Les écailles de plus de 10.000 adultes de truites de mer capturés principalement par piégeage à la remontée sur l'Orne et la Touques (Basse-Normandie) ont été examinées. L'interprétation de ces écailles et leur validation parla recapture d'individus marqués a permis de : — distinguer trois phases de croissance de l'écaillé caractéristiques d'un migrateur amphibiotique à nos latitudes: rivière, transition, mer. — déterminer relativement facilement l'âge d'eau douce des poissons en raison d'une bonne croissance des juvéniles permettant d'identifier correctement les bandes hivernales. — définir quatre types de poissons à partir de l'âge de mer de première reproduction. — caractériser la marque de reproduction qui se singularise chez cette espèce à frais multiples par l'importance de l'érosion de l'écaille dans sa partie postérieure. Cette marque est d'autant plus prononcée que le poisson a un âge marin élevé à la première reproduction. — déceler des structures particulières et propres à ces poissons en liaison avec des comportements migratoires variés lors du stade post-smolt. Scales of more 10.000 sea-trout (Salmo trutta L.) adults mainly trapped in the R. Orne and R. Touques (Lower Normandy) were analysed. Their interpretation and the validation of scales structures by the recapture of tagged fish have shown : — a typical distinction between growth zones on the scale for an amphibiotic migratory fish in that latitude: freshwater, run-out and sea growth. — an easy determination of the freshwater age because of a high growth during the juvenile stage resulting in an accurate identification of winter bands. — the definition of four sea-trout types according to the sea age at the first reproduction period. — a spawning mark characterized by a large erosion at the posterior edge of the scale in this multispawner fish. The erosion of the scale increases with the sea age at the first reproduction. — the existence of particular structures related to various migratory behaviours during post-smolt stage

We evaluated bird and small mammal use of two mowed (15 to 25 cm height) and two unmowed vegetation plots (40 to 88 ha) at John F. Kennedy International Airport (JFKIA), New York, in 1998 to 1999 to determine which management strategy would best reduce wildlife use of the airport. We counted more birds per 5- minute observation period in unmowed plots than mowed plots in both 1998 (9.0 versus 7.9) and 1999 (11.7 versus 8.6). Maximum vegetation height was greater (P<0.05) for unmowed areas than mowed areas after mowing commenced in 1998 and 1999 for each two-week monitoring period. In 1998 to 1999, vegetation density was also higher (P<0.05) for unmowed plots for 13 of 14 sampling periods. The species composition of vegetation differed (X2=20.54, df=3, (P<0.01) among mowed and unmowed plots. Mowed plots contained a higher percentage of grasses (81% versus 68%), and a lower percentage of forbs (16% versus 25%) and woody plants (1% versus 4%) than unmowed plots. Vegetation was generally sparse in both unmowed and mowed plots, a consequence of the poor, sandy soils on much of the airport. We captured 33 small mammals from three species in unmowed plots and 12 individuals of one species in mowed plots in 1999. Small mammal populations increased seasonally in unmowed plots, but remained constant in mowed plots over the same time period. We recommended JFKIA switch from the unmowed vegetation management regime in place since 1986 to a regime of maintaining vegetation mowed at 15 to 25 cm height. This management strategy should reduce bird and small mammal use of grassland areas at JFKIA. Further research should examine use of alternative vegetation types to improve ground cover and vegetation density at JFKIA while minimizing attraction to wildlife.

While the global impact of the edible cockle Cerastoderma edule on microphytobenthos (MPB) dynamics has been extensively studied, some underlying processes remain unknown, such as their non-trophic interactions. For this purpose, a laboratory mesocosm experimental approach was used to quantify the bioturbation generated by C. edule adults and their influence on oxygen and nutrient fluxes, MPB biomass and photosynthetic performance at the sediment-water interface. The effects of sediment properties and cockle densities (0, 288, 720 and 1,297 ind. m⁻²) were also investigated. Our results showed that cockles exert a net negative density-dependent effect on MPB biomass, with intensity varying according to sediment type. This is mainly due to sediment reworking by cockles and their emergence at the sediment surface, mechanically disrupting MPB biofilms. Nonetheless, the physiological status and photosynthetic performances of the remaining MPB cells were not impacted. This could be explained by cockle bioirrigation which stimulates nutrient fluxes at the sediment surface and cell turnover. In the finest sediment, the stimulation of MPB growth by nutrient fluxes did not compensate algal biomass loss due to burial, leading to a net decrease in MPB biomass. In coarser sediment, no significant impact of cockles on the net total MPB biomass was observed. This indicates a balance between suboptimal sediment condition for MPB, biofilm destruction by cockles, and enhanced bioirrigation rates that increase nutrient availability for MPB biofilms at the sediment-water interface.

