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Home About Us  Habitat Mapping Pontoon Estuary Offshore

Abstract:
Offshore surveying was conducted to study the effects of physical water column properties on the chemical and biological distribution of shelf seas over temporal and spatial scales. Strong stratification was present offshore with some increases in mixing towards land. Observed changes in physical properties across spatial and temporal scales correlated with changes in nutrient and biological distribution.

Introduction:

To determine the physical parameters offshore and how they impact the chemistry and biology, while comparing this with the overall structure in the Fal estuary. Five stations were sampled using CTD casts and ADCP transects, along with zooplankton trawls and water samples, starting with the furthest station from the coast and sampling on the way back. The data from this survey should allow the group to compare and contrast the marine and estuarine environment. Coastal shelf waters, such as the offshore waters off Falmouth, display seasonal increases in stratification due to increased water surface heating during summer months. As stratification increases towards the coast, there is increased interaction with tidal movements.

Methodology:

CTD Deployment Methodology:

The Niskin bottles placed on the CTD rosette were firstly checked to be ready to fire and the switch CTD was switched to on. To begin to deploy the CTD the dry-lab team and winch operator had to be on stand-by, stabilising the CTD using ropes. The CTD was halted at the surface to allow time for the dry lab team to get into place. Information was relayed from the dry-lab team to the winch operator, taking Niskin bottle samples at depths of interest. Once the CTD was retrieved the Niskin bottle water was passed to the wet-lab team and the CTD was subsequently switched off.

Niskin Bottle Rossette:

Water samples were collected using Niskin bottles mounted on the CTD rosette and deployed off the Callista. Each Niskin bottle was fired at a specific depth that was chosen after CTD was run on a downward profile. These samples were processed in different ways in the wet lab depending on the parameter of interest. The station number and Niskin bottle number was recorded and the different processed samples were also numbered and recorded.

MiniBAT Deployment:

The MiniBAT has a total of 120m of cable that is attached to the capstan before deployment and detached after retrieval. The MiniBAT is left to run for a period of time over a predetermined distance and has the orientation within the water column controlled in the dry lab. Whilst being towed the MiniBAT oscillated up and down through the water column at a pre-set 5- 45m by wing angle change.

OFFSHORE SURVEY:

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