scholarly journals Bioturbation, ecosystem functioning and community structure

2002 ◽  
Vol 6 (6) ◽  
pp. 999-1005 ◽  
Author(s):  
C. L. Biles ◽  
D. M. Paterson ◽  
R. B. Ford ◽  
M. Solan ◽  
D. G. Raffaelli
Keyword(s):  
Community Structure ◽  
Water Column ◽  
Ecosystem Functioning ◽  
Nutrient Concentration ◽  
Nutrient Release ◽  
Nutrient Concentrations ◽  
Infaunal Community ◽  
Significant Difference ◽  
In Situ Experiments

Abstract. The effect of community structure on the functioning of the ecosystem is an important issue in ecology due to continuing global species loss. The influence of infaunal community structure on the functioning of marine systems is proposed here to act primarily through bioturbation of the sediment. Nutrient concentration in the water column, generated by release from the sediment, was used as a measure of ecosystem functioning. In situ and laboratory experiments showed a significant difference in nutrient concentrations with different species treatments. Bioturbation profiles showing the incorporation of tracer particles also differed between communities with different dominant species. The behavioural differences between infaunal species, generating different modes and rates of bioturbation, are therefore proposed to influence nutrient release. The presence and quantity of bioturbating infauna also influenced the amount of sediment suspended in the water column. The increase in surface area available for microbial activity may generate an increase in nutrient cycling. Abiotic influences on sediment structure, such as flow, may have a similar effect on nutrient concentration. Annular flumes used in both laboratory and in situ experiments to generate flow conditions produced a significant increase in ammonia (NH4-N) production in macrofaunal treatments. Flow may influence the behaviour of macrofaunal species, causing changes in NH4-N production through modifying bioturbation of the sediment. Keywords: bioturbation, community structure, ccosystem functioning, estuaries, flow, infauna

Application of Gypsum Granule as a Capping Material to Reduce Phosphorus Release from Sediment of Lake Paldang

2007 ◽  
Vol 544-545 ◽  
pp. 521-524 ◽  
Author(s):  
Yong Jin Park ◽  
Jae Jung Ko ◽  
Young Im Kim ◽  
Sang Leen Yun ◽  
So Jung Kim ◽  
...  
Keyword(s):  
Water Column ◽  
Chlorophyll A ◽  
Nutrient Concentration ◽  
Phosphorus Release ◽  
Experimental Results ◽  
Chlorophyll A Concentration ◽  
P Concentration ◽  
In Situ Experiments ◽  
Calcium Cation

In this study, the capping effects of granular gypsum (Ca2SO4·2H2O) and sand on sediment and water column were evaluated in in-situ experiments in Lake Paldang. The results indicate that capping treatment is very effective for the restoration of eutrophied lake. It was demonstrated that phosphorus, T-N and T-P concentration in the water column of treated basin was relatively lower than control basin. As a consequence of reduction of nutrient concentration by capping treatment, chlorophyll-a concentration in treated basin was considerably lower than control basin. The chlorophyll-a concentration in water column could be reduced to 52% and 25% as compared to control basin, respectively, by the capping treatment with gypsum and sand. From the experimental results, it was concluded that gypsum was more effective capping material than sand for controlling of nutrients and chlorophyll-a. In addition, capping with gypsum bring calcium cation into sediment, which offer more site for phosphorus to bind. In case of the capping with gypsum, apatite P composition, mainly consist of Ca boun P, in the sediment increased from 24% to 43% for the two month of operation.

scholarly journals Advanced experimental approaches to marine water-column biogeochemical processes

2017 ◽  
Vol 75 (1) ◽  
pp. 30-42 ◽  
Author(s):  
Louis Legendre ◽  
Richard B Rivkin ◽  
Nianzhi Jiao
Keyword(s):  
Water Column ◽  
Numerical Models ◽  
Free Water ◽  
Sea Surface ◽  
Biogeochemical Processes ◽  
In Situ Experiments ◽  
Technological Developments ◽  
Approaches To Study ◽  
Experimental Approaches

