Trophic relationships of the sea ice meiofauna in Frobisher Bay,Arctic Canada

Summary A distinct fauna consisting mainly of nematodes, harpacticoid and cyclopoid copepods, rotifers, turbellarians and polychaete larvae, inhabits the lower levels of the sea ice in Frobisher Bay. Similar faunas are found throughout circumpolar regions. Thirteen taxa of the Frobisher Bay ice fauna were entirely herbivorous. Their food consisted of 26 genera of algae dominated by Chlamydomonas, Nitzschia, Navicula and Chaetoceros. There was a clear tendency to feed on the most abundant ice algae, hence little evidence of selective feeding. High algal food concentrations in the ice (estimated at 5000 g C/l) were in sharp contrast with the scant nourishment available from phytoplankton under the ice (8 g C/l) from mid-winter until the start of the summer bloom. Algal stocks and estimated productivity rates indicate that ice meiofaunal food requirements may be met by the ice algae. All the major ice meiofaunal species are well adapted to feeding within the ice. All are small enough to enter brine channels and secure particulate prey from surfaces within confined spaces. The ice meiofaunal species are major consumers of the ice algae and therefore important links in the transfer of energy from the ice to pelagic and benthic predators, including fishes, birds and mammals.     

Sedimentation in Arctic Canada: Species composition and biomass of phytoplankton contributed to the marine sediments in Frobisher Bay

Summary Sedimentation of phytoplankton provides food and energy for zoobenthic communities. In this study the rates, species composition and biomass of phytoplankton input to Frobisher Bay sediments were examined during ice (late November to July) and open water (late July to October) periods from 1982 to 1985. The rates were higher on the sea bed than at 20 m. The minimum rate (3x10⁵ cells·m^-2·day^-1) of sedimentation occurred during the early part of the ice period. It increased as the ice thickened and reached a maximum of 2.8x10⁸ cells·m^-2·day^-1 after the phytoplankton bloom at the beginning of the open water period in the first two weeks of August. The sedimented phytoplankton was dominated by diatoms, with a great majority of pennate species during the spring (April to June) and centric forms during the summer (July to August). Green flagellates, dinoflagellates and chrysophytes occurred as a low percentage of the total population in all seasons. Other indicators (chlorophyll a and phaeopigments) showed highest biomass levels in the deepest traps. They were consistently low during the winter (December to March) and reached their maxima during the open-water period of summer. Their abundance was correlated with the seasonal cycle of the phytoplankton in the water column.     

胶州湾浮游植物水华期群落结构特征

根据2001年8月对胶州湾海域进行的为期2d的大面积调查资料,对浮游植物的群落结构进行了初步研究,结果表明,浮游植物群落主要由沿岸暖水性种类组成,以硅藻为主,共34种;还有少量的甲藻7种和绿藻1种,湾中央水域出现的物种数最多,为37种;湾边缘最少,仅出现10种,细胞数量的密集区出现在湾东部边缘水域,最高值为6．96×10⁸个cell·m^-3;低值区出现在湾口,最低值仅为3．18×10⁶个cell·m^-3调查期间浮游植物的物种多样性及其均匀度的最低值均出现在湾东部边缘水域;高值区出现在湾口和湾中央水域,胶州湾海域水团运动和水体富营养化程度是影响浮游植物群落分布的主要环境因素。     

Seasonal variation in marine phytoplankton and ice algae at a shallow antarctic coastal site

The phytoplankton population near Davis, Vestfold Hills, Antarctica was monitored throughout 1982. Chlorophyll-a determinations and counts of living cells in both the water column and sea ice demonstrated a marked seasonality in phytoplankton abundane and species composition. From April to October nanoplanktonic organisms contributed most of the chlorophyll-a in both the sea ice and water column. Blooms of diatoms occurred in May, November and December in the bottom of the sea-ice and in January and February in the water column. Phaeocystis pouchetii was dominant during December in the water column. Large numbers of dead diatoms were found in winter. The concentrations of nitrate, dissolved inorganic phosphate and dissolved silicate increased throughout the year until December, when the concentrations of nitrate and silicate fell sharply, followed a month later by a reduction in phosphate concentration. The diversity of phytoplankton was greatest during the summer months.     

