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Optical sensing of plankton communities and dynamics
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A darkfield optical flow imaging system for high-throughput analysis of marine zooplankton
P-B2-06
Tao Chen* , Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences
Jianping Li, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences
Presenter Email: tao.chen@siat.ac.cn |
| Zooplankton plays important role in matter and energy cycling in marine ecological system. High spatio-temporal frequency observation of zooplankton to quantify their abundance, taxonomy and size composition is one of the fundamental tasks for oceanographic research. However, compared to phytoplankton, fishes, sea birds, and sea mammals, zooplankton observation still represents a major bottleneck in the design of truly ecosystemic studies of marine systems.
Optical imaging is promising for quantitative zooplankton sensing due to its non-contact, rapid characteristics and good resolution for morphological analysis. However, the sample volume and imaging resolution do not always enable quantitative estimates of key zooplankton variables. In-situ static imaging instruments (e.g. CPICS and SPC) are good in imaging quality and hence resulted in good taxonomic resolution for zooplankton observation at fixed site underwater. However, their imaging volume is too small for efficient sensing of sparsely distributed zooplankton in natural seawater environment. On the contrary, towed imaging technologies (e.g. VPR and ISIIS) have much larger imaging volume and water sampling throughput, but the increase in silhouette imaging efficiency is payed off by sacrificing morphological details, and hence resulting in taxonomy weakness.
Net sampling enrichment followed by imaging (e.g. ZooScan) is another strategy proved highly efficient in zooplankton analysis. Particularly, besides terrestrial lab examination of chemically fixed samples shipped back by cruise, there is an increasing need to have concentrated live samples being analyzed on board. Unfortunately, flat-scanning technology has poor imaging resolution and slow speed, and requires unilaminar distribution of samples in static. These limitations have disabled its application for live swimming zooplankton imaging and severely degraded their performance on a jerky research vessel.
In this light, we aimed to develop a new flow imaging system that is capable of high-throughput imaging net-condensed live or fixed zooplankton particles with good imaging quality and enhanced efficiency. The system features in equipment of 360-degee darkfield illumination with matched illumination volume to depth-of-field, and in-line arrangement between imaging axis and flowing direction. With up to 27.2mmx21.7mm field-of-view and 20 micron resolution, the system can acquire high quality images of zooplankton in size range from 400 micron to 10mm at a volume flow rate of 1.5L/min. With dedicated image analysis software, the system is expected to produce zooplankton abundance, taxonomy and sizing information with greatly increased accuracy and efficiency.
We will report the hardware and software development of this imaging system and present preliminary results in this conference. |
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