Equipment

Home Offshore- Terramare Estuarine Habitat Mapping Index

CLICK ON ALL PLOTS TO EXPAND!

Equipment

ADCP

The Acoustic Doppler Current Profiler, does what it says, it measures currents with sound using the doppler effect. It was widely used to measure the rate and direction at which water moves across a section of the water column, as well as enabling us to look at the shape and depth of the seabed. It was used on both the RV ‘Callista’ and RV ‘Bill Conway’ vessels for offshore and estuarine expeditions.

BONGO NET

The Bongo Net system is a device used to collect samples of zooplankton. In the case of the offshore sampling, two nets with varying mesh sizes were deployed over the side of the vessel and towed at set depths at slow speeds for a given period.

Based on the diameter of the net opening and distance towed, the volume of water passed through can be calculated. Removable collection buckets make for easy storage and transfer of samples.

NISKIN BOTTLE

This is a relatively simple device that captures water samples at discrete depths. It enters the water open and is closed using a weighted ‘messenger’ when at the required depth. It was most often operated by hand, but may also have been attached to a rosette (see below). This was used on the MTS ‘Terramare’, RV ‘Callista’, RV ‘Bill Conway’ and Winnie-the-Pooh vessels for offshore and estuarine sampling. On the pontoon, a horizontal version was used, it operates in the same way, but instead enters the water horizontally (rather than vertically) for ease of use.

CTD

The Conductivity, Temperature and Depth sensor is the primary tool used to characterize the vertical structure of the water column; both offshore and within the estuary. The device is attached to a computer on board the vessel via a cable which gives real-time data. In many cases it was used as a single device (i.e. within a YSI multiprobe), deployed over the side of the vessel and lowered to depth, alternatively it may have been incorporated into a rosette which helped to make decisions on where to take water samples.

ROSETTE

A rosette is typically a large circular frame containing several remotely activated Niskin bottles that enable discrete depth samples of the water column. As mentioned, they often have a CTD attached as well as other useful instruments to characterize the water column. This was used on the Conway and Callista for both the offshore and estuarine practicals.

SIDE SCAN

The side scan towfish is a sonar system used to survey the seafloor during the geophysical benthic habitat mapping exercise. To take measurements it was deployed (by hand) over the stern of the MTS Explorer vessel, and towed for a set period to analyze the seabed at a specific location – in our case the Helford River. Connected via a cable to a sytem on board the vessel it could produce a live feed of the seabed as we moved over it. With a swath of 75m it provided sufficient information to get a good idea of the seabed.

LIGHT METER

This is an instrument used to measure and record the Photosythetically Active Radiation (PAR) of the water column, helping to give an indication of the euphotic depth as well as other factors such as turbidity. It is important to compare the water column irradiance with surface irradiance. This was primarily used on the pontoon, and was operated by hand. Knowing the depth of the water column prevented the operator lowering it too far and thus creating disturbance from the seabed which would affect the readings.

YSI MULTIPROBE

This is a hand operated device that enables sensitive measurements of depth, temperature, conductivity, dissolved oxygen, and fluorescence among others. Connected via a cable to a display, real time readings may be recorded allowing quick and efficient analysis of the water column. This was mainly used on the pontoon.

CURRENT METER

A hand-held device used to measure speed and direction of current flow by mechanical means. This was used on the pontoon to give an indication of the tidal state.

U-1500 SPECTROMETER

In the dry lab, a spectrophotometer was used to measure the absorption of a water sample, indicating the concentration of a chemical constitute, for example silicon. A calibration curve is required to convert absorption values to concentration, this was done on Microsoft excel. Samples from offshore and the estuary were measured using this determine silicon,

665 DOSIMAT

This is a manually operated ‘dose controller’ allowing precise analysis of chemical concentrations. In the dry lab, it was used for the titration of sodium thiosulphate to calculate oxygen concentration of the water samples from offshore and the estuary. It was used in conjunction with an End Point Detector.

10-AU LABORATORY FLOUROMETER

This is a highly sensitive device used to measure the chlorophyll concentration of a water sample. Again, this was used to analyze the water samples from both offshore and within the estuary.

VIDEO CAMERA

A high-resolution video camera was used to get a visual of the seabed and to get a better look at the Maerl beds we were studying. It was towed just above the seabed with the camera either angled outwards or straight down depending on what we were trying to look at. Since it provided live feedback, we were able to watch the footage on board the vessel and make observations as we went along.

Below is a list of the equipment used to collect the data: