Voloshchuk E. V., Eremina T. R., Ryabchenko V. A.
The paper discusses the diagenetic model CANDI (carbon and nutrient diagenesis) which was used for assessment of biogeochemical changes in the upper layer of bottom sediments caused by bioirrigation activity of benthic organisms. For the conditions of the Eastern part of the Gulf of Finland the verification of the model is made, the comparability of the model calculations with the in situ observations is showed. The sensitivity of the model to the sediment porosity is tested; the dependence of the oxygen penetration depth in the sediments from organic matter content is showed. The bioturbation coefficient is calculated taking into account the population size of benthic organisms, providing a mechanical effect on bottom sediments. The modeling results show that constant bioirrigation influence on benthic layer can lead to the reduction of phosphates and ammonium reserve in 5 years as compared to the case of bioirrigation absence. The reserve of nitrates and sulfates, contrary, will increase. The reserve of solid iron of bottom sediments will not change significantly. It is concluded that cycles of biogenic elements and their associated dissolved compounds of iron will change significantly in 5 years in case of bioirrigation absence, which can lead to significant changes in benthic systems.