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Dubbele dijken als robuuste waterkerende landschappen voor een welvarende Zuidwestelijke Delta. NIOZ Report 2021-01
No full textKlimaatopwarming en zeespiegelverandering dwingen ons om de aanpak met betrekking tot waterveiligheid tegen het licht te houden en zelfs te heroverwegen. De huidige Nederlandse aanpak waarbij dijken steeds hoger en breder worden zorgt op termijn voor problemen. Door voortgaande bodemdaling nemen op termijn de kosten toe om waterkeringen stabiel te houden en verzilting tegen te gaan. In dit rapport onderzoeken we de kansen voor implementatie van dubbele dijken met een wisselpolder als alternatief voor de huidige aanpak. Bij een dubbele dijk wordt een dijk landwaarts van de zeewaartse dijk aangelegd, of een bestaande slaperdijk opgewaardeerd. Tevens wordt een doorlaat in de zeewaartse dijk gemaakt zodat de tussenliggende wisselpolder door getijden overstroomd en op kan slibben. Doordat de bodemhoogte toeneemt worden de dijken stabieler en hoeven minder opgehoogd te worden, wat kosten kan besparen. De wisselpolder kan baten leveren wanneer deze voor aquacultuur en zilte teelt of voor natuurontwikkeling, waar recreatie en toerisme van kunnen profiteren, gebruikt wordt. Wanneer de bodem op hoogte is kan de doorlaat afgesloten worden om de wisselpolder weer voor landbouw in gebruik te nemen. In deze studie werken we het concept van dubbele dijken met wisselpolder in meer detail uit. We voeren een kosten-batenanalyse en economische effectrapportage van een estuarium brede implementatie in de Zuidwestelijke Delta uit, langs de oevers van de Westerschelde, Oosterschelde en het Haringvliet. Daarbij maken we gebruik van een model welke de bodemhoogte in de wisselpolders berekend en de daaraan gekoppelde baten m.b.t. aquacultuur, zilte teelt en natuur. We vergelijken de dubbelde dijken met zowel de conventionele dijkophoging ('business as usual') als ook een alternatief met overslagbestendige dijken. Uit deze analyse blijkt dat dubbele dijken met wisselpolders op alle fronten goed scoort ten opzichte van de conventionele aanpak. Ondanks de hoogste implementatiekosten is het investeringsrendement hoog en voegt het nieuwe economische en natuurlijke functies toe aan het landschap, waardoor een no-regret investering ontstaat. Tijdige implementatie is echter essentieel voor het succes ervan, omdat door zeespiegelstijging de bodemophoging achter kan blijven. Wanneer de bodem in de wisselpolders tussen de dubbele dijken relatief laag blijft, heeft dat niet direct gevolgen voor de waterkerende werking. Wel zal de mogelijkheid om de polder weer in gebruik te nemen voor landbouw uitblijven en zal de stabilisatie minder zijn. Daar staat tegenover dat de wisselpolders langer voor aquacultuur geschikt blijven, welke een sterk alternatief voor landbouw zijn. Concluderend zijn dubbele dijken met wisselpolders een betaalbaar alternatief en zorgen ze voor een veilig en robuust waterkerend landschap met meerwaarde voor de regionale economie en natuur
High-resolution current meter and hydrographic data from the Irminger Current mooring array 2016 - 2018
No full textThe Irminger Currrent mooring array consists of 5 subsurface ocean moorings in the Irminger Current on the Reykjanes Ridge in the North Atlantic Ocean. The third high-resolution data set of oceanographic variables from instrumentation on these moorings was collected from 6 August 2016 to 19 July 2018. The moorings are named IC0, IC1, IC2, IC3 and IC4 going from west to east.
