Seasonal and Diel Patterns of Abundance and Productivity of Phototrophic Picoplankton in the Lower Chesapeake Bay

This study was performed to evaluate phototrophic pico-plankton (0.2 to 2.0 μm) dynamics within the lower Chesapeake Bay. A 15 month study of phototrophic picoplankton abundance and productivity was made from June 1988 to October 1989. Annual picoplankton abundance using epifluorescence microscopy ranged from 7.26 x 106 cells/1 in the winter to 9.28 x 108 cells/1 during late summer. In situ incubations of natural picoplankton populations over the 15 month study were used to test the applicability of the frequency of dividing cells technique in estimating phototrophic picoplankton growth rates. The regression equation o fμ = 2.37 x 10-3 (FDC) + 0.024 was developed to estimate phototrophic picoplankton growth rates in the lower Chesapeake Bay where productivity values were estimated using phototrophic picoplankton abundance and carbon content. Limitations and improvements in using the frequency of dividing cells technique were discussed. Productivity estimates using both frequency of dividing cells and sodium 14C-bicarbonate fractionation techniques identified phototrophic picoplankton contributing over 50% of total primary productivity during the summer season. Two high frequency diel studies measuring phototrophic picoplankton abundance and productivity in summer and winter seasons revealed physical factors in the water column partly determining phototrophic picoplankton distribution. Higher phototrophic picoplankton concentrations were associated with waters seasonally above the pycnocline. In summer, phototrophic picoplankton concentrations were highest during ebb tide when the dominant phototrophic picoplankton was phycocyanin enriched Synechococcus sp. In winter, phototrophic picoplankton concentrations were highest during flood tide when phycoerythrin enriched Synechococcus sp. dominated phototrophic picoplankton composition. Availability of phototrophic picoplankton carbon within the water column is discussed as to its influence to Bay trophodynamics

Groups without cultured representatives dominate eukaryotic picophytoplankton in the oligotrophic South East Pacific Ocean

Background: Photosynthetic picoeukaryotes (PPE) with a cell size less than 3 µm play a critical role in oceanic primary production. In recent years, the composition of marine picoeukaryote communities has been intensively investigated by molecular approaches, but their photosynthetic fraction remains poorly characterized. This is largely because the classical approach that relies on constructing 18S rRNA gene clone libraries from filtered seawater samples using universal eukaryotic primers is heavily biased toward heterotrophs, especially alveolates and stramenopiles, despite the fact that autotrophic cells in general outnumber heterotrophic ones in the euphotic zone. Methodology/Principal Findings: In order to better assess the composition of the eukaryotic picophytoplankton in the South East Pacific Ocean, encompassing the most oligotrophic oceanic regions on earth, we used a novel approach based on flow cytometry sorting followed by construction of 18S rRNA gene clone libraries. This strategy dramatically increased the recovery of sequences from putative autotrophic groups. The composition of the PPE community appeared highly variable both vertically down the water column and horizontally across the South East Pacific Ocean. In the central gyre, uncultivated lineages dominated: a recently discovered clade of Prasinophyceae (IX), clades of marine Chrysophyceae and Haptophyta, the latter division containing a potentially new class besides Prymnesiophyceae and Pavlophyceae. In contrast, on the edge of the gyre and in the coastal Chilean upwelling, groups with cultivated representatives (Prasinophyceae clade VII and Mamiellales) dominated. Conclusions/Significance: Our data demonstrate that a very large fraction of the eukaryotic picophytoplankton still escapes cultivation. The use of flow cytometry sorting should prove very useful to better characterize specific plankton populations by molecular approaches such as gene cloning or metagenomics, and also to obtain into culture strains representative of these novel groups

Invasion of a littoral cladoceran Sida crystallina into the pelagic zone of Christine Lake, NH and its potential impact on the phytoplankton community

