Mark symons

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  • Potential Ballast Water Movement

    within the Fal Estuary


    Mr Mark Symons, (Student) Falmouth Marine School (University of

    Plymouth) Fdsc Marine Science, Falmouth, Cornwall, United

    Kingdom. 58 Manor Way, Helston, Cornwall, TR13 8LJ

    Miss Louise Hockley, (Associate Lecturer) Falmouth Marine School,

    Falmouth, Cornwall, United Kingdom. MSc Marine Science.


    The Fal Estuary a SAC under the E,Us Habitats Directive but home to

    a working docks, and invasive species. Its Hydrodynamic traits are

    mainly unknown. Measurements of tidal flow in the dockland area

    of the Fal are undertaken over an entire tidal cycle of

  • February/March. This data plotted in vector graphs shows that the

    mean movement of water is towards the docklands, and that

    statistically there was no significant difference in direction between a

    flooding and ebbing tide. Along with this the velocities were so slow

    that the maximum any NIS would travel before the tidal current

    reversed is 425.52m, thus negating the need to develop any

    management strategies.


    Transportation of Non Indigenous Species (NIS) through the use of

    ballast water in shipping is a well known problem and has been since

    the technology was fully established in the 1950s (Griffiths et al;

    2009) (other transportation vectors do also exist such as hull fouling).

    Though the use of ballast water has a negative effect on the

    environment by introducing NIS, it plays a major role in keeping

    vessels stable and improving manoeuvrability when free from cargo

  • (Packard, 1984; Tsolaki, 2009; Zhang and Dickman, 1999). Tsolaki

    (2009) states that Shipping moves 80% of the worlds commodities

    and transfers approximately 3-5 billion tonnes of ballast water

    internationally. This vast movement of ballast water has lead to the

    introduction of over 1000 NIS in European coastal waters (Golasch,

    2006); though it was the harmful affect to human health and the

    economy that attracted the attention of scientists and professionals

    to address the issue (Institute for European environmental policy


    In 2004 the International Maritime Organisation organised a

    convention for the management of ballast water and sediment in

    ships. The convention came up with two strategies to combat the


    1) They must have and implement a ballast water management

    plan approved by the administration.

    2) To have aboard a ballast water record book, recording when

    ballast water is taken on board and when it is discharged, also

  • any accidental or exceptional discharges must be recorded

    (International Maritime Organisation, 2004).

    The two most important regulations are D-1, Ballast water exchange

    Ref (Matej, 2008), and D-2 which is a ballast water performance

    standard which dictates the acceptable levels of organism allowed

    within ballast water. A D-2 table of organisms sizes and quantities

    can be found in Tsolakis (2009) review of ballast water treatment.

    Regulation D-1 is being phased out and after 2016 only ballast water

    treatment systems will be utilised to comply with regulation D-2

    (International Maritime Organisation, 2004). Therefore the ballast

    water related industry is focused mainly on treatment of ballast

    water, this maybe port based or ship based. Even with treatment

    systems in place there is not a method which can remove 100% of

    NIS (Tsolaki, 2009). The treatment systems do have their place and

    should continue to evolve, however there maybe alternative

    methods to manage NIS.

  • This study is to investigate whether simple current modelling can

    help to manage NIS within the Fal estuary, Falmouth, Cornwall.

    When planktonic NIS is deposited with ballast water in the Fal it is at

    the mercy of abiotic factors; Transportation will be controlled by the

    estuaries hydrodynamic traits (Becker et al., 2010). The region of the

    Fal estuary where the docks are located is macrotidal (Pirrie et al.,

    2003) with the largest spring tides of 5.7m. The Fal possess a flood

    dominant tidal flow, but low tidal currents (Stapleton and Pethick

    1996) this means that settlement of sediment in lower half of the

    estuary has been minimal which could have similar implications for

    NIS. However geochemical data showing the distribution of

    contaminates within the Fal suggests that it follows the dominant

    tidal flow (Carrick Roads area) (Pirrie et al., 2003), this could also

    have similar implications for NIS.

