RRS Discovery D361 (GA06)

Cruise summary report

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Cruise Info.

Ship name (ship code)

RRS Discovery (74E3)

Cruise identifier

D361 (GA06)

Cruise period

2011-02-07 — 2011-03-19

Status

Completed

Port of departure

Santa Cruz de Tenerife, Spain

Port of return

Santa Cruz de Tenerife, Spain

Purpose

Research

Objectives

The cruise D361 forms part of a study entitled 'Physical and chemical forcing of diazotrophy in the (sub)-tropical Atlantic Ocean'. The study is investigating the potential influence of iron and phosphorus availability on nitrogen fixation in regions of the tropical Atlantic Ocean. The cruise also undertakes deep trace metal clean CTD casts as part of the International GEOTRACES programme. The purpose of the cruise therefore is to undertake measurements of dissolved and particulate iron and phosporpus availability, their spatial and temporal variations, and their impact on diazotrophy in the surface ocean.

Aim: To quantify the supply and determine the biogeochemical cycling of Fe and other nutrients, and relate this to N2 fixation, diazotroph species distribution and N* fields.
1. Quantify the distribution of nutrients and trace metals: Quantify surface water and water column distributions of dissolved inorganic/organic N, P, Fe, and DAl, DMn and particulate P, N, Fe, Al, Mn.
2. Quantify the rate of Fe, Al, Mn, P and N supply to surface waters: Assess the source fluxes of the key elements for diazotrophs and source tracers to the surface ocean from atmospheric deposition and internal transport via diapycnal mixing and lateral advection.
3. Identify the source of subsurface Fe enrichment: Identify whether Fe-rich subsurface waters of the tropical North Atlantic thermocline originate from the atmosphere or the shelf using Fe distributions and Al, Mn, and O2 source tracers.
4. Quantify the diazotrophic response to Fe, phosphate, DOP supply: Relate the spatial distributions of inorganic Fe and organically complexed Fe, and phosphate and DOP to diazotrophy. The specific uptake of Fe, phosphate and DOP by the whole microbial community and Trichodesmium will be assessed by shipboard incubations, radiotracer techniques and enzyme bioassays. In addition, we will identify the connection between N2 fixation rates and diazotroph community structure, by comparing size fractionated 15N2-derived rates of N2 fixation (Fig. 1) with abundance and diversity of diazotrophs using nifH phylogeny.
Objective 5: Investigate how the large scale transport pathways of Fe and P influence the N* distribution: Use fine-scale isopycnic model to reveal the large-scale transport pathways of Fe and P in the (S)-T Atlantic, and their effect on the N* distribution.

Chief scientist

Eric Pieter Achterberg (University of Southampton School of Ocean and Earth Science)

Project

GEOTRACES

Cruise report

(8.25 MB)

Ocean/sea areas

General

North East Atlantic Ocean (limit 40W)
South Atlantic Ocean

Specific

Tropical North and South Atlantic Ocean

Measurements

Physical oceanography

CTD stations

Quantity: number of profiles = 8
Description: 7 + 1test CTD stations for Th-234 measurements. 6 Shallow (500 m) and two deep CTD profiles (1000m) were sampled

CTD stations

Quantity: number of profiles = 40
Description: 21 Stainless steel; 19 titanium CTD profiles. Shallow (500 m) and full depth.

Subsurface temperature and salinity measurements

Quantity: track kilometres = 8000
Description: Ship fitted underway data (surface temperature, salinity, fluorescence and transmissivity, bathymetry). Ship fitted meterological instruments (wind speed/direction incident light, PAR etc)

Current profiler (eg ADCP)

Quantity: track kilometres = 8000
Description: Vessel mounted ADCP (75kHz)

Other physical oceanographic measurements

Quantity: number of profiles = 15
Description: Turbulence profiler

Chemical oceanography

Oxygen

Quantity: number of stations = 21
Description: Dissolved oxygen (µmol l-1) discrete samples from vertical profiles - stainless steel (10depths) and titanium rosettes (4-16 depths). Analysed onboard using PC-controlled potentiometric system and modified Winkler method.

