What Is the Role of Fresh Groundwater and Recirculated Seawater in Conveying Nutrients to the Coastal Ocean?

2011 ◽  
Vol 45 (12) ◽  
pp. 5195-5200 ◽  
Author(s):  
Yishai Weinstein ◽  
Yoseph Yechieli ◽  
Yehuda Shalem ◽  
William C. Burnett ◽  
Peter W. Swarzenski ◽  
...  
Keyword(s):  
Coastal Ocean ◽  
Fresh Groundwater

scholarly journals DOM degradation by light and microbes along the Yukon River-coastal ocean continuum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Brice K. Grunert ◽  
Maria Tzortziou ◽  
Patrick Neale ◽  
Alana Menendez ◽  
Peter Hernes
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Salinity Gradient ◽  
Coastal Ocean ◽  
Interactive Effects ◽  
The Arctic ◽  
Yukon River ◽  
Spring Freshet ◽  
Dom Composition

AbstractThe Arctic is experiencing rapid warming, resulting in fundamental shifts in hydrologic connectivity and carbon cycling. Dissolved organic matter (DOM) is a significant component of the Arctic and global carbon cycle, and significant perturbations to DOM cycling are expected with Arctic warming. The impact of photochemical and microbial degradation, and their interactive effects, on DOM composition and remineralization have been documented in Arctic soils and rivers. However, the role of microbes, sunlight and their interactions on Arctic DOM alteration and remineralization in the coastal ocean has not been considered, particularly during the spring freshet when DOM loads are high, photoexposure can be quite limited and residence time within river networks is low. Here, we collected DOM samples along a salinity gradient in the Yukon River delta, plume and coastal ocean during peak river discharge immediately after spring freshet and explored the role of UV exposure, microbial transformations and interactive effects on DOM quantity and composition. Our results show: (1) photochemical alteration of DOM significantly shifts processing pathways of terrestrial DOM, including increasing relative humification of DOM by microbes by > 10%; (2) microbes produce humic-like material that is not optically distinguishable from terrestrial humics; and (3) size-fractionation of the microbial community indicates a size-dependent role for DOM remineralization and humification of DOM observed through modeled PARAFAC components of fluorescent DOM, either through direct or community effects. Field observations indicate apparent conservative mixing along the salinity gradient; however, changing photochemical and microbial alteration of DOM with increasing salinity indicate changing DOM composition likely due to microbial activity. Finally, our findings show potential for rapid transformation of DOM in the coastal ocean from photochemical and microbial alteration, with microbes responsible for the majority of dissolved organic matter remineralization.

scholarly journals Integrating Hydrogeological and Microbiological Data and Modelling to Characterize the Hydraulic Features and Behaviour of Coastal Carbonate Aquifers: A Case in Western Cuba

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1989 ◽  
Author(s):  
Rebeca Hernàndez-Diaz ◽  
Emma Petrella ◽  
Antonio Bucci ◽  
Gino Naclerio ◽  
Alessandra Feo ◽  
...  
Keyword(s):  
Primary Source ◽  
Interdisciplinary Approach ◽  
Mixing Processes ◽  
Fresh Groundwater ◽  
Experimental Modelling ◽  
Carbonate Aquifers ◽  
Saltwater Wedge ◽  
Microbiological Data ◽  
Modelling Approach

Carbonate aquifers are the primary source of freshwater in Cuba. Unfortunately, coastal groundwater is often contaminated by seawater intrusion. The main aim of the present study was to test the efficacy of an experimental modelling approach, ranging from hydrogeology/geomorphology to microbiology, to better characterise both the hydraulic features and behaviour of a coastal carbonate aquifer and acquire useful information to prevent groundwater salinization. The interdisciplinary approach was an effective tool in order to understand (i) the hydraulic role played by some fault zones; (ii) the influence of discontinuous heterogeneities on groundwater flow and saltwater wedge shape; (iii) mixing processes between different water bodies (groundwater, surface water, seawater); (iv) the role of karst conduits in influencing the step-like halocline within the mixing zone between fresh groundwater and seawater.

scholarly journals Riverine influence on the tropical Atlantic Ocean biogeochemistry

