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11.
Seasonal dynamics and feeding of scyphomedusae, Aurelia aurita, were investigated monthly from 1999 to 2002 in relation to environmental conditions in Tapong Bay, a eutrophic tropical lagoon in southwestern Taiwan. Medusae appeared throughout the year but exhibited seasonal dynamics that were correlated with hydrographic features in the bay. Most ephyrae of A. aurita occurred mainly in the lower flushed and eutrophic inner bay, and during the cold, dry season between November and February. They grew to young medusae with a maximum abundance in spring (March–May), but their numbers abruptly decreased during the warm and rainy summer season in June–September. The remaining medusae then grew rapidly to a maximal size of 29 cm. Mature females spawned in the following autumn when precipitation decreased but zooplankton food was still abundant. These mature individuals decreased in size after spawning and in winter. Gut content analysis revealed that A. aurita fed mainly on copepods and copepod nauplii and less on bivalve larvae and fish eggs. Prey selectivity indices indicated that larger medusae selected positively for copepods while small size medusae preferred copepod nauplii. The overall feeding effect of A. aurita on the standing stock of zooplankton was significant (27%) in the bay. Our results suggest that tidal flow and dense oyster culture pens were the two most important factors influencing the spatial distribution pattern of A. aurita in the bay, while precipitation affected the population abundance seasonally; decreasing water temperature coincided with the mass release of ephyra in late autumn and winter. 相似文献
12.
自20世纪90年代末起,沙海蜇频繁暴发于东亚海域,特别是8、9月份为黄海沙海蜇生物量的高峰期/大量暴发期。研究沙海蜇的大量出现对所在生态系统的影响十分必要,最直接的影响表现在对饵料生物浮游动物的影响。本文研究了黄海2006和2007年8、9月份沙海蜇的呼吸率、摄食率,估算了沙海蜇的食物需求量及其在黄海的分布格局,获得了其每天对中、大型浮游动物现存量及生产力的潜在摄食压力。结果表明沙海蜇的食物需求量的分布格局与其生物量的分布格局一致。在沙海蜇的捕获率为最大时,2006年9月上旬沙海蜇的摄食率为47.84(0.7—215.05)mg C/(m2d)。假设中、大型浮游动物都可以作为沙海蜇的摄食对象,那么每天对中、大型浮游动物现存量及生产力的摄食压力平均分别为6.4%(0.09%—28.79%)和76.61%(1.12%—344.28%)。2006年9月下旬及2007年8月沙海蜇的食物需求比2009年9月上旬有所降低。因此,沙海蜇在暴发期间对中、大型浮游动物潜在的消耗非常大,甚至是毁灭性的。尤其是沙海蜇在高生物量站位对浮游动物的食物需求非常高,沙海蜇对浮游动物的摄食压力远超过了浮游动物本身的生产力(大于100%),这时的浮游动物远远不能满足沙海蜇的食物需求。本文的研究结果为探讨沙海蜇暴发对黄海浮游生态系统的影响程度提供了基础资料。 相似文献
13.
Molecular data have shown that jellyfishes are more geographically restricted and evolutionarily divergent than previously thought. We examined genetic variation and divergence within the meroplanktonic barrel jellyfish Rhizostoma pulmo in the Mediterranean Sea; specific sampling areas were the northern Adriatic, western Mediterranean and Tunisian coast. A total of 19 sampling sites and 68 sequences of the mtDNA cytochrome c oxidase subunit I (COI) gene were used. Of the 68 COI sequences, 45 were newly collected specimens which originated from nine sampling sites along the Tunisian coast. A total of 24 haplotypes were obtained and the specimens sampled were characterised by relatively high levels of haplotype diversity (h = 0.866) and low levels of nucleotide diversity (π = 0.004). Haplotype network analysis showed the presence of three distinct phylogenetic lineages (populations), with separate geographic ranges in the northern Adriatic, western Mediterranean and Tunisian coast. The observed genetic differentiation between these three lineages was supported by the presence of significant genetic differentiation between the 19 populations (FST = 0.757, p < 0.001). The high level of genetic differentiation detected in the barrel jellyfish investigated could be attributed to either intrinsic and/or extrinsic barriers to genetic exchange between different populations that may have adapted to different environmental conditions. 相似文献
14.