Carbon dioxide

Quantity: number of stations = 37
Description: CTD Vertical profiles: Dissolved Inorganic Carbon, Dissolved Organic Carbon, Alkalinity

Carbon dioxide

Quantity: activity duration in days = 25
Description: Dissolved Inorganic Carbon Automated underway samples

Phosphate

Quantity: number of samples = 224
Description: Surface sampling Fish underway samples

Phosphate

Quantity: number of stations = 42
Description: Micromolar Nutrients CTD Vertical profiles

Nitrate

Quantity: number of stations = 42
Description: Micromolar Nutrients CTD Vertical profiles

Nitrite

Quantity: number of stations = 42
Description: Micromolar Nutrients CTD Vertical profiles

Silicate

Quantity: number of stations = 42
Description: Micromolar Nutrients CTD Vertical profiles

Alkalinity

Quantity: number of samples = 128
Description: Alkalinity Underway samples

Alkalinity

Quantity: number of stations = 37
Description: CTD Vertical profiles: Dissolved Inorganic Carbon, Dissolved Organic Carbon, Alkalinity

Quantity: number of samples = 360
Description: pH Underway samples

Trace elements

Quantity: number of samples = 115
Description: Unfiltered seawater for total dissolvable trace metal measurements was collected from the underway fish along the cruise track. Samples will be analysed after a minimum of 4 months at the National Oceanography Centre, Southampton by Isotope Dilution-ICPMS

Trace elements

Quantity: number of samples = 57
Description: Unfiltered seawater samples were collected and analysed on board for dissolved Fe(II) using Flow Injection with Chemiluminescence detection.

Trace elements

Quantity: number of samples = 200
Description: Filtered seawater samples for the detemination of total dissolved cobalt were collected from the underway fish along the cruise track. Samples will be determined using Flow Injection Analysis at the University of Plymouth

Trace elements

Quantity: number of samples = 371
Description: Particulate samples collected on PES filters from the trace metal OTE bottles deployed on the Titanium Rosette. Samples will be analysed using ICP-MS at the university of Plymouth.

Trace elements

Quantity: number of samples = 368
Description: Filtered seawater samples for determination of total dissolved cobalt collected from the Titanium Rosette. Samples will be determined using Flow Injection Analysis at the University of Plymouth

Trace elements

Quantity: number of samples = 180
Description: Unfiltered seawater for total dissolvable trace metal measurements was collected from the Titanium Rosette. Samples will be analysed after a minimum of 4 months at the National Oceanography Centre, Southampton by Isotope Dilution-ICPMS

Trace elements

Quantity: number of samples = 50
Description: 0.4 µm filtered seawater for iron ligands was collected from the Titanium Rosette. Samples were stored frozen (-20C) for analysis at the National Oceanography Centre, Southampton by Competitive Ligand Exchange-Cathodic Stripping Voltammetry.

Trace elements

Quantity: number of samples = 50
Description: Filtered seawater samples for iron isotopes collected from the trace metal OTE bottles deployed on the Titanium Rosette. Samples will be analysed using ICP-MS at the University of Southampton.

Trace elements

Quantity: number of samples = 213
Description: Filtered seawater samples for the detemination of dAl (H), dFe (G) and dissolved trace metals (I) were collected from the underway fish along the cruise track. Samples for dAl and dFe were analysed on board using Flow Injection Analysis. Dissolved trace metals will be analysed at the National Oceanography Centre, Southampton by Isotope Dilution-ICPMS

Trace elements

Quantity: number of samples = 369
Description: Filtered seawater samples for determination of dissolved aluminium and iron (dAl (H) and dFe (G)) collected from the Titanium Rosette. Samples have been analysed on board using Flow Injection Analysis.

