{"72038":{"#nid":"72038","#data":{"type":"news","title":"Marine Phytoplankton Changes Form to Protect Itself","body":[{"value":"\u003Cp\u003EA tiny single-celled organism that plays a key role in the carbon cycle of cold-water oceans may be a lot smarter than scientists had suspected.\u003C\/p\u003E\n\u003Cp\u003EIn a paper published June 11 in the online version of \u003Cem\u003EProceedings of the National Academy of Sciences\u003C\/em\u003E, researchers report the first evidence that a common species of saltwater algae - also known as phytoplankton - can change form to protect itself against attack by predators that have very different feeding habits.  To boost its survival chances, \u003Cem\u003EPhaeocystis globosa\u003C\/em\u003E will enhance or suppress the formation of colonies based on whether nearby grazers prefer eating large or small particles.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Based on chemical signals from attacked neighbors, \u003Cem\u003EPhaeocystis globosa\u003C\/em\u003E enhances colony formation if that\u0027s the best thing to do for survival, or it suppresses the formation of colonies in favor of growing as small solitary cells if that\u0027s the best thing to do,\u0022 said Mark E. Hay, Teasley Professor of Biology at the Georgia Institute of Technology.  \u0022These changes in form made nearly a 100-fold difference in the alga\u0027s susceptibility to being eaten.  It\u0027s certainly surprising that a single-celled organism can chemically sense the presence of nearby consumers, identify those consumers and change in opposing ways depending on which consumers are present.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe behavior could have implications for global climate change because \u003Cem\u003EPhaeocystis\u003C\/em\u003E blooms play a key role in the carbon cycle of cold oceans, accounting for up to 85 percent of local productivity during some time periods.  This complex defensive behavior also shows how environmental factors can affect even simple organisms, Hay noted.  \n\u003C\/p\u003E\n\u003Cp\u003EConducted largely at Georgia Tech\u0027s marine lab in Savannah, Ga., the research was sponsored by the U.S. National Science Foundation and the U.S. Environmental Protection Agency.\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cem\u003EPhaeocystis\u003C\/em\u003E has two primary predators: small grazers such as ciliates, which prefer to eat small solitary cells that are four to six microns in diameter, and the larger shrimp-like copepods, which prefer to eat large, ball-shaped colonies.\n\u003C\/p\u003E\n\u003Cp\u003EWhen copepods are attacking the phytoplankton, therefore, the best survival strategy of \u003Cem\u003EPhaeocystis\u003C\/em\u003E is to form solitary cells.  When ciliates are attacking, the best strategy is to form colonies that are too large for those predators to consume.\n\u003C\/p\u003E\n\u003Cp\u003ELead author Jeremy D. Long, along with collaborators Gabriella W. Smalley, Todd Barsby, Jon T. Anderson and Mark Hay found that\u0027s just what \u003Cem\u003EPhaeocystis\u003C\/em\u003E does.  Chemicals that signaled attacks from copepods suppressed the formation of colonies by 60 to 90 percent, while signals from ciliates enhanced colony formation by more than 25 percent.\n\u003C\/p\u003E\n\u003Cp\u003EThe transformations took place over periods of three to six days, and the overall size difference could be dramatic.  \u0022When one of these cells changes to the biggest colony form, although it takes a while, it\u0027s like changing from a mosquito to 76 blue whales or 3,000 bull elephants,\u0022 Hay explained.  \u0022That\u0027s a pretty dramatic difference.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EDefensive responses are often seen in higher plants, but this is believed to be the first report of such a complex and species-specific response in marine phytoplankton.  Hay suspects scientists may find other examples of complex defensive strategies when they look more closely at other single-celled organisms.\n\u003C\/p\u003E\n\u003Cp\u003EThe response of \u003Cem\u003EPhaeocystis\u003C\/em\u003E could be important to scientists studying climate change because the predator that ultimately consumes the phytoplankton determines the fate of the carbon it contains.  If eaten by copepods, for example, the carbon becomes part of fecal packages that sink into the deep ocean where a portion of that carbon is sequestered - thereby reducing atmospheric carbon dioxide, a leading greenhouse gas.  