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  • 1
    Online Resource
    Online Resource
    The late Holocene demise of a sublittoral oyster bed in the North Sea
    Public Library of Science (PLoS) ; 2021
    In:  PLOS ONE Vol. 16, No. 2 ( 2021-2-16), p. e0242208-
    Details
    In: PLOS ONE, Public Library of Science (PLoS), Vol. 16, No. 2 ( 2021-2-16), p. e0242208-
    Abstract: A fossil oyster bed ( Ostrea edulis ) was recently encountered offshore Helgoland (German Bight). Oysters are important filter feeders in marine environments and their habitat structure supports a large associated biodiversity. The European flat oyster Ostrea edulis has historically occurred in vast populations in the North Sea, but declined massively in the early 20th century. The ecological restoration of Ostrea habitats is a current focal point in the North Sea. To better understand the mechanisms that caused the local collapse of the oyster population, this study investigated the size structure, weight, and age of the shells, along with the spatial dimensions, seafloor properties, and environmental context of the oyster bed. The results show that the demise of the population occurred around 700 CE, ruling out excessive harvest as a driver of decline. Synchronicity of increased geomorphological activity of rivers and concurrent major land use changes in early medieval Europe suggest that increased sedimentation was a viable stressor that reduced the performance of the oysters. The shells provided no indication of a demographically poor state of the oyster bed prior to its demise, but manifested evidence of the wide-spread occurrence of the boring sponge Cliona sp. Our study challenges the assumption of a stable preindustrial state of the European flat oyster in the North Sea, and we conclude that the long-term variability of environmental conditions needs to be addressed to benchmark success criteria for the restoration of O . edulis .
    Type of Medium: Online Resource
    ISSN: 1932-6203
    URL: Article
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    DOI: 10.1371/journal.pone.0242208
    DOI: 10.1371/journal.pone.0242208.g001
    DOI: 10.1371/journal.pone.0242208.g002
    DOI: 10.1371/journal.pone.0242208.g003
    DOI: 10.1371/journal.pone.0242208.g004
    DOI: 10.1371/journal.pone.0242208.g005
    DOI: 10.1371/journal.pone.0242208.t001
    DOI: 10.1371/journal.pone.0242208.t002
    DOI: 10.1371/journal.pone.0242208.s001
    DOI: 10.1371/journal.pone.0242208.s002
    DOI: 10.1371/journal.pone.0242208.s003
    DOI: 10.1371/journal.pone.0242208.s004
    DOI: 10.1371/journal.pone.0242208.r001
    DOI: 10.1371/journal.pone.0242208.r002
    DOI: 10.1371/journal.pone.0242208.r003
    DOI: 10.1371/journal.pone.0242208.r004
    Language: English
    Publisher: Public Library of Science (PLoS)
    Publication Date: 2021
    detail.hit.zdb_id: 2267670-3
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  • 2
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    Hydroacoustic Mapping of Geogenic Hard Substrates: Challenges and Review of German Approaches
    MDPI AG ; 2020
    In:  Geosciences Vol. 10, No. 3 ( 2020-03-09), p. 100-
    Details
    In: Geosciences, MDPI AG, Vol. 10, No. 3 ( 2020-03-09), p. 100-
    Abstract: Subtidal hard substrate habitats are unique habitats in the marine environment. They provide crucial ecosystem services that are socially relevant, such as water clearance or as nursery space for fishes. With increasing marine usage and changing environmental conditions, pressure on reefs is increasing. All relevant directives and conventions around Europe include sublittoral hard substrate habitats in any manner. However, detailed specifications and specific advices about acquisition or delineation of these habitats are internationally rare although the demand for single object detection for e.g., ensuring safe navigation or to understand ecosystem functioning is increasing. To figure out the needs for area wide hard substrate mapping supported by automatic detection routines this paper reviews existing delineation rules and definitions relevant for hard substrate mapping. We focus on progress reached in German approval process resulting in first hydroacoustic mapping advices. In detail, we summarize present knowledge of hard substrate occurrence in the German North Sea and Baltic Sea, describes the development of hard substrate investigations and state of the art mapping techniques as well as automated analysis routines.
