Cover of the OOI Special Issue in Oceanography MagazineOOI Special Issue Student Summaries

Oceanography Magazine’s 2018 Special Issue on the Ocean Observatories Initiative featured a number of articles on the early research results from the OOI. To better understand how these stories might resonate with undergraduates, we asked two students to summarize their key takeaways from several of the articles. These example summaries can be used in lessons by faculty to help introduce these specific topics.  These examples also provide a case study on how certain aspects of cutting-edge research might be more relevant or engaging for students than others.

The following summaries were written by Devin Busono and Kasey Walsh in the summer of 2019.


Warm Blobs

Typical ocean temperatures can be affected by long term cyclical variations such as the ENSO (El Niño/ La Niña) and Pacific Decadal Oscillation (PDO). Three OOI arrays off the Northwest Pacific are set up to track these long-term changes. In the winter of 2013-2014 the atmospheric Jetstream shifted bringing a mass of warm water, “warm blob”, near the shore. The warm water reached over 4oC (about 7oF) warmer than average. Such drastic changes in temperature caused issues such as the growing of toxic algae.

From the winter season of 2014 through the fall of 2017, the arrays tracked the patterns of this warm blob. Data from the sensors showed that when the warm blob reached the endurance array anomalies were strongest within the first 100m but were seen through 500m depth (Figure 3 page 94). The gap in data between 2016 and 2017 was due to a broken profiler. The strength of the anomalies seen in the winter 2015-2016 was because of the El Niño phase at that time. Although at some points, the water was cooler than normal, this is likely caused by upwelling, an annual physical process that brings cold bottom water to the surface. Based on this figure, it is also shown that the cooler periods were not as intense or as long as the warm events.

The biology of the ocean is greatly influenced by temperature. Many organisms have specific temperature windows in which they can survive, and smaller windows in which their growth thrives. For a certain toxic diatom, the warm water enhanced their growth allowing for the creation of a harmful algal bloom (HAB). HABs have caused issues along many coasts of the United States and in the Great Lakes. General concerns include water contamination, production of toxins that harm humans, and causing illness or death of various organisms which can impact fisheries. Mediation can cost a lot of money, if it is feasible, and in some areas has become a platform for political campaigns. In this area, the warm blob and subsequent diatom bloom led to a release of domoic acid which delayed the opening of, or completely shut down the Dungeness crab fishery, valued at about $170 million. The warm blob also decreased the abundance of euphausiids which are an important food source for salmon. Salmon is an important part of the food webs in this ecosystem, and is economically important to humans. Tracking these temperature patterns is important for understanding how biology will react and how humans will be impacted.

Barth, J.A., J.P. Fram, E.P. Dever, C.M. Risien, C.E. Wingard, R.W. Collier, and T.D. Kearney. 2018. Warm blobs, low-oxygen events, and an eclipse: The Ocean Observatories Initiative Endurance Array captures them all. Oceanography 31(1):90–97, https://doi.org/10.5670/oceanog.2018.114.


A Tale of Two Eruptions

Underwater volcanic eruptions are responsible for creating island groups such as Hawaii and Indonesia, exchanging heat and chemicals, and supporting biological communities. Despite this, little is known about the dynamic processes involved in mid-ocean ridge eruptions. Specifically, the association between underwater seismic activity and submarine volcanic eruptions is not well understood.

When underwater volcanoes erupt, seismic signals are usually detected as well. However, the spatiotemporal relationship between the seismic signals and the eruptions are unable to be properly mapped because real-time data transmission about the seafloor requires tools that are both costly and hard to deploy.

The implementation of the Axial Seamount proved monumental when in 2015, an eruption there provided in situ real-time geophysical data collected during a mid-ocean ridge eruption for the first time. This data led to the discovery of the locations of the seismic signals associated with lava eruptions on the seafloor, though the cause of the signals is not yet known.

Guided by this finding, researchers revisited data from an eruption a decade earlier with a fundamental new view of seafloor spreading at fast-spreading ridges. Even though cabled observatories like the Axial Sea Mount are bound to a specific location, their results can have significant implications for understanding how mid-ocean ridges erupt in different systems, such as the East Pacific Rise during its eruption in 2006. Through this scientific breakthrough, the differences in tremor timings between the Axial eruption and the East Pacific eruption were used to infer the cause of the eruptions.

Tolstoy, M., W.S.D. Wilcock, Y.J. Tan, and F. Waldhauser. 2018. A tale of two eruptions: How data from Axial Seamount led to a discovery on the East Pacific Rise. Oceanography 31(1):124–125, https://doi.org/10.5670/oceanog.2018.118.


Biological Carbon Pump

Currently, at the forefront of environmental issues is the global warming crisis. This problem, exacerbated by the presence of CO­2­ in the atmosphere, causes heat to be trapped within the earth’s atmosphere, melting polar ice caps and contributing to the rising sea level worldwide.

To better understand this global warming phenomenon, it is imperative to understand how the ocean plays a role in the carbon cycle via sequestration. Photosynthetic organisms in the ocean make use of the CO2 that makes its way into the surface layers of the ocean, fixing it into organic carbons (sugars) through photosynthesis. These fast sinking organisms are then transported into the deep ocean, where if they sink below the deepest layers of winter ventilation depths, they and any carbon they may convert into organic carbon can avoid being brought back up near the surface during winter ventilation

The OOI allows for the measuring of this data by providing year round simultaneous data collection and observations in this traditionally under-sampled region. By measuring the dissolved oxygen levels via the OOI array, we can infer the location of these organisms and the carbon they sequester. A lower level of dissolved oxygen would mean that more cellular respiration is occurring, and that CO2 is being released by these organisms into the water, whereas a higher level of dissolved oxygen would mean that less cellular respiration is occurring, and carbon is more successfully being stored in these organisms.