Abstract This “Food for Thought” article examines the potential uses of several novel scientific and technological developments, which are currently available or being developed, to significantly advance or supplement existing experimental approaches to study water-column biogeochemical processes (WCB-processes). After examining the complementary roles of observation, experiments and numerical models to study WCB-processes, we focus on the main experimental approaches of free-water in situ experiments, and at-sea and on-land meso- and macrocosms. We identify some of the incompletely resolved aspects of marine WCB-processes, and explore advanced experimental approaches that could be used to reduce their uncertainties. We examine three such approaches: free-water experiments of lengthened duration using bioArgo floats and gliders, at-sea mesocosms deployed several 100s m below the sea-surface using new biogeochemical sensors, and 50 m-tall on-land macrocosms. These approaches could lead to significant progress in concepts related to marine WCB-processes.

scholarly journals Seasonal dynamics of Daphnia laevisBirge, 1878 ephippia in a tropical lake with a description of a new methodology for in situ evaluation

2014 ◽  
Vol 74 (3) ◽  
pp. 642-648 ◽  
Author(s):  
LPM Brandão ◽  
DGF Pujoni ◽  
PM Maia-Barbosa
Keyword(s):  
Water Column ◽  
Seasonal Dynamics ◽  
Thermal Stratification ◽  
Core Sample ◽  
Hatching Rate ◽  
The Core ◽  
Significant Difference ◽  
Chi Squared ◽  
Hatching Rates

The effect of dormancy in zooplankton populations is still unknown, largely because of the lack of methods to estimate hatching and production of the dormant stages. This study aimed to compare the production and hatching rates of ephippia of Daphnia laevis between thermal stratification and mixing periods in Jacaré Lake (Middle Rio Doce, Minas Gerais, Brazil). For this, we collected ephippia on the sediment with core sampler and we created a device called the “Ephippial Collector”. There was a significant difference in ephippia hatching in situ between stratification and mixing periods (Pearson's Chi-squared test p <0.001), being higher in the second one. Significant differences in the hatching rates between periods was observed in the laboratory only for ephippia collected with Ephippial Collectors (Pearson's Chi-squared test p <0.001), being higher during the mixing period (∼8%). The core sample allows the collection of a certain fraction of the sediment that may contain a mixture of ephippia produced in different periods, i.e., may contain old and not viable ephippia, which masks the hatching rate. Thus, seasonality in hatching rates of ephippia was reported only by Ephippial Collectors. The higher hatching rate observed during the mixing period in the lake suggests that individuals hatched from ephippia may contribute to the increase in the population of D. laevis in the water column at this time.

In-situ investigation of alkalinity - denitrification coupling in the sediment - water column interface

2020 ◽  
Author(s):  
Mona Norbisrath
Keyword(s):  
Water Column ◽  
German Bight ◽  
Anthropogenic Impacts ◽  
Binding Capacity ◽  
Quantitative Relationship ◽  
Terminal Electron Acceptor ◽  
The North ◽  
In Situ Investigation ◽  
In Situ Experiments

