The Settlement And Spatial Distribution Of Fistulobalanus Albicostatus And Its Deposition Effect In The Spartina Alterniflora Marsh, Rudong Coast, Jiangsu Province

Abstract:Since Spartina alterniflora was transplanted on the Jiangsu coast in 1979, its rapid expansion has a great impact on sediment dynamics and environmental dynamics of the native coastal ecosystem. In recent decades, the introduction of S. alterniflora has aroused a heated discussion about its constructive role in coastal protection and its destructive effect on biodiversity of native ecosystems. In Rudong, Fistulobalanus albicostatus provides a typical example of the influence by the expansion of Spartina alterniflora. In the present study,28 quadrates of along 5 tidal creeks were sampled during October 2012, to collect the above-ground parts of Spartina alterniflora plants and the attached barnacles. The maximum elevation at which barnacles attach to the plants were measured in-situ, and analysis on size and weight of barnacles were carried out in laboratory. Moreover, a simplified model was proposed to estimate the contribution of barnacles’shell to marsh sediments.The results show that the barnacles are primarily distributed along the tidal creeks within a narrow zone, whose width is 5 m on average. Their maximum distance from the marsh margin bordering the tidal creeks largely depends on the size of tidal creeks, i.e., a larger creek is associated with a larger distance of extension. For each sampling station, the maximum height of barnacles attaching to the plants shows the same level at every site. But maximum attaching evaluation on the Spartina alterniflora of different sites shows the different evaluation. The evaluation increases logarithmically with distance from the marsh margin.Fistulobalanus albicostatus is the exclusive barnacle species in the study area. Its average biomass is 273±69g·m-2, and the diameter of most individuals ranges from 4 to 10 mm. The relation between the dry weight and diameter presents a power function with the power exponent of 2.7-3.9. And the mean biomass of Spartina alterniflora is 981±81g·m-2. Plants near the tidal creeks are tall and lower popularity density, while far away from the tidal creeks plants are undersized but higher popularity density.Correlation analysis indicates that although Spartina alterniflora provides the barnacles with an attachment base, its influence on the biomass and spatial distribution pattern is limited. The spatial distribution of barnacles attached to S. alterniflora plants is dominated by the duration of seawater inundation. Fistulobalanus albicostatus can survive for the minimum daily duration of seawater inundation of 0.86 h, and its biomass reaches the maximum value when the duration of seawater inundation is 3.65 h per day. Furthermore, the relatively strong current in tidal creeks is advantageous for the landward migration of larvae, and the frequent flood and ebb tides can bring about abundant food for barnacles.Finally, the outputs of simplified model show that the content of calcium carbonate produced by barnacles buried in marsh sediments is different on the tidal flats of different elevations, with the maximum value of 5.8%. In addition, the deposition pattern of calcium carbonate evolving with time can be divided into three types, characterized by rapid deposition on the higher part of tidal flats, slow deposition on the middle part of tidal flats, and the equilibrium of deposition on the lower part of tidal flats, respectively. The carbon sequestration capacity of barnacles is 27.8 g C·m-2·a-1 on average, with the maximum value of 95.0 g C·m-2·a-1, which is equivalent to the carbon sequestration capacity of vegetation in lake wetlands.