Other chemical oceanographic measurements

Quantity: number of samples = 114
Description: Rates of alkaline phosphatase activity were determined from water samples taken from 6 depths from the stainless steel CTD (114 rate measurements). Rates were determined by the change in fluoresence of the substrate MUFP and calibrated using the standard MUF. Fluoresence was determined using a Turner 10Au field fluorometer. Rates were determined onboard by Claire Mahaffey

Other chemical oceanographic measurements

Quantity: number of samples = 111
Description: Unfiltered seawater samples were collected and analysed on board for the determination of hydrogen peroxide using Flow Injection with Chemiluminescence detection.

Other chemical oceanographic measurements

Quantity: number of samples = 18
Description: Trichodesmium colonies were collected from plankton nets deployed in the upper 30m of the water column. 10-20 Trichodesmium colonies were placed in filtered or unfiltered seawater and rates of 33P-phosphate and alkaline phosphatase activity.

Other chemical oceanographic measurements

Quantity: number of samples = 114
Description: Samples collected from the stainless steel rosette and FISH for 33phosphate uptake rates of the bulk community. Incubations conducted on board by Sarah Reynolds

Biology and fisheries

Primary productivity

Quantity: number of samples = 311
Description: Incubations with 15N2 and H13CO3 to measure uptake of inorganic carbon and dinitrogen by the phytoplankton and bacterial community

Phytoplankton pigs (eg chlorophyll, fluorescence)

Quantity: activity duration in days = 27
Description: Continuous fluorescence data collected using a Chelsea Scientific instruments FASTtrackTM Fast Repetition Rate fluorometer (FRRf) that was attached to the ships non-toxic underway system.

Phytoplankton pigs (eg chlorophyll, fluorescence)

Quantity: number of samples = 147
Description: Seawater samples from the stainless CTD were filtered onto GF/Fs to measure chlorophyll a concentration. Filters were submerged in 90% acetone for 24 hours and analysed onboard using a fluorometer. Samples were also collected from the continuous towed FISH supply (200 more samples).

Particulate organic matter (inc POC, PON)

Quantity: number of samples = 137
Description: Seawater samples from the stainless CTD were filtered onto pre-ashed GF/Fs to measure POC/PON/15N tzero. Filters will be analysed using mass spectrometry. Samples were also collected from the continuous FISH supply (78 more samples).

Particulate organic matter (inc POC, PON)

Quantity: number of deployments = 8
Description: 7 + 1test SAPS deployments, 53 and 1 micron mesh sizes x 3 depths (up to 500m) for POC, PON, BSi and PIC analyses.

Particulate organic matter (inc POC, PON)

Quantity: number of samples = 114
Description: Filter samples for the determination of particulate phosphorus were collected from the stainless steel rosette. Concentrations will be determined by high temperature combustion and acid hydrolysis and subsequent phosphate analysis by Sarah Reynolds and Claire Mahaffey at the University of Liverpool.

Particulate organic matter (inc POC, PON)

Quantity: number of samples = 311
Description: Incubations with 15N2 and H13CO3 to measure uptake of inorganic carbon and dinitrogen by the phytoplankton and bacterial community

Dissolved organic matter (inc DOC)

Quantity: number of samples = 343
Description: Filtered seawater samples for the determination of dissolved organic phosphorus collected from the stainless steel (0-500m, 183 samples) and titanium rosette (below 500m, 133 samples). Samples will be determined by UV digestion and subsequent phosphate analysis by Sarah Reynolds and Claire Mahaffey at the University of Liverpool. Samples were also collected from the FISH (37 samples).

Dissolved organic matter (inc DOC)

Quantity: number of stations = 37
Description: CTD Vertical profiles: Dissolved Inorganic Carbon, Dissolved Organic Carbon, Alkalinity

Dissolved organic matter (inc DOC)

Quantity: number of samples = 167
Description: Filtered seawater samples for the determination of enzyme hydrolysable phosphorus collected from the stainless steel rosette (0-500m, 183 samples). Samples will be determined by enzyme assays by Sarah Reynolds and Claire Mahaffey at the University of Liverpool. Samples were also collected from the FISH (37 samples).

