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Using local materials for scalable marine restoration: Xiriton as a nature-enriching, low impact building material
No full textMaterials currently used to produce reef structures are often limited by high production costs, negative environmental impacts or limited flexibility in design and degradability. We tested the ability of a novel concrete alternative, Xiriton, to i) exhibit adjustable erodibility using different mixtures, ii) limit the input of foreign products into the marine environment by using locally sourced building materials (e.g. local C4 grass Spartina anglica or Miscanthus giganteus, crushed shells and sand) and iii) facilitate the establishment of marine organisms. In addition to material testing of compressive strength, porosity and pH, we combined direct measurements of erosion in a fast flow flume with field measurements of erosion over time at different heights in the intertidal frame. Furthermore, we monitored the settlement of marine organisms onto Xiriton blocks placed into the field. We showed that i) while the erodibility of Xiriton can be made comparable with more conventional building materials, its degradability can be easily adjusted by altering the proportion of binding material in the mixture, ii) the use of locally sourced building materials did not reduce the structural integrity of the material but did minimise its potential long-term impacts on the environment, and that iii) Xiriton acts as a colonisable building material by facilitating the rapid establishment of species such as seaweeds, barnacles, Pacific oysters and blue mussels, and thus may enhance biodiversity. While further research is necessary to understand the longer-term behaviour and impacts of Xiriton, its simple production process, minimal short-term impacts and adjustable erodibility reveal a strong potential for its application in marine restoration using local ingredients on a global scale
Environmental risk framework and research recommendations for SMS mining in the Norwegian Arctic mid-ocean ridge
No full textTo meet future demands, mineral resources found in deposits along mid-ocean ridges have triggered the interest of the deep-sea mining industry. Comprehensive environmental management regulations are being developed by the International Seabed Authority (ISA) to control the exploitation of seabed areas beyond national jurisdiction. Norway has recently opened its seabed to mining exploration, which may potentially lead to future commercial exploitation of seafloor massive sulfides (SMS) and manganese crusts. Large uncertainties remain about the environmental consequences of such activities and improved knowledge is required to be able to describe and evaluate the associated environmental risks. An environmental risk assessment (ERA) is the process of assessing potential harm to the environment. In this paper, we apply a framework for environmental risk assessment as a mechanism to identify priority environmental knowledge, technology, and practice needed for future SMS mining operations. The ERA framework is aligned with the key elements of the draft ISA regulations and includes how risk terms and principles are understood and used by Norwegian policymakers and authorities. Regulatory draft documents, scientific literature, expert opinions, and an assessment of environmental severity, vulnerability, and value criteria have provided informative bases for the discussed research and development (R&D) recommendations. While the risk framework and associated R&D recommendations are aimed at future mining in the areas of the Arctic Mid-Ocean Ridge (AMOR) under Norwegian jurisdiction, they are also relevant to other areas of SMS exploitation and may form a useful template
Quantifying soil resistance to sheet and lateral erosion across different habitats on a managed sandy Back‐Barrier island
No full textBack-barrier islands are understudied, dynamic, soft-sediment coastal landscapes located in fetch-limited environments. They are of key ecological importance; however, they are threatened by global change impacts including increasing storm surges and sea level rise. This study aimed to investigate the soil erosion resistance to hydraulic forces of different habitats across a sandy back-barrier island with characteristic sandy subsoils that has been managed >100 years to prevent its complete erosion and submergence. We quantified sheet and lateral soil erosion resistance in flumes, investigated their correlations with sediment and belowground vegetation characteristics, and discussed how these characteristics may relate to the island\u27s past management and development. Soil cores were collected from the barrier dune ridge, back-barrier marshes and unvegetated sandflats and were exposed laterally to waves (lateral erosion) and horizontally to water flow (sheet erosion). Resistance to sheet and lateral erosion was not correlated. Resistance to lateral erosion depended on the thickness of the cohesive topsoil layer accreted by the marsh vegetation on top of a sandy subsoil. For instance, marsh soils with thin cohesive topsoils were resistant to sheet erosion (<0.5 cm erosion in 3 hr) but not to lateral erosion (collapsed within the first 10 min), which could make them vulnerable to wave attacks if they get laterally exposed during island erosion. Topsoil thickness was related to marsh elevation and age. In turn, the development of the cohesive layer may be related to the past management of the island, as soft engineering measures such as beach nourishments can create sheltered conditions for marsh development.</span
Warming winters promote biodiversity through reduced mortality of a habitat‐forming species in soft‐sediment intertidal systems