2013 ◽  
Vol 10 (10) ◽  
pp. 6357-6373 ◽  
Author(s):  
L. C. da Cunha ◽  
E. T. Buitenhuis
Keyword(s):  
Atlantic Ocean ◽  
Coastal Ocean ◽  
Open Ocean ◽  
N Fixation ◽  
South American ◽  
Tropical Atlantic ◽  
Co2 Fluxes ◽  
Tropical Atlantic Ocean ◽  
Ocean Biogeochemistry

Abstract. We assess the role of riverine inputs of N, Si, Fe, organic and inorganic C in the tropical Atlantic Ocean using a global ocean biogeochemistry model. We use a standard model scenario and three sensitivity tests to investigate the role of total river nutrient and carbon inputs, as well as the western (South American) and eastern (African) river inputs on the tropical Atlantic Ocean biogeochemistry, between 20° S–20° N and 70° W–20° E. Increased nutrient availability from river inputs in this area (compared to a sensitivity scenario without river nutrient inputs, NO_RIVER) leads to an increase in primary production (PP) and export production (EP), mainly in the coastal ocean area (modeled ocean area with bathymetry <200 m). Model results suggest an enhanced N-fixation by diazotrophs on the tropical Atlantic mainly in open ocean areas. The increased rate of N-fixation in the TODAY scenario is proportional to the increase in PP and EP relative to the NO_RIVER scenario, and may support up to 14% of the coastal ocean export production. Inputs from South American rivers have an impact in coastal PP and EP two times higher than those from African rivers. On the other hand, results suggest that the contribution of African and South American rivers to the total increase in open ocean PP and EP is similar. Considering the amount of delivered nutrients (2–3 times less nutrients and carbon inputs by African rivers) one concludes that African riverine inputs may have a larger impact on the whole tropical Atlantic Ocean biogeochemistry. This is probably due to a combination of nutrient trapping in upwelling areas off the large rivers' outflows and shallow mixed layers in the eastern tropical Atlantic, concomitantly to the differences in delivered nutrient ratios leading to alleviation in limitation conditions, mainly for diatoms. When river inputs are added to the model, we estimate a modest decrease in open ocean sea-air CO2 fluxes (−5.2 Tg C a−1) and an increase in coastal ocean CO2 fluxes, mainly provoked by the remineralization of riverine organic matter delivered by the South American rivers.

scholarly journals The Role of a Permeable Sand Column in Modifying Tidal Creek Nutrient Inputs into the Coastal Ocean

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3079
Author(s):  
Nicholas A. Legut ◽  
Brandon T. Hawkins ◽  
Angelos K. Hannides
Keyword(s):  
South Carolina ◽  
Nutrient Loading ◽  
Salinity Gradient ◽  
Coastal Ocean ◽  
Coastal Sediments ◽  
Nutrient Inputs ◽  
Tidal Creeks ◽  
Overlying Water ◽  
Sand Column

Estuarine tidal creeks are an important conduit for freshwater run-off into the coastal ocean. In Long Bay, South Carolina, tidal creeks terminate in swashes—broad sandy fields constantly reworked by discharged creek water. We examined the role of a highly permeable sandy column in altering the nutrient loading of the passing water at Singleton Swash, Myrtle Beach, South Carolina. Seasonal transects along the swash’s primary channel documented gradients in physical and biogeochemical parameters. The nutrient and chlorophyll a concentrations were higher in the sediment than in the overlying water, consistent with coastal sediments as a major site of organic matter degradation, nutrient regeneration, and benthic primary productivity. Oxygen, nutrient, and chlorophyll concentrations exhibited a strong seasonal component, explained by a photosynthesis–respiration balance shift between summer and winter. The conservative mixing model approach to elucidate the sink–source patterns was moderately informative due to the lack of a gradual salinity gradient from land to ocean, due to substantial tidal flushing and observable nutrient-rich surface freshwater discharges along the channel that fueled substantial submerged aquatic macroalgal growth. Future studies should focus on the role of benthic photosynthesizers, both microbial and macroalgal, in retaining land-derived nutrients in irrigation freshwater inputs prior to them reaching the coastal ocean.

scholarly journals Tracking How Plastic Moves in the Coastal Ocean

Eos ◽  
2020 ◽  
Vol 101 ◽  
Author(s):  
Kate Wheeling
Keyword(s):  
Particle Density ◽  
Coastal Ocean ◽  
Wave Tank ◽  
Drift Behavior

Researchers used a wave tank to study the movement of plastic particles experimentally and to understand the role of particle density in drift behavior.

