Niskin Bottle Samples Research Articles

Microplastic pollution in waters of the Antarctic coastal environment of Potter Cove (25 de Mayo Island/King George Island, South Shetlands)

Plastic pollution in the Southern Ocean around Antarctica is a growing concern, but many areas in this vast region remain unexplored. This study provides the first comprehensive analysis of marine microplastic (MPs) concentrations in Potter Cove, located near the Argentinian Carlini research station on 25 de Mayo/King George Island, Antarctica. Water samples were collected at 14 sites within the cove, representing various influences from the station's activities. Two sampling methods were used: a 5 L Niskin bottle and an in-situ filtering device called Microfilter, allowing for large water volumes to be filtered. MPs were found in 100 % of the samples. Microfilter samples ranged from 0.02 to 2.14 MPs/L, with a mean concentration of 0.44 ± 0.44 MPs/L. Niskin bottle samples showed concentrations from 0.40 to 55.67 MPs/L, with a mean concentration of 19.03 ± 18.21 MPs/L. The dominant types of MPs were anthropogenic black, transparent, and pink microfibers (MFs) measuring between 0.11 and 3.6 mm (Microfilter) and 0.06 to 7.96 mm (Niskin bottle), with a median length of 0.01 mm for both methods. Transparent and black irregular microfragments (MFRs) with diameters from 0.10 to 5.08 mm and a median diameter of 0.49 mm were also prevalent. FTIR-spectroscopy revealed the presence of 14 types of polymers. Cellulose-based materials and polyethylene terephthalate were the most abundant in MFs, while polyurethanes and styrene-based copolymers dominated in MFRs. MPs were more abundant near the Carlini station. Compared to other coastal Antarctic areas, the MPs in the cove were relatively abundant and mostly smaller than 1 mm. Local activities on the island were identified as the primary source of MPs in the cove, and the cyclonic water circulation likely affects the distribution of small-sized particles. To protect the ecosystem, reducing plastic usage, improving waste management, regulating MPs debris, and enhancing wastewater practices are essential.

Microbial diversity gradients in the geothermal mud volcano underlying the hypersaline Urania Basin.

Mud volcanoes transport deep fluidized sediment and their microbial communities and thus provide a window into the deep biosphere. However, mud volcanoes are commonly sampled at the surface and not probed at greater depths, with the consequence that their internal geochemistry and microbiology remain hidden from view. Urania Basin, a hypersaline seafloor basin in the Mediterranean, harbors a mud volcano that erupts fluidized mud into the brine. The vertical mud pipe was amenable to shipboard Niskin bottle and multicorer sampling and provided an opportunity to investigate the downward sequence of bacterial and archaeal communities of the Urania Basin brine, fluid mud layers and consolidated subsurface sediments using 16S rRNA gene sequencing. These microbial communities show characteristic, habitat-related trends as they change throughout the sample series, from extremely halophilic bacteria (KB1) and archaea (Halodesulfoarchaeum spp.) in the brine, toward moderately halophilic and thermophilic endospore-forming bacteria and uncultured archaeal lineages in the mud fluid, and finally ending in aromatics-oxidizing bacteria, uncultured spore formers, and heterotrophic subsurface archaea (Thermoplasmatales, Bathyarchaeota, and Lokiarcheota) in the deep subsurface sediment at the bottom of the mud volcano. Since these bacterial and archaeal lineages are mostly anaerobic heterotrophic fermenters, the microbial ecosystem in the brine and fluidized mud functions as a layered fermenter for the degradation of sedimentary biomass and hydrocarbons. By spreading spore-forming, thermophilic Firmicutes during eruptions, the Urania Basin mud volcano likely functions as a source of endospores that occur widely in cold seafloor sediments.

