A synthesis of large-scale patterns in the planktonic prey of larval and juvenile cod (Gadus morhua)

Data from 40 published studies of the diet composition of larval and juvenile cod (Gadus morhua) from around the northern North Atlantic were summarized to assess generic patterns in ontogenetic and regional variability in the key prey. The results showed that larvae at the northern edge of the latitudinal range of cod depend primarily on development stages of the copepod Calanus finmarchicus, whilst those at the southern edge depend on Para‐ and Pseudocalanus species. Juvenile cod preyed on a wider range of taxa than larvae, but euphausiids were the main target prey. Analysis of regional variations in the relative abundances of C. finmarchicus and Para/Pseudocalanus spp. in the plankton, as estimated by the continuous plankton recorder (CPR) surveys, showed a similar geographical pattern to the larval cod stomach contents. Comparison of CPR data from the 1960s and 70s with data from the 1990s showed that the boundary between C. finmarchicus and Para/Pseudocalanus spp. dominance has shifted northwards on both sides of the Atlantic, whilst the abundance of euphausiids in the southern cod stock regions has declined. The results are discussed in relation to regional differences in the response of cod stocks to climate variability.     

Influences of human activity and climate on the stock-recruitment dynamics of whitefish, Coregonus lavaretus, in Lake Geneva

Abstract  Analysis of long-term catches from the deep peri-alpine Lake Geneva, showed a shift in the stock-recruitment relationship of Coregonus lavaretus (L.), a target species of commercial fishing. This change was mainly related to large-scale meteorological factors. Higher spring water temperatures may have improved larval survival and hence recruitment of whitefish via: (1) a better match between the hatching date of whitefish larvae and development of their zooplankton prey; and (2) the positive temperature effect on larval growth. In Lake Geneva, changes in regulatory mechanisms coupled with stocking and improved water-quality have led to an explosion in the C. lavaretus population in recent years. These results highlight the relevance of long-term changes in the stock-recruitment relationship for management of aquatic ecosystems that are sensitive to climate forcing.     

秋香江冬季水质现状及浮游生物群落结构特征

【目的】调查秋香江上游、中游和下游3个水电站6个监测断面的水环境因子、浮游生物组成等,阐明秋香江的水生态现状。【方法】分别利用综合营养状态指数、生物多样性指数和冗余分析,调查水质现状、浮游生物的群落结构特征及两者间的关系。【结果】秋香江水体透明度为0.32～0.53 m,叶绿素a含量为0.10～0.43 mg/L,总磷含量为0.6～5.3 mg/L,总氮含量为1.39～4.33 mg/L,高锰酸盐浓度为 0.70～3.90 mg/L,综合营养状态指数表明秋香江水体现处于中营养状态水平;共鉴定出53种浮游植物和62种浮游动物,浮游植物密度和浮游动物丰度范围分别为5.1×10~8～1.89×10~9 cells/L和3.93～232.87 ind/L,其中绿藻、硅藻、蓝藻、原生动物和轮虫为优势种;综合浮游生物的多样性指数来看,秋香江属于中污染水平。【结论】秋香江上游受到了一定程度的污染,沿着河流方向污染程度减小,溶解氧是影响秋香江浮游生物群落结构的关键环境因子。     

东海浮游异足类环境适应分析

根据1997~2000年东海23°30′~33°00′N、118°30′~128°00′E海域4个季节海洋调查资料,采用浮游异足类物种丰度和同步的温、盐度数据拟合曲线,构建数学模型,计算物种分布的最适温度和盐度值。同时根据以往对异足类生态特征分析的结论,划分东海浮游异足类各物种的生态类型。结果表明,塔明螺(Atlanta turriculata)和拟翼管螺(Firoloi-da desmaresti)分布在外海,具有高温、高盐的适应特征,是热带大洋种。其他为亚热带外海种,其中玫瑰明螺(Atlantarosea)具广温种特征,明螺(Atlanta peroni)适温偏低,有广盐种的特征,大口明螺(Atlanta lesueuri)分布在盐度较高的水域,扁明螺(Atlanta depressa)具有近海种特征。东海浮游异足类总体上属于典型的暖水性生态类型,温、盐适应范围较窄,对水温和盐度敏感,是较好的指示种。东海浮游异足类主要分布在28°00′~30°00′N,124°00′~126°00′E的海域,绝大多数物种难以逾越冷水水团的阻隔,这是浮游异足类很少在黄渤海出现的主要原因之一。浮游异足类生态类型划分在古气象海洋学、海洋地质、海洋物理和海洋生物学的研究中具有重要的意义。     

上海城市河流浮游动物季节变化及其与环境因子的关系

探究河道水体中浮游动物群落分布的变化及影响因素对河道水体生物多样性的维持和水生生态系统保护具有非常重要的意义。本研究于2017年9月至2018年8月对上海徐汇区代表性的城市河道进行了环境因子和浮游动物群落结构的周年调查,共采集到浮游动物32种,其中轮虫25种,桡足类4种,枝角类3种。全年浮游动物优势种12种,包括轮虫10种,桡足类1种,枝角类1种。不同季节环境因子差异显著,浮游动物种数、丰度和生物量均为夏季最高,冬季最低。浮游动物的典范对应分析（CCA）显示,氮磷比、叶绿素a浓度和溶解氧是影响该水体浮游动物群落差异的显著环境因子。运用水质理化因子、多样性指数及浮游动物优势种进行水质污染水平评价,判断该河流水质状况属于中污型。调查结果可为上海市城市河道生态环境保护提供理论支撑。     