The Irminger Current mooring array is part of the international Overturning of the Subpolar North Atlantic Program (OSNAP, www.o-snap.org) which runs from 2014 to at least 2022. The data set consists ocean temperature, salinity, current velocities, pressure and time. Variables were collected at different time intervals, varying from 5 minutes to 1 hour. The data have been calibrated and quality controlled. The data and the metadata are stored in NetCDF files following the Climate Forecast (CF) conventions, see http://cfconventions.or
High-resolution current meter and hydrographic data from the Irminger Current mooring array 2014-2015
No full textThe Irminger Current mooring array consists of 5 subsurface ocean moorings in the Irminger Current on the Reykjanes Ridge in the North Atlantic Ocean. The second high-resolution data set of oceanographic variables from instrumentation on these moorings was collected from 11 July 2014 to 10 July 2015. The moorings are named IC0, IC1, IC2, IC3, and IC4 going from west to east. The Irminger Current mooring array is part of the international Overturning of the Subpolar North Atlantic Program (OSNAP, www.o-snap.org) which runs from 2014 to at least 2018. The data set consists ocean temperature, salinity, current velocities, pressure and time. Variables were collected at different time intervals, varying from 5 minutes to 1 hour. The data have been calibrated and quality controlled. The data and metadata are stored in NetCDF files following the Climate Forecast (CF) conventions, see http://cfconventions.or
Central-West Siberian-breeding Bar-tailed Godwits Limosa lapponica segregate in two morphologically distinct flyway populations
No full textLong-distance migratory species often include multiple breeding populations, with distinct migration routes, wintering areas and annual-cycle timing. Detailed knowledge on population structure and migratory connectivity provides the basis for studies on the evolution of migration strategies and for species conservation. Currently, five subspecies of Bar-tailed Godwits Limosa lapponica have been described. However, with two apparently isolated breeding and wintering areas, the taxonomic status of the subspecies L. l. taymyrensis remains unclear. Here we compare taymyrensis Bar-tailed Godwits wintering in respectively the Middle East and West Africa, with respect to migration behaviour, breeding area, morphology and population genetic differentation in mitochondrial DNA. By tracking 52 individuals from wintering and staging areas over multiple years, we show that Bar-tailed Godwits wintering in the Middle East bred on the northern West-Siberian Plain (n = 19), whilst birds from West Africa bred further east, mostly on the Taimyr Peninsula (n = 12). The two groups differed significantly in body size and shape, and also in the timing of both northward and southward migrations. However, they were not genetically differentiated, indicating that the phenotypic (i.e. geographic, morphological and phenological) differences arose either very recently or without current reproductive isolation. We conclude that the taymyrensis taxon consists of two distinct populations with mostly non-overlapping flyways, which warrant treatment as separate taxonomic units. We thus propose to distinguish a more narrowly defined taymyrensis subspecies (i.e. the Bar-tailed Godwits wintering in West Africa and breeding on Taimyr), from a new subspecies (i.e. the birds wintering in the Middle East and breeding on the northern West-Siberian Plain)
Seawater hydrography and biogeochemistry data from Luymes Bank Sinkhole Expedition 64PE20191205
No full textThese datasets contain the measurements from discrete bottle samples and CTD sensors during cruise 64PE465/64PE20191205 on RV Pelagia in the Caribbean Netherlands (Luymes Bank Sinkhole Expedition, 5-18 December 2019). The cruise report is included for reference
Counting using deep learning regression gives value to ecological surveys.
No full textMany ecological studies rely on count data and involve manual counting of objects of interest, which is time-consuming and especially disadvantageous when time in the field or lab is limited. However, an increasing number of works uses digital imagery, which opens opportunities to automatise counting tasks. In this study, we use machine learning to automate counting objects of interest without the need to label individual objects. By leveraging already existing image-level annotations, this approach can also give value to historical data that were collected and annotated over longer time series (typical for many ecological studies), without the aim of deep learning applications. We demonstrate deep learning regression on two fundamentally different counting tasks: (i) daily growth rings from microscopic images of fish otolith (i.e., hearing stone) and (ii) hauled out seals from highly variable aerial imagery. In the otolith images, our deep learning-based regressor yields an RMSE of 3.40 day-rings and an R^2 of 0.92. Initial performance in the seal images is lower (RMSE of 23.46 seals and R^2 of 0.72), which can be attributed to a lack of images with a high number of seals in the initial training set, compared to the test set. We then show how to improve performance substantially (RMSE of 19.03 seals and R^2 of 0.77) by carefully selecting and relabelling just 100 additional training images based on initial model prediction discrepancy. The regression-based approach used here returns accurate counts (R^2 of 0.92 and 0.77 for the rings and seals, respectively), directly usable in ecological research
