Variability in growth,development and reproduction of the non-native seaweed Sargassum muticum (Phaeophyceae) on the Irish west coast

This study compared seasonal growth, development and reproduction of the invasive brown macroalga Sargassum muticum in habitats with different wave exposure on the Irish west coast. Three field sites with different degrees of wave exposure were chosen for monthly observations to reflect different habitats that were characteristic of the Irish west coast. Growth and receptacle development differed considerably between sites. Growth and receptacle development was lower at the most sheltered site. Here, S. muticum showed signs of early fragmentation in April/May during the two years of investigation (2007 and 2008), whilst the population at an exposed site developed normally and plants grew to a maximum average length of 163 cm by July, with the onset of fragmentation in August. Sargassum muticum in a tide pool exhibited a similar seasonal growth cycle as plants at the exposed open shore site. Overall growth however was stunted, with plants reaching a maximum length of only 30–40 cm in July. Receptacle development was also inhibited at the sheltered site, with a maximum of only 10% of plants found to be fertile during spring and summer 2008, while plants at the exposed site and the tide pool exhibited 100% plant fertility by August. An extensive occurrence of the native epiphyte Pylaiella littoralis on S. muticum was noticed during field sampling at the sheltered study site which may have contributed to inhibited development of S. muticum observed in this area.     

湛江湾真光层深度与初级生产力的时空变化及其影响因素

基于2016−2017年4个季节航次数据,分析了湛江湾真光层深度与初级生产力的时空变化特征及其影响因素。结果表明,湛江湾真光层深度平均值为（6.95±3.17）m,空间变化比季节变化明显,K_d(PAR)与浊度存在显著的正相关关系,建立的线性回归模型R²为0.73（p<0.01）,表明悬浮颗粒物对湛江湾真光层深度的影响占主导地位。利用VGPM模型得到初级生产力（以碳计）的平均值为（639.53±427.95）mg/(m²·d),其时空特征与真光层深度基本保持一致,真光层深度比叶绿素a浓度更能解释初级生产力的时空分布模式。     

夏季闽东沿海水体中透明胞外聚合颗粒物的分布特征及影响因素

透明胞外聚合颗粒物(TEP)在海洋微食物网和海洋碳循环中发挥着重要作用。本文针对夏季闽东沿海TEP的分布特征及影响因素进行研究。结果表明,闽东沿海TEP含量(以黄原胶为标准物质计算,后同)范围为25.2～935.5 μg/L,平均值为(201.8±177.9) μg/L。整体而言,TEP的分布表现为近岸高、远岸低,表层TEP含量相对于底层要低。相关性分析显示,研究海域TEP含量与浊度和营养盐(硅酸盐、磷酸盐、硝酸盐、亚硝酸盐和铵盐)浓度呈正相关,与pH、溶解氧浓度和小型浮游生物量呈负相关。分级叶绿素a结果显示,相对于其他尺寸浮游植物,调查海域小型浮游生物可能对TEP含量的贡献最大。相比于开阔大洋中TEP主控因素为浮游植物而言,夏季闽东海域TEP主要由浮游植物在衰退阶段产生,其分布主要受颗粒物再悬浮作用影响。该结果不仅进一步阐明了近岸海域与开阔大洋TEP影响因素的区别,并且对我国近海海域不同区域TEP分布研究空白进行了补充。     

