Annick Verween, S' Degraer, M' Vincx

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Reducing the economic impact of Mytilopsis
leucophaeata in the harbour of Antwerp

• Annick Verween, S. Degraer,
  M. Vincx

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Biofouling

• the disfunctioning of a technical installation
  because of interaction between natural biological
  processes and the activities of the installation
  (Jenner, 1998)

Cooling water conduits organisms get pumped
up ideal situation growth and
colonisation clogging
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Fouling-organisms

• Hydrozoa, Barnacles, Worms, ...
• Mussels Most harmful
• Clog heat-exchangers
• Difficult to remove once theyre settled

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2. Mussels (Dreissenidae)

• Mytilopsis leucophaeata
• Brackish Water Mussel
• alien invader in Europe
• (? Atlantic Coast N-Am)
• brackish water sp.

• Dreissena polymorpha
• Zebra Mussel
• alien invader in U.S.
• (? Caspian Sea)
• fresh water sp.

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• Mytilopsis leucophaeata

• Dreissena polymorpha

Solutions? - Chlorination - Ozonation -
UV-radiation
Solutions! - Chlorination - Ozonation -
UV-radiation
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Mytilopsis leucophaeata

• Chlorination at BASF, Antwerp
• untill now only solution against
  biofouling
• Problem Use of Cl-chemicals is/will be limited
  (VLAREM II, 4.2.4., annex 2.3.1.)
• Can we reduce the use of biocides, as such meet
  the VLAREM II criteria, and still be as effective
  against biofouling?

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3. Mytilopsis leucophaeata

• OBJECTIVES
• - Efficient use of biocides
• - Switch to biological solution

Developing control stategies Knowledge of
lifecycle
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Lifecycle of M. leucophaeata
Soft tissue
settle
Protective shell
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PhD-research

• Population dynamics
• In situ observation
• Experimental observation
• Early warning system
• Correlation environment population dynamics
• Logistic regression

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3.1. Population dynamics of M. leucophaeata3.1.1.
In situ observation
Weekly monitoring of incoming water at cooling
conduits
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Strong seasonal patterns
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Compare environment larval presence
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• Strong seasonal patterns

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Compare 2001 - 2003
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Summary

• Population dynamics of M. leucophaeata quite
  similar yearly,
• BUT small variations determine size of
  fouling-problems

Larvae arrive end May - early June, until Sept -
Oct Settlers arrive in august, until december or
longer Densities and spread may differ
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3.1. Population dynamics of M. leucophaeata3.1.2.
Experimental observation

• effect of changes in environmental factors on
• Adults ? detailed information about relation
  environment population, explanations
• Larvae ? search for max. mortality under min.
  changes in current environment
• ? can a combination of environmental factors
  avoid boifouling?

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• Adults Scope for Growth
• Protocol Widdows Staff, 1985
• energy balance between E-gain E-loss of
  bivalves
• direct measure of potential growth under
  specific conditions

• Larvae hatching testing
• Protocol Honkoop, 1998
• way to hatch Macoma balthica in the lab
• closest to M. leucophaeata

A protocol alone is not enough! Working with
living animals, keeping them alive testing with
them is DIFFICULT! Time- energyconsuming to
find most ideal protocol for each
experiment Dont underestimate this!
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3.2. Early warning system STATISTICS

• warning when the larvae will arrive in the
  system
• new biofouling gets avoided
• Based on - presence/absence of larvae (0/1)
• - predicting environmental variabels
• 3.2.1. Correlation environment population
  dynamics
• What are the predicting variabels for larval
  arrival?
• - literature timing duration of reproduction
  cycle is believed to be controlled by
  environmental factors
• - temperature, salinity, foodavailability

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• Is there a correlation?

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3.2. Early warning system STATISTICS

• 3.2.2. Logistic regression
• to predict the probability of appearance of
  larvae as a response on changes in environmental
  variables (Ysebaert et al., 2002)
• statistical model, relates the proportions pi
  of a dependent variabele to an undependent
  variabele X (Cox, 1970 Hosmer Lemeshow, 1989
  Trexler Travis, 1993 Jongman et al., 1995)
• p(x) e(a bX) / 1 e(a bX)

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4. Conclusions and further research

• Monitoring
• Larvae arrive in june, until september-october
• Settlers arrive in august, until december or
  longer
• Effect of environmental factors

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• Early warning system
• Experimental research
• larvae search for max. mortality under min.
  changes in current environment

Efficient use of biocides ? PROACTIVE
Switch to a more biological solution