制备了基于八乙基卟啉铂和香豆素的光强比率测量传感膜,结合3CCD相机构建了基于比率测量法的两维溶解氧观测系统,通过实验验证了该系统在沉积物-水界面微结构的溶解氧的时空动态变化监测的可行性。基于实验室模拟观测装置对海蜇消亡过程中沉积物-海水溶解氧的变化特征进行了观测。观测结果表明在置入水母组织的第16h后,水母分解使得沉积物-水界面的溶解氧开始下降,在2~3d内会导致沉积物-水界面空间的海水溶解氧发生剧烈变化,在沉积物-海水界面附近海水形成严重缺氧区。第1天内,沉积物-海水界面的溶解氧消耗速率为0.2mg·L-1·h-1,第2天溶解氧的消耗速率为0.04mg·L-1·h-1。在近海底的水体空间内,第1天的溶解氧消耗速率为0.28mg·L-1·h-1,第2天为0.14mg·L-1·h-1,第3天为0.13mg·L-1·h-1,表明水母消亡过程中的溶解氧消耗呈动态分布。实验证明水母在消亡过程中的3~4d内可在沉积物-海水界面附近形成一个贫氧区,水母消亡过程改变了海底区域的溶解氧分布体系,将对海底生态环境产生较大影响。 相似文献
15.
为了探究不同种类水母对浮游食物网的摄食影响,采用碳氮稳定同位素和脂肪酸标记法,研究分析了渤海红沿河海域常见的4种小型水母(伞径直径5 cm:卡玛拉水母Malagazzia carolinae、球形侧腕水母Pleurobrachia globosa、帽铃水母Tiaricodon coeruleus、半球美螅水母Clytia hemisphaerica和3种大型水母(伞径10—200cm:沙海蜇Nemopilema nomurai、海月水母Aurelia aurita)和白色霞水母Cyanea nozakii)的食物组成。结果表明,不同种类水母的食物组成存在差异。其中卡玛拉水母、球形侧腕水母、帽铃水母、半球美螅水母和白色霞水母均偏肉食食性,食物组成中动物性食物所占比例更高,高于海月水母与沙海蜇。在食物粒径谱上,帽铃水母和半球美螅水母较大粒径的食物比例均高于小粒径的悬浮有机物(POM)比例。卡玛拉水母和球形侧腕水母各个粒径食物比例接近。大型水母中,白色霞水母的食物中大粒径的浮游动物的比例高于海月水母,更高于沙海蜇。由此看来,小型水母和大型的白色霞水母的暴发会直接影响大中型浮游动物数量,海月水母的暴发对不同大小的浮游生物均会产生一定的影响。而沙海蜇的暴发会大量摄食1 mm的小型浮游生物和POM,对大中型浮游动物以及更高营养层生物(鱼类等)的影响可能是通过蜇伤以及饵料竞争导致的。因此,不同种类水母暴发对浮游生物的影响存在差异。本研究从摄食角度初步探究了水母对海洋生态系统物质循环和能量流动的影响,为水母暴发的灾害防治提供了数据支持。 相似文献
16.
本研究调查了秋季红沿河核电站海域镭、氡同位素的活度水平及分布情况，结合镭同位素表观年龄模型计算该海域的水体年龄，进而得出研究区域的水体运移方向，初步探讨了水母丰度分布与水体运移的相关关系。得到结论如下:(1)红沿河核电站海域表层水体中224Ra、226Ra及222Rn的活度水平分别为2.9～62.4 dpm/(100 L)，11.9～57.4 dpm/(100 L)及0.1～1.3 dpm/L，镭同位素活度呈现出近岸高、远岸低的分布趋势，氡同位素的分布则更大程度上受水温控制；(2)通过224Ra/226Ra表观年龄模型计算得出红沿河海域表层水体年龄范围介于0～16 d，平均年龄(10.9±3.6) d，水体主体流向为北偏东方向，流速为7.2 cm/s；(3)水母丰度分布与水体流向呈现出较为一致的对应关系，在主体流向方向上，水体年龄较大的海域水母丰度最高。 相似文献
17.
