Biogeochemical Cycles Of Phosphorus In Ice-free Areas And Inshore Zone Of Antarctica

One of the basic functions of the ecosystem is the material flow. Material flow is cycle, which belongs to the biogeochemical cycles. The formal implementation of the International Geosphere-Biosphere Programme (IGBP) in1991focuses on the biogeochemical cycles of material, and its goal is to illustrate the physical, chemical and biological processes which control of the earth system and its evolution of interacting, and to understand the function of human activity in the biogeochemical cycles of material.Phosphorus (P) is one of the basic biogenic elements. The cycle of P generally starts from the weathering of rocks and terminates in sediment. Thus, it belongs to the sedimentary cycle. Moreover, the period of P cycle is very long, so the deposition of P in the sediment is difficult in returning to the land timely. Thus, P cycle is also an incomplete cycle. Currently, many researchers have expressed worry about the global P scarcity in the21st century. The marine sediments have enormous P, which can return to land by sea level rise, upwelling seawater, commercial fishing and birds transfer. However, the study of the mechanism and the amount of P transfer from marine to the land is still limited.The marine ecosystem is dynamically interrelated with the terrestrial ecosystem. Antarctic penguins, seals and other marine organisms feed on the krill, fish and other foods in the Southern Ocean. When they breed regularly in the ice-free areas, they will transfer a large number of P in the form of gunao, debris, eggs, etc., from sea to land. Thus, this paper chooses Antarctica as study area, and focus on the closed and open scale of P biogeochemical cycles in the ice-free area and inshore zone. The contents are summarized as follows:1) In organisms (or guano) of different trophic levels, P content is enriched by as high as1.59×104-3.58×106times relative to the background value through the food chains of the Southern Ocean. Penguins are the largest number of seabirds in Antarctica. We chose three important colonies of penguins, the most important seabirds in Antarctica, and computed the annual quantity of P transferred by penguins from sea to land. Our results showed that adult penguins in Ardley Island, Vestfold Hills and Ross Island, could transfer in the form of guano up to12349kg/y,167036kg/y, and224200kg/y of P, respectively, over the entire breeding period. These quantities are equivalent of an annual input of5,77x1012-2.37×1013kg of seawater to land of Antarctica. Finally, we discussed in detail the factors of climate, environment, human disturbance, and food availability, etc., that impact of P transfer.2) This study focuses on the characteristic of elemental concentrations of moss, Andreaea Hedw and its relationships with different habitat environments at Zhongshan Station, East Antarctica. For this purpose, samples of moss and the underlying sand substrates from4sites around Zhongshan Station were collected and analyzed for the elemental concentrations of Fe、Mg、P、Na、Mn、Cu、Zn、Sr、 Ni and Pb. The elemental concentrations of mosses and sand substrates among the4sampling sites show some different characteristics. The average concentration of Fe in mosses and sands show highest level with10014.73mg/kg and24405.48mg/kg, respectively. Element Mg had the second highest mean concentration in both moss and sand, while the concentrations of the other8elements were inconsistent between moss and sand. Moreover, the relationships between elemental concentrations in moss and its habitat environments such as sand substrate, altitude, seabird impact, marine influence as well as the anthropogenic factor were discussed. Finally, we analyzed the relationship among mosses and the sand substrates.3) Distribution and vertical variation of P forms in the sediment cores from two typical lakes of Ardley Island were studied, using the standard measurement and test (SMT) procedure of P forms for the freshwater sediment. Combined with the percentages of inorganic phosphorous (IP) and organic phosphorous (OP) to total P (TP) in mosses and penguin guano, we analyzed the sources of material in the two profiles, and studied the correlation coefficients among the forms of P. Moreover, the correlation coefficients between sediment P and the loss on ignition at550℃, water content, TC and TN. Finally, the potential bio-availability phosphorus (BAP) was discussed.The results showed that IP has smaller proportion (28.71%) to TP in mosses. The two profiles were both affected by moss and penguin guano, and G1was more strongly influenced by penguin (95.05%) than Q2(90.99%). The TP concentration of G1and Q2were1032-4898mg/kg and960-2127mg/kg, respectively, and IP was the main part of the two core sediments. However, the distribution and vertical variation of P forms in the two profiles were inconsistent. Besides, difference was obvious in the correlation coefficients between different P fractions and sediment geochemical characteristics (loss on ignition at550℃, water content, TC, TN) in the two studied profiles. Estimation showed that the average contents of bio-availability phosphorus (BAP) in Gl and Q2were1322.17mg/kg and683.51mg/kg. Thus, Gl profile had much higher BAP than Q2, and the potential release of P to water bodies was also higher, which would have extremely role in maintenance the biodiversity of barren Antarctic ice-free ecosystems.4) Taking the Fildes Peninsula in West Antarctica as an example, we investigated the records of P transported by penguins, seals in terrestrial and freshwater ecosystems. Results showed that the input of P by marine animals would generally increase the P content in soil, plants, water and sediments etc.5) Taking Ardley Island, the maritime Antarctic, for instance, we studied the transport process and mechanism of the biogeochemical cycling of P and estimated the fluxes of P cycle. Results showed that P biogeochemical cycle in Antarctica includes the migration and transformation of P in the sea-land-lakes/streams-sea. In this island, there were three ways of external input, including physical transport, bio-transport, and atmospheric deposition. Remarkably, the P transported by penguins in the form of guano accounted for94.34%-99.74%of the total P input, thus has the dominant role. The output ways of P included atmospheric output, physical output (that is, water and wind output), and the amount of material output by water was biggest among the three ways. In addition, the amount of P conserved on ice-free areas by bio-transport of P was about1358.39kg/y, and most of them were entering into offshore of Antarctica.The innovations are as follows:1) For the first time, we study the biogeochemical cycling mechanism and cycle flux of P in ice-free areas and inshore zone in Antarctica from the closed and open scale. Then, we illustrate the ways of material transferred from sea to land and the influences that material pose on ecosystems of ice-free areas. Also, the ways of material transport to inshore zone and its impacts on coastal ecosystems are also discussed. Finally, we explicitly explain the dominant role of penguin in the biogeochemical of P in ice-free area and inshore zone of Antarctica.2) Distinguish the proportion of IP and OP to TP in mosses and penguin guano, combined with the forms of P in sediments, we investigate the material sources in sediments. This method will be the powerful compliment to the way, which uses organic geochemistry in distinguishing the sources from penguins and plants.