    Type of Medium: Online Resource
    ISSN: 2076-3263
    URL: Article
    DOI: 10.3390/geosciences10030100
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2655946-8
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  • 3
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    Autumn migration of the migrant hawker (Aeshna mixta) at the Baltic coast
    Springer Science and Business Media LLC ; 2023
    In:  Movement Ecology Vol. 11, No. 1 ( 2023-08-24)
    Details
    In: Movement Ecology, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2023-08-24)
    Abstract: Migratory insects are important for the provision of ecosystem services both at the origin and destination sites but – apart from some iconic species – the migration routes of many insect species have not been assessed. Coastlines serve as a funnel where migrating animals including insects accumulate. Migratory behaviour and captures of dragonflies in bird traps suggest autumn migration of dragonflies along coastlines while the origin and regularity of this migration remain unclear. Methods Dragonfly species were caught at the bird observatory Kabli at the Baltic coast in Estonia in 2009, 2010 and 2015. For the 2015 data set, we used a stable hydrogen (H) approach to trace the potential natal origin of the migrant hawker ( Aeshna mixta ). Results 1079 (2009), 701 (2010) and 88 (2015) A. mixta individuals were caught during the study periods (35, 37 and 11 days in 2009, 2010 and 2015, respectively). The migration period lasted from end of August to end of September. Based on the results from our stable isotope analysis, we identified two populations of A. mixta : One (range of isotope signatures of non-exchangeable H [δ 2 H n wing ]: −78‰ to −112‰) had a local likely origin while the other (δ 2 H n wing : −113‰ to −147‰) migrated from northerly directions even in headwind from the South. The former showed an even sex ratio whereas the actively migrating population was dominated by males. Conclusions Our results suggest a regular southbound autumn migration of A. mixta along the Baltic coast. However, nearly half of the sampled individuals originated from the surroundings suggesting either no, partial or “leap-frog” migration. Contrary to our expectation, A. mixta did not select favourable wind conditions but continued the southbound autumn migration in the flight boundary layer even in case of headwinds. The dominance of males might indicate migration as a result of competition for resources. Further repeated, large-scale studies along the Baltic coast are necessary to pinpoint the migratory pattern and the reason for migration of A. mixta . Such studies should also comprise locations north of the known species range of A. mixta because of the rapid climate-change induced range expansion.
    Type of Medium: Online Resource
    ISSN: 2051-3933
    URL: Article
    DOI: 10.1186/s40462-023-00415-z
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 2724975-X
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  • 4
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    Invasive Vaucheria (Xanthophyceae) at the lower shore of the Wadden Sea
    Informa UK Limited ; 2022
    In:  Phycologia Vol. 61, No. 3 ( 2022-05-04), p. 274-283
    Details
    In: Phycologia, Informa UK Limited, Vol. 61, No. 3 ( 2022-05-04), p. 274-283
    Type of Medium: Online Resource
    ISSN: 0031-8884 , 2330-2968
    URL: Article
    DOI: 10.1080/00318884.2022.2035532
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2022
    detail.hit.zdb_id: 2243466-5
    detail.hit.zdb_id: 391102-0
    SSG: 12
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  • 5
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    Site selection for biogenic reef restoration in offshore environments: The Natura 2000 area Borkum Reef Ground as a case study for native oyster restoration
    Wiley ; 2020
    In:  Aquatic Conservation: Marine and Freshwater Ecosystems Vol. 30, No. 11 ( 2020-11), p. 2163-2179
    Details
    In: Aquatic Conservation: Marine and Freshwater Ecosystems, Wiley, Vol. 30, No. 11 ( 2020-11), p. 2163-2179
    Abstract: According to the EU Marine Strategy Framework Directive (2008/56/EC), marine protected areas (MPA) should contribute to a good environmental status of the Europeans seas. Measures maintaining or restoring a favourable conservation status of protected species and habitats are mandatory according to the EU Habitats Directive (92/43/EEC). Identification of suitable sites for ecological restoration measures within MPAs is a crucial step towards successful conservation and sustainable MPA management. In terms of species restoration, it is important to restore the respective species with the best possible environment for growth, survival, fitness, and successful recruitment. This study provides a comprehensive list of site‐selection criteria for ecological species restoration. Three general categories were chosen: (1) ecological history: evidence for the historical distribution; (2) feasibility of restoration: regulating framework and logistics; and (3) environmental conditions: quality of abiotic and biotic factors. A total of 16 site‐selection criteria were identified and applied to biogenic reef restoration, namely for reefs of the native European oyster Ostrea edulis , in the German Bight. The Natura 2000 area Borkum Reef Ground was identified as a suitable site for oyster restoration. It is one of three MPAs in the German Exclusive Economic Zone of the North Sea, which have been declared as Nature Conservation Areas according to national legislation. The conservation objectives include maintenance or, if necessary, restoration of the habitat type ‘reefs’. As a reef‐building species, the European oyster O. edulis is of particular importance for this habitat type in terms of nature conservation. The step by step approach for site selection presented here is applicable for biogenic reef restoration elsewhere. The selected Natura 2000 area showcases the potential role and future perspective of European MPAs with regards to active conservation measures.