Combining laser diffraction, flow cytometry and optical microscopy to characterize a nanophytoplankton bloom in the Northwestern Mediterranean

The study of particle size distribution (PSD) gives insights on the dynamics of distinct pools of particles in the ocean, which reflect the functioning of the marine ecosystem and the efficiency of the carbon pump. In this study, we combined continuous particle size estimations and discrete measurements focused on phytoplankton to describe a spring bloom in the North West Mediterranean Sea. During April 2013, about 90 continuous profiles of PSD quantified through in situ laser diffraction and transmissiometry (the Laser in situ Scattering and Transmissiometry Deep (LISST-Deep), Sequoia Sc) were complemented by Niskin bottle samples for flow cytometry analyses, taxonomic identification by optical microscopy and pigments quantification. In the euphotic zone, the PSD shape seen by the LISST was fairly stable with two particle volume peaks covering the 2–11 µm and 15–109 µm size fractions. The first pool strongly co-varied with the chlorophyll fluorescence emitted by phytoplankton cells. In addition, over the 2–11 µm fraction, the LISST derived abundance was highly correlated with the abundance of nanophytoplankton counted by flow cytometry. Microscopy identified a phytoplankton community dominated by nanodiatoms and nanoflagellates. High correlation of LISST derived particle carbon and Particulate Organic Carbon and high nitrogen in the Particulate Organic Matter also supported a dominance of actively growing phytoplankton cells in this pool. The second, broader pool of particles covering sizes 15–109 µm was possibly microflocs coming from rivers and/or sediments. This study demonstrates the complementarity of continuous measurements of PSD combined with discrete measurements to better quantify size, abundance, biomass, and spatial (both vertical and horizontal) distribution of phytoplankton in open ocean environments.

An Alternative Method to Niskin Sampling for Molecular Analysis of the Marine Environment

The development of low-cost, open-source Remotely Operated Vehicle (ROV) systems has provided almost unrestricted access for researchers looking to monitor the marine environment in ever greater resolution. Sampling microbial communities from the marine environment, however, still usually relies on Niskin-bottle sampling (ROV or Conductivity-Temperature-Depth sampler (CTD) based), a method which introduces an inaccuracy and variability that is incompatible with metatranscriptomic analysis, for example. Here, we describe a versatile, easily-replicated platform which achieves in situ mRNA preservation, via the addition of RNAlater to filtered microbial cells, to enhance ROV or CTD functionality.

Niskin bottle sample collection aliases microbial community composition and biogeochemical interpretation

AbstractParticles able to settle distances of approximately a meter in 1–2 h are undersampled in water traditionally collected in Niskin bottles. Gardner (Limnol Oceanogr, 22, 764–768, 1977) demonstrated that particles sink into the space below the spout of Niskin bottles on timescales relevant to sample processing. We examined this effect on measurements of microbial abundance, community composition, and transparent stainable particles across an oxygen‐sulfide gradient in the Cariaco Basin. Within 1 h, modestly sized micro‐aggregates (> 16 μm) were not detected in samples drawn from the spout, but were abundant in the waters below the spout. Total transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP) were at least twice as abundant in the below‐spout samples as in spout‐collected water. Below‐spout samples accounted for four times more total particle surface area per mL than spout samples. Approximately 10% of all microbes were particle‐associated, which led to only small enrichments of total microbes in the below‐spout samples. However, fluorescent in situ hybridization (FISH) revealed five of seven clades surveyed were significantly more enriched in water below the spout than total cells, indicating (1) a small bias when enumerating total particles and microbes from spout samples and (2) a very strong bias for particular phylogenetic groups that are more prevalent on particles than the total community. In particular, sulfate‐reducing δ‐proteobacteria were consistently enriched in below‐spout samples collected at depths along the oxygen‐sulfide transition. Abundance of this functional group has potentially been underestimated in the past. Consequently, microbial diversity results derived from Niskin bottle samples should be cautiously applied when interpreting biogeochemical cycling.

What did we learn about ocean particle dynamics in the GEOSECS–JGOFS era?

Particles determine the residence time of many dissolved elements in seawater. Although a substantial number of field studies were conducted in the framework of major oceanographic programs as GEOSECS and JGOFS, knowledge about particle dynamics is still scarce. Moreover, the particulate trace metal behavior remains largely unknown. The GEOSECS sampling strategy during the 1970s focused on large sections across oceanic basins, where particles were collected by membrane filtration after Niskin bottle sampling, biasing the sampling toward the small particle pool. Late in this period, the first in situ pumps allowing large volume sampling were also developed. During the 1990s, JGOFS focused on the quantification of the “exported carbon flux” and its seasonal variability in representative biogeochemical provinces of the ocean, mostly using sediment trap deployments. Although scarce and discrete in time and space, these pioneering studies allowed an understanding of the basic fate of marine particles. This understanding improved considerably, especially when the analysis of oceanic tracers such as natural radionuclides allowed the first quantification of processes such as dissolved-particle exchange and particle settling velocities. Because the GEOTRACES program emphasizes the importance of collecting, characterizing and analyzing marine particles, this paper reflects our present understanding of the sources, fate and sinks of oceanic particles at the early stages of the program.

