Post-extinction recovery of the Phanerozoic oceans and biodiversity hotspots.

The fossil record of marine invertebrates has long fuelled the debate as to whether or not there are limits to global diversity in the sea. Ecological theory states that, as diversity grows and ecological niches are filled, the strengthening of biological interactions imposes limits on diversity. However, the extent to which biological interactions have constrained the growth of diversity over evolutionary time remains an open question.

Particulate and dissolved fluorescent organic matter fractionation and composition: Abiotic and ecological controls in the Southern Ocean.

Phytoplankton-derived organic matter sustains heterotrophic marine life in regions away from terrestrial inputs such as the Southern Ocean. Fluorescence spectroscopy has long been used to characterize the fluorescent organic matter (FOM) pool. However, most studies focus only in the dissolved FOM fraction (FDOM) disregarding the contribution of particles.

Energetic equivalence underpins the size structure of tree and phytoplankton communities.

The size structure of autotroph communities - the relative abundance of small vs. large individuals - shapes the functioning of ecosystems. Whether common mechanisms underpin the size structure of unicellular and multicellular autotrophs is, however, unknown.

Nutrient limitation suppresses the temperature dependence of phytoplankton metabolic rates.

Climate warming has the potential to alter ecosystem function through temperature-dependent changes in individual metabolic rates. The temperature sensitivity of phytoplankton metabolism is especially relevant, since these microorganisms sustain marine food webs and are major drivers of biogeochemical cycling. Phytoplankton metabolic rates increase with temperature when nutrients are abundant, but it is unknown if the same pattern applies under nutrient-limited growth conditions, which prevail over most of the ocean.

Trophic and tectonic limits to the global increase of marine invertebrate diversity.

The marine invertebrate fossil record provides the most comprehensive history of how the diversity of animal life has evolved through time. One of the main features of this record is a modest rise in diversity over nearly a half-billion years. The long-standing view is that ecological interactions such as resource competition and predation set upper limits to global diversity, which, in the absence of external perturbations, is maintained indefinitely at equilibrium.

Continental erosion and the Cenozoic rise of marine diatoms.

Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms.

Resource supply overrides temperature as a controlling factor of marine phytoplankton growth.

The universal temperature dependence of metabolic rates has been used to predict how ocean biology will respond to ocean warming. Determining the temperature sensitivity of phytoplankton metabolism and growth is of special importance because this group of organisms is responsible for nearly half of global primary production, sustains most marine food webs, and contributes to regulate the exchange of CO2 between the ocean and the atmosphere. Phytoplankton growth rates increase with temperature under optimal growth conditions in the laboratory, but it is unclear whether the same degree of temperature dependence exists in nature, where resources are often limiting.

Unimodal size scaling of phytoplankton growth and the size dependence of nutrient uptake and use.

Phytoplankton size structure is key for the ecology and biogeochemistry of pelagic ecosystems, but the relationship between cell size and maximum growth rate (μ(max) ) is not yet well understood. We used cultures of 22 species of marine phytoplankton from five phyla, ranging from 0.1 to 10(6) μm(3) in cell volume (V(cell) ), to determine experimentally the size dependence of growth, metabolic rate, elemental stoichiometry and nutrient uptake.

Isometric size-scaling of metabolic rate and the size abundance distribution of phytoplankton.

The relationship between phytoplankton cell size and abundance has long been known to follow regular, predictable patterns in near steady-state ecosystems, but its origin has remained elusive. To explore the linkage between the size-scaling of metabolic rate and the size abundance distribution of natural phytoplankton communities, we determined simultaneously phytoplankton carbon fixation rates and cell abundance across a cell volume range of over six orders of magnitude in tropical and subtropical waters of the Atlantic Ocean. We found an approximately isometric relationship between carbon fixation rate and cell size (mean slope value: 1.

Marine planktonic microbes survived climatic instabilities in the past.

In the geological past, changes in climate and tectonic activity are thought to have spurred the tempo of evolutionary change among major taxonomic groups of plants and animals. However, the extent to which these historical contingencies increased the risk of extinction of microbial plankton species remains largely unknown. Here, I analyse fossil records of marine planktonic diatoms and calcareous nannoplankton over the past 65 million years from the world oceans and show that the probability of species' extinction is not correlated with secular changes in climatic instability.

Phytoplankton biogeography and community stability in the ocean.

Background: Despite enormous environmental variability linked to glacial/interglacial climates of the Pleistocene, we have recently shown that marine diatom communities evolved slowly through gradual changes over the past 1.5 million years. Identifying the causes of this ecological stability is key for understanding the mechanisms that control the tempo and mode of community evolution.

Controls on diatom biogeography in the ocean.

The extent to which the spatial distribution of marine planktonic microbes is controlled by local environmental selection or dispersal is poorly understood. Our ability to separate the effects of these two biogeographic controls is limited by the enormous environmental variability both in space and through time. To circumvent this limitation, we analyzed fossil diatom assemblages over the past ~1.

The role of nutricline depth in regulating the ocean carbon cycle.

Carbon uptake by marine phytoplankton, and its export as organic matter to the ocean interior (i.e., the "biological pump"), lowers the partial pressure of carbon dioxide (pCO(2)) in the upper ocean and facilitates the diffusive drawdown of atmospheric CO(2).

Identification of flavonoid diglycosides in several genotypes of asparagus from the Huétor-Tájar population variety.

The qualitative and quantitative composition of flavonoids from the Huétor-Tájar population variety of asparagus (commonly known as " triguero") was investigated. Flavonoids were analyzed by reversed-phase high-performance liquid chromatography-diode array detection (HPLC-DAD). Liquid chromatography-mass spectrometry (LC-MS) under identical HPLC conditions was used to verify the identities of the flavonoid glycosides from triguero asparagus.

Invariant scaling of phytoplankton abundance and cell size in contrasting marine environments.

Scaling relationships such as the variation of population abundance with body size provide links between individual organisms and ecosystem functioning. Previous work, in marine pelagic ecosystems, has focused on the relationship between total phytoplankton abundance and the assemblage mean cell size. However, the relationship between specific population abundance and cell size in marine phytoplankton has received little attention.