北部湾海域小型底栖动物丰度和生物量

根据2008年10月4日至8日北部湾海域生态环境综合调查资料,对北部湾海域小型底栖动物的类群组成、丰度和生物量分布进行了分析研究,结果表明,研究海域的小型底栖动物平均丰度约为399.09±452.20 had·10cm^-2,平均生物量约为359.56±324.45μg·10cm^-2;按丰度来讲,分选出的14个类群中,自由生活海洋线虫的丰度为最优势,约占总丰度的92.69%,其次为底栖桡足类和多毛类,分别约占总丰度的3.28%和2.47%;线虫、多毛类和桡足类分别约占总生物量的41.16%、38.34%和6.76%。研究海域的钦州、防城港市沿岸海区小型底栖动物平均丰度相对较高,其平均丰度约为614.98±799.63 ind·10cm^-2;涠洲岛周边海区和北海南部近岸海区平均丰度分别约为481.68±240.03 ind·10cm^-2和278.14±126.38 ind·10cm^-2;对照海区的小型底栖动物平均丰度约仅有197.37±116.72 ind·10cm^-2。根据各站位小型底栖生物的种类组成及其丰度进行了多样性分析,各站位丰富度指数介于0.466～1.516之间,均匀度指数介于0.203～1.13之间,Shannon-Weiner指数(H')介于0.141～0.783之间。根据类群组成及其丰度进行组平均法聚类分析,把研究海区各站位分成了3个不同的底栖生物群落。研究海区线虫和桡足类丰度的比率变化范围在5.02～223.83之间。     

长江口及其陆架春季小型底栖生物丰度和生物量

2007年4—5月对长江口及其陆架海域小型底栖生物进行了调查。结果表明:调查海域有18个类群小型底栖生物,平均丰度为(1117.19±820.36)个/10 cm2,平均生物量为(754.87±546.37)(μg.干重)/10 cm2,其中线虫是绝对优势类群,占小型底栖生物总丰度的95.42%,占总生物量的55.35%。其他优势类群分别是桡足类、多毛类和动吻类。垂直分布研究表明:小型底栖生物丰度随着深度的增加而减少,其数量的65%分布于0—2 cm层,其中线虫分布于0—2 cm层的数量约占64%;桡足类集中分布于0—2 cm层,占该类总量的88%以上;多毛类分布于0—2 cm层的数量约占61%。各区块小型底栖生物总丰度从高到低依次为东海陆架深水区长江口近岸杭州湾。与环境因子相关分析表明:盐度与小型底栖生物丰度,线虫丰度成显著的正相关,与多毛类,桡足类丰度以及小型底栖生物生物量呈极显著的正相关。近底溶解氧与小型底栖生物丰度,多毛类,线虫丰度以及小型底栖生物生物量呈显著的负相关,与桡足类丰度呈极显著的负相关。调查海域沉积物的中值粒径,粘土粉砂含量与小型底栖生物丰度,多毛类,线虫丰度以及小型底栖生物生物量的相关性不显著。位沉积物叶绿素a和脱镁叶绿素含量与小型底栖生物丰度,线虫丰度、多毛类丰度,桡足类丰度相关不显著;沉积物中异养细菌含量与多毛类丰度呈显著负相关。     

南黄海冬季小型底栖生物丰度和生物量

分别于2003年1月和2004年1月在南黄海广大陆架浅海水域进行小型底栖生物调查.结果表明,两个航次的小型底栖生物平均丰度分别为 (954.20±269.47) ind·10 cm^-2和(1 186.12±486.07) ind·10 cm^-2;平均生物量分别为(954.38±403.93)μg·10 cm^-2和(1 120.72±487.21) μg·10 cm^-2.两个航次小型底栖生物丰度值、生物量和生产力均无显著变化(P>0.05).共鉴定出20个小型底栖生物类群,按丰度,自由生活海洋线虫为最优势类群,两个航次的优势度分别为87%和90%,其他优势类群依次为桡足类、多毛类和动吻类;按生物量依次为线虫34%～38%,多毛类25%～33%,介形类9%～22%,桡足类8%.96.64%的小型生物分布在0～5 cm的表层沉积物内,线虫和桡足类分布在0～2 cm的比例分别为72.48%和89.46%.小型底栖生物的生物量与沉积物砂含量(%)、粉砂含量(%)和叶绿素a含量呈显著相关.代表性站位的种类组成和多样性分析显示了沿岸、黄海冷水团和东、黄海交汇区3个不同的底栖生物群落.     

