Data set title:
PML Benthic Survey water column nutrient concentrations from 4 different benthic study sites off Plymouth, South West England, between 2008 and 2011.

Name of data file:
benthic_nutrients_2008-2011.csv

Data set creator(s) and institute(s):
E. Malcolm S. Woodward, Carolyn Harris and Karen Tait. Plymouth Marine Laboratory.

Data set period: 
2008-07-11 to 2011-05-19

Data set location:
Cawsand                 50° 19.81' N, 4° 11.50' W
L4                      50° 13.30' N, 4° 11.40' W
Rame                    50° 17.75' N, 4° 16.00' W
Jennycliff              50° 20.91' N, 4° 07.71' W

Data set abstract:
Results are reported for the analysis of water samples taken from the overlying water column of 4 different study sites occupied on a bi-monthly basis, when possible, during a 3 year Benthic Study programme off Plymouth, on the south-west coast of England, United Kingdom. The analyses are reported for Nitrate+Nitrite, Nitrite, Silicate and Phosphate concentrations. Results show variations across the year with the main influence to particularly the upper water column being the output of the River Tamar and the nutrients fed out during periods of rainfall. Water column structure is seen for each site, with the sites varying from L4 which is an offshore coastal site, Rame Head which is a essentially a mud based strata, to Cawsand Bay and Jennycliff which are both situated within Plymouth Sound and hence are shallow and are greatly influenced by the river outputs.

Sampling methodology and description of analytical techniques:
The nutrient samples were taken from the research vessel from the surface to near bottom, and were sampled every 2 months where conditions made this possible. They are sampled under as clean conditions as possible, using gloves to avoid contamination, and were frozen as soon as possible for later analysis at the laboratory in Plymouth. Triplicate samples are taken for both unfiltered water and also filtered (0.2μm Millipore Fluoropore).
The analyser is a 5-channel Bran and Luebbe segmented flow system using well tested colorimetric analytical methodologies (Woodward, E.M.S, and A.P. Rees, (2001). Nutrient distributions in an anticyclonic eddy in the North East Atlantic Ocean, with reference to nanomolar ammonium concentrations. Deep Sea Research II, 48, Nos. 4-5, 775-794), and the same as those used by the PML nutrient group in all their International Research cruises, and research programmes. Quality control procedures are carried out with regular use of KANSO certified reference materials, and also the group participates in the European Quasimeme programme as well as being a member of the International Nutrient Scale System International Intercalibration programme steering committee. 

Data quality comments:
The data has all been Quality Controlled, any obvious individual 'outliers' have been discarded and the results published are the averages of the triplicate sampling results for every depth at each station.

Data usage:
It is essential for all users of these data to establish and maintain contact with the nominated current data originators as well as fully consulting the metadata. While not impinging on free data access, this ensures that this dataset is being used in the correct way, and any potential issues with the data are clarified. As more samples are identified, a proper dialogue with these local experts on the series may enable, where appropriate the most recent dataset to be used.