Palevsky, H.I., and D.P. Nicholson. 2018. The North Atlantic biological pump: Insights from the Ocean Observatories Initiative Irminger Sea Array. Oceanography31(1):42–49, https://doi.org/10.5670/oceanog.2018.108.


Earthquake activity of the Cascadia subduction zone

Earthquakes occur when Earth’s tectonic plates collide. A subduction zone is when two plates collide and one is forced underneath the other. The Cascadia subduction zone is the boundary between the North American plate and Juan de Fuca plate, it occurs off the coast of Oregon. Although it currently does not have regular activity that affects humans, researchers predict built up tension could cause at least a magnitude 8 earthquake. For comparison, in 2010 Haiti suffered from a magnitude 7 earthquake which subsequently had multiple aftershocks killing approximately 250,000 people (world vision). Although this subduction zone, and others, are located underneath the ocean most technology is focused on measuring, predicting, and understanding earthquakes below land.

To bridge this gap, the OOI has begun measuring earthquakes offshore near the Cascadia subduction zone. Marine fauna, water depth, currents and crust thickness make seismic detection in the water difficult. To help protect the instruments, the OOI buried them in the sand. The sensors have measured earthquakes undetectable on land with current technology.

Large magnitude subduction earthquakes are often preceded by smaller earthquakes. With the OOI researchers are able to detect more earthquake activity and may be able to recognize patterns in plate movement. Detecting an earthquake cluster that leads up to a magnitude 8 could lead to a public warning allowing people time to prepare for such an event.

Tréhu, A.M., W.S.D. Wilcock, R. Hilmo, P. Bodin, J. Connolly, E.C. Roland, and J. Braunmiller. 2018. The role of the Ocean Observatories Initiative in monitoring the offshore earthquake activity of the Cascadia subduction zone. Oceanography 31(1):104–113, https://doi.org/10.5670/oceanog.2018.116.


Eclipse

Marine science is almost always an interdisciplinary subject. The OOI’s endurance array contains sensors for water temperature, salinity, dissolved oxygen, and chlorophyll fluorescence, as well as atmospheric sensors. Together, the array gives researches an insight into marine physics, chemistry, and biology. As a result, it allows scientists to answer old questions that could not previously be answered and even ask new questions they did not know to ask. In the case of the August 21, 2017 eclipse the array allowed scientists to track the reaction of zooplankton to the eclipse.

Zooplankton, are near the bottom of most food webs and serve as an important food source, directly or indirectly, for several economically important fish. Many of them are diel migrators, meaning they travel to the surface of the ocean at night and down to various depths depending on species during the day. Reasons for this includes predator avoidance and convenience of eating algae. Bioacoustic sensors revealed that zooplankton reacted to the eclipse by beginning their typical nightly migration to the surface (figure 6 page 96). The sensors were able to determine when the zooplankton began their migration and the speed at which they did.

The endurance array was not placed in the area to track a single eclipse. This array tracks long term oceanographic and atmospheric cycles along with other day to day measurements and events. However, because it was there researchers were able to see how such small, yet important organisms react to changes in their environment, even on a time span of only 45 minutes. Although it was known zooplankton would react to the eclipse, it was important to be able to track the organisms continuously. Future events could lead to the discovery of something by these OOI arrays which is currently unknown because of established research methods.

Barth, J.A., J.P. Fram, E.P. Dever, C.M. Risien, C.E. Wingard, R.W. Collier, and T.D. Kearney. 2018. Warm blobs, low-oxygen events, and an eclipse: The Ocean Observatories Initiative Endurance Array captures them all. Oceanography 31(1):90–97, https://doi.org/10.5670/oceanog.2018.114.


Hypoxia

Hypoxia is an inadequate amount of dissolved oxygen in the water. This can cause harm to the marine organisms that live in that area. Among other areas, hypoxic conditions occur in areas of strong upwelling, like off the coast of Oregon. Upwelling is a physical process in which nutrients typically found near the bottom of the ocean are brought to the surface. This nutrient injection along with ample sunlight cause extensive plankton growth. Plankton blooms are followed by a large sinking event of decaying organic matter through death and predation which leads to hypoxic conditions near the bottom. The continental shelf off of Oregon has become more hypoxic in recent years resulting in the die-offs of invertebrates and migration of fish away from the area.

To help understand this phenomenon the OOI placed the Endurance Array on the continental shelf and slope in the Northeast Pacific. Sensors in this array span various depths and have instruments that track temperature, salinity, dissolved oxygen, and chlorophyll fluorescence. There are also sensors on the surface of the ocean to track atmospheric changes and help researchers understand how the air and ocean interact. Together they have allowed researchers to track hypoxic and severe hypoxic events along with the temperatures and depths they occur at. The OOI sensors tracked a pattern of hypoxia when the wind blows to the south and bottom temperatures decrease (Figure 4 Page 95).

Tracking hypoxic events is important for understanding the ocean, but also for the people that rely on this area for their careers. In 2014, the Dungeness crab fishery was valued at approximately $170 million, and in July 2017 there was a die-off of these crabs due to severe hypoxia. The effects of hypoxia, especially if prolonged, could have a negative impact on the local economy and employment rates. Using the OOI to understand why this area of the California Current is becoming more hypoxic is important for the organisms that live there as well as the people that rely on them.

Barth, J.A., J.P. Fram, E.P. Dever, C.M. Risien, C.E. Wingard, R.W. Collier, and T.D. Kearney. 2018. Warm blobs, low-oxygen events, and an eclipse: The Ocean Observatories Initiative Endurance Array captures them all. Oceanography 31(1):90–97, https://doi.org/10.5670/oceanog.2018.114.