The sources and cycling of organic matter on 2 mudflats in the Huon Estuary, SE Tasmania, were investigated over 4 seasons using pigment and lipid biomarkers as well as stable isotopes of carbon and nitrogen; 1 site was in the upper estuary,1 site was in a marine side-arm. The organic matter within the sediments at both sites was dominated by terrestrial sources, but most of this was refractory and only slowly remineralised. Significant, but seasonally variable, amounts of organic matter were derived from microphytobenthos (MPB), but this was rapidly remineralised and comprised only a minor fraction of the preserved sediment organic matter pool. Compound specific stable-isotope analysis of bacterial biomarkers suggested that the bacteria within the sediment were consuming microalgae-derived material. Separation of MPB from the sediment at the site in the upper estuary using the lens-tissue technique was found to significantly fractionate the algae community with cyanobacteria being enriched in the separated fraction. Nitrogen fixation probably contributed significantly to the growth requirements of cyanobacteria at the site in the upper estuary, as indicated by the low δ 15 N value of the cyanobacteria separated from the sediment.KEY WORDS: Microphytobenthos · Stable isotope · Compound-specific isotope-ratio mass spectrometry · Fatty acids · Sterols · Accessory pigment · Mudflat Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 280: [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] 2004 1999, Cahoon & Safi 2002), but this may shift seasonally to chlorophytes and cyanobacteria (Barranguet et al. 1997). In some areas, intertidal sediments may be dominated by cyanobacteria where high rates of nitrogen fixation may supply a significant amount of nitrogen to the benthic community (Stal et al. 1984, Bautista & Paerl 1985, Stal 1995.A number of approaches have been used to estimate the contributions of organic matter from various sources to sediments. Isotope ratios of 13 C/ 12 C have been used to estimate the relative contribution of terrestrial and marine sources to sedimentary organic matter (Fry & Sherr 1984). While this approach is relatively simple and gives an integrated estimate of sources for the total carbon in the sample, it will only provide useful information when there are 2 welldefined end-members. Furthermore, this technique gives little information about the type of marine or terrestrial organic matter in question.The use of lipid and pigment biomarkers such as fatty acids and sterols can allow the sources of various subfractions of organic matter to be identified much more specifically than any of the above approaches. However, unambiguously assigning sources to biomarkers is difficult, as they are rarely produced by a single class of organism. The advent of compound-specific stableisotope analysis has provided a powerful new tool for the differentiation between 2 sources of the same biomarker, provided the isotopic sign...

[1] The variability in the inherent optical properties along an estuary-coast-ocean continuum in tropical Australia has been studied. The study area, the Fitzroy Estuary and Keppel Bay system, is a shallow coastal environment (depth < 30 m) with highly turbid waters in the estuary and blue oceanic waters in the bay and subject to macrotides. Biogeochemical and inherent optical properties (IOPs) were sampled in the near-surface layer spatially and across the tidal phase during the dry season. These determinations included continuous measurements of spectral absorption, scattering and backscattering coefficients, together with discrete measurements of spectral absorption coefficients of phytoplankton, nonalgal particles and colored dissolved organic matter, and concentrations of phytoplankton pigments and suspended matter. Because of a large variability in the characteristics of the water components on short spatial and temporal scales, we observe a large variability in the associated optical properties. From the estuary to the bay, particle scattering and dissolved absorption decreased by 2 orders of magnitude, and nonalgal particle absorption decreased by 3 orders of magnitude. We also observed a strong variability in particle single scattering albedo and backscattering efficiency (by a factor of 6) and in specific IOPs (IOPs normalized by the relevant constituent concentration) such as suspended matter-specific particle scattering and chlorophyll-specific phytoplankton absorption. Superimposed on this strong spatial variability is the effect of the semidiurnal tide, which affects the spatial distribution of all measured properties. These results emphasize the need for spatially and temporally adjusted algorithms for remote sensing in complex coastal systems.

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A method using flow-injection, gas-diffusion, derivatisation and then fluorescent detection has been established for ammonium ion determination in seawater. The fluorescent derivative formed by reacting ortho-phthaldialdehyde (OPA) and sulfite with ammonia gives high sensitivity while removing potential interferences. This is required to measure the low concentrations of ammonium often seen in the open ocean. The experimental conditions (flow-rate, reagent concentrations, membrane configurations, etc.) were manipulated to improve performance. For a sample throughput of 30 samples h(-1), the limit of detection was 7 nM, the coefficient of variation was 5.7% at 800 nM, and the calibration curve was linear to at least 4 micromol L(-1). Interferences were minimised by a gaseous diffusion step. Volatile small molecular-weight amines as interferents were discriminated against by this method. They neither passed through the membrane as efficiently as ammonia, nor reacted as readily with OPA when sulfite was the reductant. Contamination by ammonia from laboratory and shipboard sources complicates application of the method to natural waters, especially measurement of low concentrations (<100 nM) in open-ocean waters. Steps to overcome contamination are described in detail. Some results are presented for ammonium determination in Southern Ocean and Huon Estuary (Tasmania) waters.

A global compilation of in situ data is useful to evaluate the quality of ocean-colour satellite data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (including, inter alia, MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID, AMT, ICES, HOT and GeP&CO) and span the period from 1997 to 2018. Observations of the following variables were compiled: spectral remotesensing reflectances, concentrations of chlorophyll a, spectral inherent optical properties, spectral diffuse attenuation coefficients and total suspended matter. The data were from multi-project archives acquired via open internet services or from individual projects, acquired directly from data providers. Methodologies were implemented for homogenization, quality control and merging of all data. No changes were made to the original data, other than averaging of observations that were close in time and space, elimination of some points after quality control and conversion to a standard format. The final result is a merged table designed for validation of satellite-derived ocean-colour products and available in text format. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) was propagated throughout the work and made available in the final table. By making the metadata available, provenance is better documented, and it is also possible to analyse each set of data separately. This paper also describes the changes that were made to the compilation in relation to the previous version (Valente et al., 2016).