Methods in Oceanography最新文献

Since the 1930s, the use of the Continuous Plankton Recorder (CPR) sampler has been considered one of the most important plankton collection methods using ships of opportunity, which make samples available on a wider spatial and temporal scale. With this advantage in mind, the objective of this work was to develop a device that uses a similar collection method as the CPR, but with lower construction costs, and to carry out changes in functioning that facilitate its use in fishing craft in the Southeast and South regions of Brazil, for use as a tool for generating oceanographic data applied to fisheries management. The new equipment, called the Oceanographic Towed Vehicle (Veículo Oceanográfico de Reboque —VOR), has mechanical improvements and construction alterations for combined use with a multiparameter probe. For the new design of the vehicle, the aim was to create the hydrodynamic shape of an Undulating Towed Vehicle (U-tow), but without the characteristic of undulating in the water column. Based on a prototype, three experimental trawls were carried out, to calibrate the mechanism and analyze the material collected, in a laboratory, through a stereoscopic microscope.

The National Reference Station (NRS) network, part of Australia’s Integrated Marine Observing System (IMOS), is designed to provide the baseline multi-decadal time series required to understand how large-scale, long-term change and variability in the global ocean are affecting Australia’s coastal ocean ecosystems. High temporal resolution observations of oceanographic variables are taken continuously across the network’s nine moored stations using a Water Quality Monitor (WQM) multi-sensor. The data collected are made freely available and thus need to be assessed to ensure their consistency and fitness-for-use prior to release. Here, we describe a hybrid quality control system comprising a series of tests to provide QC flags for these data and an experimental ‘fuzzy logic’ approach to assessing data. This approach extends the qualitative pass/fail approach of the QC flags to a quantitative system that provides estimates of uncertainty around each data point. We compared the results obtained from running these two assessment schemes on a common dataset to those produced by an independent manual QC undertaken by an expert oceanographer. The qualitative flag and quantitative fuzzy logic QC assessments were shown to be highly correlated and capable of flagging samples that were clearly erroneous. In general, however, the quality assessments of the two QC schemes did not accurately match those of the oceanographer, with the semi-automated QC schemes being far more conservative in flagging samples as ‘bad’. The conservative nature of the semi-automated systems does, however, provide a solution for QC with a known risk. Our software systems should thus be seen as robust low-pass filters of the data with subsequent expert review of data flagged as ‘bad’ to be recommended.

Performance of autonomous pH sensors is evaluated by comparing in situ data to independent bench-top measurements of pH and to co-located pH, O₂, and $p{\mathrm{CO}}_2$ sensors. While the best practice is always to deploy a properly calibrated sensor, the lengthy time period required for sensor conditioning and calibration often results in sensor deployment without comprehensive calibration. Quality control (QC) procedures are examined to determine the errors associated with different in situ calibration approaches and lay a framework for best practices. Sensor packages employing the Honeywell Durafet remained stable across multiple deployments for over nine months. However, sensor performance was often limited by biofouling. Regional empirical relationships for estimating carbonate system parameters are shown to enable identification of otherwise indistinguishable sensor offset and drift when multiple sensor types are co-located. Uncertainty is determined by calibration approach and must be quantified on a case-by-case basis. Our results indicate that the Durafet is capable of accuracy, relative to a chosen reference, of better than 0.03 pH units over multiple months. Accuracy is improved when a robust shore-side calibration is performed, an independent means of QC is available throughout a deployment, and effective biofouling prevention measures are taken.

Absorption spectra of seawater can be used to estimate the concentration of nitrate based on the UV absorption characteristic of nitrate. However the results of that estimation show an increased uncertainty compared to wet chemical methods. This is caused by the close proximity and the magnitude of the bromide peak (as the main component of seawater salt) close to the nitrate signal in the UV. Current data processing methods are optimized to give good results under constant conditions in terms of temperature, salinity, and CDOM concentration. However, in coastal regions all three parameters are highly variable.

In this work three methods to determine nitrate concentration from the seawater UV spectrum are compared: (A) via the subtraction of the seawater spectrum and CDOM absorbance from the total absorbance of the sample and then fitting the nitrate absorption to the remaining absorbance, (B) the subtraction of the seawater spectrum and fitting the spectral signature of nitrate and CDOM as suggested by Sakamoto et al. (2009) and (C) the direct determination via the fitting of the spectral signature of all components to the sample spectrum. The results of all three methods correlate ($R>0.99$) very well with each other as well as to the results of the wet chemical analysis.

