Karen Helen Wiltshire

Substrate-controlled succession of marine bacterioplankton populations induced by a phytoplankton bloom.

Blooming Succession Algal blooms in the ocean will trigger a succession of microbial predators and scavengers. Teeling et al. (p. 608) used a combination of microscopy, metagenomics, and metaproteomics to analyze samples from a North Sea diatom bloom over time. Distinct steps of polysaccharide degradation and carbohydrate uptake could be assigned to clades of Flavobacteria and Gammaproteobacteria, which differ profoundly in their transporter profiles and their uptake systems for phosphorus. The phytoplankton/bacterioplankton coupling in coastal marine systems is of crucial importance for global carbon cycling. Bacterioplankton clade succession following phytoplankton blooms may be predictable enough that it can be included in models of global carbon cycling. Seasonal diatom growth in the North Sea results in a temporal succession of metabolically specialized bacteria. Phytoplankton blooms characterize temperate ocean margin zones in spring. We investigated the bacterioplankton response to a diatom bloom in the North Sea and observed a dynamic succession of populations at genus-level resolution. Taxonomically distinct expressions of carbohydrate-active enzymes (transporters; in particular, TonB-dependent transporters) and phosphate acquisition strategies were found, indicating that distinct populations of Bacteroidetes, Gammaproteobacteria, and Alphaproteobacteria are specialized for successive decomposition of algal-derived organic matter. Our results suggest that algal substrate availability provided a series of ecological niches in which specialized populations could bloom. This reveals how planktonic species, despite their seemingly homogeneous habitat, can evade extinction by direct competition.

The warming trend at Helgoland Roads, North Sea: phytoplankton response

We combine the temperature and phytoplankton data from one of the longest aquatic data sets in history, the Helgoland Roads (North Sea, 54°11.3’N, 7°54.0’E) timeseries to evaluate the effects of climate change on the base of marine food webs. The data shows that, despite an obvious warming of 1.1°C since 1962, the mean diatom day of the algal spring bloom is delayed and shifted to the end of the first quarter of the year. This is apparently related to a warming of the autumn (October–December) temperatures. It is the first indication of a warming related shift in phytoplankton succession, the consequences of which would range from lifecycle/food resource mismatches to regime shifts in the North Sea system.

Extraction of pigments and fatty acids from the green alga Scenedesmus obliquus (Chlorophyceae)

In this paper, the efficiency of pigment and fatty acid extraction from resistant algae using Scenedesmus obliquus as an example was examined. We found that adding quartz sand and solvent to freeze-dried algal material and subsequent extraction in an ultrasound bath for 90min at −4 °C resulted in excellent extraction of these compounds. This extraction method was compared with a method regularly used for extraction of fatty acids and pigments, i.e. addition of solvents to algal material with subsequent incubation. Our extraction using the ultrasound and sand method was about twice as efficient as this method for both pigments and fatty acids. The ultrasound method is simple, extracts over 90% of the different substances in one step and conserves the relationships of pigments and fatty acids. In addition, no alteration- or breakdown products were observed with the new method. Thus, this method allows accurate quantitative extraction of both pigments and fatty acids from Scenedesmus obliquus and other algae. The method was also been found to be as effective for Cryptomonas erosa (Cryptophyceae), Cyclotella meneghiniana (Bacillariophyceae), Microcystis aeruginosa (Cyanophyceae), and Staurastrum paradoxum (Chlorophyceae, Desmidiaceae) and is thus applicable to a wide spectrum of algae.

