Biogeosciences discussions : (BGD)最新文献

{"title":"Fluorescent double labelling of F-actin in Foraminifera: evaluation of granular pattern F-actin organisation in reticulopodia","authors":"J. Goleń, J. Tyszka, Karolina Godos","doi":"10.5194/BG-2021-76","DOIUrl":"https://doi.org/10.5194/BG-2021-76","url":null,"abstract":"Abstract. This paper presents novel results of experiments focused on actin cytoskeleton organisation in pseudopodial structures of foraminifera. The main aim of this research was to test the hypotheses proposed to explain the previously reported granular pattern of F-actin labelling in several species of foraminifera with SiR-actin fluorescent probe. These hypotheses include the possibility that SiR-actin enhances the F-actin polymerisation or that it binds to other than F-actin compounds within foraminiferal cells, resulting in capturing the staining artefacts. The series of replicated experiments conducted on small miliolid Quinqueloculina sp. included double staining of F-actin with SiR-actin and phalloidin-based probes, complemented with observations of reticulopodia under the polarised light to identify the granules showing birefringence. All of performed experiments demonstrate highly congruent results expressed in SiR-actin and phalloidin co-labelling patterns, especially pronounced with the small granular objects (SiR-actin labelled granules or ALGs). Furthermore, the birefringence strongly tends to characterise primarily areas stained with both of the probes. These results rule out staining artefacts and support existence of actin cytoskeleton associated with micrometre-size motile granules. We discuss possible implications of this granular pattern that facilitates efficient formation and fast reorganization of extended granuloreticulopodia and other pseudopodial structures. If this is the case, they are one of the key evolutionary adaptations of these organisms that most likely predates the evolution of the foraminiferal tests that started in the early Palaeozoic.","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":" ","pages":"1-14"},"PeriodicalIF":0.0,"publicationDate":"2021-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44981034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geodiversity and biodiversity on a volcanic island: The role of scattered phonolites for plant diversity and reproductive fitness","authors":"David Kienle, Anna Walentowitz, Leyla Sungur, A. Chiarucci, S. D. Irl, A. Jentsch, Ole R. Veetas, Richard Field, C. Beierkuhnlein","doi":"10.5194/BG-2021-107","DOIUrl":"https://doi.org/10.5194/BG-2021-107","url":null,"abstract":"Abstract. Oceanic islands are cradles of endemism, contributing substantially to global biodiversity. A similarity in magmatic origin translates into high global comparability of substrates of volcanic islands on the oceanic crust. In some places, the petrography of magmatic rocks is differentiated chemically or physically. Phonolites are examples of rare localities with intermediate chemical traits between felsic and mafic and with diverse textures. They contribute to habitat heterogeneity and offer specific growth conditions in a significantly different matrix of basaltic substrates. The explicit contribution of geodiversity to island biodiversity has been little studied, despite accumulating evidence of its importance on continents. On the island of La Palma, Canary Islands, isolated phonolitic rocks are conspicuous by their light colour and specific shape. Although these outcrops only cover small areas, their unique form and composition increase within-island geodiversity. To investigate how this affects biodiversity on La Palma, we sampled all vascular plant species in 120 plots on four sets of paired sites, comparing phonolitic with basaltic rocks, to test whether phonolitic rocks increase overall plant species richness and promote the reproductive fitness of plants. We recorded species number and abundance, individual plant height, and diameter as proxies for aboveground resource allocation and tested for differences in vegetation cover and species composition between the bedrock types. We found higher species richness and abundance on phonolites than neighbouring basaltic substrates, and individuals of the same species were larger (in height and diameter) on phonolites compared to neighbouring basalt. An endemic woody species with two distinct varieties even appears almost exclusively on the small surfaces of phonolitic rock. Despite extremely limited spatial extent, phonolitic rocks can play an important role for plant biodiversity on islands.","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":" ","pages":"1-21"},"PeriodicalIF":0.0,"publicationDate":"2021-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47667910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Riverine nitrogen supply to the global ocean and its limited impact on global marine primary production: a feedback study using an Earth System Model","authors":"M. Tivig, D. Keller, A. Oschlies","doi":"10.5194/BG-2021-101","DOIUrl":"https://doi.org/10.5194/BG-2021-101","url":null,"abstract":"Abstract. A