Chemical characteristics of dissolved organic matter in an oligotrophic subtropical wetland/estuarine ecosystem

Fluorescence properties of whole water samples and molecular characteristics of ultrafiltrated dissolved organic matter (UDOM > 1,000 D) such as lignin phenol and neutral sugar compositions and 13C nuclear magnetic resonance (NMR) spectra were determined along a freshwater to marine gradient in Everglades National Park. Furthermore, UDOM samples were categorized by hierarchical cluster analysis based on their pyrolysis gas chromatography/mass spectrometry products. Fluorescence properties suggest that autochthonous DOM leached/exuded from biomass is quantitatively important in this system. 13C NMR spectra showed that UDOM from the oligotrophic Taylor Slough (TS) and Florida Bay (FB) ecosystems has low aromatic C (13% ± 3% for TS; 2% ± 2% for FB) and very high O-alkyl C (54% ± 4% for TS; 75% ± 4% for FB) concentrations. High O-alkyl C concentrations in FB suggest seagrass/phytoplankton communities as dominant sources of UDOM. The amount of neutral sugars was not appreciably different between the TS and FB sites (115 ± 12 mg C g C-1 UDOM) but their concentrations suggest a low level of diagenesis and high production rates of this material in this oligotrophic environment. Total yield of lignin phenols (vanillyl + syringyl phenols) in TS was low (0.20–0.39 mg 100 mg C-1 UDOM) compared with other riverine environments and even lower in FB (0.04–0.07 mg 100 mg C-1 UDOM) and could be a result of photodegradation and/or dilution by other utochthonous DOM. The high O-alkyl and low aromatic nature of this UDOM suggests significant biogenic inputs (as compared with soils) and limited bioavailability in this ecosystem.

Benthic Exchange of C, N, and P Along the Estuarine Ecotone of Lower Taylor Slough, Florida (USA): Effect of Seasonal Flows and Phosphorus Availability

The southern Everglades and Florida Bay have experienced a nearly 50 % reduction in freshwater flow resulting in increased salinity and landward expansion of mangrove forest. Given the marine end-member is a natural source of P to this region, it is necessary to understand the interactions between inflows and P availability in controlling the exchange of materials across the mangrove ecotone. From 2007 to 2008, we used sediment core incubations to quantify fluxes of dissolved inorganic N and P and dissolved organic carbon (DOC) in three ecotone areas (dwarf mangrove, pond, and bay). Experiments were repeated seasonally over 2 years involving P-enriched surface water as a factor. We saw consistent uptake of soluble reactive P (SRP), DOC, and nitrate + nitrite (N+N) by the soils/sediments and release of ammonium (NH4 +) from soils/sediments to the water column across all sites and seasons. P enrichment had no discernible effect on DIN or DOC flux, suggesting that rapid P uptake may have been more geochemically mediated. However, uptake of added P occurred across all sites and seasons, reflecting high uptake capacity in this carbonate system and the potential of the mangrove ecotone to sequester P as it becomes more available.

Effects of an extreme temperature event on the behavior and age structure of an estuarine top predator, Carcharhinus leucas

The frequency of extreme environmental events is predicted to increase in the future. Understanding the short- and long-term impacts of these extreme events on large-bodied predators will provide insight into the spatial and temporal scales at which acute environmental disturbances in top-down processes may persist within and across ecosystems. Here, we use long-term studies of movements and age structure of an estuarine top predator—juvenile bull sharks Carcharhinus leucas—to identify the effects of an extreme ‘cold snap’ from 2 to 13 January 2010 over short (weeks) to intermediate (months) time scales. Juvenile bull sharks are typically year-round residents of the Shark River Estuary until they reach 3 to 5 yr of age. However, acoustic telemetry revealed that almost all sharks either permanently left the system or died during the cold snap. For 116 d after the cold snap, no sharks were detected in the system with telemetry or captured during longline sampling. Once sharks returned, both the size structure and abundance of the individuals present in the nursery had changed considerably. During 2010, individual longlines were 70% less likely to capture any sharks, and catch rates on successful longlines were 40% lower than during 2006−2009. Also, all sharks caught after the cold snap were young-of-the-year or neonates, suggesting that the majority of sharks in the estuary were new recruits and several cohorts had been largely lost from the nursery. The longer-term impacts of this change in bull shark abundance to the trophic dynamics of the estuary and the importance of episodic disturbances to bull shark population dynamics will require continued monitoring, but are of considerable interest because of the ecological roles of bull sharks within coastal estuaries and oceans.

