522 0,10 ~ ~ I ~ 'E ~ OJ I ~~ Q) ... IV.. Q) 0.04 u c l! IV Q) U 0.02 0.10 --- ~ ~ 0.08 .E C) '-' 0.06 ... QI ~... Q) 0.04 OJ ~ i! co ., U 0.02 0 0 2 4 6 8 10 12 14 16 18 20 calyx diameter (mm) mean <str<strong>on</strong>g>of</str<strong>on</strong>g> all sizes + y = 0.021 +0.002x 0.10 ~- !: 0.08 .e C1 ~ 0.06 QI .. to .. Q) 0.04 u ~ to ~ 0.02 U ~- I: "e OJ ~ Q) .. ~Q) 0.10 i i :u 0.02 R2 = 0.67, p
Effect <str<strong>on</strong>g>of</str<strong>on</strong>g> different grain sizes There were no significant differences in clearing efficiency after 10, 100 <strong>and</strong> 1000 min, total clearing efficiency, <strong>and</strong> clearing rates between the three types <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> used (ANOVAs, F=2.554, p=0.09 after 10 min; F=0.773, p=0.47 after 100 min; F=0.125,p=0.88 after 1000 min; F= 1.19, p=0.32 for clearing rate, F=0.373, p=0.69 for clearing efficiency). Reacti<strong>on</strong>s to c<strong>on</strong>tinuous <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> applicati<strong>on</strong> Levels <str<strong>on</strong>g>of</str<strong>on</strong>g> activity In Faviafavus, Favites pentag<strong>on</strong>a <strong>and</strong> Platygyra daedalea, c<strong>on</strong>tact with <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> led to inflati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> polyps. C<strong>on</strong>tinued cover resulted in the extrusi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> mesenterial filaments. After I wk <str<strong>on</strong>g>of</str<strong>on</strong>g> c<strong>on</strong>tinuous <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> cover many <str<strong>on</strong>g>of</str<strong>on</strong>g> the polyps were fully extended with inflated peristome. This behaviour c<strong>on</strong>tinued throughout the entire experimental period. Gyrosmilia interrupta retracted tentacles, which during short-term <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> applicati<strong>on</strong> were active in removing <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g>. Reacti<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> scleractinia are summarized in Table 2. Alcy<strong>on</strong>acea, except Lobophytum depressum, retracted all polyps with the <strong>on</strong>set <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> applicati<strong>on</strong> <strong>and</strong> most col- <strong>on</strong>ies inflated. Specimens which suffered tissue damage remained c<strong>on</strong>stantly inflated, while other specimens showed no c<strong>on</strong>sistent pattern. Maximum inflati<strong>on</strong> led to about 30% volume increase compared to c<strong>on</strong>trol c<strong>on</strong>diti<strong>on</strong>s. Some Sarcophyt<strong>on</strong> glaucum col<strong>on</strong>ies became limp <strong>and</strong> deflated at times. This aided to clear <str<strong>on</strong>g>of</str<strong>on</strong>g>f <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g>. In these specimens, inflati<strong>on</strong> alternated with deflati<strong>on</strong>, Behavioural reacti<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> alcy<strong>on</strong>acea are summarized in Table 2. Tissue necroses These were defined as macroscopically visible areas in which body wall tissue had retreated or was in the process <str<strong>on</strong>g>of</str<strong>on</strong>g> retreating, <strong>and</strong> the lighter subepidermal cell-layers were clearly visible. 