scholarly journals Organic matter quantity and quality across salinity gradients in conduit‐ vs. diffuse flow‐dominated subterranean estuaries

2019 ◽  
Vol 64 (3) ◽  
pp. 1386-1402 ◽  
Author(s):  
Andrea J. Pain ◽  
Jonathan B. Martin ◽  
Caitlin R. Young ◽  
Laibin Huang ◽  
Arnoldo Valle‐Levinson
Keyword(s):  
Organic Matter ◽  
Diffuse Flow ◽  
Salinity Gradients ◽  
Subterranean Estuaries

scholarly journals Changes in Organic Matter Deposition Can Impact Benthic Marine Meiofauna in Karst Subterranean Estuaries

2021 ◽  
Vol 9 ◽  
Author(s):  
David Brankovits ◽  
Shawna N. Little ◽  
Tyler S. Winkler ◽  
Anne E. Tamalavage ◽  
Luis M. Mejía-Ortíz ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ecosystem Functioning ◽  
Storm Events ◽  
Terrestrial Organic Matter ◽  
Core Sediment ◽  
Carbon Isotopic ◽  
Cozumel Island ◽  
Intense Storm ◽  
Terrestrial Environments ◽  
Subterranean Estuaries

Subsurface mixing of seawater and terrestrial-borne meteoric waters on carbonate landscapes creates karst subterranean estuaries, an area of the coastal aquifer with poorly understood carbon cycling, ecosystem functioning, and impact on submarine groundwater discharge. Caves in karst platforms facilitate water and material exchange between the marine and terrestrial environments, and their internal sedimentation patterns document long-term environmental change. Sediment records from a flooded coastal cave in Cozumel Island (Mexico) document decreasing terrestrial organic matter (OM) deposition within the karst subterranean estuary over the last ∼1,000 years, with older sediment likely exported out of the cave by intense storm events. While stable carbon isotopic values (δ13Corg ranging from −22.5 to −27.1‰) and C:N ratios (ranging from 9.9 to 18.9) indicate that mangrove and other terrestrial detritus surrounding an inland sinkhole are the primarily sedimentary OM supply, an upcore decrease in bulk OM and enrichment of δ13Corg values are observed. These patterns suggest that a reduction in the local mangrove habitat decreased the terrestrial particulate OM input to the cave over time. The benthic foraminiferal community in basal core sediment have higher proportions of infaunal taxa (i.e., Bolivina) and Ammonia, and assemblages shift to increased miliolids and less infaunal taxa at the core-top sediment. The combined results suggest that a decrease in terrestrial OM through time had a concomitant impact on benthic meiofaunal habitats, potentially by impacting dissolved oxygen availability at the microhabitat scale or resource partitioning by foraminifera. The evidence presented here indicates that landscape and watershed level changes can impact ecosystem functioning within adjacent subterranean estuaries.

scholarly journals Habitat Partitioning in the Marine Sector of Karst Subterranean Estuaries and Bermuda's Marine Caves: Benthic Foraminiferal Evidence

2021 ◽  
Vol 8 ◽  
Author(s):  
Jacquelyn N. Cresswell ◽  
Peter J. van Hengstum
Keyword(s):  
Organic Matter ◽  
Benthic Foraminifera ◽  
Organic Matter Content ◽  
Matter Content ◽  
Habitat Partitioning ◽  
Benthic Habitat ◽  
Marine Plankton ◽  
Organic Matter Sources ◽  
Bulk Organic Matter ◽  
Subterranean Estuaries

