Ecosystem responses to hydrologic change and mechanisms of nitrogen sequestration in seasonally flooded tree islands of the southern Everglades

In the Florida Everglades, tree islands are conspicuous heterogeneous elements in a complex wetland landscape. I investigated the effects of increased freshwater flow in southern Everglades seasonally flooded tree islands, and characterized biogeochemical interactions among tree islands and the marsh landscape matrix, specifically examining hydrologic flows of nitrogen (N), and landscape N sequestration capacity. I utilized ecological trajectories of key ecosystem variables to differentiate effects of increased sheetflow and hydroperiod. I utilized stable isotope analyses and nutrient content of tree island ecosystem components to test the hypothesis that key processes in tree island nitrogen cycling would favor ecosystem N sequestration. I combined estimates of tree island ecosystem N standing stocks and fluxes, soil and litter N transformation rates, and hydrologic inputs of N to quantify the net sequestration of N by a seasonally flooded tree island. ^ Results show that increased freshwater flow to seasonally flooded tree islands promoted ecosystem oligotrophy, whereas reduced flows allowed some plant species to cycle P less efficiently. As oligotrophy is a defining parameter of Everglades wetlands, and likely promotes belowground production and peat development, reintroducing freshwater flow from an upstream canal had a favorable effect on ecosystem dynamics of tree islands in the study area. Important factors influencing the stable isotopic composition of nitrogen and carbon were: (1) a contribution to soil N by soil invertebrates, animal excrement, and microbes, (2) a possible NO3 source from an upstream canal and an "open" ecosystem N cycle, and (3) greater availability of phosphorus in tree islands relative to the marsh landscape, suggesting that tree island N cycling favors N sequestration. Hydrologic sources of N were dominated by surface water loads of NO3- and NH 4+, and an important soil N transformation promoting the net loss of surface water DIN was nitrate immobilization associated with soils and surficial leaf litter. The net inorganic N sequestration capacity of a seasonally flooded tree island was 50 g yr-1 m -2. Thus, tree islands likely have an important function in landscape sequestration of inorganic N, and may reduce significant anthropogenic N loads to downstream coastal systems. ^

Projected Reorganization of Florida Bay Seagrass Communities in Response to the Increased Freshwater Inflow of Everglades Restoration

Historic changes in water-use management in the Florida Everglades have caused the quantity of freshwater inflow to Florida Bay to decline by approximately 60% while altering its timing and spatial distribution. Two consequences have been (1) increased salinity throughout the bay, including occurrences of hypersalinity, coupled with a decrease in salinity variability, and (2) change in benthic habitat structure. Restoration goals have been proposed to return the salinity climates (salinity and its variability) of Florida Bay to more estuarine conditions through changes in upstream water management, thereby returning seagrass species cover to a more historic state. To assess the potential for meeting those goals, we used two modeling approaches and long-term monitoring data. First, we applied the hydrological mass balance model FATHOM to predict salinity climate changes in sub-basins throughout the bay in response to a broad range of freshwater inflow from the Everglades. Second, because seagrass species exhibit different sensitivities to salinity climates, we used the FATHOM-modeled salinity climates as input to a statistical discriminant function model that associates eight seagrass community types with water quality variables including salinity, salinity variability, total organic carbon, total phosphorus, nitrate, and ammonium, as well as sediment depth and light reaching the benthos. Salinity climates in the western sub-basins bordering the Gulf of Mexico were insensitive to even the largest (5-fold) modeled increases in freshwater inflow. However, the north, northeastern, and eastern sub-basins were highly sensitive to freshwater inflow and responded to comparatively small increases with decreased salinity and increased salinity variability. The discriminant function model predicted increased occurrences ofHalodule wrightii communities and decreased occurrences of Thalassia testudinum communities in response to the more estuarine salinity climates. The shift in community composition represents a return to the historically observed state and suggests that restoration goals for Florida Bay can be achieved through restoration of freshwater inflow from the Everglades.

