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Nutrient, pigment, suspended matter and turbidity measurements in the Belgian part of the North Sea
Get PDFThrough regular sampling surveys, the Flanders Marine Institute is generating long term data series for the Belgian coastal water and sand bank systems, a designated site in the Long Term Ecological Research (LTER) network. The data series is built on sampling activities initiated in 2002, but gradually upgraded and extended in the framework of the LifeWatch marine observatory and the Integrated Carbon Observation System (ICOS) participation. Nine nearshore stations are sampled monthly, with additional seasonal sampling of eight offshore stations. This paper presents the generated data series for nutrients, pigments, suspended matter and turbidity. The collection, methodology and processing of the 2002–2018 dataset is described, along with its data curation, integration and quality control. Yearly versions of the data are published online in a standardized format, accompanied with extensive metadata description and labelled with digital identifiers for traceability. Data is published under a CC-BY license, allowing use of the data under the condition of providing reference to the original source
New ecosystems in the deep subsurface follow the flow of water driven by geological activity
Get PDFEukarya have been discovered in the deep subsurface at several locations in South Africa, but how organisms reach the subsurface remains unknown. We studied river-subsurface fissure water systems and identified Eukarya from a river that are genetically identical for 18S rDNA. To further confirm that these are identical species one metazoan species recovered from the overlying river interbred successfully with specimen recovered from an underlying mine at -1.4 km. In situ seismic simulation experiments were carried out and show seismic activity to be a major force increasing the hydraulic conductivity in faults allowing organisms to create ecosystems in the deep subsurface. As seismic activity is a non-selective force we recovered specimen of algae and Insecta that defy any obvious other explanation at a depth of -3.4 km. Our results show there is a steady flow of surface organisms to the deep subsurface where some survive and adapt and others perish. As seismic activity is also present on other planets and moons in our solar system the mechanism elucidated here may be relevant for future search and selection of landing sites in planetary exploration
Land–sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing
Get PDFWe assess the disputed phase relations between forcing and climatic response in the early Pleistocene with a spliced Gelasian (∼ 2.6–1.8 Ma) multi-proxy record from the southern North Sea basin. The cored sections couple climate evolution on both land and sea during the intensification of Northern Hemisphere glaciation (NHG) in NW Europe, providing the first well-constrained stratigraphic sequence of the classic terrestrial Praetiglian stage. Terrestrial signals were derived from the Eridanos paleoriver, a major fluvial system that contributed a large amount of freshwater to the northeast Atlantic. Due to its latitudinal position, the Eridanos catchment was likely affected by early Pleistocene NHG, leading to intermittent shutdown and reactivation of river flow and sediment transport. Here we apply organic geochemistry, palynology, carbonate isotope geochemistry, and seismostratigraphy to document both vegetation changes in the Eridanos catchment and regional surface water conditions and relate them to early Pleistocene glacial–interglacial cycles and relative sea level changes. Paleomagnetic and palynological data provide a solid integrated timeframe that ties the obliquity cycles, expressed in the borehole geophysical logs, to Marine Isotope Stages (MIS) 103 to 92, independently confirmed by a local benthic oxygen isotope record. Marine and terrestrial palynological and organic geochemical records provide high-resolution reconstructions of relative terrestrial and sea surface temperature (TT and SST), vegetation, relative sea level, and coastal influence.During the prominent cold stages MIS 98 and 96, as well as 94, the record indicates increased non-arboreal vegetation, low SST and TT, and low relative sea level. During the warm stages MIS 99, 97, and 95 we infer increased stratification of the water column together with a higher percentage of arboreal vegetation, high SST, and relative sea level maxima. The early Pleistocene distinct warm–cold alterations are synchronous between land and sea, but lead the relative sea level change by 3000–8000 years. The record provides evidence for a dominantly Northern Hemisphere-driven cooling that leads the glacial buildup and varies on the obliquity timescale. Southward migration of Arctic surface water masses during glacials, indicated by cool-water dinoflagellate cyst assemblages, is furthermore relevant for the discussion on the relation between the intensity of the Atlantic meridional overturning circulation and ice sheet growth
Trait-based approaches in rapidly changing ecosystems: A roadmap to the future polar oceans
Get PDFPolar marine regions are facing rapid changes induced by climate change, with consequences for local faunal populations, but also for overall ecosystem functioning, goods and services. Yet given the complexity of polar marine ecosystems, predicting the mode, direction and extent of these consequences remains challenging. Trait-based approaches are increasingly adopted as a tool by which to explore changes in functioning, but trait information is largely absent for the high latitudes. Some understanding of trait–function relationships can be gathered from studies at lower latitudes, but given the uniqueness of polar ecosystems it is questionable whether these relationships can be directly transferred. Here we discuss the challenges of using trait-based approaches in polar regions and present a roadmap of how to overcome them by following six interlinked steps: (1) forming an active, international research network, (2) standardizing terminology and methodology, (3) building and crosslinking trait databases, (4) conducting coordinated trait-function experiments, (5) implementing traits into models, and finally, (6) providing advice to management and stakeholders. The application of trait-based approaches in addition to traditional species-based methods will enable us to assess the effects of rapid ongoing changes on the functioning of marine polar ecosystems. Implementing our roadmap will make these approaches more easily accessible to a broad community of users and consequently aid understanding of the future polar oceans
Characteristics of meiofauna in extreme marine ecosystems: a review
