Epipelagic mesozooplankton communities in the northeastern Indian Ocean off Myanmar during the winter monsoon

The northern Andaman Sea off Myanmar is one of the relatively high productive regions in the Indian Ocean.The abundance,biomass and species composition of mesozooplankton and their relationships with environmental variables in the epipelagic zone(~200 m)were studied for the first time during the Sino-Myanmar joint cruise(February 2020).The mean abundance and biomass of mesozooplankton were(1916.7±1192.9)ind./m3and(17.8±7.9)mg/m3,respectively.A total of 213 species(taxa)were identified from all samples.The omnivorous Cyclopoida Oncaea venusta and Oithona spp.were the top two dominant taxa.Three mesozooplankton communities were determined via cluster analysis:the open ocean in the Andaman Sea and the Bay of Bengal(Group A),the transition zone across the Preparis Channel(Group B),and nearshore water off the Ayeyarwady Delta and along the Tanintharyi Coast(Group C).Variation partitioning analysis revealed that the interaction of physical and biological factors explained 98.8%of mesozooplankton community spatial variation,and redundancy analysis revealed that column mean chlorophyll a concentration(CMCHLA)was the most important explanatory variable(43.1%).The abundance and biomass were significantly higher in Group C,the same as CMCHLA and column mean temperature(CMT)and in contrast to salinity,and CMT was the dominant factor.Significant taxon spatial variations were controlled by CMCHLA,salinity and temperature.This study suggested that mesozooplankton spatial variation was mainly regulated by physical processes through their effects on CMCHLA.The physical processes were simultaneously affected by heat loss differences,freshwater influx,eddies and depth.

Mesozooplankton distribution and diversity from the Bering Sea shelf to the Chukchi Sea

In recent decades,environmental changes in the Arctic have aroused widespread concern around the world.To better understand ecology issues such as ecosystem dynamics,the Arctic and the subarctic regions were integrated as the“pan-Arctic”region.In this study,mesozooplankton were sampled from the Bering Sea shelf to the northern Chukchi Sea during the 10th Chinese National Arctic Research Expedition in 2019.Based on the species composition and abundance,three geographical communities were identified:the Bering Sea shelf community(BSS),the Bering Strait transitional community(BST),and the Chukchi Sea shelf community(CSS).The BSS was characterized by Bering Sea oceanic species such as Eucalanus bungii;the BST was mainly composed of the pan-Arctic distributed Calanus glacialis,meroplankton of benthos,and neritic species such as Centropages abdominalis;copepods,especially the copepodite of C.glacialis,were predominant in the CSS community.The BSS community structure was strongly affected by the inflow of Bering Shelf Water,while those of BST and CSS were determined by the recruitment of local species.The zooplankton community structure is influenced by both advection and environmental changes such as warming and a prolonged productivity period.Here,it was difficult to distinguish the changes induced by climate change from the effects of the Bering Sea Water.The key to solving this problem is the accumulation of comparable data,which requires continuous monitoring of key species such as C.glacialis and Calanus hyperboreus.

Taxonomic composition, abundance and biomass of mesozooplankton in the Zhelin Bay—an estuary with intensive aquaculture

The Zhelin Bay is an estuary that supports intensive aquaculture in South China. Aside from traditional nutrient inputs derived from waste water and agriculture, the increased intensification of aquaculture has accelerated eutrophication during the past deeade, jeopardizing aquacultural production. Annual variations of mesozooplankton in the Zhelin Bay were described, providing baseline data for long-term ecological studies. The taxonomic composition, abundance and biomass of mesozooplankton were stud- ied monthly from July 2001 to July 2002 at 19 stations. Collections yielded 73 taxa, including 60 species of eopopods, three species of cladocerans, as well as tunieates, ehaetognaths, polyehaetes, medusae, ostraceds, rotatori, amphipods, planktonic mollusks, pelagic larvae, and planktonic shrimps. The Zhelin Bay was dominated by small mesozooplankton, with 76% of the species smaller than 1.4 mm, and 97% of the individuals smaller than 1.0 nun. Dominant species （ Paracalanus crassirostris, Oithona brevicornis, and Penilia avirostria） accounting for 60% of the total abundance were less than 0.6 mm in body length. Species diversity, biomass, and total abundance of mesozooplankton were greater in the samples collected outside the bay than inside the bay. Samples from the outer and eastern boundaries of the bay had greater biomass, diversity, and abundance than those from the inner and western boundaries. Total abundance and biomass had a unimodal annual pattern and were the greatest in August 2001 when water temperature was maximum, and the least in February 2002 when water temperature was minimum. Canonical correspondence analysis （CCA） revealed that temperature, turbidity, nutrients and salinity were the main determinants of spatial and temporal distributions of mesozooplankton in the Zhelin Bay, and six distinct zones were identified across the 19 sampling stations.