This study evaluated the phytoplankton community and grazing influences of the zooplankton in oligotrophic Christine Lake, NH, by assessing the body size and clearance rates of the three dominant crustaceans: Sida crystallina (0.08 individuals L-1 ), Daphnia dubia (0.11 individuals L-1 ), and Leptodiaptomus sicilis (2.11 individuals L-1 ). Sida crystallina, typically a littoral cladoceran, was abundant throughout the water column in the open water, and contributed approximately 44% of the grazing in the pelagic zone. Phytoplankton abundance was examined to assess the potential impact S. crystallina might have on the phytoplankton in Christine lake. Aphanocapsa, the dominant phytoplankton in Christine Lake (relative abundance 68.54%), is a picocyanobacterium capable of forming colonies in the presence of planktonic grazers. Its ability to out-compete other phytoplankton due to differential grazing pressure suggests the appearance of the strong grazer S. crystallina may have contributed to the dominance of cyanobacteria in this oligotrophic lake

The Effects of Alewife on the Zooplankton Community in Townhouse Pond

The purpose of this study was to determine what plankton species was more dominant in Townhouse Pond and what effects predation has on the food web. Plankton size is important when determining pelagic food web structure. Plankton size along with predation determines whether the lake is dominated by top-down or bottom-up control. Plankton size and biomass, grazing rates, light intensity, and chemistry parameters were all determined for Townhouse Pond in October 2008. We concluded that Townhouse Pond is a mesotrophic lake and is mainly dominated by phytoplankton, such as Microystis and Dinobryon. Alewife (Alosa pseudoharengus), planktivorous fish, are dominant in this pond resulting in top-down control. Although various studies were conducted here, further research could determine the abundance of alewife and their prey and specific parameter that effect their predation

An assessment of the physical, chemical, and biological properties of Christine Lake, NH

As part of a comparative assessment of seven New Hampshire lakes, performed throughout the month of September 2003, students and faculty from the University of New Hampshire’s Center for Freshwater Biology sampled Christine Lake in Stark, NH. The goal of the study was to quantify the lake’s physical, chemical, and biological properties and compare it to the six other lakes studied, as well as to results from identical sampling of Christine Lake in June, 2003. Christine Lake is an oligotrophic lake with very little primary production and low densities of zooplankton. Nutrient levels were low, likely due to the forested composition of the lake’s watershed and the small number of homes on the lake’s shore. The low phosphorus concentration and high N:P ratio (TN:TP = 50) typify a phosphoruslimited system which is likely to be the cause of the minimal algal abundance (1.6 ± 0.1 µg L-1 average epilimnetic chlorophyll compared to 39.4 ± 1.0 µg L-1 in eutrophic York Pond). Predation by young Brook and Brown Trout most likely favored the increased densities of the smaller zooplankter Bosmina (average body length: 0.42 mm ± 0.01), as they are not readily visible to the trout like the larger Daphnia (average body length: 1.39 mm ± 0.03). Evidence for increased predation on Daphnia can be seen in their location in the water column (8 m and 12 m) which indicates migration to deeper waters to avoid fish predation. The depressed density and size of the zooplankton in the lake are most likely due to a lack of suitable grazing material and predation from the planktivorous fish population. Interactions between zooplankton and higher trophic levels, as well as phytoplankton, are discussed in the context of a model food web

Multifaceted impacts of the stony coral Porites astreoides on picoplankton abundance and community composition