2005年夏季东太平洋中国多金属结核区小型底栖生物研究

“大洋一号”调查船于2005年7月在太平洋结核区中国合同区东、西小区调查中共进行了12个站位的小型底栖生物的取样.研究表明:调查区域小型底栖生物共有13个类群.东、西两小区小型底栖生物平均密度分别为(104.4±20.48)个/10 cm2,(40.26±25.84)个/10 cm2,线虫平均生物量分别为(5.25±0.99)(μg·干重)/10 cm2,(1.68±0.77)(μg·干重)/10 cm2,东小区小型底栖生物平均密度、线虫生物量明显高于西小区.线虫是绝对优势类群,分别占东、西小区小型底栖生物总密度的93.13％和91.36％,其它优势类群有桡足类,多毛类,介形类等.小型底栖生物密度随着沉积物深度的增加而减少,其数量的75％以上分布在0-2 cm层,东小区深层的小型底栖生物所占比例比西小区要大.与环境因子相关分析表明:调查区域的小型底栖生物密度,线虫密度,线虫生物量,桡足类密度,多毛类密度与经、纬度呈显著负相关,与脱镁叶绿素呈显著正相关,与沉积物微型生物生物量相关性不显著.小型底栖生物密度,线虫密度,线虫生物量,多毛类密度与叶绿素a呈显著正相关,桡足类与叶绿素a相关性不显著.脱镁叶绿素与沉积物微型生物生物量呈显著正相关.     

珠江口伶仃洋海域小型底栖生物丰度和生物量

分别于2006年7-8月(夏)、2007年4月(春)和10月(秋)对珠江口伶仃洋附近海域小型底栖生物丰度和生物量进行调查.3个航次共鉴定小型底栖生物类群15类,包括线虫、桡足类、多毛类、介形类、动吻动物、端足类、颚咽动物、涟虫、纽虫、腹足类、双壳类、星虫、螠虫、原足类和其他未鉴定种类;春、夏、秋3个航次小型底栖生物丰度分别为(272.1+281.9)、(165.1±147.1)和(246.4±369.3) ind·10 cm-2,线虫为主要优势类群,分别占小型底栖生物总丰度的86.8％、83.5％和93.4％.小型底栖生物丰度垂直分布不均匀,分布于沉积物0～2 cm、2～5 cm、5～10 cm的数量比例分别为54.1％、35.2％和10.8％,线虫分布于沉积物0～5 cm数量比例为87.4％;春、夏、秋3个航次小型底栖生物生物量分别为(374.6±346.9)、(274.1±352.2)和(270.8±396.0) μg·10 cm-2,多毛类平均生物量最高,分别占小型底栖生物总生物量的30.1％、46.7％和46.0％,其次为线虫(25.2％、20.1％和34.0％)和介形类(20.6％、15.3％和14.8％).伶仃洋小型底栖生物丰度平面分布呈现从北向南升高、东部高于西部的趋势.伶仃洋小型底栖生物丰度、生物量分布与水深呈显著正相关.     

珠江口水域夏季小型底栖生物群落结构

于2010年8月在珠江口水域进行小型底栖生物取样分析,结果表明,该调查水域夏季小型底栖生物的平均丰度为(183±174)个/10 cm2,平均生物量为(345±334)μg干重/10 cm2,平均生产量为(3104±3008)μg干重/10 cm2。共鉴定出小型底栖生物16个类群,按丰度,自由生活海洋线虫和双壳类幼体为优势类群,其丰度分别占调查水域小型底栖生物总丰度的62.61%和22.62%。按生物量,优势类群由双壳类幼体(50.57%)、线虫(13.33%)和多毛类(12.47%)等组成。81.15%的小型底栖生物分布在0—5 cm的沉积物中。与环境因子相关分析表明:小型底栖生物丰度、线虫丰度与温度呈显著负相关,与盐度呈显著正相关。调查水域线虫与桡足类数量的比值(N/C)呈现出由河口上游向下游递增,且西岸明显高于东岸的趋势。     