&lt;p&gt;&lt;strong&gt;Abstract: EGU 2020&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Session: BG4.1: Biogeochemistry of coastal seas and continental shelves (Helmuth Thomas)&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Mona Norbisrath&lt;sup&gt;1&lt;/sup&gt;, Kirstin D&amp;#228;hnke&lt;sup&gt;1&lt;/sup&gt;, Andreas Neumann&lt;sup&gt;1&lt;/sup&gt;, Justus van Beusekom&lt;sup&gt;1&lt;/sup&gt;, Nele Treblin&lt;sup&gt;1&lt;/sup&gt;, Bryce van Dam&lt;sup&gt;1&lt;/sup&gt;, Helmuth Thomas&lt;sup&gt;1&lt;/sup&gt;&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1&lt;/sup&gt;Institute for Coastal Research, Helmholtz-Zentrum Geesthacht&lt;/p&gt;&lt;p&gt;Contact: [email protected]&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;In-situ investigation of alkalinity - denitrification coupling in the sediment - water column interface&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;As a shallow shelf sea, the North Sea is very vulnerable to anthropogenic impacts like rising CO&lt;sub&gt;2&lt;/sub&gt; concentrations, increasing nutrient inflows and coincident oxygen loss.&lt;/p&gt;&lt;p&gt;Two important processes that determine the role of the coastal ocean as a net sink for anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; are alkalinity and denitrification. Alkalinity, the acid binding capacity of the ocean, buffers natural and anthropogenic changes in the oceans&amp;#8217; CO&lt;sub&gt;2&lt;/sub&gt; and pH system. Denitrification, an anaerobic microbial process in which organic matter is respired, uses NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; instead of O&lt;sub&gt;2&lt;/sub&gt; as a terminal electron acceptor. Denitrification reduces NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; to N&lt;sub&gt;2&lt;/sub&gt; and in turn produces alkalinity.&lt;/p&gt;&lt;p&gt;Eutrophication, caused by leaching of excess fertilizer nutrients into coastal seas, leads to enhanced denitrification and therefore to enhanced alkalinity as well as an increased uptake of CO&lt;sub&gt;2&lt;/sub&gt;. However, the quantitative relationship between denitrification and alkalinity production and its control under changing environmental conditions is yet to be determined.&lt;/p&gt;&lt;p&gt;In the German Bight, denitrification is usually restricted to anoxic sediments. In this study, we therefore focus on in-situ experiments in the sediment - water column interface. Batch core incubations in combination with the isotope pairing technique (IPT) and labelled nitrate additions were used to detect denitrification and gauge its effect on alkalinity production during a cruise on RV Heincke (HE541) in September 2019 in the German Bight. To quantify denitrification, the production of all three N&lt;sub&gt;2&lt;/sub&gt; isotope species (&lt;sup&gt;28&lt;/sup&gt;N&lt;sub&gt;2&lt;/sub&gt;, &lt;sup&gt;29&lt;/sup&gt;N&lt;sub&gt;2&lt;/sub&gt; and &lt;sup&gt;30&lt;/sup&gt;N&lt;sub&gt;2&lt;/sub&gt;) is measured using a membrane inlet mass spectrometer (MIMS). We expect an increase of denitrification rates with nitrate concentrations and incubation times, and we will quantify benthic denitrification. We will further evaluate the assumption of concurrent increases in alkalinity production and will investigate the benthic-pelagic coupling of these processes. Investigating the in-situ interaction of metabolic alkalinity and denitrification will give an estimation of the alkalinity impact on the reduction of anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; in the atmosphere.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Quantification of Litter Fall and Estimation of Nutrient Release Through in-Situ Decomposition of Leaf Litter From Some Important Mangrove Species of Indian Sundarbans

2021 ◽  
Author(s):  
S.K. Das ◽  
Ranjan Kumar Manna ◽  
Pranab Gogoi ◽  
Roshith C. M. ◽  
Sajina A. M. ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Leaf Litter ◽  
Nutrient Dynamics ◽  
Nutrient Release ◽  
Mangrove Ecosystem ◽  
Litter Fall ◽  
Mangrove Species ◽  
Indian Sundarbans ◽  
In Situ Experiments

Abstract Looking into the importance of mangrove leaf litter in regulation of sediment carbon sequestration and nutrient flux in Sundarbans ecosystem, an experiment was conducted at Jharkhali island of Sundarbans. In this experiment, collection of leaf litter-shedding from nine dominant mangrove species during December 2012 to November 2013 was donemonthly using ‘litter traps’ (1 m2) in Eco-garden on the bank of Herobhanga creek.Seasonal litter fall was highest in Geon (Excoecariaagallocha)(103 gm-2) followed by Keora (Sonneratiaapetala) (98.5 gm-2). Kal Bain (Avicennia alba) produced the highest amount (414.37 gm-2) of total annual leaf litter followed by Bruguieragymnorrhiza (410.43 gm-2). Kankra (Bruguieragymnorrhiza), Garjan (Rhizophoramucronata) and Geon (Excoecariaagallocha) dry leaf litters contained more than 50% carbon (oven dry basis). Litter from Avicennia group contained more nitrogen and carbon. Decomposition rates of various mangrove litters were estimated through twoshort-term (30 days and 52 days) in-situ experiments using mangrove leaf litter in nylon net bags (0.6 mm mesh) subjected to periodical diurnal submergence by tidalriver water at Jharkhali. During decomposition process,observation said thatmost susceptible and resistant litter with respect to mass loss were Geon (Excoecariaagallocha) (81±5.5%) and Taura (Aegialitisrotundifolia) (26±4%) respectivelyafter 30 days. The biomass retained after decomposition losses (average45±15.2%after 30 days and 56±20.2 % after 52 days) indicated the amount of carbon retained in mangrove soil and ultimately determines the carbon sequestered in soil through mangrove litter fall. The study gives important insight into contribution of different mangrove species in carbon sequestration and nutrient dynamics in mangrove ecosystem of Indian Sundarbans.

