Recovery of the Land Plants at Enewetak Atoll Following a Nuclear Detonation, Vol I, No. 2, PP 182-189

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}<ECK)I’ERY OF THE LAND PLANTS AT EN: determine the rate of recovery of land plants damaged by the radiation, shock and heat blast of the Nectar detonation in 1954, .\t Belle Island seven plant species were tagged, measured and photographed before the detonation. At approximately monthly intervals after the detonation for a period of ten months, and again after an interval of six months, the plants were observed and photographed. The first indication of recovery was observed on the eighth day, at which time buds were noticeable on stems of Scaeuo[a and ib’es~erschmidia plants. In a month’s time, most of the plants had formed new leaves and some had produced flowers and f] uits. In six months, the general condition of the vegetation was similar to that which existed before the detonation. Two plants, Guettarda and Portulaca, which were unhealthy at ten months, had improved by the sixteenth month. Photographs of the recovery of some of the plants are included in this report, as well as a discussion of agents other than radiation which have been reported to cause similar damage to plants of the coral atolls of the Pacific Ocean. ann+es 1954–1 ’357 afin de determiner la vitesse de restauration de plantes de pleine terre endommag&es par les radiations, le shock et le souffle thermique de l’explosion Nectar en 1954. A Belle Island, sept esp?ces de plantes ont t!t~ ktiquetdes, mesurees et photographiees avant pendant une periode de dix mois apr?s l’explosion et ensuite, apr+s un d~lai de six mois. Le premier indite de restauration a W observe le huiti+me jour, moment auquel des bourgeons ont 4t~ relew% sur es tiges de Scaevola et .Vfeswr-dwnidia. End6ans une ptkiode d’ un mois, la plupart des plantes avaient forme de nouvelles feuilles et certaines avaient produit des fleurs et des fruits. En six mois, Ies conditions g4m&ales de vegetation +taient redevenues semblables a celles qui existaien t avant 1‘explosion. Deux plantes. Guettarda et Portulaca, qui etaient maladives & dix mois, se sent ameliorees au seizi?me mois. Des photographies de la restauration de plusieurs de ces plantes sent inclues clans ce rapport ainsi qu’une discussion des agents autres que les radiations connus commc +tant cause de semblables d~gats aux plantes des attols de Zusasnmenfasstig-Eine langfristige Untersuchung am Eniwetok Atoll wurde wahrend der Jahre 1954-57 durchgeftihrt urn die Geschwindigkeit der Erholung der durch Bestrahlung, Schock und Hitzestoss der Nectar Detonation in 1954 beschiidigten Landpflanzen festzustellen. Auf der Belle Insel wurden sieben .4rten vor der Detonation markiert, gemessen und photographiert. In ungefahr monatlichen Abstanden, wahrend der ersten 10 Monate nach der Detonation und danach nach 6 Monaten wurden die Pf3anzen wieder beobachtet und photographiert. Das erste Anzeichen der Erholung wurde am achten Tag gefunden, indem Knospen hatten die meisten Pflanzen neue Blatter gebildet und einige hatten Bltiten und Fruchte. Nach 6 Monaten war der generelle Zustand der Vegetation ahnlich dem der vor uer Detona- *Operated by the University of Washington under Contract .No. AT(45– Atomic Energy Commission. ) 1385 with the United States

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tion rxistirrte. Zwel Pflanzen, Guettarda und Portuka, die nach 10 Monaten noch ungesund warm, hattejl sich nach 16 ~Ionaten gebessert. Photographien einiger der erholten Pflanzen sind diesem Bericht beigefW sowie eine Besprechung der Mittel, ausser den Strahhmgen, von denen ahnlicher Schaden wir der an den Pflanzen der Korallenattolle des Pazifik berichtet SIriCE the summer of 1946, the Laboratory of I<acliation Biology of the University of Washington has conducted studies at the Eniwetok Proving Ground to evaluate the distribution of radioactivity in aquatic and terrestrial organisms of the atolls of the western Pacific and adjacent areas. These studies were made either shortly after a nuclear device had been detonated or after intervening periods varying from several to many months. The results of the investiga1949,(3) and 1952(5) indicated the need for a study of the reinvasion or regrowth of organisms in an area contaminated by radiation. A study of this nature was undertaken following the detonation of an atomic device (Nectar) at Eniwetok Atoll in the spring of 1954. Facilities were made available at the Eniwetok Marine Biological Laboratory on Elmer (Parry) Nec tor site FIG. 1. Eniwetok Atoll.

