Nicole Poulton is a senior research scientist and the director of the Center for Aquatic Cytometry at Bigelow Laboratory for Ocean Sciences (BLOS). On Tuesday, July 23, before an audience of about 130 at the Opera House of Boothbay Harbor, she delivered an educational lecture, “Flow Cytometry (FC) – Revealing the Microscopic Wonders in a Drop of Sea Water.”

Poulton came to Bigelow in 2001 as a post-doctoral fellow, after receiving her Ph.D. in biological oceanography from MIT and Woods Hole Oceanographic Institution Joint Program. She began her lecture by sharing a childhood photo from the coast of Lake Michigan, stating she was interested in aquatic ecosystems from an early age, but it wasn’t until her family moved to the South Pacific that she understood, “how big the ocean actually is. A single drop of ocean water on a slide is teeming with life.” She presented a slide showing that one drop of ocean water contains 50,000-500,000 bacteria and viruses, 500-5,000 phytoplankton, and one to five small zooplankton.

“With up to a million microscopic organisms in a drop of seawater, sorting them can be a huge obstacle to studying them. FC is a method that allows scientists to detect microbes and other small particles in water using laser light. BLOS was one of the first places to examine, count and study phytoplankton using the tool. Co-founder Clarice Yentsch championed its use and established the first center dedicated to FC for aquatic sciences, creating a multitude of research directions and opportunities,” she wrote in “Transect” (Summer 2024).

Phytoplankton contain pigments and, by adding DNA-binding dyes and probes, we can identify various species and detect chlorophyll, she said. FC is a rapid method of counting and characterizing particles in a fluid using laser light (particle scanner and fluorescence) to measure cells. It has many applications in environmental and biomedical fields. It can analyze 1,000 to 100,000 particles per second.

Innovation from Bigelow took FC a step further. Chris Sieracki, Michael Sieracki and Charles Yentsch added a microscope to the FC to create FlowCAM, an imaging-in-flow system for automated analysis of marine phytoplankton – the first in the world.

“The FlowCAM revolutionized the tedious and slow process of manual examination of phytoplankton via microscope by providing a semi-automated method to rapidly count, measure and analyze individual cells and particles in a fluid sample using digital images,” said a slide during the talk. 

Poulton showed a video of how fast the laser triggers the camera to take an image, tuned for fluorescence and size detection, amassing a ton of data she hopes within the next 50 years, machine learning algorithms and AI will help index/identify all the microbes in real time speeds, and analyze density counts.

“As I look ahead to the coming decades, I think the cutting-edge work of BLOS on FC will continue to accelerate science and the insights it provides about our world,” she wrote. “One advancement made possible by FC, for example, was the discovery of a bacterium known as Prochlorococcus – the planet’s smallest and most abundant photosynthetic organism, which produces about 20% of the oxygen we breathe.” Known as “little greens,” a marine cyanobacterium, it is estimated there a billion, billion, billion (that’s 10 to the 27) of them in the ocean, discovered by Penny Chisholm at MIT in1988.

Since getting its first FC device in the early 1980s, BLOS has hosted over a dozen FC workshops for scientists.

In town, Poulton has been sampling seawater weekly or bi-weekly at McKown Point since 2001. The Booth Bay time series has helped scientists understand how things are moving through the food web, predator-prey dynamics, and phenology shifts as the waters of the Gulf of Maine are rapidly changing.

Efforts are underway to measure nutrient flux from the lower ocean to the upper 200 meters via a NASA satellite launched in February, and FC can be used to validate the satellite data. “Flow cytometry is constantly advancing, and the impact and applications of the field continue to grow. Most recently, I’ve been working with colleagues in the industry and at BLOS to use FC to image, sort and isolate aquatic organisms for downstream analysis. I’m also working with partners at other institutions to develop a tool for counting and measuring even the smallest types of microplastics.”

Poulton took questions from an engaged audience following the presentation. Poulton’s lecture will be posted on BLOS’s YouTube channel. The series of lectures, sponsored by HM Payson, continues July 30 with senior research scientist Ramunas Stepanauskas, presenting “Single Cell Genomics: Understanding the Ocean’s Potential, One Cell at a Time,” and on Aug. 6, the series closes with “Satellite Oceanography: Unlocking Insights by Analyzing the Big Picture,” by senior research scientist Catherine Mitchell. Space is limited, and free registration is required.