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1.
Teruhisa Komatsu 《Journal of Oceanography》1989,45(2):106-115
This paper examines the influence of aSargassum forest on distributions of illuminance, dissolved oxygen content and pH in a small cove facing Wakasa Bay. Spatial distributions of illuminance, dissolved oxygen content, water density and pH were observed for June 1982 during the season of luxuriant seaweed growth, and for August 1982 during the season of little growth. Observations of dissolved oxygen content, water density and pH were made during the day and at night. The values of illuminance at the sea surface were decreased to less than 40% inside theSargassum forest when the sun was highest in the sky during the season of luxuriant growth. Density stratification occurred during every observation. Dissolved oxygen content and pH showed similar patterns of spatial distribution. Their horizontal distributions reversed from day to night, and consisted of two types: (1) higher values inshore and lower values offshore in the upper layer during the day with (2) lower values inshore and higher values offshore at night. Distributions of illuminance about noon, and dissolved oxygen content and pH at night showed patterns corresponding to the vertical distribution of algal density of theSargassum forest. Dissolved oxygen was supersaturated at every observation point during the daytime, but at night it was undersaturated in the lower part of the forest or along the bottom in June and August, respectively. Processes that brought about these spatial distributions are discussed. 相似文献
2.
Teruhisa Komatsu 《Journal of Oceanography》1985,41(4):235-243
This paper examines the influence of aSargassum forest on temporal fluctuations in temperatures of surrounding water in relation to the thermal structure of water in and above theSargassum forest. Water temperature records were obtained at about one-minute intervals for almost two days in May 1977 during the season of luxuriant seaweed growth, and in August 1977 during the season of little growth. The fluctuations were divided into two types. (1) A diurnal fluctuation under the forest with about a three hour lag behind that above the forest during the season of luxuriant growth but with about a 30 min lag during the season of little growth. (2) Sharp spike-like fluctuations with periods shorter than five minutes appearing only in the dense canopy or floating seaweeds in the surface and subsurface layers during the period of luxuriant growth. The luxuriant forest ofSargassum seems to influence the spatial distribution of water temperature and consequently seems to induce the fluctuations mentioned above. The relationship between short period fluctuations and behaviours of larval fishes are discussed. 相似文献
3.
Teruhisa Komatsu Hiroyuki Ariyama Hiroyuki Nakahara Wataru Sakamoto 《Journal of Oceanography》1982,38(2):63-72
The present study examined the influence of aSargassum forest on the spatial and temporal distributions of water temperature in a small cove on a time scale of the order of hours. Water temperature and algal density were measured along a fixed transect at the cove for almost 2 days. The measurements were carried out in May 1977 during the season of luxuriant seaweed growth, and in August during the season of little growth. The average standing crop per unit volume, named the spatial algal density, was employed as a means of expressing the growth condition of the seaweed forest along the transect. Using the spatial algal density and by analyzing water temperature distribution the following facts were revealed. The diurnal fluctuation of water temperature was influenced by theSargassum forest during the season of luxuriant growth, and the seaweed forest delayed the ascent and descent of water temperature, especially under its canopy, on a time scale of the order of hours, i.e., the temperature distribution patterns were influenced by the heights and densities of theSargassum forest during its season of luxuriant growth. It is thought that these phenomena are brought about by two effects: one is the absorption by the seaweed forest of short-wave radiation passing through the sea surface, and the other is the suppression of convection by the seaweed. 相似文献
4.
