Assessing the role of non-native species and artificial water bodies on the trophic and functional niche of Mediterranean freshwater fish communities.

Habitat alterations and the introduction of non-native species have many ecological impacts, including the loss of biodiversity and a deterioration of ecosystem functioning. The effects of these combined stressors on the community trophic web and functional niche are, however, not completely clear. Here, we investigated how artificial ecosystems (i.e. reservoirs) and non-native species may influence the trophic and functional niche space of freshwater fish communities. To do so, we used carbon and nitrogen stable isotope and abundance data to compute a set of isotopic, trait, and functional metrics for 13 fish communities sampled from 12 distinct ecosystems in Türkiye. We show that in reservoirs, fish were more similar in their trophic niche compared to lakes, where the trophic niche was more variable, due to higher habitat complexity. However, there were no differences in the trait and functional metrics between the two ecosystem types, suggesting a higher prey diversity than assumed in reservoirs. We also found that the number of non-native species did not affect the trophic niche space, nor the trait or functional space occupied by the fish community. This indicates that non-native species tended to overlap their trophic niche with native species, while occupying empty functional niches in the recipient community functional space. Similarly, the proportion of non-native species did not affect any trophic, trait, or functional metric, suggesting that changes in community composition were not reflected in changes in the community niche space. Moreover, we found that trait richness, but not functional richness, was positively related to the isotopic niche width and diversity, indicating that a wider occupied trait niche space corresponded with a wider occupied trophic niche and lesser interspecific similarity. Our findings underscore the complexity of ecological relationships within freshwater ecosystems and highlight the need for comprehensive management strategies to mitigate the impacts of human activities and biological invasions.

Biological invasions are a population-level rather than a species-level phenomenon.

Biological invasions pose a rapidly expanding threat to the persistence, functioning and service provisioning of ecosystems globally, and to socio-economic interests. The stages of successful invasions are driven by the same mechanism that underlies adaptive changes across species in general-via natural selection on intraspecific variation in traits that influence survival and reproductive performance (i.e., fitness). Surprisingly, however, the rapid progress in the field of invasion science has resulted in a predominance of species-level approaches (such as deny lists), often irrespective of natural selection theory, local adaptation and other population-level processes that govern successful invasions. To address these issues, we analyse non-native species dynamics at the population level by employing a database of European freshwater macroinvertebrate time series, to investigate spreading speed, abundance dynamics and impact assessments among populations. Our findings reveal substantial variability in spreading speed and abundance trends within and between macroinvertebrate species across biogeographic regions, indicating that levels of invasiveness and impact differ markedly. Discrepancies and inconsistencies among species-level risk screenings and real population-level data were also identified, highlighting the inherent challenges in accurately assessing population-level effects through species-level assessments. In recognition of the importance of population-level assessments, we urge a shift in invasive species management frameworks, which should account for the dynamics of different populations and their environmental context. Adopting an adaptive, region-specific and population-focused approach is imperative, considering the diverse ecological contexts and varying degrees of susceptibility. Such an approach could improve and refine risk assessments while promoting mechanistic understandings of risks and impacts, thereby enabling the development of more effective conservation and management strategies.

Economic costs of non-native species in Türkiye: A first national synthesis.

Biological invasions are increasingly recognised as a major global change that erodes ecosystems, societal well-being, and economies. However, comprehensive analyses of their economic ramifications are missing for most national economies, despite rapidly escalating costs globally. Türkiye is highly vulnerable to biological invasions owing to its extensive transport network and trade connections as well as its unique transcontinental position at the interface of Europe and Asia. This study presents the first analysis of the reported economic costs caused by biological invasions in Türkiye. The InvaCost database which compiles invasive non-native species' monetary costs was used, complemented with cost searches specific to Türkiye, to describe the spatial and taxonomic attributes of costly invasive non-native species, the types of costs, and their temporal trends. The total economic cost attributed to invasive non-native species in Türkiye (from 202 cost reporting documents) amounted to US$ 4.1 billion from 1960 to 2022. However, cost data were only available for 87 out of 872 (10%) non-native species known for Türkiye. Costs were biased towards a few hyper-costly non-native taxa, such as jellyfish, stink bugs, and locusts. Among impacted sectors, agriculture bore the highest total cost, reaching US$ 2.85 billion, followed by the fishery sector with a total cost of US$ 1.20 billion. Management (i.e., control and eradication) costs were, against expectations, substantially higher than reported damage costs (US$ 2.89 billion vs. US$ 28.4 million). Yearly costs incurred by non-native species rose exponentially over time, reaching US$ 504 million per year in 2020-2022 and are predicted to increase further in the next 10 years. A large deficit of cost records compared to other countries was also shown, suggesting a larger monetary underestimate than is typically observed. These findings underscore the need for improved cost recording as well as preventative management strategies to reduce future post-invasion management costs and help inform decisions to manage the economic burdens posed by invasive non-native species. These insights further emphasise the crucial role of standardised data in accurately estimating the costs associated with invasive non-native species for prioritisation and communication purposes.

Predicting the potential implications of perch (Perca fluviatilis) introductions to a biodiversity-rich lake using stable isotope analysis.

