Picoplanktonic Algae Research Articles

Picoplanktonic algae in the northern Baltic Sea: seasonal dynamics and flagellate grazing

The seasonal succession of picoplanktonic algae was followed from March to December 1986 at a station off Tvarminne, northern Baltic Sea. This area is characterized by strong seasonal changes in water temperature and stratification Picoeukaryotes were abundant during the whole year (103 to 104 ml-'), but picocyanobacteria thrived only during summer (10' to 106 ml-'). The contrasting seasonal dynamics of these 2 groups led to the conclusion that growth of picocyanobacteria is more temperature dependent than that of the almost equally sized picoeukaryotes. However, the cyanobacterial dynamics could not be explained by temperature alone and light climatic changes may have contributed to the drastic decline of cyanobacterial numbers in the warm deep-mixed water column in the autumn. Estimates of flagellate grazing on picoplanktonic cyanobacteria were obtained by differential filtration experiments. These showed that flagellates could graze vigorously on picoalgae. Total flagellate grazing on picoalgae amounted to 15 % of annual primary production, and was estimated to be 32 and 42 % during summer and autumn, respectively. The microbial loop seems to be of major quantitative importance in the boreal northern Baltic Sea.

Nutrient and Grazer‐Mediated Effects on Picoplankton and Size Structure in Phytoplankton Communities

AbstractThis study examines the factors which contribute to the abundance of algal picoplankton in lakes. A three‐year field study of a meso‐eutrophic lake was compared with observations from oligotrophic and highly eutrophic lakes in the region. Trophic state alone (oligotrophic vs. eutrophic) was not a good predictor of the importance of picoplankton; smaller cells were relatively abundant when phosphorus was limiting other phytoplankters, but also when nitrogen was in surplus. Subsequent field experiments found that picoplankton growth was stimulated by N, but not by P additions. This relationship was strongly affected by light and grazer levels. Grazers apparently mediate the effects of nutrient deficiency, and favor the growth of larger algal size classes, especially nanoplankton. The flux of P within experimental enclosures was controlled by picoplankton abundance under low nutrient conditions, but was a function of total phytoplankton biomass under P surplus.

Predominance of picoplankton and nanoplankton in eutrophic Calder Lake

A study was conducted to examine factors regulating the biomass of algal picoplankton in Calder Lake, a small eutrophic lake in southern New York state. A particular focus was a current paradigm which suggests that larger cells may dominate in nutrient-rich waters, while smaller cells may predominate only in oligotrophic waters. Over two years, phytoplankton biomass consisted predominantly (74% on average) of very small organisms; nanoplankton (<20 to 2 µm: 39%) and picoplankton (<2 µm to 0.2 µm: 35%), despite the presence of surface blooms of colonial cyanobacteria (Microcystis aeruginosa, Anabaena limnetica), and dense metalimnetic populations of the dinoflagellate Ceratium hirundinella. This dimictic system is characterized by relatively high levels of total P (max = 85, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmiEayaara% aaaa!3702!\[\bar x\] = 9.7 µg P/L), inorganic P (max = 26, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmiEayaara% aaaa!3702!\[\bar x\] = 4.5 µg P/L), and total inorganic N (max = 285, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmiEayaara% aaaa!3702!\[\bar x\] = 85 µg P/L), but larger forms were rarely the most abundant. Unlike some marine systems, greater abundance of algal picoplankton was not associated with deeper strata (low light), or warmer temperatures. Data suggest that midsummer nutrient limitation, especially P-limitation, favors the development of pico- and nanoplankton in the limnetic zone of eutrophic lakes.

Algal picoplankton production and contribution to food-webs in oligotrophic British Columbia lakes

The pelagic communities of two contrasting oligotrophic lakes in British Columbia were studied to determine why an interior, dimictic lake (Quesnel) supports a greater biomass of zooplankton and produces larger planktivorous sockeye salmon (Oncorhynchus nerka) than a coastal warm-monomictic lake (Sproat). The ultra-oligotrophic status and differing planktivore densities in Sproat Lake increased the relative importance of algal picoplankton, diminished the abundance of large zooplankton, and increased the significance of rotifers and other small-bodied zooplankton. These picoplankton based food webs result in longer, indirect and less efficient pathways of carbon flow from phytoplankton to fish. In contrast, Quesnel Lake is a more productive oligotrophic lake and its pelagic food webs are based more on nanoplankton and small microphytoplankton that support larger-bodied zooplankton (Daphnia, Diaptomus), and a more direct and efficient two-step transfer to fish. The greater variability of the annual recruitment of sockeye fry in interior lakes may keep zooplankton communities in a non-steady state, this in turn may perpetuate the occurrence of quadrennial cyclic dominance in adult salmon returning to these systems.

ULTRASTRUCTURE AND ECOLOGY OF AUREOCOCCUS ANOPHAGEFERENS GEN. ET SP. NOV. (CHRYSOPHYCEAE): THE DOMINANT PICOPLANKTER DURING A BLOOM IN NARRAGANSETT BAY, RHODE ISLAND, SUMMER 19851

ABSTRACTObservations of a marked cessation of feeding in filter feeding animals maintained in flowing Narragansett Bay seawater in June 1985 drew our attention to a bloom of a golden alga 2 μm in diameter at unprecedented populations of 109 cells. L−1. This picoplankter lacked morphological features useful in discriminating it from other similar sized forms with either phase contrast or epifluorescence light microscopy. Natural populations of picoplankton, obtained from the height of the bloom until its decline, were examined in thin section with transmission electron microscopy. A cell with a single chloroplast, nucleus, and mitochondrion and an unusual exocellular polysaccharide‐like layer was apparently the bloom alga. The ultrastructure of this alga is consistent with that of the Chrysophyceae, and a new genus and species, Aureococcus anophagefferens is described.Attempts to grow this previously unrecognized picoplanktonic alga as an obligate phototroph failed and only yielded cultures of other previously described picoalgae. Facultative and obligate phagotrophic protists with ingested cells of Aureococcus were only observed as the bloom waned and minute diatoms became common. Cells of A. anophagefferens with virus particles typical for picoalgae occurred throughout the bloom. Populations of the usually dominant photosynthetic picoplankter, the cyanobacterium Synechococcus Nägeli, were depressed during the bloom. This could be due in part to selective grazing on Synechococcus rather than Aureococcus by elevated populations of Calycomonas ovalis Wulff which accompanied the algal bloom.

