High Ecological Status Research Articles

Decade-long historical shifts in legacy and emerging per- and polyfluoroalkyl substances (PFAS) in surface sediments of China's marginal seas: Ongoing production and ecological risks

Since the addition of perfluorooctane sulfonate (PFOS) to the Stockholm Convention in 2009, it became imperative to reassess the distribution and ecological risk of per- and polyfluoroalkyl substances (PFAS) in coastal sediments over the past decade as sediment records the history of pollutants from human activities. To achieve this, sediments were collected in 2009 and 2021 from China's coastal regions. Despite the consistent geographical pattern where the highest concentrations of ∑PFAS were found in the Yellow Sea, temporal changes have emerged. During the studied period, ∑PFAS levels experienced an increase in the East China Sea while concurrently witnessing a decrease in the South China Sea. Of significance, emerging PFAS compounds displayed not only rising concentrations but also a broader array, pointing towards their intensified production and utilization within China. Alarmingly, PFOS levels in sediments taken from the East China Sea maintained a consistently high ecological risk status over the last ten years. Significant correlations were found between long-chain PFAS and organic carbon content. Comparisons between datasets from 2009 to 2021 uncovered a shifting ecological risk landscape, with heightened concerns for PFOA in the East China Sea, while PFOS-associated risks appeared to diminish in the South China Sea—potentially reflecting the transition to alternative PFAS chemicals. The research reinforces the importance of continuous monitoring and emphasizes the urgent necessity for deeper exploration into the environmental implications and hazards posed by emerging PFAS.

Responses of Epilithic Diatoms to the Construction of Small Hydropower Plant in a Serbian River

Energy of running water accounts for almost 3/4 of the global supply of renewable energy sources and almost 1/5 of total electricity generation. Large and small hydropower plants are associated with a number of environmental problems. The main aim of this study is to investigate the impact of SHP on the diatom community. A total of 149 diatom taxa classified in 47 genera were identified, some of which are considered invasive (Achnanthidium druartii), rare (Gomphonema zellense, Frustulia amphipleuroides) and Navicula radiosafallax is first finding for Serbia. The impact of SHP is evident considering diatoms diversity and relative abundance of dominant species in three seasons (summer, autumn and winter). Values of most measured physico-chemical parameters changed immediately downstream of the SHP. Based on most diatom indices, the water of the Ljuboviđa River had a good ecological status. TID and TDI indicated a predominantly moderate water quality of the Ljuboviđa River. According to Serbian regulations, the Ljuboviđa River had a high ecological status.

Determination of ecological statuses of streams in the Ceyhan River Basin using composition and ecological characteristics of diatoms

The present study aimed to evaluate the interactions between diatoms and ecological factors in various streams and to test the suitability of diatom indices to evaluate the ecological status of 44 streams in the Ceyhan River Basin during the spring and autumn periods of 2021 and the summer of 2022. Canonical correspondence analysis indicated the significant effects of electrical conductivity (EC), dissolved oxygen, biological oxygen demand (BOD5), total phosphorus (TP), and total nitrogen (TN) on the distribution of diatom species of streams in the Ceyhan River Basin. Of the streams, Aksu and Erkenez streams were associated with high EC, BOD5, and TP and characterized by pollution-tolerant species. Pollution-sensitive species showed close integration with Aksu Spring Brook, Gözpınar Creek, Göksun Creek, and Yeşilgöz Spring Brook, which related to a high dissolved oxygen gradient. Different eco-regional diatom indices displayed different scores, representing from bad to high ecological status in the Ceyhan River basin. Among the diatom indices, Trophic Index Turkey (TIT) proved to be the more suitable metric to assess the ecological status of streams. TIT indicated deterioration of water quality in Karasu (S06), Erkenez (S07) streams, and downstream areas of the Ceyhan River and the least distributed sampling stations in the basin. Results suggested that eco-regionally developed diatom indices, like TIT, are required to more accurately assess the ecological status of streams in the Mediterranean region. The study provides a fundamental assessment of the ecological status of streams in the Ceyhan River Basin using an appropriate diatom index before the Pazarcık-centered earthquake on February 6, 2023. Findings allow someone to assess the impact of the earthquake on diatom communities and ecological factors in the region in the future studies.

Potential Ecological Risk Assessment of Soil Heavy Metals in Fengdong New District Based on Information Diffution Model

The large-scale construction of new districts has led to severe soil heavy metal pollution. Therefore, taking Fengdong New District as the target research area, the descriptive statistics of heavy metal content characteristics and Kriging interpolation analysis have been conducted, and the potential ecological risk index and information diffusion theory were further combined to create an information diffusion model based on risk assessment. Finally, the pollution degree, ecological risk, and risk occurrence probability of Pb, Cu, Cd, and Hg were discussed. The findings revealed that the average concentrations of the four heavy metals far exceeded the background value of soil heavy metals by a factor of 1.943 (Pb), 1.419 (Cu), 3.074 (Cd), and 3.567 (Hg), respectively. Moreover, the distribution of soil heavy metals showed strong variability(CV>65%)owing to human interference. The distribution of Pb and Cu pollution were predominantly influenced by industrial production and land development for construction purposes, whereas industrial activities, agricultural practices, and transportation served as the primary sources of Cd contamination. On the other hand, industrial construction emerged as the major factor contributing to Hg pollution. The average values of individual potential ecological risk index for heavy metals of 9.716 (Pb), 7.095 (Cu), 92.292 (Cd), and 142.469 (Hg), coupled with the regional comprehensive potential ecological risk index (RI) average of 251.573, signified that the region was overall characterized by a relatively high potential ecological risk status. The overall potential ecological risk for Pb and Cu in the region were mild, whereas Cd and Hg posed moderate to high risks, indicating that Cd and Hg were the dominant driving factors behind regional heavy metal pollution. The evaluation results of the information diffusion model based on the potential ecological risk indicated that the probability ranking of different levels of comprehensive potential ecological risk was as follows:slightly high (38.98%) > moderate (38.55%) > high (5.89%) > slight (5.15%) > extremely high (3.56%). The exceeding probabilities of potential ecological risk levels for Cd and Hg were significantly higher than those for Pb and Cu. The exceeding probability of different pollution levels of Hg were slight (94.89%), moderate (66.85%), slightly high (23.62%), high (3.9%), and extremely high (2%), of which only the surpassing probability of the slight level was lower than that of Cd. The prediction error of pollution probability of each potential ecological risk level was less than 5%, demonstrating the reliability of the information diffusion model based on the risk assessment. This research will provide technical reference and support for the monitoring and management of potential ecological risks from soil heavy metals in limited sample data regions.

Сommunities of macrozoobenthos on soft sediments in the coastal areas of Peter the Great Bay near Vladivostok (Japan Sea) and their ecological status

At least 16 communities of macrozoobenthos are determined by modern statistical methods on soft sediments in the coastal areas with the depth of ≥ 5 m of Peter the Great Bay at Vladivostok surveyed in 2001–2019. They were: I. Scoletoma spp. + Sigambra bassi; II. Scoletoma spp. + Ophiura sarsii; III. Philine orientalis + Macoma sp.; IV. Aphelochaeta pacifica; V. A. pacifica + Capitella capitata; VI. O. sarsii + Macoma scarlatoi; VII. O. sarsii + Scoletoma spp. + Scoloplos armiger + Ennucula tenuis; VIII. Phoronopsis harmeri; IX. Maldane sarsi; X. A. pacifica + Dipolydora cardalia; XI. Scoletoma spp.; XII. Praxillella gracilis + Pelonaia corrugata, XIII O. sarsii + Acila insignis, XIV Scoletoma spp. + O. sarsii + M. sarsi; XV. Scoletoma spp. + M. scarlatoi, and XVI. A. pacifica. Their differentiation was determined by such environmental imperatives as the level of chemical pollution, eutrophication, and impact of terrigenous water discharge. By biotic indices (AMBI, M-AMBI, TPFbio), the most damaged and environmentally disturbed communities were IV, V, and XVI inhabited the Golden Horn Bay and Diomid Inlet. The communities of the East Bosphorus Strait (III, VI) have higher ecological status that increases even more in the Amur and Ussuri Bays (communities I, II, VII, XII, XIII, XV, XIV), except of the northern tips of both bays (IX, XI) and the eastern part of the Amur Bay (VIII, X). With such bioindicative approach, ecological status of the communities is described more concisely and visually than with indices of species richness, diversity, or W-statistics.

Stressors affecting the ecological status of temporary rivers in the Mediterranean region

Temporary rivers are widespread in the Mediterranean region and impose a challenge for the implementation of the Water Framework Directive (WFD) and other environmental regulations. Surprisingly, an overarching analysis of their ecological status and the stressors affecting them is yet missing. We compiled data on the ecological status of 1504 temporary rivers in seven European Mediterranean region countries and related their ecological status (1) to publicly available data on pressures from the European WISE-WFD dataset, and (2) to seven more specific stressors modelled on a sub-catchment scale. More than 50 % of the temporary water bodies in the Mediterranean countries reached good or even high ecological status. In general, status classes derived from phytobenthos and macrophyte assessment were higher than those derived from the assessment of benthic invertebrates or fish. Of the more generally defined pressures reported to the WISE-WFD database, the most relevant for temporary rivers were ‘diffuse agricultural’ and ‘point urban waste water’. Of the modelled more specific stressors, agricultural land use best explained overall ecological status, followed by total nitrogen load, and urban land use, while toxic substances, total phosphorus load and hydrological stressors were less relevant. However, stressors differed in relevance, with total nitrogen being most important for macrophytes, and agricultural land use for phytobenthos, benthic invertebrates and fish. For macrophytes, ecological quality increased with stressor intensity. The results underline the overarching effect of land use intensity for the ecological status of temporary water bodies. However, assessment results do not sufficiently reflect hydrological stress, most likely as the biological indicators used to evaluate these systems were designed for perennial water bodies and thus mainly target land use and nutrient impacts. We conclude that biomonitoring systems need to be updated or newly developed to better account for the specific situation of temporary water bodies.

Using diatom indices to estimate the ecological status of minimally disturbed rivers of the Sakarya River Basin (Türkiye)

AbstractIn order to determine the ecological status of surface waters of different types in a particular ecoregion, the reference conditions for each type should be identified to compare with observed conditions, as suggested by the Water Framework Directive (WFD). In this study, 36 candidate reference river sites of the Sakarya Basin (Türkiye) were sampled three times in 2018, and the biological assessment of these sites was evaluated using 18 different diatom indices. In addition, nine different environmental variables were also sampled combined with epilithic diatoms. Based on the canonical correspondence analysis (CCA), alkalinity and pH were determined as the most significant environmental variables for diatom assemblages. Among the diatom indices, Biological Diatom Index (IBD), Artois‐Picardie Diatom Index (IDAP), Descy's Index (DES) and Sládeček's Index (SLA) showed significant correlations with alkalinity and pH according to multiple linear regression (MLR) results. IBD index showed the highest response to the pressures and indicated high or good ecological status of the sampling sites. Moreover, rivers with high water quality status have a high correlation with alkalinity, pH and pollution‐sensitive species. On the other hand, good water quality rivers were highly correlated with total phosphorus and intermediate pollution‐sensitive or pollution‐tolerant species. The 13 reference sites established in this study can be used to assess the ecological status by comparison with the same types of river bodies for further studies in the basins of Türkiye.

Macrophyte-Based Assessment of Upland Rivers: Bioindicators and Biomonitors

For the first time, a macrophyte-based assessment of ecological status was related to the accumulated heavy metals and trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn) in aquatic plants. Three moss and two vascular plant species were applied as biomonitors: Fontinalis antipyretica Hedw., Leptodictyum riparium (Hedw.) Warnst., Platyhypnidium riparioides (Hedw.) Dixon, invasive Elodea canadensis Michx., and Myriophyllum spicatum L. Three streams were assessed as good at a high ecological status which correlated with low contamination based on calculated contamination factors (CFs) and metal pollution index (MPI). Two sites evaluated in moderate ecological status were revealed to be in heavy trace element contamination. The most significant was the accumulation of moss samples from the Chepelarska River under mining impact. Mercury exceeded the environmental quality standard (EQS) for biota in three of the studied upland river sites.

Spatiotemporal change and driving factors of ecological status in Inner Mongolia based on the modified remote sensing ecological index.

Remote sensingmonitoring of regional ecological quality has advanced significantly with the rapid developments of remote sensing technology. At present, remote sensing ecological index (RSEI) has been widely used in ecological status monitoring. However, RSEI was proposed for urban environments, and the rationality and accuracy of its applicability to desert-dominated arid region ecosystems need to be demonstrated. Therefore, in this study, we incorporated desertification monitoring index (DMI) and salinity monitoring index (SMI) to RSEI and developed the modified remote sensing ecological index (MRSEI) for arid regions. Moreover, we analyzed the stability of MRSEI in ecological status monitoring for arid regions. The MRSEI was then used to evaluate the ecological quality of Inner Mongolia from 2000 to 2020 and exploring its causes. The results show that (1) Although the evaluation results of RSEI and MRSEI are more consistent in areas with high ecological status grades, the MRSEI results are more cautious and reliable in extreme conditions (e.g., desertification, salinization) than the RSEI. (2) Approximately 87.66% of ecological quality have improved or remain stable from 2000 to 2020, but the remaining areas (accounting for 12.34% of the whole area) are still under degraded conditions. This demonstrates that although local governments have made some progress in ecological conservation, the areas that are fluctuating or degraded still require protection or management. (3) In Inner Mongolia, the ecological quality which drove by precipitation (P) & temperature (T) accounting for 26.67% of the study area, population density (D) and GDP per capita (G) affected 13.23% of regional ecological quality. Overall, this research is crucial for evaluating spatial and temporal changes in arid region ecology and establishing conservation strategies.

Assessment of Zooplankton and Physico-chemical Parameters of Upper River Benue, Adamawa State, Nigeria

Between January and June, 2022 some physico-chemical and biological conditions of Upper River Benue were assessed at five selected sites on monthly basis between 6:00 – 10:00a.m. A total of 9.849 ×104 organisms/L was recorded for zooplankton abundance. Rotifera was observed to have a total abundance of 39.9%, followed by Cladocera contributed a total of 33.45%, while the least was Decapoda gave 1.37%. The higher number of taxa (25) was recorded at site V. The abundance of individuals was highest at site IV. Twenty-seven species (27) species of zooplankton were identified during the study period ranging from elven Rotifera, nine Cladocera, five Copepoda, one Ostracoda and one Decapoda. The order of dominance of the zooplankton of Upper River Benue is Rotifera>Cladocera>Copepoda>Ostracoda>Decapoda with Brachionus caudate, Bosmina longirostis and daphnia being the most dominant (6.94%) of the total zooplankton of Upper River Benue. The physico-chemical parameters results revealed that temperature, pH, electrical conductivity, transparency, dissolved oxygen, free CO2, alkalinity were within recommended acceptable limit except ammonia, phosphorus and nitrogen were higher than recommended acceptable limit. However, no significant difference was found between the seasons in terms physico-chemical paraneters and zooplankton distribution (P>0.05). The study showed the reservoir to be eutrophic with moderate water quality, high ecological and pass chemical status, with diverse assemblages of zooplankton. It was recommended that there should be continuous monitoring of the biological and physico-chemical status of the river to ascertain the long-term impact of anthropogenic inputs to take remedial measures so as to ensure the health of aquatic life.

Land use and environmental quality in Ireland over two decades of contrasting agricultural trends

Global awareness and scrutiny of food production systems, including competition for land between agriculture and nature-based solutions to climate change, has increased immensely recently. In Ireland, around 70% of land area is used for agriculture, mostly pasture-based livestock production. Cattle numbers began to decline in the late 1990s, as milk productivity per cow increased along with the European Union policy of intensification implemented in 1998. Phasing out of the EU milk quota system from 2011 onwards initiated an increase in dairy cow numbers, which rose by 46% by 2020. This development has reversed environmental progress. This study outlines the impact of contrasting policies that have contributed to abatement and intensification of greenhouse gas and ammonia emissions from Ireland’s agriculture, forestry and other land use (AFOLU) sector, along with impacts on water quality effects. Ireland achieved most environmental targets during the 2000s. However, between 2010 and 2019, agricultural greenhouse gas emissions increased by 12% and annual ammonia emission ceilings exceeded the national limit in seven of those years. Around 6% of rivers lost their good or high ecological water quality status. These developments jeopardise compliance with contemporary environmental targets, such as achieving a 25% reduction in greenhouse gas emissions from agriculture by 2030, and AFOLU climate neutrality by 2050. Achieving environmental quality targets will necessitate far-reaching and immediate development of policy for the land use sector beyond the implementation of currently proposed mitigation measures.

Eco-assessment of streams of Konya closed river basin (Turkey) using various ecoregional diatom indices.

