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How microbial communities change over time in response to the environment is poorly understood. Previously a six-year time series of 16S rRNA V6 data from the Western English Channel demonstrated robust seasonal structure within the bacterial community, with diversity negatively correlated with day-length. Here we determine whether metagenomes and metatranscriptomes follow similar patterns. We generated 16S rRNA datasets, metagenomes (1.2 GB) and metatranscriptomes (157 MB) for eight additional time points sampled in 2008, representing three seasons (Winter, Spring, Summer) and including day and night samples. This is the first microbial ‘multi-omic’ study to combine 16S rRNA amplicon sequencing with metagenomic and metatranscriptomic profiling. Five main conclusions can be drawn from analysis of these data: 1) Archaea follow the same seasonal patterns as Bacteria, but show lower relative diversity; 2) Higher 16S rRNA diversity also reflects a higher diversity of transcripts; 3) Diversity is highest in winter and at night; 4) Community-level changes in 16S-based diversity and metagenomic profiles are better explained by seasonal patterns (with samples closest in time being most similar), while metatranscriptomic profiles are better explained by diel patterns and shifts in particular categories (i.e., functional groups) of genes; 5) Changes in key genes occur among seasons and between day and night (i.e., photosynthesis); but these samples contain large numbers of orphan genes without known homologues and it is these unknown gene sets that appear to contribute most towards defining the differences observed between times. Despite the huge diversity of these microbial communities, there are clear signs of predictable patterns and detectable stability over time. Renewed and intensified efforts are required to reveal fundamental deterministic patterns in the most complex microbial communities. Further, the presence of a substantial proportion of orphan sequences underscores the need to determine the gene products of sequences with currently unknown function.

A reverse phase HPLC (hlgh performance liquid chromatography) technique using a binary solvent system with a linear gradient on a Hypersilm MOS2 C-8 column is described. As well as the resolution of key chemotaxonom~c chlorophyll and carotenoid pigments, baseline separation of mono-and divinyl chlorophyll a and of lutein and zeaxanthin. and partial separation of mono-and dlvinyl chlorophyll b are a c h~e v e d in a total analysis time of less than 30 min. The method provides an optimal balance between analyte resolutlon and sample throughput and IS hence well suited to the analysis of oceanographic samples.

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Copepods are able to discriminate between different foods on the basis of particle size and nutritional quality. However, the extent of selective feeding behavior and the mechanisms controlling it in the field are still poorly understood. In this study, we investigated selective feeding behavior and egg production for Calanus helgolandicus feeding on natural phytoplankton (using high-performance liquid chromatography techniques), and egg production, at a coastal station off Plymouth with the annual phytoplankton cycle from July 1996 to June 1997. The phytoplankton succession included biomass peaks of dinoflagellates, prymnesiophytes, and diatoms. C. helgolandicus showed little selective feeding behavior throughout the study with a slight preference for diatoms. The influence of the diet composition on egg production was analyzed using forward stepwise regression methods. Prymnesiophytes and diatoms were shown to have positive effects whereas the effect of dinoflagellates was negative. The effect of the different phytoplankton peaks is analyzed and discussed in relation to the phytoplankton taxonomic composition and dietary diversity.Since the initial controversies (see Harvey 1937) the ability of calanoid copepods to discriminate between different particles, either as a function of size (Frost 1972) or of food quality (Huntley et al. 1983;Cowles et al. 1988) has been clearly demonstrated in laboratory experiments using phytoplankton cultures. Video techniques have also helped us to understand the mechanisms used by copepods to detect, capture, and manipulate different particles as a function of their characteristics, their concentration, or the physical environment (Paffenhöfer 1988;Price 1988;Kiørboe and Saiz 1995).However, field studies are less conclusive (Poulet 1978;Huntley 1981) and the factors, other than the size (Cowles 1979), governing selective feeding from natural particulate assemblages are still doubtful. Optimal foraging theory has been advanced as an explanation of selectivity in the field (DeMott and Moxter 1991;DeMott 1993DeMott , 1995a, hypothesizing that the intensity of selection should depend on the concentration of high-quality food. This has been demonstrated in the laboratory with pairs of particles (DeMott 1993) and in the field with the same food (DeMott 1995a,b). However, other studies provide evidence for nonselective feeding by copepods on natural particle mixtures (Huntley 1981;Turner and Tester 1989).On the other hand, the fact that different phytoplankton Acknowledgments This research was supported by funding from the European Commission through the TASC project, Contract MAS3-CT95-0039. B. Meyer-Harms was supported by a EU grant (TMR, MAS3-CT96-5032). Thanks are due to the captains and crew of the RV Squilla and RV Sepia for collecting the samples. We also would like to thank W. DeMott and an anonymous reviewer for their helpful comments and suggestions.