Seasonal Community Structure of Mesozooplankton in the Daya Bay,South China Sea

Mesozooplankton are key components of coastal ecosystems,linking the microbial food web to the classic food chain.In this study,species composition and abundance of mesozooplankton is studied for the Daya Bay in April(spring) and October(fall),2006.A total of 27 species of mesozooplankton were identified in spring and 58 species in fall.Dominant species were Oithona tenuis,Flaccisagitta enflata,Penilia avirostris and Centropages tenuiremis in spring,shifting to Microsetella norvegica,Oithona tenuis and Parvocalanus crassirostris in fall.Higher mesozooplankton abundance was found at Aotou Cove and Dapeng'ao Cove compared to other stations,indicating the influence of eutrophication on mesozooplankton community in the Daya Bay.The outbreak of Noctiluca scintillans bloom in spring reduced the species diversity and abundance of mesozooplankton.

Diel vertical migration of mesozooplankton in the northern Yellow Sea

The Yellow Sea Cold Water Mass(YSCWM),one of the most vital hydrological features of the Yellow Sea,causes a seasonal thermocline from spring to autumn.The diel vertical migration(DVM)of zooplankton is crucial to structural pelagic communities and food webs,and its patterns can be aff ected by thermocline depth and strength.Hence,we investigated zooplankton community succession and seasonal changes in zooplankton DVM at a fixed station in the YSCWM.Annual zooplankton community succession was aff ected by the forming and fading of the YSCWM.A total of 37 mesozooplankton taxa were recorded.The highest and lowest species numbers in autumn and spring were detected.The highest and lowest total densities were observed in autumn(14464.1 inds./m^(3))and winter(3115.4 inds./m^(3)),respectively.The DVM of the dominant species showed obvious seasonal variations.When the YSCWM was weak in spring and autumn,most species(e.g.Paracalanus parvus,Oithona similis,and Acartia bifilosa)stayed above the thermocline and vertically migrated into the upper layer.Calanus sinicus and Aidanosagitta crassa crossed the thermocline and vertically migrated.No species migrated through the stratification in summer,and all of the species were limited above(P.parvus and A.crassa)or below(C.sinicus and Centropages abdominalis)the thermocline.The YSCWM disappeared in winter,and zooplankton species were found throughout the water column.Thus,the existence of thermocline influenced the migration patterns of zooplankton.Cluster analyses showed that the existence of YSCWM resulted in significant differences between zooplankton communities above and below the thermocline.

Temporal variations of mesozooplankton abundance and biomass in the mangrove creek area along the Karachi coast, Pakistan

The temporal variations of mesozooplankton abundance and biomass （1-Volumetric method by settling volume and displacement volume and 2- Gravimetric method through wet weight, dry weight and ash-free dry weight） with relation to environmental parameters were studied in the mangrove creek area of Karachi coast, Pakistan. The data of mesozooplankton samples along with environmental parameters （temperature, salinity, pH, etc.） were collected during January 1998 to December 1998 from two creek stations. The abun-dance of mesozooplankton also exhibited seasonal trends at both stations. At Sta. S2, the highest and low-est abundance values were observed during post-monsoon and southwest monsoon respectively whereas, at Sta. S1, a clear trend of high abundance in pre-monsoon to low abundance in southwest monsoon was observed. Mesozooplankton abundance was also positively correlated with settling volume, displacement volume, wet weight and dry weight. The highest biomass value was observed in the northeast monsoon and pre-monsoon periods. The results of the canonical analysis of the output from the discriminate function was tested. Out of fifteen variables, only one was significantly different in single character ratios dry weight/ash free-dry weight （F3,23=4.78,P＆lt;0.005）. The mesozooplankton community was collectively composed of 28 taxa. Among these groups, copepoda （66.3%）, gastropod larvae （9.94%）, evadne （4.60%）, zoea （3.60%）, cypris nauplii （2.56%）, lemellibranch larvae （1.87%）, chaetognaths （1.81%）, ostracods （1.73%）, lucifer （1.15%） and barnacles nauplii （1.35%） contributed the most to the similarities within Sta. S1, while copepoda （74.68%）, cypris nauplii （5.29%）, gastropods （4.87%）, barnacles nauplii （4.81%）, evadne （1.72%）, zoea （1.53%） and ca-ridean larvae （1.18%） at Sta. S2. The remaining mesozooplanktonic group were accounted for less than 5% and 6% at Sta. S1 and Sta. S2 respectively, of the total organisms. Similarity percentage （SIMPER） analysis revealed that copepoda, gastropod larvae and cyprus nauplii contributed most of the similarities within Sta. S2 along Sta. S1.