Macroinvertebrate abundance in tropical Andean streams, Ecuador

Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Overall, our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. Also, this research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

Qualidade do solo da camada de cobertura final em área de disposição de resíduos no semiárido tropical

The final disposal of municipal solid waste in unsuitable areas without an infrastructure that meets the health measures and environmental protection, coupled with the lack of technical criteria in phase and decommissioning of the dump can promote environmental degradation. Alternatively to minimize the impacts of this activity for the stabilization of the area by isolating the massive waste with implementation of an adequate and finished by a layer of soil for plant growth final cover system. In this context, the present study aimed to evaluate the quality of the final cover in the area of a disabled dump the tropical semi-arid region in order to assist the process of recovery of these areas. The study area is located in the tropical semi-arid region in São João do Sabugi /RN. Soil samples were collected in the dump area and bushland as a benchmark of quality. To which they were subjected to analysis of physical attributes (particle density, bulk density, grain size and porosity), chemical properties (pH, K + , Na+ , Ca2 + , Mg2 + and Al3 + exchangeable, potential acidity, available phosphorus, sum of bases, CEC, base saturation, aluminum saturation, saturation Na + and adsorption ratio sodium, total organic carbon and total nitrogen) and total and soluble concentrations of heavy metals (Mn, Pb, Zn, Cd, Cu, Mo, Co, Cr, Ba and Ni). The differences between physical and chemical soil under native forest and final cover showing reduction of soil quality in the area off to the dump, which hinders the development of native vegetation and the recovery of the area. The absence of superior waterproofing to allow vertical transfer between the solid waste and the final cover promoted enrichment by chemical elements and heavy metals in excess can impair revegetation. Deficiencies found in the construction process of the final cover point to the need for intervention to accelerate the process of stabilization and recovery of the area of the local ecosystem

Seawater carbonate chemistry and calcification in the tropical urchin Echinometra viridis in a laboratory experiment

Atmospheric carbon dioxide (pCO2) has risen from approximately 280 to 400 ppm since the Industrial Revolution, due mainly to the combustion of fossil fuels, deforestation, and cement production. It is predicted to reach as high as 900 ppm by the end of this century. Ocean acidification resulting from the release of anthropogenic CO2 has been shown to impair the ability of some marine calcifiers to build their shells and skeletons. Here, we present the results of ocean acidification experiments designed to assess the effects of an increase in atmospheric pCO2 from ca. 448 to 827 ppm on calcification rates of the tropical urchin Echinometra viridis. Experiments were conducted under the urchin's winter (20 °C) and summer (30 °C) water temperatures in order to identify seasonal differences in the urchin's response to ocean acidification. The experiments reveal that calcification rates decreased for urchins reared under elevated pCO2, with the decline being more pronounced under wintertime temperatures than under summertime temperatures. These results indicate that the urchin E. viridis will be negatively impacted by CO2-induced ocean acidification that is predicted to occur by the end of this century. These results also suggest that impact of CO2-induced ocean acidification on urchin calcification will be more severe in the winter and in cooler waters.

Surface wind stress modeled for the Panama Seaway with the Community Climate System Model 3

The early Pliocene warm phase was characterized by high sea surface temperatures and a deep thermocline in the eastern equatorial Pacific. A new hypothesis suggests that the progressive closure of the Panamanian seaway contributed substantially to the termination of this zonally symmetric state in the equatorial Pacific. According to this hypothesis, intensification of the Atlantic meridional overturning circulation (AMOC) - induced by the closure of the gateway - was the principal cause of equatorial Pacific thermocline shoaling during the Pliocene. In this study, twelve Panama seaway sensitivity experiments from eight ocean/climate models of different complexity are analyzed to examine the effect of an open gateway on AMOC strength and thermocline depth. All models show an eastward Panamanian net throughflow, leading to a reduction in AMOC strength compared to the corresponding closed-Panama case. In those models that do not include a dynamic atmosphere, deepening of the equatorial Pacific thermocline appears to scale almost linearly with the throughflow-induced reduction in AMOC strength. Models with dynamic atmosphere do not follow this simple relation. There are indications that in four out of five models equatorial wind-stress anomalies amplify the tropical Pacific thermocline deepening. In summary, the models provide strong support for the hypothesized relationship between Panama closure and equatorial Pacific thermocline shoaling.

Ammonium excretion and respiration rate of tropical copepods and euphausiids measured during METEOR cruise M93, M97 and Maria S. Merian cruise MSM22

Respiration and ammonium excretion rates at different oxygen partial pressure were measured for calanoid copepods and euphausiids from the Eastern Tropical South Pacific and the Eastern Tropical North Atlantic. All specimens used for experiments were caught in the upper 400 m of the water column and only animals appearing unharmed and fit were used for experiments. Specimens were sorted, identified and transferred into aquaria with filtered, well-oxygenated seawater immediately after the catch and maintained for 1 to 13 hours prior to physiological experiments at the respective experimental temperature. Maintenance and physiological experiments were conducted in darkness in temperature-controlled incubators at 11, 13 or 23 degree C (±1). Before and during experiments, animals were not fed. Respiration and ammonium excretion rate measurements (both in µmol h-1 gDW-1) at varying oxygen concentrations were conducted in 12 to 60 mL gas-tight glass bottles. These were equipped with oxygen microsensors (ø 3 mm, PreSens Precision Sensing GmbH, Regensburg, Germany) attached to the inner wall of the bottles to monitor oxygen concentrations non-invasively. Read-out of oxygen concentrations was conducted using multi-channel fiber optic oxygen transmitters (Oxy-4 and Oxy-10 mini, PreSens Precision Sensing GmbH, Regensburg, Germany) that were connected via optical fibers to the outside of the bottles directly above the oxygen microsensor spots. Measurements were started at pre-adjusted oxygen and carbon dioxide levels. For this, seawater stocks with adjusted pO2 and pCO2 were prepared by equilibrating 3 to 4 L of filtered (0.2 µm filter Whatman GFF filter) and UV - sterilized (Aqua Cristal UV C 5 Watt, JBL GmbH & Co. KG, Neuhofen, Germany) water with premixed gases (certified gas mixtures from Air Liquide) for 4 hours at the respective experimental temperature. pCO2 levels were chosen to mimic the environmental pCO2 in the ETSP OMZ or the ETNA OMZ. Experimental runs were conducted with 11 to 15 trial incubations (1 or 2 animals per incubation bottle and three different treatment levels) and three animal-free control incubations (one per experimental treatment). During each run, experimental treatments comprised 100% air saturation as well as one reduced air saturation level with and without CO2. Oxygen concentrations in the incubation bottles were recorded every 5 min using the fiber-optic microsensor system and data recording for respiration rate determination was started immediately after all animals were transferred. Respiration rates were calculated from the slope of oxygen decrease over selected time intervals. Chosen time intervals were 20 to 105 min long. No respiration rate was calculated for the first 20 to 60 min after animal transfer to avoid the impact of enhanced activity of the animal or changes in the bottle water temperature during initial handling on the respiration rates and oxygen readings. Respiration rates were obtained over a maximum of 16 hours incubation time and slopes were linear at normoxia to mild hypoxia. Respiration rates in animal-free control bottles were used to correct for microbial activity. These rates were < 2% of animal respiration rates at normoxia. Samples for the measurement of ammonium concentrations were taken after 2 to 10 hours incubation time. Ammonium concentration was determined fluorimetrically (Holmes et al., 1999). Ammonium excretion was calculated as the concentration difference between incubation and animal-free control bottles. Some specimens died during the respiration and excretion rate measurements, as indicated by a cessation of respiration. No excretion rate measurements were conducted in this case, but the oxygen level at which the animal died was noted.