Ecological assessment of freshwater ecosystems based on diatom metrics is an important issue for attaining environmental sustainability. The present study aimed to evaluate differences in the diatom-stressor relationship in relatively least disturbed streams in the Konya closed river basin using multivariate analyses and to bio-assess streams by the application of different ecoregional diatom indices. Cocconeis euglypta, Cymbella excisa, Cocconeis placentula, and Achnanthidium minutissimum are the most contributing species to the dissimilarity of sampling stations between rainy (spring) and dry (summer and fall) seasons and also between altitude (A2 800- < 1600m and A3 ≥ 1600m) groups. The first two axes of canonical correspondence analysis revealed a significant (82.8%) relationship between diatom species and stressors. Diatom species displayed distinct responses to environmental variables (electrical conductivity, Ni, Cu, B, and altitude) playing important roles on the distribution of species. Diatom indices indicate different ecological statuses of stations, from bad to high. European diatom indices except Duero Diatom Index (DDI) and Trophic Diatom Index (TDI) showed good responses to the eco-assessment of streams and indicated high ecological status for the least disturbed sampling stations symbolized as S16, S20, S24, S25, S27-29, S37, and S39. These results were also supported by abiotic evaluation. Although TIT was more competitive in the bio-assessment of streams among diatom indices, it is necessary to increase its species list by determining their trophic weights in future studies. Therefore, the use of ecoregion-specific diatom indices is suggested along with increasing the number of used species to correctly interpret the water quality.

Phosphorus reference conditions in lowland streams: Survey in old forests and anaerobic sediment release

The reference (pristine) concentrations of total dissolved phosphorus (TDP) in surface waters are difficult to define in lowland regions because of their high population density. Here, we estimated reference conditions of TDP from headwaters and their riverbed sediments (n = 140) in old forests. Surface waters and sediments were collected in the lowland region of Belgium as transects starting in 20 different old forests (before 1775; pristine) to up to 1.5 km outside the forest edge (disturbed). Sediment P concentrations in disturbed samples readily increased with increasing distance from the borders of old forests. The P mobilized from the sediments to the overlying water was also measured in laboratory incubations to mimic P release during seasonal redox cycles. The sediment respiration was larger in disturbed than in the reference sediments. Disturbed sediments released more P during anaerobic than aerobic incubations, while reference sediments did not show such a difference. The mean TDP in the reference surface water samples is 57 μg TDP L−1 [95 % confidence interval 41; 72], very close to the pre-industrial background previously estimated for the Scheldt river. The 90th percentile of the reference water is 137 [110; 180] μg TDP L−1. That P90 is just under the prevailing TP limit of 140 μg P L−1, illustrating that this limit is very close to the upper baseline of reference conditions. The P75, often proposed as the threshold for high ecological status, was 84 [55; 122] μg P L−1. This study showed that soil or sediments in old forests might serve to identify reference conditions. The well-established summer peaks of TDP in lowland rivers are unlikely to occur in pristine areas.

Microplastic Contamination and Ecological Status of Freshwater Ecosystems: A Case Study in Two Northern Portuguese Rivers

Most European rivers have not yet achieved "good" ecological status. In addition, the presence and abundance of microplastics (MPs) in freshwater is a matter of great concern to the scientific community. This study assesses the ecological status of four sampling sites of Selho (S1-S4) and Costa-Couros (C1-C4) rivers (Guimarães, Portugal), and the abundance of MPs in sediments and benthic macroinvertebrates (Oligochaeta) from those sites. All sites of both rivers under higher pressure did not reach a "good" ecological status (S2-S3, C2-C4) based on the macroinvertebrate community. High levels of nutrients were observed at all sites in both rivers (except C2), especially phosphorus. In the Oligochaeta's gut of Costa-Couros river, the high number of MPs seems to be associated with their weight (95.25 ± 25.61 to 1069.00 ± 385.30 MPs g/fresh weight), suggesting the existence of malnutrition and digestive disorders, whereas the highest number of MPs in gut (134.00 ± 30.36 to 558.6 ± 100.70 MPs g/fresh weight) were found for the heaviest organisms of Selho. Thus, sites with higher ecological status do not necessarily have lower abundance of MPs. In the sediments, urbanization seems to be the main driver for MP contamination. MP contamination is pervasive across the sediments and Oligochaeta's gut in both rivers. Since MPs have the potential to cause harm to environmental and human health, it is essential to monitor not only the ecological status of freshwaters, but also emerging pollutants such as MPs.

Assessing pressure drivers on the benthic ecosystem in the coastal zone of Western Messinia, Greece

The Messinia region, located in the South – West of the Peloponnese, Greece, is an ecologically valuable area comprising of several important coastal habitats (including coastal lagoons, seagrass meadows, and Mediterranean rhodolith beds) eliciting its inclusion in the Natura 2000 network. Land-based anthropogenic pressures are likely to influence the ecological status of this coastal zone. Here we identify those regional pressures and use physico-chemical elements of the ecosystem, and the status of the macrofauna communities to assess the level of environmental degradation in the coastal and lagoon water bodies. High organic load from the catchment area, geomorphological and hydrological features of the water bodies are the major drivers affecting the ecological quality of the region. The lagoon is severely degraded due to both a high nutrient input from the surrounding river basin (likely due to agricultural run-off), and a relatively low level of connectivity with the marine environment (due to alterations in the regional hydrology). In contrast, the coastal zone is classified as being at a high or good ecological status and seems scarcely impacted by anthropogenic pressures. The macrobenthic communities reflect how vulnerable the lagoon is to multiple stressors (and in particular agricultural practices), and highlight the necessity of defining and implementing holistic, river-basin based management plans for the Gialova lagoon, and the surrounding coastal area of Messinia.

Alien species and the Water Framework Directive: Recommendations for assessing ecological status in fresh waters in Norway

Abstract Invasive alien species are recognized as a significant anthropogenic threat to freshwater ecosystems, because they may bring about the local extinction of native species and the collapse of habitat types of special conservation concern. The Water Framework Directive (WFD) is an important legislative tool for the protection of water bodies in the European Union. It requires the assessment of the ecological status of water bodies and the enforcement of measures for water bodies that fail to achieve at least ‘good’ ecological status. However, the WFD does not explicitly mention alien species. This article presents a three‐tiered approach for the incorporation of data on alien species into WFD assessments of freshwater bodies in Norway. If relevant data on WFD parameters are available for the water body under consideration, its ecological status should be inferred from those data. Otherwise, ecological status should be assessed using evidence of the effects that the alien species have on biological quality elements in comparable water bodies. If neither of these options is feasible, the ecological status should be classified according to the ecological effect score of the alien species present, as obtained from the Generic Ecological Impact Assessment of Alien Species (GEIAA). It is further recommended that a water body cannot be assigned ‘high ecological status’ if at least one alien species is present. If more than one alien species is present, the status is determined by the species with the highest impact. Ecological, geographical, historical, and taxonomic delimitation criteria for this assessment method are presented, together with a list of the alien species that at present fulfil these delimitations in Norway. The management implications of the recommendations are that more Norwegian freshwater bodies are likely to require measures, and that further data must be collected. Most of the recommendations are transferable to other countries, although they may require adjustment.

Estimating nutrient thresholds for eutrophication management: Novel insights from understudied lake types

Nutrient targets based on pressure-response models are essential for defining ambitions and managing eutrophication. However, the scale of biogeographical variation in these pressure-response relationships is poorly understood, which may hinder eutrophication management in regions where lake ecology is less intensively studied. In this study, we derive ecology-based nutrient targets for five major ecoregions of Europe: Northern, Central-Baltic, Alpine, Mediterranean and Eastern Continental. As a first step, we developed regressions between nutrient concentrations and ecological quality ratios (EQR) based on phytoplankton and macrophyte communities. Significant relationships were established for 13 major lake types; in most cases, these relationships were stronger for phosphorus than for nitrogen, and stronger for phytoplankton than for macrophytes. Using these regressions, we estimated the total phosphorus (TP) and total nitrogen (TN) concentrations at which lakes of different types are likely to achieve good ecological status. However, in the very shallow lakes of the Eastern Continental region, relations between nutrient and biological communities were weak or non-significant. This can be attributed to high nutrient concentrations (in the asymptotic zone of phosphorus-phytoplankton models) suggesting other factors (light, grazing) limit primary production. However, we also show that fish stocking is a major pressure on Eastern Continental lakes, negatively affecting ecological status: lakes with low fish stocking show low chlorophyll-a concentrations and good ecological status despite high nutrient levels, while the lakes with high fish stocking show high chlorophyll-a and low ecological status. This study highlights the need to better understand lakes in biogeographic regions that have been, for historical reasons, less studied. This, in turn, helps reveal factors that challenge the dominant paradigms of lake assessment and management.