Some features of jump in water temperature in aSargassum forest 总被引：1，自引：0，他引：1
To clarify the influence of aSargassum forest on water temperature distributions observations were made inside and outside aSargassum forest off the Nagata Shore on the northern Saiki Bay open to the Bungo Channel on the Pacific side of Kyushu, Japan. About sixty thermistor probes were deployed at 0.5 m depth intervals from the bottom to the sea surface at seven stations spaced at 50–80 m distances along two transects: one inside the forest and the other outside. Water temperature was measured at five minutes intervals from 6 to 9 August 1987 with thermistor probes. The spatial standing crop distribution of theSargassum forest along the transects was investigated. A water temperature jump of about 2°C, recorded during the observation, is probably caused by an intrusion of a warm water mass from the central Bungo Channel to Saiki Bay. The water temperature jump under theSargassum forest on the rough bottom with stones occurred one to two hours behind that outside the forest (sandy bed) although the distance between the transects inside and outside the forest was only 50–80 m. It is suggested that theSargassum forest and the rough bottom would prevent intruding warm water from smoothly replacing cold water due to resistance of theSargassum species and the bottom to a current. 相似文献
5.
J. R. Rooker A. M. Landry Jr. B. W. Geary J. A. Harper 《Estuarine, Coastal and Shelf Science》2004,59(4):653-661
Trawl surveys were conducted in 2000 and 2001 to examine patterns of distribution and abundance of postsettlement red snapper (Lutjanus campechanus) on a shell bank, Freeport Rocks Bathymetric High (FRBH), in the northwestern Gulf of Mexico. In addition, otolith-based methods were used to determine age, hatch-date, growth and mortality of new recruits associated with FRBH. Date and region were significant factors affecting density of red snapper in 2000. Peak densities of red snapper were observed in July and August, and mean density among habitat types (shell bank, inshore mud, offshore mud) was similar (range: 50–52 ind hectare−1) in 2000. Alternatively, a habitat effect was detected during a limited survey conducted in 2001, with density higher on the shell bank than inshore or offshore mud habitat. Postsettlement red snapper were first detected at approximately 16 mm standard length, and individuals less than 20 mm were present in all habitats. Estimated ages of red snapper ranged from 26 to 121 d, with new settlers (≤20 mm) typically less than 28 d. Predicted hatch dates ranged from early April to mid August with a single peak occurring from late May to early June. Growth rate for the April–May cohort (0.817 mm d−1) was similar to the June–July cohort (0.830 mm d−1). Habitat-specific differences in growth were observed, and rates were highest for individuals from the inshore habitat (0.881 mm d−1). Mortality rates (Z) during the early post-settlement period were approximated using catch curves, and early life mortality of red snapper was 12.1% d−1 (Z=0.129). While the difference in mortality between cohorts was negligible, a habitat-specific difference in mortality was observed. Mortality rate of red snapper inhabiting the inshore mud habitat (Z=0.045, 4.4% d−1) was lower than rates observed for individuals on the shell bank (Z=0.120, 11.9% d−1) or offshore (Z=0.099, 9.3% d−1) habitat. Individuals residing in the inshore habitat had significantly higher growth rates and significantly lower mortality rates, suggesting that recruitment potential was higher for these individuals. 相似文献
6.
《African Journal of Marine Science》2013,35(1):229-237
The distribution patterns of saury eggs, larvae and early juveniles have been investigated over the continental shelf off the South-Western Cape from August 1977 to August 1978. Young saury tend to occupy water of 18°C or warmer in all seasons and are found offshore of the Benguela oceanic front when inshore upwelling is evident. Their distribution in the region appears to be linked to seasonal hydrography. Spawning in the study area occurs mainly between Cape Columbine and Cape Point, and to a lesser extent east of Cape Point. The ratio of large larvae and early juveniles to small larvae is greater off the West Coast than off the South Coast. Most spawning appears to take place in summer, with a peak abundance of larvae and early juveniles towards the end of this season. Instantaneous natural mortality was calculated: 5 – 30 mm, Z = 0,14·day?1; 30 – 100 mm, Z = 0,02·day?1. There is therefore a marked but unexplained decline in mortality shortly after the transition from the larval to the juvenile phase. 相似文献
7.
利用2009-2018年在南黄海苏北浅滩海域的现场调查数据，分析和研究了该海域漂浮绿藻和马尾藻的长期变化和季节性波动特征。研究显示，漂浮绿藻于每年4月中旬至下旬在浅滩中部筏架周围开始出现。5月－6月，漂浮绿藻生物量迅速增加，并漂移扩散至深水区。漂浮绿藻密度年际变化较大，但这十年间总体呈上升趋势。相比较而言，漂浮马尾藻仅在2013、2017和2018年在浅滩聚集形成春季藻华；且这三年，漂浮马尾藻密度超过同期漂浮绿藻。浅滩漂浮马尾藻的发生与发展过程与漂浮浒苔明显不同。3月，漂浮马尾藻开始出现于浅滩离岸海域，4-5月，漂浮马尾藻大量侵入浅滩，因此浅滩漂浮马尾藻现并非起源于本地。受高强度人类活动以及浅滩以外海域物理化学和生物过程的影响，浅滩环境因素与漂浮绿藻生物量的关系不甚明确。对于漂浮马尾藻的起源以及与漂浮绿藻的相互关系也需要进一步研究。 相似文献
8.
Attachment and feeding of pelagic copepods on larvacean houses 总被引：3，自引：0，他引：3
The attachment and feeding of pelagic copepods on discarded and occupied oikopleurid larvacean houses were investigated from May 1989 to August 1991 at an offshore station in the Nansei Islands, which is strongly influenced by the Kuroshio Current, and an inshore station in the central Seto Inland Sea.Oncaea spp.,Microsetella norvegica, and other calanoid and cyclopoid copepods were found attached onto discarded and occupied houses throughout the year at the offshore station, whereas neither discarded nor occupied houses, carried copepods at the inshore station at any time. The feeding behavior ofOncaea sp. in a discarded house was observed with a video tape recorder system. 相似文献
9.
溶解氧(DO)是海洋生物生存不可缺少的要素。随着人类活动的增加，全球近岸海域低氧情况愈发严重，已经成为威胁海洋生态系统健康的重要因素。通过对2017年5?9月秦皇岛外海区域的观测调查，探讨了该海域低氧与酸化的形成机制并计算了月平均耗氧速率。结果表明，5月秦皇岛外海水体混合较为均匀，表、底层DO浓度一致，均大于8 mg/L；6月开始形成密度跃层，与此同时底层DO浓度和pH开始下降；8月底层呈现明显的低氧和酸化状态，DO浓度下降至2～3 mg/L，pH下降至7.8以下；9月随着层化消失，底层水体DO浓度和pH逐渐升高。相关性分析显示，DO和叶绿素a (Chl a)以及pH具有良好的耦合性，说明秦皇岛外海区域的低氧发生过程主要为局地变化。同时表明DO浓度和pH主要受水体中浮游植物的光合作用和有机物有氧分解的影响。通过箱式模型计算得到2017年6?8月密度跃层以下水体及沉积物耗氧速率为951～1193 mg/(m2·d)[平均为975 mg/(m2·d)]。综合来看，水体分层是秦皇岛外海低氧和酸化发生的先决条件，跃层以下的有机物分解耗氧则是底层水体发生低氧和酸化的重要原因。 相似文献
10.
作者基于2011年9月(丰水期)和2012年1月(枯水期)粤西近岸30米以浅海域的调查资料,分析该海域浮游植物的种类组成、优势种、丰度及其群落结构多样性。结果表明,调查海域共鉴定浮游植物4门41属116种,硅藻为最主要优势类群。丰水期与枯水期共有种类40种,物种相似性指数为34.48%,表明2个调查季节种类组成变化较大,存在明显的季节性差异。枯水期优势种仅1种,为金藻门(Chrysophyta)的球形棕囊藻(Phaeoecystis globosa),优势度高达0.496;丰水期优势种有4种,其中以硅藻门的旋链角毛藻(Chaetoceros curvisetus)优势度较高(0.249)。浮游植物丰度表现出时间和空间异质性,丰度总体呈现近岸站位高于离岸站位,此外,丰水期浮游植物丰度湛江沿岸站位高于其他调查站位,枯水期浮游植物丰度则由西南部向东北部递减,总体而言,枯水期浮游植物丰度比丰水期高。群落结构多样性为枯水期西南部海域明显低于东北部海域,丰水期站位间多样性无明显变化规律,相比之下,丰水期群落物种多样性水平相对较高。相关分析表明:浮游植物丰度与p H、悬浮物呈正相关,与丰水期水温和枯水期盐度呈负相关。 相似文献
11.
