Development of the Southern Ocean Continuous Plankton Recorder survey

The Continuous Plankton Recorder (CPR) Type I was first used in Antarctic waters during the 1925–1927 Discovery Expedition, and has been used successfully for 70 years to monitor plankton in the North Sea and North Atlantic Ocean. Sixty-five years later the CPR as a Type II version returned to Antarctic waters when the Australian Antarctic Division initiated a survey of the Southern Ocean on RSV Aurora Australis south of Australia and west to Mawson. The objectives are to study regional, seasonal, interannual and long-term variability in zooplankton abundance, species composition and community patterns, as well as the annual abundance and distribution of krill larvae. The survey covers a large area from 60°E to 160°E, and south from about 48°S to the Antarctic coast—an area of more than 14 million km². Tows are conducted throughout the shipping season, normally September to April, but occasionally as early as July (midwinter). The large areal and temporal scale means that it is difficult to separate temporal and geographical variation in the data. Hence, CPRs are now also towed on the Japanese icebreaker Shirase in collaboration with the Japanese Antarctic programme. Shirase has a fixed route and time schedule, travelling south on 110°E in early December and north on 150°E in mid-March each year, and will serve as an important temporal reference for measuring long-term interannual variability and to help interpret the Australian data. Since 1991, over 90 tows have been made, providing over 36,000 nautical miles of records. The most successful seasons to date have been the 1997/1998, 1999/2000 and 2000/2001 austral summers with 20, 31 and 26 tows, respectively. The 1999/2000 season included a unique, nearly simultaneous three-ship crossing of the Southern Ocean along 25° 30’E, 110°E and 157°E. Typical CPR tows show very high abundance of zooplankton in the uppermost 20 m of the permanently open ocean zone between the sea-ice zone and the Sub-Antarctic Front; this is an area thought to be oligotrophic. Appendicularians and small calanoid and cyclopoid copepods dominate the plankton. By comparison the surface waters of the sea-ice zone have low species diversity and abundances. Zooplankton data, and hence distribution patterns, can be time- and geo-coded to GPS data and environmental data collected by the ships’ underway monitoring system (e.g. fluorescence, water temperature, salinity, and meteorological data).     

Experiments with Zooplankton on Coral Reefs,or, Will the Real Demersal Plankton Please Come Up?

Abstract. Zooplankton was sampled with emergence traps on a Thalassia bed behind an insular reef at San Salvador. Bahamas. These traps tested the effect of sealing the trap to the substrate or allowing it to rest unsealed on the substrate. Total numbers of plankters collected did not differ between the two types of trap, but significantly more cyclopoid copepods were collected in unsealed traps and significantly more tanaids were found in sealed traps. Total densities in unsealed traps were inflated as much as 24–28 % by contamination with holoplankton. Both trap designs, but particularly the sealed traps, collected animals that apparently crawled up the insides. A substantial number of animals, as many as 9–31% of those collected in sealed traps, may not be actually planktonic. Our results suggest that reefs produce fewer meroplankters per unit of substrate, and thus meroplankters contribute less to reef foodwebs than formerly thought.     

Zooplankton nutrition,storage and fecal lipid composition in different water masses associated with the Agulhas and Subtropical Fronts

Fecal pellets of zooplankton can be important carriers of organic matter from surface to deep waters of the oceans. The summer cruise ANTARES 4 gave us the opportunity to collect zooplankton from the frontal subantarctic zone (station 7 or s-ant) and adjacent subtropical waters (station 8 or s-trop). Triglyceride fatty acid profiles were used to assess the trophic position of two copepods (Metridia lucens and Pleuromamma spp.), three euphausiids (Euphausia spinifera, Nematoscelis megalops, and Thysanoessa sp) and a decapod Acanthephyra sp. The euphausiid E. spinifera was studied at the two sites and its reaction to contrasting trophic environments and hydrology was highlighted by variations in its lipid composition. Most species showed various degree of omnivory: E. spinifera from subantarctic showed the highest degree of herbivory on phytoplankton (high proportion of 16:4(n-1), 18:5(n-3), 16:1(n-7)), while the same species at the subtropical station, as well as Thysanoessa sp and M. lucens from the subantarctic station displayed more omnivorous feeding characteristics, partly linked to the abundance of microzooplankton cells. Acanthephirasp, N. megalops and Pleuromammasp from station 8 (s-trop) appear to be essentially carnivorous (high 18:1n-9/18:1n-7 ratio, high levels of 20:1(n-9) or 22:1(n-11)). The trophic position influenced the composition of feces, with higher PUFA percentages in fecal pellets from carnivorous species. Hence, the surface faunal assemblage and the season controlled not only the quantity but also the quality of the food supply as PUFA exported towards the benthic domain.     

