Methods improving the quality of the marine environment and ecological restoration of epibiotic bivalves
Cornel Ursache, Marian Paiu, Mare Nostrum – Constanta, Romania, 2013
Anthropogenic activities undertaken in the last decades in the coastal marine area have made significant changes in the marine substrate, also among invertebrates organisms that inhabited it, organisms whose major ecological role in maintaining a normal quality of sea water and the installation of a major ecological imbalance produced significant qualitative and quantitative changes in all components of marine ecosystems in the coastal area.
The negative aspects presented highlights the need to start concrete actions to improve the quality of the marine environment of shallow coastal areas, areas of particular importance for tourism and leisure activities because natural recovery is slow and insignificant.
Knowing the fact that the epibiotic bio filters have an important ecological role in self-purification of the marine waters and the fact that in the last decade restoring its natural coastal sectors, important in social and economic terms, was insignificant and it is necessary to find a feasible and appropriate method to ensure a faster and more efficient rehabilitation of both rocky clogged facies after extensive waterworks realized and epibiotic bio filters population affected by human activities.
Given the important role of the macrophytes and invertebrates in improving the quality of marine environment, including the areas affected by the anthropogenic impact, it requires knowledge of the current status of marine invertebrate’s populations of ecological and economic interest, in order to assess the biological potential of species or associations of species to promote conservation and rehabilitation programs.
To develop a method that matches, in technical and biological terms, to the ultimate goal pursued – restoring the rocky clogged facies and thus improving the natural epibiotic bio filter – have considered the geomorphological, hydrological, hydrochemical and biological conditions specific to coastal sectors, affected by the anthropic impact where is expected its application, relating to:
- Destructive effects of specific frequencies of natural weathering of Black Sea in the absence of housed areas at the Romanian seaside;
- Changes in the circulation of water masses in shallow coastal areas and the presence of strong currents, often foulcault currents, in the waters close to the basement.
- Thickness, structure and degree of compaction of terrigenous material deposited on the platforms and on the small humps of the rocky facies;
- Frequency of hypoxic condition present especially during summer in the water layer found in the immediate vicinity of the substrate that causes mortality among benthic organisms, conditions generated by the intensive processes of chemical degradation of organic detritus;
- Qualitative – quantitative fixations in space of epibiotic bodies on hard natural stands (rocks, platforms, excavations) and clogged areas of rocky facies, depending on the hydrological and hydrochemical conditions above mentioned as well as their evolution in time.
The method developed is suitable for the development of artificial reefs for the fixations of epibiotic bodies that should be placed in areas with rocky facies affected by silting. By using appropriate technical means the baring surface will be extended for the mentioned bodies and thus will significantly increase the ability of self-purification, of epibiotic bio filters formed on them.
The materials used for the construction of the artificial reefs -metal, concrete and stone pieces from demolition – are according with the legislative requirements, Law 310 of 28 June 2004 amending and supplementing Water Law 107/1996, published in Official Gazette of Romania, Part I, no. 244 of October 8, 1996, as amended.
Technical means usable/ artificial reefs to rehabilitate coastal sectors with rocky clogged facies from human activities are: concrete slabs, limestone blocks of rough stone, rigid protection hydrotechnics – gabions and underwater pyramid structures.
Experimental models have been designed and built according to technical documentation and were released for testing in real operating conditions in coastal area Mamaia Baia, on Singol Cap alignment, the 12 m isobaths, at a distance of 2 Mm from the shore. Launching and reinforcement in the sea the experimental models, was done in late March according to the launcher – outfitting set.
After launch and the reinforcement in the sea, decadal and after each storm that generated large waves and strong sea currents, were made controls by a team of divers to control and to check the anchor system (anchor position on the substrate), floating superstructure behavior, the fixing epibiotic material on the artificial supports, and their positioning in the horizon of 1-5 m, to ensure optimum performance.
Findings and spot checks made by divers’ team, who researched anchor position and the collectors, have concluded that the experimental models retained the shape and size of the initial project and the occurred loads under the action of external forces are uniformly distributed on anchorages and anchors.
At Romanian Coast of Black Sea, epibiotic bivalves are reproducing with variable intensities in almost all year. This fact is illustrated by the constant presence in the water, throughout the year, varying the amounts of mussels’ larvae. At times, however, increased periodic reproduction has the effect of the appearance in the water of numerous generations of larvae.
By analyzing the distribution of mussels’ larvae, it appears that water masses above the depth of 10 to 30 m are always best populated. Regardless of the distance from the shore, the horizon of 0 ÷ 10 m and to 10 ÷ 25 m remained always the most densely populated mussel larvae. This proves that the metamorphosis from egg to larva capable to fix, is ongoing in the water, near the surface and near the bottom where there are colonies of mussels generating larvae.
Since April, when the temperature reached 8 ÷ 100 C, there is a rapid increase in reproduction marked by the presence of increased amounts of larvae in a cubic meter, compared to previous months. More than 99% of them belong to the early stages of development and only very few are in advance stages of metamorphosis.
Depending on the specific hydroclimatic conditions from each year, till the end of November, when it is considered the end of a growing cycle of fixed epibiotic organisms, can reach approx. 9.0 – 9.5 kg/ m.l. the existing bodies on the artificial surfaces predominate the mussels, performing approx. 84% of biomass, being followed by cirripedia with approx. 4.94% of the total. The rest of the total available biomass, about 1% is the macrophyte algae and other epibiotic invertebrates.
Based on the results obtained in experiments on the ability of bio treatment of seawater by epibiotic organism, one kilo of epibiotic bio filters juvenile, of which 90% of the total is represented by the mussels, can bio purge in a cycle of 24 hours and 85 – 90%, a volume of 73 m3 seawater, having phytoplankton load of approx. 18 mil. cells/liter.
For an artificial barrier of reefs in an area affected by the anthropic impact, that should ensure efficient support for attachment and growth of epibiotic bodies can be used with great performance price, cost/ active area achieved, scrapped sleepers that can be launched directly in the sea or assembled in large pyramidal structures. Artificial reefs made of sleepers will realize natural epibiotic habitat for marine bodies or benthic fish species.
The production technology of marine eibiota on arranged artificial supports presented is an ecological method par excellence designed to promote the improvement of water marine quality in the coastal area of tourist interest with local epibiotic bio filters.