The diversity,abundance and fate of ice algae and phytoplankton in the Bering Sea

Despite being an essential part of the marine food web during periods of ice cover, sea ice algae have not been studied in any detail in the Bering Sea. In this study, we investigated the diversity, abundance and ultimate fate of ice algae in the Bering Sea using sea ice, water and sub-ice sediment trap samples collected during two spring periods in 2008 and 2009: ice growth (March–mid-April) and ice melt (mid-April–May). The total ice algal species inventory included 68 species, dominated by typical Arctic ice algal diatom taxa. Only three species were determined from the water samples; we interpret the strong overlap in species as seeding of algal cells from the sea ice. Algal abundances in the ice exceeded 10⁷ cells l^?1 in the bottom 2-cm layer and were on average three orders of magnitude higher than in the water column. The vertical flux of algal cells beneath the ice during the period of ice melt (>10⁸ cells m^?2 day^?1) exceeded export during the ice growth period by one order of magnitude; the vertical flux during both periods can only be sustained by the release of algae from the ice. Differences in the relative species proportions of algae among sample types indicated that the fate of the released ice algae was species specific, with some taxa contributing to seeding in the water column, while other taxa were preferentially exported.     

Springtime coupling between ice algal and phytoplankton assemblages in southeastern Hudson Bay,Canadian Arctic

Microalgal assemblages from the bottom ice, the ice-water interface and the water column were systematically sampled from April to June 1986, in southeastern Hudson Bay (Canadian Arctic). The taxonomic similarity between samples from the three environments was assessed using a clustering procedure. There were two groups that comprised samples from both the ice-water interface and the water column, while five other groups were made of samples originating from a single environment. Taxonomic compositions of the two mixed groups suggest two types of connexion between the ice-water interface and the water column, i.e. before the phytoplankton bloom, there was seeding of the water column by ice algae and, during ice melt, interfacial algae contributed to the water column communities that were otherwise typically phytoplankton. Overall, the phytoplankton community underwent a succession from pennate to centric diatoms. Sinking rates of algae from the ice-water interface were estimated using settling columns (SETCOL). The sinking rates increased seasonally (0.4–2.7 m d^–1), which enhanced accessibility of ice-algal cells to the pelagic grazers. Ice algae contributed to water column production as they became accessible to the pelagic grazers, and also by seeding the water column before the phytoplankton bloom.Contribution to the programs of GIROQ (Groupe interuniversitaire de recherches océanographiques du Québec) and of the Maurice Lamontagne Institute (Department of Fisheries and Oceans)     

Lipids and fatty acids in ice algae and phytoplankton from the Marginal Ice Zone in the Barents Sea

Samples of ice algae from the Marginal Ice Zone in the Barents Sea could be divided into two categories: one dominated by assemblages of Melosira arctica, and the other dominated by Nitzschia frigida and associated diatoms. Total lipid from the Melosira assemblages consisted of approximately equal amounts of polar lipids and triacylglycerols. Total lipid from the Nitzschia assemblages contained more triacylglycerols than polar lipids. Total lipid from the Melosira assemblages had higher percentages of C16 PUFA, especially 16:4(n-1) and 20:5(n-3), than that from the Nitzschia assemblages, this reflecting the higher percentages of both C16 PUFA and 20:5(n-3) in polar lipids than in triacylglycerols. Phytoplankton from the pelagic zone were␣richer in flagellates and contained less C16 PUFA and 20:5(n-3) but more C18 PUFA and 22:6(n-3). The dominance of diatoms in the ice-algae assemblages in the Marginal Ice Zone and their high nutritional value as a source of 20:5(n-3) for higher trophic levels are emphasised. Received: 24 November 1997 / Accepted: 8 February 1998     

Winter-time ecology in the Bothnian Bay, Baltic Sea: nutrients and algae in fast ice

Landfast ice algal communities were studied in the strongly riverine-influenced northernmost part of the Baltic Sea, the Bothnian Bay, during the winter-spring transition of 2004. The under-ice river plume, detected by its low salinity and elevated nutrient concentrations, was observed only at the station closest to the river mouth. The bottommost ice layer at this station was formed from the plume water (brine volume 0.71%). This was reflected by the low flagellate-dominated (93%) algal biomass in the bottom layer, which was one-fifth of the diatom-dominated (74%) surface-layer biomass of 88 μg C l⁻¹. Our results indicate that habitable space plays a controlling role for ice algae in the Bothnian Bay fast ice. Similarly to the water column in the Bothnian Bay, average dissolved inorganic N:P-ratios in the ice were high, varying between 12 and 265. The integrated chlorophyll a (0.1–2.2 mg m⁻²) and algal biomass in the ice (1–31 mg C m⁻²) correlated significantly (Spearman ρ = 0.79), with the highest values being measured close to the river mouth in March and during the melt season in April. Flagellates <20 μm generally dominated in both the ice and water columns in February–March. In April the main ice-algal biomass was composed of Melosira arctica and unidentified pennate diatoms, while in the water column Achnanthes taeniata, Scrippsiella hangoei and flagellates dominated. The photosynthetic efficiency (0.003–0.013 (μg C [μg chl a ⁻¹] h⁻¹)(μE m⁻²s⁻¹)⁻¹) and maximum capacity (0.18–1.11 μg C [μg chl a ⁻¹] h⁻¹) could not always be linked to the algal composition, but in the case of a clear diatom dominance, pennate species showed to be more dark-adapted than centric diatoms.     

太湖梅梁湾湖岸带浮游植物群落演替及其与水华形成的关系

利用2009～2010年周年观测数据,结合江苏太湖湖泊生态系统研究站15年监测数据,分析了太湖梅梁湾湖岸带浮游植物群落演替及其与蓝藻水华形成的关系.50次周监测结果表明:蓝藻门(Cyanophyta)、绿藻门(Chlorophyta)、硅藻门(Bacillariophyta)分别占浮游植物总生物量的60%、16%和22%.冬春季绿藻、硅藻为主要优势种,夏秋季蓝藻门的微囊藻占绝对优势.4月下旬～6月初,平均温度低于20℃,蓝藻没有大规模生长,硅藻门、绿藻门生物量急剧降低,总生物量小于1mg·L^-1;随后温度超过25℃,蓝藻迅速增长并很快成为绝对优势,蓝藻增加滞后于绿藻、硅藻的减少.在营养盐充足、物理因素合适的条件下,浮游植物群落结构自然演替是蓝藻水华形成的主要原因之一.     

Proterozoic phytoplankton and timing of Chlorophyte algae origins

Abstract: Morphological and reproductive features and cell wall ultrastructure and biochemistry of Proterozoic acritarchs are used to determine their affinity to modern algae. The first appearance datum of these microbiota is traced to infer a minimum age of the divergence of the algal classes to which they may belong. The chronological appearance of microfossils that represent phycoma‐like and zygotic cysts and vegetative cells and/or aplanospores, respectively, interpreted as prasinophyceaen and chlorophyceaen microalgae is related to the Viridiplantae phylogeny. An inferred minimum age of the Chlorophyte origin is before c. 1800 Ma, the Prasinophyceae at c. 1650 Ma and the Chlorophyceae at c. 1450 Ma. These divergence times differ from molecular clock estimates, and the palaeontological evidence suggests that they are older.     

Dynamics of phytoplankton in Finnish lakes

The studies on lake phytoplankton in Finland are reviewed and the major aspects of the phytoplankton dynamics are discussed. Special attention has been paid to the factors limiting productivity and species succession in different communities. After the early mainly taxonomical and floristic publications on phytoplankton at the end of last century, phytoplankton studies in lakes have proceeded along two different lines: 1) the species composition of communities and taxonomy, and 2) their production ecology or dynamics. Recently, both approaches have been combined, resulting in some profound ecological studies. In many lakes, phosphorus has been shown to be a limiting factor for phytoplankton productivity. However, it has also been shown that the irradiance and water temperature may effectively regulate the seasonal trend of phytoplankton productivity. This is the case especially in polyhumic forest lakes, where allochthonous material seems to play a major role also in primary production ecology.     

Monterey Bay phytoplankton I. Seasonal cycles of phytoplankton assemblages

Netplankton collections from shallow-water stations in MontereyBay, California were examined for 1976 and 1977. The predominatingphytoplankton forms were neritic diatom species. Recurrent speciesgroups were identified using Fager's regroup analysis and theirdistributions related to hydrographic seasons. Neritic groupswere relatively more abundant during the Davidson Current andupweiling periods; however, many of the species were presentthroughout much of the year. The appearance of oceanic groupsand species was seasonal and associated with advective events. One neritic species group was of overwhelming numerical importancebut within the group conspicuous changes in relative abundanceof phytoplankton populations occurred seasonally among speciesfrom this group. This group appears to be composed of residentspecies and may be locally retained as vegetative cells or benthicresting stages. Species cycles in Monterey Bay may be regardedas largely the result of suc-cessional changes or cycles ofautochthonous species, while species introduced by adjectiveprocesses appear to be of minor importance. The study has suggested that the presence of species in a ‘seedpopulation’, either as vegetative cells or benthic restingstages, may be important as the growth rate of the species inunderstanding and predicting composition and relative abundancein coastal phytoplankton assemblages.     

流沙湾海草床海域浮游植物的时空分布及其影响因素

2008年2月至11月对广东省流沙湾海草床海域的浮游植物进行了周年的季节调查,结果共检出浮游植物151种:冬季57种、春季66种、夏季73种、秋季66种,其中硅藻门44属123种,占浮游植物种类数的81.4%;甲藻门11属26种,占浮游植物种类数的17.2%;绿藻门和蓝藻门各1属1种,各占浮游植物种类数的0.7%。优势种共有26种,主要为夜光藻Noctiluca scintillans、威氏角毛藻Chaetoceros weissflogii、圆海链藻Thalassiosira rotula、菱形海线藻Thalassionema nitzschioides等,都是链状群体或个体较细长或较大的种类,没有个体较短小的优势种群;各季节间共有种类数在22-43种,Jaccard种类相似性指数范围在0.211-0.448,多样性指数和均匀度平均值分别为2.12和0.35,群落结构较脆弱;细胞丰度在0.24×10⁴-5.72×10⁴ 个/L,秋季最高,夏季次之,冬季最低,属季节单峰型变化,与一般亚热带春、秋季出现丰度高峰不一致。相关性分析发现,浮游植物丰度与活性硅酸盐呈极显著的正相关,与盐度呈显著的负相关,与其他因子不存在明显的相关性;叶绿素a浓度与水温呈极显著的负相关,与浮游动物丰度呈显著的负相关。从浮游植物吸收N、P的配比分析,N为四季的营养限制因子,但从N、P的绝对值看,N和P都是全年的营养限制因子,因此其水质营养类型属于亚热带贫营养型。     

中国近海生物固碳强度与潜力

通过现场调查和数据分析,首次探讨了中国近海浮游植物的固碳强度与潜力以及近海人工养殖大型藻类的固碳能力.结果表明,渤、黄、东海的浮游植物固碳强度约为2.22亿t a-1,固碳量的季节变化从大到小的顺序依次为春季、夏季、秋季、冬季,其中春夏季的固碳量占全年的65.3%.南黄海1999～2005年10～11月间浮游植物固碳强度有较大的年际变化,10～11月份7a间其浮游植物最低固碳量为3.54万t d-1,最高为16.58万t d-1,平均为10.50万t d-1,没有明显的年际变化趋势,磷对浮游植物固碳强度的影响最为明显,次之的影响因素是Chl a和亚硝氮 (NO2-N)的含量.南海的固碳能力约为渤黄东海的2倍,为4.16亿t a-1,其季节变化和渤黄东海不同,南海浮游植物在冬季的固碳能力最强,在夏季最弱.整个中国近海浮游植物年固碳量达6.38亿t,可占全球近海区域浮游植物年固碳量的5.77%.实际外海龙须菜的养殖发现,龙须菜每年固定的碳为8.18 t,养殖密度与方式对其产量和固碳量影响巨大.近几年,我国大型经济藻类养殖产量每年在120～150万t左右,换算为固碳量为36～45万t,平均每年40万t,如果海藻养殖产量每年增加5%,到2010年,我国大型经济藻类养殖的固碳量可达57万t a-1,海藻养殖是海洋增加碳汇有多重价值的重要措施.     

胶州湾叶绿素a浓度及浮游植物的粒级组成

2008年2、5、8和11月对胶州湾及邻近水域中表层叶绿素a浓度和浮游植物粒级组成进行了调查.结果表明:胶州湾内和湾外表层叶绿素a年平均浓度分别为4.90和2.03 mg·m^-3;叶绿素a浓度的平面分布呈现自东北部及近岸向中部、南部及湾外递减的趋势;叶绿素a浓度季节变化明显,冬季和夏季浓度较高,春季次之,呈现温带海域双峰型的变化趋势.胶州湾浮游植物粒级组成以微型浮游植物为主,平均占叶绿素a总量的60.9%,其次是小型浮游植物,超微型浮游植物所占比例最低,与我国近海浮游植物粒级组成基本一致.与历史资料相比,微型浮游植物所占比例有所增加,超微型浮游植物所占比例降低.     

Benthic algae compensate for phytoplankton losses in large aquatic ecosystems

Anthropogenic activities can induce major trophic shifts in aquatic systems, yet we have an incomplete understanding of the implication of such shifts on ecosystem function and on primary production (PP) in particular. In recent decades, phytoplankton biomass and production in the Laurentian Great Lakes have declined in response to reduced nutrient concentrations and invasive mussels. However, the increases in water clarity associated with declines in phytoplankton may have positive effects on benthic PP at the ecosystem scale. Have these lakes experienced oligotrophication (a reduction of algal production), or simply a shift in autotrophic structure with no net decline in PP? Benthic contributions to ecosystem PP are rarely measured in large aquatic systems, but our calculations based on productivity rates from the Great Lakes indicate that a significant proportion (up to one half, in Lake Huron) of their whole‐lake production may be benthic. The large declines (5–45%) in phytoplankton production in the Great Lakes from the 1970s to 2000s may be substantially compensated by benthic PP, which increased by up to 190%. Thus, the autotrophic productive capacity of large aquatic ecosystems may be relatively resilient to shifts in trophic status, due to a redirection of production to the near‐shore benthic zone, and large lakes may exhibit shifts in autotrophic structure analogous to the regime shifts seen in shallow lakes.     

飞来峡水库蓄水初期浮游植物组成与数量的变化

于2000~2002年的丰水期和枯水期对飞来峡水新建后库的营养状态和浮游植物进行监测。结果表明,水库中氮盐的浓度无显著变化,总磷浓度下降显著。浮游植物优势种类和丰度有较大差异。2000年浮游植物种类为29种,2001和2002年增加到99种;其中以绿藻和硅藻增加的种类数最多,分别增加34和27种。浮游植物丰度为13.4×104~41.6×104cells.L-1,2000年最高,2001年最低。2000年丰水期优势种较为单一,主要以假鱼腥藻(Pseudoanbeanaspp.)为主,枯水期主要是硅藻中的颗粒直链藻(Melosira granulata)丰度较高;2001和2002年丰水期蓝藻、绿藻和硅藻共同占优势,浮游植物无绝对的优势种,蓝藻的相对丰度较高的为假鱼腥藻、蓝纤维藻(Dactylococcopsis acicularis)和粘球藻(Gloeocapsa magma),绿藻的优势种为衣藻(Chlamydomonassp.)和美丽胶网藻(Dictyospharium pul-chellum);硅藻的优势种为梅尼小环藻(Cyclotella menighiniana)和针杆藻(Synedraspp.),枯水期主要是硅藻占优势,优势种为颗粒直链藻、变异直链藻(Melosira varians)等。     

Sea-ice algae in Arctic pack ice during late winter

Pack ice around Svalbard was sampled during the expedition ARK XIX/1 of RV “Polarstern” (March–April 2003) in order to determine environmental conditions, species composition and abundances of sea-ice algae and heterotrophic protists during late winter. As compared to other seasons, species diversity of algae (total 40 taxa) was not low, but abundances (5,000–448,000 cells l⁻¹) were lower by one to two orders of magnitude. Layers of high algal abundances were observed both at the bottom and in the ice interior. Inorganic nutrient concentrations (NO₂, NO₃, PO₄, Si(OH)₄) within the ice were mostly higher than during other seasons, and enriched compared to seawater by enrichment indices of 1.6–24.6 (corrected for losses through the desalination process). Thus, the survival of algae in Arctic pack ice was not limited by nutrients at the beginning of the productive season. Based on less-detailed physical data, light was considered as the most probable factor controlling the onset of the spring ice-algal bloom in the lower part of the ice, while low temperatures and salinities inhibit algal growth in the upper part of the ice at the end of the winter. Incorporation of ice algae probably took place during the entire freezing period. Possible overwintering strategies during the dark period, such as facultative heterotrophy, energy reserves, and resting spores are discussed.     

大亚湾浮游植物群落特征

于2002年冬、春、夏和秋季对大亚湾浮游植物进行采样调查,分析了浮游植物的种类组成、丰度、优势种、多样性及群落结构的季节变化特征和平面分布特征。并讨论了浮游植物与营养盐、水温及环流等环境因子之间的关系。2002年大亚湾浮游植物共鉴定出48属114种(包括变型和变种),丰度范围在5.79×104~5.37×106cells/m3之间,平均值为1.14×106cells/m3。其中硅藻共37属84种,其种数和细胞丰度都占绝对优势,平均丰度为1.08×106cells/m3,其次为甲藻,9属23种,平均丰度为9.91×104cells/m3。此外还鉴定出蓝藻和金藻。大亚湾浮游植物丰度变化呈单一周期型,春夏季高,秋冬季节低。虽然硅藻的丰度占优势,但秋季硅藻丰度降低(占总丰度75.8%)使甲藻和蓝藻所占比例上升。研究得出春夏季大亚湾浮游植物主要以沿岸暖水性种类为主,秋季和冬季除沿岸暖水种之外,广布种和大洋种也较多,尤其在冬季后者占优势。大亚湾浮游植物优势种类多,不同季节既有交叉又有演替。与以往调查资料相比,部分优势种发生变化,优势程度顺序和细胞丰度发生了一定改变,个体较大的细胞丰度优势逐渐增加。另外,受季风、潮流、地理位置及人类活动影响,大亚湾浮游植物丰度和群落结构有一定的季节和平面分布特征。大亚湾浮游植物的多样性在夏季偏低,尤其在大亚湾核电站和大鹏澳养殖区附近表现明显。大亚湾浮游植物的丰度、种数、优势种演替及群落结构等其它群落特征与营养盐尤其是氮、磷和N/P、水温、环流等环境因子密切相关。     

Photoacclimation in Antarctic bottom ice algae: an experimental approach

The aim of the study was to investigate the capacity of microalgae from the extremely low light habitat of bottom ice to acclimate to different light conditions. During austral spring 1997 the bottom layer of land-fast ice in Terra Nova Bay displayed high values of microalgal biomass up to 2,400 μg Chla L⁻¹ concentrated in a few centimetres ice layer. The algal assemblage was dominated by benthic pennate diatoms. Photoacclimation of the microalgae was addressed in terms of pigment spectra and photosynthetic parameters. Immediate and long term (minutes to days) changes in the photoprotective pigments (DD-cycle) were analysed. Severe photodamage occurred in microalgal assemblages exposed to high light. However, part of the bottom ice algal community showed a notable ability to acclimate to high irradiance levels. Changes in photosynthetic parameters preceded the sudden abrupt changes in pigment synthesis and the rapid increase in biomass and growth rates. This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National Program of Research in Antarctica (PNRA) of Italy.