Formation of marine barite (BaSO4) concurrent with dissolution of acantharian celestite (Sr/Ba, SO4) was examined under laboratory conditions in this work. Acantharian cysts, composed of barium-enriched celestite (Ba/Sr mole fraction ∼0.003), were allowed to react for 21–158 days in small volumes of natural seawater (20 to 100 μl) sealed within Teflon tubes. In 17 trials, three experiments yielded single barite particles, and one experiment produced barite overgrowth on a siliceous particle. These observations are consistent with a barite formation pathway in which acantharian dissolution within microenvironments leads to BaSO4 supersaturation and subsequent barite formation. This work supports the significance of Acantharia as one potential source of strontium-rich barite particles that are ubiquitous in the oceanic water column.

Inductively coupled plasma mass spectrometry was used to analyze the Ba and Sr concentrations of the celestite (SrSO4) skeletons and cysts of individual acantharian specimens obtained from four diverse areas of the world’s oceans. Acantharian celestite Ba/Sr mole ratios (χBa/χSr) averaged 2.6×10-3 with minimum and maximum values of 6.1×10-4 and 2.5×10-2. Celestite Ba/Sr mole ratios were compared to dissolved Ba and Sr concentration ratios ([Ba2+]T/[Sr2+]T) derived from GEOSECS stations that most closely corresponded to acantharian collection sites. Resultant Ba/Sr distribution coefficients (DBa/Sr=(χBa/χSr)/([Ba2+]T/[Sr2+]T)) in diverse areas of the world’s oceans are on the order of three or larger. These data, in conjunction with observations of acantharian mediated Sr2+ depletions in the upper ocean, indicate that acantharians play a substantial role in the global oceanic Ba budget. Observation of Ba enrichments during celestite formation is consistent with expectations based on solidsolution–aqueous-solution precipitation dynamics and the much lower solubility of BaSO4 compared to SrSO4. Furthermore, the small solubility product of RaSO4 relative to SrSO4 and BaSO4 indicates that Ra should be enriched in both celestite and barite. Consequently, acantharians may have a substantial influence on the oceanic distributions of both Ba and Ra.

Free-drifting sediment traps deployed at 400, 1500, and 3200 m were used to collect particles near the US JGOFS Time-Series Station (31°49.5′N and 64°08.2′ W) in the Atlantic Ocean. Acantharian specimens isolated from our samples were abundant at the 400-m depth horizon and were rare to non-existent in our 1500-m traps. No specimens were detected in the 3200-m traps. This trend parallels those noted for the Pacific and has been linked to the oceans' SrCl profiles. Our collections revealed the presence of myriad, heretofore undocumented, minute SrSO4 particles. These particles are most likely related to the acantharian reproductive cycle. The extreme abundance of acantharians and acanthari-anderived particles may have implications beyond the oceans' Sr budgets. Barium/strontium molar ratios in acantharian-derived celestite on the order of 3 sx 10−3 indicate that acantharians may play an important role in oceanic Ba cycling.

A series of synchronous, 24-h experiments using sensor-equipped sediment traps revealed that higher particle collection rates were associated with higher approach velocieties. Surface-tethered traps with variable drag configurations provided distinct differences in approach velocities for paired 400 m deployments and paired 1500 m deployments. Small-scale hot-film hydrodynamics sensors located both inside and outside the sediment traps detected flow cells within the traps with velocities between 50 and 100% of the external fluid approach velocities. In conjunction with laboratory flume simulations, these observations reveal that particles do not settle gravitationally across trap apertures. Intead, particles are swept advectively into traps at the downstream portion of trap apertures, and most are then expelled at the upstream portions of trap apertures. Fluid flows detected inside the drifting traps, which ranged from 1.2 to 31 cm s−1,l probably overwhelm all but the strongest “swimmers” that interact with these sampling divices. At our two sampling horizons (400 and 1500 m), tether-line motions generated trap depth oscillations with a period of the order of 10 s and an amplitude of about 0.5 m. Such effects have not been accounted for in flume simulated of sediment traps collection experiments.

