The impact of seabirds on the content of various forms of phosphorus in organic soils of the Bellsund coast, western Spitsbergen

In areas isolated from direct human impact, such as Spitsbergen, environmental changes result mainly from natural processes, which include nutrient enrichment caused by seabirds. The objective of this study was to evaluate the degree of nutrient enrichment of organic soils fertilized by seabirds, indicated by the phosphorus content and transformations. This study encompassed two areas on the Bellsund coast. A profile without the influence of seabirds and profiles located at different distances from the colony of birds (0 150 m) were analysed. A sequential phosphorus fractionation method was used, and three inorganic P (Pi) fractions were obtained as a result: Pi-L (labile P), Pi-FeAl (P associated with Fe and Al) and Pi-CaMg (P associated with Ca and Mg); and two fractions of organic P (Po): Po-HuAc (P associated with humic acids) and Po-Res (residual P). Polar organic soils not subjected to the direct seabird impact contained amounts of total phosphorus (Pt) similar to organic soils in other climate zones. The presence of the seabird colony increased the Pt content and changed the distribution between the ratio of organic and inorganic P fractions. Within the inorganic P fraction, the Pi-CaMg component was dominant and its distribution was modified by the fertilizing effect of bird droppings. The nutrient enrichment of organic soils by birds in the polar zone was therefore very strong.