River water and nutrient discharges in the Northern Adriatic Sea: Current importance and long term changes

Runoff and nutrient transport by rivers were analysed in the Northern Adriatic continental shelf, in order to evaluate their interannual and multidecal variability, as well as their current contribution to determine freshwater and nutrient budgets in this marine region. During the years 2004-2007, the runoff in the basin (34.1-64.6 km³ yr⁻¹) was highly imbalanced, being 84% of freshwater discharged along the western coast, because of the contributions of Po, Adige and Brenta rivers. In the northern and eastern sections of the coast, freshwater discharge by rivers was less important (10 and 6%, respectively), but not negligible in determining the oceanographic properties at sub-regional scales. The oscillations of the transport of biogenic elements (124-262×10³ t N yr⁻¹ for TN, 72-136×10³ t N yr⁻¹ for DIN, 4.5-11.1×10³t P yr⁻¹ for TP, 2.2-3.5×10³ t P yr⁻¹ for PO₄ and 104-196×10³ t Si yr⁻¹ for SiO₂) were strictly dependant to the differences in the annual runoff. A strong excess of N load in comparison to P load characterised all rivers, both in inorganic nutrient (DIN/PO4=37-418) and total (TN/TP=48-208) pools, particularly in the northern and eastern areas of the basin.The annual runoff showed significant oscillations for Po on multidecadal time scale, whereas a general decrease (−33%) was observed for the other N Adriatic rivers as the recent discharges were compared to those before the 1980s. During the dry years 2005-2007, a strong reduction of river water flows and nutrient loads was experienced by the N Adriatic ecosystem with respect to years characterised by medium-high regimes. An increased frequency of similar drought periods, due to ongoing climate changes or to a larger human usage of continental waters, would be easily able to significantly change the biogeochemistry of this basin.     

Deep water ventilation traced by <Emphasis Type="Italic">Synechococcus</Emphasis> cyanobacteria

The paper describes a finding of photoautotroph cyanobacteria Synechococcus in deep Adriatic waters during the spring of 2006. The maximum abundance in early May was positioned at 800 m, being of order of the values referred for the surface waters in the Adriatic Sea. The deep abundance maximum has been associated to the fast ventilation of deep Adriatic waters, usually occurring during wintertime strong cooling events. Two processes were detected: (1) deep convection in the South Adriatic Pit (SAP) and (2) density current going downslope. The first process was responsible for bringing the cyanobacteria down to 600-m depth in the area of convection, and the second one triggered the downslope transport of the cyanobacteria to the SAP very bottom. The depletion rate of Synechoccocus cyanobacteria in an extremely hostile environment has been computed to equal about 1 month.     

Impact of fish farming on the distribution of phosphorus in sediments in the middle Adriatic area

During the last decade, intensive fish farming developed along the central Croatian coast, creating a need to study and evaluate its potential influence on unaffected sites. We considered phosphorus as an indicator of the influence of fish farming and investigated the distribution of phosphorus forms in sediment from several fish farms and marine areas of different trophic status in the middle Adriatic. Analyses of samples were performed with modified SEDEX techniques. Our results indicated that authigenic apatite phosphorus showed no significant differences among the investigated stations, while organic phosphorus concentrations reflected the trophic status of the station area. Below-cage sediment was characterized by enhanced fish debris phosphorus and low detrital apatite phosphorus concentrations, while sediment from an anthropogenically influenced bay showed the highest values of iron bound phosphorus species. Among the different P fractions, fish debris phosphorus proved to be the most sensitive indicator of the influence of fish farming on marine sediment.     

