Despite their importance in shaping the structure and function of marine microbial food webs, little is known about factors regulating marine virus abundance. Previous work demonstrated clearance of laboratory‐cultured Emiliania huxleyi virus by the appendicularian Oikopleura dioica ; however, the applicability of this interaction to natural virus assemblages was not investigated. Here, we conducted controlled laboratory exper...

By shunting material out of the predatory pathway toward detritus and dissolved material, viruses are believed to have an important impact on biogeochemical functions of the pelagic microbial food web. To include viruses as a single plankton functional type (PFT) in dynamic food web models is, however, not trivial since they will then compete with predators for the same host/prey community as a shared limiting resource. As rec...

Phytoplankton play a central role in the regulation of global carbon and nutrient cycles, forming the basis of the marine food webs. A group of biogeochemically important phytoplankton, the coccolithophores, produce calcium carbonate scales that have been hypothesized to deter or reduce grazing by microzooplankton. Here, a meta-analysis of mesocosm-based experiments demonstrates that calcification of the cosmopolitan coccolith...

Summary Ocean acidification (OA), a consequence of anthropogenic carbon dioxide (CO 2 ) emissions, strongly impacts marine ecosystems. OA also influences iron (Fe) solubility, affecting biogeochemical and ecological processes. We investigated the interactive effects of CO 2 and Fe availability on the metabolome response of a natural phytoplankton community. Using mesocosms we exposed phytoplankton to ambient (390 μatm) or futu...

This article is a response to Korell et al., 26, 325–327 ; See also the Commentary on this article by Muller et al., 26, e4–e5 ; See also the response to this Letter to the Editor by Korell et al., 26, 328–329 .

Arctic waters are often enriched with terrestrial dissolved organic matter (DOM) characterized by having elevated visible wavelength fluorescence (commonly termed humic‐like). Here, we have identified the sources of fluorescent DOM (FDOM) in a high Arctic fjord (Young Sound, NE Greenland) influenced by glacial meltwater. The biological transformation of FDOM was further investigated using plankton community size‐fractionation...

In food webs, interactions between competition and defence control the partitioning of limiting resources. As a result, simple models of these interactions contain links between biogeochemistry, diversity, food web structure and ecosystem function. Working at hierarchical levels, these mechanisms also produce self‐similarity and therefore suggest how complexity can be generated from repeated application of simple underlying pr...

Appendicularians are planktonic marine tunicates with elaborate filter‐feeding houses that can efficiently trap particles as small as 0.2 μm. While marine viruses are seldom considered outside their role in disease transmission, we conducted a controlled laboratory experiment to determine if the appendicularian Oikopleura dioica can trap and ingest the Emiliania huxleyi virus (EhV; 160–180 nm diameter). Removal and retention o...

Interactions of bottom‐up factors such as the availability of mineral and organic nutrients, and top‐down factors like predation and viral infection affect microbial communities of the pelagic food web. Hypothesis derived from previous experimental and modeling work suggest some general mechanisms on how these factors may be linked and call for an experiment to test interactions between (1) nitrogen source and diatom cell size...

In order to characterize copepod feeding in relation to microbial plankton community dynamics, we combined metabarcoding and metabolome analyses during a 22‐day seawater mesocosm experiment. Nutrient amendment of mesocosms promoted the development of haptophyte ( Phaeocystis pouchetii )‐ and diatom ( Skeletonema marinoi )‐dominated plankton communities in mesocosms, in which Calanus sp. copepods were incubated for 24 h in flow...

Microzooplankton dilution grazing experiments conducted in phytoplankton rich waters, particularly in polar and subpolar seas, often result in calculation of nonsignificant or negative grazing coefficients. We hypothesized that preparation of filtered seawater (FSW) from water containing high biomass of phytoplankton results in release of allelochemicals that inhibit phytoplankton growth, lowering the net growth of phytoplankt...

Microalgae in the division Haptophyta play key roles in the marine ecosystem and in global biogeochemical processes. Despite their ecological importance, knowledge on seasonal dynamics, community composition and abundance at the species level is limited due to their small cell size and few morphological features visible under the light microscope. Here, we present unique data on haptophyte seasonal diversity and dynamics from...

Most studies of spring bloom succession in Norwegian waters have employed light microscopy and accounted for species composition of phyto‐ and zooplankton. Flow cytometry and molecular tools enable us to extend such investigations to include smaller organisms like bacterio‐ and virioplankton. Here, we describe succession and diversity of algae, bacteria, and viruses in relation to environmental changes from 15 February to 27 A...