  • Apart from the work by Stapleton and Pethic, I am only aware of one

    physical study of the Fal performed by Matthew Le Maitre who

    undertook a hydrographical survey for the Harbour Commission. The

    survey was looking at the accuracy of tidal diamonds on admiralty

    charts in comparison with real time data collected from in-situ

    buoys. The current flow data was only undertaken for surface layers

    and modelled in a programme known as PICES for mapping oil spill


    The Fal estuary is a special area of conservation under European

    Habitats Directive, which aims to protect the site and stop any

    Figure 1. Map showing dominant tidal flow in the Fal. Map A- 3 hours before high water.

    Map B 3 hours after high water. Courtesy of Stapleton and Pethic Institute of Estuarine

    and Coastal Studies.

  • degradation and obtain favourable conservation status of the

    interest features across their bio- geographical ranges (Langston et al

    2006) NIS would conflict with this. The Fal estuary is also a ria

    making it one of the deepest natural harbours in the world. This

    allows there to be a commercial docks run by A&P Ltd, again

    conflicting with the special area of conservation principals. Although

    export is low from Falmouth docks ,it still exists. Therefore ballast

    water will be released into the estuary; the majority of ballast water

    released in the docks is from vessels entering dry docks for repair

    (Mike Pereir, A & P Ltd, Pers. Comm., January 14, 2011).

    Species that have been recorded in the Fal are:

    Crepidula fornicate,

    Caprella mutica,

    Styelea cava,

    Crassostrea gigas,

    Sargassum muticum,

  • Watersipora subtorquata,

    There is also no management in place by Cornwall council to deal

    with invasive species. (Jenny Christie, Maritime Environment officer,

    Cornwall Council. Pers. Comm., November 25th 2010). However both

    the Environment Agency and Natural England would be responsible

    should an outbreak occur that could be contained or eradicated

    (Lisa Rennocks, Cornwall Wildlife Trust, Pers. Comm., May 04 2011)

    There is a hotline for reporting NIS and each cased is judged on

    whether action is needed.

    Sampling area

    The sampling area is shown in fig 2, the site was not the preferred

    location but had to be used to coincide with the working

    functionality of the docks. This site is however a good representation

    for ballast water transport, as Duchy Wharf is one of the primary

    wharfs used by A&P Ltd, thus NIS could potentially be released into

    the recorded currents.

  • The Hydrodynamic traits of this area are unknown, being affected by

    natural fluxes and anthropogenic structures. These structures may

    be permanent such as the wharfs, or mobile structures such as the

    access barge and other vessels using the docks.

    Wharf Destroyed in

    Fire 2003.

    Figure 2. This GiS Map shows the location of the sampling site, note anthropogenic structures that may

    influence hydrodynamic traits. (a) Location was an access barge used for smaller vessels; this was constantly



  • Methodology

    The sampling was conducted using a Valeport 106 Current Meter. It

    was used in self recording mode with the 10-way subconn connector.

    Direct operation was not possible due to location. The current meter

    was then lowered through the water column stopping at each 1m

    interval for a period of two minutes allowing data collection. This

    would be done each day over one entire tidal cycle, alternating daily

    between flooding and ebbing tides. During spring and neap tides,

    both the flooding and ebbing tide would be measured to give a tidal

    flow for the extremes of the cycle.

    As the 106 current-meter was used in self recording mode, the data

    needed to be removed after each daily sample obtained. This is

    done using Datalog (software provided by Valeport) and the Y lead to

    connect the fish to the computer. Once the data had been removed

    it is to be converted into an excel format and filtered (shading

    alternative depths for clarity). Each depths flow and heading data

    would be copied into a new spreadsheet (Flooding, Ebbing, Spring

  • Flood, Spring Ebbing, Neap Flooding or Neap Ebbing): Sheets are

    then separated into individual depths. Vectors would then be

    converted into Cartesian coordinates and then averaged.

    X= cos

    Y= sin

    ( = )

    ( = )

    Once the data is averaged it is changed back to vector (polar)

    coordinates using Atan2: