Description: In marine fish, stock complexity confers resilience to environmental variability and exploitation. Accurate stock identification is, therefore, a prerequisite to decipher the factors responsible for recruitment variation. We concatenated energetic reproductive investment with otolith microchemistry in order to delineate between stock spawning components in bonga shad Ethmalosa fimbriata in Senegal. Satellite-derived (Moderate-resolution Imaging Spectroradiometer – MODIS Aqua, level 2, 0.1 degrees) sea surface temperatures were assessed at Joal (15 km radius) and Djifer once per sampling week. As no remote sensing data for inland waters are available, the Saloum River's surface water temperatures were recorded in situ once per sampling week with a digital thermometer (ama-digit ad 15 th; precision 0.4%; accuracy 0.4%). At Djifer and Foundiougne, salinity was determined once per sampling week according to the Practical Salinity Scale (PSS-78) with a handheld refractometer (Aqua Medic; precision 0.7%, accuracy 0.2%) using in situ water samples. For Joal, monthly means in MODIS satellite-derived (Aquarius, level 3, 0.5 degrees) sea surface salinities were used. Monthly sampling was conducted at the Senegalese southern coast (SSC) and inside the Saloum River from February to October 2014, during Ethmalosa fimbriata's extended spawning season. Three environmentally contrasted study sites were chosen: Joal (SSC, 14°9.1' N; 16°51.7' W), Djifer (Saloum River's mouth, 13°57.8' N; 16°44.8' W), and Foundiougne (Saloum River's middle reaches, 14°8.1' N; 16°28.1' W). Fish were caught with gill nets (32 - 36 mm mesh size) by local fishermen and immediately stored on crushed ice after landing. Approx. 1000 fish per sampling site and month were examined randomly in order to find stage V females, i.e. mature individuals with ovaries containing fully hydrated oocytes. Sagittal otoliths were extracted, rinsed with ethanol (70%), and stored dry in Eppendorf caps. Females that spawned recently or lost part of their egg batch during handling were rejected. Total wet mass (WM±0.01 g) and total length (LT, nearest mm) were obtained from individual stage V females. Ovaries were dissected, and oocytes were extracted out of one ovary lobe, rinsed with deionized water, and counted under a stereomicroscope. Around 80 hydrated oocytes per fish (ca. 70 for lipid analysis, ca. 10 for protein analysis) were transferred to a pre-weighed tin cap, stored in cryovials, and deep-frozen in liquid nitrogen. Dissected ovaries were transferred to a 4% borax buffered formaldehyde and freshwater liquid for fecundity analysis. Absolute batch fecundity (ABF) was estimated gravimetrically using the hydrated oocyte method for indeterminate spawners. The female's relative batch fecundity (RBF) was calculated by dividing ABF with the ovary free body weight (OFBM). The gonado-somatic index (GSI) of female spawners was calculated by dividing the ovary weight (OM, ±0.0001 g) by the ovary-free body weight (OFBM, ±0.1 g): GSI=OM ×[OFBM]^(-1) × 100. In order to access the nutritional status of female fish, a condition index (CI) was calculated for each individual using WM, LT, and b of the length-weight relationship: CI = WM x LT ^ -3.62 x 1000. Oocytes in tin caps were freeze-dried (24 h) and weighed again to ascertain their dry mass (ODM±0.1 µg). The following equation was employed to calculate oocyte volumes (OV, mm3): OV =4/3 π(d_2/2)^2. Oocyte lipid content was determined by gas chromatography flame ionization detection (GC-FID). Three random samples were processed via GC mass spectrometry to ensure that all lipid classes were detected by the GC-FID. The total lipid content was assessed via summation of all individual lipid classes. For protein analyses, counted oocytes in tin caps were dried at 40°C for 〉24 h and weighted again for dry weight determination. Total organic carbon (C) and nitrogen (N) content was measured using a EuroVector EuroEA3000 Elemental Analyzer. From the total amount of N in the sample, the protein content was calculated according to Kjeldahl (Bradstreet, 1954), using a nitrogen-protein conversion factor of 6.25. The oocyte gross energy content (J) was calculated on the basis of measured protein and lipid content, which were multiplied by corresponding energy values from literature: The amount of proteins per given oocyte (P, mg) was multiplied by a factor of 23.66 J mg-1 and subsequently added to the total amount of lipids per oocyte (L, mg) multiplied by 39.57 J mg-1 (Henken et al. 1986). Dividing the oocyte's energy content by the oocyte's dry weight allowed for calculation of the oocyte's calorific value (J mg-1). Further, the oocyte energy content of each individual E. fimbriata female was multiplied by its respective relative batch fecundity (RBF) to obtain a standardized estimate of the total amount of energy invested into a single spawning batch per unit body mass (SBEC, J g-1 OFBM): SBEC = [(P × 23.66 J [mg]^(-1) )+(L × 39.57 J [mg]^(-1) )]× RBF. Dried sagittal otoliths were embedded in epoxy resin (Araldite 2020; Huntsman, USA) on glass slides. They were ground from the proximal side down to the nucleus using an MPS2 surface-grinding machine (GN, Nürnberg, Germany) and polished with a diamond-grinding wheel (grain size 15 µm). Concentrations of eight elements (Magnesium, Manganese, Copper, Zinc (Zn), Strontium (Sr), Yttrium, Barium (Ba), and Lead) were determined along transects of up to 2300 μm length along the rostrum's anterior edge on the otolith's proximal side. Analyses were carried out by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) using a NewWave UP193 solid-state laser coupled to a Thermo-Finnigan Element2 ICP-MS. The employed analytical procedure used a pulse rate of 10 Hz, an irradiance of ca. 1 GW cm−2, a spot size of 75 μm, and a traverse speed of 3 μm s−1. For external calibration the glass reference material NIST610 was analysed after every second ablation path, using reference values of Jochum et al. (2011). Data quality was validated by analysing a pressed pellet of NIES22 otolith with a calcium concentration of 38.8 wt. %, as well as through regular analyses of BCR-2G and BHVO-2G standard glasses. Precision was 〈 2% and the accuracy was 〈 13% for Zn. Recovery percentages were 100%, 101%, and 114% for Ba, Sr, and Zn, respectively. To account for the substitution of Calcium (Ca) by the divalent elements Ba, Sr, and Zn all element concentrations are given as element:Ca ratios. Mean otolith Ba:Ca, Sr:Ca, and Zn:Ca values throughout the entire female's lifetime are given in this dataset.

