32181 research outputs found
Sort by
DNA barcoding of benthic species from the Belgian part of the North Sea for diversity impact assessments
Get PDFSpecies living in or near the seafloor fulfill a variety of ecosystem functions. Understanding how benthic communities respond to human activities is crucial to determine how such activities impact the functioning of the benthic environment. In the Belgian part of the North Sea, ILVO is extensively monitoring different benthic ecosystem components, and explores new ways to characterise the structural and functional benthic diversity. DNA-based approaches such as metabarcoding may complement and speed up the characterisation of changes noted in these communities during impact assessments. Linking sequences to taxonomic data is indispensable when information on ecosystem functioning is the key concern. However, the taxonomic resolution of metabarcoding is still hampered by a lack of reliable reference sequence data to which the metabarcode sequences can be compared. We compiled longterm monitoring data from soft sediment macrobenthic, epibenthic and pelagic fish communities in the Belgian part of the North Sea. For macrobenthos, 334 species belonging to nine phyla have been registered in the past 15 years. The classes Polychaeta, Malacostraca and Bivalvia are the most species rich and include 40%, 37% and 13% of all species, respectively. ILVO aims to barcode as many benthic species as possible to validate and - when proven to be reliable - to implement DNA-based methods for biodiversity impact assessments. To this end, ethanol preserved voucher specimens are morphologically identified, photographed and stored as reference material for DNA sequencing. Partial or whole specimens are subjected to DNA extraction and COI Sanger sequencing. At present, the genetic reference database contains 95 macrobenthic species, representing the aforementioned classes and phyla. In addition, 85 epibenthic species and demersal/benthopelagic fish have been barcoded. Collection and sequencing of additional species is an ongoing effort. Next to DNA barcoding, we also explore new library preparation methods for high throughput sequencing of benthic communities by using different COI primer sets and primer free approaches such as long read 18S rRNA sequencing, on mock communities, ethanol fixatives and field samples. These methods will be compared to morphologically identified samples to assess whether comparable patterns in species and functional diversity patterns in impacted versus non-impacted sediments are found by the different approaches
Synthese van het wetenschappelijk onderzoek in de context van Vlaamse Baaien – Met de Belgische Oostkust als focusgebied
Get PDFOfficiële lijst van de Belgische vissersvaartuigen = Liste officielle des navires de pêche belges. Toestand op 01/01/2018
Get PDFWhere to go during winter? Habitat use does not shape variation in migratory strategies in lesser black-backed gulls
Get PDFThe impact of decades of environmental change on phytoplankton communities in the Belgian part of the North Sea
Get PDFOcean current connectivity propelling the secondary spread of a marine invasive comb jelly across western Eurasia
Get PDFAim: Invasive species are of increasing global concern. Nevertheless, the mechanisms driving furtherdistribution after the initial establishment of non-native species remain largely unresolved, especiallyin marine systems. Ocean currents can be a major driver governing range occupancy, but this hasnot been accounted for in most invasion ecology studies so far. We investigate how well initialestablishment areas are interconnected to later occupancy regions to test for the potential role ofocean currents driving secondary spread dynamics in order to infer invasion corridors and thesource–sink dynamics of a non-native holoplanktonic biological probe species on a continental scale.Location: Western Eurasia.Time period: 1980s–2016.Major taxa studied: ‘Comb jelly’ Mnemiopsis leidyi.Methods: Based on 12,400 geo-referenced occurrence data, we reconstruct the invasion historyof M. leidyi in western Eurasia. We model ocean currents and calculate their stability to match thetemporal and spatial spread dynamics with large-scale connectivity patterns via ocean currents.Additionally, genetic markers are used to test the predicted connectivity between subpopulations.Results: Ocean currents can explain secondary spread dynamics, matching observed range expansionsand the timing of first occurrence of our holoplanktonic non-native biological probe species,leading to invasion corridors in western Eurasia. In northern Europe, regional extinctions after coldwinters were followed by rapid recolonizations at a speed of up to 2,000 km per season. SourceJASPERS ET AL. | 815areas hosting year-round populations in highly interconnected regions can re-seed genotypes overlarge distances after local extinctions.Main conclusions: Although the release of ballast water from container ships may contribute tothe dispersal of non-native species, our results highlight the importance of ocean currents drivingsecondary spread dynamics. Highly interconnected areas hosting invasive species are crucial forsecondary spread dynamics on a continental scale. Invasion risk assessments should considerlarge-scale connectivity patterns and the potential source regions of non-native marine species
Future scenarios of marine resources and ecosystem conditions in the Eastern Mediterranean under the impacts of fishing, alien species and sea warming
Get PDFUsing a temporal-dynamic calibrated Ecosim food web model, we assess the effects of future changes on marine resources and ecosystem conditions of the Israeli Mediterranean continental shelf. This region has been intensely invaded by Indo-Pacific species. The region is exposed to extreme environmental conditions, is subjected to high rates of climate change and has experienced intense fishing pressure. We test the impacts of a new set of fishing regulations currently being implemented, a continued increase in sea temperatures following IPCC projections, and a continued increase in alien species biomass. We first investigate the impacts of the stressors separately, and then we combine them to evaluate their cumulative effects. Our results show overall potential future benefits of fishing effort reductions, and detrimental impacts of increasing sea temperature and increasing biomass of alien species. Cumulative scenarios suggest that the beneficial effects of fisheries reduction may be dampened by the impact of increasing sea temperature and alien species when acting together. These results illustrate the importance of including stressors other than fisheries, such as climate change and biological invasions, in an ecosystem-based management approach. These results support the need for reducing local and regional stressors, such as fishing and biological invasions, in order to promote resilience to sea warming
Global Carbon Budget 2018
Get PDFAccurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use and land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2008–2017), EFF was 9.4±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.7±0.02 GtC yr−1, SOCEAN 2.4±0.5 GtC yr−1, and SLAND 3.2±0.8 GtC yr−1, with a budget imbalance BIM of 0.5 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2017 alone, the growth in EFF was about 1.6 % and emissions increased to 9.9±0.5 GtC yr−1. Also for 2017, ELUC was 1.4±0.7 GtC yr−1, GATM was 4.6±0.2 GtC yr−1, SOCEAN was 2.5±0.5 GtC yr−1, and SLAND was 3.8±0.8 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 405.0±0.1 ppm averaged over 2017. For 2018, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.7 % (range of 1.8 % to 3.7 %) based on national emission projections for China, the US, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. The analysis presented here shows that the mean and trend in the five components of the global carbon budget are consistently estimated over the period of 1959–2017, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations show (1) no consensus in the mean and trend in land-use change emissions, (2) a persistent low agreement among the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models, originating outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018, 2016, 2015a, b, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2018
Drivers of nematode community structure and of nematode microbiomes on an estuarine intertidal flat
Get PDFEstuarine tidal flat sediments are highly productive and biologically rich ecosystems. Their secondary production provides nutrition to large numbers of migratory bird populations and to commercially relevant shellfish and fish stocks. This high productivity can be driven by a range of organic matter subsidies, including deposited phytoplankton and detritus of both terrestrial and marine origin, macroalgae, seagrasses and/or salt marsh vegetation. In most cases, however, the in situ productivity of microbial biofilms fuels a major part of the secondary production on estuarine intertidal flats. These biofilms are complex consortia of benthic microalgae and heterotrophs embedded in a biogenic polymer matrix. They play key roles in a range of important ecosystem functions, such as sediment stabilization and water quality improvement. Nevertheless, several unknowns still exist about the complex interplay between microphytobenthos (MPB), prokaryotes and benthic invertebrates in microbial biofilms on tidal flats. Nematodes are by far the most abundant metazoans, and are also among the most species-rich taxa in estuarine and marine soft substrates and their biofilms. Their high abundances and generally high biomass turnover rates have caused speculation about their importance in tidal flat sediments. Their grazing and non-trophic interactions with biofilm-forming organisms may affect the activity and community structure of both MPB and of sediment bacteria, and thus probably also affect some of the ecosystem processes mediated by these micro-organisms. In addition, nematodes can be an important food source for higher trophic levels. Thus, nematodes may represent an important trophic link between biofilm-forming organisms and higher trophic levels. Moreover, the high local-scale species diversity of nematodes has puzzled ecologists for decades. Differential resource use is often invoked as a basis for niche differentiation among species, yet the vast majority of studies demonstrating that this would be prominent in marine nematodes are based on laboratory experiments on single species or on highly simplified assemblages, leaving the issue of resource differentiation under natural conditions rather understudied until present