The RRS Discovery cruise 304 was conducted from 12 May to 6 June 2005 from and to Santa Cruz (Tenerife). The cruise was completed as part of the NERC founded RAPID programme to monitor the meridional overturning circulation at 26 N. The primary purpose was to service the eastern boundary and Mid-Atlantic Ridge part of the 26 N mooring array which had previously been serviced during the RRS Charles Darwin cruises 170 and 177. 12 moorings were successfully recovered, however two of the shallow eastern boundary moorings failed to release. Intense fishing activity at these sites is likely to be the cause. 12 mooring and four bottom pressure landers were re-deployed. Data from two bottom mounted inverted echosounders was uploaded via acoustic telemetry. A total of 10 CTD casts to calibrate the mooring sensors were carried out and 3 Argo floats (from the UK Met Office) were launched. The moored sensors are CTD loggers for the most part but also bottom pressure sensors, different types of current meters and inverted echosounders are used to determine the strength and structure of the meridional overturning circulation.

The main testable hypothesis of the proposed work is: Atmospheric inputs control rates of primary production and microbial diversity in oceanic waters where nutrients are limiting. The objectives of the project are to: 1. Obtain an improved temporal and spatial estimate of atmospheric dust inputs to the tropical N Atlantic through collections on a dedicated SOLAS process cruise. 2. Obtain an improved estimate of the seawater dissolution of N, P, Fe and Zn species from aerosol dust. 3. Determine the impact of atmospheric dust derived micronutrients on microbial community production and species diversity in the surface microlayer and underlying waters. In addition, researchers from the Archer/Geider group were on-board. The overall aim of their research was to determine the extent to which the photoprotective roles of DMSP and QAs influence their production rates in marine surface waters and hence, the production of their volatile breakdown products. The cruise objectives for this work were to: 1. relate DMSP and QAC concentrations to plankton community structure, light regime, photoinhibition, xanthophyll cycle and MAA accumulation in varying oceanic provinces and over diel cycles. 2. determine the potential for photoinhibition and DMSP/GBT turnover in natural phytoplankton in contrasting oceanic provinces. The cruise departed Tenerife on February 5, 2008, and we have conducted regular stations (typically 2 per day) along the cruise track. The track took us into the oligotrophic Atlantic waters, productive Cape Verde waters, and tropical waters with very high nitrogen fixation (judged initially from the Trichodesmium concentrations). The various researchers and groups have also started a range of biological experiments at different sites along the cruise track. We have encountered a major dust event in week 2, and then from week 3 of the cruise we encountered large amounts of dust. We have visited the TENATSO time series site near the Cape Verdes and have undertaken an extensive set of measurements there. We have collected the atmospheric dust for elemental analyses (at UEA and NOCS), and also to produce leachates which are used on board for biological experiments. We have undertaken sampling of the water column to analyse for dissolved and particulate metals, nutrients, dissolved organic matter, amino acids, hemes, thiols and phytochelatin synthase expression. In addition, nitrogen fixation measurements were undertaken, in tandem with nifh gene sampling. Nitrate uptake experiments have been conducted. Furthermore, bacterial phosphate uptake experiments have been undertaken using addition of collected dust. Halocarbon and DMS gas measurements have been conducted during the cruise. In addition, experiments have been undertaken by the Archer/Geider group on effects of high sun light exposure on DMS and GBT production. The cruise has been very successful with a minimum of lost time.

CD170 was a collaborative cruise with the Knorr cruise KN182_2. The latter cruise was conducted between 2 May 2005 and 26 May 2005. These cruises were completed as part of the UK Natural Environment Research Council (NERC) funded RAPID Programme and the US National Science Federation (NSF) funded MOCHA Programme to monitor the Atlantic Meridional Overturning Circulation at 26.5 degrees North. The primary purpose of both cruises was to service the 26.5 degrees North mooring array deployed in 2004 during RRS Discovery cruises D277 and D278. These cruises are the first annual refurbishment of this array.

The objective of cruise JC103 was to service the moorings of the RAPID 26°N project that are deployed to monitor the Atlantic Meridional Overturning Circulation. For each mooring instruments were recovered, data were downloaded and instruments were redeployed. A number of CTDs were made to calibrate the instruments from the moorings. During passage from port of Spain to Nassau trial CTDs were completed in the waters of the Turks and Caicos Islands. After departing Nassau on 29th April work commenced on the western boundary sub-array comprising of moorings WBADCP, WBAL, WB1, WB2, WB2l, WB2h, WB4 and WB4L. The ship returned to Nassau on 6th May to disembark one person before sailing east once again. The final mooring of the wester sub-array was serviced on 8th May before continuing east to the mid-Atlantic Ridge (MAR) sub-array. Work on the MAR sub-array commenced on 13th May at mooring MAR0. The other moorings in this sub-array were MAR1, MAR1L, MAR2, MAR3 and MAR3L were all completed by 18th May. On the following day the NOG mooring was deployed and as the ship transited to the astern sub-array the first of 5 Argo floats was deployed on 21st May. The eastern boundary sub-array starts at EB1, which was serviced on 23rd May. Following this moorings at EB1L, EBHi, EBH1, EBH2, EBh3,EBh4 and EBH4L in the following days up until 31st May. A number of CTDs were completed form 31st may to 2nd June.