common notion is that negative feedbacks stabilize the marine nitrogen inventory. Recent modeling studies have shown, however, some potential for localized positive feedbacks leading to substantial nitrogen losses, in regions where nitrogen fixation and denitrification occur in proximity to each other. Here we include dissolved nitrogen from river discharge in a global 3-D ocean biogeochemistry model and study the effects on near-coastal and remote open ocean biogeochemistry. We find that at steady state the biogeochemical feedbacks in the marine nitrogen cycle, nitrogen input from biological N2 fixation, and nitrogen loss via denitrification, mostly compensate for the yearly addition of 22.8 to 45.6 Tg of riverine nitrogen and limit the impact on global marine productivity to < 2 %. Global experiments that regionally isolate river nutrient input show that sign and strength of the feedbacks depend on the location of the river discharge and the oxygen status of the receiving marine environment. Marine productivity generally increases in proximity to the nitrogen input, but we also find a decline in productivity in the Bay of Bengal and near the mouth of the Amazon River. While most of the changes are located in shelf and near coastal oceans, nitrogen supply from the rivers can impact the open ocean, due to feedbacks or knock-on effects.\u0000","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":" ","pages":"1-31"},"PeriodicalIF":0.0,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47162372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Bouraké semi-enclosed lagoon (New Caledonia). A natural laboratory to study the life-long adaptation of a coral reef ecosystem to climate change-like conditions","authors":"F. Maggioni, M. Pujo-Pay, J. Aucan, C. Cerrano, B. Calcinai, C. Payri, F. Benzoni, Y. Letourneur, R. Rodolfo-Metalpa","doi":"10.5194/BG-2021-90","DOIUrl":"https://doi.org/10.5194/BG-2021-90","url":null,"abstract":"Abstract. According to current experimental evidence, coral reefs could disappear within the century if CO2 emissions remain unabated. However, recent discoveries of diverse and high cover reefs that already thrive under extreme conditions seem to contradict these projections. Volcanic CO2 vents, semi-enclosed lagoons and mangrove estuaries are unique study sites where one or more ecologically relevant parameters for life in the oceans are close or even worse than currently projected for the year 2100. These natural analogues of future conditions hold new hope for the future of coral reefs and provide unique natural laboratories to explore how reef species could keep pace with climate change. To achieve this, it is essential to characterize their environment as a whole, and accurately consider all possible environmental factors that may differ from what is expected in the future and that may possibly alter the ecosystem response. In this study, we focus on the semi-enclosed lagoon of Bouraké (New Caledonia, SW Pacific Ocean) where a healthy reef ecosystem thrives in warm, acidified and deoxygenated water. We used a multi-scale approach to characterize the main physical-chemical parameters and mapped the benthic community composition (i.e., corals, sponges, and macroalgae). The data revealed that most physical and chemical parameters are regulated by the tide, strongly fluctuate 3 to 4 times a day, and are entirely predictable. The seawater pH and dissolved oxygen decrease during falling tide and reach extreme low values at low tide (7.2 pHT and 1.9 mg O2 L−1 at Bouraké, vs 7.9 pHT and 5.5 mg O2 L−1 at reference reefs). Dissolved oxygen, temperature, and pH fluctuates according to the tide of up to 4.91 mg O2 L−1, 6.50 °C, and 0.69 pHT units on a single day. Furthermore, the concentration of most of the chemical parameters was one- to 5-times higher at the Bouraké lagoon, particularly for organic and inorganic carbon and nitrogen, but also for some nutrients, notably silicates. Surprisingly, despite extreme environmental conditions and altered seawater chemical composition, our results reveal a diverse and high cover community of macroalgae, sponges and corals accounting for 28, 11 and 66 species, respectively. Both environmental variability and nutrient imbalance might contribute to their survival under such extreme environmental conditions. We describe the natural dynamics of the Bouraké ecosystem and its relevance as a natural laboratory to investigate the benthic organism’s adaptive responses to multiple stressors like future climate change conditions.