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Meet the Zooplankton: Tiny and Tenacious

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The ocean is home to so many amazing creatures. Compared with sleek and streamlined sharks, majestic whales, or colorful coral reefs, tiny drifting organisms might seem a little boring or insignificant. However, these microscopic organisms are incredibly diverse, exhibiting a variety of strange forms and strategies for surviving in an unforgiving environment where they compete fiercely for food and struggle to avoid being eaten.

Plankton are organisms that cannot swim against currents. Instead, they move with bodies of water throughout the oceans. Some plankton have a limited ability to swim; several species are known to migrate from deep waters, where they hide from predators, to shallow waters, where they feed. Most of the time, though, they are at the mercy of currents. The term plankton is derived from the Greek word planktos, which means drifter or wanderer.

In general, plankton are divided into two major groups: the phytoplankton and zooplankton. Phytoplankton, like plants and trees on land, are autotrophic; they make their food by photosynthesizing, using energy from the sun, carbon dioxide, and nutrients in their environment. Zooplankton are heterotrophic, which means they do not make their own food. They prey on other organisms in the oceans, including phytoplankton or other zooplankton. Zooplankton are an important component of marine food webs and healthy marine ecosystems. Over the next several weeks, On the Ocean will describe several species of zooplankton, their role in the world’s oceans, and the challenges they face to survive.

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.

Contributing Professor: Dr. Lisa Campbell

Script Author: James M. Fiorendino

Meet the Zooplankton: Tintinnopsis

Living in the ocean are tiny marine sculptors known as Tintinnids. Tintinnids are a group of zooplankton that build shells around themselves using primarily organic material, such as proteins, but often incorporating minerals and sediment. Tintinnid shells, known as loricae, are marine works of art, taking many different shapes but most often resembling a vase or bell. Scientists typically classify tintinnids based on the shape of the lorica; within the Tintinnopsis complex, there are roughly 100 described species. The ability of these organisms to gather particles and form shells is currently their only unifying feature; identifying other traits is difficult, as the organisms are obscured by their loricae.

Figure 1: Diagram of a typical tintinnid
Figure 1: Diagram of a typical tintinnid. From: Zaid, M. M. A., & Hellal, A. M. (2012). Tintinnids (Protozoa: Ciliata) from the coast of Hurghada Red Sea, Egypt. The Egyptian Journal of Aquatic Research, 38(4), 249-268.

Zooplankton belonging to the Tintinnopsis complex are present in coastal areas of North America, Europe, South America, and Eastern Asia, where sediment is plentiful for them to cover themselves with. Tintinnids can be found in surface waters to depths of over 300 meters. They are commonly present at densities of roughly 100 per liter but can reach densities of thousands per liter. Tintinnids are grazers, feeding on phytoplankton and bacteria. At one end of the lorica, the Tintinnid beats tiny hair-like appendages known as cilia, creating a current that draws prey toward the cell. These cilia are also used to move the cell through the water.

Figure 2: Loricae of various species of tintinnids collected from the Egyptian Red Sea (1: Tintinnopsis cylindrical, 2: Tintinnopsis campanula, 3: Tintinnopsis gracilis, 4: Tintinnopsis davidoffi, 5: Tintinnopsis radix, 6: Tintinnopsis corniger, 7: Tintinnopsis lobiancoi, 8: Tintinnopsis tocantinensis, 9: Tintinnopsis nana, 10: Tintinnopsis compressa, 11: Tintinnopsis orientalis, 12: Tintinnopsis rotundata)
Figure 2: Loricae of various species of tintinnids collected from the Egyptian Red Sea (1: Tintinnopsis cylindrical, 2: Tintinnopsis campanula, 3: Tintinnopsis gracilis, 4: Tintinnopsis davidoffi, 5: Tintinnopsis radix, 6: Tintinnopsis corniger, 7: Tintinnopsis lobiancoi, 8: Tintinnopsis tocantinensis, 9: Tintinnopsis nana, 10: Tintinnopsis compressa, 11: Tintinnopsis orientalis, 12: Tintinnopsis rotundata) From: Zaid, M. M. A., & Hellal, A. M. (2012). Tintinnids (Protozoa: Ciliata) from the coast of Hurghada Red Sea, Egypt. The Egyptian Journal of Aquatic Research, 38(4), 249-268.

 

Tintinnid abundance is directly related to prey abundance, light and nutrient availability, temperature, and salinity, or the abundance of salt in marine waters. In the spring, the greatest number of Tintinnid species are present, but tintinnid biomass is greatest in the summer months, usually due to the success of one or a few specific species.

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 Author: Anum Shahid and Bradley Bryant

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Meet the Zooplankton: Globigerina Bulloides

Why did the mushroom get invited to all the parties? Because he’s a fun guy! The star of today’s show, the heterotrophic zooplankter Globigerina bulloides, is not actually a type of fungus, but it does look like a bunch of mushroom caps squished together. Globigerina bulloides belongs to a group of zooplankton called foraminifera, which are characterized by their chambered, often intricate, calcium carbonate shells or tests. These tests have pores through which the cell projects extensions of itself, known as pseudopodia, to capture food, attach to a surface, or swim.

Scanning electron micrograph of a Globigerina bulloides test; this image shows only the test,which remains in sediments after the organism dies. Image from: https://alchetron.com/Globigerina-bulloides#-
Scanning electron micrograph of a Globigerina bulloides test; this image shows only the test,which remains in sediments after the organism dies. Image from: https://alchetron.com/Globigerina-bulloides#-

Globigerina bulloides can be found globally in the photic zone, where sunlight is available throughout the water column. They are most abundant in the Southern Hemisphere, specifically the Southern Ocean. Upwelling in the Southern Ocean ensures availability of nutrients for Globigerina bulloides, particularly in the spring when they are most abundant.

