥料氮的吸收量,还增加了对土壤氮的吸收量,这与其促进烤烟根系生长发育、提高根系吸收能力有密切关系。纳米碳无论做基肥还是做追肥,均显著提高了氮肥利用率,提高幅度分别达到14.44%和9.62%,有效降低了氮素土壤残留和损失。     

Changes of nitrogen and phosphorus loads to European seas

During the last decades human activity has altered the natural cycle of nitrogen and phosphorus on a global scale, producing significant emissions to waters. In Europe, the amount of nutrients discharged from rivers to coastal waters as well as the effects of mitigation measures in place are known only partially, with no consistent temporal and spatial cover. In this study, we quantify the loads and concentration of nitrogen and phosphorus discharged in the European seas over the period 1985–2005, and we discuss their impact on coastal ecosystems. To support our analysis, a catchment database covering the whole of Europe was developed together with data layers of nutrients diffuse and point sources, and the statistical model green was used to estimate the annual loads of nitrogen and phosphorus discharged in all European seas. The results of this study show that during the last 20 years, Europe has discharged 4.1–4.8 Tg yr^?1 of nitrogen and 0.2–0.3 Tg yr^?1 of phosphorus to its coastal waters. We show that beside the North Sea and part of the Baltic Sea, annual nutrient exports have not changed significantly, in spite of the implementation of measures to reduce nutrient sources, and that the N : P ratio has increased steadily, especially in the North, Mediterranean and Atlantic seas. The response of river basins to changes in inputs was not linear, but influenced by climatic variations and nutrients previously accumulated in soils and aquifers. An analysis of the effects of European environmental policies shows that measures to reduce phosphorus were more successful that those tackling nitrogen and that policies aimed at point sources were more effective or more effectively implemented than those controlling pollution from diffuse sources. The increase of the N : P ratio could fuel eutrophication in N‐limited coastal ecosystems, reducing biodiversity and the ecosystem's resilience to future additional anthropogenic stress, such as climate change.     

减少农业对水体污染的对策与措施

水体富营养化是一个全球关注的问题。逐渐增加的化肥施用量和畜禽养殖业产生的粪便进一步引起营养流失,进而产生了N、P营养物质的不平衡。因此农业面源污染已被视为水体富营养化的主要污染源。本文简要地概述了农业面源污染对造成水体富营养化的危害,同时介绍了国内外防治农业面源污染的主要措施,包括面源控制措施和转移转化措施。指出了建立稳定、和谐与良性循环的农业生态系统是治理农业面源污染的长久之计。     

近30年中国滨海滩涂湿地变化及其驱动力

随着人类活动影响的不断加剧,滨海湿地正面临着退化的威胁。尤其是近三十年来,中国东部沿海地区经济发展迅速,中国滨海湿地在时空格局等方面发生了巨大改变。以Google Earth Pro(GEP)s遥感影像为数据源,基于Google Earth Engine(GEE)平台和随机森林分类方法,解译了1990—2020年中国滨海地区的遥感影像,提取不同年份滩涂湿地面积,分析了过去30年间滨海滩涂湿地空间分布变化,从自然原因和政策变化两个方面探讨了中国滨海滩涂湿地时空格局变化的驱动机制。研究表明,中国滨海滩涂湿地呈现总体减少的趋势,总面积减少了42.98%,其中光滩面积减少了46.30%,盐沼面积增加了4.95%。不同省份滩涂湿地面积变化总体趋势与全国一致,与国家政策紧密联系;但不同年份各省份因发展需求和压力不同,滩涂湿地的变化的进程有一定差异。泥沙沉积和水动力条件的变化是滩涂湿地变化的主要自然因素,方针政策的贯彻执行是滩涂湿地变化的重要人为因素,通过出台严格合理管控政策可以促进中国滨海滩涂湿地可持续发展。     

Regional nitrogen budgets and riverine N & P fluxes for the drainages to the North Atlantic Ocean: Natural and human influences

