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Life Is Weird!

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Life Is Weird! Windows to the Deep Exploration Life is Weird! FOCUS SEATING ARRANGEMENT Biological organisms in cold seep communities Groups of four students GRADE LEVEL MAXIMUM NUMBER OF STUDENTS 7-8 (Life Science) 30 FOCUS QUESTION KEY WORDS What organisms are typically found in cold seep Cold seeps Sipunculida communities, and how do these organisms interact? Methane hydrate ice Mussel Chemosynthesis Clam LEARNING OBJECTIVES Brine pool Octopus Students will be able to describe major features of Polychaete worms Crustacean cold seep communities, and list at least five organ- Chemosynthetic Alvinocaris isms typical of these communities. Methanotrophic Nematoda Thiotrophic Sea urchin Students will be able to infer probable trophic Xenophyophores Sea cucumber relationships among organisms typical of cold-seep Anthozoa Brittle star communities and the surrounding deep-sea envi- Turbellaria Sea star ronment. Polychaete worm Students will be able to describe in the process of BACKGROUND INFORMATION chemosynthesis in general terms, and will be able One of the major scientific discoveries of the last to contrast chemosynthesis and photosynthesis. 100 years is the presence of extensive deep sea communities that do not depend upon sunlight as MATERIALS their primary source of energy. Instead, these com- 5 x 7 index cards munities derive their energy from chemicals through Drawing materials a process called chemosynthesis (in contrast to Corkboard, flip chart, or large poster board photosynthesis in which sunlight is the basic energy source). Some chemosynthetic communities have AUDIO/VISUAL MATERIALS been found near underwater volcanic hot springs None called hydrothermal vents, which usually occur along ridges separating the Earth’s tectonic plates. TEACHING TIME Hydrogen sulfide is abundant in the water erupt- Two 45-minute class periods, plus time for indi- ing from hydrothermal vents, and is used by che- vidual group research mosynthetic bacteria that are the base of the vent 1 Windows to the Deep – Grades 7-8 (Life Science) Windows to the Deep – Grades 7-8 (Life Science) Focus: Biological organisms in cold seep communities oceanexplorer.noaa.gov oceanexplorer.noaa.gov Focus: Biological organisms in cold seep communities community food chain. Visit http://www.pmel.noaa.gov/ direction that is roughly perpendicular to the conti- vents/home.html for more information and activities on nental rise for more than 500 km to the southwest hydrothermal vent communities. from water depths of 2000 to 4800 m. Over the past 30 years, the Blake Ridge has been extensively Other deep sea chemosynthetic communities are studied because of the large deposits of methane found in areas where hydrocarbon gases (often hydrate found in the area. Methane hydrate is a methane and foul-smelling hydrogen sulfide) and type of clathrate, a chemical substance in which the oil seep out of sediments. These areas, known as molecules of one material (water, in this case) form cold seeps, are commonly found along continental an open lattice that encloses molecules of another margins, and (like hydrothermal vents) are home material (methane) without actually forming chemi- to many species of organisms that have not been cal bonds between the two materials. These depos- found anywhere else on Earth. Methane and its are significant for several reasons: hydrogen sulfide are produced by the breakdown • The U. S. Geological Survey has estimated that of organic matter deposited in the sediments. on a global scale, methane hydrates may con- Archea and bacteria gain energy by oxidizing tain roughly twice the carbon contained in all methane (methanotrophs) or hydrogen sulfide reserves of coal, oil, and conventional natural (thiotrophs), and then become the base for a “che- gas combined. mosynthetic” food chain, in some cases by being • Methane hydrates can decompose to release grazed and filtered out of the water and in other large amounts of methane which is a green- cases by functioning as symbionts (for example, liv- house gas that could have (and may already ing in close association with mussels and clams). have had) major consequences to the Earth’s climate. Where hydrogen sulfide is present, large tube- • Sudden release of pressurized methane gas worms (phylum Pogonophora) known as vesti- may cause submarine landslides which in turn mentiferans are often found, sometimes growing can trigger can trigger catastrophic tsunamis. in clusters of millions of individuals. These unusual • Methane hydrates are associated with unusual animals do not have a mouth, stomach, or gut. and possibly unique biological communities Instead, they have a large organ called a tro- containing previously unknown species that phosome that contains