This chapter contains sections titled: Introduction and Background Sediment Trap Sampling Pre-Cruise Laboratory Preparation Sample Processing Sample Analyses Discussion

Free drifting sediment traps were deployed individually to make day-long collections of settling particulates at seven stations in the western North Pacific Ocean. Samples were taken between 70 and 2200 m along a longitudinal section between 16 and 50-degrees-N latitude.Radiolarian skeletons were mechanically isolated under a reflected light microscope. Subsequent gravimetrically determined radiolarian silica fluxes range from 0 to 4.43 mg m-2 day-1 and show significant and consistent increases at all depths with increasing latitude.Radiolarians also were counted and categorized into each of their three suborders: Nassellaria, Spumellaria and Phaeodaria. An inverse relationship is evident between the proportions of phaeodarians and polycystines (nassellarians plus spumellarians), with the phaeodarians increasing relative to the polycystines with increasing latitude.Although the absolute numbers of phaeodarians in the northern samples may not exceed the numbers of their polycystine counterparts in the south, the comparatively large and heavy phaeodarian skeletons contribute significantly to the increased silica fluxes noted in the north. This contribution, combined with a high susceptibility to dissolution, may signifiy that phaeodarians are important for the recycling of silica in the northern North Pacific.Spectrophotometric analyses of seven phaeodarian species and one species of colonial spumellarian show that silica constituted between 86 and 99% of the phaeodarians' skeletons and 75% of the spumellarians' skeletons.Non-radiolarian amorphous silica was mobilized by a selective chemical leach and quantified spectrophotometrically. Significant and consistent increases in the flux of this diatomaceous silica fraction (ranging from 0.14 to 47.0 mg m-2 day-1) are noted with increasing latitude. In almost all cases, diatomaceous silica fluxes are greater than those of the radiolarians. With the exception of some anomalously high percentages, radiolarian-derived silica ranges from 0 (only one sample) to 24% of the total amorphous silica flux.

Several recent studies have shown that large quantities of mineral dust from eastern Asia are transported through the atmosphere to the North Pacific each spring1–5. The paucity of information on mineral fluxes during individual dust events prompted a coordinated effort, Asian Dust Input to the Oceanic System (ADIOS), which simultaneously measured mineral fluxes in the atmosphere and upper water column during such an event. In March 1986 a major dust outbreak in China moved over the North Pacific Ocean and was detected downstream using changes in particle number, size and composition. Most striking was the presence of 'giant' (>75-μm) silica minerals found in atmospheric as well as water-column samples at the ADIOS sampling site (26° N, 155° W). Their appearance more than 10,000 km from their source cannot be explained using currently acknowledged atmospheric transport mechanisms. Furthermore, the large wind-blown minerals that dominated our samples are extremely rare in the long-term sedimentary record in the North Pacific.

Data on particulate strontium sulfate fluxes and strontium to chlorinity ratios were compared to provide insights into the strontium cycle of the North Pacific. Free-drifting sediment traps were used to derive large particle fluxes between depths of 100 and 3500 meters in the eastern and western North Pacific Ocean. Flux data revealed substantial quantities of acantharian skeletons and cysts (both made of strontium sulfate) settling through the upper kilometer of the water column. The greatest fluxes of celestite were detected at 400 meters. Minimal to nondetectable fluxes noted at and below 900 meters provide evidence that by this horizon, the majority of acantharian specimens had dissolved, thereby contributing to the pool of dissolved strontium. Growth and subsequent dissolution of acantharians in the upper kilometer are qualitatively consistent with the well-developed minimum and maximum strontium to chlorinity ratios that are consistently noted in these waters. These fluxes of particulate strontium and model calculations for fluxes of dissolved strontium indicate that acantharians play an important role in the ocean's strontium budget.

THE extrusion of sodium and accompanying potassium accumulation by red cells against electrochemical gradients is linked to the energy of cell glycolysis1,2. Active cation transport ceases at low temperatures, in the presence of iodoacetate or fluoride, and in the absence of glucose. Per contra, the process is unrelated to red-cell respiration, since transport is not influenced by cyanide, azide, carbon monoxide, methylene blue, pyruvate or malonate.