Variability of water mass properties in the last two decades in the South Adriatic Sea with emphasis on the period 2006-2009

Spatially averaged temperature and salinity profiles from individual cruises between 1990 and 2009 were analysed to outline the temporal evolution of water mass properties in the deep convection site in the South Adriatic Pit (SAP). The long-term variability in thermohaline conditions has been explained and related to a close feedback mechanism between the Ionian and the Adriatic Sea. Prominent influences of the Eastern Mediterranean Transient are manifested in changes in the vertical temperature and salinity patterns in the South Adriatic, and the whole studied period was divided into three stages according to the main thermohaline characteristics: 1990-1995, 1995-2004 and the last period from 2005 onwards.Particular attention was given to data collected during 2006-2009, which permitted us to situate the actual thermohaline properties in the context of the decadal variability. This last period was characterised by a very low production of dense water in the northern basin during 2007, while from winter 2008 high production of North Adriatic Deep Water (NAdDW) and Adriatic Deep Water (AdDW) in the northern and southern basins, respectively, was observed. Finally, we used the Optimum Multiparameter Analysis (OMP) to identify the percentages of the different water masses contained in the SAP, and this highlighted some differences between two recent periods studied (2007 and 2008) and the production of dense waters.     

On the contributions of atmospheric pressure and wind to daily sea level in the northern Adriatic Sea

Daily sea level variability in the Adriatic Sea is studied from different data sets using Empirical Orthogonal Functions, in connection with atmospheric pressure and wind stress. The first mode explains 56–69% of total variance and consists of uniform sea level variability all over the basin, correlated with atmospheric pressure through the inverse barometer effect. The second mode explains 13–16% of variance and accounts for an along-basin sea level gradient, which is correlated with the meridional wind stress component. The first two Principal Components are used as proxies to pressure- and wind-induced components of storm surges in the northern Adriatic. The analysis of the frequency of the most intense events in the 1957–2005 period shows that the wind contribution to storm surges has decreased, while no significant trends are found in the contribution of atmospheric pressure.     

Towards the application of the Water Framework Directive in Italy: Assessing the potential of benthic tools in Adriatic coastal transitional ecosystems

The potential of four benthic indices (AMBI/M-AMBI, BENTIX, BITS) was assessed in Italian coastal transitional ecosystems. The community composition showed a strong dominance of lagoonal, tolerant species, and out of more of 400 species found, only about 40 taxa were dominant. The full agreement of the four indices on an undegraded (Good or better) or degraded (Moderate or worse) status occurred only in 32.3% of stations. This study evidenced that BENTIX is inappropriate for eutrophic Adriatic lagoons, and that in such environments M-AMBI classification is actually too much dependent on diversity and richness, and seems unable to capture some peculiarities of benthic assemblages in transitional waters. AMBI and BITS gave similar classifications despite the different level of taxonomic identification needed. The unmodified use of these indices might impair accurate assessment of ecological quality status and decision-making on the managers’ point of view.     

Decadal-scale variations of water mass properties in the deep Weddell Sea

Data from cruises between 1989 and 2003 with FS Polarstern were used to construct section-wide potential temperature and salinity time series of the main water masses in the Weddell Gyre. In tandem with these CTD data, two time series between 1989 and 1995 are presented from moored instruments in the central Weddell Sea. The regional and methodological consistency of the dataset allows us to quantify variations which are not visible in less homogeneous datasets. The data reveal significant temperature and salinity variations of the Warm Deep Water and the Weddell Sea Bottom Water on a decadal time scale. The longest time series were obtained at the prime meridian. Here warming is observed in the Warm Deep Water from 1992 to 1998 followed by cooling. In the Weddell Sea proper, measurements of instruments moored in the Weddell Sea Bottom Water layer recorded a temperature increase over 6 years at a rate of 0.01 °C a^–1. After the mooring period, CTD casts in 1998 point to a weakening of the trend. The warming trend in the bottom water occurs over most of the Weddell Sea, as detected in the additional CTD surveys. The variations are close to the detection level in the voluminous Weddell Sea Deep Water. The initial warming trend of the Warm Deep Water is consistent with warming trends reported in literature of subsurface waters of the Antarctic Circumpolar Current. The reversal of the trend in the Weddell Sea seems to be related to variations of the atmospheric conditions which can affect both the intrusion of Circumpolar Deep Water from the north and the circulation of the Weddell Gyre. Because the Warm Deep Water is the major source water for the formation of deep and bottom water in the Weddell Sea, it is suggested that its increase in temperature and salinity is likely to at least partly cause the variations which were observed in the bottom water.Responsible Editor: Jörg-Olaf Wolff     

