OBSERVATIONS ON PHYTOPLANKTON PRODUCTIVITY IN RELATION TO HYDROGRAPHY IN THE NORTHERN ADRIATIC

This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997.     

Quantitative relationships among phytoplankton body size classes and production processes in the North Adriatic frontal region

The variation patterns of phytoplankton standing crop and productivity in the North Adriatic frontal region and the relative importance of pico-, nano-, micro-phytoplankton are shown. Data of standing crop (chlorophyll a - Chl a ) and productivity ( 14 C assimilation) and PAR radiation ( w Em m 2 r s m 1 ) were collected during the four oceanographic cruises of the PRISMA II project. Average standing crop and productivity in the study area were 1.41 - 0.42 r mg r m m 3 Chl a and 1.23 - 0.37 r mg r C r m m 3 r h m 1 ; average assimilation number (P/B) was 0.872 - 0.589 r mg r C (mg-Chl a ) m 1 h m 1 and average photosynthetic efficiency (PE) was 0.020 - 0.054 (mg r C(mg-Chl a ) m 1 r h m 1 ) [ w Em m 2 r s m 1 ] m 1 . Phytoplankton biomass and productivity showed significant patterns of variation with the distance from the coast, with increasing depth and decreasing light intensity. The same patterns were shown by the three phytoplankton size classes. The spatio-temporal variations were significantly larger within the microplankton than within the pico- and nano-plankton size classes. Planktonic guilds were dominated by picoplankton, both as standing crop and productivity, in the northern stations (0.539 - 0.21 r mg r m m 3 Chl a and 0.572 - 0.25 r mg r C r m m 3 r h m 1 ) and in those more offshore, while microplankton was more important in the coastal and southern stations (0.727 - 0.58 r mg r m m 3 Chl a and 0.63 - 0.28 r mg r C r m m 3 r h m 1 ). In relative terms, picoplankton accounts for the 53% and 46% of biomass and primary production, while the microplankton account for the 43.6% and 48%. Assimilation number and photosynthetic efficiency did not show spatio-temporal variations but PE was inversely related with PAR radiation for all the size classes. Data suggest that the spatio-temporal patterns observed in this study are affected by the competitive relationships among body size classes in the phytoplankton guilds.     

EGG PRODUCTION AND HATCHING SUCCESS IN NORTH ADRIATIC SEA POPULATIONS OF THE COPEPOD Acartia clausi

Egg production, fecal pellet production and hatching success are reported for Acartia clausi females sampled during three cruises in February 1997, 1998 and June 1997 at 20-24 stations along 4 transects in the North Adriatic Sea. Dramatically low hatching rates were recorded during both diatom bloom events in February as opposed to much higher rates during post-bloom conditions in June, even though A. clausi productivity during the bloom was apparently high. These results are discussed in the light of recent findings on the negative impact of diatoms on copepod reproductive potential.     

杉木林凋落物产量、分解率与储量的关系

在福建三明采用2种方法测定27a生杉木林的杉木叶和小枝凋落物的分解率．采用网袋法(孔径0．5mm尼龙网袋)测定的杉木叶和小枝凋落物残留率Olson指数模型的分解系数(k值)分别为0．7692a^-1和0．2501a^-1，相应的第1年的分解率分别为53．66％和22．13％；另一种测定矗值的方法较为准确，是通过计算凋落物年产量与地面凋落物储量的比值得到，采用该方法计算的杉木叶和小枝凋落物的矗值分别为1．788a^-1和0．8622a^-1，分别是网袋法测定值的2．32和3．54倍，相应的第1年的分解率分别为83．27％和57．78％，分别是网袋法测定值的1．55倍和2．61倍．采用后一种方法测定的凋落物分解率可以解决尼龙网袋法测定分解速率结果偏低的问题．     

松花江水中酚类化合物生物降解性的测定及QSBR研究

以松花江水中细菌为接种源,用碘量法分别测定了１８种酚类化合物的ＢＯＤ５值采用ＱＳＡＲ程序软件计算得分子量ＭＷ、分子体积ＭＶ、疏水性参数ｌｇＰ及电离常数ｐＫａ．用ＭＭＰ软件计算了四种分子连接性指数(２ｘ,４Ｘ,２ｘＶ及４ｘＶ)．对１８种及训练组中的１４种酚类化合物ＢＯＤＴ值分别与其结构参数进行了回归分析,得到如下最佳回归方程:应用所得ＱＳＢＲ模型,拟合了１８种化合物的ＢＯＤ５值,计算了残差,预测了实验组中４个化合物的ＢＯＤＴ值,并初步探讨了生物降解机理．