These mooring operations were completed as a part of the United Kingdom Natural Environment Research Council (NERC) funded RAPID Programme to monitor the Atlantic Meridional Overturning Circulation at 26.5°N. The primary purpose of this cruise was to service the Eastern Boundary and Mid-Atlantic Ridge sections of the 26.5°N mooring array first deployed during RRS Discovery cruises D277 and D278 (SOC cruise report number 53), and serviced in 2005 during RRS Charles Darwin cruise CD177 (NOCS cruise report number 5), in 2006 on RRS Discovery cruise D304 (NOCS cruise report number 16) and FS Poseidon cruises P343 and P345 (NOCS cruise report number 28) and in 2007 on RRS Discovery cruise D324 (NOCS cruise report number 34). Cruise D334 started and finished in Tenerife, Spain and covered the Eastern Boundary and Mid-Atlantic Ridge moorings deployed on D324 and P343. This cruise was the fourth annual refurbishment of the Eastern Boundary and Mid-Atlantic Ridge sections of the mooring array. The array will be further refined and refurbished during subsequent years. The instruments deployed consist of a variety of current meters, bottom pressure recorders, CTD loggers and Inverted Echosounders, which, combined with time series measurements of the Florida Straits current and wind stress estimates, will be used to determine the strength and structure of the MOC at 26.5°N.

The three key objectives of our original proposal were to test: 1. The hypothesis that mantle upwelling and melting is focused at the centres of slow spreading ridge segments and transposed by sub-horizontal flow away from there. 2. The hypothesis that plate accretion and separation mechanisms are fundamentally different in 'magma-starved' areas. 3. Mechanisms of detachment faulting and extensional strain localisation in the lower crust and upper mantle. We proposed to achieve these objectives by detailed surveying and sampling across an extensive region of magma-poor seafloor spreading around Fifteen Twenty Fracture Zone (FTFZ), coupled with microstructural, geochemical and palaeomagnetic analyses. TOBI deep-towed sidescan and magnetic data were to be obtained both to inform the choice of sampling sites and to aid in structural, lithological and geodynamic interpretations. We spent 29 days on the Mid-Atlantic Ridge (MAR) in the vicinity of 13 to 15N. We collected multibeam ship-based bathymetry, gravity and magnetic data and TOBI sidescan, magnetic and water-column data from a total area of about 8,000 km2. We recovered samples from 47 drill and dredge stations throughout the area, in support of the objectives.

The purpose of the cruise was the refurbishment of an array of moorings on the mid-Atlantic Ridge and off the Moroccan Coast at nominal latitude of 26.5°N. The moorings are part of an Atlantic-wide mooring array for monitoring the Atlantic Meridional Overturning Circulation and Heat Flux. The array is a joint UK/US programme and is known as the RAPID-WATCH/MOCHA array. The RAPID transatlantic array consists of 24 moorings of which 21 are maintained by the UK, and 20 bottom landers of which 16 are maintained by the UK. The moorings are primarily instrumented with self logging instruments measuring conductivity, temperature and pressure. Direct measurements of currents are made in the shallow and deep western boundary currents. The bottom landers are instrumented with bottom pressure recorders (also known as tide gauges), measuring the weight of water above the instrument. A sediment trap mooring NOGST was also recovered and redeployed for the Ocean Biogeochemistry and Ecosystems Group at the NOCS. CTD stations were conducted at convenient times throughout the cruise for purposes of providing pre and post deployment calibrations for mooring instrumentation and for testing mooring releases prior to deployment. Shipboard underway measurements were systematically logged, processed and calibrated, including: waves (spectra of energy and significant wave height), surface meteorology (air pressure, temperature, wind speed and direction and radiation (total incident and photosynthetically active), 6m depth sea temperatures and salinities, water depth, navigation (differential GPS measurements feeding two independent and different receivers, heading, pitch and roll from a four antenna Ashtec ADU5 receiver, gyro heading and ships speed relative to the water using an electromagnetic log). Water velocity profiles from 15m to approximately 500m depth were obtained using a ship mounted 75 kHz acoustic Doppler current profiler. Seawater samples from CTD stations and of the sea-surface were obtained for calibration and analysed on a salinometer referencing these samples against standard sea water. For velocity data (wind and currents) measured relative to the ship considerable effort was made to obtain the best possible earth-referenced velocities. Four APEX Argo floats supplied by the Met Office were deployed at pre-assigned locations, filling gaps in the network.

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.