Role of Oxalic acid on Fractional Solubility of Aerosol Iron over Coastal Ocean: Evidence from compound-specific stable carbon isotopic composition and diagnostic mass ratios

2020 ◽  
Author(s):  
Srinivas Bikkina ◽  
Kimitaka Kawamura ◽  
Manmohan Sarin ◽  
Eri Tachibana
Keyword(s):  
Oxalic Acid ◽  
Organic Acids ◽  
Isotopic Composition ◽  
Linear Relationship ◽  
Carbon Isotopic Composition ◽  
Coastal Ocean ◽  
Water Soluble ◽  
Stable Carbon ◽  
Carbon Isotopic

&lt;p&gt;Atmospheric transport and the subsequent air-to-sea deposition of water-soluble iron (Fe&lt;sub&gt;ws&lt;/sub&gt;), an essential micronutrient for the phytoplankton growth, have a profound influence on the biogeochemical cycles of carbon and nitrogen. Sources of Fe&lt;sub&gt;ws&lt;/sub&gt; include contributions from poorly soluble natural mineral dust and highly soluble anthropogenic aerosols from biomass burning emissions and fossil-fuel combustion in the continental outflows. Apart from the source/emission contributions, atmospheric processing of aerosol iron (Fe&lt;sub&gt;Tot&lt;/sub&gt;) by inorganic acidic species (&lt;em&gt;e.g.&lt;/em&gt;, non-sea-salt or nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;) and/or organic acids also affect the supply of Fe&lt;sub&gt;ws&lt;/sub&gt; to the surface waters that are downwind of pollution sources. Among these, the least understood process is the oxalic acid-mediated photochemical cycling of Fe&lt;sub&gt;ws&lt;/sub&gt;. Laboratory studies have clearly demonstrated an enhancement in the fractional solubility of aerosol iron (i.e., Fe&lt;sub&gt;ws &lt;/sub&gt;(%) = Fe&lt;sub&gt;ws&lt;/sub&gt;/Fe&lt;sub&gt;Tot&lt;/sub&gt; &amp;#215;100) via the oxalic acid complexation with Fe&lt;sub&gt;Tot&lt;/sub&gt; and subsequent photochemical reduction process. However, lacking support from the field measurements limits our ability to incorporate the proposed mechanism in the current biogeochemistry models. This study is designed with the overarching goal of investigating the role of oxalic acid on the Fe&lt;sub&gt;ws &lt;/sub&gt;(%) over a coastal ocean (i.e., the Bay of Bengal: BoB) influenced by the atmospheric outflow from the Indo-Gangetic Plain (IGP) and South-east Asia (SEA) during the winter season. We analysed 31 PM&lt;sub&gt;2.5&lt;/sub&gt; samples for the mass concentrations of Fe&lt;sub&gt;Tot&lt;/sub&gt;, Fe&lt;sub&gt;ws&lt;/sub&gt; and other chemical composition including nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;, NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, oxalic acid and related polar compounds as well as stable carbon isotopic composition of oxalic acid (&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;oxalic&lt;/sub&gt;). Strong positive linear relationship of oxalic acid with Fe&lt;sub&gt;Tot&lt;/sub&gt; and significant inverse linear relationship between &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;oxalic &lt;/sub&gt;and Fe&lt;sub&gt;ws&lt;/sub&gt; over the BoB clearly emphasize the role of oxalic acid on the Fe&lt;sub&gt;ws&lt;/sub&gt; (%). &amp;#160;These findings comply with the notion that oxalic acid formed from the precursor water-soluble organic acids in the deliquescent aerosols, is complexed with aerosol-Fe and undergoes through successive photochemical reactions, contributing to an overall increase in the Fe&lt;sub&gt;ws &lt;/sub&gt;(%).&amp;#160;&lt;/p&gt;

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