Temporal variability of disturbances: is this important for diversity and structure of marine fouling assemblages?

Natural communities are constantly changing due to a variety of interacting external processes and the temporal occurrence and intensity of these processes can have important implications for the diversity and structure of marine sessile assemblages. In this study, we investigated the effects of temporal variation in a disturbance regime, as well as the specific timing of events within different regimes, on the composition and diversity of marine subtidal fouling assemblages. We did this in a multi‐factorial experiment using artificial settlement tiles deployed at two sites on the North East coast of England. We found that although there were significant effects of disturbances on the composition of assemblages, there were no effects of either the variation in the disturbance regime or the specific timing of events on the diversity or assemblage composition at either site. In contrast to recent implications we conclude that in marine fouling assemblages, the variability in disturbance regimes (as a driving force) is unimportant, while disturbance itself is an important force for structuring robust ecosystems.     

Environmental influences on temporal patterns of settlement in two littoral labrid fishes in the Mediterranean Sea

Correlations between daily fish settlement and environmental and physical parameters were examined during two consecutive years in two labrid species (Symphodus roissali and Symphodus ocellatus) in the NW Mediterranean Sea. Both these species have a short planktonic larval duration (12±0.3 and 9±0.4 days, respectively) and limited offshore larval dispersal. Time-series analysis was used to compare the daily settlement patterns with various environmental variables, and non-linear generalized additive models (GAM) were used to examine the relationship between environmental conditions averaged over larval period and daily settlement patterns. Settlement was not uniform and took place as pulses of different length. Although the analyses detected a few significant correlations between day-to-day patterns in environmental variables and settlement (e.g. solar radiation, atmospheric pressure, daytime or nocturnal wind components), these were not consistent among years. In S. ocellatus, however, wind components (daytime or nighttime) explained part of the variance in settlement intensity. The correlations (GAM outputs) observed between settlement patterns and environmental variables (averaged during the whole planktonic period) suggest that calm weather during the planktonic period usually increases settlement success.     

Species assemblage and recruitment patterns of echinoderms on shallow rocky reefs in central New Zealand

ABSTRACT

Echinoderms play important ecological roles in the benthic community, but the processes that regulate their distribution are still poorly understood. The aim of this study was to describe the community structure in the shallow rocky reefs of the Wellington region of central New Zealand. Five sites from a harbour and an open coast were surveyed for adult echinoderm density and habitat composition. Additionally, artificial collectors were deployed to assess recruitment patterns. Five taxa were responsible for the assemblage variation within sites and their abundance was highly correlated with habitat composition. Patiriella regularis was highly abundant in all sites, while Coscinasterias muricata and Evechinus chloroticus were dominant in the Harbour. Echinoderm settlement showed interannual variations, as well as differences between locations. There was a significant pulse of C. muricata settlers, while ophiuroids were present in lower numbers but constantly during the studied period. E. chloroticus settlement was sporadic and the absence of a juvenile cohort in the open coast sites suggests that recruitment might not occur for up to 4 years. The present study provides insights on the echinoderm assemblage in the shallow rocky reefs of the Wellington region and contributes to a better understanding of recruitment patterns shaping population structure.     

冠瘤海鞘幼体附着和变态的离子控制

研究了人工海水中三种金属离子K+,Mg2+和Ca2+分别在不同浓度下对冠瘤海鞘(Styelaca nopusSavigny)幼体附着和变态的影响,同时采用K+通道阻滞剂TEA检验其可兴奋细胞膜上的K+通道特性,对冠瘤海鞘幼体附着和变态的离子控制机制进行初步探讨,结果表明:K+的浓度为20~40mmol/dm3时诱导幼体附着和变态的效果最佳,低于45 mmol/dm3和高于80mmol/dm3的K+浓度都表现出抑制效果;Mg2+浓度在0~32 mmol/dm3时显著促进幼体附着和变态,达88mmol/dm3时起抑制作用;在人工海水中无论添加或减少Ca2+,均有效抑制幼体变态.TEA不能阻抑增加K+的诱导作用,这表明冠瘤海鞘幼体可兴奋细胞膜上的K+通道对外部TEA不敏感.另外,人工海水中缺乏K+或Ca2+或K+浓度达80mmol/dm3都会对冠瘤海鞘幼体产生毒害作用.     