We present estimates of total nitrogen and total phosphorus fluxes in rivers to the North Atlantic Ocean from 14 regions in North America, South America, Europe, and Africa which collectively comprise the drainage basins to the North Atlantic. The Amazon basin dominates the overall phosphorus flux and has the highest phosphorus flux per area. The total nitrogen flux from the Amazon is also large, contributing 3.3 Tg yr^–1 out of a total for the entire North Atlantic region of 13.1 Tg yr^–1 . On a per area basis, however, the largest nitrogen fluxes are found in the highly disturbed watersheds around the North Sea, in northwestern Europe, and in the northeastern U.S., all of which have riverine nitrogen fluxes greater than 1,000 kg N km^–2 yr^–1.Non-point sources of nitrogen dominate riverine fluxes to the coast in all regions. River fluxes of total nitrogen from the temperate regions of the North Atlantic basin are correlated with population density, as has been observed previously for fluxes of nitrate in the world's major rivers. However, more striking is a strong linear correlation between river fluxes of total nitrogen and the sum of anthropogenically-derived nitrogen inputs to the temperate regions (fertilizer application, human-induced increases in atmospheric deposition of oxidized forms of nitrogen, fixation by leguminous crops, and the import/export of nitrogen in agricultural products). On average, regional nitrogen fluxes in rivers are only 25% of these anthropogenically derived nitrogen inputs. Denitrification in wetlands and aquatic ecosystems is probably the dominant sink, with storage in forests perhaps also of importance. Storage of nitrogen in groundwater, although of importance in some localities, is a very small sink for nitrogen inputs in all regions. Agricultural sources of nitrogen dominate inputs in many regions, particularly the Mississippi basin and the North Sea drainages. Deposition of oxidized nitrogen, primarily of industrial origin, is the major control over river nitrogen export in some regions such as the northeastern U.S.Using data from relatively pristine areas as an index of change, we estimate that riverine nitrogen fluxes in many of the temperate regions have increased from pre-industrial times by 2 to 20 fold, although some regions such as northern Canada are relatively unchanged. Fluxes from the most disturbed region, the North Sea drainages, have increased by 6 to 20 fold. Fluxes from the Amazon basin are also at least 2 to 5 fold greater than estimated fluxes from undisturbed temperate-zone regions, despite low population density and low inputs of anthropogenic nitrogen to the region. This suggests that natural riverine nitrogen fluxes in the tropics may be significantly greater than in the temperate zone. However, deforestation may be contributing to the tropical fluxes. In either case, projected increases in fertilizer use and atmospheric deposition in the coming decades are likely to cause dramatic increases in nitrogen loading to many tropical river systems.     

The development of policy approaches for reducing nitro-gen pollution to coastal waters of the USA

Two-thirds of the coastal rivers and bays in the United States are degraded from nutrient pollution, and nitrogen inputs these waters continue to increase. The nitrogen comes from a variety of sources, including runoff from agricultural fields, concentrated animal feeding operations, atmospheric deposition from fossil fuel combustion, and sewage and septic wastes. Technical solutions for nitrogen pollution exist at reasonable cost. That most of these solutions have not yet been implemented to any significant extent across the United States suggests that new policy approaches are necessary. The best solution may involve a combination of voluntary and mandatory approaches, applying different approaches to different sources of nitrogen pollution. A watershed-based approach that relies heavily on voluntary mechanisms (such as crop-yield insurance to reduce over-fertilization) is likely to be the most effective for some sources of nitrogen (such as runoff from agricultural fields), while a uniform national regulatory approach may be better for others (such as NOx emissions from fossil fuel combustion). Implementation of management strategies should be carefully coupled to monitoring programs to assess the effectiveness of these strategies. While both nitrogen and phosphorus are important to control, the focus should be on nitrogen management, in part because nitrogen is more generally the causal agent of coastal eutrophication. Also, while nitrogen-control practices tend to also reduce phosphorus pollution, phosphorus-control practices often have little effect on nitrogen. Although current scientific and technical knowledge is sufficient to begin to make substantial progress toward solving coastal nitrogen pollution, progress will be made more quickly and more cost effectively with increased investment in appropriate scientific research.     

The development of policy approaches for reducing nitrogen pollution to coastal waters of the USA

Two-thirds of the coastal rivers and bays in the United States are degraded from nutrient pollution, and nitrogen inputs these waters continue to increase. The nitrogen comes from a variety of sources, including runoff from agricultural fields, concentrated animal feeding operations, atmospheric deposition from fossil fuel combustion, and sewage and septic wastes. Technical solutions for nitrogen pollution exist at reasonable cost. That most of these solutions have not yet been implemented to any significant extent across the United States suggests that new policy approaches are necessary. The best solution may involve a combination of voluntary and mandatory approaches, applying different approaches to different sources of nitrogen pollution. A watershed-based approach that relies heavily on voluntary mechanisms (such as crop-yield insurance to reduce over-fertilization) is likely to be the most effective for some sources of nitrogen (such as runoff from agricultural fields), while a uniform national regulatory approach may be better for others (such as NO_x emissions from fossil fuel combustion). Implementation of management strategies should be carefully coupled to monitoring programs to assess the effectiveness of these strategies. While both nitrogen and phosphorus are important to control, the focus should be on nitrogen management, in part because nitrogen is more generally the causal agent of coastal eutrophication. Also, while nitrogen-control practices tend to also reduce phosphorus pollution, phosphorus-control practices often have little effect on nitrogen. Although current scientific and technical knowledge is sufficient to begin to make substantial progress toward solving coastal nitrogen pollution, progress will be made more quickly and more cost effectively with increased investment in appropriate scientific research.     