Karst subterranean estuaries (KSEs) are created from the two- and three-way mixing of saline groundwater, rain, and oceanic water in the subsurface on carbonate landscapes, and this hydrographic framework promotes unique physical processes, biogeochemical cycling, and biological communities. Here we provide evidence that the source and quantity of particulate organic matter (POM) that is delivered to the benthos strongly correlates to benthic habitat partitioning in the oxygenated marine sectors of KSEs. A dataset of benthic foraminifera at 128 different locations from several large flooded cave systems in Bermuda were compiled and evaluated against common environmental characteristics (e.g., tidal exposure, substrate particle size, bulk organic matter, C:N, total organic carbon, and δ13Corg). Benthic areas receiving more carbon isotopically depleted organic matter sources (mean δ13Corg values < −23.2‰, C:N ratios >11), most likely from the terrestrial surface and some marine plankton, were dominated by Trochammina inflata, Bolivina spp., and Helenina anderseni. In contrast, benthic areas receiving more carbon isotopically enriched organic matter sources (mean δ13Corg values > −21.6‰, C:N ratios <10), most likely from marine plankton transported through marine cave openings cave from adjacent coastal waters, were dominated by Spirophthalmidium emaciatum, Spirillina vivipara, Patellina corrugata, and Rotaliella arctica. The benthic foraminifera most distal from any cave entrances were dominated by taxa also known from the deep-sea (e.g., Rotaliella, Spirophthalmidium) in sediment with the lowest bulk organic matter content (mean: 6%), or taxa that prefer hard substrates and are potentially living attached to cave walls (Patellina, Spirillina). While physical groundwater characteristics (e.g., salinity, dissolved oxygen) are expected drivers of benthic ecosystems in KSEs, these results suggest that POM source, quantity, and delivery mechanisms (e.g., groundwater-seawater circulation mechanisms, terrestrial flux) play an important role in benthic habitat partitioning and the spatial variability of biogeochemical cycles in the oxygenated marine sector of KSEs.

Photo-reactivity of natural dissolved organic matter from fresh to marine waters in the Florida Everglades, USA

2014 ◽  
Vol 16 (4) ◽  
pp. 866-878 ◽  
Author(s):  
Stephen A. Timko ◽  
Cristina Romera-Castillo ◽  
Rudolf Jaffé ◽  
William J. Cooper
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Reactive Species ◽  
Florida Everglades ◽  
Marine Waters ◽  
Salinity Gradients ◽  
Photo Production

Photo-production of reactive species by NOM in the Florida Everglades was examined across salinity gradients and coupled with PARAFAC analysis.

Modern methane and dissolved organic matter radiocarbon signatures suggest rapid transfer of organic carbon from a tropical forest to the underlying subterranean estuary ecosystem

2020 ◽  
Author(s):  
David Brankovits ◽  
John Pohlman ◽  
Mark Garnett ◽  
Joshua Dean
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Food Web ◽  
Land Surface ◽  
Dissolved Inorganic Carbon ◽  
Trophic Levels ◽  
Carbon Turnover ◽  
Isotopic Analyses ◽  
Subterranean Estuaries

<p>Biogeochemical processing of dissolved organic matter, including methane, along sharp salinity gradients in subterranean estuaries greatly alters the composition of submarine groundwater discharge into the marine environment. Along the margins of coastal carbonate (karst) platforms, which account for ~25% of all coastlines, subterranean estuaries extend kilometers inland within porous bedrock, flooding extensive cave networks. This environment harbors a poorly understood, but globally dispersed, anchialine fauna (invertebrates with subterranean adaptations) and characteristic microbial communities. In Mexico’s Yucatan Peninsula, microbial processing of methane and dissolved organic carbon (DOC), originating from overlying tropical soils, is the critical link for shuttling organic matter to higher trophic levels of the food web within the coastal aquifer. To better understand carbon turnover during organic matter transformations in this habitat, we collected samples for stable and radiocarbon analyses targeting the biotic and abiotic components of the carbon cycle. In the freshwater, radiocarbon signatures of terrestrially originated DOC (pMC = 105.1; [DOC] = 517 µM; δ<sup>13</sup>C = ˗27.8 ‰) and methane (pMC = 101.6; [CH<sub>4</sub>] = 6460 nM; δ<sup>13</sup>C = ˗71.5 ‰) correspond with modern <sup>14</sup>C ages, suggesting these sources of energy within the habitat are comprised of modern carbon fixed recently by photosynthesizing primary producers at the land surface. By contrast, DOC in the deeper saline groundwater is significantly lower in concentration (21 µM), and substantially older (pMC = 47.3, equates to 6010 ± 95 <sup>14</sup>C yrs). Similarly, dissolved inorganic carbon (DIC) in the freshwater is significantly younger (pMC = 86.5, equates to 1170 ± 15 <sup>14</sup>C yrs) than in the deeper saline water (pMC = 58.4, equates to 4320 ± 25 <sup>14</sup>C yrs). These findings demonstrate that important sources of nutrition for the food web are intimately linked to the overlying subaerial habitat, which suggests these ecosystems are highly vulnerable to nearby land use alterations. Furthermore, this study provides new insights into carbon turnover during the process of methane production/consumption, carbon exchange, and organic matter transformation before the emission of the dissolved constituents into coastal oceans from karst subterranean estuaries. Radiocarbon and stable isotopic analyses of the resident fauna will allow us to evaluate the ecological effects of the rapid top-down transfer mechanism for methane and DOC. Beyond better understanding the sources and fate of these carbon sources, our findings have the potential to support management and conservation efforts aimed at coastal groundwater ecosystems.</p>

