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In recent decades, mussel beds in the northern Atlantic and Scandinavia have declined rapidly in extent due to anthropogenic impacts, similar to many other marine habitats. In this study, a large‐scale restoration experiment was conducted to identify major challenges that arise during restoration efforts on shallow subtidal mussel beds. Suspension‐grown mussels (Mytilus edulis) were relayed in two different treatments either directly on bare bottom sandy sediments, or on coir nets (Net), used as a proxy for suitable byssal attachment substrate. The treatments were monitored for 1.5 years and coverage (%), biomass (WW), and population dynamics were quantified. Two main challenges of shallow bed restoration were identified: (1) Lack of suitable attachment substrate resulting in dislodgment of individuals during storm events. The Net treatment had significantly higher coverage and biomass of Mytilus at the end of the monitoring period, clearly demonstrating the importance of suitable substrate at physically exposed locations. (2) High mortality of juvenile mussels. Population dynamics revealed a high mortality of juvenile Mytilus, which resulted in almost complete loss of relayed Mytilus individuals less than 30 mm within the first season. This was most likely due to high meso‐predator densities, as a result of declining top‐predator populations. The high mortality of juvenile Mytilus prevented successful annual recruitment, thereby making the population unsustainable long‐term. Both challenges need to be addressed to create stable beds during restoration. Additionally, the experiment demonstrated the viability of using suspension‐grown Mytilus as a seed‐source when restoring mussel beds. [ABSTRACT FROM AUTHOR]

Loading, retention, and in-lake cycling of phosphorus (P), nitrogen, silica, and dissolved organic carbon (DOC) were studied 1 year before and 3 years after P-inactivation by aluminum (Al) hydroxide in Danish Lake Nordborg in 2006. Simultaneously, external P loading was reduced by 40% via establishment of precipitation ponds in two inlets. After Al treatment, the internal P loading (sediment P release) during summer declined 90%-94%, owing to adsorption to aluminum hydroxide. Also, silicate regeneration from the sediment was reduced by 69%-76%, and sediment oxygen uptake as well as ammonium release declined markedly. Consequently, lake water total P, dissolved inorganic P, silicate, and DOC decreased by 73%, 97%, 87%, and 46%, respectively. The Secchi depth increased in the summer period during the first post-treatment year, but declined afterwards to pre-treatment levels, even though the mean lake-water total P concentration during summer was reduced from ~240 µg x [L.sup.-1] before treatment to 26-65 µg x [L.sup.-1] in the first three post-treatment years. We conclude that a further reduction in external P loading is needed to obtain the full effect of the Al treatment in Lake Nordborg. Nous avons determine l'apport, la retention et le recyclage au sein meme du lac du phosphore (P), de l'azote, de la silice et du carbone organique dissous (DOC) un an avant et trois ans apres l'inactivation du P par l'hydroxyde d'aluminium (Al) dans le lac Norborg au Danemark en 2006. Au meme moment, la charge externe de P a ete reduite de 40% par l'etablissement d'etangs de sedimentation sur deux tributaires. Apres le traitement a Al, l'apport interne de P (liberation de P par les sediments) durant l'ete a decline de 90-94% a cause de l'adsorption a l'hydroxyde d'aluminium. De plus, la regeneration du silicate a partir des sediments a ete reduite de 69-76% et l'absorption d'oxygene par les sediments de meme que la liberation d'ammonium ont diminue de facon marquee. En consequence, le P total, le P inorganique dissous, le silicate et le DOC ont diminue dans l'eau du lac par respectivement 73%, 97%, 87% et 46%. La profondeur de Secchi s'est accrue durant la periode d'ete de la premiere annee apres le traitement, mais a decru ensuite pour atteindre les valeurs d'avant le traitement, meme si la concentration moyenne de P total a diminue de ~240 µg x [L.sup.-1] avant le traitement a 26-65 µg x [L.sup.-1] dans les trois premieres annees apres le traitement. Nous concluons qu'une reduction supplementaire de l'apport externe de P est necessaire afin d'obtenir le plein effet du traitement a l'Al dans le lac Norborg. [Traduit par la Redaction], Introduction Aluminum (Al) treatment has been widely used as a restoration tool in eutrophic lakes to precipitate phosphorus (P) in the lake water, and to reduce internal P release (e.g., [...]

