Details of Award
NERC Reference : NE/C51484X/1
Derivation of plankton net community production from situ oxygen/argon ratios.
Grant Award
- Principal Investigator:
- Professor C Robinson, Plymouth Marine Laboratory, Plymouth Marine Lab
- Grant held at:
- Plymouth Marine Laboratory, Plymouth Marine Lab
- Science Area:
- Marine
- Overall Classification:
- Marine
- ENRIs:
- Global Change
- Science Topics:
- Biogeochemical Cycles
- Ocean - Atmosphere Interact.
- Abstract:
- The increasing concentration of carbon dioxide (CO2) in the earth's atmosphere is causing significant changes in global temperature and climate. Atmospheric CO2 concentrations are influenced by the uptake and production of CO2 by plants and animals during photosynthesis and respiration. The tiny plants and animals which live in the sunlit upper ocean (plankton) play a major role in this biological cycling of CO2 and so an understanding of how their rates of photosynthesis (P) and respiration (R) vary in space and time is imperative. Despite its huge importance, the balance between plankton P and R is still poorly known. Analytical methods of measuring oxygen (O2) dissolved in seawater are about 10 times more sensitive than methods to measure dissolved CO2, and so marine scientists use O2 change as a surrogate for CO2 change because physiologically they change on an almost 1 to -1 basis during P and R. The most commonly used method of measuring the P/R ratio of plankton at sea is to incubate a series of replicate water samples in 100 ml glass bottles in the light and darkness of a 24 hour day. The change in dissolved O2 during the light+dark incubation is P-R and the decrease in dissolved O2 during the dark period is R. However, measurements of the P/R ratio derived from this method are ambiguous - differing in both the sign of the balance as well as the magnitude - for large areas of the open ocean. A second approach of estimating P/R uses chemical signatures of biological activity over seasonal to annual time periods or mathematical models of the seawater supply of nutrients which could support P and R. These methods conclude that the same open ocean areas have a balanced P=R or P>R. If some of the bottle incubation data are correct in their suggestion that R is greater than P over large ocean areas for long time periods then our view of how the biological carbon cycle works would need to be revised. This active debate is hindered by the limited amount of open ocean P and R data which is available, and it is possible that the samples collected for bottle incubations have missed infrequent short lived high levels of plankton photosynthesis. This research will use a new approach to estimate the ocean P:R balance over time periods of weeks-months and space scales of km which avoids the potential sampling problems of the bottle incubation technique. The approach relies on continually measuring the ratio of dissolved oxygen and argon in surface seawater pumped onboard a research ship. While the concentration of dissolved O2 changes due to plankton P and R, temperature and water movement, argon concentrations do not change due to P and R. Comparing the ratio of these two gases and estimating the amount of gas which has been absorbed or degassed from the ocean to the atmosphere related to wind speed allows one to calculate the magnitude and sign of O2 change equivalent to P-R. Absolute rates of P and R can be calculated from measurements of the isotopic composition of dissolved O2 because P and R change the O2 isotopic signature (the ratio of 16 O, 17 O and 18 O) in a predictable manner away from the isotopic signature of atmospheric O2. The instruments (mass spectrometers) required to make these measurements have only recently been developed by the world renowned American scientists involved in this proposal. This will be the first time these measurements have been made in the Atlantic Ocean and the first time that a direct comparison of P/R estimates from this approach and from bottle incubations have been made anywhere in the world. The British scientist involved in this proposal is an expert in the bottle incubation technique and leads a marine research programme which studies the influence of marine plankton composition and activity on climate. This programme samples a huge area of the Atlantic Ocean between the UK and South Africa twice a year making a wide range of biological and chemical measurements which will help ...etc
- NERC Reference:
- NE/C51484X/1
- Grant Stage:
- Completed
- Scheme:
- Small Grants Pre FEC
- Grant Status:
- Closed
- Programme:
- Small Grants
This grant award has a total value of £22,890
FDAB - Financial Details (Award breakdown by headings)
| Total - Staff | Total - T&S | Total - Other Costs | Total - Indirect Costs |
|---|---|---|---|
| £2,439 | £5,440 | £13,889 | £1,121 |
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