J.R. Seymour L. Seuront M.J. Doubell J.G. Mitchell 《Estuarine, Coastal and Shelf Science》2008,80(4):589-597
Sampling was conducted within inshore and offshore sites, characterized by highly dissimilar hydrodynamic and hydrobiological conditions, in the Eastern English Channel. The eutrophic inshore site was dominated by the influence of a dense bloom of the Prymnesiophyceae phytoplankton species Phaeocystis globosa, while the offshore site was characterized by more oceanic conditions. Within each site the microscale distributions of chlorophyll a and several flow cytometrically-defined subpopulations of heterotrophic bacteria and viruses were measured at a spatial resolution of 5 cm. The inshore site was characterized by comparatively high levels of microscale spatial variability, with concentrations of chlorophyll a, heterotrophic bacteria, and viruses varying by 8, 11 and 3.5-fold respectively across distances of several centimeters. Within the offshore site, microscale distributions of chlorophyll a and bacteria were markedly less variable than within the inshore site, although viruses exhibited slightly higher levels of heterogeneity. Significant mesoscale variability was also observed when mean microbial parameters were compared between the inshore and offshore sites. However, when the extent of change (max/min and coefficient of variation) was compared between meso- and microscales, the variability observed at the microscale, particularly in the inshore site, was substantially greater. This pattern suggests that microscale processes associated with Phaeocystis globosa bloom dynamics can generate heterogeneity amongst microbial communities to a greater degree than large scale oceanographic discontinuities. 相似文献
12.
根据2013年8月(夏季)和2014年5月(春季)在曹妃甸邻近海域的调查资料,研究了浮游动物群落的种类组成、丰度、生物量、优势种和多样性的时空变化特征,分析了其与环境因子的关系,并结合2004年调查资料对比分析了浮游动物丰度和优势种的变化特征及围填海的影响。结果表明,研究海域浮游动物共鉴定得到31种(类),以桡足类和浮游幼体为主,优势种主要包括双刺纺锤水蚤(Acartia bifilosa)、小拟哲水蚤(Paracalanus parvus)、拟长腹剑水蚤(Oithona similis)和桡足类幼体(Copepodid larva)等。春季的浮游动物丰度和生物量均高于夏季,多样性和均匀度指数均低于夏季。浮游动物丰度的空间分布主要受温度、叶绿素a(Chl-a)等环境因子影响,春季基本为近岸高、远岸低的空间分布规律,夏季则相反,基本为近岸低、远岸高的空间分布规律。与2004年相比,本次调查春季和夏季的浮游动物丰度明显下降,可能与浮游植物丰度及DIP浓度降低有关。春季,西侧、东侧海域的浮游动物丰度分别明显降低、升高,与围填海后营养盐重新分布促进了东侧海域浮游植物增殖有关。夏季则主要受河流输入影响,浮游动物丰度的变化不具有空间差异。 相似文献
13.