An extensive dataset of a transect from the Southern North Sea into the Weser estuary (RV HEINCKE transect 345), which covers a broad salinity range as well as a broad range of nitrate concentrations, is used to exemplary show the potential and the limitations of all three methods under these conditions.

The hadal trenches and the biology and ecology of the organisms that inhabit them remain one of the least understood marine environments. The study of hadal trenches which is often referred to as hadal science, needs special technical equipment support such as landers, unmanned submersibles and manned submersibles. Sending sampling devices or exploratory vehicles to hadal depths is technically challenging and expensive, consequently, our current understanding of hadal ecological structure is still very much in its infancy. In recognition of the significance that hadal science holds and the unique and challenging requirements that work in the deep ocean presents, Shanghai Ocean University has made a significant commitment to develop operational support for the promotion of hadal science in China. The present authors from the JIAOLONG development team were invited by Shanghai Ocean University to establish a hadal science and technology research center (HAST). The first focus of HAST is to construct a movable laboratory for hadal trenches which includes a mothership, an Human Occupied Vehicle, an Autonomous and Remotely-operated Vehicle and several landers. The purpose of this paper is to introduce the basic philosophy and concepts for the movable laboratory and the preliminary designs for the manned submersible, unmanned submersible and landers. Through these designs all the technical problems to be solved in the development of the full ocean depth surveying and sampling tools are identified and possible solutions to the key technical issues are discussed.

We developed a new multi-water-sampling system, ANEMONE-11, for autonomous underwater vehicle and remotely operated underwater vehicle exploration. Water samples are continuously collected by the ANEMONE-11 sampler by an in situ water pump at 40 mL/min and are sent to a selection valve unit that consists of 128 valves connected to 40 mL sampling bottles (50 cm in length). Each valve in the unit is selected and opened at preprogrammed intervals. We also discuss the results of observations at a hydrothermal area in the Okinawa Trough.

Penetration of the photosynthetically available radiation (PAR, over 400–700 nm) in the upper ocean is important for many processes such as water radiant heating and primary productivity. Because of this importance, daily PAR at sea surface ($\overline{\mathrm{PAR}}\left(0^{+}\right)$) is routinely generated from ocean-color images for global studies. To propagate this broadband solar radiation through the upper ocean, an attenuation coefficient of PAR ($K_{\mathrm{PAR}}$) is also generated from the same ocean-color measurements. However, due to the empirical nature of the $K_{\mathrm{PAR}}$ algorithm, this $K_{\mathrm{PAR}}$ product corresponds to an instantaneous PAR at a fixed sun angle, with no diurnal variability. It is hence necessary to have an attenuation coefficient matching the temporal characteristics of daily PAR. This paper represents an effort to meet this need. Using ECOLIGHT, the subsurface light field for a wide range of water bodies was simulated, from which the attenuation coefficient ($K_{\overline{\mathrm{PAR}}}$) of daily PAR was calculated. We presented the diurnal and vertical variation of this attenuation coefficient, and found that it can be well predicted (within $\sim$7%) as a function of the total absorption coefficient and backscattering coefficient at 490 nm and the noontime solar zenith angle. This new model offers an efficient and reasonably accurate approach for quantifying daily upper water column PAR within the global ocean from satellite measurements of water color.

In the open ocean, the movements and habitat use of large mobile predators are driven by dynamic interactions between biological and physical variables and complex predator–prey relationships. Understanding the spatial and temporal distributions of pelagic fishes and sharks is a critical component of conservation and fisheries management. Here, we report on a novel non-extractive method for the study of pelagic wildlife, based on baited stereo-camera rigs. The mid-water rigs were derived from existing methodology commonly used in demersal fish surveys. We present new data from 66 moored deployments in Shark Bay, Western Australia (26°10′S, 113°06E) in seabed depths of up to 60 m as a demonstration of the rigs’ ability to resolve spatial variability in pelagic fish and shark assemblages, and to make accurate stereo-measurements of animal lengths. We observed 248 pelagic fishes and sharks from 27 species and 10 families and were able to distinguish between assemblages based nominally on location. We make some general recommendations on optimal deployment protocols and sampling effort regimes, based upon species accumulation rates and times of $\mathrm{Max}N$ (maximum number of individuals of a given species in a single video frame). Regression analyses between high quality and low quality stereo-measurements of fish fork-lengths and range were highly significant, indicating that body lengths and distance estimates were consistent even when stereo-measurements were deemed of low quality. Mid-water stereo-video camera rigs represent an efficient tool for the rapid and non-extractive monitoring of pelagic fish and shark populations, with particular relevance for application in no-take marine protected areas.