Picoeukaryotic Plankton Diversity at the Helgoland Time Series Site as Assessed by Three Molecular Methods

We analyzed picoeukaryote assemblages in the German Bight at the Helgoland time series site by sequencing cloned eukaryotic 18S rRNA genes in six genetic libraries plus one library from the Orkney Islands from a cruise of opportunity. The libraries were constructed from environmental samples collected at different periods of the year. The same samples were also analyzed using a fingerprinting technique, single-strand conformational polymorphism (SSCP), and DNA microarrays with class-level oligonucleotide probes. One hundred unique clones were analyzed from each library, thus insuring over 85% coverage of the library. The V4 region of the 18S rRNA gene was sequenced from each of these clones, thus providing the most discrimination among the clones. The nonphotosynthetic picoeukaryotic component dominated over the photosynthetic one and was represented by the ciliates at 45% and group II alveolates at 42%. Prasinophytes dominated the photosynthetic group at 40%, but other picoplankton groups, such as bolidomonads and chrysophytes, were also present. Totally novel groups were found in the cryptomonads and in the dinoflagellates. A new algal group sister to the cryptophyte nuclear gene and the glaucocystophytes was also found. These three groups have been found in other picoeukaryotic planktonic clone libraries. SSCP analyses at closer time intervals suggest that clone libraries should be made at weekly intervals if succession in the picoeukaryotic plankton community is to be monitored accurately. A comparison of annual samples suggests thatthere appears to be an annual cycle with regard to species composition. Microarray analysis supported the clone library data and offered a faster means of community analysis, which can be performed with similar accuracy and with higher throughput for a more in-depth analysis.

Lipid and fatty acid composition of diatoms revisited: Rapid wound-activated change of food quality parameters influences herbivorous copepod reproductive success

Lipid and fatty acid composition are considered to be key parameters that determine the nutritive quality of phytoplankton diets for zooplanktonic herbivores. The fitness, reproduction and physiology of the grazers are influenced by these factors. The trophic transfer of lipids and fatty acids from algal cells has been typically studied by using simple extraction and quantification approaches, which, as we argue here, do not reflect the actual situation in the plankton. We show that cell disruption, as it occurs during a predators grazing on diatoms can drastically change the lipid and fatty acid content of the food. In some algae, a rapid depletion of polyunsaturated fatty acids (PUFAs) is observed within the first minutes after cell disruption. This fatty acid depletion is directly linked to the production of PUFA‐derived polyunsaturated aldehydes (PUA); these are molecules that are thought to be involved in the chemical defence of the algae. PUA‐releasing diatoms are even capable of transforming lipids from other sources if these are available in the vicinity of the wounded cells. Fluorescent staining reveals that the enzymes involved in lipid transformation are active in the foregut of copepods, and therefore link the depletion processes directly to food uptake. Incubation experiments with the calanoid copepod Temora longicornis showed that PUFA depletion in PUA‐producing diatoms is correlated to reduced hatching success, and can be compensated for by externally added single fatty acids.

Recurring patterns in bacterioplankton dynamics during coastal spring algae blooms

A process of global importance in carbon cycling is the remineralization of algae biomass by heterotrophic bacteria, most notably during massive marine algae blooms. Such blooms can trigger secondary blooms of planktonic bacteria that consist of swift successions of distinct bacterial clades, most prominently members of the Flavobacteriia, Gammaproteobacteria and the alphaproteobacterial Roseobacter clade. We investigated such successions during spring phytoplankton blooms in the southern North Sea (German Bight) for four consecutive years. Dense sampling and high-resolution taxonomic analyses allowed the detection of recurring patterns down to the genus level. Metagenome analyses also revealed recurrent patterns at the functional level, in particular with respect to algal polysaccharide degradation genes. We, therefore, hypothesize that even though there is substantial inter-annual variation between spring phytoplankton blooms, the accompanying succession of bacterial clades is largely governed by deterministic principles such as substrate-induced forcing. DOI: http://dx.doi.org/10.7554/eLife.11888.001

Revision and quality analyses of the Helgoland Reede long-term phytoplankton data archive

The Biological Station on Helgoland has one of the longest data series for phytoplankton species composition in the world. Since 1962, phytoplankton has been counted to a species level on a daily basis (weekdays). One of the main reasons why this data set has rarely been used is that it has never been subjected to proper quality control or inventoried properly. This paper describes the quality control which we have now carried out on this data set and also represents the first inventory of the data and its meta-information. A comparison of the electronic database where the data is archived and the original recorded lists from the different persons dealing with the samples was an integral part of the evaluation. Apart from recording inconsistencies in species identification, we also recorded and corrected the many differences found between the electronic and paper data. The evaluation was carried out in a direct comparative manner to discern taxonomic discrepancies, and in order to find random errors in the transfer of data from paper to computer random checks of the data were carried out. This paper serves to illustrate the level of quality control required when dealing with archived phytoplankton data and illustrates the typical problems encountered.

