The upper ocean, including the biologically productive euphotic zone and the mixed layer, has great relevance for studies of physical, biogeochemical, and ecosystem processes and their interaction. ...Observing this layer with a continuous presence, sampling many of the relevant variables, and with sufficient vertical resolution, has remained a challenge. Here a system is presented that can be deployed on the top of deep-ocean moorings, with a drive mechanism at depths of 150-200 m, which mechanically winches a large sensor float and smaller communications float tethered above it to the surface and back down again, typically twice per day for periods up to 1 year. The sensor float can carry several sizeable sensors, and it has enough buoyancy to reach the near surface and for the communications float to pierce the surface even in the presence of strong currents. The system can survive mooring blowover to 1000-m depth. The battery-powered design is made possible by using a balanced energy-conserving principle. Reliability is enhanced with a drive assembly that employs a single rotating part that has no slip rings or rotating seals. The profiling bodies can break the surface to sample the near-surface layer and to establish satellite communication for data relay or reception of new commands. An inductive pass-through mode allows communication with other mooring components throughout the water column beneath the system. A number of successful demonstration deployments have been completed.
Adults of Oithona nana feed on copepod nauplii of 110‐µm body length. An Ivlev curve is used to describe feeding as a function of prey density. At natural prey densities, carnivorous feeding would ...provide only 25% of its metabolic requirements. Very low respiration rate and the nature of the diet are important considerations in assessing the ecological effect of this abundant species.
The ocean’s biological carbon pump plays a central role in regulating atmospheric CO2 levels. In particular, the depth at which sinking organic carbon is broken down and respired in the mesopelagic ...zone is critical, with deeper remineralisation resulting in greater carbon storage. Until recently, however, a balanced budget of the supply and consumption of organic carbon in the mesopelagic had not been constructed in any region of the ocean, and the processes controlling organic carbon turnover are still poorly understood. Large-scale data syntheses suggest that a wide range of factors can influence remineralisation depth including upper-ocean ecological interactions, and interior dissolved oxygen concentration and temperature. However these analyses do not provide a mechanistic understanding of remineralisation, which increases the challenge of appropriately modelling the mesopelagic carbon dynamics. In light of this, the UK Natural Environment Research Council has funded a programme with this mechanistic understanding as its aim, drawing targeted fieldwork right through to implementation of a new parameterisation for mesopelagic remineralisation within an IPCC class global biogeochemical model. The Controls over Ocean Mesopelagic Interior Carbon Storage (COMICS) programme will deliver new insights into the processes of carbon cycling in the mesopelagic zone and how these influence ocean carbon storage. Here we outline the programme’s rationale, its goals, planned fieldwork and modelling activities, with the aim of stimulating international collaboration.
Adults of Oithona nana feed on copepod nauplii of 110-μ m body lenght. An Ivlev curve is used to describe feeding as a function of prey density. At natural prey densities, carnivorous feeding would ...provide only 25% of its metabolic requirements. Very low respiration rate and the nature of the diet are important considerations in assessing the ecological effect of this abundant species.
Marine planktonic organisms that undertake active vertical migrations over their life cycle are important contributors to downward particle flux in the oceans. Acantharia, globally distributed ...heterotrophic protists that are unique in building skeletons of celestite (strontium sulfate), can produce reproductive cysts covered by a heavy mineral shell that sink rapidly from surface to deep waters. We combined phylogenetic and biogeochemical analyses to explore the ecological and biogeochemical significance of this reproductive strategy. Phylogenetic analysis of the 18S and 28S rRNA genes of different cyst morphotypes collected in different oceans indicated that cyst-forming Acantharia belong to three early diverging and essentially non symbiotic clades from the orders Chaunacanthida and Holacanthida. Environmental high-throughput V9 tag sequences and clone libraries of the 18S rRNA showed that the three clades are widely distributed in the Indian, Atlantic and Pacific Oceans at different latitudes, but appear prominent in regions of higher primary productivity. Moreover, sequences of cyst-forming Acantharia were distributed evenly in both the photic and mesopelagic zone, a vertical distribution that we attribute to their life cycle where flagellated swarmers are released in deep waters from sinking cysts. Bathypelagic sediment traps in the subantarctic and oligotrophic subtropical Atlantic Ocean showed that downward flux of Acantharia was only large at high-latitudes and during a phytoplankton bloom. Their contribution to the total monthly particulate organic matter flux can represent up to 3%. High organic carbon export in cold waters would be a putative nutritional source for juveniles ascending in the water column. This study improves our understanding of the life cycle and biogeochemical contribution of Acantharia, and brings new insights into a remarkable reproductive strategy in marine protists.
Pelagic production at the Celtic Sea shelf break Joint, Ian; Wollast, Roland; Chou, Lei ...