\u0000","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":"1 1","pages":"1-42"},"PeriodicalIF":0.0,"publicationDate":"2021-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42491534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical consequences of oxygen diffusion from the oceanic crust into overlying sediments and its significance for biogeochemical cycles based on sediments of the NE Pacific","authors":"G. Versteegh, A. Koschinsky, T. Kuhn, I. Preuss, S. Kasten","doi":"10.5194/BG-2021-112","DOIUrl":"https://doi.org/10.5194/BG-2021-112","url":null,"abstract":"Abstract. Exchange of dissolved substances at the sediment–water interface provides an important link between the short–term and long–term geochemical cycles in the ocean. A second, as yet poorly understood sediment–water exchange is supported by low–temperature circulation of seawater through the oceanic basement underneath the sediments. From the basement, upwards diffusing oxygen and other dissolved species modify the sediment whereas reaction products diffuse from the sediment down into the basement, where they are transported by the basement fluid and released to the ocean. Here, we investigate the impact of this “second” route with respect to transport, release and consumption of oxygen, nitrate, manganese, nickel, and cobalt on the basis of sediment cores retrieved from the Clarion Clipperton Zone (CCZ) in the equatorial Pacific Ocean. We show that in this abyssal ocean region characterised by low organic–carbon burial and sedimentation rates vast areas exist where the downward and upward directed diffusive fluxes of oxygen meet so that the sediments are oxic throughout. This is especially the case where sediments are thin or in the proximity of faults. Oxygen diffusing upward from the basaltic crust into the sediment contributes to the degradation of sedimentary organic matter. Where the oxygen profiles do not meet, they are separated by a suboxic sediment interval characterised by Mn2+ in the pore–water. Where the sediments are entirely oxic, nitrate produced in the upper sediment by nitrification is lost both by upward diffusion into the bottom water and by downward diffusion into the fluids circulating within the basement. Where pore–water manganese in the suboxic zones remains low, nitrate consumption is low and the sediment continues to deliver nitrate to the ocean bottom waters and basement fluid. We observe that at elevated pore–water manganese concentrations, nitrate consumption exceeds production and the basement becomes a nitrate source. Within the suboxic zone, not only manganese but also cobalt and nickel are released into the pore–water by reduction of oxides, diffuse towards the oxic/suboxic fronts above and below where they precipitate, effectively removing these metals from the suboxic zone and concentrating them at the oxic/suboxic redox boundaries. We show that not only diffusive fluxes in the top part of deep–sea sediments modify the geochemical composition over time, but also diffusive fluxes of dissolved constituents from the basement into the bottom layers of the sediment. Hence, paleoceanographic interpretation of sedimentary layers should carefully consider such deep secondary modifications in order to prevent misinterpretation as primary signatures.\u0000","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":"1 1","pages":"1-34"},"PeriodicalIF":0.0,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43070868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights into nitrogen fixation below the euphotic zone: trials in an oligotrophic marginal sea and global compilation","authors":"Siqi Wu, Moge Du, X. Wan, C. Selden, M. Benavides, S. Bonnet, Robert Hamersley, C. Löscher, M. Mulholland, Xiuli Yan, S. Kao","doi":"10.5194/BG-2021-104","DOIUrl":"https://doi.org/10.5194/BG-2021-104","url":null,"abstract":"Abstract. Nitrogen (N2) fixation, the energetically expensive conversion of N2 to ammonia, plays an important role in balancing the global nitrogen budget. Defying historic paradigms, recent studies have detected non-cyanobacterial N2 fixation in deep, dark oceanic waters. Even low volumetric rates can be significant considering the large volume of these waters. However, measuring aphotic N2 fixation is an analytical challenge due to the low particulate nitrogen (PN) concentrations. Here, we investigated N2 fixation rates in aphotic waters in the South China Sea (SCS). To increase the sensitivity of N2 fixation rate measurements, we applied a novel approach requiring only 0.28 μg N for measuring the isotopic composition of particulate nitrogen. We conducted parallel 15N2-enriched incubations in ambient seawater, seawater amended with amino acids and poisoned (HgCl2) controls, along with incubations that received no tracer additions to distinguish biological N2 fixation. Experimental treatments differed significantly from our two types of controls, those receiving no additions and killed controls. Amino acid additions masked N2 fixation signals due to the uptake of added 14N-amino acid. Results show that the maximum dark N2 fixation rates (1.28 ± 0.85 nmol N L−1 d−1) occurred within upper 200 m, while rates below 200 m were mostly lower than 0.1 nmol N L−1 d−1. Nevertheless, N2 fixation rates between 200 and 1000 m accounted for 39 ± 32 % of depth-integrated dark N2 fixation rates in the upper 1000 m, which is comparable to the areal nitrogen inputs via atmospheric deposition. Globally, we found that aphotic N2 fixation studies conducted in oxygenated environments yielded rates similar to those from the SCS (< 1 nmol N L−1 d−1), regardless of methods, while higher rates were occasionally observed in low-oxygen (< 62 µM) regions. Regression analysis suggests that particulate nitrogen concentrations could be a predictive proxy for detectable aphotic N2 fixation in the SCS and eastern tropical south Pacific. Our results provide the first insight into aphotic N2 fixation in SCS and support the importance of the aphotic zone as a globally-important source of new nitrogen to the ocean.