Biochemical measurements (eg lipids, amino acids)

Quantity: number of samples = 127
Description: Seawater samples from the stainless CTD were filtered onto GF/Fs to measure heme b concentration. Filters will be analysed using high performance liquid chromatography with diode array spectrophotometry. Samples were also collected from the continuous FISH supply (79 more samples).

Biochemical measurements (eg lipids, amino acids)

Quantity: number of samples = 116
Description: Filtered seawater samples for proteomic analyses were collected from the stainless steel CTD (0-1000m, 81 samples), and the SAPS deployments (60-500m, 35 samples). Samples will be analysed by Elizabeth Sargent at the National Oceanography Centre, Southampton

Phytoplankton

Quantity: number of samples = 106
Description: Whole water samples that were collected from the stainless steel CTD (0-500m, 63 samples) and the marine snow catcher (35-100m, 13 samples), and concentrated samples that were collected from the nets (30 samples) were preserved in lugol's iodine for phytoplankton community assessments. Assessments will be carried out by Elizabeth Sargent at the National Oceanography Centre, Southampton.

Pelagic bacteria/micro-organisms

Quantity: number of hauls = 37
Description: Collected Trichodesmium colonies from plankton net hauls, each haul included 2 or 3 nets on the same line and were either 20 µm or 100 µm mesh nets. Picked Trichodesmium colonies were filtered onto suitable filters and frozen for analysis back at NOCS. Analysis will aim to relate the mRNA expression with the stoichiometric elemental composition.

Pelagic bacteria/micro-organisms

Quantity: number of samples = 352
Description: Filters of 0.2µm filtered seawater to assess the community diversity and abundance of the nifH gene (a marker gene for nitrogen fixation).

Other biological/fisheries measurement

Quantity: number of samples = 91
Description: Seawater samples from the stainless CTD were used to measure in situ nitrogen fixation rates. Samples were 'spiked' with 15N2 gas and incubated for 24 hours. Samples were then filtered onto pre-ashed GF/Fs and dried for a further 24 hours. Samples will be analysed using mass spectrometry.

Other biological/fisheries measurement

Quantity: number of stations = 20
Description: Water samples were collected for the estimation of whole microbial community iron uptake using a 55Fe tracer technique. Water was collected from the underway trace clean metal fish. Incubations were performed over 10-12 hours.

Other biological/fisheries measurement

Quantity: number of stations = 12
Description: Samples of trichodesimum were collected using net hauls for the estimation of colony specific iron uptake using a 55Fe tracer technique. Colonies were picked and rinsed 3 times in filtered trace clean seawater collected from the underway trace clean metal fish. Incubations were then performed over 10-12 hours in seawater collected in the same manner.

Meteorology

Routine standard measurements

Atmospheric chemistry

Quantity: number of samples = 78
Description: High volume aerosol samples (1 m3 min-1) for determination of trace metals (TM), major ions (MI) and metal isotopes (ISO) upon return to the UK. TM and MI samples were size segregated using a cascade impactor, ISO samples were bulk only. To avoid contamination from the ships funnel, a wind sector controller was used to ensure samples were only collected when the relative wind direction was from the bows.

Atmospheric chemistry

Quantity: number of samples = 7
Description: Rainwater samples for determination of trace metal and major ion concentrations upon return to the UK.

Data held at BODC

Get data

Series/Profiles

47 CTD/STD cast

Reference numbers
Transmittance and attenuance of the water column
Salinity of the water column
Temperature of the water column
Vertical spatial coordinates
Dissolved oxygen parameters in the water column
Density of the water column
Electrical conductivity of the water column
Chlorophyll pigment concentrations in water bodies

[Show series]

[Hide series]

BODC id	Date/Time	Location
1057668	2011-02-22 02:18:55 — 2011-02-22 03:21:50	12° 35' 39" N 17° 55' 11" W
1057712	2011-02-22 19:50:41 — 2011-02-22 19:55:12	12° 36' 35" N 17° 34' 21" W
1057804	2011-02-25 08:09:01 — 2011-02-25 09:50:43	12° 35' 7" N 23° 33' 46" W
1057841	2011-02-26 08:09:18 — 2011-02-26 09:56:12	12° 18' 4" N 25° 9' 12" W
1058008	2011-03-10 06:35:11 — 2011-03-10 06:48:08	8° 20' 21" N 28° 19' 55" W
1058045	2011-03-11 07:53:22 — 2011-03-11 09:44:12	10° 37' 28" N 28° 44' 5" W
1058069	2011-03-12 07:15:31 — 2011-03-12 07:30:48	12° 3' 15" N 28° 58' 48" W
1058101	2011-03-14 13:44:56 — 2011-03-14 15:39:06	17° 25' 56" N 28° 23' 6" W
1057656	2011-02-22 00:46:05 — 2011-02-22 01:04:26	12° 35' 13" N 17° 54' 47" W
1057785	2011-02-24 12:49:28 — 2011-02-24 14:13:07	12° 34' 25" N 21° 49' 1" W
1057828	2011-02-26 06:35:55 — 2011-02-26 06:51:58	12° 18' 0" N 25° 7' 40" W
1057853	2011-03-03 15:00:43 — 2011-03-03 15:20:39	7° 13' 19" S 24° 59' 37" W
1057933	2011-03-06 08:02:36 — 2011-03-06 09:58:07	1° 9' 47" S 25° 48' 11" W
1057945	2011-03-07 06:37:54 — 2011-03-07 06:51:19	1° 9' 24" N 26° 2' 45" W
1057957	2011-03-07 07:50:04 — 2011-03-07 09:04:39	1° 9' 39" N 26° 3' 13" W
1058113	2011-03-15 06:39:22 — 2011-03-15 07:03:17	19° 6' 54" N 28° 7' 51" W
1057644	2011-02-18 09:54:21 — 2011-02-18 10:11:17	27° 46' 37" N 16° 13' 40" W
1057797	2011-02-25 06:38:45 — 2011-02-25 06:54:24	12° 35' 5" N 23° 33' 25" W
1057889	2011-03-05 06:36:24 — 2011-03-05 06:50:20	3° 15' 40" S 25° 31' 13" W
1057994	2011-03-09 07:56:36 — 2011-03-09 09:11:59	5° 40' 8" N 27° 30' 44" W
1058021	2011-03-10 07:52:19 — 2011-03-10 09:31:26	8° 21' 0" N 28° 20' 32" W
1058057	2011-03-12 02:07:55 — 2011-03-12 04:00:57	12° 1' 57" N 28° 58' 49" W
1058094	2011-03-14 07:03:44 — 2011-03-14 07:14:56	17° 23' 56" N 28° 23' 41" W
1058125	2011-03-15 10:11:11 — 2011-03-15 10:34:27	19° 10' 12" N 28° 6' 55" W
1057632	2011-02-17 14:16:12 — 2011-02-17 14:30:16	28° 14' 7" N 16° 12' 52" W
1057681	2011-02-22 07:02:28 — 2011-02-22 07:17:42	12° 35' 27" N 17° 42' 48" W
1057693	2011-02-22 11:51:42 — 2011-02-22 12:16:01	12° 36' 35" N 17° 42' 56" W
1057724	2011-02-22 20:32:48 — 2011-02-22 20:35:50	12° 36' 43" N 17° 34' 22" W
1057736	2011-02-22 21:24:39 — 2011-02-22 21:28:52	12° 35' 17" N 17° 34' 20" W
1057748	2011-02-23 05:34:26 — 2011-02-23 05:48:57	12° 34' 1" N 18° 49' 24" W
1057761	2011-02-23 07:05:14 — 2011-02-23 08:36:37	12° 32' 54" N 18° 49' 47" W
1057877	2011-03-04 03:39:27 — 2011-03-04 03:57:05	7° 13' 6" S 24° 59' 34" W
1057970	2011-03-08 07:51:25 — 2011-03-08 09:26:38	3° 20' 58" N 26° 49' 32" W
1058070	2011-03-13 06:35:25 — 2011-03-13 06:49:40	15° 30' 30" N 28° 47' 11" W
1057908	2011-03-05 16:44:12 — 2011-03-05 17:25:03	2° 57' 44" S 25° 36' 53" W
1057921	2011-03-06 06:41:43 — 2011-03-06 06:53:16	1° 10' 23" S 25° 47' 38" W
1057969	2011-03-08 06:35:46 — 2011-03-08 06:51:44	3° 19' 48" N 26° 48' 37" W
1057619	2011-02-15 09:58:12 — 2011-02-15 10:14:39	28° 18' 45" N 16° 7' 18" W
1057773	2011-02-24 06:42:50 — 2011-02-24 06:58:10	12° 34' 37" N 21° 49' 4" W
1058033	2011-03-11 06:33:37 — 2011-03-11 06:48:17	10° 37' 36" N 28° 43' 52" W
1057620	2011-02-16 09:52:04 — 2011-02-16 10:51:07	28° 18' 59" N 16° 7' 32" W
1057700	2011-02-22 16:50:27 — 2011-02-22 17:00:59	12° 35' 13" N 17° 34' 6" W
1057816	2011-02-25 16:14:34 — 2011-02-25 16:42:44	12° 35' 16" N 23° 34' 44" W
1057865	2011-03-03 16:41:25 — 2011-03-03 18:38:57	7° 12' 55" S 24° 59' 54" W
1057890	2011-03-05 07:51:38 — 2011-03-05 09:40:09	3° 14' 54" S 25° 32' 29" W
1057982	2011-03-09 06:35:42 — 2011-03-09 06:54:02	5° 39' 42" N 27° 29' 56" W
1058082	2011-03-13 07:47:58 — 2011-03-13 09:19:36	15° 30' 20" N 28° 47' 39" W

Discrete samples

234 All plastic clean surface pumped supply

Concentration of inorganic halogens in water bodies
Nitrite concentration parameters in the water column
Phosphate concentration parameters in the water column
Silicate concentration parameters in the water column
Radioactivity in water bodies
Nitrate concentration parameters in the water column
Dissolved metal concentrations in the water column

24 Atmospheric air sampling pump

Sulphur species concentrations in the atmosphere
Metal concentrations in the atmosphere
Concentration of nitrogen species in the atmosphere
Concentration of inorganic halogens in the atmosphere

22 CTD frame plus rosette sampler

Total dissolved inorganic carbon (TCO2) concentration in the water column
Dissolved total and organic nitrogen concentrations in the water column
Nitrite concentration parameters in the water column
Phosphate concentration parameters in the water column
Salinity of the water column
Temperature of the water column
Dissolved oxygen parameters in the water column
Dissolved organic carbon concentration in the water column
Silicate concentration parameters in the water column
Radioactivity in water bodies
Nitrate concentration parameters in the water column
Alkalinity, acidity and pH of the water column

6 Rain water collector

Precipitation chemistry

Total dissolved inorganic carbon (TCO2) concentration in the water column
Dissolved total and organic nitrogen concentrations in the water column
Particulate metal concentrations in the water column
Concentration of inorganic halogens in water bodies
Nitrite concentration parameters in the water column
Phosphate concentration parameters in the water column
Salinity of the water column
Temperature of the water column
Dissolved oxygen parameters in the water column
Dissolved organic carbon concentration in the water column
Silicate concentration parameters in the water column
Particulate total and organic phosphorus concentrations in the water column
Radioactivity in water bodies
Nitrate concentration parameters in the water column
Alkalinity, acidity and pH of the water column
Dissolved metal concentrations in the water column

Resources

RRS Discovery D361 (GA06)

Cruise summary report

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