If you can't access it, try one of these mirrors. They do have captchas though.
http://moscow.sci-hub.bz/7c5f77c87ddeb6b1d71015646aab39b1/10.1038%40scientificamerican0507-90.pdf
http://ocean.sci-hub.bz/7c5f77c87ddeb6b1d71015646aab39b1/10.1038%40scientificamerican0507-90.pdf