2012年春季和秋季长江口无脊椎动物群落结构及其与环境因子的关系

根据2012年春季和秋季长江口及邻近海域无脊椎动物的底层拖网资料和环境调查数据,分析了该海域春、秋季无脊椎动物群落结构特征及其与环境因子的关系。结果表明,长江口及邻近海域2个季节共捕获无脊椎动物5目14科25种,其中甲壳动物是最主要的无脊椎动物类群。长江口无脊椎动物资源量占优势的种类包括三疣梭子蟹(Portunus trituberculatus)、脊腹褐虾(Crangon affinis)、细点圆趾蟹(Ovalipes punctatus)和葛氏长臂虾(Palaemon gravieri),春季和秋季对无脊椎动物资源量贡献最大的种类不同。各站次Margalef种类丰富度指数(D)的范围在0.31~2.02之间,ShannonWiener多样性指数(H′)的范围在0.37~1.92之间,Pielou均匀度指数(J')的范围在0.17~0.95之间。春季和秋季长江口无脊椎动物资源量和多样性季节间变异不显著。等级聚类分析(CLUSTER)和非参数的多维标度排序(NMDS)分析表明,无脊椎动物样本可以区分为春季组与秋季组2个组群。单因子相似性分析(ANOSIM)表明,春、秋季组群间无脊椎动物群落结构差异极显著。典型对应分析(CCA)表明,表层磷酸盐、底层溶解氧、底层硅酸盐和底层硝酸盐是影响长江口及邻近海域无脊椎动物群落结构变异的主要环境因子。长江口无脊椎动物季节变异主要体现在种类的季节演替上,营养盐和溶解氧浓度是无脊椎动物种类季节分布的主要限制因素。     

南黄海大型底栖生物生态调查与研究

根据2008年9月第十二次中韩黄海环境联合调查底栖生物的调查资料整理而成,并与2006年的资料进行比较,分析研究了南黄海海域大型底栖动物的环境质量状况。结果表明,底栖生物种类组成以多毛类居首,软体动物次之。大型底栖生物的栖息密度、生物量和种类数基本上呈现沿岸高,黄海中部低的空间分布特征。调查海域东北部的B3站位是相对稳定的底栖生物栖息密度和生物量高值区。调查海域大型底栖生物可划分为7个群落,以临近长江口的群落Ⅶ的多样性指数和丰富度最高。靠近中国沿岸的群落的生物量组成与临近韩国的群落显著不同。中国与韩国的部分近岸海域均受到一定的人为扰动,但未发现有相互污染的情况。除群落Ⅳ和群落Ⅵ多样性指数和丰富度较低外,其它群落多样性指数和丰富度尚可,群落结构基本稳定。     

东海南部海域头足类群落结构特征及其与环境关系

根据2008年春(5月)、夏(8月)、秋(11月)、冬(2009年2月)四季东海区桁杆拖虾网调查期间所采集的头足类资料,分析了东海南部海域头足类种类组成及优势种,采用生态多样性指数分析了群落物种多样性,并运用典范对应分析法研究了头足类群落变化与主要环境因子的关系。结果表明:东海南部海域共捕获头足类22种,隶属于3目6科8属,优势种主要有神户乌贼(Sepia kobiensis)、双喙耳乌贼(Sepiola birostrata)、短蛸(Octopus ocellutus)和杜氏枪乌贼(Loligo duvaucelii)等;种类丰富度指数D变化范围为0—1.30,多样性指数H′变化范围为0—1.69,均匀度指数J变化范围为0.02—1.00,t检验表明,各群落多样性指数四季之间的差异均不显著(P0.05);根据典范对应分析认为,底层水温为影响调查海域头足类种类组成的主要环境因子。     

胶州湾女姑口潮间带大型底栖动物群落生态学研究

根据2003年8月至2004年5月间夏、秋、冬、春4个季度月,对位于胶州湾内女姑口潮间带的高潮带、中潮带和低潮带所设的3个站进行的大型底栖动物生态调查并分析所获得的资料,采用Shannon-Wiener指数(H′)、物种丰富度指数(D)和物种均匀度指数(J)以及Jaccard的群落种类相似性指数Ja分析该潮间带不同潮区大型底栖动物的物种多样性和群落种类组成的相似程度。结果表明,本次调查共采到大型底栖动物57种,其中软体动物24种,占42.11%;甲壳动物和多毛类各15种,占26.32%;鱼类2种,占3.51%;螠虫1种;女姑口潮间带高、中和低潮区生物种类和生物组成均差别较大,两两群落相似性系数也比较低;3个多样性指数H′,D,J的值大小顺序为低潮区>中潮区>高潮区;女姑口潮间带物种多样性指数季节性变化明显,H′和J为春季最高、冬季最低;D为秋季最高、春季最低。     