Integrating long-term water and sediment pollution data, in assessing chemical status within the European Water Framework Directive

The European Water Framework Directive (WFD) establishes a framework for the protection and improvement of estuarine (transitional) and coastal waters, attempting to achieve good water status by 2015; this includes, within the assessment, biological and chemical elements. The European Commission has proposed a list of priority dangerous substances (including metals such as Cd, Hg, Ni and Pb), with the corresponding list of environmental quality standards (EQS), to assess chemical status, but only for waters. In this contribution, a long-term (1995–2007) dataset of transitional and coastal water and sediment trace elements concentrations, from the Basque Country (northern Spain), has been used to investigate the response of these systems to water treatment programmes. Moreover, the approach proposed in the WFD, for assessing water chemical status (the ‘one out, all out’ approach), is compared with the integration of water and sediment data, into a unique assessment. For this exercise, background levels are used as reference conditions, identifying the boundary between high and good chemical status. EQS are used as the boundary between good and moderate chemical status. This contribution reveals that the first approach can lead to misclassification, with the second approach representing the pattern shown by the long-term data trends. Finally, the management implications, using each approach are discussed.     

Comparing efficacy of different taxonomic resolutions and surrogates in detecting changes in soft bottom assemblages due to coastal defence structures

Sandy shores on the West coast of the North Adriatic Sea are extensively protected by different types of defence structures to prevent coastal erosion. Coastal defence schemes modify the hydrodynamic regime, the sediment structure and composition thus affecting the benthic assemblages. This study examines the effectiveness in detecting changes in soft bottom assemblages caused by coastal defence structures by using different levels of taxonomic resolution, polychaetes and/or bivalves as surrogates and different data transformations. A synoptic analyses of three datasets of subtidal benthic macrofauna used in studies aimed at assessing the impact of breakwaters along the North Adriatic coast has been done. Analyses of similarities and correlations between distance matrices were done using matrices with different levels of taxonomic resolution, and with polychaetes or bivalves data alone. Lentidium mediterraneum was the most abundant species in all datasets. Its abundance was not consistently related to the presence of defence structures. Moreover, distribution patterns of L. mediterraneum were masking the structure of the whole macrofaunal assemblages. Removal of L. mediterraneum from the datasets allowed the detection of changes in benthic assemblages due to coastal defences. Analyses on different levels of taxonomic resolution showed that the level of family maintained sufficient information to detect the impacts of coastal defence structures on benthic assemblages. Moreover, the outcomes depended on the transformation used. Patterns of distribution of bivalves, used as surrogates, showed low correlations with the patterns of the total macrofaunal species assemblages. Patterns of polychaetes, if identified to the species or genus level showed higher correlations with the whole dataset. However, the identification of polychaetes to species and genus level is as costly as the identification of all macrobenthic taxa at family level.This study provided additional evidences that taxonomic sufficiency is a useful tool in environmental monitoring, also in investigations on the impacts of coastal defence structures on subtidal macrofauna. The use of coarser taxonomic level, being time-efficient, would allow improving sampling designs of monitoring programs by increasing replication in space and time and by allowing long term monitoring studies.     

The expansion and decline of charophyte communities in lakes within the Sejny Lake District (north-eastern Poland) and changes in water chemistry

Over the last 25 years, considerable changes have been observed in the littoral vegetation of 11 lakes within the Sejny Lake District. In eight lakes (Dowcień, Jurkowo, Kunis, Miałkie, Pilwie, Płaskie, Wiłkokuk, Zelwa) where Chara species dominated, their communities declined or disappeared completely. In four of these lakes (Dowcień, Jurkowo, Kunis and Miałkie), charophytes were replaced by communities of the class Potametea (mainly Nupharo-Nymphaeetum albae and Ceratophylletum demersi). In three other lakes (Pilwie, Płaskie and Wiłkokuk), the area covered by charophyte communities decreased. In Lake Zelwa, Charetum rudis and Charetum jubatae disappeared while Charetum tomentosae and Charetum fragilis expanded. A total area of charophyte communities remained approximately the same. A considerable increase in the water total hardness and concentration was noted in each of the eight lakes. In most of them increased levels of dissolved organic matter (measured as COD-KMnO₄) and pH were detected as well. However, the increase in the concentration was smaller in Lakes Wiłkokuk and Zelwa in which only slight changes in the vegetation were observed. In the above two lakes, the concentration of dissolved organic matter decreased and low water colour values are now noted. In three lakes (Długie, Dmitrowo and Gajlik), the charophyte communities tended to expand under the condition of moderate or high (Lake Długie) concentration, while dissolved organic matter concentrations were low. These lakes are also characterized by low values of colour. Charophyte communities may persist in lakes for a long period of time even when there is a moderate increase in concentration until the colour of water distinctly increases (>20 mg Pt L⁻¹).     