Seasonal food web structures and sympagic-pelagic coupling in the European Arctic revealed by stable isotopes and a two-source food web model

We simultaneously followed stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in a two-source food web model to determine trophic levels and the relative importance of open water- and ice-associated food sources (phytoplankton vs. ice algae) in the lower marine food web in the European Arctic during four seasons. The model is based upon extensive seasonal data from 1995 to 2001.Phytoplankton, represented by samples of particulate organic matter from open water (Pelagic-POM) and ice algae, represented by samples from the underside of the ice (Ice-POM), were isotopically different. Ice-POM was generally dominated by the typical ice diatoms Nitzschia frigida and Melosira arctica and was more enriched than Pelagic-POM in ¹³C (δ¹³C = −20‰ vs. −24‰), but less enriched in ¹⁵N (δ¹⁵N = 1.8‰ vs. 4.0‰). However, when dominated by pelagic algae, Ice-POM was enriched in ¹³C and ¹⁵N similarly to Pelagic-POM.The derived trophic enrichment factors for δ¹⁵N (Δ_N = 3.4‰) and δ¹³C (Δ_C = 0.6‰) were similar in both pelagic and sympagic (ice-associated) systems, although the Δ_C for the sympagic system was variable.Trophic level (TL) range for zooplankton (TL = 1.8-3.8) was similar to that of ice fauna (TL = 1.9-3.7), but ice amphipods were generally less enriched in δ¹⁵N than zooplankton, reflecting lower δ¹⁵N in Ice-POM compared to Pelagic-POM. For bulk zooplankton, TLs and carbon sources changed little seasonally, but the proportion of herbivores was higher during May-September than in October and March. Overall, we found that the primary carbon source for zooplankton was Pelagic-POM (mean 74%), but depending on species, season and TL, substantial carbon (up to 50%) was supplied from the sympagic system. For bulk ice fauna, no major changes were found in TLs or carbon sources from summer to autumn. The primary carbon source for ice fauna was Ice-POM (mean 67%), although ice fauna with TL > 3 (adult Onisimus nanseni and juvenile polar cod) primarily utilized a pelagic food source.     

东海夏季日本鲭(Scomber japonicus)和鳀鱼(Engraulis japonicus)鱼卵仔鱼分布特征

采用1999年6—8月间在东海(26°30′—32°30′N、121°00′—128°00′E)的日本鲭和鱼卵仔鱼综合调查资料,对鱼卵仔鱼的数量分布的生态特征进行分析,并就平面分布与水文环境的关系进行了初步探讨。结果表明,鱼卵分布范围较仔鱼要大,高值区主要出现在南部近海的鱼外渔场,鱼仔鱼则在近海的长江口外渔场分布较多。日本鲭仔鱼的摄食对水温盐度的要求较亲鱼产卵的水文环境要严格许多,鱼产卵受水温和盐度的影响控制较仔鱼的育肥更为显著。两种鱼卵仔鱼数量平面分布状况与黄海冷水、江浙沿岸流、台湾暖流以及黑潮在本区运动消长而产生的温、盐变化存在着密切关系,日本鲭和鱼的鱼卵数量随着浮游动物丰度减少而逐渐增加,鱼仔鱼的数量则随着浮游动物丰度的增加而增加,浮游生物饵料生物的变动对鱼卵仔鱼的分布也有一定的影响。     

Iron regeneration and organic iron(III)-binding ligand production during in situ zooplankton grazing experiment

To elucidate iron regeneration and organic iron(III)-binding ligand formation during microzooplankton and copepod grazing on phytoplankton, incubation experiments were conducted in the western subarctic Pacific. During 8 days of dark incubation of ambient water and that amended with plankton concentrate, dissolved iron and organic iron(III)-binding ligands accumulated, approximately proportionally to the decrease in chlorophyll a. The observed increases in dissolved iron concentration were much greater than those expected from the consumption of phytoplankton biomass and previously reported Fe:C value of cultured algal cells, suggesting resolution from colloidal or particulate iron adsorbed onto the algal cell surface. When copepods were added to the ambient water, organic iron(III)-binding ligands accumulated more rapidly than in the control receiving no copepod addition, although consumed phytoplankton biomass was comparable between the two treatments. Bioassay experiment using filtrates collected from the incubation experiment showed that organic ligands formed during microzooplankton grazing reduced the iron bioavailability to phytoplankton and suppressed their growth. Moreover, picoplankton Synechococcus sp. and Micromonas pusilla were more suppressed by the organic ligands than the diatom Thalassiosira weissflogii. In conclusion, through microzooplankton and copepod grazing on phytoplankton, organic iron(III)-binding ligands as well as regenerated iron are released into the ambient seawater. Because the ligands lower iron bioavailability to phytoplankton through complexation and the degree of availability reduction varies among phytoplankton species, grazing by zooplankton can shift phytoplankton community structure in iron-limited waters.     