地铁盾构线路穿越运营隧道的沉降影响

针对地铁修建过程中穿越运营地铁线路时需动态监测隧道的安全状态问题,该文以深圳地铁某区间盾构隧道穿越过程为例,利用测量机器人,以0.5~2h/次的频率对监测点进行全程观测。断面数据分析表明:在下穿过程中,上下隧道间距在1.823和6.028m之间存在某个临界距离,当小于这个临界值时,穿越时要注意隆起对既有隧道,尤其是对道床轨面沉降差的影响;盾构机从进到出1号线左、右线隧道引起的沉降量各占相应穿越线路总沉降量的50%~86%,盾构穿越已有隧道的过程应增大观测频率,及时进行二次注浆;总的监测断面布设数量不受上下隧道间距的影响,距离上、下隧道正交断面10m外的相邻断面只需布设两个观察点。从而实现最优点位布设密度和监测频率,节约施工成本。     

建筑物沉降监测方案设计及数据处理

通过对某学校图书馆变形监测,阐述了变形监测的方法和意义。主要包括变形监测网的布设、测量方法的选取、监测数据的处理,以及建筑物的沉降分析。然后在EXCEL软件上绘制建筑物的沉降趋势图,并且预测分析平均观测量和每个点位。     

外来蓝领农民工城市定居意愿影响因素——以广东省东莞市为例

以外来蓝领(即工厂、企业中的外来产业工人)高度集聚的广东省东莞市为例,基于814份有效调查问卷数据,采用Logistic模型和描述性统计分析,结合预假设及反馈验证,揭示了外来蓝领工人城市定居意愿的影响因素。回归结果显示:工资收入、产权住房、工作时间、是否已婚、生活满意度等经济、环境、家庭和心理因素均对外来民工的定居意愿产生显著的影响;而年龄、性别、户口性质、受教育水平等因素未通过显著性检验,既反映现有文献中存在的争议,也反馈了当地的真实情况。相关统计分析发现,拥有资格证书、本地户口及其赋予的福利权利、良好的居住环境也有助于提高外来蓝领农民工的定居意愿。最后,讨论了提高外来蓝领工人城市定居意愿的政策启示。     

浙江省人居环境气候适宜度概率分布分析

利用浙江省43年的气候资料,采用人体舒适度指数对浙江人居环境气候适宜度进行分析。结果表明:浙江省出现极热和极冷的概率极小,人居气候适宜度等级为Ⅰ(很冷,极不舒适)、Ⅷ级(热,很不舒适)的概率为0.07%和0.78%,出现Ⅸ级(很热,极不舒适)的概率基本为零;适宜度等级为Ⅳ—Ⅵ级(较舒适至舒适)的天气出现概率为55.0%,其中Ⅴ级(舒适)出现的概率最大,为33.1%。5月和10月是浙江人居环境气候适宜度最好的时段,其中Ⅴ级(舒适)天气出现概率的平均值超过99%;1月是浙江人居环境气候适宜度最低的月份;7月、8月中气候适宜度为Ⅶ级,即暖热不舒适的天气出现概率平均值分别为62.3%和42.8%,出现概率呈现沿海低于内陆,浙南低于浙北,浙中高、浙北浙南低的总体趋势。     

环渤海地区城市人居环境质量评估及影响因素

城市人居环境是城市居民生活质量和满意度的重要内容。本文以环渤海地区44个城市为例,从人居硬环境和软环境两方面评价人居环境指数,运用描述统计和GIS制图方法,分析环渤海地区城市人居环境综合质量空间差异及其影响因素,研究发现：①人居环境综合指数存在显著空间差异,沿海城市的人居环境质量明显高于内陆城市;在省级行政单元中,辽宁省人居环境综合指数最高,天津最低。②环渤海地区城市人居环境指数与经济发展水平和城镇化水平不存在显著的正相关关系,但与人口规模存在显著的负相关关系,表明仅提升经济发展水平和城市化率并不能提升城市人居环境质量,但合理控制城市人口规模则可有助于提升城市人居环境质量。     

Barnacle Larvae and their Settlement in Genoa Harbour (North Tyrrhenian Sea)

Abstract. Density of barnacle larvae in plankton and settlement on atoxic plane surfaces have been compared at one station of Genoa harbour over sixteen months.
There were two periods of larval emission, during summer and autumn, with a slight one during winter. Barnacle settlement varied according to sea temperature, the amount of larvae and competition for the substratum.