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Limnology and Oceanography 62 (2017): 217–234, doi:10.1002/lno.10389.Picoplankton foster essential recycling of nutrients in the oligotrophic waters sustaining coral reef ecosystems. Despite this fact, there is a paucity of data on how the specific interactions between corals and planktonic bacteria and archaea (picoplankton) contribute to nutrient dynamics and reef productivity. Here, we utilized mesocosm experiments to investigate how corals and coral mucus influence picoplankton and nutrients in reef waters. Over 12 days, we tracked nutrient concentrations, picoplankton abundances and taxonomic composition of picoplankton using direct cell-counts, sequencing of SSU rRNA genes and fluorescent in situ hybridization-based abundances of dominant lineages in the presence or absence of Porites astreoides corals and with mucus additions. Our results demonstrate that when corals are present, Synechococcus, SAR11 and Rhodobacteraceae cells are preferentially removed. When corals were removed, their exudates enhanced the growth of diverse picoplankton, including SAR11 and Rhodobacteraceae. A seven-fold increase in nitrate concentration, possibly caused by nitrogen remineralization (ammonification coupled to nitrification) within the coral holobiont, may have further facilitated the growth of these taxa. In contrast, the addition of mucus resulted in rapid initial growth of total picoplankton and Rhodobacteraceae, but no measurable change in overall community structure. This study presents evidence of the multifaceted influences of corals on picoplankton, in which the coral holobiont selectively removes and promotes the growth of diverse picoplankton and remineralizes nitrogen.NSF Grant Number: OCE-1233612; NSF Oceanic Microbial Observatory Grant Number: OCE-080199

Picophytoplankton biomass distribution in the global ocean

The smallest marine phytoplankton, collectively termed picophytoplankton, have been routinely enumerated by flow cytometry since the late 1980s during cruises throughout most of the world ocean. We compiled a database of 40 946 data points, with separate abundance entries for Prochlorococcus, Synechococcus and picoeukaryotes. We use average conversion factors for each of the three groups to convert the abundance data to carbon biomass. After gridding with 1? spacing, the database covers 2.4% of the ocean surface area, with the best data coverage in the North Atlantic, the South Pacific and North Indian basins, and at least some data in all other basins. The average picophytoplankton biomass is 12 ± 22 µg Cl-1 or 1.9 g Cm-2. We estimate a total global picophytoplankton biomass of 0.53–1.32 Pg C (17–39% Prochlorococcus, 12–15% Synechococcus and 49–69% picoeukaryotes), with an intermediate/best estimate of 0.74 Pg C. Future efforts in this area of research should focus on reporting calibrated cell size and collecting data in undersampled regions

Seasonal patterns and interannual variability of phytoplankton in Lake Stechlin

The paper presents results of detailed phytoplankton investigations in Lake Stechlin between 1994 and 2003. The analysis includes the picoplankton fraction (dominated by Cyanobium sp.) that regularly appears as a deep-layer chlorophyll maximum (DCM). Planktothrix and Aulacoseira are successful competitors against Cyanobium in the isothermal period, the consequences differ markedly due to the fact that Planktothrix is able and Aulacoseira is unable to accumulate in the DCM after the onset of thermocline. The „regular-Cyanobium” and „irregular-Planktothrix, -Aulacoseira” patterns of DCM development has a basic influence on ecosystem functioning. Lake Stechlin a pristine, oligo-mesotrophic deep lake, with an established and detailed monitoring system and thus has been an ideal reference site for studying the influence of global climate changes on plankton that may improve our predictive tools for impact assessment

Trophic effects of sponge feeding within Lake Baikal\u27s littoral zone .2. Sponge abundance, diet, feeding efficiency, and carbon flux

Endemic freshwater demosponges in the littoral zone of Lake Baikal, Russia, dominate the benthic biomass, covering 44% of the benthos. We measured in situ sponge abundance and,orating and calculated sponge-mediated Fluxes of picoplankton (plankton \u3c2 mu m) for two common species, Baikalospongia intermedia and Baikalospongia bacillifera. By means of dual-beam how cytometry, we found retention efficiencies ranging from 58 to 99% for four types of picoplankton: heterotrophic bacteria, Synechococcus-type cyanobacteria, autotrophic picoplankton with one chloroplast, and autotrophic picoplankton with two chloroplasts. By using a general model for organism-mediated fluxes, we conservatively estimate that through active suspension feeding, sponges are a sink for 1.97 g C d(-1) m(-1), mostly from procaryotic cell types. Furthermore, grazing by these extensive sponge communities can create a layer of picoplankton-depleted water overlying the benthic community in this unique lake