Performance of operational systems with respect to water level forecasts in the Gulf of Finland

This paper is devoted to the validation of water level forecasts in the Gulf of Finland. Daily forecasts produced by four setups of operational, three-dimensional Baltic Sea oceanographic models are analyzed using statistical means and are compared with water level observations at three Finnish stations located on the northern coast of the Gulf of Finland. The overall conclusion is that the operational systems were skillful in forecasting water level variations during the study period from November 1, 2003, to January 31, 2005. The factors causing differences between the water level forecasts of different models are discussed as well. An important task of operational sea level forecasting services is to provide accurate and early information about extreme water levels, both positive and negative surges. During the study period, two major winter storms occurred which caused coastal flooding in the region. According to our analysis, the operational models forecast the rise of water levels during these events rather successfully. Nowadays, operational forecasts can provide early warnings of extreme water levels at least 1 day in advance, which may be regarded as a minimum requirement for an operational forecasting system. The paper concludes that the models generally performed very well, with over 93% of the hourly water level forecasts found to be within the range of ±15 cm of the observed water levels, and with the timing of the water level peaks accurately predicted. Further discussion and studies dealing with the assessment of the skills of both operational meteorological and oceanographic forecasts, especially in connection with rare surge events, will be necessary. Skill assessment of operational oceanographic models would be relatively easy if acceptable error limits or a quality system was developed for the Baltic Sea operational models.     

Ecosystem response to regulatory and management actions: The southern California experience in long-term monitoring

Billions of dollars have been invested over the past 35 years in reducing pollutant emissions to coastal environments. Evaluation of the effectiveness of this investment is hampered by the lack of long-term consistent data. A rare opportunity exists in southern California to evaluate the effectiveness of management actions by analyzing long-term monitoring of effluent, sediment, benthos, and fish and comparing this trend data to periodic regional surveys of environmental condition. In this paper, we ask the question “have improvements in effluent quality in response to environmental regulation translated into improvements in the receiving environment?” Results indicate that management actions directed at reducing mass emissions from wastewater treatment plants (POTWs) have resulted in substantial improvement in aquatic communities. However, the magnitude and timing of response varies by indicator suggesting that use of multiple assessment endpoints is necessary to adequately interpret trends. Reductions in the effect of POTW effluent have allowed managers to shift resources to address other contaminant sources such as stormwater and resuspension of legacy pollutants.     

Trace metal dynamics in the water column and pore waters in a temperate tidal system: response to the fate of algae-derived organic matter