Hydrolytic ectoenzyme activity associated with suspended and sinking organic particles within the anoxic Cariaco Basin

Ectohydrolase activities of suspended microbiota were compared to those associated with sinking particles (sed-POM) retrieved from sediment traps deployed in the permanently anoxic Cariaco Basin. In shore-based assays, activities of aminopeptidase, β-glucosidase, chitinase and alkaline phosphatase were measured in samples obtained from oxic and anoxic depths using MUF- and MCA-labeled fluorogenic substrate analogs. Hydrolysis potentials for these enzymes in the seston varied widely over the nine cruises sampled (8 Nov 1996–3 May 2000) and among depths (15–1265 m); from <10 to over 1600 nM d −1 hydrolysate released, generally co-varying with one another and with suspended particulate organic carbon (POC) and particulate nitrogen (PN). Hydrolytic potentials, prokaryotic abundances and POC/PN concentrations in sinking debris were 400–1.3×10 7 times higher than in comparable volumes of seawater. However when normalized to PN, hydrolytic potentials in sediment trap samples were not demonstrably higher than in Niskin bottle samples. We estimate that PN pools in sediment trap samples were turned over 2–1400 times (medians=7–26 x) slower by hydrolysis than were suspended PN pools. Median prokaryotic growth rates (divisions d −1) in sinking debris were also ∼150 times slower than for bacterioplankton. Hydrolytic potentials in surface oxic waters were generally faster than in underlying anoxic waters on a volumetric basis (nM hydrolysate d −1), but were not significantly ( p>0.05) different when normalized to PN or prokaryote abundances. Alkaline phosphatase was consistently the most active ectohydrolase in both sample types, suggesting that Cariaco Basin assemblages were adapted to decomposing phosphate esters in organic polymers. However, phosphorus limitation was not evident from nutrient inventories in the water column. Results support the hypothesis that efficiencies of polymer hydrolysis in anoxic waters are not inherently lower than in oxic waters.

A 1-D vertical multiple grain size model of suspended particulate matter in combined currents and waves in shelf seas

Accurate representation of light attenuation by inorganic suspended particulate matter (SPM) is one of the major factors limiting realism in coupled physical‐biogeochemical models used to simulate primary production in shelf seas. The main problem is the accurate calculation of SPM concentrations. A multiple‐grain size advection‐diffusion method is presented, and results are compared to observations. The method has been incorporated in the 1‐D hydrodynamics model General Ocean Turbulence Model. Particular attention has been given to the representation of sediment pickup, which is based on upward diffusion of sediment from a reference concentration near the seabed. Also, a bulk approach is used where the dominant fraction governs the pickup of the other fractions. A seabed model using the active layer approach is included. Moreover, to better represent seasonal cycles in background SPM concentration, a temperature‐dependent kinematic viscosity is used, which modifies settling velocities and sediment pickup. Model results were tested against multiyear time series of surface observations of SPM using an Optical Backscatter sensor on “SmartBuoy” at two sites on the UK shelf and against suspended load observations obtained from Niskin bottle samples. It was found that at least four size fractions are required for reasonable predictions of the SPM concentration at the two sites: a coarse fraction representing the median grain size of the seabed sediments, two silt fractions responsible for most of the variability near the sea surface, and a clay fraction that provides a background concentration with slow variations in time. The method can easily be extended to 3‐D models.

