Nutrient, pigment, suspended matter and turbidity measurements in the Belgian part of the North Sea.

Through regular sampling surveys, the Flanders Marine Institute is generating long term data series for the Belgian coastal water and sand bank systems, a designated site in the Long Term Ecological Research (LTER) network. The data series is built on sampling activities initiated in 2002, but gradually upgraded and extended in the framework of the LifeWatch marine observatory and the Integrated Carbon Observation System (ICOS) participation. Nine nearshore stations are sampled monthly, with additional seasonal sampling of eight offshore stations. This paper presents the generated data series for nutrients, pigments, suspended matter and turbidity. The collection, methodology and processing of the 2002-2018 dataset is described, along with its data curation, integration and quality control. Yearly versions of the data are published online in a standardized format, accompanied with extensive metadata description and labelled with digital identifiers for traceability. Data is published under a CC-BY license, allowing use of the data under the condition of providing reference to the original source.

Effect of carbonate chemistry alteration on the early embryonic development of the Pacific oyster (Crassostrea gigas).

Ocean acidification, due to anthropogenic CO2 absorption by the ocean, may have profound impacts on marine biota. Calcareous organisms are expected to be particularly sensitive due to the decreasing availability of carbonate ions driven by decreasing pH levels. Recently, some studies focused on the early life stages of mollusks that are supposedly more sensitive to environmental disturbances than adult stages. Although these studies have shown decreased growth rates and increased proportions of abnormal development under low pH conditions, they did not allow attribution to pH induced changes in physiology or changes due to a decrease in aragonite saturation state. This study aims to assess the impact of several carbonate-system perturbations on the growth of Pacific oyster (Crassostrea gigas) larvae during the first 3 days of development (until shelled D-veliger larvae). Seawater with five different chemistries was obtained by separately manipulating pH, total alkalinity and aragonite saturation state (calcium addition). Results showed that the developmental success and growth rates were not directly affected by changes in pH or aragonite saturation state but were highly correlated with the availability of carbonate ions. In contrast to previous studies, both developmental success into viable D-shaped larvae and growth rates were not significantly altered as long as carbonate ion concentrations were above aragonite saturation levels, but they strongly decreased below saturation levels. These results suggest that the mechanisms used by these organisms to regulate calcification rates are not efficient enough to compensate for the low availability of carbonate ions under corrosive conditions.

Nitrification in the Schelde estuary: methodological aspects and factors influencing its activity.

Abstract We present a 15-month dataset on nitrification measurements in the Schelde estuary (Belgium and The Netherlands). Nitrification was estimated using the N-serve sensitive dark (14)C-bicarbonate incorporation technique. A peak of nitrification activity was observed in the freshwater part of the estuary. Downstream from this peak, nitrification declined, probably because of ammonium limitation. A range of nitrification inhibitors was tested on both a Nitrosomonas europaea culture and estuarine samples. It was found that methyl fluoride and acetylene stimulated dark (14)C-bicarbonate incorporation and those inhibitors were therefore considered inappropriate nitrification inhibitors in combination with this technique. The effect of the inhibitor N-serve was studied on the dark incorporation of (13)C-bicarbonate into polar lipid derived fatty acids to further identify the dominant chemoautotrophic processes. Inhibition of polar lipid derived fatty acid labelling in the presence of N-serve was complete, suggesting that nitrifying bacteria dominated the chemoautotrophic community.