Variability of diatom community composition and structure in mountain streams

Small rivers support high levels of biodiversity, being especially sensitive to the effects of global change. Temporal records of community composition in minimally impaired streams can be used to explore trends in biodiversity in response to climate change and natural temporal variation. We approached the comparison of two time periods (2003–2008 and 2016–2020) to study whether the composition of diatom assemblages changed over time in twenty-three streams of the mountain range of Picos de Europa (Northern Spain). The stream’s water chemistry indicated significant decreases in N_NO3− and P_PO43− content over time. In these minimally disturbed streams, the specific diatom community was dominated by Achnanthidium pyrenaicum, Achnanthidium minutissimum and Cocconeis euglypta. PERMANOVA analyses did not identify significant changes in diatom assemblage composition between periods or river types. Diatom indices (e.g. IPS, NORTIdiat) indicated high or good ecological status and relatively high alpha diversity values were found in these mountain rivers during the studied years. Although diversity and evenness showed a significant decrease over time, the temporal stability of the river-type diatom reference community between the two periods should be considered as an indicator of biodiversity persistence of high importance when monitoring the ecological status following the reference condition approach.

Trends and influential factors of high ecological status mobility in Irish Rivers

The decline in high ecological water status in rivers is a significant concern in European countries. It is thus important to investigate the factors that cause sites to lose high status in order to undertake measures to protect and restore high status water quality. Analysis of 20 years of water quality data reveals strong mobility between high status and non-high status (especially good status) rivers. Associations between this mobility and socio-economic and physical environmental variables were estimated by multinomial logistic regression at national scale and regional scale. Based on reported changes in water quality status cross across 1990, 2000 and 2010, four classes of the mobility of high status were defined in this study: those sites that maintain high status (maintain), enter high status (enter), fluctuate between high and non-high status (fluctuate) and exit from high status (exit). The national results indicate that agricultural activity as indicated by variables representing intensity of livestock farming (organic nitrogen) and tillage farming (cereal share) and elevation had significant negative impacts on high status rivers. Meanwhile, significant differences in population density and septic tank density between ‘exit’, ‘maintain’, ‘fluctuate’ and ‘enter’ classes indicate that these factors played important roles in the stability of high status rivers. The regional outcomes reveal differential significant pressures across regions. For example, rainfall and elevation had positive impacts on high status rivers in the north-west region, while organic nitrogen had a negative effect in the south-west. This paper demonstrates the challenge in achieving the Water Framework Directive goal of maintaining high status rivers, given the sensitive and highly differentiated nature of areas that have lost high status or fluctuated in and out of high status. This paper also suggests the necessity for localised policies and mitigation measures.

Biodiversity and seasonal distribution of benthic diatom assemblages as an indicator of water quality of small karstic river in Bosnia and Herzegovina

The aims of this paper were to describe seasonal changes in the qualitative and quantitative composition of diatom taxa and the potential application of benthic diatoms for ecological status evaluation. Diatom indices (IPS and TI) were calculated from data from three different locations along a longitudinal profile of the Bunica, a small karstic river in Bosnia and Herzegovina. A total of 147 taxa were recorded in 12 samples. The most common taxa were Meridion circulare (Greville) C.Agardh and Ulnaria ulna (Nitzsch) Compère. Physical and chemical analyses showed low concentrations of nutrients, good oxygenation, typical pH for carbonate bed/origin and generally oligotrophic conditions and high ecological status. All sites had similar physico-chemical conditions and there were only few seasonal differences. Ordination of the diatom data showed that samples showed neither longitudinal nor seasonal patterns. Median value for IPS (16.8) and for TI (7.3) can be possible ‘‘expected’’ values for ecological status assessment for small karstic rivers in the Mediterranean region. We propose the use of the phytobenthos Intercalibration Common Metric (pICM - an index that combines the IPS and TI) as a national metric for countries developing WFD diatom methods at a late stage. One situation is described, and a solution, which is potentially transferable to other locations in Bosnia and Herzegovina and also to other countries facing similar challenges.