Uneven rise in N inputs to the Lake Michigan Basin over the 20th century corresponds to agricultural and societal transitions

By constructing nitrogen (N) budgets from 1880 to 2002 for watersheds that have undergone urbanization, intensive agricultural specialization or experienced minimal change, we document an uneven timeline of increase in anthropogenic N inputs. N loading to the watersheds of the Lake Michigan Basin grew six-fold from 1880 to 2002, peaking in 1987. Human activities influenced N inputs as early as 1880, and the magnitude and timing of increase differed markedly across regions in accord with population growth, land use, and type of agriculture. The greatest increase occurred from 1950 to 1980, corresponding with rapidly accelerating use of artificial fertilizers, but increases in atmospheric deposition and shifting patterns in crop and livestock production also affected trends. Net anthropogenic N inputs have changed little since about 1980, showing a modest decline due to a leveling out of fertilizer use and greater export of animal feed and products. Using a model that predicts riverine N export from watershed N loadings and river discharge, we found that river TN fluxes from all tributaries increased approximately threefold from 1900 to 2000 but have stabilized or declined over the past two decades, consistent with national surveys that show near-constant or declining riverine TN concentrations. For the LMB, the past two decades has been a period of relative stasis in N inputs to its terrestrial systems and N export from watersheds. This retrospective analysis also points to the challenge of forecasting future trends in N budget terms, which can both increase and decline in response to policy and societal transitions.     

The development of policy approaches for reducing nitrogen pollution to coastal waters of the USA

Two-thirds of the coastal rivers and bays in the United States are degraded from nutrient pollution, and nitrogen inputs these waters continue to increase. The nitrogen comes from a variety of sources, including runoff from agricultural fields, concentrated animal feeding operations, atmospheric deposition from fossil fuel combustion, and sewage and septic wastes.Technical solutions for nitrogen pollution exist at reasonable cost. That most of these solutions have not yet been implemented to any significant extent across the United States suggests that new policy approaches are necessary. The best solution may involve a combination of voluntary and mandatory approaches, applying different approaches to different sources of nitrogen poilution. A watershed-based approach that relies heavily on voluntary mechanisms (such as crop-yield insurance to reduce over-fertilization) is likely to be the most effective for some sources of nitrogen (such as runoff from agricultural fields), while a uniform national regulatory approach may be better for others (such as NOx emissions from fossil fuel combustion). Implementation of management strategies should be carefully coupled to monitoring programs to assess the effectiveness of these strategies. While both nitrogen and phosphorus are important to control, the focus should be on nitrogen management, in part because nitrogen is more generally the causal agent of coastal eutrophication. Also, while nitrogen-control practices tend to also reduce phosphorus pollution, phosphorus-control practices often have little effect on nitrogen.Although current scientific and technical knowledge is sufficient to begin to make substantial progress toward solving coastal nitrogen pollution, progress will be made more quickly and more cost effectively with increased investment in appropriate scientific research.     

Rapid Communication: Climatic Control on Eutrophication of the Hudson River Estuary

Eutrophication is arguably the biggest pollution problem facing estuaries globally, with extensive consequences including anoxic and hypoxic waters, reduced fishery harvests, toxic algal blooms, and loss of biotic diversity. However, estuaries vary greatly in their susceptibility to eutrophication. The Hudson River estuary receives very high levels of nutrient inputs yet in the past has shown relatively low rates of phytoplankton productivity and is generally considered to be only moderately susceptible to eutrophication. Here, we show that eutrophication and primary production in the Hudson estuary can increase dramatically in response to climatic variation and lowered freshwater discharge from the watershed. During dry summer periods in 1995 and 1997, rates of primary production were substantially higher than those measured during the 1970s, when freshwater discharge tended to be high. In the Hudson, low freshwater discharge increases waterresidence times and stratification and deepens the photic zone, all of which (alone or in combination) could lead to the observed increase in primary production. Our data, along with the prediction of most climate change models that freshwater discharge will be lower in the future during the summer in the northeastern US, suggest that the Hudson will become more susceptible to eutrophication. Eutrophication in an estuary is a complex process, and climate change is likely to affect each estuary differently due to interactions with nutrient loadings and physical circulation. Hence, it is essential to consider the effects of climate change in the context of individual estuarine functioning to successfully manage eutrophication in the future. Received 22 December 1999; accepted 28 December 1999.     

