Grazing effects by Nereis diversicolor on development and growth of green algal mats

Nereis diversicolor is generally considered to be a predator and deposit feeder, but have also been found to graze on benthic algae in shallow coastal areas. In this study we investigated the grazing effects on the development and growth of green algae, Ulva spp. Algal growth was studied in an experiment including two levels of sediment thickness; 100 mm sediment including macrofauna and 5 mm sediment without macrofauna, and three treatments of varying algal biomass; sediment with propagules, sediment with low algal biomass (120 g dry weight (dwt) m^− 2) and sediment with high algal biomass (240 g dwt m^− 2). In the 100 mm sediment, with a natural population of macrofauna, N. diversicolor was the dominating (60% of total biomass) species. After three weeks of experimentation the result showed that N. diversicolor was able to prevent initial algal growth, affect growth capacity and also partly reduce full-grown algal mats. The weight of N. diversicolor was significantly higher for polychaetes in treatments with algae added compared to non-algal treatments. There were also indications that a rich nutrient supply per algae biomass counteracted the grazing capacity of N. diversicolor.     

A potential new threat on the coral reefs of Puerto Rico: The recent emergence of Ramicrusta spp.

The rapid appearance of Ramicrusta spp. is described and analyzed from 40 permanent monitoring coral reef stations in Puerto Rico. Before 2016, Ramicrusta had not been observed from any of the reef monitoring stations. By 2018, it was present at 76% of all the monitoring stations. Ramicrusta was the dominant substrata type at all of the shallow reef sites sampled on the east coast (e.g., Fajardo, Culebra, and Vieques), reaching a cover (±SE) as high as 63.0 ± 5.8%. The spread of Ramicrusta occurred at the expense of historically resilient living benthic elements, such as turf algae. Since its detection in 2016, colonization of hard substrata by Ramicrusta remained constant, with the exception of two shallow reefs in Fajardo and Culebra, where the cover was significantly reduced by the scouring and or abrasive effects of two major hurricanes. The ecological implications of Ramicrusta prevalence on Puerto Rican reefs remain unclear; however, increasing herbivory might be a useful mitigation tool in the reduction of Ramicrusta abundance on coral reefs.     

太湖微囊藻对几种枝角类种群影响的实验生物学分析

微囊藻是形成蓝藻水华最普遍的一种,不同枝角类受微囊藻的影响不同.实验从太湖梅梁湾分离天然的微囊藻,研究了其对长刺溞、隆线溞、短尾秀体溞和角突网纹溞四种枝角类存活和生殖的影响.在微囊藻食物浓度为1×106 cells/ml,测得四种枝角类的半致死时间(LT50)分别为长刺溞3.03 d、隆线溞3.79 d、短尾秀体溞8.48 d和角突网纹溞9.25 d,体长较小的短尾秀体溞和角突网纹溞的半致死时间相对较长;实验过程中没有观察到长刺溞和隆线溞有新生幼体,而短尾膊秀体溞和角突网纹溞在少数几天里产出了少量新生幼体.以不同浓度微囊藻(0.5×106-8×106 cells/ml)喂养枝角类,测得四种枝角类的24h半致死浓度(LC50)分别为:4.10×106、4.78×106、6.21×106和7.77×106 cells/ml.参照以栅藻喂养的枝角类生长情况,可知太湖微囊藻对四种枝角类的存活和生殖有很强的负面作用,其中体长较大的长刺溞和隆线溞受的影响相对较大.     

低氧化还原电位对铜绿微囊藻(Microcystis aeruginosa)生长的抑制及恢复的影响

在实验室光照黑暗交替培养下,用半胱氨酸下调黑暗起始时的氧化还原电位(ORP),研究低电位对铜绿微囊藻(Microcystis aeruginosa FACHB 469)生长的影响,并探索低电位胁迫消除后铜绿微囊藻生长的恢复潜力.结果表明,在-50～-100 mV范围内水体ORP越低,其对铜绿微囊藻生长的抑制作用越强.低ORP可抑制铜绿微囊藻对磷的吸收,且这种抑制程度与电位变化无关.-50～-75 mV的电位对铜绿微囊藻SOD酶活性有促进作用,而-90～-100 mV电位明显抑制SOD酶活.当低ORP胁迫消除后,铜绿微囊藻能够恢复至最初的生长状态,同时伴随含磷量的提高和SOD酶活的恢复,-50～-75 mV电位胁迫对藻消除胁迫后的生长更有促进作用.因此,低ORP对铜绿微囊藻的生长会产生不利影响,但是该影响是可逆的.     