基于表层及温跃层环境变量的南太平洋长鳍金枪鱼栖息地适应性指数模型比较

为了量化比较海表层环境及温跃层环境对南太平洋长鳍金枪鱼渔场分布的影响程度;本研究采用2010-2012年南太平洋长鳍金枪鱼延绳钓渔船实际生产统计数据;结合卫星遥感所获取的海表面温度（sea surface temperature;SST）和海表面高度（sea surface height;SSH）数据以及Argo浮标所获取的温跃层上、下界水温和深度数据;运用外包络法分别构建了基于海表层环境变量、温跃层上界环境变量以及温跃层下界环境变量的3种栖息地适应性指数（habitat suitability index;HSI）模型。模型验证结果显示;基于海表层环境变量的HSI模型;HSI>0.6时所占产量比重为70.04%;投钩数量比重为70.86%;HSI>0.8时所占产量比重为24.92%;投钩数量比重为25.79%;基于温跃层上界环境变量的HSI模型;HSI>0.6时所占产量比重为82.17%;投钩数量比重为80.95%;HSI>0.8时所占产量比重为33.24%;投钩数量比重为32.69%;基于温跃层下界环境变量的HSI模型;HSI>0.6时所占产量比重为81.01%;投钩数量比重为81.54%;HSI>0.8时所占产量比重为43.51%;投钩数量比重为43.73%。研究发现;基于温跃层上界和下界环境变量的两个HSI模型预报精度明显高于基于表层环境变量的HSI模型;且基于温跃层下界环境变量的HSI模型预报精度高于基于温跃层上界环境变量的HSI模型。研究结果表明;相较于海表层环境;温跃层环境;尤其是温跃层下界环境特征对南太平洋长鳍金枪鱼资源分布的影响更为显著。     

Environmental factors affecting regional differences and decadal variations in the buried flux of marine organic carbon in eastern shelf sea areas of China

To characterize environmental factors controlling decadal-scale variations in the buried flux of marine organic carbon(BF_(C_m)) in the eastern shelf sea areas of China(ECSS),four well preserved sediment cores collected from the central Yellow Sea mud(CYSM) area,the Yellow Sea Coastal Current(YSCC) area and the Changjiang River Estuary(CRE) were investigated in this study.In the CYSM,variations in BF_(C_m) were found to be dependent on variations in primary productivity and to exhibit a cyclical trend possibly related to fluctuations in the Pacific Decadal Oscillation(PDO) and the East Asian winter monsoon index(EAWM).In the YSCC,BF_(C_m) likewise depends on primary productivity.Prior to the 1950s,variations in BF_(C_m) were similar to that of the EAWM.After the 1950s,BF_(C_m) increased rapidly and exhibited maximum values in the surface layer,consistent with an increase in primary productivity caused by the input of terrestrial nutrients associated with China's economic development.In the CRE,variations in BF_(C_m) were affected by several competing factors making it difficult to identify clear relationships between variations in BF_(C_m) and primary productivity.In contrast,long-term variability in BF_(C_m) is more similar to changes in the Changjiang River sediment load.Thus,it is speculated that the construction of dams along the Changjiang River may be the main cause of variations in BF_(C_m) in this area.Given the disproportionate effects of human activities on marine environments and decadal variations in BF_(C_m) in the ECSS,careful attention should be paid to regional differences in organic carbon preservation and environmental changes lest estimates of these values be made imprecise or inaccurate.     

基于水温垂直结构的西北太平洋柔鱼栖息地模型构建

根据1998-2004年8～10月中国大陆西北太平洋柔鱼生产数据,结合对柔鱼渔场与各水层水温的分析,以作业次数为基础建立各水层水温的适应性指数(Suitability Index,SI)模型,采用算术平均法(Arithmetic Mean Model,AMM)和几何平均法(Geometric Mean Model,GMM)建立综合栖息地指数(Habitat Suitability Index,HSI)模型;并对1998-2004年8～10月的HSI值与实际作业次数、产量和单船日产量(CPUE)作比较.结果表明,8～10月,HSI＞0.6时,AMM的产量和作业次数比重分别占83.4％和80.9％,CPUE均2.1 t/d以上;GMM的产量和作业次数比重分别占73.5％和69.6％,CPUE均2.3 t/d以上.2种模型比较认为,AMM模型稍优于GMM模型.同时,利用2005年8～10月生产数据及水温资料对HSI模型进行验证.结果表明,基于水温垂直结构的栖息地指数模型能较好地预测西北太平洋中心渔场和潜在渔场.     