北部湾北部海域水体异养细菌的时空分布特征研究 总被引：2，自引：1，他引：1
为探讨环境因素对异养细菌丰度的影响，2016年9月至2017年8月通过月度航次调查对北部湾北部海域异养细菌丰度的时空分布特征进行了系统研究。结果表明，调查海区异养细菌丰度介于（2.75~56.86）×105 cell/mL，平均值为（11.01±6.31）×105 cell/mL。各季节细菌丰度从高至低依次为:夏季、春季、冬季、秋季。异养细菌丰度由近岸海域向西南深水区方向逐渐降低，在近岸浅水区垂直分布均匀，在水深大于20 m的海区出现季节性分层现象:表层细菌丰度较高，底层细菌丰度较低。主成分分析显示温度对异养细菌时空分布有重要影响，秋、冬季异养细菌丰度与温度呈显著负相关，在春、夏季呈显著正相关。细菌丰度与盐度呈显著负相关，说明海水盐度变化是细菌时空分布重要影响因素。异养细菌丰度与叶绿素a和溶解氧含量呈显著正相关，表明浮游植物初级生产过程影响了异养细菌的时空分布。在秋、冬和春3季异养细菌丰度与营养盐水平呈显著负相关，二者关系受浮游植物生物量间接影响。异养细菌时空分布差异取决于环境条件的变化，温度、盐度、叶绿素a和溶解氧含量是影响异养细菌丰度分布的主要因素。 相似文献
14.
《African Journal of Marine Science》2013,35(3-4):479-491
Pigment indices were used to investigate the distribution and composition of phytoplankton in the northern Benguela during the austral spring of 2000, with sampling being conducted on five transect lines between 19°S and 25°S and at other inshore stations on the shelf. Total chlorophyll a concentrations (TChla) at the surface ranged from 18.4mg m?3 at shallow inshore stations to 0.58mg m?3 at offshore localities in deeper water. Phytoplankton communities in the inshore environment were characterised by elevated biomass levels and the dominance of diatoms (high FucDP indices). These diatom populations were associated with cool, higher density, nutrient-rich waters near the coast. Phytoplankton biomass declined with increasing distance offshore and the communities changed to a mixed population where small flagellates were generally dominant (high FlagDP indices). These flagellate communities were associated with warmer, lower density waters. Whereas dinoflagellates (PerDP Index) and prokaryotes (ZeaDP Index) were observed throughout the region, their contribution to the communities was of secondary importance. 相似文献
15.
秦皇岛近岸海域绿藻微观繁殖体的分布以及在绿潮形成中的作用 总被引：2，自引：0，他引：2
2015年以来，秦皇岛近岸海域暴发了绿潮，对北戴河旅游区的环境和生态系统造成了严重影响。绿藻微观繁殖体在绿潮的形成过程中起到重要作用，主要包括孢子、配子、幼苗和营养片段。绿藻微观繁殖体作为绿潮的“种源”，其分布规律可以反映绿潮的“藻源”位置。本研究于2016年4-9月和2017年1月对秦皇岛近岸海域绿藻微观繁殖体的调查，探究了其分布规律以及生物量变化。结果显示，绿藻微观繁殖体主要分布在近岸海域，由近岸向远岸海域逐渐降低。绿藻微观繁殖体的数量在7、8月份最高，在冬季最低。受绿潮影响严重的海域微观繁殖体数量高于其它海域。秦皇岛近岸海域的绿藻微观繁殖体为该海域绿潮的种源，其分布规律表明秦皇岛近岸海域绿潮起源于本地。 相似文献
16.
17.
Waverider buoys were installed in approximately 16 m of water offshore of the Size-well-Dunwich Bank off the East Coast of England and in approximately 11 m of water inshore of it. Minimum water depth over the bank was approximately 4.5 m at mid-tide level. Simultaneous records were obtained for substantial periods between November 1978 and May 1979. These show negligible attenuation for small waves, but as the offshore waveheight increased, the inshore waveheight tended to saturate at an Hs of about 3 m. The form of the relationship between inshore and offshore waveheight is predicted theoretically assuming that high individual waves which cross the bank are limited by breaking. The theoretical curve agrees well with the measured data. The measured saturation level corresponds to a wave breaking when its height is approximately 0.5 the water depth, which is considerably lower than the usual engineering criterion. However, some published tank results also appear to show the same low value. 相似文献
18.
