Observation of chlorophyli-a distribution in the Suruga Bay using the underwater tow device-SCAN FISH

本项目的目的是开发合适的方法来研究Suruga湾以及日本东部外海的浮游植物分布和春季水华机制。我们最初在日本附近的开阔海域使用水下拖曳装置-扫描鱼类观测系统(Macartney A/S，丹麦)，搭载在东海大学的BOSEI-MARU(1777t)RV上，记录了上层水柱的温度、盐度和叶绿素a荧光的垂直剖面。随后，我们对该系统进行了必要的可操作性改进，使其可以在苏里加湾的渔船等小型平台上使用。此外，我们还分析了从ORB VIEW 2/Sea WiFS和NOAA/AVHRR卫星获取的3年(1999-2001年)海温时间序列和海温数据，以监测苏鲁加湾海面热场的时空变化及其对近地表叶绿素a浓度的影响。我们进一步发展了经验方法来推导ClOp…的垂直剖面。更多的来自近地表色素浓度的hyll a用于卫星数据的实施。为此，在100m以内的表层和不同深度采集了现场水样，并用高效液相色谱法分析了叶绿素a的浓度。从时间序列数据中可以看出，2000年苏鲁加湾春季水华的开始时间比1999年和2001年推迟了一个月。我们根据苏鲁加湾及其周围不同的海洋学和气象数据得出的结果表明，水柱分层始于1999年和2001年的2月下旬。然而，在2000年2月下旬，这种层结在局地风的强烈影响下被破坏，形成了深层混合层。这样的条件不允许浮游植物在春季开花。结果表明，垂直层结是该湾春季水华现象的一个重要参数。我们进一步使用扫描FISH，观察不同海洋参数的垂直剖面以及氯代-a荧光，以了解水华现象的机制。盐度剖面对水体上部30m内叶绿素a的垂直分布的影响大于水温的影响，尤其是在海湾西段。盐度垂直分布与叶绿素a之间的密切关系凸显了密度分层在湾侧春季水华现象中的重要性。这可以归因于从西部边缘的四条主要河流涌入海湾的大量淡水。较少

Objective of our project was to develop appropriate methods to study phytoplankton distribution and spring bloom mechanism in the Suruga Bay as well as in open ocean waters off eastern Japan. We initially used the underwater tow device-SCAN FISH observation system (MACArtney A/S, Denmark) in the open ocean near Japan onboard RV BOSEI-MARU (1777t) of the Tokai University, to record vertical profile of temperature, salinity and chlorophyll-a fluorescence in the upper water column. Later we made necessary operational modification in the system to make it usable from smaller platforms such as fishing boats, in the Suruga Bay.Besides, we analyzed 3-year time series (1999-2001) of satellite derived ocean color and SST date respectively from Orb View2/Sea WiFS and NOAA/AVHRR to monitor spatial and temporal change in sea surface thermal field and its impact on near surface chlorophyll-a concentration in the Suruga Bay. We further developed empirical method to derive vertical profile of chlorop … More hyll a from the near surface pigment concentration for implementation on satellite data. For this purpose in situ water samples were collected during the cruises at surface and at different depths within 100m and chlorophyll a concentration was analyzed using HPLC technique.From the time series data it was noticed that beginning of the spring bloom in the Suruga Bay was delayed by one month during 2000 compared to 1999 and 2001. Our results based on different oceanographic and meteorological data in and around the Suruga Bay indicated that water column stratification started in the late-February in 1999 and 2001. However, during the late-February of 2000 such stratification got disrupted under strong influence of local wind creating deep mixed layer. Such condition did not allow phytoplankton to develop the spring bloom. Our results clearly indicated that vertical stratification is an important parameter in spring bloom phenomenon in the bay. We further used the SCAN FISH, to observe vertical profiles of different oceanographic parameters along with chlorohyll-a fluorescence to understand the mechanism of the bloom phenomenon. Vertical distribution of chlorophyll-a within upper 30m of the water column was noticed to be more strongly influenced by salinity profile than that of water temperature especially in the western sector of the bay. Strong relationship between vertical profile of salinity and chlorophyll-a underlines the importance of density stratification in the spring bloom phenomena in side the bay. This can be attrebuted to influx of plentiful freshwater into the bay from four major rivers along the western margin. Less