Notes on sea beach ecology, food sources on sandy beaches and localized diatom blooms bordering Gulf beaches.

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 Leptogorgiaand 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, Leptogorgh 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 Chaefocerus 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. There are variations in time both in production of food on beaches and that washing in from the sea. Quantitative studies have not been made; nevertheless, certain nonquantitative observations and distinctions can be made. Food production and the sources of food for animals living along sand beaches are considerably different from those of rocky beaches. In contrast to rocky shores, no large algae grow on sand beaches except for filamentous green varieties which find small footholds upon certain molluscs such as Donax, the mole crab Emerita, strands of the alcyonarian coral Leptogorgia, and other beached objects such as logs. They occur only in negligible amounts. Thus the basic food along the sand beach is microscopic plants, chiefly diatoms, bacteria, various other unicellular algae and detritus. The diatoms are probably the most abundant autotrophic organisms produced on the beach. Presumably the beach bacteria are largely heterotrophic. Most of the food consumed on sandy beaches comes from the sea. Pearse et al. (1942, p. 137) have made similar comparisons before and their words are worth quoting, “A marine sandy beach seems like an inhospitable place for plants and animals to become established. On a rocky, wave-beaten headland, where storms rage and intertidal areas are exposed alternately to cool, surging water and hot or cold desiccating air, there may be an abundant biota of attached seaweeds, hydroids, barnacles, clams, etc. The rocks may be literally carpeted with living things. On the other hand a shifting, Manuscript received Apnl9,1979;accepted April 19, 1979. sandy beach is usually without much apparent life. There may be seen an occasional scuttling crab, a school of little fishes wiggling into the shallows, or a solitary sandpiper drilling holes with his long beak. In general a sandy shore seems to be a barren, clean place admirable for bathing, but unpromising as a habitat where a biologist may collect or study animals. But appearances are deceiving. Marine littoral sands swarm with plant and animal life.” Along both rocky and sandy beaches food production has a seasonal aspect on temperate coasts, and the total production or peaks change from year to year. Nevertheless, this process has aspects of steadiness and regularity. Possibly the same thing holds for drift of planktonic materials from the sea, but information on that point is lacking. There is a second fundamental difference between the sand beach and the rocky beaches in that the rougher and more abrupt the beach, the less organic materials, especially large particles or bodies, tend to strand and add their increment to the food of the shoreline. This holds true for two reasons. Rocky beaches are generally not wide and the water from waves and tide is channeled into quite strong currents returning to the sea. Floating objects may bump or bounce against rocks, which act as more or less pointed bodies, and be swirled out to sea again long before they ground on relatively level bottom. This is not to imply that stranding does not take place on rocky coasts, for it sometimes does and the total frequency may even be high, but the tendency is less than on an even-bottomed sand beach. The amount of food stranding on rocky coasts will