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wang, Z. A., Moustahfid, H., Mueller, A., V., Michel, A. P. M., Mowlem, M., Glazer, B. T., Mooney, T. A., Michaels, W., McQuillan, J. S., Robidart, J. C., Churchill, J., Sourisseau, M., Daniel, A., Schaap, A., Monk, S., Friedman, K., & Brehmer, P. Advancing observation of ocean biogeochemistry, biology, and ecosystems with cost-effective in situ sensing technologies. Frontiers in Marine Science, 6, (2019): 519, doi:10.3389/fmars.2019.00519.

Description: Advancing our understanding of ocean biogeochemistry, biology, and ecosystems relies on the ability to make observations both in the ocean and at the critical boundaries between the ocean and other earth systems at relevant spatial and temporal scales. After decades of advancement in ocean observing technologies, one of the key remaining challenges is how to cost-effectively make measurements at the increased resolution necessary for illuminating complex system processes and rapidly evolving changes. In recent years, biogeochemical in situ sensors have been emerging that are threefold or more lower in cost than established technologies; the cost reduction for many biological in situ sensors has also been significant, although the absolute costs are still relatively high. Cost savings in these advancements has been driven by miniaturization, new methods of packaging, and lower-cost mass-produced components such as electronics and materials. Recently, field projects have demonstrated the potential for science-quality data collection via large-scale deployments using cost-effective sensors and deployment strategies. In the coming decade, it is envisioned that ocean biogeochemistry and biology observations will be revolutionized by continued innovation in sensors with increasingly low price points and the scale-up of deployments of these in situ sensor technologies. The goal of this study is therefore to: (1) provide a review of existing sensor technologies that are already achieving cost-effectiveness compared with traditional instrumentation, (2) present case studies of cost-effective in situ deployments that can provide insight into methods for bridging observational gaps, (3) identify key challenge areas where progress in cost reduction is lagging, and (4) present a number of potentially transformative directions for future ocean biogeochemical and biological studies using cost-effective technologies and deployment strategies.

Description: The unpublished work related to iTag and mini-DO sensor was supported by the US National Science Foundation (NSF) (DBI-145559). The US NSF (OCE-1233654), the US National Institute of Standards and Technology (NIST) (60NANB10D024), and the NOAA Sea Grant (2017-R/RCM-51) supported the development of the CHANOS sensor. Part of this work was supported by the European Commission via the STEMM-CCS, AtlantOS, SenseOCEAN, TriAtlas, and Preface projects under the European Union’s Horizon 2020 research and innovation program (Grant Nos. 603521, 654462, 633211, 614141, and 817578), as well as the AWA project (IRD and BMBF; 01DG12073E), and the Blue Belt Initiative (BBI). The work on the LOC nutrients and carbonate sensors was supported by the Autonuts and CarCASS projects, part of the UK Natural Environment Research Council capital program OCEANIDS (NE/P020798/1 and NE/P02081X/1). The work on zooplankton and chlorophyll sensors was co-supported by the ROEC program (Reseau d’Observation en Environnement Côtier 2015–2020) and the European Regional Development Fund (ERDF).

Description: Glider measurements acquired along four transects between Cap-Vert Peninsula and the Cape Verde archipelago in the eastern tropical North Atlantic during March–April 2014 were used to investigate fine-scale stirring in an anticyclonic eddy. The anticyclone was formed near 12°N off the continental shelf and propagated northwest toward the Cape Verde islands. At depth, between 100 and –400 m, the isolated anticyclone core contained relatively oxygenated, low-salinity South Atlantic Central Water, while the surrounding water masses were saltier and poorly oxygenated. The dynamical and thermohaline subsurface environment favored the generation of fine-scale horizontal and vertical temperature and salinity structures in and around the core of the anticyclone. These features exhibited horizontal scales of O(10–30 km) relatively small with respect to the eddy radius of O(150 km). The vertical scales of O(5–100 m) were associated to density-compensated gradient. Spectra of salinity and oxygen along isopycnals revealed a slope of around k−2 in the 10- to 100-km horizontal scale range. Further analyses suggest that the fine-scale structures are likely related to tracer stirring processes. Such mesoscale anticyclonic eddies and the embedded fine-scale tracers in and around them could play a major role in the transport of South Atlantic Central Water masses and ventilation of the North Atlantic Oxygen Minimum Zone.