If consumed by smaller creatures like ciliates, less of the carbon sinks to the deep sea and more remains in the surface waters.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This could alter the flow of energy and nutrients from deep to shallow, depending on what might be trying to eat it, and how the organism responds to the chemical signals of what\u0027s attacking it,\u0022 Hay said.\n\u003C\/p\u003E\n\u003Cp\u003EExperimentally, the researchers attempted to separate the chemical signals from the actual predators.  They grew \u003Cem\u003EPhaeocystis\u003C\/em\u003E in the presence of either ciliates or copepods.  They then filtered out both the phytoplankton and predators, leaving only water containing the chemical signals of attack.\n\u003C\/p\u003E\n\u003Cp\u003EWater samples containing signals from the two predators were then separately introduced into \u003Cem\u003EPhaeocystis\u003C\/em\u003E cultures that had not been attacked.  The scientists then studied how the different chemical signals affected the percentage of \u003Cem\u003EPhaeocystis\u003C\/em\u003E living in colonies or as solitary cells.  Finally, they examined whether this response affected how much the predators ate to determine if the change conferred a survival advantage.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We found that these organisms were making the right choice,\u0022 Hay said.  \u0022They were shifting to the shape that made them largely immune to whichever predator was attacking, and this shift suppressed either the feeding or growth and reproduction of the consumer to which they were responding.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe role of this phytoplankton has been controversial in the scientific community, with some arguing that \u003Cem\u003EPhaeocystis\u003C\/em\u003E makes a good food source for higher creatures in the cold oceans, while others contend its food role is small.  While this paper won\u0027t resolve the dispute, Hay believes it shows that both points of view could be correct - depending on which form the organism has taken.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022It depends on the environmental context, which we are appreciating more and more in ecology and in biomedical research,\u0022 he added.  \u0022Some of these differences are small, but they can have a large effect.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 100\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\u003C\/strong\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986); E-mail: (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003ETechnical Contact\u003C\/strong\u003E: Mark Hay (404-894-8429); E-mail: (\u003Ca href=\u0022mailto:mark.hay@biology.gatech.edu\u0022\u003Emark.hay@biology.gatech.edu\u003C\/a\u003E)\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\n\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Single-celled organisms respond to different predators in different ways"}],"field_summary":[{"value":"A tiny single-celled organism that plays a key role in the carbon cycle of cold-water oceans may be a lot smarter than scientists had suspected.","format":"limited_html"}],"field_summary_sentence":[{"value":"Single-celled algae can display complex behaviors"}],"uid":"27303","created_gmt":"2007-06-15 00:00:00","changed_gmt":"2016-10-08 03:03:29","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2007-06-15T00:00:00-04:00","iso_date":"2007-06-15T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"72039":{"id":"72039","type":"image","title":"Copepod predator","body":null,"created":"1449177425","gmt_created":"2015-12-03 21:17:05","changed":"1475894649","gmt_changed":"2016-10-08 02:44:09"},"72040":{"id":"72040","type":"image","title":"Phaeocystis solitary cells","body":null,"created":"1449177425","gmt_created":"2015-12-03 21:17:05","changed":"1475894649","gmt_changed":"2016-10-08 02:44:09"},"72041":{"id":"72041","type":"image","title":"Phaeocystis colony","body":null,"created":"1449177425","gmt_created":"2015-12-03 21:17:05","changed":"1475894649","gmt_changed":"2016-10-08 02:44:09"}},"media_ids":["72039","72040","72041"],"related_links":[{"url":"http:\/\/www.biology.gatech.edu\/faculty\/mark-hay\/","title":"Mark Hay"},{"url":"http:\/\/www.biology.gatech.edu\/","title":"School of Biology"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"154","name":"Environment"},{"id":"146","name":"Life Sciences and Biology"},{"id":"135","name":"Research"}],"keywords":[{"id":"610","name":"carbon"},{"id":"2262","name":"climate"},{"id":"1366","name":"defense"},{"id":"7561","name":"phytoplankton"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}