Determining Spatial and Temporal Inputs of Freshwater, Including Submarine Groundwater Discharge, to a Subtropical Estuary Using Geochemical Tracers, Biscayne Bay, South Florida

Geochemical mixing models were used to decipher the dominant source of freshwater (rainfall, canal discharge, or groundwater discharge) to Biscayne Bay, an estuary in south Florida. Discrete samples of precipitation, canal water, groundwater, and bay surface water were collected monthly for 2 years and analyzed for salinity, stable isotopes of oxygen and hydrogen, and Sr2+/Ca2+ concentrations. These geochemical tracers were used in three separate mixing models and then combined to trace the magnitude and timing of the freshwater inputs to the estuary. Fresh groundwater had an isotopic signature (δ 18O = −2.66‰, δD −7.60‰) similar to rainfall (δ 18O = −2.86‰, δD = −4.78‰). Canal water had a heavy isotopic signature (δ 18O = −0.46‰, δD  = −2.48‰) due to evaporation. This made it possible to use stable isotopes of oxygen and hydrogen to separate canal water from precipitation and groundwater as a source of freshwater into the bay. A second model using Sr2+/Ca2+ ratios was developed to discern fresh groundwater inputs from precipitation inputs. Groundwater had a Sr2+/Ca2+ ratio of 0.07, while precipitation had a dissimilar ratio of 0.89. When combined, these models showed a freshwater input ratio of canal/precipitation/groundwater of 37%:53%:10% in the wet season and 40%:55%:5% in the dry season with an error of ±25%. For a bay-wide water budget that includes saltwater and freshwater mixing, fresh groundwater accounts for 1–2% of the total fresh and saline water input.

Tree Island Response to Fire and Flooding in the Short-Hydroperiod Marl Prairie Grasslands of the Florida Everglades

Within the marl prairie grasslands of the Florida Everglades, USA, the combined effects of fire and flooding usually lead to very significant changes in tree island structure and composition. Depending on fire severity and post-fire hydroperiod, these effects vary spatially and temporally throughout the landscape, creating a patchy post-fire mosaic of tree islands with different successional states. Through the use of the Normalized Difference Vegetation Index (NDVI) and three predictor variables (marsh water table elevation at the time of fire, post-fire hydroperiod, and tree island size), along with logistic regression analysis, we examined the probability of tree island burning and recovering following the Mustang Corner Fire (May to June 2008) in Everglades National Park. Our data show that hydrologic conditions during and after fire, which are under varying degrees of management control, can lead to tree island contraction or loss. More specifically, the elevation of the marsh water table at the time of the fire appears to be the most important parameter determining the severity of fire in marl prairie tree islands. Furthermore, in the post-fire recovery phase, both tree island size and hydroperiod during the first year after the fire played important roles in determining the probability of tree island recovery, contraction, or loss.

Properties of seawater from a Sea-Bird TSG temperature and conductivity sensor mounted on the continuous surface water sampling system during campaign TARA_20110311Z of the Tara Oceans expedition 2009-2013

The Tara Oceans Expedition (2009-2013) sampled the world oceans on board a 36 m long schooner, collecting environmental data and organisms from viruses to planktonic metazoans for later analyses using modern sequencing and state-of-the-art imaging technologies. Tara Oceans Data are particularly suited to study the genetic, morphological and functional diversity of plankton. The present data publication contains measurements from the Continuous Surface Sampling System [CSSS] made during one campaign of the Tara Oceans Expedition. Water was pumped at the front of the vessel from ~2m depth, then de-bubbled and circulated to a Sea-Bird TSG temperature and conductivity sensor. System maintenance (instrument cleaning, flushing) was done approximately once a week and in port between successive legs. All data were stamped with a GPS.

