aqua-tools Zestaw analityczny ATP do wód balastowych (BWTK)

Since the introduction of steel hull for the vessel construction, a system has been developed to provide better stability, maneuverability and weight balance: the ballast.

Ballast takes different forms: crew, keel made with high density material (stone, sand, iron, lead, etc.). The main problem with this kind of ballast is the mass. It significantly increases the weight of the boat, and the mass can’t be easily modified depending on the cargo. In order to gain flexibility a new kind of ballast has been setup, the water ballast.

Despite of its relatively low density, water is more and more used as ballast especially for cargoship. Water ballasts are big tanks located in the hull, it require large space but the possibility to easily modify the quantity of water inside the ballast is a massive advantage. Whatever is the cargo, you can fill the ballast or pump out the waterdepending on the cargo load and then maintain the buoyancy and the angle of heel at a perfect level.

 

 

The problem that the ballasts are filled with water from one location but are emptied maybe 20.000km from there. This discharge of non-local water can introduce nonindigenous, nuisance, invasive or exotic species that can cause ecological and economic damage to aquatic ecosystems along with serious human health problems.

Around the world the most "prominent" cases were: - Introduction of the European zebra mussel Dreissena polymorpha into the Great Lakes (USA) - Introduction of the East-American comb jelly Mnemiopsis leidyi into the Black and Azov seas - Introduction of the cholera bacterium Vibrio choleare into coastal waters of the USA - Introduction of toxic dinoflagellates into the Australian waters

Concerning the consequences of such changes in ecosystem, introduction of the nonindigenous species has direct impact on:
Human health (cholera, paralytic shellfish poisoning (PSP); human fatalities ...) Marine environment (impoverishment of biodiversity and decrease of the abundance of autochthonous marine species ...) Economy, losses counted in billions of dollars (shellfish industry, fishery ...).

For the first time problem of harmful introduction of nonindigenous species has been raised during the 1973 IMO conference. A Resolution was adopted: “ballast water taken in water which may contain bacteria of epidemic diseases, may, when discharged, cause a danger of spreading of the epidemic diseases to other countries". During twenty years scientists and experts has collected a lot of data, that have been used to negotiate with IMO member states and finally around late 90’s and early 2000’s ship ballast water has been recognized as a vector of introduction of pathogens and harmful spices by the WHO and the IMO, and a the International Convention for the Control and Management of Ships' Ballast Water and Sediments was adopted

 

- This Ballast Water Management Convention has been signed by 30 states, representing 35% of the global merchant shipping tonnage.

The convention introduces threshold value for ballast water discharge in order to limit introduction / spreading of harmful organisms. IMO gives guidelines concerning quantity of microorganisms that could be release during the discharge of ballast water, all this guidelines are described in “Annex - Section D Standards for Ballast Water Management" in the paragraph related to performance:

Regulation D-2 Ballast Water Performance Standard - Ships conducting ballast water management shall discharge less than 10 viable organisms per cubic meter greater than or equal to 50 micrometers in minimum dimension and less than 10 viable organisms per milliliter less than 50 micrometers in minimum dimension and greater than or equal to 10 micrometers in minimum dimension; and discharge of the indicator microbes shall not exceed the specified concentrations.

The indicator microbes, as a human health standard, include, but are not be limited to:

- United States Coast Guard 46 CFR 162.060 is following the same purpose, preventing the discharge of nonindigenous aquatic nuisance by ship that had operated on waters beyond the exclusive economic zone during any part of its voyage, and enter the Snell Lock at Massena, New York, or navigates north of the George Washington Bridge on the Hudson River.

Those vessels must meet the 33 CFR 151.2030 - ballast water discharge standard:

All this size criteria are corresponding, more or less, to the different parts of the sea water life form. The organisms that are or are bigger than 50µm represent the Zooplankton. The zooplankton is the animal part of the plankton.

 

The organisms with a size between 10 and 50µm are mainly from the phytoplankton, the vegetal part of the plankton.

 

After treatment different methods could be used to quantify the microorganisms from the three fractions (=50µm; <50 and =10µm; bacteria indicator):

Chlorophyll measurement :
A fluorimeter is used to emit light that will put the chlorophyll in an exciting state that will generate in return a second light with another specific wavelength that will be measured by the fluorimeter. The quantity of light will be used to estimate the phytoplankton biomass.

Culture dependent methods (dilution culture, plate counts) :
After filtration, the filter where bacteria are on, is put on selective medium in culture plate and incubated for few days before counting.

Fluorescein di-acetate hydrolysis assay (FDA) :
Fluorescein diacetate is an esterase substrate that release green bright fluorescence after its hydrolysis; esterases are unspecific enzymes that are in every living cell.

ATP assay :
ATP is the energy carrier produced by all living organisms; with intracellular ATP assay you can estimate the amount of total living biomass in a sample.

Flow cytometry :
Depending on the fraction, sample has to be stain with fluorescent marker before being analyzed. Then this machine can count cells depending on their size and/or fluorescence.

Direct counts with microscope in combination with fluorescent stains (FISH) :
Organisms have to be stained with specific fluorescent markers. Under microscope a laser is used to excite the markers that will emit a luminescent signal that allow the user to see and count marked cells.

According to the description above, each technique has its own advantage/disadvantage that are summarize in the following table for a quick comparison.

Table. Quick comparison of methods usable for regulation D-2 compliance.