Biosensing Lagrangian Instrumentation and Nitrogen Cycling Systems (BioLINCS)
Tracking nitrogen in the open ocean

MBARI is a partner institution in the Center for Microbial Oceanography: Research and Education (C-MORE), a National Science Foundation-sponsored Science and Technology Center established in 2006. Our contribution to the shared goal of facilitating a deeper understanding of the biological and ecological diversity of marine microorganisms includes providing our state-of-the-art technology and unique scientific and engineering expertise.

On the BioLINCS cruise, MBARI personnel will provide engineering and research support for the operation of our Environmental Sample Processor (ESP). The data gathered by the ESP will enable the cruise’s science team to study how microscopic organisms in the open ocean take up and transform nitrogen compounds in the open ocean.

About the Cruise

During the BioLINCS cruise, the research vessel Kilo Moana will spend 14 days in a patch of open ocean about 320 kilometers north of Oahu. Conditions in this area are similar to those at Station ALOHA, a mid-ocean research site that for almost 25 years has provided scientists with a wealth of background information about the chemistry, biology, and currents of the open Pacific.

The science personnel on board the Kilo Moana will conduct a number of experiments to study marine bacteria and archaea. Archaea are single-celled organisms that look similar to bacteria, but are in an entirely separate biological domain. The BioLINCS team is particularly interested in how these microbes take up nitrogen and convert it into different chemical forms through the process called nitrogen cycling.

These experiments involve deploying a variety of research equipment in the ocean, and allowing this equipment to drift with the currents for days at a time. Some of these drifting (“Lagrangian”) instruments are incubators, which allow scientists to run experiments on microbes in the environment from which the microbes were collected.

One of the largest of these drifting instruments is MBARI's Environmental Sample Processor (ESP). The ESP will allow researchers to use the DNA of marine microbes to figure out what organisms are present. It will also be used to determine the abundances of genes necessary for taking up dissolved nitrogen gas from seawater—a process known as “nitrogen fixation.”

While the Kilo Moana follows this array of drifting instruments, the science team will collect water samples at various depths and acquire physical, chemical, and biological data throughout the water column. They will also conduct incubation experiments on board the ship using the collected seawater. The water-column data, shipboard measurements, and incubation experiments will help the BioLINCS team to understand the biological-chemical links (or “biogeochemical processes”) occurring in the water column. The water-column data will also become part of the long-term scientific record for Station ALOHA.

About the Science

MBARI's Roman Marin prepares for a deployment of the second generation ESP in the Monterey Bay. On this cruise, researchers will be testing a new version of the ESP, which can collect data while drifting with the ocean currents for days at a time.

Conditions around Station ALOHA are typical of the mid-Pacific, with extremely clear water and low populations of microscopic photosynthetic organisms, or "primary producers," which form the basis for marine food webs. Primary producers are relatively sparse in the open ocean because the surface water contains very low concentrations of the nutrients that they need to grow. Oceanographers use the term “oligotrophic” to describe such low-nutrient waters, thus the acronym for Station ALOHA: "A Long-term Oligotrophic Habitat Assessment."

One of the most important nutrients for primary producers is nitrogen, which can take several different chemical forms (nitrate, nitrite, ammonium, etc.). Different types of marine microbes use different forms of nitrogen as “fertilizer.“

In the open ocean, the waste from one group of microbes typically serves as an energy source or as a nutrient for another group of microbes. This biologically-controlled process of converting compounds from one form to another is called “biogeochemical cycling.” During the BioLINCS cruise, researchers will focus on learning about the biogeochemical cycling of nitrogen compounds.

Nitrogen gas is the only form of nitrogen that is available in high concentrations near the sea surface. However, only a few organisms exist that can take up nitrogen gas. These organisms “fix” nitrogen, converting nitrogen gas into energy-rich, “reduced” forms of nitrogen, such as ammonium, which can be utilized by other organisms. Thus nitrogen-fixing organisms can be thought of as providing fertilizer for other organisms. In fact, nitrogen fixation by microbes fuels most of the primary production in the surface waters of the open ocean.

In addition to being used by primary producers, nitrogen compounds are also nutrients for other marine microbes that do not necessarily rely on sunlight and photosynthesis for survival. These microbes get their energy not from light, but rather by absorbing reduced chemicals directly from seawater. In doing so, they convert these compounds from one chemical form to another. This is analogous to animals eating food (which contains reduced carbon) and converting it to carbon dioxide (an oxidized form of carbon), which is then released to the atmosphere.

Although population densities of primary producers are relatively low in open-ocean areas, these areas cover much of Earth’s surface. As the dominant organisms in this immense environment, marine microbes are critically important in maintaining the climate of Earth. They also supply a significant amount of the oxygen in our atmosphere.

In addition to providing oxygen, marine microbes have other important effects on the atmosphere. Some of them release nitrous oxide (N2O), which is a greenhouse gas. Others release compounds such as dimethyl sulfide (DMS), which influence the formation of clouds.

Because of all these interactions between the open ocean and the atmosphere, studying the nitrogen cycle of the open ocean is more than an academic exercise. The results from the BioLINCS experiments could help improve computer models that predict how life in the ocean will respond to increasing carbon dioxide in the atmosphere, global warming, and ocean acidification.

Read more about marine microbes

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