Seawater carbonate chemistry and calcification during a tropical lagoon study at SW lagoon, New Caledonia, 1991

A selective chemical photosynthesis inhibitor, DCMU (Dichorophenyl-dimethylurea), dissolved in DMSO (Dimethyl sulfoxide) was substituted for the dark incubation method commonly used to measure the oxygen consumption in metabolic and primary production studies. We compared oxygen fluxes during light incubations with DCMU and dark incubations procedure, on soft bottom benthos. For this purpose, we studied the effects of different DCMU concentrations. A concentration of 5 · 10-5 mol l-1 inside a clear incubation enclosure completely inhibits photosynthesis without affecting the metabolism of soft bottom benthos.

Seawater carbonate chemistry and calcification during tropical reef studies at Moorea (French Polynesia), 1996

Community metabolism was investigated using a Lagrangian flow respirometry technique on 2 reef flats at Moorea (French Polynesia) during austral winter and Yonge Reef (Great Barrier Reef) during austral summer. The data were used to estimate related air-sea CO2 disequilibrium. A sine function did not satisfactorily model the diel light curves and overestimated the metabolic parameters. The ranges of community gross primary production and respiration (Pg and R; 9 to 15 g C m-2 d-1) were within the range previously reported for reef flats, and community net calcification (G; 19 to 25 g CaCO3 m-2 d-1) was higher than the 'standard' range. The molar ratio of organic to inorganic carbon uptake was 6:1 for both sites. The reef flat at Moorea displayed a higher rate of organic production and a lower rate of calcification compared to previous measurements carried out during austral summer. The approximate uncertainty of the daily metabolic parameters was estimated using a procedure based on a Monte Carlo simulation. The standard errors of Pg,R and Pg/R expressed as a percentage of the mean are lower than 3% but are comparatively larger for E, the excess production (6 to 78%). The daily air-sea CO2 flux (FCO2) was positive throughout the field experiments, indicating that the reef flats at Moorea and Yonge Reef released CO2 to the atmosphere at the time of measurement. FCO2 decreased as a function of increasing daily irradiance.

Seawater carbonate chemistry and calcification during tropical reef studies at Younge reef (Great Barrier Reef), 1996

Community metabolism was investigated using a Lagrangian flow respirometry technique on 2 reef flats at Moorea (French Polynesia) during austral winter and Yonge Reef (Great Barrier Reef) during austral summer. The data were used to estimate related air-sea CO2 disequilibrium. A sine function did not satisfactorily model the diel light curves and overestimated the metabolic parameters. The ranges of community gross primary production and respiration (Pg and R; 9 to 15 g C m-2 d-1) were within the range previously reported for reef flats, and community net calcification (G; 19 to 25 g CaCO3 m-2 d-1) was higher than the 'standard' range. The molar ratio of organic to inorganic carbon uptake was 6:1 for both sites. The reef flat at Moorea displayed a higher rate of organic production and a lower rate of calcification compared to previous measurements carried out during austral summer. The approximate uncertainty of the daily metabolic parameters was estimated using a procedure based on a Monte Carlo simulation. The standard errors of Pg,R and Pg/R expressed as a percentage of the mean are lower than 3% but are comparatively larger for E, the excess production (6 to 78%). The daily air-sea CO2 flux (FCO2) was positive throughout the field experiments, indicating that the reef flats at Moorea and Yonge Reef released CO2 to the atmosphere at the time of measurement. FCO2 decreased as a function of increasing daily irradiance.