Plankton abundance and size structure in the northern North Pacific Ocean in early summer

Phyto- and zooplankton abundance and size structure were investigated in the northern North Pacific Ocean (37.0–49.5^oN along 180^o longitude) during June of 1987. The area between 41.5^oN and 47.5^oN was expected to be abundant in phytoplankton since both water column stability and nutrient availability were favourable for phytoplankton growth. Actual phytoplankton abundance was, however, low between 41.5^oN and 45.5^oN. In particular, abundance of net phytoplankton (>10μm) was low although picophytoplankton (<2 μm) was abundant between 41.5^oN and 43.5^oN. The zooplankton community between 41.5^oN and 45.5^oN was characterized by a large amount of net zooplankton and a small amount of microzooplankton. This situation may be best explained by top-down control; that is, net zooplankton grazing suppressed net phytoplankton and microzooplankton abundance. The diminished microzooplankton promoted the increase of picophytoplankton. Because planktivorous Pacific saury were abundant between 40.0^oN and 41.0^oN, it is further speculated that the low biomass of net zooplankton south of 41.0^oN resulted from feeding by Pacific saury. The reduced grazing pressure of net zooplankton may have enhanced the growth of net phytoplankton and microzooplankton in this region.     

后官湖浮游生物群落结构特征及其环境驱动因子

为了了解后官湖国家湿地公园水生态环境现状,于2020年1月至12月对后官湖的水质、浮游植物和浮游动物进行了监测。结果表明后官湖西部湖区的总磷、高锰酸盐指数最高,是后官湖的主要污染来源。综合营养状态指数TLI(Σ)评价表明后官湖属于中营养状态,Shannon-Weaver指数和Pielou指数结果显示后官湖总体上为轻度污染到中度污染状态。调查期间共检出7门54属浮游植物,其中1月和4月主要以绿藻门和隐藻门占优势,5月至12月则以蓝藻门占优势。5月、9月-10月桡足类在浮游动物群落中占优势,其他月份则是轮虫类占优势。相比于2017年-2019年,2020年后官湖的营养状态水平和浮游植物丰度出现了明显的下降,而大型浮游动物在群落中的比例则明显上升。Spearman相关分析和冗余分析表明影响后官湖浮游植物群落的主要环境驱动因子为水温、透明度和浮游动物丰度。后官湖环境管理的不断加强和新冠疫情导致的流域内人类活动的减弱可能是后官湖2020年水生态环境质量明显提升的原因。     

同安湾浮游动物数量的平面分布和季节变动

本文主要研究2000年同安湾浮游动物的种类组成和数量分布，并就其与环境因子的关系进行了初步探讨。结果表明，在同安湾共记录到浮游动物69种及12种浮游幼虫，以近岸低盐种类为主。浮游动物数量季节分布呈现春季高，冬、夏季居中，秋季最低的特点。种类数的季节分布与水温的季节变化一致。浮游动物数量与养殖贝类、浮游植物细胞数密切相关，并与浮游植物数量呈显著的正相关关系。同安湾浮游动物的数量与邻近养殖水域西海域的相当，比马銮湾的低。与历史资料比较，同安湾浮游动物的次级生产力水平比1995年的有所上升，但恢复得较慢。     

Cryopreservation of marine microalgae and potential toxicity of cryoprotectants to the primary steps of the aquacultural food chain

Cryopreservation, a technique of high potential for culture collections, might offer a solution for reliable supply of microalgae in aquaculture units. Marine microalgae used in aquaculture were cryopreserved under 4, −20 and −80 °C using common cryoprotectants (methanol, dimethylsulfoxide (DMSO), propylene glycol and polyvinylpyrrolidone (PVP)) with promising results for Chlorella minutissima, Chlorella stigmatophora, Isochrysis galbana and Dunaliella tertiolecta. As cryoprotectants usually are toxic above certain concentrations and exposure time, and assuming that low amounts of cryoprotectants will remain in regenerated cultures, an experimental scheme was employed to explore the lower limits of safety for these algae and their primary consumers in hatchery food chains. Results showed that methanol was well tolerated by C. stigmatophora and D. tertiolecta up to a concentration of 1.6% (v/v) while I. galbana could not survive in culture at any concentration and C. minutissima exhibited some 30% of the control's yield at 0.2%. DMSO was highly tolerated up to 1.0% by all strains with the Chlorella strains surviving well up to 2%. Propylene glycol was not only tolerated up to 8% by Dunaliella but induced mixotrophic growth as well, while for Isochrysis it was lethal at any concentration. Among zooplanktonic consumers, brine shrimp Artemia nauplii could tolerate very high concentrations of the tested cryoprotectants, the rotifer Brachionus plicatilis was found sensitive to low amounts of PVP, while the nauplii of the shrimp Penaeus japonicus and the crab Eriocheir sinensis were in general very sensitive to all cryoprotectants and in several cases to much lower amounts than 1%. However, as long as the residues of cryoprotectants are kept below 1% in the regenerated cultures, there will be no problem with the animal consumers.