Description

Problem summary

The problem we're trying to address is to find a material alternative to antifouling compounds, which are worldwide used in the formulations of paints to prevent settlement of biofouling on boats, tubes, and objects immersed in water to reduce the use of both fuel and maintenance. Biofouling results from the natural association of sessile organisms encrusting submerged hard substrates, the composition and succession of which depend on geographic location, type of substrate, physico-chemical characteristics, and seasonal climatic conditions. Macrofouling on artificial objects causes economic damage, which results in high costs, due to continuous maintenance of structures, and increases in fuel consumption to offset hydrodynamic loss by ship’s hulls. On the other hand, it is also important to consider the severe damage to biodiversity caused by these xenobiotic mixtures in costal marine biocoenoses, particularly fragile ecosystems like that of the Lagoon of Venice, rich in micro-environments and endemism.

From the 1960s onwards, organotin compounds were massively introduced in the formulation of antifouling paints. These substances proved to be harmful to benthic biocenoses and persistent in the environment. The damages, also economic, caused by organotin compounds in the past are well known: imposex in molluscs, bioaccumulation in fish and cetaceans, immunotoxicity and embryo-larval toxicity in many benthic invertebrates. After the ban of organotin compounds by the IMO-MEPC  and subsequently by the EC (directive 782/2003), industries turned their attention to replacement biocidal formulations containing a main biocide and either newly synthesised booster substances - like Sea Nine 211 - or ones from the pharmacological (bactericides like Zinc pyrithione) or agriculture (herbicides, fungicides, insecticides like Diuron, Irgarol 1051, TCMS pyridine, Zinc carbamate or Zineb, Chlorothalonil, Dichlofluanid, Endosulfan) industries, in order to enhance paint performance against a wider spectrum of fouling organisms and prevent both the settlement of spores and larvae, and the formation of bacterial and microalgal film (biofilm), from which the ecological succession of hard-substrate biocoenoses begins. Although these compounds have a shorter half-time than organotins in the environment, a few or, in some cases, no information is known about the fate of themselves and their derivatives in the environment, the rate of bioaccumulation and biomagnification throughout the trophic chains and the effects on non-target organisms and their biocoenoses, thus representing an ecological problem.

Proposed research

Geotextile materials find increasing use in coastal protection as an alternative material to natural stone, slag, and concrete. In this environment, geotextile, like all surfaces of technical objects immersed in seawater, are subject to be covered by biofouling.  However, recent 2-years experiments in the Elbe estuary (Germany) by M.A. Wetzel demonstrated that panels covered on non-woven fabric geotextiles was colonized by significantly less species, fewer individulas, and lower biomass values than those of woven fabric geotextiles and the control panels. The Lagoon of Venice represents a fragile ecosytem of transitional waters rich in species of the macrofouling of hard substrate.

The aim of this project is of studying the effects of geotextiles on the macrofouling biocoenosis of hard substrate in the Lagoon of Venice with two aproaches.

1)  Effects on macrofouling of hard substrate (field research). These are long-term experiments on settlement capability of the biofouling on panels covered by geotextiles and immersed for at least one year in the Lagoon of Venice. Data will be collected monthly and compared with those of both control panels as regards largely used parameters:  physical and chemical parameters of the seawater (temperature, salinity, pH, total dissolved solids, turbidity), and biotic parameters (number of species, covering-abundance index, benthic community structure, similarity index).

2) Effects on ascidian larval settlement. Experiments on larval settlement and metamorphosis capability will be carried out in the lab with the colonial ascidian Botryllus schosseri, which is common in the lagoon of Venice where it is the dominant species of  the "Botryllus community" at the end of the relative climax of the macrofouling biocoenosis of hard substrate and is reared in our lab since 1950s. Experiments will be carried out for 24-48 on little glass plates (10 x 10 cm) covered or not by geotextiles and compared with the effects on glass plates covered of at least five common types of antifouling paints. Survival, morphological changes, adhesion to substrate will be evaluated statistically (lab reserach).

We have previously carried out 1-year experiments in the Lagoon of Venice with panels covered by various antifouling paints of the market in comparison with both panels treated with organotin compounds and untreated wood and steel panels (Cima F. & Ballarin L., 2008. Effects of antifouling paints alternative to organotin-based ones on macrofouling biocoenosis of hard substrates in the Lagoon of Venice. Fresenius Environ. Bull., 17: 1901-1908). Results revealed an order of biocidal efficacy (as significant long-term alteration of the structure of biocoenoses) of the tested antifouling paints by means of direct observations of panels monthly and on the basis of results expressed by means of four biodiversity indexes: number of species, covering-abundance index, benthic community structure, similarity index. 

Team

• Dr. Federico Caicci, PH.D., technician (University of Padova, Italy); Dr. Filippo Schiavon Ph.D. student (University of Padova, Italy); Dr. Markus A. Wetzel, PH. D. (German Federal Instutute of Hydrology, Germany)
• Dr. Caicci and Dr. Schiavon are expert of ascidian rearing and biology. Dr. Wetzel is expert of geotextile materials. 

Environment

• We'll be supported by facilities of the Department of Biology in Padova (Italy) and by the Hydrobiological Station "U. D'Ancona" in Chioggia (Venice) of the University of Padova.
• We'll prepare in our lab all tools for the experiments (aquaria and termostatic room for ascidian rearing, panels, geotextiles, antifouling paints, computer for digital images and data processing, multiparametric probe instrument, spectrophotometer, light and electron microscopes). The Hydrobiological Station will provide the boat for excursions in the Lagoon.

Project outcome and impact of result

Project outcome and impact of results :

• The end-result of the project is an evaluation of the geotextiles as alternative materials of antifouling paints in covering anthropic structures without effects on ecosytems.
• This research will open a new scenario on the problem of biofouling solving it without the use of biocides.
• This research appears to be important, urgent and relevant for stopping the continuous introduction of biocides in the environment and finding equilibrium between anthropic activities and safeguarding of fragile ecosytems with simple and not expensive tools like geotextile materials.
• The results will be published in extenso on peer-reviewed journals with I.F.
• This research will open new international research collaborations also involving academic institutions and industries.
• We are pleased to share the data and results publicly and make them available to the community.

References

• https://sites.google.com/site/ascidianbiologylab/our-staff/francesca-cima