Get PDFExtreme marine environments cover more than 50% of the Earth's surface and offer many opportunities for investigating the biological responses and adaptations of organisms to stressful life conditions. Extreme marine environments are sometimes associated with ephemeral and unstable ecosystems, but can host abundant, often endemic and well-adapted meiofaunal species. In this review, we present an integrated view of the biodiversity, ecology and physiological responses of marine meiofauna inhabiting several extreme marine environments (mangroves, submarine caves, Polar ecosystems, hypersaline areas, hypoxic/anoxic environments, hydrothermal vents, cold seeps, carcasses/sunken woods, deep-sea canyons, deep hypersaline anoxic basins [DHABs] and hadal zones). Foraminiferans, nematodes and copepods are abundant in almost all of these habitats and are dominant in deep-sea ecosystems. The presence and dominance of some other taxa that are normally less common may be typical of certain extreme conditions. Kinorhynchs are particularly well adapted to cold seeps and other environments that experience drastic changes in salinity, rotifers are well represented in polar ecosystems and loriciferans seem to be the only metazoan able to survive multiple stressors in DHABs. As well as natural processes, human activities may generate stressful conditions, including deoxygenation, acidification and rises in temperature. The behaviour and physiology of different meiofaunal taxa, such as some foraminiferans, nematode and copepod species, can provide vital information on how organisms may respond to these challenges and can provide a warning signal of anthropogenic impacts. From an evolutionary perspective, the discovery of new meiofauna taxa from extreme environments very often sheds light on phylogenetic relationships, while understanding how meiofaunal organisms are able to survive or even flourish in these conditions can explain evolutionary pathways. Finally, there are multiple potential economic benefits to be gained from ecological, biological, physiological and evolutionary studies of meiofauna in extreme environments. Despite all the advantages offered by meiofauna studies from extreme environments, there is still an urgent need to foster meiofauna research in terms of composition, ecology, biology and physiology focusing on extreme environments
Influence of strain origin on osmoregulatory and endocrine parameters of two non-native strains of Atlantic salmon (<i>Salmo salar</i> L.)
No full textNon-native strains of Atlantic salmon are used in reinstatement trials where populations are extinct. Environmental cues like photoperiod and temperature are known to influence the smolting process and there is evidence of strain-, stock- or population-specific differences associated with seaward migration or smoltification. The objective of this study was to compare morphological, osmoregulatory and endorcrine features between two strains, one originating from a cold and short river in Ireland (Cong) and another from a long and warm river in France (Loire-Allier), reared under Belgian conditions in order to highlight major differences in restocking adaptability. Comprehensive endocrine profiles, consistent with their interactive role of mediating changes associated with smolting, have been observed. Na+/K+ATPase activity (1.3–10.5 µmol ADP∗mg prot.−1∗h−1) and hormone plasma levels (e.g. 55–122 ng∗mL−1 of cortisol and 4.5–6.4 ng∗mL−1 of GH) were consistent with reported values. We observed strain-related differences of the influence of temperature and daylength on cortisol, GH and sodium plasma levels. These may be related to the respective environmental conditions prevailing in the river of origin, which have impacted the genetic background for smoltification. Using Na+/K+ATPase activity as an indicator, both strains smoltified successfully and simultaneously testifying a prevailing influence of environmental cues over genetic factors for smoltification
A review of the stable istotope bio-geochemistry of the global silicon cycle and its associated trace elements
Get PDFSilicon (Si) is the second most abundant element in the Earth's crust and is an important nutrient in the ocean. The global Si cycle plays a critical role in regulating primary productivity and carbon cycling on the continents and in the oceans. Development of the analytical tools used to study the sources, sinks, and fluxes of the global Si cycle (e.g., elemental and stable isotope ratio data for Ge, Si, Zn, etc.) have recently led to major advances in our understanding of the mechanisms and processes that constrain the cycling of Si in the modern environment and in the past. Here, we provide background on the geochemical tools that are available for studying the Si cycle and highlight our current understanding of the marine, freshwater and terrestrial systems. We place emphasis on the geochemistry (e.g., Al/Si, Ge/Si, Zn/Si, δ13C, δ15N, δ18O, δ30Si) of dissolved and biogenic Si, present case studies, such as the Silicic Acid Leakage Hypothesis, and discuss challenges associated with the development of these environmental proxies for the global Si cycle. We also discuss how each system within the global Si cycle might change over time (i.e., sources, sinks, and processes) and the potential technical and conceptual limitations that need to be considered for future studies
Natural chemicals produced by marine microalgae as predator deterrents can be used to control ciliates contamination in microalgal cultures
No full textLarge-scale production of microalgae for biofuels is often hampered by contamination of cultures with predators that feed on microalgae. An important group of predators are ciliates. Some species of marine microalgae in natural ecosystems are known to produce chemicals that act as deterrents against predators. In this study, we tested whether these chemicals (trans, trans-2,4-decadienal, dimethyl sulfoniopropionate (DMSP), glycine betaine and proline) as well as a chemical analogue (methyl 3-(methylthio) propionate or MMP) can be used to control contamination of cultures of the microalga Chlamydomonas by the predatory ciliate Sterkiella. All chemicals were capable of rapidly eradicating the ciliates from a contaminated Chlamydomonas culture, but at a higher dose also had a negative effect on the microalga. For each chemical an optimal dose was determined at which ciliates were controlled and losses in microalgal biomass productivity were minimized (0.13 mM decadienal, 4.75 mM DMSP, 10 mM MMP, 250-300 mM proline and 250-300 mM glycine betaine). In the case of DMSP, MMP and proline, biomass productivity was even the same as that of a non-contaminated culture. The chemicals were also effective against other ciliates (Stylonychia notophora, Oxytricha sp. and 2 different Paramecium species). These chemicals therefore have potential to be used as natural pesticides to control contamination of microalgal cultures by ciliates. Of all chemicals tested, DMSP and MMP are the most promising because they are effective at a relatively low dose and have a limited negative effect on microalgal productivity