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184 RECOVERY OF THE LAND PLANTS AT ENIWETOK ATOLL Island by the Division of Biology and .Nfedicine of the United States Atomic Energy Commission, and logistic support to carry out the sampling programme was furnished by Joint Task Force Seven of Operation Castle. The study of the land plants was a part of the over-all programme of the Laboratory of Radiation Biology. In this report only the results of this portion of the programe are presented. The results of the investigations on the following organisms already have been reported: reef The objective of the land plant programme was to determine the length of time required for a plant damaged by a nuclear detonation to resume its normal functions of growth and reproduction while being subjected to chronic The main site of study was BeHe Island tion (Fig. 1). This area was estimated to be far enough removed from ground zero that the plants would not be uprooted by physical forces yet would be in an area of sufficient radioactivity for the proposed study. Representative plants of the eight most common species growing in the area were studied in detail; however, numerous other plants also were observed. Before the Nec detonation the plants were staked, labell measured and photographed. After the deto tion, and at approximately monthly inter~ thereafter, observations and measurements w made of the plants and photographs were tak Scaevola sericea Vahl, a woody shrub, was cho> as the principal plant for study because of widespread occurrence on the islands of ~ Central Pacific Ocean. The other plants studi in detail were: Messerschmidia argentea, Guetta) speciosa and Cocos nucz~era, trees; Lepturus repe a grass; Boerhaavia tetrandra and Triumfe firocumbens, prostrate vines; and Portulaca olerac a fleshy herb. The locations of these plants the island are shown in Fig. 2. Gamma survey-meter readings also were tak to determine the gamma dose to which tl plants were subjected. Belle Island during the period of investigatic, are given in Fig. 3, which includes the theoretic gamma dose rate according to MILLER an minute after the detonation to the end of 20 days was calculated to be approximately 400 I Before the Nectar detonation, the plants o Belle Island were generally green and health> Secward reef flat FIG. 2. Diagram of Belle Island, Eniwetok Atoll, showing the location of the land plant stations and the collecting areas.

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erved. Before the lNect, ES were staked, labelle raphed. After the deton: nately monthly interva s and measurements wer Iphotographs were taker wood y shrub, was chose] for study because of it z on the islands of th[ The other plants studiec ra, trees; Leplurus repem, es; and Portulaca Oleracea, tions of these plants on readings also were taken na dose to which the eter readings taken at period of investigation includes the theoretical ding to MILLER and d total dose from one on to the end of 200 nation, the plants on \ FIG.4. General view of land plants at Belle Island, Eniwetok Atoll. (a) On April 15, 1954, before the .Nectardetonation. (b) On May 22, 1954, eight days following Nectar, showing

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I FIG. 6. Land plants at Belle Island, Eniwetok .Atoll, Area D. (a) Three months after the Nectar detonation. (b) Six months after detonation.

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FIG. 7. Guettardaplant at Belle Island, Eniwetok .\toll. (a) Close-up of unhealthy plant (No. 1216) on March 15, 1955. (b) Close-up of the same plant on r{ovember 1. 1955.

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o Gommo dose rote-Belle Is. (10) Doys after 14 May 1954 FIG. 3. Gamma dose rates ,at three feet at Belle Island, Eniwetok Atoll, May 15, 1954 to March 21, 1955, compared with the decay of fission products from the slow neutron looking. A photograph of the general area taken ance of the vegetation. In some plants there was yellowing of the leaves and necrosis, especially in Scaevola and Guettarda, and some reddening of the tops of the grass, Lepturus repenx. The latter symptom is typical of some species of plants growing in phosphorus-deficient soil, a condition often found on coral atolls and in areas where the top soil has been disturbed or blown away. The Mike detonation of 1952 had removed most of the plants and top soil from Belle Island, resulting in the depletion of some of the elements essential for plant growth. In spite of these deficiencies regrowth of the plants at Belle Island was rapid. In April 1954 some of the Scaevola and Me.rserschmidia “trees” were up to five feet in height, with a spread of ten feet, and bore many flowers and fruits. Plants of the other species also were well established. A photograph of Belle Island taken eight days following the Nectar detonation (Fig. %) shows the extent of the damage sustained by the plants. From the air the island looked brown and desolate. On closer inspection it was found that most of the plants had been scorched by the heat wave and many of them had been blown over or broken by the shock blast. Two of the previously tagged plants (Coco~ and Portulaca) had disappeared or had been dislodged from their original positions; other plants of these species were staked and Iabelled for study. On the tall shrubs, such as Scaeuola, Messerschmidia and Guettarda, the leaves were usually gone or scorched, and the scorched branches and a few persistent leaves were all that remained of the plants. Flowers and fruits were found on some plants, especially in the prostrate plants such as Portulaca, which was located behind a large fallen coconut trunk. Close-ups of examples of damaged plants eight days post Nectar are shown in the foreground of Figures 4b and 5a. Recovery of the plants was rapid. Heavy rains occurred on the third day. On the eighth served on the stems of Scaevijla and .14esser-