Composition and geochemistry of clay sediments offshore the northeastern Sicilian coast (Southeastern Tyrrhenian Sea,Italy)

Grain-size, mineralogical and chemical analyses were carried out on fine fraction of sediments collected in the Gulfs of Patti and Milazzo, two borderland basins in the Southern Tyrrhenian extending offshore the northeastern Sicilian coast.     

Acoustically estimated size distribution of sperm whales (Physeter macrocephalus) off the east coast of New Zealand

ABSTRACT

The length-frequency distribution of sperm whales (Physeter macrocephalus) was studied on the east coast of NZ using passive acoustic recorders moored offshore of Kaikoura, Cape Palliser and Castlepoint. Sperm whale’s echolocation signals are unique among odontocete species. Their clicks are composed by multiple pulses resulting from the sound transmission within the whale head. The total length of the whales can be estimated by measuring the time delay between these pulses. A total of 997 length measurements were obtained from click trains using cepstral analysis (mean?=?14.6?m; min?=?9.6?m; max?=?18.3?m; std?=?1?m). The size-frequency distributions at all three locations were similar, although animals smaller than 12?m were not present offshore of Kaikoura. Animals of various sizes appeared to be present all year round, with no apparent seasonality in the occurrence of any size class.     

Relative importance of estuarine nurseries for species of the genus Diplodus (Sparidae) along the Portuguese coast

The relative importance of estuarine nursery areas for species of the genus Diplodus and their relations with several environmental variables was evaluated along the Portuguese coast. Nine estuarine systems were sampled with beam trawl surveys. Species of the genus Diplodus were only present in estuaries south of the Ria de Aveiro (40°38′). A latitudinal gradient of increasing species richness and abundance towards the south was found. Estuarine nurseries of Diplodus vulgaris, Diplodus sargus and Diplodus puntazzo were characterized by mud substrate, lower salinity and lower dissolved oxygen, with the exception of Ria Formosa. Diplodus bellottii was associated with estuaries with large areas and high volumes, the Tejo and the Sado. Diplodus bellottii nursery grounds were characterized by low depth. Diplodus annularis was associated with seagrass and saltmarsh habitats, certainly because it is the only species of the genus Diplodus which recruits exclusively to seagrass meadows. Diplodus annularis nursery grounds were also characterized by sand substrate, higher salinity and higher dissolved oxygen. Niche breath varied widely amongst species and location. Diplodus vulgaris generally presented the highest values of niche breath, except when D. bellottii was present. Niche overlap was not high, the highest value being that between D. vulgaris and D. sargus in the Mira estuary, with 76% spatial niche overlap. Considerations were made on these species progress towards the north in a climate warming context, taking into account the habitat associations described here.     

A preliminary rotary spectral analysis of inertial currents off the west coast of Nevj/ Zealand (Note)

Results from a preliminary spectral analysis of inertial currents at a site with co‐ordinates 42° 1.73’ S, 168°41.1 l'E and a depth of 1505 m are described. Rotary spectral analysis indicates that inertial currents form a significant constituent of the observed oscillatory currents recorded.     

Long‐term presence and habitat use of Cuvier's beaked whale (Ziphius cavirostris) in the Central Tyrrhenian Sea

Cuvier's beaked whale (Ziphius cavirostris, G. Cuvier 1823) is a poorly known species and many international agreements have asked for a better understanding of its biology for conservation purposes. In the present study, systematic cetacean surveys were carried out from ferries along a trans‐regional fixed transect in the Central Tyrrhenian Sea (Civitavecchia, Latium – Golfo Aranci, Sardinia), just outside the southeastern border of the Pelagos Sanctuary. This research provided long‐term, consistent data on Cuvier's beaked whale during two research periods (1990–1992 and 2007–2011). The objective of the research was to compare the presence, distribution and habitat use of Cuvier's beaked whale between the two investigated periods. Summer data (June–September) from the two periods were compared in terms of frequency of sightings, group size and spatial distribution related to the main ecogeographical features. A presence‐absence model (generalized additive modelling) was performed to predict habitat suitability in the two study periods. The results highlight long‐term site fidelity of Cuvier's beaked whale in the Central Tyrrhenian Sea with encounter rates comparable to the ones reported for other key areas. Separate suitability models based on 1990s and 2000s data appeared to work for each individual time period but differences were evident between the two periods, indicating changes in habitat selection over time. Our findings of the study appear to expand the definition of suitable beaked whale habitat and underline how the temporal scale of the analysis can affect the results in habitat studies. Moreover, this research highlights the importance of the Central Tyrrhenian Sea marine region for Cuvier's beaked whale and the ability of continuous monitoring to identify changes in cetacean frequency and distribution, necessary for adaptive conservation management approaches.     

小黑山岛潮下水生层生境适宜性分析-以毛蚶为例

以小黑山岛潮下水生层为研究区域,利用生境适宜性指数（habitat suitability index,HSI）模型,同时结合GIS空间分析,选划出适宜毛蚶的增殖修复区域。综合文献查阅和咨询专家咨询的方式,确定影响毛蚶生存的7个重要影响因子,分别为：底质类型,水温,盐度,溶解氧,水深,pH和氨氮。结合专家赋值法和层次分析法确定每个评价因子的权重,利用GIS空间分析模块将现状调查数据进行插值、重分类和栅格计算,绘制研究区域目标种群生境适宜性地图。结果表明：对于刺参和紫贻贝,研究区域均适宜其生长繁殖,同一物种,相同季节在空间上无站位差异,但各季节的生境适宜性分区变化明显;对于魁蚶来说,东北部海域较适宜增殖,其次为西部海域,四季均以较适宜生境为主,仅冬季出现基本适宜生境。水温是造成季节差异的主要因素,底质类型则是引起生境站位差异的重要原因。可为后续的生物多样性保育和生态修复提供基础资料参考。     

Fish assemblages and rapid colonization after enlargement of an artificial reef off the Algarve coast (Southern Portugal)

Artificial reefs (ARs) have been deployed in Algarve (Southern Portugal) coastal waters to contribute to the sustainability of local nearshore fisheries. Herein, we describe the colonization process of the recently deployed Faro/Ancão AR, and assess the time until the fish assemblage reaches stability and their seasonal patterns. In addition, we compare the results from the present study with those previously reported for an older AR. The fish assemblages were monitored monthly over a 2‐year period by means of visual census. A rapid increase in fish colonization occurred within the first 4 months. After this initial period the assemblage structure showed high similarity (> 73%). The high rate of colonization of the AR was related to the maturity already achieved by the nearby 14‐year‐old AR and to the fish migration from the Ria Formosa lagoon, a nearby nursery habitat. The reef fish assemblage structure showed a seasonal pattern, mainly associated with recruitment episodes of occasional demersal species (Boops boops, Trachurus trachurus and Pagellus spp.) in spring and summer. A total of 66% of the species found in AR are of commercial and recreational importance. The overall mean density and biomass were 2.8 ind·m^?3 and 207 g·m^?3. The occasional demersal species accounted for 42% of the fish density. The most important species in terms of biomass belong to the Sparidae family along with Dicentrarchus labrax. The fish assemblage of the new ARs showed higher mean number of species, diversity, density and biomass values than those reported for the older AR. This result was associated with enlargement of the AR area and with the fishing exploitation of the isolated, small and patchy old AR. Moreover, the high biomass values recorded in the new ARs were mainly due to the increased density of D. labrax after AR enlargement. The results of the present study are used to define guidelines for suitable management strategies for the AR areas that are exploited by the local commercial and recreational fisheries.