    Type of Medium: Online Resource
    ISSN: 1052-7613 , 1099-0755
    URL: Issue
    URL: Article
    DOI: 10.1002/aqc.v30.11
    DOI: 10.1002/aqc.3405
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 1146285-1
    detail.hit.zdb_id: 1496050-3
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    SSG: 14
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  • 6
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    Multiannual Seafloor Dynamics around a Subtidal Rocky Reef Habitat in the North Sea
    MDPI AG ; 2022
    In:  Remote Sensing Vol. 14, No. 9 ( 2022-04-26), p. 2069-
    Details
    In: Remote Sensing, MDPI AG, Vol. 14, No. 9 ( 2022-04-26), p. 2069-
    Abstract: Rocky reefs provide complex structures in the otherwise largely sand-dominated coastal North Sea. Therefore, these reefs are highly important natural habitats for the functioning of coastal ecosystems, as they provide shelter, refuge and nursery grounds for various mobile and sessile species. In the North Sea, the spatial distribution of these habitats has been intensively investigated over recent years. However, these studies generally provide static accounts of the current state of these reef systems, but limited data exist on the temporal variations in sediment dynamics at and around natural rocky reefs. In this study, we provide observations from a multiannual time series of hydroacoustic seafloor surveys conducted at an isolated rocky reef in the North Sea. We use multibeam bathymetry and side-scan sonar backscatter data in combination with video observations, sediment sampling, and sub-bottom profiler data to assess the long-term variations of the rocky reef system. The reef is located in water depths between 11 and 17 m with an areal extent of ~0.5 km2 and is surrounded by mobile sands. The topography of the rocky reef appears to create a distinct hydrodynamic system that permits mobile sands to settle or move into bathymetrical deeper parts of the reef. Our results suggest a very dynamic system surrounding the reef with large scale scouring, sediment reworking and transport, while the shallower central part of the reef remains stable over time. We demonstrate the importance of hydrodynamics and current scouring around reefs for the local variability in seafloor properties over time. These small-scale dynamics are likewise reflected in the spatial distribution of sessile species, which are less abundant in proximity to mobile sands. The hydroacoustic mapping and monitoring of seafloor dynamics at higher spatial and temporal resolutions presents an important future direction in the study of valuable coastal habitats.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs14092069
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2513863-7
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  • 7
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    Online Resource
    Invading grass-like alga transforms rippled sand bars into bumpy muddy flats: arrival of a game changer in the Wadden Sea?
    Regional Euro-Asian Biological Invasions Centre Oy (REABIC) ; 2022
    In:  Aquatic Invasions Vol. 17, No. 1 ( 2022), p. 1-20
    Details
    In: Aquatic Invasions, Regional Euro-Asian Biological Invasions Centre Oy (REABIC), Vol. 17, No. 1 ( 2022), p. 1-20
    Type of Medium: Online Resource
    ISSN: 1818-5487
    URL: Issue
    URL: Journal
    URL: Article
    DOI: 10.3391/ai.2022.17.1
    DOI: 10.3391/ai
    DOI: 10.3391/ai.2022.17.1.01
    Language: Unknown
    Publisher: Regional Euro-Asian Biological Invasions Centre Oy (REABIC)
    Publication Date: 2022
    detail.hit.zdb_id: 2381496-2
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  • 8
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    Online Resource
    Persistent effects of sand extraction on habitats and associated benthic communities in the German Bight
    Copernicus GmbH ; 2021
    In:  Biogeosciences Vol. 18, No. 12 ( 2021-06-17), p. 3565-3577
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 18, No. 12 ( 2021-06-17), p. 3565-3577
    Abstract: Abstract. Sea-level rise demands for protection measures of endangered coastlines crucial for the local population. At the island of Sylt in the SE North Sea, shoreline erosion is compensated by replenishment with sand dredged from an offshore extraction site. We studied the long-term effects of sand extraction on bathymetry, geomorphology, habitats and benthic fauna. Sand extraction created dredging holes about 1 km in diameter and up to 20 m below the ambient seafloor level. Directly after dredging the superficial sediment layer, inside the pits was dominated by coarse sand and stones. Hydroacoustic surveys revealed only minor changes of bathymetry 〉 35 years after sand extraction. Obviously, backfill of the dredging pits was very slow, at a rate of a few millimeters per year, presumably resulting from low ambient sediment availability and relatively calm hydrodynamic conditions despite high wave energy during storms. Thus, a complete backfill of the deep extraction sites is likely to take centuries in this area. Hydroacoustic surveys and ground truthing showed that the backfilled material is mainly very fine sand and mud, turning the previously coarse sand surface into a muddy habitat. Accordingly, grab samples revealed significant differences in macrozoobenthos community composition, abundance and species density between recently dredged areas (〈 10 years ago), recovery sites (dredging activity 〉 10 years ago) and undisturbed sites (control sites). Overall, dredging turned the original association of sand-dwelling species into a muddy sediment association. Since re-establishment of disturbed benthic communities depends on previous re-establishment of habitat characteristics, the low sedimentation rates indicate that a return to a pre-dredging habitat type with its former benthic community and habitat characteristics is unlikely. Since coarse sand is virtually immobile in this area, a regeneration towards pre-dredging conditions is also unlikely without human interference (e.g., mitigation measures like depositing coarse material on the seafloor to restore the sessile epifauna).
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-18-3565-2021
    DOI: 10.5194/bg-18-3565-2021-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2158181-2
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