Tidal and seasonal behaviour of the redox-sensitive trace metals Mn, Fe, Mo, U, and V have been investigated in the open-water column and shallow pore waters of the backbarrier tidal flats of the island of Spiekeroog (Southern North Sea) in 2002 and 2007. The purpose was to study the response of trace metal cycles on algae blooms, which are assumed to cause significant changes in the redox state of the entire ecosystem. Trace metal data were complemented by measurements of nutrients and enumeration of algae cells in 2007. Generally, Mn and V show a tidal cyclicity in the water column with maximum values during low tide which is most pronounced in summer due to elevated microbial activity in the sediments. Mo and U behave almost conservatively throughout the year with slightly increasing levels towards high tide. Exceptions are observed for both metals after summer algae blooms. Thus, the seasonal behaviour of the trace metals appear to be significantly influenced by productivity in the water column as the occurrence of algae blooms is associated with an intense release of organic matter (e.g. transparent exopolymer particles, TEP) thereby forming larger organic-rich aggregates. Along with elevated temperatures in summer, the deposition of such aggregates favours microbial activity within the surface sediments and release of DOC, nutrients and trace metals (Mn, Mo and V) during the degradation of the aggregates. Additionally, pronounced reducing conditions lead to the reduction of Mn(IV)-oxides and Fe(III)-(oxihydr)oxides, thereby releasing formerly scavenged compounds as V and phosphate. Therefore, pore-water profiles show significant enrichments in trace metals especially from July to September. Finally, the trace metals are released to the open water column via draining pore waters (esp. Mo, Mn, and V) and/or fixed in the sediment as sulphides (Fe, Mo) and bound to organic matter (U). Non-conservative behaviour of Mo in oxygenated seawater, first observed in the investigation area by Dellwig et al. (Geochim Cosmochim Acta 71:2745–2761, 2007a), was shown to be a recurrent phenomenon which is closely coupled to bacterial activity after the breakdown of algae blooms. In addition to the postulated fixation of Mo in oxygen-depleted micro-zones of the aggregates or by freshly formed organic matter, a direct removal of Mo from the water column by reduced sediment surfaces may also play an important role.     

利用背景噪声研究紫坪铺水库水位加卸载对库区地下介质波速的影响

基于2005年1月1日~2008年1月1日紫坪铺台网及YZP台连续波形资料,利用噪声互相关技术研究了紫坪铺水库区域在蓄水、泄水过程中库区介质的变化特征,同时对可能的渗透过程进行了讨论。使用移动窗口互谱方法计算了库区台站对之间的相对波速变化。结果表明,在紫坪铺水库的3次大规模蓄水及2次泄水过程中,地下介质相对波速变化与水位变化之间存在较为明显的相关性,且在时间上有一定延迟,其可能与水的渗透有关。分析认为蓄水对浅层介质产生的作用最快,影响最大,波速的变化是蓄水产生的压力及渗透共同作用的结果。在第1次蓄水时,压力起主要作用,后2次蓄水时,渗透起主要作用,且渗透作用已影响至深达8km左右的断层。     

Using fuzzy operators to address the complexity in decision making of water resources redistribution in two neighboring river basins

This paper emphasizes the use of fuzzy sets for incorporating objective and subjective uncertainties to address coevolutionary alignment of a suite of water resources redistribution alternatives in a transboundary channel–reservoir system. The highlighted decision making complexity arises from the interactions between two neighboring water systems (i.e., the Tseng-Wen and Kao-Ping River Basins, South Taiwan) where a pending diversion plan has been under intensive debate for over a decade. While the local stakeholders make uncertain science linked with uncertain politics resulting in endless delay of the diversion plan, the environmental advocacy groups stress the increasing concern of loss of biological integrity due to changes of land use when sharing water resources across the boundary. Consequently, there is a need to generate a novel integration that enables us to consider a vast number of internal weirs, water intakes, reservoirs, drainage ditches, and transfer pipelines within the basin and bring out the connectivity via diversion between these two neighboring river basins under uncertainty. To explore the managerial implications with varying risk perception and risk attitude, four types of fuzzy operators tailored for the fuzzy multi-objective decision analysis depict greater flexibility in representing the complexity of possible trade-offs among those alternatives. These trade-offs in the multi-objective evaluation context are constrained by physical, chemical, socioeconomic, managerial, and technical factors reflecting the needs for adaptive water resources management. Findings indicates that the use of fuzzy operators is instructive, which could provide unique guidance for enlightening the potential barriers in sustainable water resources management at the regional scale.     

