Trophic interactions between native and alien palaemonid prawns and an alien gammarid in a brackish water ecosystem

Macroalgae are an important habitat for small mobile invertebrates such as gammarid amphipods and palaemonid prawns. Gammarid amphipods are important grazers of micro- and macroalgae whereas palaemonid prawns are feeding on macroalgae and small aquatic invertebrates including gammarids. Recently the invasive palaemonid prawn Palaemon elegans established in the Baltic Sea. As P. elegans occurs within the same habitats as the native Palaemon adspersus, it is expected that this invasion modifies the existing trophic interactions. To address this question, we experimentally investigated the feeding of the native P. adspersus and the invasive P. elegans on the benthic macroalga Cladophora glomerata and on the invasive gammarid amphipod Gammarus tigrinus. In the course of the experiment neither G. tigrinus nor Palaemon spp. had effects on filamentous macroalgae. The presence of prawns drastically increased the mortality of amphipods with no difference in the feeding efficiency between the two prawn species. To conclude, the alien prawn does not add an extra function to the trophic system of the coastal ecosystem of the Baltic Sea. Nevertheless, due to its progressively increasing densities and wide habitat range, P. elegans is expected to exert stronger predation pressure on gammarid amphipods as compared to P. adspersus alone

Türkçe Kitabımız: Batı Trakya’nın Edebiyatı, Gazete ve Dergi Metinleri

Το βιβλίο έγινε με γνώμονα τις εκπαιδευτικές ανάγκες των παιδιών της μειονότητας της Θράκης, που έχουν μητρική γλώσσα την τουρκική. Δημιουργήθηκε για να χρησιμοποιείται παράλληλα με τα σχολικά βιβλία διδασκαλίας της τουρκικής γλώσσας που υπάρχουν ήδη, ως βοηθητικό και συμπληρωματικό. Η καινοτομία που το κάνει υποδειγματικό είναι ότι στηρίζεται στη δημιουργική συμβολή της μειονότητας και δίνει τη σημασία που πρέπει στον πολιτιστικό της πλούτο. Οι ιδιαιτερότητες του βιβλίου: 1) Είναι η πρώτη φορά που μειονοτικοί Θρακιώτες, με τη συμβολή δύο ελλήνων μειονοτικών της Κωνσταντινούπολης, συνέταξαν ένα σχολικό βιβλίο δικό τους, δείγμα σεβασμού στη μειονότητα. 2) Όλα τα κείμενα που περιέχει το βιβλίο έχουν γραφτεί στα τουρκικά από μέλη της μειονότητας. Το βιβλίο φιλοξενεί σαράντα οκτώ μειονοτικούς συγγραφείς, ποιητές και διανοουμένους. 3) Το βιβλίο περιέχει πολλών ειδών κείμενα που έχουν αντληθεί από σχεδόν όλα τα τουρκόφωνα έντυπα (εφημερίδες και περιοδικά) που εκδίδονται στη Θράκη. 4) Το κάθε μάθημα συνοδεύουν φωτογραφίες που απεικονίζουν τον πολιτισμό και την ιστορική κληρονομιά της μειονότητας. Ένας μεντρεσές, ένα τζαμί, ένα σχολείο παρέχουν στους μικρούς αναγνώστες υλικό για να αναπτύξουν με το περιβάλλον τους σχέσεις που ανοίγουν πόρτες σε ένα καλύτερο μέλλον. 5) Οι συγγραφείς είναι μειονοτικοί. Τα κείμενα πηγάζουν από την πραγματικότητα της μειονότητας, αναφέρονται στην καθημερινότητα, στις παραδόσεις και στα προβλήματά της, και αποπνέουν κατανόηση της καθημερινότητας, αγάπη των παραδόσεων και ενσυναίσθηση των προβλημάτων. Τα περιεχόμενα (τίτλοι μαθημάτων) είναι: 1- Ξεκινά το σχολείο και ένας νέος χρόνος 2- Η αγάπη για τη μητέρα 3- Η αγάπη για το δάσκαλο 4- Η αγάπη για τον τόπο μας – Η νοσταλγία 5- Η αγάπη για τον τόπο μας – Η αγάπη για το συνάνθρωπο 6- Προβλήματα – Η παιδεία 7- Η καπνοπαραγωγή 8- Τα απόμακρα προβλήματα – ή τα δεινά των άλλων 9- Οι παραδόσεις μας 10- Οι γειτονιές μας, τα έθιμά μας 11- Η αγάπη για τον Γιουνούς και το ποίημα 12- Το περιβάλλον μας που αλλάζει 13- Η ιστορία, ή «Κάποτε ήταν αλλιώς» 14- Η γλώσσα μας 15- Κοινωνικά θέματα – Η μέρα της γυναίκας και του παιδιού 16- Η καθημερινότητά μας – Οι ευχάριστες αναμνήσεις 17- Η καθημερινότητά μας – Οι δυσάρεστες αναμνήσεις 18- Η καθημερινότητά μας – Σκηνές από τα σχολεία μας 19- Πρέπει να είμαστε δίγλωσσοι και Οι μεταφράσεις 20- Τι γίνεται στον κόσμο 21- Τι κάνουμε στον ελεύθερο χρόνο μας – Τα «hobby» μας 22- Δεν υπάρχει τίποτα σαν την υγεία! 23- Ο εσωτερικός μας κόσμος 24- Η ζωή σας περιμένε

The invasive amphipod Gammarus tigrinus Sexton, 1939 displaces native gammarid amphipods from sheltered macrophyte habitats of the Gulf of Riga

The North-American amphipod Gammarus tigrinus Sexton, 1939 is a successful invader in European waters due to its high reproductive potential and tolerance to severe environmental conditions and various pollutants. In this study, we followed the invasion and establishment of this exotic species in a species-poor ecosystem of the northern Baltic Sea. Two years after the establishment of G. tigrinus, over half of the sampling sites were occupied exclusively by G. tigrinus, whereas G. tigrinus coexisted with native gammarids in only one tenth of all sites. There was a clear separation of habitat occupancy between native species and G. tigrinus in terms of abiotic environment and macrophytic habitat. G. tigrinus preferred shallow sheltered areas dominated by vascular plants, while native species mainly occurred in more exposed, deeper habitats with phaeophytes and rhodophytes. In its suboptimal habitats, G. tigrinus exhibited moderate abundances, which allowed for the coexistence of native gammarids and the invasive gammarid. Since its establishment, the abundance of G. tigrinus has showed no signs of decline, with abundances exceeding almost fifteen times those of native gammarids at some locations. The results suggest that, irrespective to the competitive superiority of G. tigrinus over the native gammarids, the invasive G. tigrinus does not monopolize the entire coastal area of the northern Baltic Sea but mostly outcompetes native species in its favoured habitats.

Molecular genetic differentiation of native populations of Mediterranean blue mussels, Mytilus galloprovincialis Lamarck, 1819, and the relationship with environmental variables

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Cleaning up seas using blue growth initiatives : Mussel farming for eutrophication control in the Baltic Sea

Eutrophication is a serious threat to aquatic ecosystems globally with pronounced negative effects in the Baltic and other semi-enclosed estuaries and regional seas, where algal growth associated with excess nutrients causes widespread oxygen free “dead zones” and other threats to sustainability. Decades of policy initiatives to reduce external (land-based and atmospheric) nutrient loads have so far failed to control Baltic Sea eutrophication, which is compounded by significant internal release of legacy phosphorus (P) and biological nitrogen (N) fixation. Farming and harvesting of the native mussel species (Mytilus edulis/trossulus) is a promising internal measure for eutrophication control in the brackish Baltic Sea. Mussels from the more saline outer Baltic had higher N and P content than those from either the inner or central Baltic. Despite their relatively low nutrient content, harvesting farmed mussels from the central Baltic can be a cost-effective complement to land-based measures needed to reach eutrophication status targets and is an important contributor to circularity. Cost effectiveness of nutrient removal is more dependent on farm type than mussel nutrient content, suggesting the need for additional development of farm technology. Furthermore, current regulations are not sufficiently conducive to implementation of internal measures, and may constitute a bottleneck for reaching eutrophication status targets in the Baltic Sea and elsewhere. Highlights • Mussel farming is a viable internal measure to address Baltic Sea eutrophication. • Rates of nutrient removal depend on salinity at the regional scale and food availability at the local scale. • Cost effectiveness of nutrient removal by mussel farming depends also on farm type. • Total farm area needed for achieving HELCOM nutrient reduction targets is realistic

Diversity and distribution of genetic variation in gammarids: Comparing patterns between invasive and non-invasive species

© 2017 Published by John Wiley & Sons Ltd. Biological invasions are worldwide phenomena that have reached alarming levels among aquatic species. There are key challenges to understand the factors behind invasion propensity of non-native populations in invasion biology. Interestingly, interpretations cannot be expanded to higher taxonomic levels due to the fact that in the same genus, there are species that are notorious invaders and those that never spread outside their native range. Such variation in invasion propensity offers the possibility to explore, at fine-scale taxonomic level, the existence of specific characteristics that might predict the variability in invasion success. In this work, we explored this possibility from a molecular perspective. The objective was to provide a better understanding of the genetic diversity distribution in the native range of species that exhibit contrasting invasive propensities. For this purpose, we used a total of 784 sequences of the cytochrome c oxidase subunit I of mitochondrial DNA (mtDNA-COI) collected from seven Gammaroidea, a superfamily of Amphipoda that includes species that are both successful invaders (Gammarus tigrinus, Pontogammarus maeoticus, and Obesogammarus crassus) and strictly restricted to their native regions (Gammarus locusta, Gammarus salinus, Gammarus zaddachi, and Gammarus oceanicus). Despite that genetic diversity did not differ between invasive and non-invasive species, we observed that populations of non-invasive species showed a higher degree of genetic differentiation. Furthermore, we found that both geographic and evolutionary distances might explain genetic differentiation in both non-native and native ranges. This suggests that the lack of population genetic structure may facilitate the distribution of mutations that despite arising in the native range may be beneficial in invasive ranges. The fact that evolutionary distances explained genetic differentiation more often than geographic distances points toward that deep lineage divergence holds an important role in the distribution of neutral genetic diversity