Inorganic nitrogen release from sediment slurry of riverine and estuarine ecosystems located at different river regimes

2017 ◽  
Vol 68 (7) ◽  
pp. 1282 ◽  
Author(s):  
Bhanu Paudel ◽  
Paul A. Montagna ◽  
Mark Besonen ◽  
Leslie Adams
Keyword(s):  
Organic Matter ◽  
Inorganic Nitrogen ◽  
River Sediments ◽  
River Estuary ◽  
Overlying Water ◽  
Salinity Gradients ◽  
Sediment Slurry ◽  
Guadalupe River ◽  
Nitrite Nitrate ◽  
Nueces River

The purpose of the present study was to compare the nature of dissolved inorganic nitrogen (DIN=ammonium (NH4+) and nitrite+nitrate (NO2+3=(NO2–+NO3–)) release from aerobic sediment slurry at two different hydrologic flow regimes. The watershed of the Guadalupe River–Estuary system receives more freshwater inflow than does the watershed of the Nueces River–Estuary system; thus, the Nueces Estuary is more saline than is the Guadalupe Estuary. Sediment samples were collected using cores, analysed for organic matter and grain size, and used to perform laboratory experiments to measure DIN release. During the experiments, DIN concentrations in overlying water were measured for 48h in five different salinity treatments. Ammonium concentrations were higher in the Nueces River and Estuary treatments than in similarly treated samples from the Guadalupe River and Estuary. An increase in NO2+3 concentrations along salinity gradients of the Nueces Estuary treatments indicated favourable condition for nitrification. The Guadalupe River sediments that were not exposed to salinity had an increase in NH4+ concentration at 7.5ppt. The different DIN release among salinity treatments indicated that hydrologic forcing on organic matter deposition and salinity have an important role on the retention and release of inorganic nitrogen at the sediment–water aerobic layers in rivers and estuaries.

scholarly journals Bryophytes as key indicators of ecosystem function and structure of northern peatlands

2021 ◽  
Vol 43 (1) ◽  
Author(s):  
DALE H. VITT ◽  
MELISSA HOUSE
Keyword(s):  
Organic Matter ◽  
Water Level ◽  
Ecosystem Function ◽  
Mechanisms Of Resistance ◽  
Salinity Gradients ◽  
Wetland Site ◽  
Key Indicators ◽  
Northern Peatlands ◽  
Site Types

Bryophytes play a number of important roles in the functioning and structure of northern peatlands where they form the ground layer of fens and bogs. Sphagnum, dominant in bogs and poor fens, and brown mosses, dominant in rich fens, make up a large percentage of the organic matter that is stored as deep deposits of peat. In this paper we review the mechanisms of resistance to decay in these two moss groups. We then document a case study of a rich fen dominated mostly by Hamatocaulis vernicosus, that has remained stable for over 8000 calendar years. At this site, we use macrofossil abundances, including bryophyte habitat positions on water level and chemistry gradients, to infer past environmental conditions. Lastly, we provide a new ecohydrologic framework for wetland classes centered on bryophyte abundances across water level, nutrient, and salinity gradients and argue that bryophyte species are among the most significant indicators for classifying wetland site-types.

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