Oceanographic investiations from the Sea of Ochotsk

The Sea of Okhotsk is a marginal sea of the Pacific Ocean, which is characterized by strong variations in the productivity and sediment supply due to sea ice transport and river input. Furthermore the variations in the hydrological cycle determine the formation of the SOIW (Sea of Okhotsk Intermediate Water) which plays an important role in the ventilation processes in the intermediate water of the N-Pacific. Isotope data measured on planktonic and benthic foraminifera, sedimentological and geochemical studies of sediment cores and surface samples from the Sea of Okhotsk are used to reconstruct the paleoceanography during the past 350.000 years. The dating and correlation of the sediments are based on oxygen isotope stratigraphy, absolute ages, magnetic susceptibility as well as a detailled tephrachronology of the entire basin. The sedimentation rates are characterized by temporal and spatial variations. The maximum sedimentation rate takes place at the continental slope off Sakhalin due to the input of the Amur River, the sea ice drift and the high productivity. The sedimentation rate in the eastern part of the Sea of Okhotsk is generelly high because of the influence of the nutrient-rich Kamchatka Current. In the central and northern parts of the Sea of Okhotsk, areas with low productivity and reduced terrestrial supply, the sedimentation rate is the lowest. The analyses of the surface sediment samples make it possible to characterize the (sub)- recent sediment supply and transportation processes. The bulk sediment measurements, isotope data and the accumulation rate of ice-rafted debris (IRD) show a dominant sea ice cover and a region with a high productivity as well as a high Amur River input in the western part of the sea. The eastern part of the Sea of Okhotsk, however, is marked by the predominance of warm and nutrient-rich water masses coming from the Kamchatka Current which restricts the sea ice cover. This is reflected in low content of ice-rafted debris and high productivity proxies as well as in isotope data. The deposits of the Sea of Okhotsk are characterized by terrestrial, biogenic and volcanogenic sediment input which varies temporally and spatially. Here, the sedimentation pattern is dominated by the terrestrial input. Bulk sediment measurements and sample analyses of the > 63 micron particle input make it possible to distinguish glacial and interglacial fluctuations. The sedimentation processes during glacial times are determined by a high content of ice-rafted debris, whereas the primary production is higher during interglacial periods. During the last glacial/interglacial cycle the IRD-distribution pattern indicates a strong sea ice transport in the western part and in large areas of the open sea in the eastern part of the Sea of Okhotsk with a relatively constant ice-drift system. The IRD flux in sediments of the oxygen isotope Stage 6 reflects a new sedimentation pattern in the eastern part of the sea. This high IRD accumulation rate indicates ice advances beyond the shelf margin and an iceberg transport from NE-E direction into the Sea of Okhotsk. The several large, brief, negative anomalies in d13C values of Neogloboquadrina pachyderma (s) show releases of methane from basin sediments which correspond to periods of relative sea level falls. The high sedimentation rates on the Sakhalin slope allow insights into the climatic history in Holocene and indicate shorter-scale variations oscillation in Stage 3, which correlate with the global climatic changes. These variations are described as Dansgaard-Oeschger cycles in Greenland ice cores and as Heinrich-Events in several marine sediment cores from the N-Atlantic.

Chemical and isotopic compositions of water, particulates, plankton, gases, sediments, and minerals from the Kara Sea and lower Ob and Yenisei Rivers

The Kara Sea is an area uniquely suitable for studying processes in the river-sea system. This is a shallow sea, into which two great Siberian rivers, Yenisei and Ob, flow. From 1995 to 2003, the sea was studied by six international expeditions onboard the R/V Akademik Boris Petrov. This publication summarizes the results obtained, within the framework of this project, at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Various hydrogeochemical parameters, concentrations and isotopic composition of organic and carbonate carbon of the sediments, plankton, particulate organic matter, hydrocarbons, and dissolved CO2 were examined throughout the whole sea area at more than 200 sites. The d13C varies from -22 and -24 per mil where Atlantic waters enter the Kara Sea and in the north-eastern part of the water area to -27 per mil in the Yenisei and Ob estuaries. The value of d13C of the plankton is only weakly correlated with the d13C of the organic matter from the sediments and is lower by as much as 3-4 per mil. The paper presents the results obtained from a number of meridional river-sea profiles. It was determined from the relations between the isotopic compositions of plankton and particulate matter that the river waters carry material consisting of 70% detrital-humus matter and 30% planktonogenic material in the river part, and the material contained in the offshore waters consists of 30% terrigenous components, with the contribution of bioproducers amounting to 70%. The carbon isotopic composition of the plankton ranges from -29 to -35 per mil in the riverine part, from -28 to -27 per mil in the estuaries, and from -27.0 to -25 per mil in the marine part. The relative lightness of the carbon isotopic composition of plankton in Arctic waters is explained by the temperature effect, elevated CO2 concentrations, and long-distance CO2 supply to the sea with river waters. The data obtained on the isotopic composition of CO2 in the surface waters of the Kara Sea were used to map the distribution of d13C. The complex of hydrocarbon gases extracted from the waters included methane, C2-C5, and unsaturated C2=-C4= hydrocarbons, for which variations in the concentrations in the waters were studied along river-estuary-sea profiles. The geochemistry of hydrocarbon gases in surface fresh waters is characterized by comparable concentrations of methane (0.3-5 µl/l) and heavier hydrocarbons, including unsaturated ones. Microbiological methane with d13C from -105 to -90 per mil first occurs in the sediments at depths of 40-200 cm. The sediments practically everywhere display traces of methane oxidation in the form of a shift of the d13C of methane toward higher values and the occurrence of autogenic carbonate material, including ikaite, enriched in the light isotope. Ikaite (d13C from -25 to -60 per mil) was found and examined in several profiles. The redox conditions in the sediments varied from normal in the southern part of the sea to highly oxidized along the Novaya Zemlya Trough. Vertical sections through the sediments of the latter exemplify the complete suppression of the biochemical activity of microorganisms. Our data provide insight into the biogeochemistry of the Kara Sea and make it possible to specify the background values needed for ecological control during the future exploration operations and extraction of hydrocarbons in the Kara Sea.

