冲绳海槽北部PC-1岩芯24 cal.kaBP 以来孢粉记录的古环境信息

东海陆架是世界上最宽阔的陆架之一，面积达770 000 km2左右。在末次冰盛期（LGM），东海海平面下降120～130 m左右，绝大部分陆架暴露出海面。而冲绳海槽是第四纪以来一直保持海洋环境的东海深海区。本文以冲绳海槽北部PC-1岩芯为材料，通过分析该孔的孢粉，加上详细的AMS 14C测年，恢复了周边地区24 cal.kaBP以来的古植被，并推测古环境和古气候变化，重点讨论了LGM时期出露大陆架上发育的植被。 PC-1孔（31°27.5′N，128°24.8′E）位于黑潮支流对马暖流东侧，水深590 m，柱长812 cm。孢粉分析按间隔8 cm取样，个别为4~6 cm，共分析了103个孢粉样品。利用9个AMS 14C数据建立年龄标尺，用Calib5.1.0软件进行年龄校正。通过相邻样品深度的线性内插获得每个样品的年龄，采用外延法得到顶部和底部的校正年龄分别为351cal aBP、24 280 cal aBP，孢粉样品的时间分辨率平均为230 a。 根据孢粉百分比和沉积率的变化，可划分出四个带：Ⅰ带（812～715 cm，24.2～21.1 cal. kaBP）、Ⅱ带（715～451 cm，21.1～15.2 cal. kaBP）、Ⅲ带（451～251 cm，15.2～10.8 cal. kaBP）、Ⅳ带（251～0 cm，10.8～0.3 cal. kaBP），分别对应MIS 3末期、末次冰盛期、冰消期和全新世。末次冰盛期草本植物花粉占优势，孢粉沉积率较高，此时草本花粉主要来源于出露的大陆架，其上发育了以蒿属为主的草地植被，气候比较寒冷干燥；冰消期海平面开始回升，松属花粉含量升高，草本植物花粉含量下降；全新世以木本植物花粉占绝对优势，栗属－栲属花粉迅速增加，蕨类孢子含量升高，草本植物花粉含量锐减，孢粉沉积率降低，由于海平面回升，大陆架被淹没，此时孢粉主要来源于日本岛，九州地区生长了以栲属、栎属为主的常绿阔叶与落叶阔叶林，气候温暖湿润。 叶枝杉属花粉在整个岩芯中零星出现。叶枝杉属植物分布于菲律宾吕宋北部至塔斯马尼亚和新西兰气候潮湿的山地林中，该属花粉在岩芯中的出现，可能暗示了黑潮的影响或者是较强的夏季风。 草本植物与松属花粉百分比变化很好的反映了海平面的升降，松属花粉含量较高指示海平面较高。对岩芯中主要类型的花粉百分比进行了频谱分析，显示存在千年尺度的准周期变化，有明显的6.8，3.8，2.2，1.6 ka的周期。 孢粉样品中的炭屑统计表明，末次冰消期炭屑含量最高，可能因为末次冰消期降雨量增加，炭屑可被降水带到沉积地点沉积下来；全新世的炭屑浓度较高，尤其在晚全新世，出现了一个峰值，究其原因可能与气候变化和人类活动有关。

Major and trace element analytical methods of the National Status and Trends Program: 2000-2006

This document contains analytical methods that detail the procedures for determining major and trace element concentrations in bivalve tissue and sediment samples collected as part of the National Status and Trends Program (NS&T) for the years 2000-2006. Previously published NOAA Technical Memoranda NOS ORCA 71 and 130 (Lauenstein and Cantillo, 1993; Lauenstein and Cantillo, 1998) detail trace element analyses for the years 1984-1992 and 1993-1996, respectively, and include ancillary, histopathology, and contaminant (organic and trace element) analytical methods. The methods presented in this document for trace element analysis were utilized by the NS&T Mussel Watch and Bioeffects Projects. The Mussel Watch Project has been monitoring contaminants in bivalves and sediment for over 20 years, and is the longest active contaminant monitoring program operating in U.S. costal waters. Approximately 280 Mussel Watch sites are monitored on biennial and decadal timescales using bivalve tissue and sediment, respectively. The Bioeffects Project applies the sediment quality approach, which uses sediment contamination measurements, toxicity tests and benthic macroinfauna quantification to characterize pollution in selected estuaries and coastal embayments. Contaminant assessment is a core function of both projects. Although only one contract laboratory was used by the NS&T Program during the specified time period, several analytical methods and instruments were employed. The specific analytical method, including instrumentation and detection limit, is noted for each measurement taken and can be found at http://NSandT.noaa.gov. The major and trace elements measured by the NS&T Program include: Al, Si, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Sn, Sb, Ag, Cd, Hg, Tl and Pb.