scholarly journals Seasonal Variation in Mineral Nutrient Content of Primocane-fruiting Blackberry Leaves

HortScience ◽  
2015 ◽  
Vol 50 (4) ◽  
pp. 540-545 ◽  
Author(s):  
Bernadine C. Strik
Keyword(s):  
Nutrient Concentration ◽  
Nutrient Status ◽  
Mineral Nutrient ◽  
Nutrient Concentrations ◽  
Plant Nutrient ◽  
Green Fruit ◽  
Stage Of Development ◽  
Significant Difference ◽  
Leaf Sampling ◽  
Fruit Stage

Primocane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars, Prime-Jan® and Prime-Jim®, grown only for a primocane crop, were studied for 2 years to evaluate whether this type of blackberry should be sampled at a certain stage of development or time of season to best evaluate plant nutrient status. Leaves were sampled every 2 weeks from a primocane height of ≈0.75 m in spring through fruit harvest in autumn and were analyzed to determine concentration of macro- and micronutrients. Primocanes were summer pruned at 1.4 m, by hedging to a height of 1.0 m, to induce branching, a standard commercial practice. Leaf nutrient concentration was related to stage of primocane growth and development and whether the leaves originated on the main cane or on the branches that resulted from summer pruning. Nutrient concentration of leaves sampled on the main primocane from early growth in spring until early branch growth in summer was significantly affected by cultivar, year, and week for most nutrients. When leaf sampling occurred on the older leaves of the main cane (for 4 weeks after hedging), the concentration of Ca, Mg, B, Fe, Mn, and Al increased, likely a result of the relative immobility of most of these nutrients. When samples were taken on primocane branches, leaf N, Mg, S, B (2009 only), Fe, Mn, Cu (2009 only), Zn, and Al concentrations did not differ between samples taken 6–8 weeks after summer pruning or hedging. Leaf K and Ca were more stable when sampling was done from weeks 8 to 10 (early bloom to green/early red fruit). There was a significant difference in leaf P among all weeks sampled during this period. A sample date corresponding to early green fruit stage (week 8) would thus likely provide the best compromise for assessing plant nutrient status in this crop. During this stage of development the nutrient concentrations measured for both cultivars and years, were within the present recommended nutrient sufficiency levels for other blackberry and raspberry crops for all except leaf K and P which were below current standards. The results suggest leaf sampling primocane-fruiting blackberry at the early green fruit stage (about 8 weeks after summer pruning) rather than a particular calendar date. The present leaf sufficiency range for P and K may need to be lowered for this crop. In addition, sampling cultivars separately for tissue analysis would still be advised to better manage nutrient programs.

scholarly journals The trophic biology of the holothurian <i>Molpadia musculus</i>: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon

2010 ◽  
Vol 7 (8) ◽  
pp. 2419-2432 ◽  
Author(s):  
T. Amaro ◽  
S. Bianchelli ◽  
D. S. M. Billett ◽  
M. R. Cunha ◽  
A. Pusceddu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ecosystem Functioning ◽  
Submarine Canyon ◽  
Gut Contents ◽  
Digestion Rate ◽  
In Situ Experiments ◽  
Total Digestion ◽  
Organic Matter Cycling