A living Globigerina bulloides cell. The many spines extending outward are extensions of the cell known as pseudopodia. Image from: https://wordsinmocean.com/2012/05/16/does-phosphate-thin-foram-shells/
A living Globigerina bulloides cell. The many spines extending outward are extensions of the cell known as pseudopodia. Image from: https://wordsinmocean.com/2012/05/16/does-phosphate-thin-foram-shells/

Globigerina bulloides tests are like tiny history records, preserving indicators of Earth’s climatic conditions in the past. The calcium carbonate in their tests contains oxygen, of which there are isotopes, or atoms with different numbers of neutrons. Oxygen 18, with more neutrons, is heavier than oxygen 16. This difference in mass means the rate of exchange between the ocean and atmosphere for oxygen 18 is different from oxygen 16, both varying with temperature. Measuring the ratio of oxygen 18 to oxygen 16 in Globigerina bulloides tests allows scientists to determine what the climate was like throughout Earth’s history. When there is a greater abundance of oxygen 18 relative to oxygen 16 in calcium carbonate tests, the climate was cooler. When the ratio was lower, the climate was warmer.

Thank you for listening; 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: Anna Ashy and Courtney Nevels

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Meet the Zooplankton: Euphausia superba

Despite being no larger than your pinky finger, the Antarctic krill, Euphausia superba, is able to sustain the largest animal on Earth, the blue whale. The Antarctic krill is a keystone species in the Southern Ocean, which means it is a species that plays a critical role in the function of its ecosystem. In addition to whales, these tiny crustaceans are preyed upon by seals, squid, and birds.

A single Euphausia superba. Photo by Martin Rauschert (http://www.marinespecies.org/photogallery.php?album=724&pic=10895)
A single Euphausia superba. Photo by Martin Rauschert (http://www.marinespecies.org/photogallery.php?album=724&pic=10895)

To sustain so many hungry predators, and maintain their population, there must be a staggering amount of krill in the oceans! The estimated biomass of Antarctic krill is around 500 million tons, making them one of the most abundant animals on Earth, with likely the greatest biomass of any multicellular animal. Krill tend to group together in congregations known as bait balls, with densities reaching 30,000 individuals per cubic meter. These bait balls can often be seen and tracked from space!

Marine predators are not the only ones chasing after krill. Krill oil is becoming a popular supplement for humans who want a healthy dose of omega-3 fatty acids. Demand for krill oil has driven the development of a commercial fishery for these animals, capturing over 300,000 tons annually to produce several products including krill oil and animal feed. There is concern regarding the potential overfishing of Antarctic krill due to the importance of krill as a keystone species and their role in removing carbon dioxide from the atmosphere. Krill eat phytoplankton, which take up CO2 from the atmosphere. But krill are sloppy eaters, and the pieces of phytoplankton they drop sink to the bottom of the ocean along with their feces. The feeding activity of krill moves substantial amounts of carbon to the deep ocean; overfishing may limit this process, with consequences for Earth’s climate.

Krill feeding on algae on the underside of pack ice. Image from: https://commons.wikimedia.org/wiki/File:Krillicekils.jpg
Krill feeding on algae on the underside of pack ice. Image from: https://commons.wikimedia.org/wiki/File:Krillicekils.jpg

Thank you for listening; 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: Abby Jyrkila and Marisa Gonzales

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Meet the Zooplankton: Strobilidium

If phytoplankton are the grass of the sea, then grazers like the marine ciliate Strobilidium are the cows. Phytoplankton commonly cause harmful algal blooms when they grow to very high densities, becoming detrimental to marine ecosystems and human health. Organisms that feed on phytoplankton deter runaway growth and prevent harmful blooms.

Light micrograph of a strobilidium sp. cell. Photo by Olivier Barth, from: http://www.photomacrography.net/forum/viewtopic.php?t=4419&sid=5c3264cc66677387565a374beddf07b3
Light micrograph of a strobilidium sp. cell. Photo by Olivier Barth, from: http://www.photomacrography.net/forum/viewtopic.php?t=4419&sid=5c3264cc66677387565a374beddf07b3

Strobilidium is a naked ciliate; a single-celled organism with tiny hair-like projections called cilia arranged in a spiral around the cell’s mostly spherical body. They are called naked because they do not have a shell or other protective covering. Cells of Strobilidium are 40-60 microns in diameter, or about 2 thousandths of an inch, which is still bigger than the phytoplankton they eat!

A fixed strobilidium cell, with visible cilia. Image from: http://www.hedegard.nu/planktonbilder/
A fixed strobilidium cell, with visible cilia. Image from: http://www.hedegard.nu/planktonbilder/

Zooplankton like Strobilidium are important members of marine food webs. They are effective grazers, responsible for 30 – 50% of grazing activity on phytoplankton in some environments. Additionally, they are important prey for larger organisms, such as fish.

Currently, scientists are unsure how grazers like Strobilidium, and marine food webs in general, will respond to climate change. Research has indicated that rising ocean temperatures can promote the growth of Strobilidium, which means more intense grazing on phytoplankton populations. Increased grazing could help prevent harmful algal blooms in the future. However, phytoplankton will also respond to rising temperatures, possibly with increased growth rates of their own. The impact of climate change on marine food webs remains uncertain.

Thank you for listening; 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 Author: Lane Peery

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino