Offshore

Home River Estuary Offshore Habitat Map References

Falmouth 2017 - Group 12 7TITLE

Time: 09:20 - 14:37 UTC

Date: 05/07/17

Location: 50º 05’ 66’’ N

004º 52’ 23’’ W

Weather: There was an easterly wind (10 knots) and there was a cloud cover between 0 – 1/8 tL.

Tide: Low tide was at 10:15 UTC and the flood tide was at 15:46 UTC.

Cum sociis natoque
Aliquam vel quam
Vivamus justo est
Donec sit amet

Offshore Terramare background info

A CTD was used to determine the depth of the thermocline, the thermocline is closely related to the deep chlorophyll maximum due to factors such as stratification, nutrient levels and light attenuation. Once the depth at which the deep chlorophyll maximum (DCM) was determined, using a winch on-board the MTS Terramare a Niskin bottle was lowered to this depth. The Niskin bottle was triggered at the pre-determined depth using a messenger and this collected the sample of seawater, this was also done for the surface water. This seawater was then used to run the nitrate, silicate, phosphate, dissolved oxygen, and phytoplankton analysis. The samples for the zooplankton identification was collected by using a “Bongo net” this is a pair of plankton nets, each a different mesh size, in our case 100 and 200 microns and measuring 60cm in diameter. The bongo net was deployed to the estimated deep chlorophyll maximum (32 m which was determined by the CTD data) and this was done using the crane that was on-board the MTS Terramare. A surface sample (2 m depth) was also collected this was to allow comparisons to be drawn between depths at the same station and across all of the stations. At the end of the nets there were bottles that would collect the zooplankton, these bottles had the location, station number, date and time written on them.

The aim of the work on the MTS Terramare was to look at the temporal changes that occur in physical and biological parameters in offshore waters. The physical factors that were being studied were: temperature, salinity, dissolved oxygen content, and phosphate, nitrate and silicate concentration. The biological factors that were being collected/recorded were the chlorophyll concentrations, zooplankton and phytoplankton species and the abundance of those species.

As two samples were taken at each station (one at the DCM and one at the surface) it was expected that there would be a higher concentration and diversity of both phytoplankton and zooplankton when looking at the 32 m sample compared with the surface sample. Due to sampling taking place in the summer it was also expected that the ocean would be highly stratified due to the higher temperature of the surface waters.

Using the CTD a “yo-yo” time series was recorded, this was to look at changes with the tidal cycle, this was completed at station 11.

The data collected by group 12 on the MTS Terramare was on 05/07/2017 all of the information for the exact location and times can be found below

N.B: At station 11, a trawl wasn’t carried out due to not having enough bottles for all of the stations.

During the day the weather conditions remained largely the same. There was an easterly wind (10 knots) and there was a cloud cover between 0 – 1/8 tL. The conditions were calm, but became choppier as the day went on. The tidal state during the sampling was at low tide. Low tide was at 10:15 UTC and the flood tide was at 15:46 UTC.

The MTS Terramare is an example of a vessel of opportunity, and because of this there was very little in the way of on-board oceanographic equipment.

Methodology

Results