Relationship between life stages (nauplius, copepodite and adult) of Acartia tonsa with physicochemical parameters and dominant Planktonic species in Mazandaran Coasts during summer (a modeling approach)

The relationships between life stages (nauplius, copepodite and adult) of Acartia tonsa with physicochemical parameters, and dominant planktonic species were investigated using Random Forest (RF) model along the Mazandaran Coasts during summer. Monthly sampling was conducted in 2012 along four transects (Amirabad, Babolsar, Noshahr and Ramsar) in different water layers at depths of 5, 10, 20 and 50 m. The results showed that the mean density of A. tonsa was1586 ind/m3. The spatial distribution of life stages showed that the density had decreasing trend from Ramsar, Amirabad, Babolsar to Noshahr, respectively. The density of each life stage of A. tonsa was also decreased with increase in depth and distance from the shore. Data evaluation through R-software showed that RF model had a good performance for identifying the most important factors in the distribution of the three life stages of A. tonsa (with accuracy of 97 %). It had been determined that the nauplius stage of A. tonsa had a noticeable relation with its copepodite and adult stages, temperature, phosphate, turbidity and larval stage of M. leidyi. Additionally, a close relationship was found between A. tonsa copepodite stage, and its nauplius and adult stages, temperature, larval stage (cydippid) of M. leidyi, nitrite and turbidity, while the adult stage had close relationship with its copepodite stage and cydippid stage of M. leidyi, nitrites, temperature, salinity and oxygen.