Co-evolution of the terrestrial and aquatic ecosystem in the Holocene Baltic Sea
No full textThe Baltic Sea experienced changes in marine input throughout the Holocene as substantial regional ice retreat led to isostatic adjustment, eustatic sea level change, and periodic isolation from the North Sea. Here, we determine the distributions and isotopic signatures of organic compounds preserved in a sediment record spanning the last ~ 11 ka to reconstruct environmental change under these dynamic conditions. Carbon and hydrogen isotope ratios of short-, mid-, and long-chain n-alkanes, along with long-chain diol and glycerol dialkyl glycerol tetraether abundances, were analyzed in sediments sampled from the Arkona Basin in the southwestern Baltic Sea. In the earlier part of the record (specifically 10 ? 8.2 ka), hydrogen isotope values of higher plant-derived n-alkanes revealed a change in dominant water source from an ice melt-derived to a precipitation-dominated hydrological regime. Following this shift in water source, carbon isotope values of n-alkanes suggest diversification of vegetation. Shifts in hydrology and vegetation did not coincide with established phase boundaries, but instead occurred mid-phase or spanned phase transitions. For this reason, we suggest describing the Ancylus Lake in two phases: a meltwater phase (10.6 to 9.2 ka) and a precipitation phase (9.2 to 7.7 ka). Our results highlight the utility of using C and H isotope ratios in conjunction with other compound abundance proxies to better understand the complex environmental change recorded in paleo archives
NIOZ jetty hourly data for temperature and salinity for 2012
No full textNIOZ jetty LON=4.789E LAT=53.002N, using EXO sensor at depth of -1.5 meter NAP. Derived product from 10 second calibrated data. Separate calibration measurement at 2 week intervals
Underway surface seawater high-resolution pH time series for R/V Sonne cruise SO279.
No full textThis dataset contains a high-resolution (1 measurement every 30 seconds) time series of surface ocean pH in the Azores Region (North Atlantic Ocean) measured with a PyroScience fiber-based pH sensor (PHROBSC-PK8T) and cross-calibrated using discrete carbonate system observations (total alkalinity, dissolved inorganic carbon and nutrients). The measurements were collected during R/V Sonne cruise SO279 in Dec 2020, as part of the NAPTRAM research programme to build an understanding of the transport pathways of plastic and microplastic debris in the North Atlantic. Bad results from technical issues during analysis have been removed from these results, so there are no recognised issues. The data were collected as part of an international effort from the JPI Oceans project HOTMIC and BMBF project PLASTISEA , and forms a joint effort of HOTMIC and PLASTISEA researchers from a range of countries and institutes. The NIOZ created the metadata entry and is responsible for holding master copies of the data
Algal-Induced Biogeomorphic Feedbacks Lay the Groundwork for Coastal Wetland Development
No full textEcosystem establishment under adverse geophysical conditions is often studied within the "windows of opportunity" framework, identifying disturbance-free periods (e.g., calm wave climate) where species can overcome establishment thresholds. However, the role of biogeophysical interactions in this framework is less well understood. The establishment of saltmarsh vegetation on tidal flats, for example, is limited by abiotic factors such as hydrodynamics, sediment stability and drainage. On tidal flats, raised sediment ridges colonized by algal mats (Vaucheria sp.) appear to accomodate high densities of plant seedlings. Such ridges were previously found to have higher sediment strength than substratum without algae. Here, we investigate whether these measurements can be explained by geophysical factors only, or that biological (Vaucheria-induced) processes influence tidal marsh establishment by forming stabilized bedforms. We performed two experiments under controlled mesocosm conditions, to test the hypotheses that i) Vaucheria grows better on elevated topographic relief, that ii) the binding force of their algal filaments increases sediment strength, and that iii) Vaucheria consequently creates elevated topographic relief that further facilitates algal growth. Our experimental results confirm the existence of this algal-induced biogeomorphic feedback cycle. These findings imply that benthic algae like Vaucheria may contribute significantly to tidal marsh formation by creating elevated and stabilized substratum. This suggests biogeophysical feedbacks can "widen" the windows of opportunity for further ecosystem establishment. Our results could be useful for the design of managed realignment projects aimed at restoring the unique ecosystem services of coastal wetlands, such as habitat biodiversity, carbon sequestration potential and nature-based flood defense