Global impacts of the 1980s regime shift

Abstract Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change‐point analysis and a sequential t‐test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earths biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur.

The determination of algal biomass (as chlorophyll) in suspended matter from the Elbe estuary and the German Bight: A comparison of high-performance liquid chromatography, delayed fluorescence and prompt fluorescence methods

Abstract HPLC methods are now widely accepted as being the only accurate means of quantifying chlorophyll in aquatic systems. Very little is known about the comparability of HPLC with conventional in situ prompt fluorescence methods and with newer techniques involving the measurement of delayed fluorescence of phytoplankton (measure of living algal biomass) in aquatic systems. This paper investigates the use of HPLC for the calibration of in situ delayed fluorometric and Turner fluorometric methods and the correlation of these methods to one another when applied to chlorophyll measurements in waters from the Elbe estuary and the German Bight. The data shows that the correlations of HPLC to both methods were high r2=0.7–0.99 when all the samples taken were from the reaches of the river Elbe (605–725 km). The correlations of all methods were low at r2=0.45–0.52 for samples taken in the saline part of the Elbe plume and when the chlorophyll concentrations were low (0.2–9 μg·l−1) and with comparatively high chlorophyllide and chlorophyll c contents. Generally the correlations of HPLC to delayed fluorescence were better than the other correlations. This was probably due to the fact that delayed fluorescence measurements are not affected by the presence of other chlorophylls and their breakdown products whereas prompt fluorescence signals are. Delayed and prompt fluorescence methods can be calibrated accurately against HPLC values for chlorophyll in the natural samples and correlations remained good over several days. However, we suggest that it is advisable to check these as often as possible, particularly in the face of measurable changes of turbidity, salinity or spectral properties of the water. In this work the May and October slopes for the comparisons HPLC: delayed fluorescence in the limnic Elbe below Hamburg were similar (i.e. 223–245). A significantly lower slope (160) was found for the 32 stations in the Elbe mouth/German Bight. This indicates that we were dealing with different water bodies and thus different algal populations and is backed up by the HPLC fingerprints of the samples. Our work shows conclusively that although a correlation may be good between absolute chromatographic methods and fluorometric/photometric methods, one cannot extrapolate a long-term conversion factor which holds for different sampling times or sites in any one system, not to mention between systems.

A reduced model of the fluorescence from the cyanobacterial photosynthetic apparatus designed for the in situ detection of cyanobacteria

Fluorometric determination of the chlorophyll (Chl) content of cyanobacteria is impeded by the unique structure of their photosynthetic apparatus, i.e., the phycobilisomes (PBSs) in the light-harvesting antennae. The problems are caused by the variations in the ratio of the pigment PC to Chl a resulting from adaptation to varying environmental conditions. In order to include cyanobacteria in fluorometric analysis of algae, a simplified energy distribution model describing energy pathways in the cyanobacterial photosynthetic apparatus was conceptualized. Two sets of mathematical equations were derived from this model and tested. Fluorescence of cyanobacteria was measured with a new fluorometer at seven excitation wavelength ranges and at three detection channels (650, 685 and 720 nm) in vivo. By employing a new fit procedure, we were able to correct for variations in the cyanobacterial fluorescence excitation spectra and to account for other phytoplankton signals. The effect of energy-state transitions on the PC fluorescence emission of PBSs was documented. The additional use of the PC fluorescence signal in combination with our recently developed mathematical approach for phytoplankton analysis based on Chl fluorescence spectroscopy allows a more detailed study of cyanobacteria and other phytoplankton in vivo and in situ.