Marine phytoplankton in the northern Benguela upwelling system (nBUS) serve as a food and energy source fuelling marine food webs at higher trophic levels and thereby support a lucrative fisheries industry that sustain local economies in Namibia. Microscopic and chemotaxonomic analyses are among the most commonly used techniques for routine phytoplankton community analysis and monitoring. However, traditional in situ sampling...

Fluorescence quantum yield is a powerful tool for assessing phytoplankton photophysiology and photosynthetic efficiency, but there is a paucity of in situ studies. Here we present the first wavelength‐specific fluorescence quantum yield data from high spatial and temporal resolution real‐time measurements made in the Southern Ocean. This dataset represents both winter and summer conditions across a broad latitudinal range of t...

Active chlorophyll-a fluorescence was measured during five summer research cruises (2008 – 2016), spanning the Atlantic sector of the Southern Ocean. This unique data set provides information for assessing zonal, inter-annual and intra-seasonal variability (early versus late summer) of photosynthetic efficiency (F v /F m ). The zonal variability of F v /F m showed a typical latitudinal decline from a maximum in the Polar Front...

Measuring plankton and associated variables as part of ocean time-series stations has the potential to revolutionize our understanding of ocean biology and ecology and their ties to ocean biogeochemistry. It will open temporal scales (e.g., resolving diel cycles) not typically sampled as a function of depth. In this review we motivate the addition of biological measurements to time-series sites by detailing science questions t...

Central to the Southern Ocean's role in setting atmospheric CO 2 is the seasonal alternation between upward mixing of nutrients and their subsequent consumption by phytoplankton. Active nutrient cycling within the mixed layer, including the release of ammonium (NH 4 + ) and its removal by phytoplankton and nitrifiers, also affects Southern Ocean CO 2 drawdown, yet remains poorly understood. We conducted kinetics experiments ac...

Phytoplankton photosynthetic physiology can be investigated through single-turnover variable chlorophyll fluorescence (ST-ChlF) approaches, which carry unique potential to autonomously collect data at high spatial and temporal resolution. Over the past decades, significant progress has been made in the development and application of ST-ChlF methods in aquatic ecosystems, and in the interpretation of the resulting observations....

Active fluorescence measurements can provide rapid, non‐intrusive estimates of phytoplankton primary production at high spatial and temporal resolution, but there is uncertainty in converting from electrons to ecologically relevant rates of CO 2 assimilation. In this study, we examine the light‐dependent rates of photosynthetic electron transport and 13 C‐uptake in the Atlantic sector of the Southern Ocean to derive a conversi...