Heatwole sees through his microscope 

 as he probes the plant — tiny animals 

 with four pairs of stout legs, also 

 known as water bears or tardigrades. 

 There are rotifers, protozoans and 

 nematode worms too. These are all 

 nearly microscopic animals that can 

 exist in suspended animation for 

 decades when 

 dried out. 



"They are 

 similar to species 

 found in soil that 

 is subject to 

 drying out," he 

 says. "They're 

 basically soil 

 animals living up 

 in trees." 



As morning 

 dew or rain 

 moistens Spanish 

 moss, the critters 

 become active. 

 But when the 

 moss is parched, 

 the microscopic 

 community of 

 animals goes 

 dormant. 



"They can 

 stand high and 

 low temperatures, 

 they're unaffected 

 by chemicals, 

 they even quit 

 respiring and 

 metabolizing," 

 says Heatwole. 



Spanish 

 moss, which is 

 among the most 

 widespread plants 

 in the world, is 

 one of nearly 

 2,000 species of 

 Tillandsia. Its 



relatives are equally intriguing from a 

 zoological point of view. In South 

 America, the leaf bases of some species 

 form a watertight container that sup- 

 ports aerial ponds in the forest canopy, 

 says Ed McWilliams, a horticulturist at 

 Texas A&M University. Small crabs 

 have even been found dwelling in 



bromeliads in these tree habitats, 

 he says. 



Aside from a fascinating commu- 

 nity of inhabitants, Spanish moss has 

 scientific significance as an indicator 

 of air pollution. 



"Spanish moss, like lichens, ob- 

 tains all it needs from the air and there- 



fore accumulates gaseous and particu- 

 late metal pollutants," says botanist 

 David Richardson, dean of science at 

 St. Mary's University in Nova Scotia 

 and author of Pollution Monitoring with 

 Lichens. "For this reason, like lichens, 

 Spanish moss has been used for pollu- 

 tion monitoring." 



McWilliams has used propagated 

 plants to sample air in a 24,000- 

 square-mile region of northeast Texas. 

 Because Spanish moss doesn't use 

 soil, elements found inside it can be 

 traced to the atmosphere. The samples 

 are placed high on plastic poles away 

 from obvious local pollution sources, 

 such as high- 

 ways, he says. 



Unlike 

 mechanical air 

 samplers, which 

 can cost up to 

 $5,000 apiece, 

 Spanish moss is 

 cost-effective, 

 can be used in 

 remote areas 

 where electricity 

 is unavailable, 

 and requires no 

 security or 

 maintenance. 

 McWilliams has 

 used his "poor 

 man's air sam- 

 pler" to test for 

 36 elements. 



"One of the 

 things we see 

 when we do this 

 is a drop-off in 

 sodium in the 

 atmosphere as 

 we move farther 

 north," he says. 

 "So we get a 

 natural picture 

 of a broad 

 regional 

 atmospheric 

 chemistry." 



As he 

 studies changes 

 in the atmo- 

 sphere, 



McWilliams will also look for how 

 industrial pollutants are affecting local 

 communities of this native plant. Most 

 recently, he has used Spanish moss — 

 which many Texans call by its Span- 

 ish name galitos — to get a picture of 

 air pollution in south Texas along the 

 Rio Grande Valley. 



COASTWATCH 23 



