The 83 m Canadian Coast Guard icebreaker,
the NGCC Martha L. Black
Most of the sampling done by IML scientists within the Atlantic Zone Monitoring Program occurs on Canadian Coast Guard ships like the one in this photograph. The NGCC Martha L. Black, a light icebreaker—Type 1100, is shown here fitted out for scientific sampling, with the portable container laboratories attached to the forward deck.
Sea-Bird 911plus CTD
- conductivity sensor (SBE 4)
- temperature sensor (SBE 3plus)
- pressure sensor (Paroscientific Digiquartz)
- fluorometer (WET Labs WETStar)
- dissolved oxygen sensor (SBE 43)
- submersible light sensor (Biospherical Instruments QSP-2200)
- submersible pump (SBE 5T)
A rosette system (see figure) is used to sample key variables. The main component of this instrument is the Sea-Bird 911plus CTD profiling instrument, which is used to measure the Conductivity and Temperature of the water as a function of the Depth, hence the acronym CTD
The rosette sampling system
Other sensors can be added to the CTD to measure, for example, the fluorescence due to the presence of chlorophyll, the dissolved oxygen, or the quantity of light. The sampling bottles (called Niskin bottles) attached around the perimeter of the instrument allow water to be collected at specific depths. This water will be used for various laboratory analyses. The instrument is lowered from the surface to within a few metres of the bottom at a speed of about 1 metre per second. During the descent, a shipboard computer records the signals coming from the different sensors and traces a profile in real-time on the computer screen. The instrument is stopped on the way up, and bottles are remotely triggered to close at depths of 300, 200, 100, 50, 25, 15, and 5 metres as well as the surface.
- water salinity (Guildline Autosal salinometer);
- phytoplankton biomass estimated by fluorometric measurements of chlorophyll quantity (Turner Designs TD-700 fluorometer);
- nutrient concentrations (NO2, NO3, PO4, SIO2) (Technicon AutoAnalyzer or Alpkem Flow Solution);
- dissolved oxygen determination by automated Winkler titrations (Dosimat and Brinkman colorimeter);
- Microscopic examination for the identification and counts of phytoplankton species.
A plankton net is deployed at each station, making a vertical tow from the bottom to the surface. This net collects the small animals known as zooplankton.
A TSK electronic flow-meter and a pressure sensor are attached to the net, giving real-time information about the depth and the volume of water filtered as the net is towed upwards. The samples collected with the plankton net will be used:
- To determine the zooplankton biomass (dry weight);
- To identify, count, and determine the specific composition of the zooplankton community.