Benthic organic carbon flux and oxygen penetration depth in the Southern Ocean

For the investigation of organic carbon fluxes reaching the seafloor, oxygen microprofiles were measured at 145 sites in different sub-regions of the Southern Ocean. At eleven sites, an in situ oxygen microprofiler was deployed for the measurement of oxygen profiles and the calculation of organic carbon fluxes. At four sites, both in situ and ex situ data were determined for high latitudes. Based on this dataset as well as on previous published data, a relationship was established for the estimation of fluxes derived by ex situ measured O2 profiles. The fluxes of labile organic matter range from 0.5 to 37.1 mgC m**2/day. The high values determined by in situ measurements were observed in the Polar Front region (water depth of more than 4290 m) and are comparable to organic matter fluxes observed for high-productivity, upwelling areas like off West Africa. The oxygen penetration depth, which reflects the long-term organic matter flux to the sediment, was correlated with assemblages of key diatom species. In the Scotia Sea (~3000 m water depth), oxygen penetration depths of less than 15 cm were observed, indicating high benthic organic carbon fluxes. In contrast, the oxic zone extends down to several decimeters in abyssal sediments of the Weddell Sea and the southeastern South Atlantic. The regional pattern of organic carbon fluxes derived from micro-sensor data suggest that episodic and seasonal sedimentation pulses are important for the carbon supply to the seafloor of the deep Southern Ocean.

(Table 1) Age control points and dating methods for sediment cores of the Sea of Okhotsk

Marine- and terrestrial-derived biomarkers (alkenones, brassicasterol, dinosterol, and long-chain n-alkanes), as well as carbonate, biogenic opal, and ice-rafted debris (IRD), were measured in two sediment cores in the Sea of Okhotsk, which is located in the northwestern Pacific rim and characterized by high primary productivity. Down-core profiles of phytoplankton markers suggest that primary productivity abruptly increased during the global Meltwater Pulse events 1A (about 14 ka) and 1B (about 11 ka) and stayed high in the Holocene. Spatial and temporal distributions of the phytoplankton productivity were found to be consistent with changes in the reconstructed sea ice distribution on the basis of the IRD. This demonstrates that the progress and retreat of sea ice regulated primary productivity in the Sea of Okhotsk with minimum productivity during the glacial period. The mass accumulation rates of alkenones, CaCO3, and biogenic opal indicate that the dominant phytoplankton species during deglaciation was the coccolithophorid, Emiliania huxleyi, which was replaced by diatoms in the late Holocene. Such a phytoplankton succession was probably caused by an increase in silicate supply to the euphotic layer, possibly associated with a change in surface hydrography and/or linked to enhanced upwelling of North Pacific Deep Water.

Air-sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

We present air–sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27m above mean sea level, a.m.s.l.), each from a different period during 2014–2015. At sampling heights ≥18ma.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable (≤ ±20% in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20±3; 38±3; 29±6 μmolem-2 d-1 at 15, 18, 27ma.m.s.l.) than during falling tides (14±2; 22±2; 21±5 μmolem-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 μmolem-2 d-1 over hourly timescales (4 μmolem-2 d-1 over 24 h).

Air-sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

We present air–sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27m above mean sea level, a.m.s.l.), each from a different period during 2014–2015. At sampling heights ≥18ma.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable (≤ ±20% in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20±3; 38±3; 29±6 μmolem-2 d-1 at 15, 18, 27ma.m.s.l.) than during falling tides (14±2; 22±2; 21±5 μmolem-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 μmolem-2 d-1 over hourly timescales (4 μmolem-2 d-1 over 24 h).

Assessment of sea-level variability for the Emilia-Romagna coastal area in the framework of the Mediterranean Sea

Sea–level change is one of the ocean characteristics closely connected to climate change. Understanding its variation is essential since a large portion of the world’s population is located in low–lying locations. Two main techniques are employed to measure sea level: satellite altimetry and tide gauges. Satellite altimetry monitors sea–level relative to a geocentric reference, is unaffected by crustal processes and covers nearly the entire surface of the oceans since 1993. Conversely, tide gauges measure sea level at specific coastal locations and relative to a local ground benchmark, therefore are impacted by vertical land movements. In this study, the linear and non–linear geocentric and relative sea–level trends along the Emilia–Romagna coast (Northern Italy) have been analyzed over different periods. In order to assess the local sea–level variability, data from satellite altimetry and tide gauges have been compared over a common time interval (1993–2019), hence disentangling the contribute of vertical land movements. Non–linearity has been also evaluated at the broader scale of the Mediterranean Sea, in order to depict the main variability in geocentric sea–level trends from regional to sub–basin scale. Furthermore, the anthropogenic and natural influence at the river basin scale has been addressed, in order to shed light on the factors inducing the drastic reduction of riverine sediment supply to the Emilia–Romagna coast over the period 1920–2020. The findings of this analysis indicate that the sediment delivery reduction to the coast by rivers has been driven by several anthropogenic processes, acting on various spatiotemporal scales. Moreover, the local absolute sea–level trend is far from linear and appear "contaminated" by the presence of natural oscillations that act at the multi–decadal, quasi–decadal and inter–annual scale, mainly driven by both large–scale climatic modes and variations in local oceanography.

Atopic dermatitis in adults: evaluation of peripheral blood mononuclear cells proliferation response to Staphylococcus aureus enterotoxins A and B and analysis of interleukin-18 secretion

Atopic dermatitis (AD) is a chronic, inflammatory skin disease with a high prevalence and complex pathogenesis. The skin of AD patients is usually colonized by Staphylococcus aureus (S. aureus); its exotoxins may trigger or enhance the cutaneous inflammation. Several mediators are related to the AD immune imbalance and interleukin-18 (IL-18), an inflammatory cytokine, may play a role in the atopic skin inflammation. To evaluate peripheral blood mononuclear cells (PBMC) proliferation response to staphylococcal enterotoxins A (SEA) and B (SEB) and the levels of IL-18 in adults with AD. Thirty-eight adult patients with AD and 33 healthy controls were analysed. PBMC were stimulated with SEA and SEB, phytohemaglutinin (PHA), pokeweed (PWM), tetanus toxoid (TT) and Candida albicans (CMA). IL-18 secretion from PBMC culture supernatants and sera were measured by ELISA. A significant inhibition of the PBMC proliferation response to SEA, PHA, TT and CMA of AD patients was detected (P <= 0.05). Furthermore, increased levels of IL-18 were detected both in sera and non-stimulated PBMC culture supernatants from AD patients (P <= 0.05). A decreased PBMC proliferation response to distinct antigens and mitogens (TT, CMA, SEA and PHA) in adults with AD suggest a compromised immune profile. IL-18 secretion from AD upon stimulation was similar from controls, which may indicate a diverse mechanism of skin inflammation maintained by Staphylococcus aureus. On the other hand, augmented IL-18 secretion from AD sera and non-stimulated cell culture may enhance the immune dysfunction observed in AD, leading to constant skin inflammation.

Use of Acoustic Doppler Sonography to Ascertain the Feasibility of the Pedicled Nasoseptal Flap After Prior Bilateral Sphenoidotomy

Objectives/Hypothesis: Blood supply to the Hadad-Bassagasteguy pedicled nasoseptal flap may be interrupted by surgery of the pterygopalatine fossa, posterior septectomy, or large sphenoidotomies. This would preclude its use for reconstruction of skull base defects after expanded endonasal approaches (EEA). We present a novel method to ascertain the patency of the nasoseptal artery after prior surgery, and consequently the availability of the nasoseptal flap, using acoustic Doppler sonography. Study Design: Retrospective clinical review. Methods: Four patients who underwent EEAs were evaluated intraoperatively with acoustic Doppler sonography. The mucosa that covers the inferior aspect of the rostrum of the sphenoid sinus was scanned with the tip of the probe. Reflection of sound waves representing intravascular blood flow was assessed. Results: In three patients, the artery was identified in at least one side. One remaining patient showed no acoustic signal suggesting loss of the nasoseptal artery bilaterally, therefore necessitating the use of a fat graft for the reconstruction. Conclusions: Acoustic Doppler sonography seems to be a feasible and effective way to ascertain the availability of the nasoseptal artery. It is a relatively inexpensive and simple technique that can be performed by any endoscopic surgeon.