chemosynthetic bacteria. may be sources of beneficial pharmaceutical Vestimentiferans have tentacles that extend into the materials. water. The tentacles are bright red due to the pres- ence of hemoglobin which can absorb hydrogen In September, 2001, the Ocean Exploration Deep sulfide and oxygen which are transported to the East expedition conducted four DSV Alvin dives to bacteria in the trophosome. The bacteria produce explore chemosynthetically-based communities on organic molecules that provide nutrition to the tube the crest of the Blake Ridge at a depth of 2,154 worm. A similar symbiotic relationship is found in m. The expedition recovered some of the largest clams and mussels that have chemosynthetic bacte- mussels (up to 364 mm) ever discovered, observed ria living in their gills. Bacteria are also found liv- shrimp that appeared to be feeding directly on ing independently from other organisms in large methane hydrate ices, and documented 16 other bacterial mats. numerically abundant groups of invertebrates. The Blake Ridge is a large sediment deposit located This activity focuses on relationships between some approximately 400 km east of Charleston, South inhabitants of cold-seep communities on the Blake Carolina on the continental slope and rise of the Ridge. United States. The crest of the ridge extends in a 2 3 Windows to the Deep – Grades 7-8 (Life Science) Windows to the Deep – Grades 7-8 (Life Science) Focus: Biological organisms in cold seep communities oceanexplorer.noaa.gov oceanexplorer.noaa.gov Focus: Biological organisms in cold seep communities LEARNING PROCEDURE In addition to written reference materials (ency- 1. Lead a discussion of deep-sea chemosynthetic clopedia, periodicals, and books on the deep communities. Contrast chemosynthesis with pho- sea), the following websites contain useful infor- tosynthesis. In both processes, organisms build mation: sugars from carbon dioxide and water. This pro- http://www.bio.psu.edu/cold_seeps cess requires energy; photosynthesizers obtain http://biodidac.bio.uottawa.ca/ this energy from the sun, while chemosynthesiz- http://www.fishbase.org/search.cfm ers obtain energy from chemical reactions. Point http://www.geomar.de/projekte/sfb_574/abstracts/vanDover_ out that there are a variety of chemical reactions et_al_2003.pdf (this document also contains a that can provide this kind of energy. Contrast food web model for the Blake Ridge, so you hydrothermal vent communities with cold-seep may want to provide only selected portions of communities. Visit http://www.bio.psu.edu/cold_seeps for this reference!) a virtual tour of a cold seep community in the Gulf of Mexico. Each student group should try to determine the energy (food) source(s) of their assigned organ- Review the concepts of food chains and food isms. It may not be possible to precisely deter- webs, including the concept of trophic levels mine specific foods for all groups, but students (primary producer, primary consumer, secondary should be able to draw reasonable inferences consumer, and tertiary consumer). from information about related organisms and anatomical features that may give clues about 2. Assign each student group one or more of the fol- what the animals eat. Students should prepare lowing groups to research: a 5 x 7 index card for each organism with an Methanotrophic bacteria illustration of the organism (photocopies from ref- Thiotrophic bacteria erence material, downloaded internet pictures, or Xenophyophores (see also genus Syringammina) their own sketches), notes on where the organism Anthozoa (sea anemones) is found, approximate size of the organism, and Turbellaria (a flatworm of the genus its trophic level (whether it is a primary producer, Platyhelminthes) primary consumer, secondary consumer, or ter- Nautiliniella (a genus of polychaetes) tiary consumer). Maldanidae (a family of polychaetes) Chaetopteridae (a family of polychaetes) 3. Have each student group orally present their Capitellidae (a family of polychaetes) research results to the entire class. On a cork- Sipunculida (peanut worms) board, flip chart, or piece of poster board, Bathymodiolus heckerae (a species of mussel) arrange the cards to show organisms that inhabit Vesicomya (a genus of clams) cold-seep communities, organisms from deep-sea Octopoda (octopus) environments outside cold-seep communities, and Munidopsis (a genus of crustacean) the trophic (feeding) relationships between these Alvinocaris (a genus of crustacean) organisms. You may want to arrange the organ- Nematoda (a round worm) isms by habitat first, then draw lines indicating Sarsiaster greigi (a species of sea urchin) which organisms probably provide an energy Chiridota (a genus of sea cucumber) source (food) for other organisms. Painting Ophioctenella (a genus of brittle star) tape or
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