Dissolved Iron, Aluminium, and Dissolved Inorganic Phosphorus in the (Sub-)Tropical Atlantic Surface Ocean

Inorganic nitrogen depletion restricts productivity in much of the low-latitude oceans, generating a selective advantage for diazotrophic organisms capable of fixing atmospheric dinitrogen (N2). However, the abundance and activity of diazotrophs can in turn be controlled by the availability of other potentially limiting nutrients, including phosphorus (P) and iron (Fe). Here we present high-resolution data (~0.3°) for dissolved iron, aluminum, and inorganic phosphorus that confirm the existence of a sharp north-south biogeochemical boundary in the surface nutrient concentrations of the (sub)tropical Atlantic Ocean. Combining satellite-based precipitation data with results from a previous study, we here demonstrate that wet deposition in the region of the intertropical convergence zone acts as the major dissolved iron source to surface waters. Moreover, corresponding observations of N2 fixation and the distribution of diazotrophic Trichodesmium spp. indicate that movement in the region of elevated dissolved iron as a result of the seasonal migration of the intertropical convergence zone drives a shift in the latitudinal distribution of diazotrophy and corresponding dissolved inorganic phosphorus depletion. These conclusions are consistent with the results of an idealized numerical model of the system. The boundary between the distinct biogeochemical systems of the (sub)tropical Atlantic thus appears to be defined by the diazotrophic response to spatial-temporal variability in external Fe inputs. Consequently, in addition to demonstrating a unique seasonal cycle forced by atmospheric nutrient inputs, we suggest that the underlying biogeochemical mechanisms would likely characterize the response of oligotrophic systems to altered environmental forcing over longer timescales.

Seawater carbonate chemistry and calcification during a tropical lagoon study at SW lagoon of New Caledonia, 1994

Carbon dioxide and oxygen fluxes were measured in 0.2 m2 enclosures placed at the water sediment interface in the SW lagoon of New Caledonia. Experiments, performed at several stations in a wide range of environments, were carried out both in darkness to estimate respiration and at ambient light, to assess the effects of primary production. The community respiratory quotient (CRQ = CO2 production rate/02 consumption rate) and the community photosynthetic quotient (CPQ= gross O2 production rate/gross CO2 consumption rate) were calculated by functional regressions. The CRQ value, calculated from 61 incubations, was 1.14 (S.E. 0.05) and the CPQ value, obtained from 18 incubations, was 1.03 (S.E. 0.08). The linearity of the relationship between the O2 and the CO2 fluxes suggests that these values are representative for the whole lagoon

Revisiting the Late Jurassic-Early Cretaceous of the NW South Iberian Basin: new ages and sedimentary environments

The study of the Upper Jurassic-Lower Cretaceous deposits (Higueruelas, Villar del Arzobispo and Aldea de Cortés Formations) of the South Iberian Basin (NW Valencia, Spain) reveals new stratigraphic and sedimentological data, which have significant implications on the stratigraphic framework, depositional environments and age of these units. The Higueruelas Fm was deposited in a mid-inner carbonate platform where oncolitic bars migrated by the action of storms and where oncoid production progressively decreased towards the uppermost part of the unit. The overlying Villar del Arzobispo Fm has been traditionally interpreted as an inner platform-lagoon evolving into a tidal-flat. Here it is interpreted as an inner-carbonate platform affected by storms, where oolitic shoals protected a lagoon, which had siliciclastic inputs from the continent. The Aldea de Cortés Fm has been previously interpreted as a lagoon surrounded by tidal-flats and fluvial-deltaic plains. Here it is reinterpreted as a coastal wetland where siliciclastic muddy deposits interacted with shallow fresh to marine water bodies, aeolian dunes and continental siliciclastic inputs. The contact between the Higueruelas and Villar del Arzobispo Fms, classically defined as gradual, is also interpreted here as rapid. More importantly, the contact between the Villar del Arzobispo and Aldea de Cortés Fms, previously considered as unconformable, is here interpreted as gradual. The presence of Alveosepta in the Villar del Arzobispo Fm suggests that at least part of this unit is Kimmeridgian, unlike the previously assigned Late Tithonian-Middle Berriasian age. Consequently, the underlying Higueruelas Fm, previously considered Tithonian, should not be younger than Kimmeridgian. Accordingly, sedimentation of the Aldea de Cortés Fm, previously considered Valangian-Hauterivian, probably started during the Tithonian and it may be considered part of the regressive trend of the Late Jurassic-Early Cretaceous cycle. This is consistent with the dinosaur faunas, typically Jurassic, described in the Villar del Arzobispo and Aldea de Cortés Fms.