Growth rate of coral reef sponges near Discovery Bay Jamaica after Hurricane Allen

In February 1986, specimens of five massive sponge species (Pseudoceratina crassa, Ircinia felix, Verongula ardis, Smenospongia aurea and Agelas dispar) were collected from 20 m depth, approximately 1 km to the west of the Discovery Bay Marine Laboratory in Jamaica. The site was covered by a dense bed of Acropora rubble in excess of half a meter thick, which had accumulated during Hurricane Allen and contained numerous small sponges and coral colonies growing on pieces of the rubble.Regular-shaped animals (presumably derived from a single larva), which were attached to rubble and without obvious signs of predation damage were chosen. The sponges were weighed after draining for approximately 20 seconds and the volume measured by displacement in water. Estimates of dry weight were made on 5 individuals of each species after drying for 36 hours at 80°C.The size-class structure of the Pseudoceratina crassa population was estimated using the MIX program, which is an interactive program used to fit distributions to grouped data by maximum likelihood estimation. For Pseudoceratina crassa, it was assumed that there were five size groupings representing the recruitment from five annual spawning events between Hurricane Allen (August 1980) and the date of collection. The mean size of sponges in each size-class was determined from the significant fit obtained to the size-frequency data with the MIX program. These mean values for each size-class were analyzed using a least squares regression to provide an exponential growth model (Wt = ae^alpha t) from which the relative growth rate alpha was estimated.Growth rates for the other four sponge species could not be obtained by the same method due to the limited number of specimens. Growth rate approximations for these species were derived using the growth model from Pseudoceratina crassa, assuming that the average size at 50 days after spawning was the same for all species. Dates for spawning of these species were extracted from the literature.
Hurricane Allen passed within 50 km of the north coast of Jamaica on 6 August 1980. Large seas generated by winds in excess of 250 km per hour caused extensive damage to the coral reefs in the vicinity of the Discovery Bay Marine Laboratory.

1986年2月，研究人员于牙买加探索湾海洋实验室（Discovery Bay Marine Laboratory）西侧约1公里、水深20米的海域，采集了5种大型海绵标本，分别为厚角海绵（Pseudoceratina crassa）、艾氏海绵（Ircinia felix）、红刺海绵（Verongula ardis）、金黄管海绵（Smenospongia aurea）以及异射海绵（Agelas dispar）。该采样点被厚度超半米的致密鹿角珊瑚（Acropora）砾石床覆盖，这些砾石由艾伦飓风（Hurricane Allen）过境后堆积形成，其上附着有大量小型海绵与珊瑚群落。
研究人员挑选了形态规整、疑似由单一个体幼虫发育而来、附着于砾石且无明显捕食损伤痕迹的海绵个体。海绵经约20秒沥干后称重，并通过排水法测定体积。针对每个物种的5个个体，在80℃下烘干36小时后估算其干重。
厚角海绵（Pseudoceratina crassa）种群的尺寸分级结构通过MIX程序（MIX program）估算得到——该程序为交互式工具，可通过最大似然估计法将分布拟合至分组数据。针对厚角海绵，研究人员假设存在5个尺寸组，对应1980年艾伦飓风（1980年8月）至本次采样时段间的5次年度产卵事件的补充群体。利用MIX程序对尺寸频率数据进行有效拟合后，可确定每个尺寸组内海绵的平均尺寸。通过最小二乘回归分析各尺寸组的平均尺寸值，构建指数生长模型（Wt = ae^αt），并据此估算相对生长率α。
其余4种海绵因标本数量有限，无法采用相同方法获取生长速率。研究人员假设所有物种在产卵后50天的平均尺寸一致，基于厚角海绵的生长模型推导得到这4种海绵的生长速率近似值。上述物种的产卵日期均从已发表文献中提取。
1980年8月6日，艾伦飓风途经牙买加北海岸附近50公里海域，其风速超250公里/小时所引发的巨浪，对探索湾海洋实验室周边的珊瑚礁造成了大面积破坏。