Systematics, species diversity and new taxa of mesozooplankton in the West Pacific Ocean and its marginal seas: a brief compilation of monographs in China

Research and protection of biodiversity is generally started with species recognizing guided by achievement of cataloguing and illustration obtained through in situ investigation data accumulation and literature learning. Facing the shortage of taxonomist, it is getting harder to maintain important specimen collections and handle loans. The West Pacific Ocean has been operating as a center of the origin of global marine biodiversity result of the richest species diversity of marine taxa found in these waters. The present work is a compilation and summary of systematics, species diversity and new taxa of mesozooplankton major group known in West Pacific Ocean and its marginal seas （0°-45°N, 105°-152°E） according to 6 203 mesozooplankton samples acquired from 701 stations during 1965 and 2008. A total of 2 657 species belonging to 686 genera and 206 families of 10 mesozooplankton groups have been found through taxonomic identification and document consulting. In details, 697 species from 251 genera of 99 families belong to the Medusozoa, 59 species from 22 genera of 12 families to the Ctenophora, 85 species from 36 genera of 14 families to the pelagic Mollusca （Pteropoda and Heteropoda）, 416 species from 91 genera of 8 families to the Ostracoda, 908 species from 156 genera of 51 families to the Copepoda, 202 species from 60 genera of 4 families to the Mysidacea, 56 species from 8 genera of 2 families to the Euphausiacea, 105 species from 23 genera of 8 families to the Decapoda, 48 species from 13 genera of 5 families to the Chaetognatha and 81 species from 26 genera of 5 families to the Tunicata. The dominant species of each group are enumerated. Moreover, 2 new species of Medusozoa, Tubulariidae, Ectopleura, 1 new species of Medusozoa, Protiaridae, Halitiarella, 1 new genus and 1 new species of Medusozoa, Corymorphidae are established. An amount of 806 species are expanded with an increase of 43.5% on the basis of 1 852 species recorded before 2008, including 1.4% increase from tropical sea around equator, 4.0% from the frigid water in high latitude region, and 3.0% of bathypelagic-associated waters. The authors also summarized future prospects into five major areas in marine mesozooplankton research in China. Such information of qualitative phyletic classification could be of high relevance to studies on biodiversity and biogeography of marine mesozooplankton, especially for monographs contributed to make an overall and systematic conclusion on the species of marine life in China after 2008.

Seasonal and regional diff erences in long-term changes in large mesozooplankton(>505μm)biomass and abundance in a semi-enclosed subtropical bay

Obvious spatiotemporal heterogeneity is a distinct characteristic of ecosystems in subtropical bays.To aid targeted management and ecological restoration in long and narrow semi-enclosed subtropical bays,we analyzed seasonal and regional differences in long-term changes(1980-2019)in the biomass and abundance of large mesozooplankton(LMZ;>505μm)in Xiangshan Bay,Zhejiang,China.We found spatiotemporal heterogeneity in the historical changes of LMZ.Significant negative trends in LMZ biomass were found in the inner and middle bay during the warm season(summer and autumn),when the nutrient concentration(especially dissolved inorganic nitrogen)and temperature increased simultaneously.Nutrient changes in Xiangshan Bay began in the late 1980s or early 1990s,coinciding with large-scale fish cage development.A rapid decline in LMZ biomass occurred after 2005 when power plants commenced operation,accelerating the warming trend.Therefore,the joint stress of eutrophication and warming likely precipitated the decline in LMZ biomass.Conversely,a significant increase in LMZ biomass was found in the outer bay in spring.This trend was consistent with the trend of LMZ biomass near the Changjiang(Yangtze)River estuary,which indicates that the pelagic ecosystem in the outer bay was aff ected by water from the Changjiang River estuary during spring.Based on our results,ecosystem management and restoration in semi-enclosed subtropical bays should focus on internal waters,which have a poor capacity for water exchange.For Xiangshan Bay,the changes in the Changjiang River estuary ecosystem during the cold season(winter and spring)should also be considered.

海洋中型浮游动物的选择性摄食对浮游植物群落的控制

海洋中型浮游动物的选择性摄食很大程度上影响着浮游植物种群的变化,控制着海洋初级生产力的节律、规模和归宿。从海洋中型浮游动物选择性摄食对有害藻华的控制、中型浮游动物的选择性摄食机制、中型浮游动物选择性摄食的研究方法和中型浮游动物的选择性摄食模型四个方面探讨了中型浮游动物选择性摄食对控制浮游植物种群演替的贡献,为进一步预测和控制有害藻华发生提供科学依据。

