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Meet the Zooplankton: Meganyctiphanes norvegica

This is Jim Fiorendino, your host for On the Ocean. Only slightly larger than a paperclip, the northern krill Meganyctiphanes norvegica might be small in stature, but it plays a big role in marine ecosystems. Meganyctiphanes norvegica is a small, shrimp-like creature found primarily in the western Mediterranean Sea and North Atlantic ocean between 30 and 80 degrees north latitude. These crustaceans grow to between 22 and 45 mm in length, and feed on other tiny organisms like phytoplankton as well as decomposing material. Typically, meganyctiphanes norvegica can be found between 100 and 400 m depths in the ocean, but they have been caught at depths as great as 1500 m. Meganyctiphanes is known to migrate vertically, moving to surface waters at night to feed.

Image from: http://www.arcodiv.org/watercolumn/euphausiid/Meganyctiphanes_norvegica.html

Meganyctiphanes norvegica is an important prey species for many marine animals. Fish, seabirds, squid, and whales all feed on Northern krill. Unfortunately, populations of Northern krill have been declining in recent years. The cause of the decline of Meganyctiphanes norvegica populations is unknown, but could be related to human activity, climate change, or increased predation. Scientists are currently trying to understand what is driving this change, and how marine ecosystems that depend on Meganyctiphanes norvegica will be impacted. One major issue facing meganyctiphanes norvegica is climate change. Meganyctiphanes norvegica is dependent on ice. Ice offers both protection from predators and an all-you-can-eat buffett in the form of algae and other small plankton growing on the underside of ice sheets. As temperatures rise and ice melts, Meganyctiphanes norvegica struggles to find food and avoid predators.

A dense population of krill feeding on phytoplankton on the underside of an ice sheet. Image from: https://news.nationalgeographic.com/news/2013/08/130817-antarctica-krill-whales-ecology-climate-science/

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Script Authors: Cecille Sorio and Jeff Orchard

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Meet the Zooplankton: Chaetognaths

This is Jim Fiorendino, your host for On the Ocean. Lurking in the cold arctic depths, an ambush predator hunts for its next meal. Detecting motion with the tiny hairs along its body, it lunges forward and seizes its target with the sharp, serrated hooks on the side of its head. Having captured and devoured its prey, the creature meanders back to the depths.

A full-body image of the chaetognath Parasagitta elegans. The lateral and tail fins can be seen clearly. Image from: http://www.arcodiv.org/watercolumn/chaetognaths/images/Parasagitta_elegans-750×750.jpg

Chaetognaths, which means bristle-jaws, are planktonic, predator marine worms. They are more commonly known as arrow-worms. Arrow worms range in size from 2 to 33 mm, approximately the size of a bobby pin. Their bodies are long, narrow, and transparent, separated into 3 sections: a head, trunk, and tail. Additionally, arrow worms can see using two compound eyes on their heads. On the sides of the arrow-worm’s head are between 4 and 14 spiny bristles used to capture and immobilize prey with neurotoxins. Arrow worms typically feed on small marine crustaceans known as copepods. In addition to being voracious predators, arrow worms are often prey for other, larger marine creatures like jellyfish, seabirds, or even other arrow worms.

Image of the head of an arrow worm, with bristles. Image credit: Russ Hopcroft, University of Alaska Fairbanks, https://oceanexplorer.noaa.gov/explorations/16arctic/background/pelagic/media/worm.html

Though they are known to be globally distributed, arrow worms are most commonly found on Arctic and sub-Arctic shelves, living alone or in small colonies. A shelf is a shallow area of the ocean attached to continental landmasses, distinct from the much deeper sea floor in large ocean basins. Currently, there are roughly 120 described species of arrow worms, 20% of which are benthic, which means they live on the bottom of the ocean, attaching to rocks or sediments, instead of in the water column.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Script Authors: Nicole Leahy-Lentz and Brandon Lentz

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Meet the Zooplankton: Strombidium

This is Jim Fiorendino, your host for On the Ocean. It is difficult to imagine how small plankton are. Often, the size of these organisms is measured in micrometers. For perspective, a piece of paper is 100 micrometers, or microns, thick. The subject of today’s show, marine plankton known as Strombidium, are only between 30 and 60 microns long.

image from: https://taxonomic.aad.gov.au/keys/ciliate/key/Antarctic%20Marine%20Ciliates/Media/Html/images/Strombidium_sulcatum/strombidium_sulcatum.jpg

Let’s zoom in on what makes Strombidinium so important in the oceans. Strombidium are single-celled marine ciliates, meaning they are covered in tiny hair-like projections that help them swim and eat, with elongate, oval shapes. In contrast with other ciliates, the cilia on much of the surface of Strombidium cells have been lost or shrunk to short bristles, while the cilia around the oral cavity of the cell are large. Strombidium are important members of marine food webs because they eat and repackage extremely small phytoplankton, known as picoplankton, for other, larger predators like copepods to consume.

image from: http://microzooplankton.uconn.edu/media.html

Strombidium may also be an important indicator of ecosystem health and response to climate change. A study in the western Arctic Ocean during the summer sea-ice reduction period found differences in ciliate community structure within their sampling region associated with environmental conditions and nutrient availability, specifically ciliate abundance and species diversity. These results led the authors to propose monitoring ciliate diversity and abundance could be an effective way to monitor ecosystem health and response to climate change.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Script Authors: Jordan Achilles and Nick Minnery

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino