In this paper we review the technologies available to make globally quantitative observations of particles in general-and plankton in particular-in the world oceans, and for sizes varying from sub-microns to centimeters. Some of these technologies have been available for years while others have only recently emerged. Use of these technologies is critical to improve understanding of the processes that control abundances, distributions and composition of plankton, provide data necessary to constrain and improve ecosystem and biogeochemical models, and forecast changes in marine ecosystems in light of climate change. In this paper we begin by providing the motivation for plankton observations, quantification and diversity qualification on a global scale. We then expand on the state-of-the-art, detailing a variety of relevant and (mostly) mature technologies and measurements, including bulk measurements of plankton, pigment composition, uses of genomic, optical and acoustical methods as well
A new Video Plankton Recorder (VPRII) has been developed for rapid surveys of plankton and seston in the size range of 100µm-1cm. The VPRII system includes: 1) a high-resolution digital camera (1Mpixel, 10-bits, 30Hz frame-rate), 2) a fast towfish capable of tow speeds up to 12 knots and 3-axis motion for automatic undulation and ship-wake avoidance, small diameter tow cable and winch for deployment on coastal vessels, and 3) new interface software (Visual Plankton) for automatic identification of plankton to major taxa and visualization of these taxa together with hydrographic data in real time. Camera and strobe optics are laboratory-adjusted to select the field-of-view (5-20mm), and depth-of-field is objectively calibrated using a tethered organism (e.g., copepod) and automatic focus-detection software. The VPRII towfish comprises a fuselage, a fixed main wing, and three servo-controlled tail fins: port and starboard for dive, climb, and roll control and rudder for lateral movement. Placement of the strobe (starboard wing-tip), camera (fuselage nose), and cantilevered tow-bridle minimize disturbance of the imaged volume. Compared with typical net surveys in shelf areas, the VPRII counts more plankton per station, quantifies ubiquitous fragile forms, automatically identifies plankton to major taxa and measures their size, quantifies scales of patchiness down to a few cm, and displays high-resolution distributions of plankton taxa and hydrography while underway. The VPRII is available to researchers via the Woods Hole Oceanographic Institution ship instrumentation pool. AcknowledgmentsWe thank the officers and crew of the R/V Oceanus for their support during field tests of the new VPR system. Engineers Pierre Tillier, Ken Peal, Nick Witzel, Ed Hobart, and Steve Faluotico made valuable contributions to the design and construction of the new VPR. Others involved in this project include
The roles of plankton behavior, stratification, and microstructure in the formation of fine-scale plankton layers were examined using a 3-dimensional video plankton recorder mounted on a remotely operated vehicle. Vertically compressed plankton patches were observed in association with a cold pool over the Southern Flank of Georges Bank, extending from the tidal mixing front to the shelf-slope break during the months of May and June, 1994, 1995, 1997. In June 1995, 3 major plankton layers were present: a 10 m thick layer above the thermocline, a 1 m thick layer within the thermocline, and a third, 2 to 5 m thick layer immediately below the thermocline. Energy dissipation rate was lowest in the central layer and increased in both top and bottom layers. Some passive organisms and particles, e.g. the colonial diatom Chaetoceros socialis and rod-shaped diatoms, were concentrated in all 3 layers, while marine snow particles were found only in transitional regions. All stages of Calanus spp. were present in high numbers on the fringes of all 3 layers, while Oithona sp. was found only in the thin, central layer. Plankton were significantly aggregated only when the motility number, Mn (i.e. ratio of plankton swimming speed/rms turbulent velocity) was greater than 3, suggesting dominance of plankton behavior over physical structure. Under both quiescent and turbulent conditions, the Lagrangian frequency spectra (f ) for swimming plankton and passive particles decreased with a slope of f -2 . However, in quiescent conditions, the magnitude of the spectrum for swimming plankton was 10-fold greater than for passive particles, illustrating a decoupling of plankton swimming from turbulent eddies. The air/water interface, the pycnocline, and multiple shear interfaces at density discontinuities act as boundaries to vertical zones where plankton behavior may succumb to or dominate background microstructure, thus providing a mechanism for formation of plankton and particulate layers.KEY WORDS: Fine-scale vertical structure · Thin layers · Plankton behavior · Turbulence Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 267: [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] 2004 communities, species-specific patterns in abundance can form as a function of fine-scale physical structure (Owen 1989, Davis et al. 1992, Gallager et al. 1996b and may persist for many days (Donaghay et al. 1992, Cowles & Desiderio 1993, reviewed in Cowles et al. 1998. If this scale is undersampled or, worse, ignored, the result of persistent fine-scale structure will be gross underestimates of production (Cowles et al. 1998).Vertical fine-structure has been observed since the study of Eckart (1948), and is usually described in terms of mixing, such as the interaction between density stratification and horizontal shear (Gargett et al. 1984). One of the net results of shear is to redistribute horizontal variance onto vertical variance, producing the typical multiple-layer effect,...
A fundamental problem in limnology and oceanography is the inability to measure the taxonomic composition of plankton quickly over a broad range of scales. Traditional sampling with bottles and nets provides critical data at the species-level, but has limited spatio-temporal coverage and can destroy ubiquitous delicate forms. To augment traditional sampling, recent advances in bioacoustics and non-imaging optics provide real-time high-resolution data on biomass abundance and size composition. New optical imaging approaches provide coarse taxonomic composition but require manual image identification, preventing real-time observation. Here, we describe a method of optical sampling and analysis, using the Video Plankton Recorder, to automatically identify plankton to major taxa (and to species in some cases) and observe their distributions at sea in real time. We present a detailed assessment of classifier accuracy, including a comparison of machine-and handclassification of images. The automated classification method was found to be sufficiently accurate for estimating abundance patterns of dominant taxa but not for less abundant taxa. The range in overall accuracy was 60 to 70% for 7 taxa and 79 to 82% for 2 taxa, with accuracies for individual taxa ranging between 45 and 91%. Classification error was small relative to natural variability in abundance of dominant taxa. For a given taxon, the error in the abundance estimate was low in regions of high relative abundance. A manual correction step can be used in areas of low relative abundance to obtain accurate abundance estimates. Example data from 2 cruises are presented to illustrate the utility of real-time taxa-specific data collection. These data represent the first real-time automatic identification and mapping of plankton taxa at sea. This methodology represents an intermediate step towards the ultimate goal of real-time identification of plankton to the level of species and life stage. At present, optical imaging methods cannot replace net and bottle surveys, but can be used to obtain coarse taxonomic composition of plankton (including fragile forms) with an identification accuracy that is high enough to produce quantitative high-resolution maps of abundant taxa in real time.
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