Diet shifts of juvenile red snapper (Lutjanus campechanus) with changes in habitat and fish size

We examined the diets and habitat shift of juvenile red snapper (Lutjanus campechanus) in the northeast Gulf of Mexico. Fish were collected from open sand-mud habitat (little to no relief), and artificial reef habitat (1-m3 concrete or PVC blocks), from June 1993 through December 1994. In 1994, fish settled over open habitat from June to September, as shown by trawl collections, then began shifting to reef habitat — a shift that was almost completed by December as observed by SCUBA visual surveys. Stomachs were examined from 1639 red snapper that ranged in size from 18.0 to 280.0 mm SL. Of these, 850 fish had empty stomachs, and 346 fish from open habitat and 443 fish from reef habitat contained prey. Prey were identified to the lowest possible taxon and quantified by volumetric measurement. Specific volume of particular prey taxa were calculated by dividing prey volume by individual fish weight. Red snapper shifted diets with increasing size. Small red snapper (<60 mm SL) fed mostly on chaetognaths, copepods, shrimp, and squid. Large red snapper (60–280 mm SL) shifted feeding to fish prey, greater amounts of squid and crabs, and continued feeding on shrimp. We compared red snapper diets for overlapping size classes (70–160 mm SL) of fish that were collected from both habitats (Bray-Curtis dissimilarity index and multidimensional scaling analysis). Red snapper diets separated by habitat type rather than fish size for the size ranges that overlapped habitats. These diet shifts were attributed to feeding more on reef prey than on open-water prey. Thus, the shift in habitat shown by juvenile red snapper was reflected in their diet and suggested differential habitat values based not just on predation refuge but food resources as well.

Biology and population dynamics of cowcod (Sebastes levis) in the southern California Bight

Cowcod (Sebastes levis) is a large (100-cm-FL), long-lived (maximum observed age 55 yr) demersal rockfish taken in multispecies commercial and recreational fisheries off southern and central California. It lives at 20–500 m depth: adults (>44 cm TL) inhabit rocky areas at 90–300 m and juveniles inhabit fine sand and clay at 40–100 m. Both sexes have similar growth and maturity. Both sexes recruit to the fishery before reaching full maturity. Based on age and growth data, the natural mortality rate is about M =0.055/yr, but the estimate is uncertain. Biomass, recruitment, and mortality during 1951–98 were estimated in a delay-difference model with catch data and abundance indices. The same model gave less precise estimates for 1916–50 based on catch data and assumptions about virgin biomass and recruitment such as used in stock reduction analysis. Abundance indices, based on rare event data, included a habitat-area–weighted index of recreational catch per unit of fishing effort (CPUE index values were 0.003–0.07 fish per angler hour), a standardized index of proportion of positive tows in CalCOFI ichthyoplankton survey data (binomial errors, 0–13% positive tows/yr), and proportion of positive tows for juveniles in bottom trawl surveys (binomial errors, 0–30% positive tows/yr). Cowcod are overfished in the southern California Bight; biomass during the 1998 season was about 7% of the virgin level and recent catches have been near 20 metric tons (t)/yr. Projections based on recent recruitment levels indicate that biomass will decline at catch levels > 5 t/yr. Trend data indicate that recruitment will be poor in the near future. Recreational fishing effort in deep water has increased and has become more effective for catching cowcod. Areas with relatively high catch rates for cowcod are fewer and are farther offshore. Cowcod die after capture and cannot be released alive. Two areas recently closed to bottom fishing will help rebuild the cowcod stock.