LC-MS-MS aboard ship: tandem mass spectrometry in the search for phycotoxins and novel toxigenic plankton from the North Sea

Phycotoxins produced by various species of toxigenic microalgae occurring in the plankton are a global threat to the security of seafood resources and the health of humans and coastal marine ecosystems. This has necessitated the development and application of advanced methods in liquid chromatography coupled to mass spectrometry (LC-MS) for monitoring of these compounds, particularly in plankton and shellfish. Most such chemical analyses are conducted in land-based laboratories on stored samples, and thus much information on the near real-time biogeographical distribution and dynamics of phycotoxins in the plankton is unavailable. To resolve this problem, we conducted ship-board analysis of a broad spectrum of phycotoxins collected directly from the water column on an oceanographic cruise along the North Sea coast of Scotland, Norway, and Denmark. We equipped the ship with a triple-quadrupole linear ion-trap hybrid LC-MS-MS system for detection and quantitative analysis of toxins, such as domoic acid, gymnodimine, spirolides, dinophysistoxins, okadaic acid, pectenotoxins, yessotoxins, and azaspiracids (AZAs). We focused particular attention on the detection of AZAs, a group of potent nitrogenous polyether toxins, because the culprit species associated with the occurrence of these toxins in shellfish has been controversial. Marine toxins were analyzed directly from size-fractionated plankton net tows (20 microm mesh size) and Niskin bottle samples from discrete depths, after rapid methanolic extraction but without any further clean-up. Almost all expected phycotoxins were detected in North Sea plankton samples, with domoic acid and 20-methylspirolide G being most abundant. Although AZA was the least abundant of these toxins, the high sensitivity of the LC-MS-MS enabled detailed quantification, indicating that the highest amounts of AZA-1 were present in the southern Skagerrak in the 3-20 microm size-fraction. The direct on-board toxin measurements enabled isolation of plankton from stations with high AZA-1 levels and from the most suspicious size-fraction, i.e. most likely to contain the AZA-producer. A large number (>100) of crude cultures were established by serial dilution and later screened for the presence of AZAs after several weeks growth. From one crude culture containing AZA, a small dinoflagellate was subsequently isolated and brought into pure culture. We have thus proved that even sophisticated mass spectrometers can be operated in ship laboratories without any limitation caused by vibrations of the ship's engine or by wave movement during heavy seas at wind forces up to nine Beaufort. On-board LC-MS-MS is a valuable method for near real-time analysis of phycotoxins in plankton for studies on bloom dynamics and the fate of toxins in the food web, and for characterization and isolation of putatively toxigenic organisms.

Characterization of azaspiracids in plankton size-fractions and isolation of an azaspiracid-producing dinoflagellate from the North Sea

Azaspiracids (AZAs) are a group of lipophilic polyether toxins implicated in incidents of shellfish poisoning in humans, particularly in northern Europe. In an attempt to establish the biogeographical distribution of AZA toxins, their association with plankton size-fractions, and to confirm the identity of the causative species responsible for human poisoning, a month-long oceanographic study was undertaken in coastal North Sea waters. The occurrence and abundance of AZA analogues was measured by on board triple quadrupole mass spectrometry coupled to liquid chromatography (LC-MS/MS). In size-fractionated plankton samples collected by net tows (20 μm mesh-size), by pumping from discrete depths and from Niskin entrapment bottle casts to fixed depths, AZA-1 was consistently the major azaspiracid component. In eastern Scottish coastal waters, the highest amounts of AZA-1 in net tow samples were in the 50–200 μm fractions, with lesser amounts detected in the >200 μm and 50–20 μm fractions. At these stations, the 50–200 μm fractions were rich in the ciliate Favella ehrenbergii. Cells of F. ehrenbergii isolated by microcapillary indeed contained AZA-1, but isolated cells grown and fed the non-toxic dinoflagellate Scrippsiella trochoidea for one week failed to contain any detectable AZA-1—evidence that F. ehrenbergii is merely a vector for AZA. Detailed analysis of plankton from Niskin bottle samples from around the North Sea typically showed highest amounts of AZA in the 3–20 μm fraction. From this fraction, a large number of crude cultures were established and subsequently screened for the presence of AZAs. A small photosynthetic thecate dinoflagellate, provisionally designated as strain 3D9, was isolated by microcapillary and brought into pure culture. This dinoflagellate strain was found to produce AZA-1, AZA-2 and an isomer of AZA-2. Sequence comparisons by molecular genetic techniques also indicated that this genotype was present in field samples rich in AZA. This discovery of a novel causative dinoflagellate for AZA toxicity essentially explains the lack of correlation of AZA with the abundance and distribution of the previously postulated culprit species Protoperidinium crassipes. We instead propose that such large phagotrophic dinoflagellates can act as an AZA vector following grazing upon a proximal source, such as the dinoflagellate 3D9 strain.