\u0000","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":"1 1","pages":"1-31"},"PeriodicalIF":0.0,"publicationDate":"2021-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41689715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Supplementary material to \"Unravelling Light and Microbial Activity as Drivers of Organic Matter Transformations in Tropical Headwater Rivers\"","authors":"James F. Spray, T. Wagner, J. Bischoff, S. Trojahn, S. Norouzi, W. Hill, Julia Brasche, Leroy James, R. Pereira","doi":"10.5194/BG-2021-92","DOIUrl":"https://doi.org/10.5194/BG-2021-92","url":null,"abstract":"Abstract. Connecting tropical rainforests to larger rivers, tropical headwaters export large quantities of carbon and nutrients as dissolved organic matter (DOM), and are thus a key component of the global carbon cycle. This DOM transport is not passive, however; sunlight and microbial activity alter DOM concentrations and compositions, affecting riverine greenhouse gas emissions and downstream ecosystems. The effects of sunlight and microbial turnover/activity on DOM concentrations and compositions in tropical headwaters are currently poorly understood, but novel Size Exclusion Chromatography (SEC) techniques coupled to suitable detectors can for the first time quantify their influences. Here, we present in-situ incubation experiments from from headwaters of the Essequibo River, in the Iwokrama Rainforest, Guyana, where sunlight oxidised up to 9% of dissolved organic carbon (DOC) over 12 hours, at higher rates than in larger tropical rivers. DOM transformations occurred in both photo-sensitive and supposedly photo-resistant pools. Microbial activity had varying, less clear influences on DOC concentrations over the same time span; compositionally, this appeared to extend beyond known bio-labile components. Biopolymers were particularly reactive to both processes. We show sunlight has the greater potential to mineralise headwater DOM and thus potentially influence degassing. Our approach provides a future template to constrain DOM transformations along river networks, identify biogeochemical activity hotspots, and improve greenhouse gas emissions estimations under changing environmental conditions.\u0000","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":" ","pages":"1-26"},"PeriodicalIF":0.0,"publicationDate":"2021-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47839598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reviews and syntheses: Enhancing research and monitoring of land-to-atmosphere greenhouse gases exchange in developing countries","authors":"Dong-Gill Kim, B. Bond‐Lamberty, Y. Ryu, B. Seo, D. Papale","doi":"10.5194/BG-2021-85","DOIUrl":"https://doi.org/10.5194/BG-2021-85","url":null,"abstract":"Abstract. Greenhouse gas (GHG) research has traditionally required data collection and analysis using advanced and often expensive instruments, complex and proprietary software, and skilled technicians. Partly as a result, relatively little GHG research has been conducted in resource-constrained developing countries and a critical data gap exists in these regions. At the same time, these are the same countries and regions in which climate-change impacts will likely be strongest, and in which major science uncertainties are centered, given the importance of dryland and tropical systems to the global carbon cycle and climate. Increasingly, scientific communities have adopted appropriate technology and approach (ATA these can often be mitigated by carefully designing experimental set-up, providing clear protocols for data collection, and monitoring and validating the quality of obtained data. For implementing this approach in GHG research of developing countries, first, it is necessary to recognize the scientific and moral importance of AT&A. At the same time, new AT&A techniques should be identified and further developed. Finally, these processes should be promoted through training local staff and encouraged for wide use and further innovation in developing countries.","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":" ","pages":"1-30"},"PeriodicalIF":0.0,"publicationDate":"2021-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44630005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biological pumps of carbon, nitrogen, and phosphorus in the northern South China Sea","authors":"J. Hung, C. Tung, Zong-Ying Lin, Y. Chen, Shao-Hung Peng, Yen-Huei Lin, L. Tsai","doi":"10.5194/BG-2021-17","DOIUrl":"https://doi.org/10.5194/BG-2021-17","url":null,"abstract":"Abstract. This paper presents the measured biological pumps (BPs) of carbon (C), nitrogen (N), and phosphorus (P) and their response to seasonal and event-driven oceanographic changes in the northern South China Sea (NSCS). The BP is defined as the sum of active and passive fluxes of biogenic carbon in the surface layer, which may be considered as the central part of marine carbon cycle. These active and passive fluxes of N and P were also considered to understand stoichiometric flux patterns and the roles of nutrients involved in the BP. The magnitudes of total C, N, and P fluxes were respectively estimated to be 71.9–347 (mean: 163) mg C m−2 d−1, 13.0–30.5 (mean: 21.6) mg N m−2 d−1, and 1.02–2.97 (mean: 1.94) mg P m−2 d−1, which were higher than most previously reported BPs in open oceans, likely because a quarter of the BPs was contributed from active fluxes that were unaccounted for in BPs previously. Moreover, the passive fluxes dominated the BPs and were estimated as 65.3–255 (mean: 125) mg C m−2 d−1 (76.7 % of total C flux), 11.9–23.2 (mean: 17.6) mg N m−2 d−1 (83.0 % of total N flux), and 0.89–1.98 (mean: 1.44) mg P m−2 d−1 (74.2 % of total P flux). Vertical fluxes of dissolved organic C, N, and P generally contributed to less than 5 % of passive fluxes. The contrasting patterns of active and passive fluxes found between summer and winter could mainly be attributed to surface warming and stratification in summer and cooling and wind-induced turbulence for pumping nutrients into the euphotic zone in winter. In addition to seasonal variations, the impacts of anticyclonic eddies and internal-wave events on BP enhancement was apparent in the NSCS. Both active and passive fluxes were likely driven by nutrient availability within the euphotic zone, which was ultimately controlled by the changes in internal and external forcings. The nutrient availability also determined the inventory of chlorophyll a and new production, thereby allowing the prediction of active and passive fluxes for unmeasured events. To a first approximation, the SCS may effectively transfer 0.208 Gt C yr−1 into the ocean's interior, accounting for approximately 1.89 % of the global C flux. The internal forcing and climatic conditions are likely critical factors in determining the seasonal and event-driven variability of BP in the NSCS.","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":"1 1","pages":"1-47"},"PeriodicalIF":0.0,"publicationDate":"2021-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46806578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of the natural background of phosphorus in the Scheldt river using tidal marsh sediment cores","authors":"Florian Lauryssen, P. Crombé, T. Maris, Elliot Van Maldegem, Marijn Van de Broek, S. Temmerman, E. Smolders","doi":"10.5194/BG-2021-100","DOIUrl":"https://doi.org/10.5194/BG-2021-100","url":null,"abstract":"Abstract. Elevated phosphate (PO4) concentrations can harm the ecological status in water by eutrophication. In the majority of surface waters in lowland regions such as Flanders (Belgium), the local PO4 levels exceed the limits defined by environmental policy and fail to decrease, despite decreasing total phosphorus (P) emissions. In order to underpin the definition of currents limits, this study was set up to identify the pre-industrial background PO4 concentration in surface water of the Scheldt river, a tidal river in Flanders. We used the sedimentary records preserved in tidal marsh sediment cores as an archive for reconstructing historical changes in surface water PO4. For sediment samples at different depths below the sediment surface, we dated the time of sediment deposition and analysed the extractable sediment-P. The resulting time series of sediment-P was linked to time series of measured surface water PO4 concentrations (data 1967–present). By combining the sediment-P and water-PO4 data, the sorption characteristics of the sediment could be described. Those sorption characteristics allowed us to estimate a pre-industrial background surface water PO4 levels, based on deeper sediment-P that stabilised at concentrations smaller than the modern. In three out of the four cores, the sediment-P peaked around 1980, coinciding with the peak in surface water PO4. The estimated pre-industrial (~1800) background PO4-concentration in the Scheldt river water was 62 [57; 66 (95 %CI)] µg PO4-P/L. That concentration exceeds the previously estimated natural background values for lakes in Flanders (15–35 µg TP/L) and is about half of the prevailing limit in the Scheldt river (120 µg PO4-P/L). In the 1930s, river water concentrations were estimated at 140 [128; 148] µg PO4-P/L, already exceeding the current limit. The method developed here proved useful for reconstructing historical, background PO4 concentrations of a lowland tidal river. A similar approach can apply to other lowland tidal rivers to provide a scientific basis for local, catchment specific PO4 backgrounds.","PeriodicalId":89897,"journal":{"name":"Biogeosciences discussions : (BGD)","volume":" ","pages":"1-21"},"PeriodicalIF":0.0,"publicationDate":"2021-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48529169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}