海洋生物分类与系统演化实验室知识库

潮间带底栖有孔虫具有很高的生物量，是微小型底栖生物的重要组成部分，在底栖微食物网的物质循环和能量流动中发挥着重要作用。同时由于其种类多、分布广、个体小、生命周期短、对环境变化敏感、大部分具有能在沉积物中长期保存的壳体等特点，使其成为古海洋环境和古气候重建中非常重要的研究载体。
潮间带同时受到陆地、海洋和大气因素的影响，环境复杂多变，且不同区域的底栖有孔虫组合存在很大区别。因此探究潮间带底栖有孔虫群落与环境因子之间的关系对于了解有孔虫对全球环境变化下的响应和适应及其在古环境重建中的应用具有重要的参考价值。
本文以青岛湾潮间带底栖有孔虫为研究对象，结合野外调查与实验生态学的研究方法，探究温度和盐度对其群落丰度、多样性、物种组成、壳体形态等的影响，主要工作包括以下四部分：
1. 温度和盐度对Ammonia aomoriensis存活和生长的影响
以青岛湾潮间带常见优势种Ammonia aomoriensis为研究对象，选取大小相近的144枚活体在三个温度梯度 (6, 12和18°C) 和四个盐度梯度 (20, 25, 30和35 psu) 完全交互条件下进行分组培养实验。实验周期共28天，每两天观察其存活状态、记录房室数目、测量长径和短径。
研究表明，相比于盐度，温度对A. aomoriensis存活、生长和形态变化影响更显著。在实验设计的温度和盐度范围内，低温对其存活具有明显的抑制作用，6°C时虫体出现死亡早且最终存活率低，而盐度变化对其存活无明显影响；温度升高对A. aomoriensis生长具有显著的促进作用，而盐度对广盐性有孔虫A. aomoriensis生长的影响不显著。实验设计中最适宜的18°C条件下，两圈房室以上的A. aomoriensis形成一个新房室平均需要3.5–7天，长径和短径的生长速率分别为0.7–1.3 μm/d、1.2–1.9 μm/d。温度升高时，A. aomoriensis长宽比减小，其壳体趋向变圆，推测其可以作为指示温度变化的指标。此外，温度和盐度对A. aomoriensis的交互作用在长径的生长中显著，在短径的生长和长宽比中不显著。
2. 温度对青岛湾潮间带底栖有孔虫群落的影响
在五个温度梯度 (6, 12, 18, 24和30°C) 下对采自青岛湾潮间带沉积物的底栖有孔虫群落进行为期100天的培养实验，每个温度条件设置4个重复。该部分实验总共获得并分析了6771枚活体底栖有孔虫标本，研究了有孔虫群落 (丰度, 物种丰富度, Margalef指数, Shannon-Wiener多样性和Pielou均匀度)、物种组成和优势种壳体形态对不同温度的响应。
结果表明，培养实验结束后不同温度下的有孔虫群落丰度为75–131枚/g干重沉积物，6°C时丰度最低，18°C时丰度最高。温度对大多数有孔虫群落参数影响显著，当温度升高时，所有群落参数先升高后降低，并在18或24°C时出现峰值，且随着温度的升高，活体有孔虫在总体群落中的比例显著降低。此外，有孔虫的物种组成也发生了明显变化，温度升高会时瓷质壳类群的比例明显升高，而玻璃质壳类群比例明显降低。优势种 (包括Ammonia aomoriensis, A. tepida和A. beccarii) 对温度有不同的耐受性和偏好，其中A. aomoriensis对温度变化的耐受性最高，且更喜欢低温 (6–12°C)，A. tepida更喜好高温 (18–30°C)，而A. beccarii则更适应中等温度范围 (12–18°C)。优势种的壳体形态研究表明，其大小、长宽比和壳体畸形对温度变化做出响应。温度升高时A. beccarii壳体变大，且三种优势种的长宽比显著降低、壳体畸形率升高。该研究表明，温度升高不仅可以显著改变潮间带有孔虫的群落结构，还可以改变潮间带有孔虫的壳体形态。
3. 盐度对青岛湾潮间带底栖有孔虫群落的影响
为探究盐度变化对有孔虫的影响，作者采集青岛湾潮间带有孔虫群落，并在实验室内6个盐度梯度 (17, 22, 27, 32, 37和42 psu) 下培养100天，每个盐度条件下设置四个重复组。该部分实验中共获得并分析了10324枚有孔虫标本，经鉴定共有24种，其中7471枚为活体标本，1853枚为死亡标本。
结果表明，盐度对有孔虫群落多样性参数 (包括物种数, Margalef指数, Shannon-Wiener指数和Fisher's α) 有显著影响，但对丰度的影响不显著。盐度为32 psu时有孔虫群落多样性最高，这一盐度与野外条件一致。而盐度自此升高或降低时有孔虫多样性均显著降低。优势种Quinqueloculina seminula (瓷质壳优势种) 的比例与盐度正相关，而玻璃质壳类群的比例与盐度负相关。
同时，研究中发现了一个含有三种广盐性优势物种 (A. aomoriensis, Cribrononion gnythosuturatum和A. tepida) 的有孔虫组合，对盐度变化表现出极强的适应能力。当盐度自32 psu升高或降低时，这三种广盐性优势种表现出了较强的耐受性，其丰度和比例均没有显著下降。尤其是A. aomoriensis，其比例在盐度升高或降低时明显升高。这些结果表明，当盐度从正常条件升高或降低时，对盐度变化敏感的有孔虫类群衰退而造成多样性降低，但对盐度变化耐受力强的优势种能迅速占据空余的生态位，使有孔虫群落保持较高的总体丰度。
作者同时研究了10173枚壳体较为完整的有孔虫壳体大小和畸形率。结果显示有孔虫群落的壳体大小与盐度呈显著负相关，推测这与有孔虫在高盐环境下会消耗更多能量用来平衡渗透压有关。此外当盐度高于或低于野外条件时，有孔虫壳体畸形率明显升高。
4. 青岛湾潮间带底栖有孔虫群落的季节性变化与环境间的关系
作者在2017年1月至2018年1月期间对青岛湾低潮带表层沉积物中的底栖有孔虫进行了连续13个月的调查，分析底栖有孔虫丰度、群落参数、物种组成和壳体形态，探究其与温度、盐度和pH变化之间的关系。
结果表明，青岛湾有孔虫群落的丰度、群落参数、物种组成和壳体畸形率均呈现出明显的季节性变化，这与环境因子的季节性变化有关，且温度的影响更高。该区域的底栖有孔虫群落在较低的温度、盐度和pH环境中具有更高的多样性。这三项环境因子升高时，有孔虫多样性降低，但同时以Quinqueloculina seminula和Ammonia aomoriensis为代表的机会物种迅速增多，使有孔虫的群落丰度升高。
不同壳质类群和优势种的有孔虫对环境变化的响应存在明显区别，以Quinqueloculina seminula为代表的瓷质壳类群和以Triloculina inflata为代表的胶结质类群更偏好高温环境，而多数玻璃质壳类群有孔虫优势种对温度和盐度的变化较为不敏感。对于温度、盐度和pH等环境因素剧烈的季节性变化，中国海域特有种Cribrononion gnythosuturatum表现出了出色的适应能力，并且相较于五年前其丰度和比例均有显著升高。
综合以上四个部分研究，结果表明温度和盐度的变化对有孔虫群落多样性、物种组成和壳体形态影响显著。在一定范围内的温度升高会促进有孔虫壳体生长，使有孔虫群落多样性和丰度升高，并呈现玻璃质壳类群降低、瓷质壳类群升高的变化趋势。同时随着温度升高，有孔虫壳体趋向变大变圆，壳体畸形率升高。当盐度由野外正常海水盐度值升高或者降低时，群落多样性显著降低，壳体畸形率升高，而丰度变化不明显。同时随着盐度的升高，有孔虫壳体趋向变小。不同物种对温度和盐度的偏好性存在明显差异。机会物种对极端条件具有出色适应能力，其中包括以Quinqueloculina seminula为代表的高温高盐种、以Ammonia tepida为代表的高温广盐种、以及以Ammonia aomoriensis和Cribrononion gnythosuturatum为代表的广温广盐种。当温度和盐度变化时，这些机会物种会迅速生长和增殖，占据空出来的生态位，使整个有孔虫群落维持较高的丰度。这同时是相较于数年前的调查结果，青岛湾潮间带有孔虫群落发生较为明显变化的原因。
 

Intertidal benthic foraminifera are the important component of microbenthos with high biomass and play an important role in the material circulation and energy flow of benthic microbial food web. Simultaneously, it is a very important carrier in palaeoenvironment and paleoclimate reconstruction of marine studies due to its variety, wide distribution, small size, short life cycle, sensitive responses to environmental changes, and excellent preservation potential in sediment.
In this paper, we studied the benthic foraminifera from the intertidal zone of Qingdao Bay with combined research techniques of field study and laboratory culture experiment. Our purpose of this study was to explore the responses of intertidal benthic foraminifera to important environmental factors, temperature and salinity. The main four parts of this study were listed as follows.
1. Effects of temperature and salinity on the growth and survive of Ammonia aomoriensis
Living specimens of Ammonia aomoriensis which was common and dominant in the Qingdao intertidal flat were cultured under a fully crossed experiment involving three temperatures (6, 12and 18°C) and four salinities (20, 25, 30, 35 psu) for 28 days. 144 specimens in total and 12 specimens for each treatment were cultured individually. We assessed the response of survival, growth and morphological change of A. aomoriensis to temperature and salinity changes by recording the survive, major/minor axis length, and chamber numbers of each specimens respectively every two days. The results showed that the survive of A. aomoriensis responding to temperature obviously, and death occurred earlier and more at 6°C. No significant relationship was observed between survive and salinity. Growth was positively correlated to the temperature while not significantly correlated with salinity. At 18°C which was optimum for A. aomoriensis in this research, every chamber growth took about 3.5–7 days. The growth rates of major or minor axis length were about 0.7–1.3 or 1.2–1.9 μm/day. In addition, A. aomoriensis became more rounded when temperature increasing, so we speculated that the length/width ratio could be used as an indicator of temperature. Interaction between temperature and salinity was significant in the growth of major axis for A. aomoriensis, but not significant in the growth of minor axis and length/width ratio. Compared to salinity, our study indicated that temperature has more significant effects on the survival, growth and morphological change of A. aomoriensis.
2. Laboratorial cultured-based impacts of temperature on intertidal foraminiferal communities
Benthic foraminiferal communities from Qingdao intertidal sediments were cultured at five temperatures (6, 12, 18, 24, and 30°C) under a laboratorial microcosmic condition. The culturing experiment was last for 100 days and four replicates were set up in each temperature treatment. The responses of foraminiferal community parameters (abundance, species richness, Margalef index, Shannon-Wiener diversity, and Pielou's evenness) and species composition to temperature were studied. In total, 6771 live (stained) specimens of benthic foraminifera were obtained. Foraminiferal community abundance after culture varied from 75 to 131 individuals/g dry sediment, occurring at 6°C and 18°C, respectively. With rising temperature, most the community parameters increased until 18°C or 24°C but declined when temperature continuously increase. The proportion of live foraminifera in total assemblages decreased significantly with temperature increasing. In addition, species composition was also significantly altered. Temperature has a significantly positive effect on the proportion of porcelaneous taxa, while negative on hyaline type. The dominant species (including Ammonia aomoriensis, A. tepida, and A. beccarii) showed different optimum temperature limits, i.e., A. aomoriensis showed a broader temperature tolerance and a preferring of lower temperature (6–12°C), while A. tepida preferred higher temperature (18–30°C), and A. beccarii had an intermediate range (12–18°C). Results of morphometric study indicated that the major and minor axes of A. beccarii were significantly increased in higher temperature. In addition, the length/width ratio of three dominant species were significantly reduced and the abnormal rates enhanced with increasing temperature. Our study indicated that temperature rising could significantly alter the community structure and chamber morphology of intertidal foraminifera. 
3.Responses of intertidal benthic foraminiferal assemblages to salinity changes in a laboratory culture experiment
Benthic foraminifera communities from Qingdao intertidal sediments were cultured at six salinity gradients (17, 22, 27, 32, 37, and 42 psu) with four replicates under laboratorial microcosmic conditions for 100 days. In total, 10324 (7471 live and 1853 dead) foraminiferal specimens belonging to 24 species were obtained and analyzed respectively. Salinity showed significant effects on foraminiferal community diversity parameters (including species number, Margalef index, Shannon-Wiener index, and Fisher's alpha), but not on abundance. The foraminiferal community diversity showed a maximum at 32 psu which was consistent with field condition and declined obviously with salinity increasing or decreasing from that. In this study, we found an euryhaline foraminiferal assemblage dominant by salinity-tolerant Ammonia aomoriensis, Cribrononion gnythosuturatum, and A. tepida. The abundance and proportion of these three dominant species did not show significant decline when salinity altered. Especially for A. aomoriensis, the proportion showed an obvious increase in brackish or hypersaline waters. Simultaneously, salinity has a significant positive effect on the proportion of Quinqueloculina seminula, while negative on hyaline taxa. Test size of 10,173 foraminiferal specimens were measured. Significant negative correlations were found between the test size of foraminiferal community and salinity. And more abnormal specimens appeared in foraminiferal assemblages when salinity altered from field conditions. Our study indicated that when salinity altered from normal conditions, species diversity decreased with the decline of salinity-sensitive population, and foraminiferal assemblages kept high abundance because salinity-tolerant species would fill the unoccupied ecological niche. The growth of foraminifera reduced in hypersaline waters. This work revealed the high adaptability of benthic foraminiferal assemblages to the various and changeable intertidal environment.
4. Seasonal variations of benthic foraminifera in a Qingdao intertidal zone and correlations with temperature, salinity and pH
Benthic foraminifera in a Qingdao intertidal zone were investigated thirteen times monthly from January 2017 to January 2018. We analyzed of seasonal variations of abundance, diversity, species composition and test abnormality of foraminiferal assemblages. The results showed that the abundance, community parameters, species composition and test abnormal rate of the intertidal benthic foraminifera community in Qingdao Bay showed obvious seasonal changes, which were related to the seasonal changes of temperature, salinity and pH, and the effects of temperature were higher than salinity and pH. The benthic foraminifera community in this region showed higher diversity when surrounding was characterized lower temperature, salinity and pH. When temperature, salinity and pH increasing, the diversity of foraminifera reduced but foraminiferal abundance increased simultaneously. Because the opportunistic species, represented by Quinqueloculina seminula and Ammonia aomoriensis, would grow and multiply rapidly. We also found the obvious different response of foraminifera with different shell types and different dominant species to environmental changes. The porcelaneous taxa represented by Quinqueloculina seminula and the agglutinated taxa represented by Triloculina inflata preferred high temperature conditions, while most hyaline benthic dominant species were less sensitive to changes in temperature and salinity. Cribrononion gnythosuturatum, a common foraminiferal species in the Chinese seas, has shown remarkable adaptability of dramatic seasonal changes of environment factors, such as temperature and salinity. And it has shown higher abundance and proportion in the Qingdao intertidal flats compared with that of five years ago.
Combined with the above four parts, the results show that changes in temperature and salinity have significant effects on foraminifera community diversity, species composition and shell morphology. An increase in temperature within a certain range will promote the growth of foraminifera individuals, increase the diversity and abundance of foraminifera communities, and enhance the hyaline group. When temperature increasing, foraminiferal tests tend to become larger and round, and more test become deformities. When the salinity increased or decreased from the field seawater salinity value, the community diversity decreased significantly, the shell deformity rate increased, and the abundance did not change significantly. As the salinity increases, the foraminifera shell tends to become smaller. The preference of different foraminiferal species for temperature and salinity is obviously different. Opportunity species have excellent adaptability to extreme conditions: Quinqueloculina seminula prefers high-temperature and high-salt conditions, Ammonia tepida prefers high-temperature and adapts euryhaline conditions, Ammonia aomoriensis and Cribrononion gnythosuturatum show excellent adaptability to changes of temperate and salinity in a wide range. When the temperature or salinity changes, these opportunistic foraminiferal species will grow and multiply rapidly, occupying the vacated ecological niche. Thus, the foraminifera community abundance maintains high. This is also the reason why the foraminifera community in the intertidal zone of Qingdao Bay has changed significantly compared with the results of field study several years ago.