Abstract. Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m−2 d−1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

scholarly journals Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment

2018 ◽  
Vol 15 (9) ◽  
pp. 2873-2889 ◽  
Author(s):  
Philip M. Riekenberg ◽  
Joanne M. Oakes ◽  
Bradley D. Eyre
Keyword(s):  
Water Column ◽  
Nutrient Availability ◽  
Nutrient Enrichment ◽  
Extracellular Enzymes ◽  
Turnover Time ◽  
Ex Situ ◽  
Nutrient Concentrations ◽  
Organic C ◽  
Storage Products

Abstract. Shallow coastal waters in many regions are subject to nutrient enrichment. Microphytobenthos (MPB) can account for much of the carbon (C) fixation in these environments, depending on the depth of the water column, but the effect of enhanced nutrient availability on the processing and fate of MPB-derived C (MPB-C) is relatively unknown. In this study, MPB was labeled (stable isotope enrichment) in situ using 13C-sodium bicarbonate. The processing and fate of the newly fixed MPB-C was then traced using ex situ incubations over 3.5 days under different concentrations of nutrients (NH4+ and PO43-: ambient, 2× ambient, 5× ambient, and 10× ambient). After 3.5 days, sediments incubated with increased nutrient concentrations (amended treatments) had increased loss of 13C from sediment organic matter (OM) as a portion of initial uptake (95 % remaining in ambient vs. 79–93 % for amended treatments) and less 13C in MPB (52 % ambient, 26–49 % amended), most likely reflecting increased turnover of MPB-derived C supporting increased production of extracellular enzymes and storage products. Loss of MPB-derived C to the water column via dissolved organic C (DOC) was minimal regardless of treatment (0.4–0.6 %). Loss due to respiration was more substantial, with effluxes of dissolved inorganic C (DIC) increasing with additional nutrient availability (4 % ambient, 6.6–19.8 % amended). These shifts resulted in a decreased turnover time for algal C (419 days ambient, 134–199 days amended). This suggests that nutrient enrichment of estuaries may ultimately lead to decreased retention of carbon within MPB-dominated sediments.

scholarly journals Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: A <sup>13</sup>C pulse-chase experiment

2017 ◽  
Author(s):  
Philip M. Riekenberg ◽  
Joanne M. Oakes ◽  
Bradley D. Eyre
Keyword(s):  
Water Column ◽  
Nutrient Availability ◽  
Extracellular Enzymes ◽  
Turnover Time ◽  
Ex Situ ◽  
Nutrient Concentrations ◽  
Organic C ◽  
Storage Products ◽  
And Storage

Abstract. Shallow coastal waters in many regions are subject to nutrient over-enrichment. Microphytobenthos (MPB) can account for much of the carbon (C) fixation in these environments, depending on the depth of the water column, but the effect of enhanced nutrient availability on the processing and fate of MPB-derived C is relatively unknown. In this study, MPB were labeled (stable isotope enrichment) in situ using 13C-sodium bicarbonate. The processing and fate of the newly-fixed MPB-C was then traced using ex situ incubations over 3.5 d under different concentrations of nutrients (NH4+ and PO43−: ambient, 2× ambient, 5× ambient, and 10× ambient). After 3.5 d, sediments incubated with increased nutrient concentrations (amended treatments) had increased loss of 13C from sediment organic matter as a portion of initial uptake (95 % remaining in ambient vs 79–93 % for amended treatments) and less 13C in MPB (52 % ambient, 26–49 % amended), most likely reflecting increased turnover of MPB-derived C supporting increased production of extracellular enzymes and storage products. Loss of MPB-derived C to the water column via dissolved organic C was minimal regardless of treatment (0.4–0.6 %). Loss due to respiration was more substantial, with effluxes of dissolved inorganic C increasing with additional nutrient availability (4 % ambient, 6.6–19.8 % amended). These shifts resulted in a decreased turnover time for algal C (419 d ambient, 134–199 d amended). This suggests that nutrient enrichment of estuaries may ultimately lead to decreased retention of carbon within MPB-dominated sediments.

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