Beachrocks are early diagenetic coastal sedimentary formations derived mainly from the precipitation of CaCO3 cements in the intertidal zone. Natural beachrocks have attracted great attention as models to understand accelerated Microbial Carbonate Precipitation (MCP). Inspired by its natural capability to co-precipitate cement, sands, soils, minerals, metals, and to sequester CO2, MCP is a promising technology with potential applications in the fields of Material Sciences, Climate Change, Geobiotechnology or Geobioengineering. MCP can occur as a by-product of numerous metabolic activities, such as, photosynthesis, ureolysis, denitrification, ammonification, sulphate reduction and methane oxidation. Although MCP has been reproduced with the aid of phototrophic bacteria in specific bioreactors, further experimental studies to optimize the synthesis of beachrock (e.g., the use of different microbial communities, geochemical water doping, sediment constitution) are challenging. In natural systems, heterotrophic bacteria are frequently associated with phototrophs and can increase dissolved inorganic carbon (DIC) concentrations, which promote carbonate precipitation. In sum, phototrophic and heterotrophic microbes have a greater potential to alter the micro-pore geochemistry and induce MCP. This work presents an experimental approach using natural carbonate sand, mixing of fresh-marine waters, and a naturally enriched autotrophic-heterotrophic microcosm to reproduce Heron Island (southern GBR) beachrock through accelerated MCP. Dense Pisonia grandis forest and thousands of birds producing tonnes of guano cover Heron Island. Those enrich groundwater in phosphates and nitrates, which reach the mixing zone at the beach, creating the perfect nutrient microenvironment for the beachrock microbial ecosystem. Dominant, epilithic cyanobacterial pink mats and an heterotrophic inoculum derived from leaves and guano were used in an experiment conducted over several weeks using active growth-conditions for these microorganisms and strontium-doped seawater to track MCP. Standard BG11 and hot-water extractable organic matter from leaves and guano were utilized, respectively as nutrient media. MCP was investigated based on water geochemistry and the FE-SEM analyses of new carbonate sub-products. Finally, DNA analyses were conducted by the amplification of primers 926f/1392r from bacteria and archaea.