Decoding the Lives of Marine Wildlife: Using the Argos Satellite System to Understand the Ocean

The Argos satellite system provides a worldwide network of ocean-based data allowing scientists to decipher more and more about the cryptic nature of the ocean and the wildlife found within it. Part Three of Three. Click here for Part One and Part Two of this series.

Far above the Earth’s surface, a satellite equipped with an Argos instrument passes over the Atlantic Ocean near Sable Island off the coast of Nova Scotia. Below, a grey seal tagged with a transmitter pops to the ocean’s surface, sending a stream of short messages to the system. Within a matter of seconds, data on the seal’s migratory pattern and environmental conditions are ready for transmission to global processing centers. This interaction between satellite and receiver operates as part of the international Argos system.

Argos, a worldwide data collection and location system (DCS), began collecting and networking ocean-based data in 1978. Initially created by the French Space Agency (CNES), NASA and the National Oceanic and Atmospheric Administration (NOAA), it has evolved into a global scientific network.

A grey seal tagged with an Argos satellite transmitter and Vemco Mobile Transceiver on the Magdalen Islands. Image Credit: Damian C. Lidgard

A grey seal tagged with an Argos satellite transmitter and Vemco Mobile Transceiver on the Magdalen Islands. Image Credit: Damian C. Lidgard

The Argos system hosts a network of 22,000 autonomous platforms that collect data for more than 2,000 projects in more than 100 countries. The low-orbiting polar satellites deliver uplinked data to Global and Regional Processing Centers (GPCs and RPCs), providing worldwide coverage.

Scientists can access this network of data to aid in understanding migratory paths, ocean conditions and the impact of climate change and anthropogenic development on marine wildlife. Argos uplinks data from myriad platforms, including gliders, buoys, Argos profilers and marine wildlife tagged by the Ocean Tracking Network (OTN).

OTN is a global research, technology and scientific partnership platform based in Canada, which uses the Argos satellite technology to track the migratory pathways and feeding behaviors of 100 keystone species in the Pacific, Arctic and Atlantic. Keystone species are crucial to an ecosystem since other species directly and indirectly depend upon them for survival. For example, most keystone species are predators that keep the populations of prey species in check, ensuring a healthy balance within an established food chain. The removal or depletion of these animals leads to drastic changes in an ecosystem.

According to OTN Executive Director Fred Whoriskey, the organization uses the Argos satellite system to retrieve data from animals with satellite tags. Animals that break water periodically, such as grey seals, are tagged atop their heads allowing for real-time data collection. For other marine animals, such as fish, OTN uses specialized pop-up satellite tags. These tags store data on internal memories until they release from the animal on a pre-programmed date or pop up to the surface once the animal dies.

“Marine mammals are a challenge to study,” explains Damian Lidgard, a research associate with OTN and instructor in the Department of Biology at Dalhousie University. It is fairly easy for scientists to collect data on behavior, physiology and life history of marine mammals that come to land to breed, “but once they leave and enter the marine environment, their life becomes more of a mystery.” For this reason, “marine mammal science progresses when new technologies (like Argos) appear.”

The tracking pattern of five grey seals from July 2015 to May 2016 tagged on the Magdalen Islands in 2015. Image Credit: Damian C. Lidgard

The tracking pattern of five grey seals from July 2015 to May 2016 tagged on the Magdalen Islands in 2015. Image Credit: Damian C. Lidgard

OTN relies on the Argos tracking and satellite systems and researchers often tap into their data streams to correlate animal movements with oceanographic data, or to provide models of environmental conditions that can be linked to migration patterns.

Despite similar monikers, Argos and the Argo Float System are disparate technologies. Argos consists of an interaction of three core subsystems: Platform Transmitter Terminals (PTTs), the Space Segment, and the Ground Segment. PTTs are attached to transmitting sensors and are specifically adapted for their platforms, whether that be glaciers, ships, migratory birds or grey seals. The OTN tags attached to marine animals are one example of PTTs. The Argo float system represents another component of the subsystem, which as of Nov. 11, 2016, consisted of a global array of 3,739 profiling floats that measure either ocean temperature, pressure, salinity, oxygen or chlorophyll a levels, which is a proxy for phytoplankton presence.

The Space Segment consists of Argos instruments attached to satellites. These instruments relay messages from PTTs, such as the OTN monitoring tags and the Argo floats, in real time while also storing data like tape recorders to later deliver to the nearest of either three Global Processing Centers (GPCs) or 12 Regional Processing Centers (RPCs). Researchers can then access data concerning the animal’s location and environment from a GPC database.

The OTN team recently began using these tracking technologies in a novel way. They found that Bluetooth connections between tag types can reveal unique interactions between species including prey type, foraging locations and environmental conditions. They plan to test this “bioprobe” tagging on the Sable Island grey seal, an important marine keystone species. Using this technology provides scientists with vital data concerning marine wildlife that could inform future management strategies and help provide a better understanding of the impact that global climate change and anthropogenic development have on the ocean.

The Argos network of data collected from marine tags and the Argo float system combine to fulfill OTN’s vision of enabling “international sustainable management of valued aquatic species by providing knowledge of animal movements, survival, and habitats, and of how all are linked to environmental conditions.”

“Perhaps the greatest technological development for marine mammalogists is the Argos satellite system,” said Lidgard. It has become the workhorse of marine mammal science and led to a clearer understanding of where these animals go and what they do, particularly for migratory species such as the northern fur seal, arctic species and species that inhabit areas where humans are unable to reach, such as the southern elephant seal in the Antarctic. The Argos system has “significantly contributed to the collection of oceanographic data in these regions and improved oceanographic models,” he adds. However, the costs of sending data and the technology required significantly limits the system from becoming a truly global data sharing network for marine scientists.

Kayla Townsley is an undergraduate at Portland State University majoring in molecular biology and is a contributing writer with IEEE Earthzine.

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