#17: Life finds a way
One recurring theme in the book (and in all Carson's work, really) is the interdependence and tenacity (plus the paradoxical fragility) of life. Along the coral reefs, for example, life's grip is very tenuous; coral can survive only above a certain temperature of water, in a very narrow band of sunlight. But organisms band together, in some cases living in and anchored to each other, and adapt themselves to survive in a severely small niche and carve out their own islands of life. Shrimps settle into sea sponges and survive on the bits of food left behind by the water the sponge filters; sea fans anchor themselves to coral, and snails anchor themselves to the sea fans; and the metaphor turns literal in the case of mangroves, whose seedlings settle down into the sea silt and, as their root systems mature, hold on to the soil well enough and attract enough soil-working organisms to build little islets around them in the ocean's midst.
Carson is intent on sharing with the reader the beauty of even the most rudimentary or bizarre sea-dwellers; the great expanses of rockweed on rocks shores, for example, which lie flat at low tide only to billow expansively at the high, providing a hiding and dwelling place for countless small fish, snails, and crabs; "it is a fantastic jungle, mad in a Lewis Carroll sort of way." Or the vermetid snail, which form long, spiraling, cornet-like shells; they live so closely intertwined that geologists call the lithified remnants of their shells "worm rock." When something conventionally pretty like a sea horse enters the picture, it's actually a bit of a shock; it's odd to see a popular symbol of beauty in the ocean, when we've already been introduced to such strange beauty from its far less-appreciated residents.
Carson wrote three books on the sea, and it is a little overwhelming to read them all in a row. The Edge of the Sea is probably the best-rounded one, though its focus is somewhat narrow and the from-species-to-species, zone-by-zone layout can be a bit monotonous (though this may be my familiarity with her writing talking). Her first book, Under the Sea-Wind, offers a more lyrical look at ocean life, but her florid prose can be dense and hard-to-follow in spots. The Sea Around Us, a physical history of the sea, is actually her clearest and most easily engaging work on the ocean - it's the clear forebearer of all the immensely readable Bill Bryson-esque popular science tomes - but it has the misfortune of being dated by pre-tectonic 1950s geology. All of Carson's sea books, though, are rife with painterly prose you too seldom see in science books nowadays and a love of the entire scope of life in the ocean. It's a bit of a shame she's remembered for Silent Spring only in modern times, as she was another Jacques Cousteau in her day in how she gave the public a newfound appreciation of the sea.