Seasonal Dynamics of Benthic Infauna Communities in Zostera marina Meadows: Effects of Plant Density Gradients

<i>Zostera marina</i> meadows play a key role in the Baltic Sea ecosystem. They are characterized by high primary production and provide feeding and reproduction grounds for organisms. These characteristics vary due to year-round environmental changes and may be due to the characteristics of the meadows themselves. Organisms inhabiting seagrass meadows are involved in the transformation of substances from terrestrial runoff, and, through bioturbation and bioirrigation, affect biogeochemical processes in the sediments. This study aimed to determine the structure of benthic communities inhabiting <i>Z. marina</i> meadows and their bioturbation (BP_C) and bioirrigation (IP_C) potential as affected by seagrass density and seasonal changes. This study shows a positive correlation between the density of <i>Z. marina</i> and the structure of macrozoobenthos, as well as the bioturbation and bioirrigation potential of the studied communities. The autumn season stimulated the density of macrofauna and recorded the highest values of their potential activities indices. The presence of <i>Z. marina</i> positively affects macrozoobenthic communities and their functioning regardless of seagrass density, indicating that seagrass meadows inhabited by macrofauna are key biotopes that can support biogeochemical processes in the coastal zone more effectively than bare sand.