Biological invasions, particularly of fish species, significantly threaten aquatic ecosystems. Among these invaders, the introduction of the European perch (Perca fluviatilis) can have particularly detrimental effects on native communities, affecting both ecosystem functioning and human well-being. In this study, carbon and nitrogen stable isotope analysis was employed, using perch originating from five different ecosystems, to model the effects of their hypothetical introduction into Iznik Lake, an economically and ecologically important, biodiversity-rich lake in northern Turkey, to ultimately assess their potential predation impact and competition with native predators. The results revealed that if perch were introduced to the community, they would - considering gape size limitations - primarily prey upon Vimba vimba and Rutilus rutilus, indicating a significant feeding pressure on these species. Furthermore, the study identified a potential overlap and competition for resources between commonly mesopredator perch and the European catfish Silurus glanis, the current top predator in the ecosystem. Both species would occupy top predatory positions, emphasizing the potential disruption of predator-prey dynamics. Our findings underscore the potential ecological repercussions of perch invasions. The selective predation on V. vimba and R. rutilus, with the latter being consumed to a lesser extent by perch, could lead to cascading effects throughout the food web, altering the community structure, and ecosystem dynamics. Additionally, the competition between perch and S. glanis raises concerns about effects on the stability and functioning of the fish community. These results highlight the need for proactive management strategies to mitigate the risk of perch introductions. Strict regulations on the movement and introduction of invasive species, along with comprehensive monitoring, are crucial for preserving native communities and maintaining the ecological integrity of freshwater ecosystems. Our study demonstrates the potential predation impact of perch on vulnerable fish species and the competition with the established apex predator, emphasizing the importance of considering the ecological consequences of perch invasions and informing management decisions to ensure the conservation and sustainability of aquatic ecosystems.

Spatio-temporal Sediment Quality Risk Assessment by Using Ecological and Statistical Indicators: A Review of the Upper Sakarya River, Türkiye.

In this study, heavy metal accumulation levels (Cu, Zn, Cr, Pb, As) in biotic [Carassius gibelio (Bloch, 1782), Squalius pursakensis (Hankó 1925)] and abiotic (sediments) components in a significant freshwater ecosystem in Türkiye were investigated on the basis of seasonal variations using geographic information systems (GIS) and some ecotoxicological risk assessment indices [PLI (pollution load index), PERI (potential ecological risk index), Igeo (geo accumulation index), CF (contamination factor) and BRI (Biological Risk Index)]. GIS-based maps were utilized to depict the distribution of ecotoxicological risk assessment indices to provide a visual explanation by using the Inverse Distance Weighted (IDW) as an estimation method. Samples were collected seasonally from 12 stations selected on the Upper Sakarya River Basin, which is one of the longest fluvial ecosystems in Türkiye. As a result of applied indices, cadmium was found as the most hazardous heavy metal in terms of PERI and CF, nickel was found as the most hazardous heavy metal in terms of BRI and arsenic was found as the most hazardous heavy metal in terms of Igeo. As a result of applied PCI, 2 statistically significant factors explained 81.31% of the total variance. It was also determined that levels of almost all the investigated heavy metals (except Zn) in muscle tissues of fishes were under the permissible limits of Turkish legislation and the FAO.

Heavy metal accumulations in water, sediment, and some cyprinid species in Porsuk Stream (Turkey).

Porsuk Stream is one of Turkey's most important river systems and also one of the most important branches of the Sakarya River. It provides drinking and utility water for two Turkish cities (Kütahya and Eskisehir) with a total population of one million. In this study, water, sediment, and some tissues (liver, gill, and muscle) of five cyprinid fish species were collected seasonally (2010-2011) from eight stations on the Porsuk Stream, and the zinc (Zn), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), and arsenic (As) levels of collected samples were determined. The data observed were evaluated with national and international quality criteria. Based on the data observed, it was determined that the Porsuk Stream is affected by significant inorganic pollution from the Kütahya and Eskisehir Provinces. It was also determined that the Porsuk Dam Lake has an important cleaning capacity and that the water and sediment quality of the Porsuk Stream improves after the output of the dam lake.

Boron concentration in water, sediment and different organisms around large borate deposits of Turkey.

Boron is an essential nutrient for plants and an essential element for many organisms, but can be toxic to aquatic and terrestrial organisms above certain concentrations. The aim of this research was to determine boron concentrations in water, sediment and biotic samples (Gammaridae spp.-Crustacea, Helix sp.-Gastropoda, Donax sp.-Bivalvia, Helobdella sp.-Hirudinae, Ephemeroptera nymph, Chrinomidae larvae, Tipulidae larvae-Insecta, Rana sp.-Amphibia, Natrix sp.-Serpentes, fish sample Leiscus cephalus (Linnaeus, 1758) and leaves of Salix sp.-Salicacea from Seydi Stream (Kirka-Eskisehir). Our results have shown that boron concentrations of the Seydi Stream water is higher than the Turkish Environmental Guidelines standard (>1 mg L(-1)) and in Europe (mean values typically below 0.6 mg L(-1)).

Application of multivariate statistical techniques in the assessment of surface water quality in Uluabat Lake, Turkey.

The application of different multivariate statistical approaches for the interpretation of a complex data matrix obtained during the period 2004-2005 from Uluabat Lake surface water is presented in this study. The dataset consists of the analytical results of a 1 year-survey conducted in 12 sampling stations in the Lake. Twelve parameters (T, pH, DO, PO(-3)(4), NH(4)-N, NO(2)-N, NO(3)-N, SO(3-)(4), BOD, COD, TC, FC) were monitored in the sampling sites on a monthly basis (except December 2004, January and February 2005, a total of 1,296 observations). The dataset was treated using cluster analysis, principle component analysis and factor analysis on principle components. Cluster analysis revealed two different groups of similarities between the sampling sites, reflecting different physicochemical properties and pollution levels in the studied water system. Three latent factors were identified as responsible for the data structure, explaining 77.35% of total variance in the dataset. The first factor called the microbiological factor explained 32.34% of the total variance. The second factor named the organic-nutrient factors explained 25.46% and the third factor called physicochemical factors explained 19.54% of the variances, respectively.