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186 RECOVERY OF THE LAND PLANTS AT ENIWETOK ATOLL the shoot leaves were 7–15 cm long, covering much of the old stems (Fig. 5b) and giving the plants a green and healthy appearance. By this time many of the other plants had formed new leaves and three species (Portulaca, Triumfetta, and A4esser.rchrnidia)had produced new flowers and fruits. The island now had lost its scorched appearance; from the air itlooked green rather than brown as it had one month earlier. In August, three months after the detonation, the plants were growing well (Fig. 6a) and some species, such as Boerhaavia, had produced new flowers. The leaves of most of the species had grown to maximum size, and the branches had grown almost to the pre-Nectar dimensions. This was not the case with the Guettarda and Lepturus plants , which recovered more slowly than the other species. The new growth on the Guettarda plant consisted of ten small leaves which originated from a new shoot 18 cm tall at the base of the old plant; the Lepturus plant was’ a mat of dead tops with some new growth forming at the periphery. In six months the general condition of the vegetation (Fig. 6b) was similar to that which existed before the Nectar detonation. In March 1955, approximately ten months post Nectar, the plants appeared to be normal, most of them bearing abundant flowers and fruits, healthy, green leaves, and the usual amount of yellow, older leaves. The Guettarda plant, however, bore curled, distorted, and unhealthy-looking leaves (Fig. 7a). When observed again in November 1955, it bore about thirty healthy, green leaves, had increased in height and apparently was plant bore only a few leaves in March 1955, but when observed in November 1955, it had recovered somewhat, bearing abundant flowers and some green leaves. No other aberrant growth forms were seen in the field observa~ions at Belle Island. At Janet Island, the fascia ted stems and the

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aluate the recovery al t the Eniwetok Provit ‘ fifteen months aft, vere made in 1949 k Iities in ten species [ s where atomic detona higher than those ol Nectar survey. Thest ?sion of stems, severe umpling and twisting t did not describe it. JetWeen two of the he plants closest to lere radiation levels verely affected. In Is were lower, the Iiation effects from Y many of the ? growth after the Illic nutrients and ons are known to e of the plant. In Ias been removed the surface layer g in the curling, e, it would be the causes of :ist. In areas of Table 1. T_heregrowthof Scaevoia sfi. (Plant jfo. 13 19) at Be[[e i~[and, Eniwetok Atoll,from May 22, 1954 to March 15, Healthy; green flowers and Plant badly damaged, stems naked and broken; some burned and green leaves persist at terminals New leaves on stems; Most leaves green and healthy; plant not as bushy as in April Plant as healthy and bushy as in April Growth normal in every respect; small flowers Plants healthy, larger than in April, many flowers Yellowing of oldest leaves only; plant healthy, no flowers or fruits A few plants observed with persistent floral No flowers observed on on this plant Flowers present on Scaevola Plant No. 1209, Flowers present on and No. 1213, Area A, Some Scaevola plants 2 metres in height could be attributed to the radiation, because it Observations made in February 1956 in the has been shown in controlled field experiments, with several plants, that chronic doses of gamma radiation of 13–37 r]day for two to five months can cause plant abnormalities of various kinds,@3J similar to those found at the Eniwetok Proving Ground. The total gamma dose delivered in these experiments ranged from 780 r to 5,550 r. In more recent studies with conifers Sparrowt20J observed that doses as low as 3 r and 4 rjday caused death of Pinus rigida after six years of exposure (total cumulative dose, about 8,000r). Many plants, however, were dead or dying at doses much below this cumulated dose, and some visible damage was observed at doses below 3 rlday. Marshall Islands by FOSBERGC9’lgj also suggest possible radiation damage to plants twentythree months after an incidence of high-leveI radioactive fallout. He found severe damage in the land plants (Guettarda speciosa, Cocos nuctfera, Surianu rnaritirna and others) at Gegen Island, Rongclap Atoll, where the “total radiation dose to infinity” was reported to be 3,360 r. Where the levels of radiation were 10–100 times lower, little or no damage was observed. However, some species (Guettarda, Lepturus re$ens, and Flewya ruderalis) appeared to be normal at Kabelle Island where the radiation level was Cordia subcordata, Cocos nucz~era and Pisonia

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188 RECOVERY OF THE LAND PL.4NTS AT ENIWETOK ATOLL grandis) were abnormal in appearance at islands where the levels of radioactivity were lower. Fosberg suggested that some species of plants were more susceptible to radiation than others. On the other hand many of the abnormalities reported by Fosberg, St. John and Biddulph have been reported from coral atolls where no radioactive fallout has occurred. For example, defoliation and death …