2019年5月,利用渔业底拖网,对我国黄海以及东海北部海域进行了全面系统的大型水母调查,分析了大型水母的种类组成、伞径大小和生物量以及与温度、盐度的关系。结果表明,本次调查主要捕获到沙海蛰、霞水母、洋须水母、多管水母四种大型水母,沙海蛰生物量最高,多管水母分布范围最广、数量最大。沙海蛰集中分布在调查海域南部,各海域伞径差异显著,在黄东海交界海域采集到幼水母体(10cm),生物量高值区出现在东海北部离岸海域,可达6422.16kg/km2;白色霞水母集中分布在东海北部,在近岸海域采集到幼水母体(6—7cm),生物量高值区位于离岸海域,可达7417.49kg/km2;洋须水母集中分布在黄海水深较深海域,北部海域个体较大,在黄海中部、南部交界处采集到幼水母体(10cm),生物量较低,高值区出现在黄海中部与南部,可达449.94kg/km2;多管水母分布范围较广,东海北部海域个体伞径较大,在山东半岛东部发现幼水母体(5cm),生物量高值区出现在黄海中部近岸海域,可达4901.42kg/km2。对比文献资料,发现整个调查海域,大型水母总体生物量比2015年同期有所增加。本文为研究该海域大型水母的年际变化规律提供数据基础。 相似文献
18.
Collapse of zooplankton stocks during Liriope tetraphylla (Hydromedusa) blooms and dense mucilaginous aggregations in a thermohaline stratified basin 
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下载免费PDF全文 Izzet Noyan Yilmaz 《Marine Ecology》2015,36(3):595-610
A growing number of studies report an increase in jellyfish populations worldwide that may have consequences for marine planktonic food web dynamics. The principal objective of this study was to understand the changes in a zooplankton community during blooms of Liriope tetraphylla and subsequent mucilage events in the Sea of Marmara, a small highly stratified transitional basin between the Black and Aegean Seas. Liriope blooms observed in 2006 and 2007 reached a maximum abundance of 2978 ind.·m?3, following the species' first observation in 2005. Jellyfish species are known to play a key guild role by restructuring plankton communities and in the Sea of Marmara Liriope caused a temporal regime shift from a crustacean‐ to a jellyfish‐controlled system. A rapid decline in abundance of most important zooplankton species followed the Liriope increase, together with a drastic shift in community structure. The dominant summer–autumn species Penilia avirostris (Cladocera) vanished in the autumn of 2006 and was diminished ~30‐fold in 2007 when compared with years without Liriope. The decline in zooplankton and the devastating effects of mucilage on pelagic ecosystem and socio‐economics through restricting commercial fisheries implied sensitivity of the already perturbed Marmara ecosystem to changes in predator densities and environmental stability. 相似文献
19.
通过对山东省靖海湾海蜇养殖港塭定期采样,采用稀释法研究该海蜇养殖港塭水体中浮游植物的生长率、微型浮游动物对浮游植物的摄食率、摄食压力以及微型浮游动物的生产力。研究结果表明,海蜇养殖港塭微型浮游动物组成比较简单,海蜇养殖期间微型浮游动物丰度低于海蜇捕捞结束期。其中,海蜇养殖期间微型浮游动物的优势种为根状拟铃虫(Tintinnopsis radix),为600~2 600 ind/L,而海蜇捕捞结束后优势种为根状拟铃虫、诺氏麻铃虫(Leprotintinnus nordquisti)和运动类铃虫(Codonellopsis mobilis),丰度分别为3 000~6 000、1 500~3 0001、500~3 000 ind/L。研究期间,该港塭浮游植物生长率为0.05~1.03 d-1。微型浮游动物的摄食率为0.24~2.37 d-1,对浮游植物现存量的摄食压力为21.10%~90.61%,对潜在初级生产力的摄食压力为77.08%~583.68%,而微型浮游动物的次级生产力占初级生产力的22.92%~76.92%。本研究表明微型浮游动物在海蜇养殖港塭生态系统物质和能量流动中起着重要作用。 相似文献
20.
The impact of the scyphomedusa Aurelia sp. on planktonic assemblages was experimentally studied in enclosures incubated in situ in the sea lake of Mljet Island (Big Lake, Southern Adriatic), where jellyfish are present throughout the year. In situ feeding experiments using plankton at natural densities indicated a reduction in abundance for small calanoid and cyclopoid copepods, copepodites, nauplii and ciliates in the presence of Aurelia sp. In addition to direct predatory pressure, Aurelia sp. exerted an indirect cascading effect on autotrophic and heterotrophic microbial plankton. Phytoplankton biomass increases of up to 0.5 μg C·l?1·h?1 were mainly related to 19′‐hexanoyloxyfucoxanthin‐ and 19′‐butanoyloxyfucoxanthin‐containing phytoplankton. Bacterial production was about twice as high in the presence of Aurelia sp. and biomass was also consistently higher. It appears that the top‐down effect of predation along with material release by Aurelia sp. results in increases in microbial biomass and production. 相似文献