Coastal Watershed Institute, Florida Gulf Coast University, 10501 FGCU Blvd South, Fort Myers, FL 33965, USA.
Biology Department, MS #32, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
Harmful Algae. 2021 Mar;103:101998. doi: 10.1016/j.hal.2021.101998. Epub 2021 Feb 13.
Anchored mesh screens have been suggested as a standardized approach to monitor the cell abundances of epiphytic dinoflagellates in benthic habitats, including toxigenic members of the Gambierdiscus genus responsible for ciguatera poisoning (CP). Here we deployed screens for 24h at eight sites in the Florida Keys and St. Thomas (US Virgin Islands) to evaluate their performance relative to the traditional method of assessing Gambierdiscus abundance in which cell counts are normalized to wet weight of host algae. The 30-month study (April 2013 - August 2015) involved monthly sampling at sites where screens were suspended at near-bottom locations for a 24h period and retrieved, with concurrent collections of macrophytes; including Halimeda, Laurencia, and Thalassia in the Florida Keys, and Dictyota in both regions. Gambierdiscus cells were identified and enumerated in the screen and macrophyte samples, and several regression techniques were evaluated (linear regression using untransformed and log-transformed data; negative binomial distribution (NBD) regression) to determine how well the screen-derived data could estimate algal cell concentrations on the host algae. In all cases, the NBD models performed the best based on Akaike Information Criteria values, although 38% of the regressions were not statistically-significant, including all of the St. Thomas sites. The r values were all < 0.75 and averaged 0.36, indicating relatively poor fit of the screen data. False negative results (regression models underestimating actual cell abundances) were common occurrences, ranging from 5 to 74% of the scenarios tested. In summary, these results indicate that 24h screen deployments do not appear to be consistent in all situations. Caution is therefore needed when considering 24h screens as a standardized monitoring approach for quantifying Gambierdiscus population dynamics across geography and ecosystems. Furthermore, neutral (artificial) substrates may not adequately capture either the host preference or palatability that likely influence the initial vector of toxin incorporation in the food web via herbivory on these macrophytes.
锚定网筛已被提议作为监测底栖生境中附生甲藻细胞丰度的标准化方法，包括产生雪卡毒素（CP）的 Gambierdiscus 属的有毒成员。在这里，我们在佛罗里达群岛和圣托马斯（美属维尔京群岛）的八个地点部署了网筛 24 小时，以评估它们相对于传统方法的性能，传统方法是将 Gambierdiscus 丰度的细胞计数归一化为宿主藻类的湿重。这项为期 30 个月的研究（2013 年 4 月至 2015 年 8 月）每月在网筛悬挂在近底部位置进行 24 小时的站点进行采样，并进行回收，同时收集大型藻类；包括佛罗里达群岛的 Halimeda、Laurencia 和 Thalassia，以及两个地区的 Dictyota。在网筛和大型藻类样本中鉴定并计数 Gambierdiscus 细胞，并评估了几种回归技术（使用未转换和对数转换数据的线性回归；负二项分布（NBD）回归），以确定网筛数据在多大程度上可以估计宿主藻类上的藻类细胞浓度。在所有情况下，NBD 模型根据 Akaike 信息准则值表现最好，尽管 38%的回归没有统计学意义，包括圣托马斯的所有站点。r 值均<0.75，平均为 0.36，表明网筛数据拟合较差。假阴性结果（回归模型低估实际细胞丰度）很常见，测试的场景中有 5%至 74%的情况都是如此。总的来说，这些结果表明，24 小时网筛部署在所有情况下似乎都不一致。因此，在考虑将 24 小时网筛作为跨地理和生态系统量化 Gambierdiscus 种群动态的标准化监测方法时，需要谨慎。此外，中性（人工）基质可能无法充分捕获宿主偏好或适口性，这可能通过这些大型藻类的食草作用影响食物链中毒素最初的纳入。