Phototrophic picoplankton: An overview from marine and freshwater ecosystems

Algal picoplankton are a ubiquitous component of the microbial plankton communities of both marine and freshwater ecosystems. They contribute significantly to the total biomass of phytoplankton communities, and in oligotrophic oceans and lakes can be responsible for up to 80–90% of the total daily or annual carbon production. As part of the “microbial loop,” they are thought to be grazed by flagellates, ciliates, rotifers, copepods, and other metazoans, and contribute to the flow of energy to higher trophic levels. This presentation highlights their discovery, distribution, physiology, production, and contribution to pelagic food webs in marine and freshwater systems.

Algal picoplankton production and contribution to food-webs in oligotrophic British Columbia lakes

Algal picoplankton production and contribution to food-webs in oligotrophic British Columbia lakes

ULTRASTRUCTURE AND PIGMENTS OF TWO STRAINS OF THE PICOPLANKTONIC ALGAPELAGOCOCCUS SUBVIRIDIS(CHRYSOPHYCEAE)1

ABSTRACTThe organelle ultrastructure and photosynthetic pigments of a new isolate of the picoplanktonic alga Pelagococcus subviridis Norris from the East Australian Current was compared with the North Pacific Ocean type species. No differences in the ultrastructure of the two isolates were observed. Mitosis was studied in detail in the Australian strain, and showed two unusual features: the de novo appearance of centrioles prior to mitosis, and the formation of a small, extra‐nuclear spindle.The major carotenoids in both strains were fucoxanthin and a 19′‐butanoyloxyfucoxanthin‐like pigment, with diadinoxanthin and diatoxanthin as secondary pigments. Several minor carotenoids have not yet been identified. In addition to chlorophylls a and c2, a new chlorophyll c derivative (chlorophyll c3), present in both strains, was separated by high‐performance thin‐layer chromatography (HPTLC). The Australian isolate, unlike the type material, showed no evidence of chlorophyllase activity during cell harvest and extraction.While the pigment composition suggests affinities with certain newly examined prymnesiophytes, organelle ultrastructure indicates Pelagococcus to be a member of the Chrysophyceae. Mitosis is, however, atypical of both Prymnesiophyceae and Chrysophyceae, and if this picoplanktonic alga is to be retained in the Chrysophyceae it must be seen as a most unusual member.

Algal Picoplankton from Marine and Freshwater Ecosystems: A Multidisciplinary Perspective

The discovery of minute (0.2–2.0 μm) algal picoplankton in the late 1970's in both marine and freshwater ecosystems has led to a resurgence of research activity throughout the world, addressing questions related to taxonomy, distribution and abundance, physiology and biochemistry, and ecological considerations of their role in aquatic food webs. To many, their discovery provided the "missing link" in the controversial carbon supply–demand question in the world's oceans and gave further credibility to the emerging new paradigm on the importance of microbial food webs in energy transfer and nutrient recycling in aquatic systems. In this essay we provide the first comprehensive multidisciplinary review of phototrophic picoplankton in lake and ocean ecosystems, discussing what is currently known about their occurrence, taxonomy, physiology, and biochemistry and their role in primary production and aquatic food webs.

Picoplankton size distributions in marine and fresh waters: problems with filter fractionation studies

The retention of algal picoplankton by Nuclepore polycarbonate filters of 0.2, 1.0, 2.0 and 3.0 μm pore size was tested in 2 marine and 3 freshwater sites. When 1 μm Nuclepore filters were used, the percentage of the total cyanobacterial cells passing the filter varied between sites and with increasing depth within sites. As much as 99% of the Synechococcus-like cells was retained by a 1 μm filter. This could lead to an underestimation of the picoplanktonic contribution or, more seriously, an apparent distribution pattern that is an artifact of the choice of filter pore size. Filter retention was also dependent on vaccum pressure during filtration. This study emphasizes the need for direct observation of picoplankton numbers in filter fractionation studies.

Picoplankton size distributions in marine and fresh waters: problems with filter fractionation studies

The retention of algal picoplankton by Nuclepore polycarbonate filters of 0.2, 1.0, 2.0 and 3.0 μm pore size was tested in 2 marine and 3 freshwater sites. When 1 μm Nuclepore filters were used, the percentage of the total cyanobacterial cells passing the filter varied between sites and with increasing depth within sites. As much as 99% of the Synechococcus-like cells was retained by a 1 μm filter. This could lead to an underestimation of the picoplanktonic contribution or, more seriously, an apparent distribution pattern that is an artifact of the choice of filter pore size. Filter retention was also dependent on vaccum pressure during filtration. This study emphasizes the need for direct observation of picoplankton numbers in filter fractionation studies.

Productivity of algal picoplankton in a small meromictic lake

Productivity of algal picoplankton in a small meromictic lake