RRS Discovery DY172
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | RRS Discovery (74EQ) |
| Cruise identifier | DY172 |
| Cruise period | 2023-12-21 — 2024-01-26 |
| Status | Completed |
| Port of departure | Cape Town, South Africa |
| Port of return | Walvis Bay, Namibia |
| Purpose | Research |
| Objectives | Our overarching objective of DY172 is to combine state-of-the-art measurements of photosynthetic physiology and primary production across natural oceanic gradients with experimentally imposed manipulation of the nutrient and temperature environment to collect datasets that will enable us to define how photosynthesis works across oceanic regions that encapsulate most of the world's oceans.
We used a North-South latitudinal survey from the South Atlantic into the Southern Ocean and back. This was selected to encompass gradients in environmental drivers that limit primary production (nitrogen, iron, temperature, light). The carefully selected region sampled across this single research cruise will encompass ecosystems and phytoplankton community and physiological diversity which is representative of the world's surface ocean. Objective 1: Collect in situ measurements of photosynthesis physiology and rates of primary productivity (alongside complementary measurements of the physics, chemistry and microbiology of the system) over natural gradients from: (i) Oligotrophic waters of the South Atlantic Subtropical Gyre (SASG), a nitrate-limited system (nitrate typically <5 micrometres) dominated by prokaryotes (Prochlorococcus and Synechococcus) (above 40 S). (ii) The iron-limited Southern Ocean (below 50 S), which is dominated by eukaryotes (diatoms) Objective 2: Collect water from (i) and (ii) regions to enable on deck manipulation experiments that test the impact of nutrient addition on the photosynthetic physiology and rates of primary production. Objective 3. To deploy 5 gliders for the Met Office in under sampled oceanographic regions Objective 4. To recover a mooring deployed by NIOZ in Jan 2023 DY172 has been successful in meeting these objectives. Despite losing some time to weather during the transit to 58 S and on the return, all ships and scientific systems worked well enabling extensive sampling of the prime target regions (low Fe and low N). A total of 31 stations were occupied at which both stainless steel (SS_CTD) and trace-metal-clean (TMC) (titanium) (Ti_CTD) CTDs were deployed for water sample collection; nominal CTD depths were to 1000 m and complemented by targeted Ti_CTDs to full depth to help resolve the sources of nutrients to the surface ocean. Twelve (48-hr) manipulation experiments and 13 (96-hr) manipulation experiments were conducted across the entire study region. These were complemented by underway sampling (every 4 hrs) using the ships system, a TMC (Tow-Fish) deployed from the starboard stern quarter and the use of a suite of continuous (real time) optical measurements of the physiology of photosynthesis communities. Four stations were occupied for 24 hrs to enable sampling of the same location over diel cycles. Combining these approaches have enabled a study of photosynthesis spatially, temporally and in response to nutrient manipulation. In addition, the use of SST, Chlorophyll and sea-surface height from satellite data enabled sampling to be targeted to dynamic frontal regions and regions of high chlorophyll concentration, and to study phenomena such as Agulhas Rings. |
| Chief scientist | Thomas S Bibby (University of Southampton School of Ocean and Earth Science) |
| Project | New Perspectives on Ocean Photosynthesis (nPOP) |
| Coordinating body | Natural Environment Research Council (NERC) |
| Cruise report |  (5.18 MB) |
| Ocean/sea areas | |
| General | South Atlantic Ocean Southern Ocean |
| Track charts | (0.11 MB) |
| Measurements | |
| Physical oceanography | |
| Surface measurements underway (T,S) | Quantity: activity duration in days = 36 Description: Temperature, salinity and fluorescence from underway sensors |
| Surface measurements underway (T,S) | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from titanium CTD (casts x30) |
| Surface measurements underway (T,S) | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from stainless steel CTD (casts x30) |
| Water bottle stations | Quantity: number of stations = 30 Description: Microbial community gene expression and diversity: stainless steel CTD |
| Water bottle stations | Quantity: number of stations = 30 Description: Extracted Chlorophyll a: Stainless Steel CTD |
| Water bottle stations | Quantity: number of stations = 30 Description: Dissolved micronutrients: Titanium CTD |
| Water bottle stations | Quantity: number of experiments = 13 Description: Microbial community gene expression and diversity: Experiments |
| Water bottle stations | Quantity: activity duration in days = 36 Description: Microbial community gene expression and diversity: FISH |
| Water bottle stations | Quantity: number of stations = 30 Description: Primary production rate s and physiology: Stainless steel CTD |
| Water bottle stations | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Stainless Steel CTD |
| Water bottle stations | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Titanium CTD |
| CTD stations | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from stainless steel CTD (casts x30) |
| CTD stations | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from titanium CTD (casts x30) |
| Transparency (eg transmissometer) | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from titanium CTD (casts x30) |
| Transparency (eg transmissometer) | Quantity: activity duration in days = 36 Description: Temperature, salinity and fluorescence from underway sensors |
| Transparency (eg transmissometer) | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from stainless steel CTD (casts x30) |
| Optics (eg underwater light levels) | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from stainless steel CTD (casts x30) |
| Optics (eg underwater light levels) | Quantity: number of profiles = 30 Description: Temperature, salinity, fluorescence, oxygen, PAR, transmission, turbidity from titanium CTD (casts x30) |
| Current profiler (eg ADCP) | Quantity: activity duration in days = 36 Description: ADCP, Ships systems |
