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Understanding rare suspended particulate matter (including planktonic microorganisms) in the deep ocean is important but difficult to sample, for which we deigned a large-sized in-situ water sampler (200-1000L), i.e., a large volume water transfer system sampler. The system comprises of a deep-ocean pump, a filtering device, data acquisition and control devices, a supporting frame, a power supply component, a connecting mechanism, and a flow meter, etc. The filtering device integrates membranes for three-graded filtration at 0.22, 1, and 5μm, and an additional membrane aperture upon the need. The control device adopts two working modes: depth trigger and time trigger. The system can be added with a CTD and a fluorescence meter, etc. In addition, for a stationed site survey, several sets (such as 3 sets) of the system can be fixed at an interval on the suspension cable to work at different depths simultaneously. The system can be applied for high-level multi-layer filtration to obtain suspended particles. The system has been applied in several marine expeditions. The development of this system provides an ideal tool for deep-ocean in-situ sampling technology in China. The applications of the large volume water transfer system sampler for in-situ sampling in deep-ocean have been launched for a few times. Some interesting phenomena have been discovered and the advantages of in situ sampling are proved.

A sea surface drifting buoy system based on Beidou communication system is designed and developed by Institute of Oceanology, Chinese Academy of Sciences. It employs a low power consumption chip, STM32F103RCT6, as the core of the control system, which can collect and process the data of the ocean environment automatically and monitor the status of the buoy system. Then the marine data are transferred to the lab on shore in real time by Beidou satellite. With the power management function, this system will reduce system power consumption greatly and extend the working time of the buoy. By placing and using the buoy at sea, the feasibility and reliability of this system is verified, which has provided the reliability support of acquiring some real-time elements and track currents of the ocean current in some certain sea area in long time real-time access to the sea currents.

Laser induced fluorescence (LIF) is a common technique for measuring chlorophyll-a (Chl-a) concentration in water, and is able to obtain profile distribution. The natural water body is a turbid media for laser transmission, resulting in a great attenuation of luminance in a short distance. Increasing laser intensity is often considered an effective way to probe deeper. However, it has been found that there is a non-linear relationship between fluorescence intensity of Chl-a solution and laser energy which may causes laser-induced saturation of fluorescence with measurement conditions unchanged. Thus, the saturation effects of Chl-a fluorescence at 685 nm were studied at two aspects, namely, Chl-a concentration and the intensity of excitation pulse. In the experiment, several concentrations of Chl-a solution were measured by 355 nm laser. For a fixed Chl-a concentration, the intensity of fluorescence gradually becomes to worse following the intensity of excitation pulse raised, while the ratios of Raman intensity of water to pulse intensity correspond to a good linear relationship. On the other hand, with different energy densities of excitation laser, the variations of Chl-a fluorescence intensity were analyzed by non-linear curve fitting. For higher Chl-a concentration, the lower threshold value of excitation intensity can lead to the nonlinearity of induced fluorescence intensity versus laser intensity. Here, the nonlinear changes of Chl-a fluorescence with saturated excitation are studied for supporting the measurement of oceanographic fluorescence by LIF and correctly estimating chlorophyll concentrations.