Traditional monitoring (e.g., in-water based surveys) of eelgrass meadows and perennial macroalgae in coastal areas is time and labor intensive, requires extensive equipment, and the collected data has a low temporal resolution. Further, divers and Remotely Operated Vehicles (ROVs) have a low spatial extent that cover small fractions of full systems. The inherent heterogeneity of eelgrass meadows and macroalgae assemblages in these coastal systems makes interpolation and extrapolation of observations complicated and, as such, methods to collect data on larger spatial scales whilst retaining high spatial resolution is required to guide management. Recently, the utilization of Unoccupied Aerial Vehicles (UAVs) has gained popularity in ecological sciences due to their ability to rapidly collect large amounts of area-based and georeferenced data, making it possible to monitor the spatial extent and status of SAV communities with limited equipment requirements compared to ROVs or diver surveys. This paper is focused on the increased value provided by UAV-based, data collection (visual/Red Green Blue imagery) and Object Based Image Analysis for gaining an improved understanding of eelgrass recovery. It is demonstrated that delineation and classification of two species of SAV (Fucus vesiculosus and Zostera marina) is possible; with an error matrix indicating 86–92% accuracy. Classified maps also highlighted the increasing biomass and areal coverage of F. vesiculosus as a potential stressor to eelgrass meadows. Further, authors derive a statistically significant conversion of percentage cover to biomass (R 2 = 0.96 for Fucus vesiculosus, R 2 = 0.89 for Zostera marina total biomass, and R 2 = 0.94 for AGB alone, p < 0.001). Results here provide an example of mapping cover and biomass of SAV and provide a tool to undertake spatio-temporal analyses to enhance the understanding of eelgrass ecosystem dynamics. [ABSTRACT FROM AUTHOR]

Information on the physical and ecological state of streams along with an overview of the need for maintenance is traditionally a time-consuming manual field task with subsequent limitations in area coverage. Here we propose a novel approach to stream monitoring and management using a low-cost Unmanned Aerial Vehicle (UAV) platform to collect data comparable to that from traditional monitoring schemes. This technology provides high-resolution imagery while being easy to implement at a low cost along with providing data that represent the stream in both fine-scale and at landscape scale. The results show a significant correlation between results obtained by the two methods, with the largest difference in DFI values being 10, but in many cases being <5. The UAV-method is especially strong in supporting geographical measurements of stream width and course along with certain stream parameters such as physical variation, water flow and gravel coverage. The results indicate that UAV mapping of streams is a feasible alternative or support to the traditional mapping of certain open stream types with the possibility of covering more area with the same time-use. [ABSTRACT FROM AUTHOR]

Zostera muelleri , the dominant seagrass species along the eastern coastline of Australia, has declined due to anthropogenic stressors, including reduced water clarity. Water quality has improved in recent years, but restoration efforts are hampered by limited knowledge of transplantation methods. To support future restoration efforts, we tested multiple techniques for transplanting mature seagrass shoots: (1) sediment cores with intact seagrass plants (plug); (2) individual shoots anchored on frames (frame); (3) frame methods combined with subsurface mats to exclude bioturbating animals (mat + frame); (4) above-ground cages to exclude grazing fish (cage + frame); and (5) combined treatment of above-ground cages and subsurface mats (cage + mat + frame). Transplant success over 10 months showed considerable variability among locations. At one site, seagrass persisted in all treatments, with highest growth in the mat + frame treatment. At two locations, uncaged shoots were lost within 6–35 days of transplanting, presumably due to grazing by fish. In treatments with cages, growth was again highest in the mat + frame treatment. At the fourth location, all seagrass was lost due to physical stress. Thus, we conclude that transplantation success is highest using the mat + frame technique, but overall success depends on careful assessment of biotic and abiotic stressors at the chosen locations. The seagrass Zostera muelleri has, in recent decades, declined massively along the eastern coastline of Australia. To restore this important marine plant, we tested multiple techniques for transplanting mature adult seagrass shoots. Results showed that transplantation works best when shoots are anchored and bioturbating animals are excluded. However, in areas where grazing fish are present, the transplanted shoots should be further protected by placement of cages above the shoots. [ABSTRACT FROM AUTHOR]