Effects of anthropogenic nitrogen discharge on dissolved inorganic nitrogen transport in global rivers

Excess nutrients from fertilizer application, pollution discharge, and water regulations outflow through rivers from lands to oceans, seriously impacting coastal ecosystems. A reasonable representation of these processes in land surface models and River Transport Models (RTMs) is very important for understanding human–environment interactions. In this study, the schemes of riverine dissolved inorganic nitrogen (DIN) transport and human activities including nitrogen discharge and water regulation, were synchronously incorporated into a land surface model coupled with a RTM. The effects of anthropogenic nitrogen discharge on the DIN transport in rivers were studied based on simulations of the period 1991–2010 throughout the entire world, conducted using the developed model, which had a spatial resolution of about 1° for land processes and 0.5° for river transport, and data on fertilizer application, point source pollution, and water use. Our results showed that rivers in western Europe and eastern China were seriously polluted, on average, at a rate of 5,000–15,000 tons per year. In the Yangtze River Basin, the amount of point source pollution in 2010 was about four times more than that in 1991, while the amount of fertilizer used in 2010 doubled, which resulted in the increased riverine DIN levels. Further comparisons suggested that the riverine DIN in the USA was affected primarily by nitrogen fertilizer use, the changes in DIN flow rate in European rivers was dominated by point source pollution, and rivers in China were seriously polluted by both the two pollution sources. The total anthropogenic impact on the DIN exported to the Pacific Ocean has increased from 10% to 30%, more significantly than other oceans. In general, our results indicated that incorporating the schemes of nitrogen transport and human activities into land surface models could be an effective way to monitor global river water quality and diagnose the performance of the land surface modeling.     

Environmental changes in Lake Taihu during the past century as recorded in sediment cores

The Lake Taihu drainage basin is an economically developed area with some of the highest population densities in China. The lake has deteriorated due to ecological destruction and eutrophication. Three short sediment cores from eastern, northeastern and southwestern Lake Taihu were collected. Total organic carbon (TOC), total nitrogen (TN), pigments, elements and particle size were analyzed for the purpose of understanding past trophic status and pollution levels. Sedimentation rates were based on ¹³⁷Cs or ²¹⁰Pb methods. Results indicated that sediment particle size became coarser since the 1920s, and the lake was contaminated by heavy metals, such as Cu and Zn, since the 1970s. A remarkable increase in eutrophication since the 1980s due to increased loading of untreated effluents from industry, agriculture and urbanization is reflected by total organic carbon, total nitrogen and pigments in the studied cores. However the onset times of eutrophication in different parts of Lake Taihu were not synchronous.     

Estuarine benthic ecology: A European perspective

The study of benthic ecology within European estuaries is discussed. The history of estuarine science, and the definition of an estuary is briefly reviewed. Estuarine benthic ecology is considered with regard to its geographical, economic and political context. It is shown that much recent study has been motivated by attempts to clean up estuaries, which were polluted after decades, or even centuries of pollution. Much has been achieved in the control of pollution, and many estuaries show clear signs of recovery. Particular focus has been on the estuaries entering the North Sea, with the realization that it is not the North Sea that is polluted, but its estuaries. The scientific appraisal of the benthos of estuaries has been particularly assisted by the ecosystem approach, which has both aided our understanding of their function as well as answering some of the questions posed by the impact of mankind. The European Union is identified as a powerful factor in benthic ecology, either through legislation or through the encouragement of collaborative programs, some of which have been particularly important in identifying common factors across a wide geographical spread of estuaries. It is concluded that in general estuaries have got cleaner, but that many problems remain, ranging from eutrophication through to sea-level change. The future of estuarine benthic ecology lies in meeting the new challenges.     

Agriculture, fertilizers and life history of a coastal seabird

1. Leakage of fertilizers from farmland has affected levels of nitrogen and phosphorus in many coastal areas, reducing limitation of primary productivity with consequences for timing and magnitude of the annual peak in phytoplankton and zooplankton. Such changes in nutrient availability may have affected temporal patterns of abundance of marine invertebrates and vertebrates that are the main prey of seabirds. 2. We investigated the extent to which changes in the use of fertilizers by farmers affected timing of breeding, clutch size, recruitment and longevity of a coastal seabird, the Arctic tern Sterna paradisaea Pont., in Denmark. 3. Timing of breeding advanced with the increase in use of fertilizers, with an effect as a consequence of a phenotypic response of individuals exposed to different levels of fertilizers. 4. Annual mean clutch size increased with the amount of fertilizer. While individual Arctic terns increased their clutch size with fertilizer level, there was no evidence of individual Arctic terns in different years changing their clutch size in response to changes in fertilizer use. 5. Annual recruitment rate, estimated as the proportion of young that were subsequently recovered as adults, was related to fertilizer use. 6. Mean longevity, estimated as the maximum age of adult individuals, decreased in response to fertilizer use. 7. These findings provide evidence of fertilizer use in agriculture having significant indirect effects on timing of reproduction, clutch size, recruitment and longevity of a seabird.