523 In scleractinia, tissue necroses appeared after 15 d. In Favia favus, Favites pentag<strong>on</strong>a <strong>and</strong> Platygyra daedalea necroses formed predominantly <strong>on</strong> the col<strong>on</strong>y periphery, in Gyrosmilia interrupta in the col<strong>on</strong>y centre. Over the next 2 wk, necroses healed <strong>on</strong> <strong>on</strong>e Faviafavus. On other specimens, tissue necroses approximately doubled their size. In all species, tissues appeared very thin <strong>and</strong> early necroses most frequently appeared <strong>on</strong> the tops <str<strong>on</strong>g>of</str<strong>on</strong>g> the thecae. After 4 wk, most tissue necroses were stable. Only <strong>on</strong>e Favires pentag<strong>on</strong>a lost two thirds <str<strong>on</strong>g>of</str<strong>on</strong>g> its tissue. In all other <strong>corals</strong>, <strong>on</strong>ly individual polyps or series <str<strong>on</strong>g>of</str<strong>on</strong>g> up to three polyps were lost. Reacti<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> scleractinia to c<strong>on</strong>tinuous <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> applicati<strong>on</strong> are summarized in Table 2. In alcy<strong>on</strong>acea, tissue necroses were present in Lobophyturn depressum prior to the experiment <strong>and</strong> increased in size within 3 d. New tissue necroses formed <strong>on</strong> <strong>on</strong>e L. venustum <strong>and</strong> Sinularia leptoclados. In Sarcophyt<strong>on</strong> glaucum, tissue necroses appeared <strong>on</strong> the hood <strong>and</strong> the stem. After 14 d<strong>on</strong>e S. glaucum <strong>and</strong> <strong>on</strong>e L. depressum died. Necroses c<strong>on</strong>tinued to form <strong>and</strong> enlarge in all alcy<strong>on</strong>acea. These were mostly round pits, which kept enlarging towards their periphery. Most necroses were located in flat parts. The most serious necroses were found <strong>on</strong> S. glaucum <strong>and</strong> L. depressum. However, while S. glaucum tended to die very quickly after the <strong>on</strong>set <str<strong>on</strong>g>of</str<strong>on</strong>g> necroses, L. depressum c<strong>on</strong>tinued to live, despite serious tissue damage. Reacti<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> alcy<strong>on</strong>acea to c<strong>on</strong>tinuous <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g> applicati<strong>on</strong> are summarized in Table 2. Bleaching Serious bleaching was observed after 5 wk <strong>on</strong> the alcy<strong>on</strong>acea Lobophytum venustum <strong>and</strong> Sinularia dura. Only the central fiat part <str<strong>on</strong>g>of</str<strong>on</strong>g> the col<strong>on</strong>y was affected. The ridges, which at no stage were completely covered by <str<strong>on</strong>g>s<strong>and</strong></str<strong>on</strong>g>, did not bleach. Significant differences were found in the chlorophyll c<strong>on</strong>centrati<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> bleached <strong>and</strong> n<strong>on</strong>-bleached parts in two <str<strong>on</strong>g>of</str<strong>on</strong>g> the three species (Table 3). Oftbe scleractinia, <strong>on</strong>ly <strong>on</strong>e specimen <str<strong>on</strong>g>of</str<strong>on</strong>g> Favites pentag<strong>on</strong>a bleached shortly after the beginning <str<strong>on</strong>g>of</str<strong>on</strong>g> the experiment. Table 2 Resp<strong>on</strong>ses <str<strong>on</strong>g>of</str<strong>on</strong>g> scleractinia alcy<strong>on</strong>acea to l<strong>on</strong>g-tenD sedimentati<strong>on</strong> during a 6-wk experimental period. Only resp<strong>on</strong>ses observed for more than at least I wk at a time are noted Hydrostatic inflati<strong>on</strong> Tentacular activity Increased mucus C<strong>on</strong>gealed sediment Small necroses Large necroses Death <str<strong>on</strong>g>of</str<strong>on</strong>g> col<strong>on</strong>ies Local bleaching Scleractinia Alcy<strong>on</strong>acea Favia Favites Platygyra Gyrosmilia favus pentag<strong>on</strong>a daedalea interrupta Yes No Yes Yes Yes No No No Yes No Yes Yes Yes Yes No Yes Yes No Yes Yes Yes No No No No No Yes Yes Yes No No No Lobophytum L. venustum Sinularia S. leptoclados Sarcophyt<strong>on</strong> depressum dura glaucum Yes Partly Yes Yes Yes Yes Yes No Yes No Yes Yes Yes No No Yes Yes No Yes Yes Yes No No Yes Yes No Yes Yes YesNo No Yes No Partly YesNo Yes Yes YesNo