What is the metabolic state of the oligotrophic ocean? A debate

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Annual Reviews for personal use, not for redistribution. The definitive version was published in Annual Review of Marine Science 5 (2013):525-533, doi:10.1146/annurev-marine-121211-172331.For more than a decade there has been controversy in oceanography regarding the metabolic state of the oligotrophic gyres of the open sea. Here we review background on this controversy, commenting on several issues to set the context for a moderated debate between two groups of scientists. In a companion paper, Williams et al (2013) take the view that the oligotrophic subtropical gyres of the global ocean exhibit a state of net autotrophy, that is, the gross primary production (GPP) exceeds community respiration (R), when averaged over some suitably extensive region and over a long duration. Duarte et al (2013) take the opposite view, that the oligotrophic subtropical gyres are net heterotrophic, with R exceeding the GPP. This idea -- that large, remote areas of the upper ocean could be net heterotrophic raises of host of fundamental scientific questions about the metabolic processes of photosynthesis and respiration that underlie ocean ecology and global biogeochemistry. The question remains unresolved, in part, because the net state is finely balanced between large opposing fluxes and most current measurements have large uncertainties. This challenging question must be studied against the background of large, anthropogenically-driven changes in ocean ecology and biogeochemistry Current trends of anthropogenic change make it an urgent problem to solve and also greatly complicate finding that solution.The authors acknowledge support from the U.S. National Science Foundation through the Center for Microbial Oceanography Research and Education (C-MORE), an NSF Science and Technology Center (EF-0424599), and NSF award OPP 0823101 (Palmer LTER) from the Antarctic Organisms and Ecosystems Program

Extensive cross-disciplinary analysis of biological and chemical control of Calanus finmarchicus reproduction during an aldehyde forming diatom bloom in mesocosms

Egg and faecal pellet production and egg hatching success of the calanoid copepod Calanus finmarchicus were monitored over a period of 14 days (14-28 April, 2008) while fed water from 4 differently treated mesocosms and ambient water. Two of the mesocosms used were inoculated with the polyunsaturated aldehyde (PUA)-producing diatom Skeletonema marinoi, while 2 received only nutrient additions with or without silica. The mesocosms developed blooms of S. marinoi, mixed diatoms or the haptophyte Phaeocystis pouchetii, respectively. Faecal pellet production of C. finmarchicus increased with increasing food availability. Egg production increased with time in all mesocosms to a maximum single female production of 232 eggs female(-1) day(-1) (average of 90 eggs female(-1) day(-1)) and followed the development of ciliates and P. pouchetii, but was not affected by the observed high (up to 15 nmol L(-1)) PUA production potential of the phytoplankton. The hatching success of the eggs produced on the mesocosm diets was high (78-96%) and was not affected by either aldehydes in the maternal diet or exposure to the dissolved aldehydes in the water

Screening For Lipids From Marine Microalgae Using Nile Red

The fluorescent stain Nile Red has been used extensively for the quantification of lipids in phytoplankton, including microalgae, because it preferentially stains neutral lipids and it is economical and sensitive to use for screening purposes. Although its basic application has not changed for several decades, recent improvements have been made to improve its utility across applications. Here we describe additional refinements in its application and interpretation as a high-throughput method for the rapid quantification of neutral lipids in liquid cultures of marine phytoplankton. Specifically we address (1) interspecies comparisons, (2) fluorescence excitation and emission wavelengths, and (3) the time course of the Nile Red signal in the context of using bulk or cell-specific fluorescence to quantify neutral lipids of live or preserved cells. We show that with proper caution in its interpretation across species and physiological states the quantity of lipid in hundreds of small volume samples can be reliably assessed daily using a refined Nile Red protocol