No full textHabitat-forming species enhance biodiversity by providing shelter, substrate and feeding grounds for many species. Climate-change effects on these species may have wide ranging impacts on local species richness and abundance. Warmer winter temperatures in particular are an important driver of demographic parameters in temperate to polar environments. However, the extent of these effects on local biodiversity remains unclear. We address this topic by studying the abundance of the tube-worm Lanice conchilega, a habitat-forming species that shows mass mortalities in intertidal areas after cold winters. Using 15 years of data collected throughout the intertidal Dutch Wadden Sea, we modelled population dynamics of L. conchilega relative to inundation and winter temperatures, and related its population growth to changes in species richness. Winter temperature was positively associated with L. conchilega\u27s population growth, which in turn correlated with increased local species richness. Specifically, for every 10-fold increase in L. conchilega population, 0.69 additional species were found. We conclude that increases in winter temperature promote L. conchilega\u27s abundance and, in turn, species richness due to its role as a habitat-forming species. The direct positive effect of warmer winters on L. conchilega abundance and the subsequent indirect effect on biodiversity might represent a silver lining within the environmental and biodiversity crisis we are facing.</span
Influence of Mediterranean oceanographic and environmental conditions on molecular proxy‐based sea surface temperature reconstructions during the last interglacial
No full textWe investigated the variability and phase relationship of two annually to subdecadally resolved sea surface temperature (SST) proxy records from the Mediterranean sapropel S5 deposited during the Last Interglacial. We compared our recently published alkenone-based SST record, considered to reliably represent surface temperature, with a newly generated record of archeal glycerol dialkyl glycerol tetraether (GDGTs). GDGT-based SST reconstruction in the Mediterranean Sea has been suggested to be affected by other parameters besides SST, and presumably represents subsurface temperature. Our investigation unveils notable differences between the two proxies; throughout most of the record, SST reconstructions derived from GDGTs and alkenones exhibit an anti-phase relationship in the multicentennial time band. This suggests that during sapropel deposition, centennial-scale alterations in the upper-ocean temperature gradient, plausibly due to water column stratification, influenced both compound classes. While we expect a direct, thermal driver for the alkenone ratio, the effect on the GDGT-based SST signal might have been mediated by ammonia oxidation rates that were positively correlated with changes in SST. A multidecadal comparison between GDGT- and alkenone-based SSTs reveals distinct behaviors of the two proxies under different oceanographic conditions, indicating that changing oceanographic and environmental dynamics significantly impacted short-term proxy variability. We demonstrate that during sapropel deposition in the Last Interglacial oceanographic, environmental and ecological factors played a crucial role in modulating the GDGT cyclization on both multidecadal and multicentennial time-scales, suggesting strong non-thermal forcing on GDGT-based SST reconstruction during Mediterranean sapropel deposition.</span
Establishing a comprehensive host-parasite stable isotope database to unravel trophic relationships
No full textOver the past decades, stable isotopes have been infrequently used to characterise host-parasite trophic relationships. This is because we have not yet identified consistent patterns in stable isotope values between parasites and their host tissues across species, which are crucial for understanding host-parasite dynamics. To address this, we initiated a worldwide collaboration to establish a unique database of stable isotope values of novel host-parasite pairs, effectively doubling the existing data in published literature. This database includes nitrogen, carbon, and sulphur stable isotope values. We present 3213 stable isotope data entries, representing 586 previously unpublished host-parasite pairs. Additionally, while existing literature was particularly limited in sulphur isotope values, we tripled information on this crucial element. By publishing unreported host-parasite pairs from previously unsampled areas of the world and using appropriate host tissues, our dataset stands unparalleled. We anticipate that end-users will utilise our database to uncover generalisable patterns, deepening our understanding of the complexities of parasite-host relationships and driving future research efforts in stable isotope parasitology.</span
Lower Meuse paleoflood record reveals NAO‐driven decadal to multi‐centennial variability
No full textA central challenge in assessing climate-driven flood regimes is constructing long-term paleoflood records with sufficient temporal resolution to identify both short- and long-term variability. To address this, we performed grain-size and X-ray fluorescence scanning analyses on two cores from paleochannels in the Lower Meuse (the Netherlands). The downcore ln(Zr/Rb) ratio proves to be a reliable grain-size proxy, allowing reconstruction of flood-related sediment input variations. We find the flood intensity record displays a ∼300-year cycle, synchronous to the North Atlantic Oscillation record at this band. Importantly, the recurring quasi-decadal (7–10 years) oscillation indicates an active and stationary high-frequency flooding regime despite significant climatic and human impacts in the Late Holocene. This study advances paleoflood methodology by demonstrating that paleochannel infills provide valuable archives for reconstructing flood histories across multi-annual to millennial intervals, thus enhancing our ability to track hydrological responses to climate variability across multiple timescales.</span
Site‐level connectivity identified from multiple sources of movement data to inform conservation of a migratory bird