夏季黄海一断面底边界层动物多样性初步研究

20 0 2年 8月 4日在黄海从青岛至济州岛断面的 4个站位上 ,进行了底边界层动物昼夜连续采样 ,对底边界层动物的多样性及其昼夜变化进行了分析。共鉴定出底边界层动物 32种 ,其中桡足类 19种 ,端足类 3种 ,涟虫 3种 ,糠虾 2种 ,毛颚类 2种 ,枝角类 2种 ,磷虾 1种 ,可划分为中型浮游动物、大型浮游动物和超底栖动物三个生物类群。主要种类有尖额真猛水蚤 (Euterpinaacutifrons)、挪威小毛猛水蚤 (Microsetellanorvegica)、戴氏猛水蚤 (Danielsseniasp .)、小拟哲水蚤 (Paracalanusparvus)和双刺纺缍水蚤 (Acartiabifilosa)等。超底栖动物和中型浮游动物是两个主要类群。此外 ,桡足类幼体 (无节幼体和桡足幼体 )也是底边界层动物的重要组成部分。多样性分析显示 :底边界层动物在 4个调查站位的均匀度 (d)皆较高 (0 .72 8- 0 .915 ) ,但种类较少 (19- 33) ,故多样性指数 (H′)较低 (2 .2 4 8-2 .82 7)。超底栖动物的多样性指数相对较高 ,中型浮游动物次之 ,大型浮游动物较低。各类群的多样性指数在白天和夜间无显著性差异 (P >0 .0 5 )。底边界层动物的丰度在细砂底质环境的 1 3站最低 ,在其他 3个具有粉砂 粘土底质环境的站位皆较高。通过聚类分析 ,可将这两种底质环境上的底边界层动物在 2 6 .6 %相似性?

大亚湾中型浮游动物群落结构和植食性

本文以中型浮游动物成体为研究对象,通过在大亚湾实验站附近一个采样点连续两年的野外调查和现场摄食实验,分析大亚湾近岸富营养化海域中型浮游动物的群落特征,及其对浮游植物的选择摄食特性。结果表明:2015—2017年实验站附近中型浮游动物的总丰度在冬季达到最高,其次为春、秋和夏季;其优势种大多是滤食性桡足类,如锥形宽水蚤(Temora turbinata)、中华哲水蚤(Calanus sinicus)等,中型浮游动物的摄食特性与优势种摄食行为有很大的相关性。中型浮游动物群落更偏好于粒径较大的小型浮游植物(20—200μm),而对微型(2—20μm)或超微型浮游植物(0.7—2μm)的摄食影响较小,甚至会因为选择性摄食对这两种类型的浮游植物的生长有间接促进作用。且中型浮游动物的摄食选择性具有明显的季节性,除每个季节均倾向于摄食甲藻和青绿藻。除此之外,在春季偏好于定鞭藻和隐藻,夏季偏好于定鞭藻和绿藻,秋季偏好于硅藻、隐藻和聚球藻。尽管硅藻的生物量在调查期间平均约占总浮游植物类群的50%,但是中型浮游动物并不主动摄食硅藻,而更偏爱生物量低但营养较高的甲藻。总体上,中型浮游动物虽然对浮游植物有一定的摄食,但其植食性较弱,不能对浮游植物的生物量进行有效控制。

夏季北极Kings Bay海域中型浮游动物群落特征

中型浮游动物是北极海域生态系统的重要组成成分,在生物地球化学循环中起着重要作用。2017年8月,调查了北极Svalbard地区Kings Bay海域中型浮游动物的种类组成及群落特征。结果表明:Kings Bay海域共检出中型浮游动物19种,桡足类是最主要类群,占总种类的57.9%,浮游动物的种类数从湾口到湾顶总体呈现逐渐减少的趋势;浮游动物的优势种为隐长腹剑水蚤(Oithona decipiens)、飞马哲水蚤(Calanus finmarchicus)和短角长腹剑水蚤(Oithona brevicornis),占浮游动物群落丰度比分别为48.0%、6.1%和4.3%,隐长腹剑水蚤占绝对优势;各站位三者丰度之和占比均超过47%;浮游动物丰度和湿重生物量均值分别为1241.5 ind·m^(-3)和290.8 mg·m^(-3),丰度分布趋势主要受优势种丰度影响,总体呈现为湾口到湾顶逐渐增多的趋势,生物量分布整体差异不大,湾顶稍高于湾口;该海域浮游动物生物多样度、均匀度和丰富度指数均值分别为2.36、0.57和1.65,湾内浮游动物多样度和丰富度差别不大,湾口浮游动物的多样度和丰富度稍高于湾内区域;被囊动物(Tunicata)和腔肠动物(Coelenterata)主要在靠近湾口区域出现,与湾口水系复杂、受北大西洋暖流等影响较大有关;湾内浮游动物丰度高于湾口,与"气候变暖—海冰融化—湾内外源营养物质增加—浮游植物增多—浮游动物生长繁殖提升"这一连锁反应有关。