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NOTES AND COMhfENT 291 A BLOOMOFTHEPLANKTONIC BLUE-GREEN ALGA, Trichodesmium ~~~$&~~~~,INTHEToNGAIsLANDs The planktonic blue-green alga, Trichodesmium erythraeum Ehrenberg, also known as SJcujaella erythraea (Ehrenberg ) J. de Toni, has a wide distribution in tropical and subtropical waters of the world. From time to time there have been reports of its occurrence at various localities in immense numbers; these reports were summarized by Brongersma-Sanders ( 1948, 1957). Except for the waters of the East Indian Archipelago, where Trichodesmium blooms have been reported from the Java Sea (Delsman 1939), the east coast of Borneo ( Mohler 1941) and the Arafura Sea ( Moseley 1892; Murray 1895)) the only accounts known to us of blooms of this alga in the Pacific Ocean are those of Yonge ( 1930), who stated that red water caused by Trichodesmium was frequently observed near Low Isles during the British Great Barrier Reef Expedition of 1928-1929, and Wood ( 1963)) who reports that the Trichodesmium “red tide” is an important feature in the South Pacific and Indian Oceans. Allen ( 1963) cites Wood as stating that Trichodesmium blooms may cover hundreds of square miles near the Great Barrier Reef. We believe, therefore, that the occurrence of a bloom at Tongatabu, Tonga Islands, is of interest. On 19 January 1963 a “gray tide” was noticed along the northern coast of Tongatabu, in the vicinity of the capital, Nuku’alofa. The heaviest concentration was in the area in front of the beach and boat dock at Touliki, about 1.2 km east of the post There was little office in Nuku’alofa. bloom beyond 20 m seaward of the outer edge of the fringing reef, which is about 30-45 m from the beach. The color of the bloom was mostly gray, with some pink to light red patches. The gray color led some observers to speculate that the water was filled with volcanic ash from an undersea eruption. The outer edges of the bloom formed long parallel streaks. The odor of the bloom was not noticeable except near Touliki, where there was a ‘“weedy pond” smell. At the terminal stages of the bloom, the stench resembled that of chlorine and was strong enough to hinder use of a road running parallel to the beach. Toxic effects of the bloom were relatively insignificant. There was a limited mortality among the small fishes, but most of the fishes apparently were not adversely affected. Several children were observed swimming in the most concentrated part of the bloom, and they suffered no ill effects. waded far into the One of us (L.J.L.) bloom to collect samples and did not notice any irritation. Samples taken in the bloom on 20 January 1963 with a small plankton net were found to consist alrnost exclusively of the filamentous blue-green alga, Trichodesmium erytlzraeum, the filaments of which sheaves. are grouped into characteristic Part of a sample was sent to Dr. Francis Sciences, Drouet, Academy of Natural who kindly confirmed our Philadelphia, The only other organisms identification. in the samples were a few harpacticoid and cyclopoid copepods, belonging to nonpelagic genera. In contrast, samples taken in the bay beyond the fringing reef in November 1962 and August 1963 were dominated by Calanoid copepods (mostly species of Paracalanus and Acartia) and chaetognaths. The duration of the bloom at Tongatabu was about 2 full days; it was almost completely gone by the evening of 20 January. According to Chacko ( ISSO), Trichodesmium blooms in waters around Krusadai Island, India, usually last 3-7 days. In its odor and occurrence in streaks, the Tonga bloom agrees \aith published accounts of Tric7.7oClcsn~ill~~z from other localities. The gray color is atyljical; the color has been described as dirty yellow, brownish yellow, reddish brown, brownish or reddish, blood red, and red. King (1950) states that it is yellowish at the height of the bloom, becoming reddish brown when the peak of growth is passed. 292 NOTES AND In the Java Sea, Delsman (1939) observed that Trichodesmium avoids brackish coastal water and is usually found at some distance from the coast. However, he did find it close to shore where brackish water was not present. Along the west coast of Florida, King ( 1950) found Trichodesmium in bloom abundance only within 56 km of the shore and most commonly just off the beaches. Ehrenberg (1830) reported an outbreak of red water due to Trichodesmium in the Bay of Tor ( El TQr ) of the Gulf of Suez; the red water occurred only in the bay and not in the open gulf outside of it. These records suggest a preference for coastal water over oceanic water if brackish water can be avoided. Unfortunately, we have, no information on the salinity at Tongatabu during the bloom. Harmful effects associated with blooms vary from negligible amounts to rather Reports of mortality are severe mortality. limited to waters around India (Chacko 1942, 1950; Chidambaram and Unny 1944) and the East Indies (Veenhuyzen 1879; Mohler 1941) . Although Trichodesmium blooms occur in the Atlantic ( Darwin 1839; Agassiz 1888)) we have not found any reports of mortality resulting from them. The factors that contribute to blooms of Trichodesmium are not yet known. Weather conditions at Nuku’alofa during the month of January 1963 were not exceptional. The sea temperature (estimated from the midnight-0600 air temperature) gradually increased from 23C on 1 January to 26C on 15 January, and the wind direction gradually shifted from east-southeast through east to north. The change in the wind direction may have increased the flow of outside water into the bay through Biha or Eastern Passage, but there is no reason to relate such a possible increased flow to the Trichodesmium bloom. Recent findings ( Dugdale, Menzel, and Ryther 1961) showing that Trichodesmium thrives in nutrient-improverished water and fixes atmospheric nitrogen have important implications for the generation of blooms. Finally, we wish to point out that blooms are not uncommon in Tonga, although they COMMENT have not been the subject of published acIn addition to Trichodesmium counts. blooms, “red tides,” with more toxic effects, are known. THOMAS E. BOWMAN Division of Marine Invertebrates, Smithsonian Institution, Washington, D.C. L. J. Tonga College, ‘Atele, Tonga Islunds. LANCASTER REFEXENCES A. 1888. Three cruises of the United States Coast and Geodetic Survey Steamer Blake in the Gulf of Mexico, in the Carribbean Sea, and along the Atlantic coast of the United States, from 1877-1880. v. I. Bull. Museum Comp. Zool. Harvard Coll., 14. 314 p. fixing organisms ALLEN, M. B. 1963. Nitrogen in the sea, p. 85-92. Zn C. J. Oppenheimer [ ed.], Symposium on marine microbiology. Thomas, Springfield, Illinois. M. 1948. The imporBRONGERSMA-SANDERS, tance of upwelling water to vertebrate paleontology and oil geology. Verhandel. Koninkl. Ned. Akad. Wetenschap., Afdel. Natuurk., Sect. II, 45: 1-112. 1957. Mass mortality in the sea, p. 941-. 1010. Zn J. W. Hedgpeth [ed.], Treatise on marine ecology and paleoecology. v. I, Ecology. Geol. Sot. Am. Mem., 67. 1296 p. of CHACKO, P. I. 1942. An unusual incidence Current Sci. Inmortality of marine fauna. dia, 11: 402. 1950. Marine plankton from waters -. around the Krusadai Island. Proc. Indian Acad. Sci., sect. B, 31: 162-174. CHIDAMBARAM, K., AND M. MUKUNDAN UNNY. 1944. Note on the swarming of the planktonic alga Trichodesmium erythrueum in the Pamban area and its effect on the fauna. Current Sci. India, 13: 263. DARWIN, C. R. 1839. Journal of researches into the geology and natural history of the various Hafner countries visited by H. LM. S. Beagle. 615 p. Publishing Co., New York-London. (Facsimile reprint of first ed., 1952). DELSMAN, H. C. 1939. Preliminary plankton investigations in the Java Sea. Treubia, 17 : 139-181. DUGDALE, R. C., D. H. MENZEL, AND J. H. RYTHER. 1961. Nitrogen fixation in the Sargasso Sea. Deep-Sea Res., 17: 297-300. EHRENBEFIG, C. G. 1830. Neue Beogachtungen iiber blutartige Erscheinungen in Aegypten, Arabien und Siberien nebst eine iibersicht und Kritik. Poggendorf’s Ann. Phys. Chem., AGASSIZ, 18: 477-515. NOTES J. E. plankton J. Florida MOHLER, W. nomeen Natuurk. KING, AND 1950. A preliminary report on the of the west coast of Florida. Quart. Acad. Sci., 12: 109-137. A. 1941. Een blauwwieren-pheaan het strand van Balikpapan. Tijdschr. Ned. Indie, lOl( 3) : 75- 79. H. N. 1892. Notes by a naturalist. An account of observations made during the voyage, of H.M.S. Challenger round the world in the years 1872-1876, under the command of Capt. Sir G. S. Nares, R.N., K.C.B., F.R.S., and Capt. F. T. Thomson, R.N. John Murray, London. 540 p. MOSELEY, 293 COMMENT JOHN. 1895. A summary of the scientific results. Rept. Sci. Res. Voyage H.M.S. Challenger 1872-76. 796 p. ( First Part) ; 797-1608 p. (Second Part). VEENHUYZEN, J. C. 1879. Communication on: Trichodesmium erythraeum. Natuurk. Tijdschr. Ned. Indie, 38: 150-151. WOOD, E. J. F. 1963. Some relationships of phytoplankton to environment, p. 275-285. Zn C. H. Oppenheimer Led.], Symposium on marine microbiology. Thomas, Springfield, Illinois. YONGE, C. M. 1930. A year on the Great Barrier Reef. Putnam, London and New York. 246 p. MURRAY, SELF-CLOSINGDEVICE FORSAMPLINGPLANKTONNEARTHE SEABOTTOM~ The apparatus described here was designed to obtain samples of plankton from 1 This device was developed during an ecological study supported in part by National Science Foundation Grant G-7141 to Dr. E. W. Fager of Scripps Institution of Oceanography, and in part Oceanography Research of by Scripps Tuna Scripps Institution of Oceanography with funds provided by U.S. Bureau of Commercial Fisheries under Contract 14-17-0007-28. FIG. 1. Diagram near the sea floor. It can be used from a small boat operating over a smooth bottom in shallow water. Other apparatus designed for collecting plankton in the immediate vicinity of the bottom (Russell 1928; Bossanyi 1951; Wickstead 1953) and conventional conical nets ( Sverdrup, Johnson, and Fleming 1942) have inadequate closing mechanisms or are of self-closing bottom plankton net.