《African Journal of Marine Science》2013,35(1):85-97
In recent years, sardine Sardinops sagax spawning has been recorded inshore off central Namibia. Field observations on eggs and laboratory measurements show that spawning, demonstrated by the distribution of newly spawned eggs, takes place just below the upper mixed layer. The high positive buoyancy of the eggs causes them to ascend rapidly to the surface layer, where they are moved offshore by upwelling-induced offshore transport. However, increased wind-induced mixing also influences the vertical distribution of eggs, causing them to be partly mixed down below the layer moving offshore and into the layer moving inshore. This mechanism acts to retard the transport and offshore loss of eggs from the spawning areas. The vertical distribution of sardine larvae, with highest concentrations deeper than 20 m, indicates active movement out of the layer moving offshore, and this tendency seems to be more pronounced for older larvae. Hence, vertical migration of larvae is an additional factor mitigating their loss from nearshore. Taken together, these features seem to minimize the offshore loss of offspring, particularly in periods of low stock biomass when spawning close to the shore seems to be common. 相似文献
19.
Rita Borges Radhouan Ben-Hamadou M. Alexandra Chícharo Pedro R Emanuel J. Gonalves 《Estuarine, Coastal and Shelf Science》2007,71(3-4):412-428
There have been no previous studies of the composition of nearshore larval fish assemblages along the coast of Portugal. We aimed to describe the composition and horizontal distribution patterns of larval fish assemblages and their temporal dynamics near a rocky reef at depths shallower than 13 m (inshore) and at two miles (3.70 km) from shore (offshore), as well as along transects perpendicular to the shoreline, from the reef to 10 miles offshore (18.52 km). Samples were taken using 5 min sub-surface trawls at the rocky shore of the Arrábida Marine Park (W Portugal). A total of 1021 larvae were collected, belonging to 61 taxa inshore and to 29 taxa offshore. Along transects, 626 larvae of 52 taxa were collected. Most larvae belonged to coastal species associated with rocky reefs. Total larval abundance and diversity were higher from May to July, which is consistent with the spawning activity of adults. Diversity and total larval abundance decreased significantly with increasing distance from shore, both in the inshore/offshore comparison and in the transects, where this decrease was evident at a very small spatial scale (within the first mile from the reef). Species assemblages differed in the pattern of distribution, with most species clearly associated to the extreme nearshore. The distribution patterns obtained were independent of the spawning mode of species. Results are discussed in the light of the possible physical mechanisms that can potentially act at the Arrábida Marine Park to facilitate larvae retention and the role of larval behaviour. 相似文献
20.
We tracked the duration and intensity of the euphausiid spawning season through biweekly sampling along a transect off Newport, OR (latitude 44°40′N) over a six year period from 1996 to 2001. Our sampling consisted of vertical plankton tows, CTD casts, and collection of water for determination of chlorophyll a. Here, we report on data collected from two stations, 5 and 15 nautical miles (9.3 and 27.8 km) offshore. The density of euphausiid eggs in our samples was highly variable spatially and temporally; we saw the most striking differences in egg densities and length of the spawning season, when we compared spawning before and after 1999. This year corresponded to the time when the Pacific Decadal Oscillation switched from warm phase (pre-1999) to cool phase (1999–present). The years 1996 and 1997 were characterized by one large, late summer peak in egg density at our inshore station. 1998, an El Niño year, followed this pattern for our offshore station, but eggs were nearly absent at our inshore station. Starting in 1999, we saw multiple peaks in egg density and found that the spawning season extended from spring through early fall. For example, in spring (March–May) at the inshore station, the abundance of eggs increased from an average of 0.4 m−3 (1996–1998) to 51.3 m−3 (1999–2001), and for summer (July–September), 27.8 m−3 to 132.6 m−3 for the same time period. At the offshore station, egg abundances doubled over the same two time periods: 7 m−3 versus 11 m−3 (spring) and 55 m−3 versus 186 m−3 (summer). Peaks in egg densities were often associated with phytoplankton blooms, but not in a predictable way. Peaks in egg densities often followed cold-water upwelling events, especially at the inshore station. It is not yet clear whether this connection is due to changes in advection or changes in upwelling-induced productivity. 相似文献