Trophic pathways and carbon flux patterns in the Laptev Sea

The Laptev Sea is a high-Arctic epicontinental sea north of Siberia (Russia) that is one of the least understood regions of the world’s ocean. It is characterized by a shallow and broad shelf plateau, high influx of river water, sediments and nutrients during summer, long-lasting sea-ice cover from October to May, and the formation of a narrow flaw-lead polynya off the fast-ice edge during winter.Here, we describe results of a German–Russian research project (1993-present), presenting the distribution patterns and dynamics of its marine flora and fauna, as well as pathways and processes of coupling between sea-ice, water-column and sea-floor biota.Three ecological zones are distinguished along a combined east–west and Lena-impact gradient, differing in the composition of pelagic and benthic communities. In general, high Chl a concentrations in the sediments indicate a tight coupling between sympagic and pelagic primary production and nutrient supply to the benthos throughout the entire Laptev Sea. However, there were pronounced regional differences between the ecological zones in magnitude of primary production and trophic dynamics. Primary production during the ice-free summer was highest in the estuarine zone most strongly influenced by the Lena River (210 mg C m⁻² day⁻¹). The western and northeastern Laptev Sea yielded 55 and 95 mg C m⁻² day⁻¹, respectively. Moreover, the zones differed in the partitioning of carbon flux between zooplankton and benthic food webs. In the Lena zone zooplankton carbon demand was about 31 mg C m⁻² day⁻¹ whereas in the western zone it was 21 mg C m⁻² day⁻¹ and in the eastern zone 4 mg C m⁻² day⁻¹. Total benthic carbon demand was 32 mg C m⁻² day⁻¹ for the Lena zone, 56 mg C m⁻² day⁻¹ in the western zone and 100 mg C m⁻² day⁻¹ in the northeastern zone.A carbon budget constructed for the Laptev Sea indicates that (1) a high proportion of primary production is channelled through the benthic trophic web, bypassing the pelagic trophic web, and (2) autochthonous primary production in the northeastern and western Laptev Sea might not be sufficient to fuel both pelagic and benthic secondary production and, hence, input of allochthonous organic carbon is required to balance the overall carbon demand.     

南黄海浮游动物群落结构研究

根据2014年春、秋季南黄海16个站位的生物样品进行了浮游动物群落结构研究。共鉴定出99种浮游动物,其中春季68种,秋季78种。除浮游幼虫外,种类较多的类群是桡足类(34种,占总种类数的34.3%)、水螅水母(13种,13.1%)和端足类(5种,5.0%)。春季优势种为夜光虫(Y=0.259 7)、桡足幼体(Y=0.135 3)、拟长腹剑水蚤(Y=0.060 8)和伪长腹剑水蚤(Y=0.022 4),秋季时桡足幼体(Y=0.335 9)、伪长腹剑水蚤(Y=0.115 7)、强额拟哲水蚤(Y=0.053 3)、桡足类无节幼虫(Y=0.051 4)和拟长腹剑水蚤(Y=0.041 0)是优势种。春季浮游动物平均生物量为1 555.1 mg/m~3,秋季为425.8 mg/m~3。春季平均丰度为9 551.4个/m~3,秋季为2 103.7个/m~3。秋季香农-威纳指数、丰富度和均匀度结果皆比春季的高。浮游动物生物量与温度和水深相关性更高;丰度和温度相关性最高,其次和水深相关。     

Bowhead whales feed on plankton concentrated by estuarine and tidal currents in Academy Bay,Sea of Okhotsk

Academy Bay in the Sea of Okhotsk is an important summertime feeding ground for pelagic-feeding Bowhead whales (Balaena mysticetus) in the western subarctic North Pacific. The present work combines satellite observations with physical (CTD, currents, tides) and biological (zooplankton sampling) measurements. Data obtained aboard the RV Lugovoe in August–September 2003 and July–August 2004 show dense populations of zooplankton (such as copepods Calanus glacialis, Pseudocalanus sp., pteropods Limacina helicina, and chaetognaths Sagitta sp.) that are concentrated by physical mechanisms within this critically important ecosystem. We show that near-bottom, cold water intrusions from the northern Sea of Okhotsk associated with the estuarine circulation advect arctic herbivorous calanoids (Calanus glacialis) and mollusks Limacina helicina into the region.     

淮河干流浮游动物群落结构特征

2011年3、6、9和12月对淮河干流11个采样点的浮游动物群落结构进行调查研究,共检出浮游动物79属206种,其中原生动物27属69种,占浮游动物总物种数的33.5%;轮虫35属104种,占50.5%;枝角类12属27种,占13.1%;桡足类5属6种,占2.9%.总体上看,从上游至下游,浮游动物物种数呈现逐渐减少的趋势.浮游动物的丰度和生物量分别为3527447 ind./L和2452 mg/L,轮虫和原生动物丰度是淮河干流浮游动物丰度的主体,轮虫生物量是淮河干流浮游动物生物量的主体,浮游动物及各类群丰度和生物量均表现为从上游到中游逐渐增高的趋势,而从中游到下游呈现逐渐降低的趋势.上游浮游动物多样性指数和均匀度指数高于中、下游.结果表明:淮河干流上游水质为轻污染,中、下游水质为中污染或重污染.浮游动物群落结构和环境因子的冗余分析表明,水温、溶解氧和流速是与淮河干流浮游动物群落结构相关性较强的环境因子.