Excitation-emission matrix (EEM) fluorescence was combined with parallel factor analysis (PARAFAC) to model base-extracted particulate (POM) and dissolved (DOM) organic matter quality in the Neuse River Estuary (NRE), North Carolina, before and after passage of Hurricane Irene in August 2011. Principle components analysis was used to determine that four of the PARAFAC components (C1-C3 and C6) were terrestrial sources to the NRE. One component (C4), prevalent in DOM of nutrient-impacted streams and estuaries and produced in phytoplankton cultures, was enriched in the POM and in surface sediment pore water DOM. One component (C5) was related to recent autochthonous production. Photoexposure of unfiltered Neuse River water caused an increase in slope ratio values (S(R)) which corresponded to an increase in the ratio C2:C3 for DOM, and the production of C4 fluorescence in both POM and DOM. Changes to the relative abundance of C4 in POM and DOM indicated that advection of pore water DOM from surface sediments into overlying waters could increase the autochthonous quality of DOM in shallow microtidal estuaries. Modeling POM and DOM simultaneously with PARAFAC is an informative technique that is applicable to assessments of estuarine water quality.

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Dissolved organic matter (DOM) absorbance and fluorescence were used as optical proxies to track terrestrial DOM fluxes through estuaries and coastal waters by comparing models developed for several coastal ecosystems. Key to using these optical properties is validating and calibrating them with chemical measurements, such as lignin-derived phenols-a proxy to quantify terrestrial DOM. Utilizing parallel factor analysis (PARAFAC), and comparing models statistically using the OpenFluor database (http://www.openfluor.org) we have found common, ubiquitous fluorescing components which correlate most strongly with lignin phenol concentrations in several estuarine and coastal environments. Optical proxies for lignin were computed for the following regions: Mackenzie River Estuary, Atchafalaya River Estuary (ARE), Charleston Harbor, Chesapeake Bay, and Neuse River Estuary (NRE) (all in North America). The slope of linear regression models relating CDOM absorption at 350 nm (a 350) to DOC and to lignin, varied 5-10-fold among systems. Where seasonal observations were available from a region, there were distinct seasonal differences in equation parameters for these optical proxies. The variability appeared to be due primarily to river flow into these estuaries and secondarily to biogeochemical cycling of DOM within them. Despite the variability, overall models using single linear regression were developed that related dissolved organic carbon (DOC) concentration to CDOM (DOC 2 = 40 ± 2 × a + ± 350 138 16; R = 0.77; N = 130) and lignin (8) to CDOM (= 2.03 ± 0.07 × a .47 2 − 0 ± = 8 350 0.59; R 0.87; N = 130). This wide variability suggested that local or regional optical models should be developed for predicting terrestrial DOM flux into coastal oceans and taken into account when upscaling to remote sensing observations and calibrations.

Although the seepage meter has been widely used in limnology, measurement errors are commonly ignored. These errors result in the need for meter correction factors due to flow field deflection and frictional resistance and head losses within the meter and prefilled bags to avoid short‐term influx of water caused by the pulling action of deformed bags. Tank‐test data indicate a ratio of measured to actual inseepage of 0.77 (at inseepage rates <20 mm h−1), with a ratio of meter to interstitial seepage flux of 0.50. Provided these precautions are observed and the adjustment factor is applied, field test “point estimates” of seepage inflow with replicate seepage meters generally have relative root‐mean‐square error(s) <20%. Data from measurements at single locations in tank tests indicate a constant bias and show that, once installed, the actual instrument error is even less (∼5%). These errors are small compared to spatial and temporal components of sampling error typically encountered in the field.

Moderate elevated vertical methane (CH 4 ) flux is associated with sediment accretion and raised fluid expulsion at the Hikurangi subduction margin, located along the northeast coast of New Zealand. This focused CH 4 flux contributes to the cycling of inorganic and organic carbon in solid phase sediment and pore water. Along a 7 km offshore transect across the Porangahau Ridge, vertical CH 4 flux rates range from 11.4 mmol·m −2 ·a −1 off the ridge to 82.6 mmol·m −2 ·a −1 at the ridge base. Stable carbon isotope ratios (δ 13 C) in pore water and sediment were variable across the ridge suggesting close proximity of heterogeneous OPEN ACCESSEnergies 2014, 7 5333 carbon sources. Methane stable carbon isotope ratios ranging from −107.9‰ to −60.5‰ and a C1:C2 of 3000 indicate a microbial, or biogenic, source. Near ridge, average δ 13 C for pore water and sediment inorganic carbon were 13 C-depleted (−28.7‰ and −7.9‰, respectively) relative to all core subsamples (−19.9‰ and −2.4‰, respectively) suggesting localized anaerobic CH 4 oxidation and precipitation of authigenic carbonates. Through the transect there was low contribution from anaerobic oxidation of CH 4 to organic carbon pools; for all cores δ 13 C values of pore water dissolved organic carbon and sediment organic carbon averaged −24.4‰ and −22.1‰, respectively. Anaerobic oxidation of CH 4 contributed to pore water and sediment organic carbon near the ridge as evidenced by carbon isotope values as low as to −42.8‰ and −24.7‰, respectively. Carbon concentration and isotope analyses distinguished contributions from CH 4 and phytodetrital carbon sources across the ridge and show a low methane contribution to organic carbon.