ALBERT

Description: Greenhouse gas emission studies from Coral Reef settings remain sparce compared to open ocean, rivers, and estuaries. Here we sampled the greenhouse gases of carbon dioxide (CO2) with isotopic fractions (δ13C-CO2), methane (CH4) with isotopic fractions (δ13C-CH4), and nitrous oxide (N2O) in high resolution (905 individual georeferenced 5 minute averaged samples) from ship based cruises throughout the southern half of the Great Barrier Reef Australia. Time and location matched high-resolution physio-chemical data (salinity, temperature, dissolved oxygen, turbidity and chlorophyll a) were also measured to determine driving factors of greenhouse gases in the lagoon. Overall, the lagoon was oversaturated in CO2 which is consistent with previous coral reef area studies. CH4 was also oversaturated despite highly oxygenated waters that are normally unconducive for CH4 production. N2O was undersaturated and up-taking N2O from the atmosphere which contrasts with the few coral reef and continental shelf area studies. Dissolved greenhouse gases were measured with a Picarro G2201-i Cavity Ring Down Spectrometer for CO2 (200 ppb ±0.05%) and CH4 (5 ppb ± 0.05%) with respective δ12C and δ13C stable isotope fractions and a Picarro G2308 Cavity Ring Down Spectrometer for N2O concentrations (〈3.5 ppb ± 0.008%). Both Cavity Ring Down Spectrometer instruments were connected in a closed loop with twin showerhead exchangers and a gas drying agent (Drierite). The showerhead exchangers received seawater from the vessel cold water intake. Both instruments averaged 300 measurements over a five-minute cycle for each greenhouse gas sample. Salinity, temperature, and turbidity were also recorded at the inlet of the seawater system with a Seabird SBE 21 (salinity ± 0.005 psu, temperature ± 0.002 °C, turbidity ± 0.04% NTU). Dissolved oxygen, pH, and Chlorophyll were recorded using respective Hydrolab MS5 multi-parameter sonde (dissolved oxygen 0.1 ± 0.02 mg L-1), SAMI-pH (〈0.001 ± 0.003 pH units) and ECO 3-Triplet fluorometer (Chl-a 0.016 ± 0.025 μg L-1) instruments fitted with inline flow cells.

Description: This dataset provides discrete nutrient, dissolved and greenhouse gas samples collected during ship-based cruises in the southern Great Barrier Reef lagoon, Australia. Here we sampled the greenhouse gases of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) with time matched (georeferenced samples) discrete nutrient measurements (dissolved organic carbon, ammonium, nitrate, dissolved inorganic nitrogen, total nitrogen and phosphate) collected from the lagoon. Nutrient concentrations remained low overall, while the lagoon was oversaturated in CO2 and CH4 despite highly oxygenated waters that are normally unconducive for CH4 production. N2O was also undersaturated in the oligotrophic conditions. Dissolved greenhouse gases were measured with a Picarro G2201-i Cavity Ring Down Spectrometer for CO2 (200 ppb ±0.05%) and CH4 (5 ppb ± 0.05%) and a Picarro G2308 Cavity Ring Down Spectrometer for N2O concentrations (〈3.5 ppb ± 0.008%). Both Cavity Ring Down Spectrometer instruments were connected in a closed loop with twin showerhead exchangers and a gas drying agent (Drierite). The showerhead exchangers received seawater from the vessel cold water intake. Both instruments averaged 300 measurements over a five-minute cycle for each greenhouse gas sample. Salinity and temperature were recorded at the inlet of the seawater intake system with a Seabird SBE 21 (salinity ± 0.005 psu, temperature ± 0.002 °C). Dissolved oxygen was also recorded using a Hydrolab MS5 (dissolved oxygen 0.1 ± 0.02 mg L-1) fitted with an inline flow cell. Discrete nutrient and dissolved organic carbon (DOC) water samples were collected along survey transects using Niskin bottles from a depth of ⁓3 m. Dissolved nutrient samples were collected by filtering sample water through cellulose acetate syringe filters (0.45 µm) into sample rinsed 12 mL polypropylene vials before immediate freezing until laboratory analysis. Nutrient concentrations were determined using a Lachat QuickChem 8500 Flow Injection Analyser [Detection limits were 0.07 μmol ± 0.3% for nitrate (NOx-) and 0.35 μmol ± 5% for ammonium (NH4+)]. DOC samples were collected by filtering sample water through Whatman G/FF syringe filters (0.7 μm) into 40 ml pre-treated (100 μL mercuric chloride) VOC vials before immediate refrigeration until laboratory analysis. DOC concentrations were determined with OI Aurora 1030 W TOC Analyzer.

