Alternate Title

Notes on Sea Beach Ecology. Food Sources on Sandy Beaches and Localized Diatom Blooms Bordering Gulf Beaches

Document Type

Short Communication


Food production along sandy beaches is much different from that of rocky beaches. No large algae grow on sand beaches. Small filamentous green algae find footholds upon molluscs, mole crabs, strands of Leptogorgia and logs. Basic food along the sand beach is made up of diatoms, bacteria, unicellular algae and detritus; diatoms are probably the most abundant autotrophic organism; the beach bacteria are largely heterotrophic. Most food on sandy beaches comes from the sea. The sandy shore seems to be barren, but it swarms with plant and animal life. Food production has a seasonal aspect. Food strands more abundantly on sandy beaches because the force of water returning to the sea is much less than that coming in. Beach materials are concentrated in a strand line. All organic materials are returned to the food cycle. Beached animal remains are consumed immediately until their breakdown products ooze away to enrich the sand substrata. The materialof logs may not be redistributed until a number of years have passed. Food producing algae are diatoms, green algae, peridinians and blue-greens. Many of them are quite small and must be detected by bacteriological methods. They are probably quite significant. Food production from autotrophic algae appears to be relatively steady compared to drifting materials, which may vary enormously. Various types of food drift in as a result of dinoflagellate blooms, catastrophic cold kills and stranding cetaceans. Seasonal drifting materials such as sargassum, Leptogorgia and jellyfish come in at particular times of the year. The river mouth floods bring in material. The artificial jetsam of ships washes up on the beaches.

Nutrients and salts are also concentrated on beaches from organic remains. As a result, a type of beach-hugging planktonic bloom has been noted on the Texas coast when the sea is calm following heavy rains. It consists of a yellowish-brown conglomeration of diatoms of the species Chaetoceras sp., 15 to 20 feet wide along the shore for many, many miles. It follows heavy rains and the event is parallel to some aspects of the Florida red tide which occurs in calm weather, often following heavy rains, which are thought to bring chelating substances from the land.

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