| Currents measured from ship drift | Quantity: activity duration in days = 36 Description: Temperature, salinity and fluorescence from underway sensors |
| Chemical oceanography | |
| Phosphate | Quantity: number of experiments = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Experiments |
| Phosphate | Quantity: activity duration in days = 36 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Underway, every 4 hours. |
| Phosphate | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Stainless Steel CTD |
| Phosphate | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Titanium CTD |
| Total - P | Quantity: activity duration in days = 36 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Underway, every 4 hours. |
| Total - P | Quantity: number of experiments = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Experiments |
| Total - P | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Titanium CTD |
| Total - P | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Stainless Steel CTD |
| Nitrate | Quantity: activity duration in days = 36 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Underway, every 4 hours. |
| Nitrate | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Stainless Steel CTD |
| Nitrate | Quantity: number of experiments = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Experiments |
| Nitrate | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Titanium CTD |
| Nitrite | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Stainless Steel CTD |
| Nitrite | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Titanium CTD |
| Nitrite | Quantity: activity duration in days = 36 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Underway, every 4 hours. |
| Nitrite | Quantity: number of experiments = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Experiments |
| Ammonia | Quantity: activity duration in days = 36 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Underway, every 4 hours. |
| Ammonia | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Stainless Steel CTD |
| Ammonia | Quantity: number of experiments = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Experiments |
| Ammonia | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Titanium CTD |
| Silicate | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Titanium CTD |
| Silicate | Quantity: number of experiments = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Experiments |
| Silicate | Quantity: number of stations = 30 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Stainless Steel CTD |
| Silicate | Quantity: activity duration in days = 36 Description: Inorganic nutrients (nitrate + nitrite, nitrite, phosphate, silicate: Underway, every 4 hours. |
| Trace elements | Quantity: activity duration in days = 36 Description: Dissolved miconutreints: FISH |
| Trace elements | Quantity: number of stations = 30 Description: Dissolved micronutrients: Titanium CTD |
| Biology and fisheries | |
| Primary productivity | Quantity: number of stations = 30 Description: Primary production rate s and physiology: Stainless steel CTD |
| Primary productivity | Quantity: number of experiments = 30 Description: Primary production rates and physiology: Experiments |
| Phytoplankton pigs (eg chlorophyll, fluorescence) | Quantity: number of stations = 30 Description: Extracted Chlorophyll a: Stainless Steel CTD |
| Phytoplankton pigs (eg chlorophyll, fluorescence) | Quantity: activity duration in days = 36 Description: Extracted Chlorophyll a: Uncerway shps systems |
| Phytoplankton pigs (eg chlorophyll, fluorescence) | Quantity: number of experiments = 30 Description: Extracted Chlorophyll a: Experiments |
| Biochemical measurements (eg lipids, amino acids) | Quantity: number of stations = 30 Description: Microbial community gene expression and diversity: stainless steel CTD |
| Biochemical measurements (eg lipids, amino acids) | Quantity: number of experiments = 13 Description: Microbial community gene expression and diversity: Experiments |
| Biochemical measurements (eg lipids, amino acids) | Quantity: activity duration in days = 36 Description: Microbial community gene expression and diversity: FISH |
| Phytoplankton | Quantity: number of experiments = 13 Description: Microbial community gene expression and diversity: Experiments |
| Phytoplankton | Quantity: activity duration in days = 36 Description: Microbial community gene expression and diversity: FISH |
| Phytoplankton | Quantity: number of experiments = 30 Description: Primary production rates and physiology: Experiments |
| Phytoplankton | Quantity: number of stations = 30 Description: Primary production rate s and physiology: Stainless steel CTD |
| Phytoplankton | Quantity: activity duration in days = 36 Description: Extracted Chlorophyll a: Uncerway shps systems |
| Phytoplankton | Quantity: number of stations = 30 Description: Extracted Chlorophyll a: Stainless Steel CTD |
| Phytoplankton | Quantity: number of experiments = 30 Description: Extracted Chlorophyll a: Experiments |
| Phytoplankton | Quantity: number of stations = 30 Description: Microbial community gene expression and diversity: stainless steel CTD |
| Pelagic bacteria/micro-organisms | Quantity: activity duration in days = 36 Description: Microbial community gene expression and diversity: FISH |
| Pelagic bacteria/micro-organisms | Quantity: number of stations = 30 Description: Microbial community gene expression and diversity: stainless steel CTD |
| Pelagic bacteria/micro-organisms | Quantity: number of experiments = 13 Description: Microbial community gene expression and diversity: Experiments |
| Meteorology | |
| Incident radiation | Quantity: activity duration in days = 36 Description: Temperature, salinity and fluorescence from underway sensors |
| Moorings, landers, buoys | |
| Physical oceanography | |
| Subsurface temperature measurements | 30° 8' 59" S 9° 31' 33" E — Mooring recovery, Recovered for NIOZ |
| Neutrally buoyant floats | 46° 23' 13" S 5° 44' 34" E — Argo Float 2 (9614) Deployed for MetOffice |
| Neutrally buoyant floats | 58° 8' 9" S 0° 30' 0" W — Argo Float 4 (10060) Deployed for MetOffice |
| Neutrally buoyant floats | 58° 8' 9" S 0° 30' 0" W — Argo Float 5 (10059 ) Deployed for MetOffice |
| Neutrally buoyant floats | 43° 6' 43" S 9° 19' 8" E — Argo Float 1 (9627) Deployed for MetOffice |
| Neutrally buoyant floats | 50° 42' 7" S 0° 36' 0" E — Argo Float 3 (10061) Deployed for MetOffice |
