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Pro-ecological and conservation activities are not always beneficial to nature: a case study of two lowland streams in Central Europe
AbstractSince 1990 and in particular, after the implementation of the Water Frame Directive, many positive effects of pro-ecological projects are evident; unfortunately, examples of adverse effects have also been observed. This study aims to indicate how some ill-considered actions, called “pro-ecological”, may lead to habitat degradation and the disappearance of valuable hydrobiont species. Two watercourses, representing the lowland gravel stream and sandy stream type, were selected for the study. Literature indicated that in the past, these watercourses were characterized by an excellent ecological status and the presence of valuable rheophilic fauna and flora. Environmental parameters were recorded, macroinvertebrates and ichthyofauna were sampled and analyzed, and finally, indexes were calculated. The results were compared with literature data. In the course of studies conducted in 2011–2015, drastic habitat deterioration and extensive changes in the species structure of ichthyofauna and aquatic invertebrates were observed. Changes in the Smolnica stream have been caused by the three retention basins constructed in 2000, along the lower and middle course; while in Kiszewko, however, the factor for habitat deterioration was connected with the excessive expansion of the Eurasian beaver (Castor fiber), which created a beaver pond 20 m in width, with impoundment elevations of up to 2 m.
Selected Quality Attributes of Freshwater Mussel Powder as a Promising Ingredient for Pet Food
The aim of this study was to describe the quality attributes of a freeze-dried preparation obtained from freshwater mussel Sinanodonta woodiana (SW) soft tissue in respect to its potential as a novel pet food ingredient. After ecotoxicological testing of the raw material with MARA (Microbial Assay for Risk Assessment), the basic physico-chemical properties of the powder, such as approximate composition, bulk density, color parameters, water activity, electrophoretic analysis (SDS-PAGE), solubility, gelling and emulsifying capacity, were analyzed. The powder with a water activity of 0.43 offers a toxically safe preparation that contains over 34% protein/100 g of dry matter (DM). The SDS-PAGE profile showed twelve protein bands with a molecular weight (MW) ranging from >250 to 10 kDa. Taurine content has been estimated at an essential amount above 150 mg/100 g of DM. The powder possessed desirable emulsifying properties with 230 mL per 1 g and demonstrated the ability to form a firmer gel with a strength of 152.9 g at a temperature above 80 °C with at least 10% protein content. The L*, a*, and b* values characterizing powder color were found to be 69.49, 16.33, and 3.86, respectively. The SW mussel powder seems to be a promising ingredient that can be added with other binding or gelling agents in order to improve both the taste and acceptance of the final pet food products.
Lower parasite pressure in invasive freshwater bivalves than in sympatric native Unionidae mussels in southern European lakes
AbstractThe Enemy Release Hypothesis (ERH) proposes that the success of bioinvasions is attributable to lower enemy pressure on invasive species compared to native ones, giving a competitive advantage for invaders. In line with the hypothesis, we previously observed in northern European bodies of fresh water that invasive bivalves were subject to lower parasite pressure than sympatric native mussels. Here, we investigated ERH in three southern European lakes, where the native mussels are rapidly declining and being replaced by non-native bivalves. In total, 679 bivalves (n of individuals per species per lake varying from 12 to 187) were collected during 2016–2018. Ten parasite taxa were found. The mean lake-specific number of parasite taxa in the native mussels (Anodonta exulcerata, A. cygnea, A. anatina and Unio elongatulus) was 2.6 times that in the invasive bivalves (Dreissena polymorpha, Corbicula fluminea and Sinanodonta woodiana). Similarly, the mean lake-specific sum of prevalences of infection by different parasite taxa in the native mussels was 3.4 times that in the invasive bivalves. Notable was the complete lack of parasites in C. fluminea. Thus, the results supported the Enemy Release Hypothesis and were in accordance with previous results from northern Europe, suggesting, on average, a lower parasite pressure in invasive bivalves than in sympatric native mussels. As parasites are usually harmful, this may contribute to the observed successful invasion of non-native freshwater bivalves in Europe.
Enemy release: loss of parasites in invasive freshwater bivalves Sinanodonta woodiana and Corbicula fluminea
Invasive freshwater bivalves harm native species, ecosystems and biodiversity, and incur economic costs. The enemy release hypothesis posits that invasive species are released from enemies during the invasion process, giving them a competitive advantage in the new environment. We compared parasitism in two invasive freshwater bivalves, Sinanodonta woodiana and Corbicula fluminea between their original range (China) and invaded range (Europe). For S. woodiana , the average sample‐size‐standardized population‐specific parasite taxon richness was 2.1 times as high, and sum of prevalence was 3.0 times as high in the native range (3 populations, 81 individuals studied) as in the invaded range (6 populations, 210 individuals studied). For C. fluminea , the average standardized population‐specific parasite taxon richness was 1.3 and sum of prevalences was 27.5 in the native range (4 populations, 749 individuals studied), whereas all European C. fluminea were free of parasites (7 populations, 418 individuals studied). The results demonstrate loss of parasites as a result of invasion. Previous studies have shown that parasite pressure on S. woodiana and C. fluminea in the invaded range in Europe is, on average, lower than on sympatric native freshwater mussel populations. Together, these results support one aspect of the enemy release hypothesis: invasive bivalves experience reduced parasite loads as a result of invasion, which may contribute to their success, given the costs typically imposed by parasitism.