###### Abstract
In the presence of Ca\({}^{2+}\) ions, calcium carbonate is then formed and precipitated, which is effective for the binding of sand particles and for the filling of micro-space:  
\[\mathrm{Ca^{2+}}+\mathrm{HCO_{3}^{-}}+\mathrm{NH_{3}}\xrightarrow{HCO_{3}} \downarrow+\mathrm{NH_{4}^{+}}. \tag{3}\]  
In the MICP method, precipitation of carbonate minerals is an important factor that occurs through extracellular or intracellular pathways by a sequence of chemical reactions and physiological pathways, which are a key factor for the making of solidified sand that is close to natural beachrock, and could be effective for various bioengineering applications [12]. Therefore, for successful implementation of the MICP method in the bio-geoengineering field, environmental factors such as temperature, pH, duration of bacterial cultivation, and crystal precipitation tendency need to be assessed. In the MICP method, most of the earlier studies addressed ureolytic bacteria as a specific foreign microorganism, and there was a major concern about the adverse effects (for example, competition for nutrients with other species, survival capacity in the new environment, dormancy or sudden shock) on the surrounding environment due to the presence of a large number of foreign species [11; 12; 13; 14]. Therefore, to overcome this adverse effect, this study aimed to reduce the impact on ecosystems by isolating urea degradation bacteria from local marine sand (Greece), targeting for coastal erosion protection in that specific area (Greece), and later on we will focus on other areas where coastal erosion is a major problem. Isolated native strains were evaluated for urease activity as whole-cell, supernatant and cell pellets and subsequently different environmental parameters were investigated. On the basis of the results, the sand solidification test (syringe) was also performed, and the degree of solidification was quantitatively evaluated by the needle penetration test. Furthermore, for the practical use of this technology, we proposed a novel approach that is sustainable and eco-friendly, one we aim to apply in future for coastal erosion protection in the targeted area. Moreover, most of the research on MICP has been limited to land ureolytic bacteria [15; 16; 17; 18], focusing on the urea hydrolysis mechanism and on the efficacy of calcite production, and little consideration has been drawn for marine ureolytic bacteria and their subsequent application [5; 18; 19; 20]. However, some of the previous studies and scope of these studies are mentioned in Table 1. Nonetheless, in the present study, we selected marine ureolytic bacteria isolated from a coastal region in Greece, which has the most comprehensive coastlines among the Mediterranean countries and coastal erosion in this region is severe. In order to protect this long coastal shoreline from erosion, the application of the proposed MICP method was suggested towards the creation of artificial beachrock using native ureolytic bacteria because of its long-term sustainability, considering the local coastal climatic environment. Previously, it was revealed that the formation mechanism of beachrocks is greatly influenced by marine ureolytic bacteria, which show a great affinity for CaCO\({}_{3}\) precipitation and can be sustained for a long time, which is a key factor for the MICP method. Hence, we isolated three ureolytic bacterial species (16s rDNA analysis) from the Greek coastal area: _Microoccus_ sp., denoted as G1; _Pseudoalteromonas_ sp., denoted as G2; and _Virgibacillus_ sp., denoted as G3. We selected native ureolytic bacteria (from Greece) due to their sustainability (considering the temperature, pH, etc.) and high urease activity, which is very important for the making of artificial beachrock by the MICP method.