南麂列岛海域蟹类群落结构及其与环境因子的关系

根据2013年11月、2014年2月、5月、9月在南麂列岛国家海洋自然保护区海域进行生物资源调查所获得的资料,分析了南麂列岛海域蟹类种类组成、优势种、生物多样性等群落结构特征,并定量分析了群落结构与水文环境因子之间的关系。结果表明,周年4个季度月调查共鉴定出蟹类21种,隶属7科、12属,其中优势种为三疣梭子蟹（Portunus trituberculatus）、日本蟳（Charybdis bimaculata）和双斑蟳（Charybdis bimaculata）3种。不同季节的蟹类种类组成差异较大,而优势种类组成变化较少,其中,以秋季的蟹类种类数最多,冬季最少。从不同水深区域的渔获种类分布趋势来看,蟹类种类以20~30 m水深带较多,30~40 m水深带较少。夏季多样性指数低于其他季节,以水深来看,多样性指数在10~20 m水深带较高,30~40 m水深带较低,蟹类多样性指数与水深呈反比。根据冗余分析认为,水深、水温和盐度是影响调查海域蟹类种类组成和群落结构特征的主要环境因子。     

近年来安海湾及邻近海域春季大型底栖动物群落结构的变化

根据2008、2010、2013年3个年度春季在安海湾及邻近海域7个站位的生态调查数据,对该海域的大型底栖动物种类组成及其群落变化进行研究.结果表明:调查海域春季大型底栖动物共计198种,种类组成上以多毛类和甲壳动物为主,不同年度的物种数由2008年的98种逐次增至2013年的118种,且软体动物比例呈上升趋势.单因素相似性分析表明3个年度的群落结构不存在显著差异,但历年调查的优势种组成已有所变化,尤其是2013年的优势种明显不同于前2个年度.3个年度的平均密度介于369~780个/m2,平均生物量介于23.22~40.10 g/m2,物种丰富度指数d介于3.693~4.265,多样性指数H'介于3.076~3.782,密度逐次降低,生物量2010年最低,而物种丰富度指数d和多样性指数H'呈现2010年最高,前后年度低的特点.空间分布上,安海湾外的站位平均物种数和多样性指数H'高于湾内.聚类结果表明,安海湾内外的群落相似性低,且优势种组成明显差异.与1989年相比,安海湾底栖动物群落发生明显改变.迹象表明,较之前2个年度,2013年安海湾底栖动物群落出现新变化.     

烟台近海大型底栖动物群落特征

为了解烟台近岸海域大型底栖动物群落现状,分析群落演替特征,并在此基础上探讨引发群落演替的原因,于2010年4月、8月、11月及2011年3月4个航次（春、夏、秋、冬）对烟台近海大型底栖动物进行周年调查分析。采用优势度指数、物种多样性指数、丰富度指数、均匀度指数、Cluster聚类和MDS排序分析大型底栖动物群落特征,并与历史资料比较分析群落演替情况。结果表明,该海域共采集到大型底栖动物176种,其中多毛类77种,软体动物46种,甲壳动物39种,棘皮动物7种,其他7种。群落中的优势种组成季节性差异较小,基本保持稳定,短叶索沙蚕和不倒翁虫为4个季度共有优势种。烟台近海年平均生物量为16.72 g/m2,以秋季最高,春季最小;年平均丰度为1022 ind/m2,以冬季最高,春季最低。丰富度指数（D）、均匀度指数（J）和多样性指数（H’）的年平均值分别为2.30、0.70和1.91。聚类分析结果表明,大型底栖动物群落结构与底质和水深关系密切,但是由于受到不同类型的环境扰动,大型底栖动物群落呈现斑块状分布。与上世纪90年代相比,群落特征发生了一定程度的变化,表现为物种数下降,群落中优势类群的比例和优势种组成发生了变化,群落中软体动物比例减少,多毛类比例增加。人类活动包括污水排放、养殖和捕捞、港口建设和船舶航运等干扰是导致调查海域大型底栖动物种类组成及数量变化的主要原因。     

