Functional Diversity of Marine Eukaryotic Phytoplankton and Their Contributions to Carbon and Nitrogen Cycling

Friday, Apr 24, 2015
The Research Vessel "Endeavor" featuring Jimmy' Qixing Ji (2014) for scale.

The Research Vessel "Endeavor" featuring Jimmy' Qixing Ji (2014) for scale.

On two ~25 day long, trans-Atlantic cruises, members of the Ward Lab ventured to the subarctic ocean. In collaboration with the Sigman Lab (Princeton University) they studied the contribution of pico- to meso-sized plankton to the cycling of carbon and nitrogen. These late summer (2013) and spring (2014) subarctic North Atlantic cruises followed-up the cruises in the western subtropical gyre (Sargasso Sea) and provided the opportunity to compare the roles of plankton functional groups between two very different ocean biomes.

The Princeton science team consisted of graduate students Jessica Lueders-Dumont, Keiran Swart, Dario Marconi (2013), 'Jimmy' Qixing Ji (2014) and Andrew Babbin (2014), post-docs Sarah Fawcett and Nicolas Van Oostende, and principal investigator Bess Ward. Bror Jonsson provided real-time remote sensing imagery to guide the seagoing team towards the phytoplankton bloom patches. Near real-time nutrient measurements were determined by Malcolm Woodward of the Plymouth Marine Laboratory, UK (2013) and Amandine Sabadel of the University of Otago, NZ (2013) and by Andrew Babbin with the help of Aimée Babbin in 2014. Jeff Hoffman of the Greg J. Venter Institute assisted with the collection of RNA/DNA of bacterial and phytoplankton communities and performed large volume filtration for the collection of viral particles.

The Ward Team
The Ward Team: (L to R) Andrew Babbin (2014), Ship Technician Erich Gruebel, Aimée Babbin, Bess Ward, Jessica Lueders-Dumont, Sarah Fawcett, Jeff Hoffman, Nicolas Van Oostende, Keiran Swart, and 'Jimmy' Qixing Ji (2014).

The overall goal of this field study was to investigate the taxonomic, genetic and functional diversity of eukaryotic phytoplankton and to link this diversity and assemblage composition to the carbon and nitrogen biogeochemistry of the surface ocean.

Kieran Swarts and Sarah Fawcett late night "in situ" pumping.

Kieran Swart and Sarah Fawcett late night "in situ" pumping.

Sampling and experimentation on board the R/V Endeavor was greatly facilitated by the outstanding leadership and highly professional and amicable crew (and the delicious meals!). As you can imagine the North Atlantic is a very different animal in late summer than it is in spring, when sunny calm seas had to make way for storms and 0 °C water. On our way from Morehead city, NC (late summer) or Narragansett, RI (spring) a 1000 m deep CTD cast was performed every day at dawn to collect various size fractions of phytoplankton and determine primary production rates, as well as chlorophyll a, nutrient concentrations and C and N isotopic composition. Along the way northeastwards, surface samples for nutrients, particulate organic matter, chlorophyll a and dissolved inorganic carbon were collected every 6 hours (why waste this valuable seawater?).

The 'bators' secured on deck.

The 'bators' secured on deck.

The other objective of the transect was to reach two so-called process stations bordering the subarctic Atlantic. This is where the round-the-clock scientific action took place. Having worked on different time shifts during several weeks, the team was more than ready! Multiple incubation experiments were performed to measure inorganic carbon and nitrogen uptake rates by different phytoplankton size groups and to determine the rates of nitrification in the surface water column. Also part of the fun, were net tows to collect larger (even multi cellular, yes) plankton for isotopic analysis as well as in situ filtration of size-fractionated particulate material using submersible pumps. Once the team was all filtered-out (most of the sampled seawater was eventually returned to the ocean) our ports of call were the lovely Ponta Delgada (Azores, summer) and the northern Reykjavik (Iceland, spring?). Even oceanographers are happy to smell land after hard and fulfilling work at sea.

"It's as cold as ice in iceberg alley," observed on-board scientists.

"It's as cold as ice in iceberg alley," observed on-board scientists.

 

Hoisting sea-water samples.

Hoisting sea-water samples.

 

One of the many sunsets in late summer North Atlantic.

One of the many sunsets in late summer North Atlantic.

 

One of two sunsets in the subarctic North Atlantic.

One of two sunsets in the spring North Atlantic.

 

Nicolas Van Oostende and Bess Ward.

Nicolas Van Oostende and Bess Ward.

 

Jessica Lueders-Dumont, Aimée Babbin, and Andrew Babbin.

 

Flying ship flags.

Flying ship flags.