Coastal marshes are key habitats contributing to organic carbon (OC) storage but remain understudied in Nordic regions regarding Blue Carbon processes. This study quantified OC stocks in above- and below-ground biomass and in the top 50 cm-soil across 12 grazed and ungrazed marshes, spanning major environmental gradients, and assessed how biotic (plant communities, livestock grazing) and abiotic (soil properties, environmental conditions) drivers shape OC storage. Grazing and environmental gradients strongly structured plant communities, partly by regulating the reed Phragmites australis, prevalent in ungrazed sites. Aboveground OC stocks were reduced by grazing, both directly through biomass removal and indirectly by reducing reed dominance. Belowground OC stocks were driven by plant community composition and indirectly by grazing effects on vegetation. Root biomass was concentrated in the top 15 cm in grazed sites and deeper (15–50 cm) in ungrazed sites, reflecting contrasting plant strategies. Abiotic soil properties were major large-scale drivers of soil OC storage, while grazing affected soil OC storage indirectly through plant composition. Soil OC stocks accounted for ∼73 % of total OC in grazed sites and ∼63 % in ungrazed ones and was higher in grazed sites (99.7 ± 57.9 Mg ha⁻¹) than in ungrazed sites (78.2 ± 44.2 Mg ha⁻¹). Soil OC increased with finer textures, whereas vegetation and grazing effects were variable and locally expressed. Overall, soil OC stocks in Nordic coastal marshes fall within the lower range of global estimates. These findings highlight the need to consider soil processes, grazing and environmental gradients tin the sustainable management of Nordic coastal marshes and their carbon storage potential.

Saltmarshes, recognized as effective organic carbon (OC) sinks, have gained attention for their potential contribution to climate mitigation through protection and restoration. However, the heterogeneous and geologically young nature of Nordic coastal marshes likely explains the limited research on their climate mitigation potential. To fill this gap, we examined soil OC storage, long-term OC accumulation rates, and soil methane emissions across four Nordic coastal marshes spanning broad climate and environmental gradients. Additionally, we evaluated the effects of grazing, a common management practice. The four Nordic saltmarshes assessed store a median of 7 kg OC m−2 (interquartile range, IQR: 8–6) in the top 15-35 cm of soil and accumulate 41 g OC m−2 yr−1 (IQR: 47–32). Considering only the saltmarsh's additional OC, most relevant to climate mitigation, these values drop to 4 kg OC m−2 (IQR: 6–2) and 21 g OC m−2 yr−1 (IQR: 33–11). Globally, both rates are comparatively low. Higher saltmarsh age and root:shoot ratio strongly and positively correlated with OC stocks and accumulation rates. The elevated root:shoot ratios seemed a morphological adaption to stressful conditions (higher soil salinity, slightly alkaline soils, warmer temperatures, and low water and nutrient availability) reflected in the saltmarsh plant composition. Soil methane emissions reduced the climate benefit of OC accumulation by 0.15–7.3% in Danish saltmarshes, which remained strong CO2eq sinks, but by 70% in Finnish saltmarshes, leaving them as much weaker sinks. Grazing slightly increased soil OC stocks but did not affect OC accumulation rates or methane fluxes. However, greenhouse gas emissions from livestock farming, even at low grazing intensity, largely outweighed saltmarsh climate benefits. A comprehensive Nordic saltmarsh management strategy is needed, extending beyond the current focus on biodiversity to include coastal protection, nutrient retention, and other ecosystem services, including their limited, yet relevant, role in climate mitigation.

Coastal marshes are key habitats contributing to organic carbon (OC) storage but remain understudied in Nordic regions regarding Blue Carbon processes. This study quantified OC stocks in above- and below-ground biomass and in the top 50 cm-soil across 12 grazed and ungrazed marshes, spanning major environmental gradients, and assessed how biotic (plant communities, livestock grazing) and abiotic (soil properties, environmental conditions) drivers shape OC storage. Grazing and environmental gradients strongly structured plant communities, partly by regulating the reed Phragmites australis, prevalent in ungrazed sites. Aboveground OC stocks were reduced by grazing, both directly through biomass removal and indirectly by reducing reed dominance. Belowground OC stocks were driven by plant community composition and indirectly by grazing effects on vegetation. Root biomass was concentrated in the top 15 cm in grazed sites and deeper (15–50 cm) in ungrazed sites, reflecting contrasting plant strategies. Abiotic soil properties were major large-scale drivers of soil OC storage, while grazing affected soil OC storage indirectly through plant composition. Soil OC stocks accounted for ∼73 % of total OC in grazed sites and ∼63 % in ungrazed ones and was higher in grazed sites (99.7 ± 57.9 Mg ha⁻¹) than in ungrazed sites (78.2 ± 44.2 Mg ha⁻¹). Soil OC increased with finer textures, whereas vegetation and grazing effects were variable and locally expressed. Overall, soil OC stocks in Nordic coastal marshes fall within the lower range of global estimates. These findings highlight the need to consider soil processes, grazing and environmental gradients tin the sustainable management of Nordic coastal marshes and their carbon storage potential.