|
Sea-surface temperature (SST) is an important control factor to the distribution patterns of planktonic foraminifers. In previous research, transfer functions were developed for estimating SST based on planktonic foraminifers have large biases and uncertainties for the low-latitude ocean. In order to understand the complex relationships between the planktonic foraminifers and surface ocean environments in the low-latitude ocean, this study was designed to collext data of 210 coretops data and 20 hydrographic parameters from the South China Sea(SCS), an important tropical marginal sea of the western Pacific. The objectives of this research are to understand: (1)how many kinds of hydrographic parameters are important to planktonic foraminifers except for SST; (2)what characteristic assemblages of planktonic foraminifers can be used to indicate different hydrographic properies between the SCS and the Western Pacific Ocean (WPAC); (3)what planktonic foraminifer assemblages can be used to indicate different hydrographic properies in the north/south SCS. We adapted three statistical techniques to examine the relationships between the planktonic foraminifers and surface ocean environments of the SCS. Results shows that the distribution pattern of planktonic foraminifers is associated with various surface ocean environments. In the SCS, the abundances of G. menardii are relatively higher than those in the WPAC. In constant, In the WPAC, P.obliquiloculata and N.dutertrei are more abundant than in the SCS. The different faunal abundance pattern may be related to the different regional hydrographic structure of the SCS and WPAC (depth of thermocline, pycnocline, and others). G. ruber and G. sacculifer are two dominant species in the southern SCS. These two species are associated with warm SST, low sea-surface salinity(SSAL), low sea-surface density(SSD), shallow depth of thermocline(DOT), and less mixed in the upper-layer environments during the winter; low SSAL, low SSD, ddp DOT, and more mixed in the upper-layer environments in the summer; and relatively low nutrient contents in comparing with those in the north SCS. G. glutinata and N.dutertrei are major species in the northern SCS. These two species are associated with low SST, high SSAL, high SSD, deep DOT, and more mixed in the upper-layer environments during the winter; high SSAL, high SSD, and less mixed in the upper-layer environments during the summer; and relatively high nutrient contents in the southern SCS. The north/south fauna distribution patterns may be also related to the riverine input of organic matter into the SCS. The SST and mixed-layer depth(MLD) seem to be the two most important controlling factors to the planktonic foraminifer distributions, For upwelling species, the other important factors are SSD, SSAL and nutrients. For shallowdwelling species, depth of halocline(DOH) are also affects the faunal distributions; For deep-dwelling species, DOT, DOH and depth of nutricline(phosphate)(DOPH) are additional factors to the fauna distribution. This research concludes that the use of only single hydrographic parameter can not fully explain the distribution of the planktonic foraminifers in the SCS. We must consider the contribution from the other hydrographic controls.
|