No full textMigratory birds depend on a suite of sites across their annual cycles, making them vulnerable to a wide variety of anthropogenic pressures. Current area-based conservation measures have been found inadequate to safeguard migratory birds, in part due to a lack of consideration for the connectivity between sites mediated by the movements of individuals.To address this issue, we develop a network analysis integrating different types of individual movement data for a migratory shorebird, the Black-tailed Godwit (Limosa limosa), across the East Atlantic Flyway. Leveraging metal-ring recoveries, colour-ring re-sightings and satellite tracking from over 10,000 individual godwits, we quantify variation in connectivity between sites across the migratory range, using two weighted metrics to address sampling biases.Colour-ring re-sightings provided the largest number of sites (70%) and links (60% and 43% per season) overall, followed by tracking data (50% of sites, 49% and 63% of links per season) and ring recoveries (25% of sites, <1% of links per season), with clear regional variation in datatype contributions. Sampling completeness of the network structure varied with longitude, with information particularly lacking in central and eastern countries of both Europe and Africa.We identified 49 sites playing a disproportionate role in the site network, each with direct connections to 48 (interquartile range 32–84) other sites, on average. Just 23 (47%) top sites are formally recognized for their international importance for Black-tailed Godwits, and 33 (67%) were robust to sampling incompleteness. Across all 1058 sites, 20% lacked protected area coverage, and per site, 44% (44% ± SD) of bird relocations fell within protected areas.Integrating multiple sources of data improved geographical coverage and completeness of the site network, allowing us to quantify the importance of sites in terms of connectivity across the flyway. Our results highlight shortcomings of existing area-based conservation measures and add value to ongoing efforts to identify important sites for migratory birds.Policy implications. The increasing availability of individual movement data provides valuable opportunities to reveal the inter-dependence of sites used by migratory species, which can help identify priority areas and facilitate flyway-scale management.</ol
Atmospheric forcing dominates the interannual variability of convection strength in the Irminger Sea
No full textTransformation of light to dense waters by atmospheric cooling is key to the Atlantic Meridional Overturning Circulation in the Subpolar Gyre. Convection in the center of the Irminger Gyre contributes to the formation of the densest waters east of Greenland. We present a 19-year (2002–2020) weekly time series of hydrography and convection in the central Irminger Sea based on (bi-)daily mooring profiles supplemented with Argo profiles. A 70-year annual time series of shipboard hydrography shows that this mooring period is representative of longer-term variability. The depth of convection varies strongly from winter to winter (288–1,500 dbar), with a mean March mixed layer depth (MLD) of 470 dbar and a mean maximum density reached of 27.70 ± 0.05 kg m−3. The densification of the water column by local convection directly impacts the sea surface height in the center of the Irminger Gyre and thus large-scale circulation patterns. Both the observations and a Price-Weller-Pinkel mixed layer model analysis show that the main cause of interannual variability in MLD is the strength of the winter atmospheric surface forcing. Its role is three times as important as that of the strength of the maximum stratification in the preceding summer. Strong stratification as a result of a fresh surface anomaly similar to the one observed in 2010 can weaken convection by approximately 170 m on average, but changes in surface forcing will need to be taken into account as well when considering the evolution of Irminger Sea convection under climate change.</span
Sedimentary and faunistic effects of medium-deep sand mining along the Dutch coast
No full textThis paper presents the results of a study into the ecological long-term effects of medium-deep sand extraction along the Dutch coast. A comparison was made of the benthic fauna in and outside medium deep extraction pits of various ages, ranging between 2 and 12 years. The pits and reference areas were also compared in terms of water depth, median grain size, silt content and percentage of organic matter.The water depth of all sand extraction pits was on average 4 m larger than the surrounding reference areas. The average silt content in the extraction pits had increased by a factor 4 compared to the surrounding reference areas. The average silt content in the pits was 9.5 %. This increase differed between pits (0 and 46 %). The percentage of organic matter had almost doubled from 0.87 % in the reference areas to 1.50 % in the pits.The medium-deep sand extraction pits are faunistically characterized by a higher average macro-benthic biomass and density but the number of species shows no clear difference with the reference areas. Faunistic heterogeneity in the pits is lower than in the surrounding reference areas. The macro-fauna in the pits is characterized by the greater abundance of deposit feeders and interface feeders while the benthic fauna in the reference areas is characterized by bivalves i.e. filter feeders. Small demersal fish did not show clear trends although some species, such as sandeel, showed a difference in abundance between pit and reference area. The effect of age of the mining pit on faunistic composition could not be separated from differences related to geographical position.The results of this study show that recolonization of a newly mined medium deep sand extraction pit is fast but that the complete recovery and return of the original benthic fauna in these pits can be a very long process. The sedimentary differences between the pits suggests that recovery depends on the abiotic environment. The data suggest that by moving from shallow mining pits to medium deep pits a critical depth is passed beyond which hydrographical changes alter the settlement of fines and determine the composition of the macrofaunal community