Effects of a sewage plume on the biology, optical characteristics, and particle size distributions of coastal waters

The effect of a sewage plume on the biology, optical characteristics, and particle size distributions of coastal waters was evaluated around the Sand Island, Hawaii, outfall diffuser. In situ physical and biooptical data and Niskin bottle samples were collected during a 1‐week cruise from September 25 to October 1, 1994. One or two layers affected by sewage could be distinguished in the water column: recently discharged (“new”) sewage plume waters and “old” plume waters. In conditions characterized by high Froude number the distribution of chlorophyll fluorescence in new plume waters was the same as for ambient waters, while for low Froude number, chlorophyll fluorescence increased within the plume, demonstrating the importance of physical forcing on effluent and phytoplankton interactions. New plume waters were associated with at least 2.7‐fold increases in particle load, high concentrations of particles larger than 70 μm, increases in ammonium, phosphate, and silicate, and high levels of heterotrophic bacteria and Prochlorococcus compared to surrounding waters. Both new and old plume layers, but not phytoplankton layers, showed distinct increases in fluorescence for the excitation/emission (Ex/Em) wavelength pair Ex/Em=228/340 in nm, interpreted as particulate tryptophan‐like fluorescence. Such fluorescence may be useful as a new in situ real‐time indicator of waters affected by effluent discharges.

Field Calibration of a Microhole Potentiostatic Oxygen Sensor for Oceanic CTDs

Abstract A new type of oxygen sensor for use on oceanic profiling CTDs has a response time that ranges from 0.4 to 0.7 s, depending on temperature. This oxygen (O2) sensor was calibrated in the field against O2 concentrations that were determined from Winkler titrations of Niskin-bottle water samples. Calibration coefficients were obtained from single casts and composite casts. When casts were calibrated separately, the mean error in predicting O2 concentrations was 1.22 ± 0.72 µM O2, n = 19 casts, and was not significantly different from the error between Niskin-bottle samples, which was 1.01 ± 2.33 µm O2, n = 33 triplicate or duplicate bottles. When casts wore combined into a composite cast for an entire cruise, however, the mean error in the calibrations increased to 5.03 ± 4.06 µm O2, n = 19 casts. These results also indicate that only three Niskin bottles on a cast are required to obtain an error of 1.0 µm in predicted oxygen. For routine use, we recommend calibrating each cast separately using eithe...

Macroflocs from diatoms: in situ photography of particles in Bedford Basin, Nova Scotia

Observations of a diatom bloom by in situ photography showed that at the beginning of the bloom the diatoms occurred only as discrete cells and were limited to the surface mixed layer. Below the thermocline, suspended particulate matter concentrations were low and dominated by 200 to 350 p-~ diameter flocs composed mainly of fine-grained detritus and terrestrial sediment. Some time after the beginning of the bloom diatoms started to clump together into aggregate particles, many mm in diameter, composed of a loose network of cells. Flocculation promoted by the high particle concentrations and the development of normal marine surface stickiness caused the diatoms to settle through the thermocline. A progressive increase in the apparent robustness and density of the flocs occurred with depth. The macroflocs could only be detected using the in situ photographs. They did not survive normal Niskin bottle sampling, and Coulter Counter analysis produced particle spectra reflecting only the size of the constituent diatoms and sediment grains. Observations indicate that studies of particle size based on water samples give misleading results and the size of particulate matter in general has been considerably underestimated in past studies based on conventional sampling methods.

A continuous pump sampler for profiling copepods and chlorophyll in the upper oceanic layers

A continuous profiling pumping system has been developed for obtaining biological profiles of copepods, chlorophyll, temperature, and light irradiance in the upper mixed layers to depths of ≈ 100 m. The sampler minimizes the problem of zooplankton avoidance of pump intakes by entrapping animals in a descending plankton net and subsequently removing them by pumping on the cod end. Measured profiles of copepods and chlorophyll indicate a vertical resolution of ≈ 3 to 4 m resulting from mixing in the hose and pump for a sampler descent rate of 0.5 to 1.0 m s −1. The pumping system delivers ≈ 50 to 60 1 min −1 of seawater on deck. Residence time and mixing in the hose are estimated. Pump and Niskin bottle samples used in primary production measurements are compared and indicate minimal damage to organisms during the production measurements. Applications of the pumping system to production measurements are presented.