长江中游城市群水资源承载力时空格局及耦合协调性

长江中游城市群是实施生态优先绿色发展战略的重点区域,从水资源承载系统内的水资源、社会、经济、生态环境4个子系统中选取24项指标构建水资源承载力评价体系,综合运用改进熵权TOPSIS模型、空间自相关分析和耦合协调发展模型定量评价2012-2018年长江中游城市群水资源承载力时空变化过程及子系统间的耦合协调性.结果表明,（1）长江中游城市群整体水资源承载力水平表现为：缓慢上升（2012-2015年）、下降（2015-2017年）、再上升的趋势（2017-2018年）;（2）水资源承载力的空间差异不明显（仅2016年差异显著）,武汉城市圈水资源承载力的空间差异相对较大且呈现低值包围高值的空间分布特征;（3）各城市生态环境子系统承载力得分较为均衡,但其他子系统的承载力均差异较大;（4）影响水资源承载力的主要因素依次为城市污水处理厂日处理能力、人均GDP、城镇化率、第三产业比重和人均水资源量;（5）长江中游城市群水资源承载系统的耦合协调度总体处于中等水平,且水资源承载力与耦合协调度有极强的正相关关系.研究结果可为长江中游城市群水资源承载力改善及水资源优化配置提供依据.     

Diatom thanatocoenosis in a middle Galician Ría: Spatial patterns and their relationship to the seasonal diatom cycle in the water column and hydrographic conditions

Modern diatom distribution patterns in the surface sediment of the Ferrol Ría and their relationship to the hydrography and diatom patterns in the water column were studied to determine the hydrographic influence on the record of these biogenic components. Diatom abundance in the water column was assessed for different oceanographic periods and compared with the biosiliceous sedimentary record. Very low abundances were found in the water column during the winter, whereas in spring and summer, diatoms proliferated. Chaetoceros spp. formed the bulk of the water column community during spring and summer, followed by Thalassionema nitzschioides and Rhizosolenia spp. Nitzschia longissima represented a significant portion of the winter assemblage, together with Paralia sulcata and benthic taxa. Leptocylindrus danicus, N. longissima and Skeletonema costatum characterized the autumn campaign, when stratification of the waters occurs, with L. danicus being especially abundant in the outer ría.Seasonal hydrographic and associated productivity patterns govern the abundance and assemblage of the diatoms preserved in surface sediments. Samples located in the inner ría area and its margins exhibited the highest abundances of diatoms, and were primarily dominated by benthic species. The freshwater group, crysophycean cysts and phytoliths were present in the landward stations influenced by river runoff. The middle ría was characterized by P. sulcata and Thalassiosira spp., with minor occurrences of the benthic and freshwater group. Chaetoceros R.S., L. danicus R.S. and T. nitzschioides typified the outer ría, an assemblage that corresponds to nutrient-rich coastal areas of high productivity influenced by oceanic waters, demonstrating the impact of oceanic waters flowing into the embayment due to enhanced tidal mixing through the narrow channel. Therefore, sediment diatom assemblages reflect diatom production patterns in the water column of the Ría. However, we must proceed with caution when interpreting the paleorecord in the inner area due to the high contribution of allochthonous taxa, which is indicative of low water depths. This paper contributes to a better understanding of diatom thanatocoenosis in the Galician Rías, where very few studies of this kind have been done to date.     

A sensitivity analysis of lake water level response to changes in climate and river regimes

Lake water level regimes are influenced by climate, hydrology and land use. Intensive land use has led to a decline in lake levels in many regions, with direct impacts on lake hydrology, ecology and ecosystem services. This study examined the role of climate and river flow regime in controlling lake regimes using three different lakes with different hydraulic characteristics (volume-inflow ratio, CIR). The regime changes in the lakes were determined for five different river inflows and five different climate patterns (hot-arid, tropical, moderate, cold-arid, cold-wet), giving 75 different combinations of governing factors in lake hydrology. The input data were scaled to unify them for lake comparisons. By considering the historical lake volume fluctuations, the duration (number of months) of lake volume in different ‘wetness’ regimes from ‘dry’ to ‘wet’ was used to develop a new index for lake regime characterisation, ‘Degree of Lake Wetness’ (DLW). DLW is presented as two indices: DLW₁, providing a measure of lake filling percentage based on observed values and lake geometry, and DLW₂, providing an index for lake regimes based on historical fluctuation patterns. These indices were used to classify lake types based on their historical time series for variable climate and river inflow. The lake response time to changes in hydrology or climate was evaluated. Both DLW₁ and DLW₂ were sensitive to climate and hydrological changes. The results showed that lake level in high CIR systems depends on climate, whereas in systems with low CIR it depends more on river regime.