温度波动对浮游藻类生长及多糖组成的影响

以铜绿微囊藻、蛋白核小球藻及梅尼小环藻为研究对象,分析了春季藻类演替期间主要门类藻对温度波动的响应,实验在恒温(20℃)和昼夜波动(20±5℃)2种温度模式下测定了3种藻的生长和不同形态多糖含量的变化.结果表明,蛋白核小球藻的生长曲线在不同处理条件下没有显著性差异,铜绿微囊藻和梅尼小环藻的生长曲线在波动温度组显著低于恒定温度组,而且温度波动对梅尼小环藻的生长抑制明显强于铜绿微囊藻.随着实验的进行,3种藻在2个温度处理组中的生长速率逐渐趋近,无显著差异,但是在实验中段3种藻的生长速率对2个温度处理的响应差异显著,其中温度波动对蛋白核小球藻的生长速率起到了显著的抑制作用,对梅尼小环藻起到短暂的显著抑制作用,而对铜绿微囊藻的生长速率无显著性影响,表明铜绿微囊藻对短期(3~6 d)的温度波动表现出较强的适应能力.铜绿微囊藻的游离多糖含量在温度波动条件下显著增加,而固着多糖和总多糖的含量显著减少;蛋白核小球藻和梅尼小环藻多糖的含量没有显著性变化,表明温度波动可能不利于铜绿微囊藻固着多糖的积累.因此,相对短期的温度波动有利于铜绿微囊藻生长优势的确立与维持,而相对长期的温度波动可能会通过影响铜绿微囊藻固着多糖的积累而影响其生长优势的维持.     

西太平洋帕劳砗磲高分辨率氧同位素记录及其指示的气候环境变化

砗磲是海洋中最大的双壳类贝壳,其碳酸盐壳体通常具有年纹层和天纹层,是一种理想的高分辨率古气候研究载体.氧同位素是砗磲古气候研究中最常用的指标之一,但在将其应用于古气候重建之前,通常需要对其现代地球化学过程进行准确的校准.帕劳群岛位于西太平洋暖池西北边缘,其珊瑚礁盘具有丰富的砗磲壳体资源,为开展古气候研究提供了丰富的材料...     

太湖底泥水华蓝藻复苏的模拟

本实验采集太湖梅梁湾底泥及上覆水,在保持底泥表面完整的前提下在实验室中建立湖泊生态系统模拟装置,探索太湖底泥中蓝藻种群的复苏规律经60d光照升温培养,显微观察蓝藻复苏细胞,测定底泥和上覆水中的色素含量.结果表明,在室内模拟条件下,太湖底泥蓝藻复苏初始时主要以2-8个细胞的小群体存在,其细胞直径为7.2-7.8μm,大于夏季的藻群体中的细胞直径(4.8-6μm).底泥蓝藻的复苏过程与环境温度变化密切相关.蓝藻在水体温度达到14℃时开始少量进入水柱中,在环境温度升至18-20℃之间时大量进入水中,为水华形成提供了种源.底泥蓝藻的最佳复苏温度(18-20℃)高于非蓝藻的复苏温度(14-18℃),高温对蓝藻复苏更为有利     

赤潮铜绿微囊藻rDNA基因间隔区的序列分析以及与淡水微囊藻的比较

采用ＰＣＲ及序列测定 厦门西港海域采集的赤潮铜绿微囊藻１６Ｓ和２３Ｓ ｒＤＮＡ基因间隔区Ｉｎｔｅｒｇｅｎｉｃ Ｓｐａｃｅｒ Ｒｅｇｉｏｎ（ＩＳＲ）区进行了序列测定和分析,并通过与两种淡水微囊藻的比较,找出了其特征性核苷酸作为专一性分子探针设计的靶序列,为该藻种以及微囊藻属的快速鉴定及系统学研究提供了分子基础。     

锗对几种微藻生长的影响

根据锗对微囊藻、聚球藻和钝顶螺旋藻生长影响的研究表明，锗对藻类生长的影响因种类而异：微囊藻对锗的耐受能力较强，在培养范围内（０￣２５ｍｇ／ｄｍ＾３，ＧｅＯ２），锗对其生长具促进作用；钝顶螺旋藻的正常生长浓度要低于２５ｍｇ／ｄｍ＾３，当锗浓度达２５ｍｇ／ｄｍ＾３时，生长受明显抑制；聚球藻对锗较敏感，锗浓度超过１２．５ｍｇ／ｄｍ＾３时会抑制其生长，甚至起毒害作用。文中还探讨了锗对藻类生长影响与藻细胞所     

我国马尾藻中砷的化学形态及其季节变化

于１９９６年３－８月在广东、广西及青岛沿海采集了部分代表性马尾藻,采用银盐分光光度法对新鲜样品中砷的化学形态,季节变化进行了研究。结果表明,广东,广西沿海马尾藻的总砷和无机砷含量较高,其中羊栖菜的无机砷含量占其总砷的５６．７３％,说明马尾藻富集无机砷的能力较强。青岛沿海鼠尾藻和海黍子的总砷含量在生长初期最低,成熟增至最高,无机砷占总砷的比例也表现出类似的季节变化,说明藻体砷含量与其生长周期有密切联