Deep-sea research. Part II, Topical studies in oceanography,
2001, 2001-1-00, 20010101, Letnik:
48, Številka:
14
Journal Article
Recenzirano
This paper reviews the data obtained in the OMEX I Project on biological production in the surface waters of the Celtic Sea shelf break. The study focused on two regions— the Goban Spur and La ...Chapelle Bank. Satellite images of the Celtic Sea frequently show a region of cooler water at the shelf break, which results in the mixing of cooler, nutrient-rich waters to the sea surface. To examine the hypothesis that the Celtic Sea shelf break might be a region of enhanced production and sedimentation, observations were made at five regions. These were four sites along a transect of the Goban Spur, from the Celtic Sea shelf (water depth <200
m), through stations at water depths of 500–1000, 1500, and 3600
m; the fifth region was at La Chapelle Bank, which offered a contrasting site where the slope is steeper and influenced by canyons.
Estimates are made of seasonal production of phytoplankton, bacterioplankton, microzooplankton, and mesozooplankton. The region has a spring bloom which is of short duration at the oceanic sites and occurs earliest on the Celtic Sea shelf; phytoplankton biomass in the summer months is greatest at La Chapelle Bank. Photosynthetic pigments analyses indicate that prymnesiophytes are present throughout the year and are often the dominant group of phytoplankton; diatoms are most abundant in the spring bloom. Primary production is estimated to be ca. 160
gC
m
−2
a
−1, with cells <5
μm in diameter accounting for almost half of the annual primary production. New production is estimated to be equivalent to 80
g
C
m
−2
a
−1; the
f-ratio is generally <0.25 during the summer and autumn months, 0.7–0.8 during the spring bloom, and ca. 0.5 during the winter.
Microzooplankton biomass and herbivory were measured from April to October at the Goban Spur regions. The biomass of mesozooplankton was determined from the records of the Continuous Plankton Recorder (CPR) survey, and was used to estimate the amount of primary production removed by mesozooplankton grazing. Bacterial production is estimated to be ca
. 12
g
C
m
−2
a
−1. The sum of microzooplankton and mesozooplankton grazing and the carbon demands of bacteria were significantly lower than primary production from November through May, but heterotrophic processes were quantitatively greater than phytoplankton production from July to October. The data suggest that up to 62
g
C
m
−2
a
−1 of primary production was not grazed by micro- or mesozooplankton in the surface mixed layer, or utilised directly by bacteria. Depending on the region, up to 38% of the primary production at the Celtic Sea margin was apparently not grazed in the surface mixed layer and would be available for heterotrophic organisms in mid-water and the benthos. The estimated respiration of the heterotrophic community of the surface mixed layer estimated also suggested that between 37% and 60% of the carbon fixed by photosynthesis in the euphotic zone was not remineralised in the surface mixed layer.
Data from satellite remote sensing are used in conjunction with the experimental data to extend the seasonal coverage of the observations made in OMEX I. The archive of the coastal zone color scanner provides mean monthly values of chlorophyll concentration, and these agree well with the seasonal variation of “green colour” of the CPR survey. Primary production has been estimated from the satellite-derived chlorophyll concentrations for the period April–September and is calculated to be 90
g
C
m
−2 for the 6-month period; the estimated production for the same period from in situ experiments suggests that primary production was ca. 116
g
C
m
−2. Nitrate concentrations in the surface water were correlated with sea-surface temperature, and this relationship was applied to temperature measurements from the advanced very high resolution radiometer sensor to estimate the potential nitrate concentrations over the region. The
f-ratio was related to nitrate concentration by a simple hyperbolic function (
r
2=0.73). which was applied to the images of potential nitrate concentration for the region to estimate new production based on satellite data. For the period April through September, new production was calculated to be 46
g
C
m
−2 from satellite estimates of temperature, nitrate, and
f-ratio, which compares favourably with the estimated new production of 57
g
C
m
−2 by direct measurement.
Presents a collection of slides covering the following topics: remote marine location observations; low power low bandwidth marine environments; ocean observations; mooring technology; control ...autonomy; power autonomy; communication autonomy; Eulerian observatories; EuroSITES; deep ocean fixed point observatories; and MBARI Ocean Observing System (MOOS).
Konferansebidrag tilknyttet fortsettelsen av OceanObs`09 konferansen : Observations and Information for Society (Vol. 1), Venice, Italy, 21-25 September 2009, Hall, J., Harrison, D.E. & Stammer, D., ...Eds., ESA Publication WPP-306
The observation of biogeochemical cycles and ecosystems has traditionally been based on ship-based platforms. The obvious consequence is that the measured properties have been dramatically undersampled. Recent technological advances in miniature, low power biogeochemical sensors andautonomous platforms open remarkable perspectives for observing the “biological” ocean, notably at criticalspatio-temporal scales which have been out of reach until present. The availability of this new observation technology thus makes it possible to envision the development of a globally integrated observation system that would serve both scientific as well as operational needs. This in situ systemm should be fully designed and implemented in tight synergy with two other essential elements of an ocean observation system, first satellite ocean color radiometry and second advanced numerical models of biogeochemical cycles and ecosystems.
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