Description: These data were compiled from original and published datasets of coastal groundwater / subterranean estuary research efforts along global coastline (sites within 1km of shoreline). The dataset includes sampling site names, locations, original sample information, sample depth, temperature, salinity, dissolved nitrogen concentrations, and dissolved phosphorus concentrations. The data source or curator is also included in the dataset.

Description: Concentrations of alkalinity (TA) and dissolved inorganic carbon (DIC) in porewater as well as in surface water measured during timeseries (fixed location) and spatial surveys (fixed time period) were compiled from 38 mangrove- and 8 saltmarsh-dominated creeks and estuaries. We used data from creeks that were predominantly surrounded by mangrove or saltmarsh vegetation and with minimal confounding factors such as mixed vegetation or large catchments. These creeks were located in either pristine or anthropologically impacted estuaries or coastal areas. Anthropologically impacted areas were defined as areas that were affected by nearby urban or agricultural activities, potentially delivering pollutants, e.g., sewage or fertilizers, to creeks. We also included pristine mangrove- and saltmarsh dominated estuaries. When available, environmental parameters were also recorded, i.e., season, salinity, temperature, pH, dissolved oxygen (DO), water level, porewater tracer radon (222Rn), partial pressure of carbon dioxide (pCO2), dissolved organic carbon (DOC), particulate organic carbon (POC), nitrate and nitrite (NOx), ammonium (NH4), total nitrogen (TN), phosphate (PO4), and total phosphorus (TP). Methods used to determine parameters are explained in each corresponding reference.

Description: Anchialine caves are common in Mediterranean karstic shorelines and elsewhere, delivering point-source fresh groundwater and nutrients to the coastal ocean. Here, we first quantified submarine groundwater discharge (SGD) in a typical karstic system (Zaton Bay, Croatia) receiving groundwater from anchialine caves using a radon (222Rn) mass balance model. We then combine our new observations with the literature to provide a Mediterranean-scale estimate of karstic fresh SGD nutrient fluxes. We found that SGD and related nutrient fluxes in the upper brackish layer were much higher than those in the underlying layer in Zaton Bay. In the upper brackish layer, both SGD (m d−1) and associated nutrient fluxes (mmol m−2 d−1) in the wet season (SGD: 0.29–0.40; DIN: 52; DIP: 0.27) were significantly higher than those in the dry season (SGD: 0.15; DIN: 22; DIP: 0.08). Red tides were observed in the wet season but not in the dry season. Nutrient budgets imply that SGD accounted for 〉98% of the total dissolved inorganic nitrogen (DIN) and phosphorous (DIP) sources into Zaton Bay. These large SGD nutrient fluxes with high N/P ratios (190–320) likely trigger and sustain red tide outbreaks. Combining our results with 30 previous studies in the region revealed that point-source DIN and DIP fluxes via karstic fresh SGD may account for 8–31% and 1–4%, respectively, of riverine inputs in the Mediterranean Sea. Overall, we demonstrate the importance of karstic SGD as a source of new nutrients with high N/P ratios to the Mediterranean Sea and emphasize how SGD lagging precipitation can drive red tide outbreaks.

Description: Lateral fluxes (i.e., outwelling) of dissolved organic (DOC) and inorganic (DIC) carbon and total alkalinity were estimated using radium isotopes at the groundwater, mangrove creek, and continental shelf scales in the Amazon region. Observations of salinity and radium isotopes in the creek indicated tidally driven groundwater exchange as the main source of carbon. Radium-derived transport rates indicate that mangrove carbon is exported out of the continental shelf on timescales of 22 ± 7 d. Bicarbonate was the main form (82% ± 11%) of total dissolved carbon in all samples, followed by DOC (13% ± 12%) and CO2 (5% ± 4%). DIC (18.7 ± 15.7 mmol m−2 d−1) exceeded DOC (3.0 ± 4.1 mmol m−2 d−1) outwelling at all spatial scales. The interpretation of outwelling across the mangrove-ocean continuum is related to the spatial and temporal scales investigated. At all scales, outwelling represented a major coastal carbon pathway driving bicarbonate storage in the ocean.