象山港大型底栖动物群落特征

2006年7月—2008年8月,对象山港全港海域设立的13个采样站位采集的调查资料,用物种丰富度指数、物种均匀度指数和物种多样性指数分析象山港大型底栖动物物种的多样性和群落种类的组成,以及采用ABC曲线方法和大型多元统计分析软件PRIMER5对象山港大型底栖动物进行Bray-Curtis相似性聚类分析和非度量MDS标序,研究象山港大型底栖动物群落结构。调查显示象山港大型底栖动物不同采样站位之间物种丰富度指数(d)、均匀度指数(J)、辛普森多样性指数(D)和香农-威纳多样性指数(H’)差异皆高度显著(P0.01)。群落结构聚类分析和MDS标序表明,13个采样站位的大型底栖动物群落大致可分为3组。根据所调查象山港大型底栖动物的丰度和生物量资料做的ABC曲线分析表明,该海域大型底栖动物群落受到了严重的环境污染或者扰动,逐渐由一种或几种个体较小的种类占优势。     

2016年莱州湾扇贝养殖区浮游植物群落生态特征

为了解莱州湾扇贝养殖区海域浮游植物群路结构变化特征,于2016年4—11月对其8个扇贝养殖区的浮游植物进行了逐月调查,并采用群落Shannon-Wiener多样性指数(H′)、Margalef丰富度指数(D)、Pielou均匀度指数(J)等方法对浮游植物多样性进行了分析。本调查共鉴定浮游植物5门96种(属),其中硅藻门(Bacillariophyta)最多,有63种,其次为甲藻门(Pyrrophyta)和绿藻门(Chlorophyta),分别有14、9种,金藻门(Chrysophyta)和隐藻门(Cryptophyta)最少,各5种。5门浮游植物均存在优势种,其中硅藻门种类最多,且在个别月份形成绝对优势。浮游植物密度在0.51×10^4~112.04×10^4 cell/L之间,在6、9月出现高峰值;多样性指数在1.06~3.92之间,均匀度指数在0.26~0.96之间,物种丰富度指数在2.09~4.89之间。调查结果表明莱州湾扇贝养殖区浮游植物种类较多,多样性指数较高,群落结构较复杂,生态环境较稳定。     

岱衢洋拖网甲壳动物多样性的季节变化

根据2010年春季(5月)、夏季(8月)、秋季(11月)与2011年冬季(2月)对岱衢洋进行的共4个航次的底拖网渔业资源调查资料,对该海域的甲壳动物多样性进行了分析。结果表明,共捕获甲壳动物21种,其中虾类13种、蟹类7种、虾蛄类1种,隶属于2目14科18属;甲壳动物的生物量与尾数密度均以秋季为最高,春季则正好相反,且该两季的生物量与尾数密度间差异均显著(P<0.05);广温广盐种在种类数量、生物量与尾数密度方面均居主导地位;Margalef丰富度指数(D)、Shannon-Wiener多样性指数(H′)和Pielou均匀度指数(J′)的最小值均出现在冬季,表明该季甲壳动物群落的丰富度、多样性与均匀性都较低,另外,D值、H′值夏、秋两季高,冬、春两季低,与较外海域的情况正好相反,这主要是其对底层水温季节变化的一种响应。     

长江口及其邻近海域大型底栖动物生物量、丰度和次级生产力的初步研究

为了解长江口及邻近海域大型底栖动物生物量、丰度和次级生产力的分布情况于2004年2月、5月、8月和11月共4个航次分别在长江口40个观测站采集大型底栖动物定量样品并利用Brey的经验公式对大型底栖动物栖息丰度、生物量、次级生产力和P/B值进行了研究计算.该调查海域共采到大型底栖动物202种,其中多毛类102种,软体动物51种,甲壳类27种,棘皮动物7种,其它动物15种.大型底栖动物年平均丰度为394.7 ind/m2;年平均生物量以去灰分干重计,为2.58 g(AFDW)/m2;年平均次级生产力以去灰分干重计,为3.52 g(AFDW)/(m2*a);P/B值平均为1.53.结果表明,长江口大型底栖动物次级生产力自长江入海口向东呈递增趋势.本文分析了长江口及其邻近海域大型底栖动物优势种的组成,主要生态类群的分布特征和次级生产力分布格局与生态环境的关系.通过比较,发现长江口大型底栖动物优势种发生了较大的变化;次级生产力高于东海而低于渤海和胶州湾;P/B值高于南黄海、胶州湾和渤海,也说明了长江口大型底栖动物群落中个体小、生活史短,代谢快的种类所占的比例高于以上海域.     

赤潮异弯藻和海洋原甲藻LSU Rdna扩增及序列分析

利用引物D1R和D2C扩增并测定了赤潮异弯藻(Heterosigma akashiwo Hada)和海洋原甲藻(Prorocentrum micans Ehrenberg)的LSU rDNA D1与D2序列,并与GenBank中相关序列进行比较分析.结果表明:在种内水平,所测的H.akashiwo 6个株系之间共有5个变异位点,序列H.k与H.k-2,H.k-4均存在碱基替换;原甲藻属不同种内各株系之间的遗传距离为0.002～0.023之间,所测序列P.mi与P.micans其他株系之间均存在碱基替换.在种间水平上,原甲藻属不同种之间的遗传距离在0.045～0.139之间,大于种内遗传距离,每个种都具有特定的保守序列.根据序列间的遗传变异,可设计特异性的探针对不同株系和物种进行检测和计数.     

Complexation of Cu,Zn and Cd by metabolites excreted from marine diatoms

The excretion of photosynthetically fixed carbon from cultured marine diatoms and its influence on Cu, Zn and Cd complexation in seawater was studied for three species. For each species, an isolate from oligotrophic waters was compared with an estuarine isolate. Complexation of metal was determined with the use of differential pulse anodic stripping voltammetry. Excreted material from cells in log-phase growth complexed Cu > Zn > Cd, while material derived from senescent cells complexed only Zn. The filtrates of all cultures complexed these metals comparably with natural coastal seawater. There were no appreciable differences in complexing ability within or among species, suggesting that no excretion-complexation ‘strategy’ peculiar to each ecosystem exists among these species.     

小洋山邻近海域主要游泳动物生态位及种间联结性

根据2014年秋季和2015年秋季在小洋山邻近海域调查获得的渔业资源资料,运用生态位测定、聚类分析、W检验、基于2×2列联表的χ2检验、联结系数（AC）和共同出现百分率（PC）等方法分析主要游泳动物间的生态关系。结果表明,该海域主要游泳动物共24种,其中优势种为龙头鱼（Harpodon nehereus）、三疣梭子蟹（Portunus trituberculatus）和安氏白虾（Exopalaemon annandalei）,这3个种类的生态位宽度较宽;通过生态位宽度聚类分析,可将主要游泳动物分为3组,分别为广生态位种、中生态位种和狭生态位种;种对间生态位重叠值介于0~0.96之间,表明物种利用资源的能力具有相似性,种对间存在一定竞争性;W检验分析得出主要游泳动物总体呈显著正关联;χ2检验显示有150个种对的联结性显著（χ2 ≥ 3.841）;联结系数（AC）和共同出现百分率（PC）表明种间联结性较强,总体趋于正相关。     

泰国近海习见有毒立方水母和钵水母的遗传分析

本研究利用线粒体16S rDNA和核基因18S rDNA片段,对泰国沿海常见的有毒水母进行遗传分析,并比较了2个基因片段作为通用分子标记,在研究水母类多个纲的遗传多样性中的应用。研究发现,泰国近海的有毒水母存在较高的遗传多样性,所获得的32个样品可以分为9个种,包括4种钵水母、4种立方水母和1种水螅水母。然而,完全确定各种的分类地位,还需要更多的形态、生活史等方面信息。两个基因片段均能明确区分各种类,但核基因18S序列比线粒体基因片段更为保守。根据16S基因片段序列计算水母种内和种间的K2P(Kimura 2-parameter)遗传距离,发现所研究的9个水母种类,种内遗传距离在0~0.050之间,其中94%的种内遗传距离小于0.040,同纲种间的遗传距离为0.204~0.474,其中91%的种间遗传距离大于0.250;而利用18S基因,种内距离在0~0.002之间,同纲种间距离为0.008~0.066(平均为0.038,SE=0.006)。16S的AT碱基含量明显高于核基因18S,且16S的碱基含量在不同纲之间有显著差异,进一步表明水母线粒体16S基因的突变率相对较高,适合研究水母较低分类阶元以及种下的遗传差异。     

防城河口湾鱼类群落结构及其与环境因子关系研究

文章根据2016年5月、8月、11月和2017年2月在防城河口湾海域进行的渔业资源和环境调查数据, 研究了河口湾鱼类群落结构及其空间和季节变化, 分析了鱼类群落结构与主要环境因子的关系。结果表明: 全年调查共渔获鱼类95种, 隶属于2纲12目37科69属, 适温性以暖水性鱼类为主, 生态类型以底层和近底层鱼类为主。其中, 春季60种, 夏季59种, 秋季54种, 冬季46种, 夏—秋季间种类相似性指数最高。全年优势种为褐菖鲉Sebastiscus marmoratus和长鳍篮子鱼Siganus canaliculatus, 主要种有黄鳍棘鲷Acanthopagrus latus、条马鲾Equulites rivulatus、李氏?Callionymus richardsoni和真赤鲷Pagrus major等10种; 夏、秋季的最大优势种均为长鳍篮子鱼, 春、冬季的最大优势种分别为褐菖鲉和条马鲾。全湾鱼类年均资源密度为45836尾·km ^-2和 435.21kg·km ^-2, 资源密度具有明显的空间差异和季节变化。全年各站位种数变化范围在2~21种, 多样性指数H′在0.468~4.031, 丰富度指数d在0.120~1.926, 均匀度指数J在0.181~0.969。聚类分析、单因子相似性分析(ANOSIM)及相似性百分比(SIMPER) 分析表明该海域鱼类群落存在一定程度的时空异质性。相关性分析表明影响防城河口湾鱼类群落结构的主要环境因子为水温、盐度和硝酸盐。     

Spatial variation in elemental composition of otoliths of three species of fish (family Sparidae)

Determining the nursery habitat of fishes that have moved from estuarine nursery habitats is difficult. The elemental fingerprints of otoliths of three species of sparids were determined to investigate their utility as a natural tag of the nursery habitat. Juvenile Pagrus auratus (snapper), Rhabdosargus sarba (tarwhine) and Acanthopagrus australis (bream) were collected from two sites in each of 15, six and three estuaries, respectively, and their otoliths analysed by solution-based inductively coupled plasma-mass spectrometry. Significant differences in otolith chemistry were found for all three species of juveniles collected from different estuaries. The same patterns among estuaries were not seen for all species, although it was not possible to sample the same sites within an estuary for all species. For bream, significant differences in otolith chemistry were found among all three estuaries, whereas for tarwhine the six estuaries were separated into three groups. For snapper, a number of estuaries could be separated, but there was some overlap for other estuaries. All three species were collected from the same site within one estuary and their otoliths analysed. Significant differences were found among species, but the implication of this finding remains unclear as the three species show differences in microhabitat use and may also differ in age. Because the elemental fingerprints of juveniles vary among estuaries or groups of estuaries, the nursery or recruitment estuary of adult fish could now be determined by analysing the juvenile region of adult otoliths. Thus, connectivity between estuaries and open coastal populations could be determined. Such information will have major implications for fisheries management because it will provide information on the distance that fish have moved from their recruitment estuary and the number of estuaries that contribute to each adult population.     

The biogeography and community structure of kelp forest macroinvertebrates

Understanding species distributions and their community structure is increasingly important when taking an ecosystem‐based approach to conservation and management. However, knowledge of the distribution and community structure of species in mid‐range trophic levels (e.g. macroinvertebrates) is lacking in most marine ecosystems. Our study aimed to examine the spatial distribution and community‐level biogeographic patterns of common kelp forest–rocky reef macroinvertebrates in Southern California and to evaluate the effects of environmental gradients on these communities. Quantitative SCUBA surveys were used to estimate macroinvertebrate densities at 92 sites from 2008–2012. Non‐metric multidimensional scaling was used to evaluate spatial patterns of macroinvertebrate communities among Regions. We found that kelp forest–rocky reef macroinvertebrate communities are distinct among different island and mainland regions, and their community patterns exhibited a strong relationship with an environmental gradient (i.e. sea surface temperature) even after controlling for geographic distance between sites. High abundances of urchin species (Strongylocentrotus purpuratus and Strongylocentrotus franciscanus) were strong drivers of regional differences. Macroinvertebrate community patterns were driven by characteristic species that were typically more prevalent at warmer or colder sites. Our results provide the first quantitative analysis of macroinvertebrate community structure within the California kelp forest ecosystem. We also describe the distribution and abundance of 92 conspicuous kelp forest‐rocky reef macroinvertebrates among nine pre‐defined Regions. This study provides important preliminary information on these macroinvertebrate species that will be directly useful to inform management of invertebrate fisheries and spatial protection of marine resources.     

Spatio-temporal and interspecific variation in otolith trace-elemental fingerprints in a temperate estuarine fish assemblage

We tested whether estuarine fishes have site-specific differences in the concentrations of trace elements in their otoliths that can be used as ‘fingerprints’ to identify them to their estuary of origin. To evaluate the robustness of this approach, we tested whether elemental fingerprints were consistent among individuals of five species that were collected in 1996 from three temperate estuaries in southern California. We also tested whether elemental fingerprints were consistent between spring and autumn 1996 for three species in one of the sites, Carpinteria Marsh. The species evaluated comprised a mid-water-dwelling smelt (Atherinops affinis), two benthic gobies (Clevelandia ios and Ilypnus gilberti), and two flatfish (Paralichthys californicus and Hypsopsetta guttulata). The concentrations of six elements (Mn, Cu, Zn, Sr, Ba, and Pb) were determined in the otoliths using inductively coupled plasma-mass spectrometry (ICP-MS). Within estuaries, the five species exhibited strong variation in elemental concentration, indicating substantial interspecific differences in otolith environmental history. When the five fish species were considered separately, multivariate (MANOVA) and univariate (ANOVA) analyses of variance indicated that the elemental composition of otoliths differed significantly among the estuaries in four of the five species. Based on linear discriminant function analyses (DFA), differences were strong enough that trace element composition could be used to accurately assign fish to their site of origin [mean (range): 93.5% (74–100%)]. However, elemental signatures within Carpinteria Marsh were not consistent between spring and autumn 1996, and this was reflected in a substantial reduction in the accuracy of assigning fish to their true site of origin. When we compared site differences between fish species (site×species interactions), the elemental fingerprints were most similar between closely related species (e.g. the two gobies and the two flatfish) and most dissimilar between distantly related species, both phylogenetically and ecologically. Among the six elements analyzed, Sr and Ba exhibited the most inconsistent pattern among species, with significant differences in 80 and 70% of the pairwise species comparisons, respectively. The remaining four elements showed ≥70% consistency in the pattern of variation among sites for the different species. Thus, while otolith elemental fingerprinting can be a useful tool for inferring estuarine residency, such fingerprints may be temporally variable and species specific.     

Effects of Larval Settlement and Post-Settlement Mortality on the Distribution Pattern and Abundance of the Spirorbid Tube Worm Neodexiospira brasiliensis (Grube) (Polychaeta) Living on Seagrass Leaves

Abstract. The role of larval settlement, post-settlement mortality and competition with a red algae in determining the patterns of abundance and distribution of the spirorbid tube worm Neodexiospira brasiliensis (Grube) (Polychaeta: Spirorbidae) on leaves of three seagrass species: Zostera marina Linnaeus, Zostera asiatica Miki and Phyllospadix iwatensis Makino were examined in Aininkap, Akkeshi Bay, Akkeshi, Hokkaido, Japan. Field collections of seagrass shoots were made at about 1-week intervals. The density of newly settled larvae (< 0.3 mm in tube diameter) increased significantly on Z. asiatica and P. iwatensis , but not on Z. marina during the sampling period. It was highest on Z. asiatica among the three seagrass species, followed by P. iwatensis and Z. marina . Newly settled larvae occurred more on the basal part of younger leaves of each seagrass species. Mortality tended to be high on Z. marina , followed by Z. asiatica and P. iwatensis , although the differences were not great. Size-specific mortality showed the existence of high mortality in early post-settlement stages on Z. asiatica and P. iwatenisis . Relatively high mortality was also suffered by individuals with a tube diameter over 1.5 mm. Growth in tube diameter of N. brasiliensis was slower on P. iwatensis than on the other two seagrasses. The effect of a calcareous red algae on larval settlement was investigated with removal experiments; however, no effect of red algae was detected. Patterns in the distribution and abundance of N. brasiliensis on leaves of three seagrass species resulted from the heterogeneity of larval settlement rather than from post-settlement mortality or competition with red algae. Different densities of larval settlement among the three seagrass species or on a leaf are likely to relate to larval behaviour, such as negative phototaxis.