Operations
Continuous Plankton Recorder Sampling
Operations
Since the first Continuous Plankton Recorder was towed by the SS
Albatross between Hull, NE England and Bremen, Germany on the
15/16th September 1931, more than 275 vessels have helped in a
voluntary capacity to maintain the survey. The Foundation is
greatly indebted to the Captains and Crews of all the tow ships,
their ship owners, management companies, charterers, port staff,
stevedores and agents. Their support is gratefully acknowledged, as
without it, this valuable plankton research could not be
economically performed. Details of the shipping companies and
photographs of the participating vessels are on the following web
page: photos of ships and details of shipping companies.
Operations: News
With the co-operation of these shipping companies, the Survey
completed a further successful year during 2005. 385 tows were
completed which comprised 132393 nautical miles logged. The total
distance that the plankton samples covered was 112922 nautical
miles. The tow success rate was 85.5%. There were three ship
changes in 2005. In April, the MSC Iris started the SM route. In
June, the Flottbeck took over the D and W routes and in October,
the Tor Dania took over the HE route. New CPR (number 177) with
filter cassette was purchased from Camtec Engineering Ltd of
Plymouth, during June 2005. CPR 177 has been towed from the
Brittany Ferries ship Bretagne between Plymouth and Roscoff,
France. It will be towed on the 450NM LG route from May 2006. This
the first new CPR to be bought by SAHFOS since 1983.
CPR sampling in the North Pacific, 2005
The USA registered containership, Horizon Kodiak resumed the AT
route from Tacoma (Washington State, USA) to Anchorage, Alaska,
from March to September 2005. The CPR was loaded at SAHFOS,
Plymouth and freighted to Tacoma, placed on the ship and then towed
to Anchorage. The three filter cassettes were sent from Anchorage
to Professor Bob Benda at Prince William Sound Community College,
Valdez. The filter mesh was unloaded and sent to Mr Doug Moore at
the Institute of Ocean Science at Sidney, Vancouver Island. During
July 2005, mechanical problems meant that a replacement gearbox and
spares had to be flown out to Tacoma. The Horizon Kodiak's crew
fitted these and tows were resumed. The samples were cut for
analysis in Vancouver and 20% of them were analysed there, with the
balance being sent back to SAHFOS. The 90.6% success rate is a
tribute to Professor Benda's work.
Also in the Pacific, the Seaboard Shipping Roll on Roll off (Ro
Ro) Skaubryn resumed the VJ route from Vancouver Island to
Hokkaido, Japan. Tows were carried out in April, June and
September, 2005. The CPRs with seven filter cassettes were serviced
at Crofton, Vancouver Island by Dr Sonia Batten and her team. 21
500NM tows were completed with a 91.6% success rate, which is a
tribute to the local team. The CPR was retained on Vancouver Island
and was overhauled and reloaded by SAHFOS technician, Roger
Barnard, during the CPR training week held 3-8 April for the local
Canadian team. After this successful visit and training, the VJ
route resumed on 3 May 2006.
CPR Tow logistics
Plankton recorders are maintained, repaired and loaded ready for
use at the SAHFOS workshop in Plymouth. They are transported with
their tow wires to the respective ports in large yellow painted,
plywood boxes. The tow ship's port agents and stevedores very
kindly see to the placing aboard and offloading of recorders from
the ships. This is a crucial role in the logistics. A close liaison
with them is maintained by the survey logistics manager. Each ship
has a detailed tow request for each month's route. The CPR is
launched at the ship's normal operating speed (e.g. 19 knots) over
the ship's stern by paying out the tow wire from a suitable mooring
winch drum. It is stopped when the bright yellow whipping, tow mark
on the wire is touching the sea. This will give the desired tow
depth of 6 to 10 metres. The tow wires are marked according to the
speeds of the ships.
The start, alter course and haul positions of the plankton
recorders with respective Universal Time Constant (UTC) (formerly
GMT) times are logged by the ship's navigators. Weather, cloud
cover and any other pertinent details are also logged. On
completion of the tow, the CPR is replaced into its carriage box
with the tow wire and landed at the requested port for returning to
SAHFOS at Plymouth. The tow log is returned to SAHFOS and is a
receipt for the honorary tow payment made to the ship's crew. The
tow logs are checked and processed in conjunction with the filter
mesh unloading chits. This provides the data for computing the
nautical miles per two-inch division of filter mesh. (The aim is to
get a ratio of five nautical miles per two-inch division). This is
the miles per division (MPD) ratio and is used for allocating the
10 nautical mile equivalent filter mesh blocks. These are the
standard filter mesh lengths used for plankton analysis under the
microscope. The required MPD ratio is achieved by setting the pitch
angles of the CPR impeller blades.
Organising the operation of a CPR on a new route or
ship
When a shipping route is selected for plankton sampling, a
suitable ship is sought that can tow CPRs at the required monthly
frequency. Permission to tow is obtained from the ship owner,
managers and the Master. The ship's stern is inspected for safe
towing facilities such as available space and siting of mooring
winches. A tow davit or tow point (usually an outrigger or 6.5
tonnes safe working load pad eye) is installed on the stern mooring
deck. The site of the davit pedestal base plate depends on the
strength of the deck and under-deck girders. After installation,
the davit arm is 'safe working load (SWL)' tested to 2 tonnes by
means of a static pull test to 2.5 tonnes using a calibrated load
cell. The test certificate is issued to the ship. Safe working load
test certificates are issued for all the towing equipment including
the steel blocks, shackles and eyes. The 10mm diameter tow wires
have test certificates for 1.18 tonnes SWL. The marine survey
manager maintains an updated record of all equipment issued to each
ship at SAHFOS. Each davit is inspected every six months by the
ship's crew and any defects repaired at SAHFOS cost. The davits are
safe working load tested every four years and certificates issued.
Accident insurance cover for persons handling the CPRs is provided
by the Foundation. A Quality Control system of checking all the tow
equipment and the wires is maintained by the technicians and survey
manager at SAHFOS. Wires are replaced after 12 tows, or if badly
kinked thus exposing the core and if 10% of any wire strands are
damaged. An up-to-date record of all tow equipment issued to ships
by SAHFOS is maintained by the operations manager at SAHFOS.
