Experimental and field studies were carried out to characterise biodeposit dynamics in a suspended mussel Mytilus edulis L. farm in Great-Entry Lagoon, eastern Canada. We assessed: (1) the quantity and quality of biodeposits produced by different age classes of mussels, (2) the sizedependent sinking velocity of faeces and (3) the variation in sedimentation rates at different spatial and temporal scales. Individual 0+ mussels produced on average only 63% of the mass of biodeposits (32.4 mg dry wt d -1 ind.-1) that 1+ mussels did (51.5 mg dry wt d -1 ind.-1 ). In contrast, the amount of biodeposits produced per unit body weight (dry weight of soft tissue) was greater for 0+ than for 1+ mussels. Faecal pellet sinking velocity ranged from 0.27 to 1.81 cm s -1 for mussels ranging in size from 3 to 7 cm, and was best correlated with faecal pellet width. Sedimentation rates were greater within the farm than at reference sites, supporting the hypothesis that mussel farming increases sedimentation rates. Variations in sedimentation were also observed at small spatial scales and through time. Prior to the harvesting of 1+ mussels, sedimentation rates directly under the 1+ mussel lines were about twice those 10 m distant, between the lines, and in other zones (reference sites and sites in the lease with 0+ mussels). These observations and sedimentation patterns along transects leading away from the mussel farm suggest that biodeposits from the farm are not dispersed broadly. The estimated initial dispersal of faecal pellets ranges from 0-7.4 m (1+ mussels) to 7-24.4 m (0+ mussels).

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Increasing empirical evidence indicates the number of released individuals (i.e. propagule pressure) and number of released species (i.e. colonization pressure) are key determinants of the number of species that successfully invade new habitats. In view of these relationships, and the possibility that ships transport whole communities of organisms, we collected 333 ballast water and sediment samples to investigate the relationship between propagule and colonization pressure for a variety of diverse taxonomic groups (diatoms, dinoflagellates and invertebrates). We also reviewed the scientific literature to compare the number of species transported by ships to those reported in nature. Here, we show that even though ships transport nearly entire local communities, a strong relationship between propagule and colonization pressure exists only for dinoflagellates. Our study provides evidence that colonization pressure of invertebrates and diatoms may fluctuate widely irrespective of propagule pressure. We suggest that the lack of correspondence is explained by reduced uptake of invertebrates into the transport vector and the sensitivity of invertebrates and diatoms to selective pressures during transportation. Selection during transportation is initially evident through decreases in propagule pressure, followed by decreased colonization pressure in the most sensitive taxa.

Iron manganese steels with Mn mass contents of 15 to 30 % exhibit microstructural related superior ductility and extraordinary strengthening behaviour during plastic deformation, which strongly depends on the Mn content. This influences the austenite stability and stacking fault energy γfcc and shows a great impact on the microstructure to be developed under certain stress state or during severe plastic deformation. At medium Mn mass contents (15 to 20 %) the martensitic γ‐ε‐ά phase transformation plays an important role in the deformation mechanisms of the TRIP effect in addition to dislocation glide. With Increasing Mn mass content large elongation is favoured by intensive twinning formation. The mechanical properties of plain iron manganese alloys are strongly influenced by the alloying elements, Al and Si. Alloying with Al Increases the stacking fault energy and therefore strongly suppresses the martensitic γ‐ε transformation, while Si sustains the γ‐ε transformation by decreasing the stacking fault energy γfcc. The γ‐ε phase transformation takes place in Fe‐Mn‐X alloys with γfcc ≤ 20 mJm−2. The developed light weight high manganese TRIP and TWIP (twinning induced plasticity) steels exhibit high ultimate tensile strength (600 to 1100 MPa) and extremely large elongation of 60 to 95 % even at high strain rates of έ = 103 s−1. Particularly due to the advanced specific energy absorption of TRIP and TWIP steels compared to conventional deep drawing steels high dynamic tensile and compression tests were carried out in order to investigate the change in the microstructure under near crash conditions. Tensile and compression tests of iron manganese alloys with varying Mn content were performed at different temperatures and strain rates. The resulting formation of γ twins, ά‐ and ε martensite by plastic deformation was analysed by optical microscopy and X‐ray diffraction. The deep drawing and stretch forming behaviour at varying deformation rates were determined by performing cupping tests and digitalised stress‐strain‐analysis.

Recent empirical and statistical evidence suggest that propagule pressure (i.e., number of individuals introduced per event, and the number and frequency of events) and colonization pressure (i.e., number of species released per event, and the number and frequency of events) are of vital importance to invasion success. To explore possible changes in propagule and colonization pressure during the transport stage of the invasion process, we examine abundance and species richness of virus-like particles, bacteria, diatoms, dinoflagellates, and invertebrates transported in commercial ships-a leading vector for global spread of aquatic nonindigenous species. We collected 154 ballast water samples from ships that had performed or were exempt from ballast water exchange (BWE) prior to arrival at Pacific and Atlantic ports in Canada and Laurentian Great Lakes ports. We found that abundance and species richness varied across taxa and regions, with ships arriving to the Atlantic region carrying the highest abundance of taxa. The highest species richness of invertebrates and diatoms was recorded from ships arriving to the Pacific, whereas the richest communities of dinoflagellates occurred in the Atlantic region. We also found that BWE had no effect on abundance or species richness of most taxa (dinoflagellates, diatoms, bacteria, and virus-like particles), whereas the effect on abundance of invertebrates was not clear. Finally, longer voyages resulted in lower abundance of all taxa except dinoflagellates, and lower species richness of diatoms. Paradoxically, the elevated abundance and species richness of dinoflagellates following BWE suggest that this group could have enhanced invasion potential when ships manage ballast water by exchange.