青岛湾小型底栖生物周年数量分布与沉积环境

2006年6月至2007年5月对青岛湾潮间带泥沙质和沙质沉积物中的小型底栖生物及环境因子进行了周年逐月采样。研究发现, 小型底栖生物在两个底质中的数量和分布上差异极大, 泥沙质中的年平均丰度高达(4853±1292) 个/10 cm², 沙质中为(1528±569) 个/10 cm², 生物量则分别为(3186.9±1993.4) μg干重/10 cm²和(1601.5±786.2) μg干重/10 cm²。在季节相上, 小型底栖生物丰度在沙质底呈双峰模式 (高值出现在6、12月份, 低值出现在3、9月份); 泥沙质中最高值出现在6月份, 最低值出现在11月份。在0-8 cm 深沉积物中, 48%的小型底栖生物集中于0-0.5 cm 表层, 分布在0-4 cm的逾86%。共发现13个主要类群, 线虫在丰度上占绝对优势(泥沙质中为95%, 沙质中为66%), 其它较优势类群在泥沙质依次为多毛类 (2%)、甲壳类幼体 (2%) 和桡足类 (1%); 沙质底则依次为甲壳类幼体 (13%)、腹毛类 (8%) 和桡足类 (6%)。泥沙质中线虫在生物量上的贡献达58%, 而在沙质中其所占生物量 (25%) 低于腹毛类 (28%)。聚类分析表明, 泥沙质和沙质沉积环境间的相似度为87%, 生物丰度组成间的相似度为71%; BIOENV分析表明, 温度、盐度、粒度及粘土粉砂含量的组合最能解释月份和站位间的差异 (r=0.614)。结合历史资料的对比研究表明, 青岛湾近海的沙质环境状况已有明显改观, 但泥沙质的污染状况仍然堪忧, 这由小型底栖生物的高丰度值、相较耐污的线虫所占的极高比例以及线虫与桡足类丰度的高比值即可看出。     

东、黄海春秋季小型底栖生物丰度和生物量研究

《北斗号》调查船分别于 2 0 0 0年 10月和 2 0 0 1年 4月在 2 6°N至 36°N,12 0°E至 12 6°30′E东、黄海陆架浅水区调查中进行了小型底栖生物的取样。研究表明 ,两个航次 (秋季、春季 )小型底栖生物的平均丰度分别为 6 5 4 .2 5± 4 4 1.72 ind/10 cm2 和342 .0 0± 2 5 2 .0 0 ind/10 cm- 2 ,平均生物量分别为 80 7.0 6± 5 17.89μg dwt/10 cm2 和 2 85 .2 5± 173.72μg dwt/10 cm2 ;平均生产量分别为 72 6 3.5 8± 4 6 6 4 .18μg dwt/(10 cm2· a)和 2 5 6 7.2 8± 15 6 3.5 0 μg dwt/(10 m2· a)。两个航次小型生物的平面分布类似 ,即高密度和高生物量区分布在水深等深浅 5 0 m左右的站位上 ,特别是在长江口以南的浙江沿海。共鉴定出 14个小型生物类群 ,按丰度自由生活海洋线虫是最优势的类群 ,秋、春季两个航次的优势度分别为 87.2 %和 91.2 %。其他优势类群依次为底栖桡足类、多毛类和动吻类 ;按生物量优势依次为多毛类 38.1%～ 5 4 .0 % ,线虫 2 8.3%～ 38.1%和桡足类 9.0 %～ 9.4 %。垂直分布的研究表明 ,91%的小型生物分布在 0～ 5 cm的表层内 ,线虫和桡足类分布在 0～ 2 cm的比例分别为 6 3%和 86 %。相关分析表明 ,小型底栖生物的数量分布与粘土含量 (% )、粉砂粘土含量 (% )和中值粒     

珠江口浮游桡足类的生态研究

根据2002～2003年珠江口12个航次的调查资料,分析了浮游桡足类种类组成、优势种演替和丰度的时空变化,探讨其影响因素。以表层盐度(S)变化将调查海域划分三个区域:I区(S<25)、Ⅱ区(2530)。结果表明:调查海域共出现桡足类65种,Ⅱ区和Ⅲ区的种类多于I区;桡足类的平均丰度为118ind·m^-3,三个区域之间的比较为Ⅱ区(165ind·m^-3)>I区(129ind·m^-3)>Ⅲ区(62ind·m^-3),春、夏季的丰度高于冬季;优势种有明显的时间和区域上的变化。I区9个航次的研究结果表明:I区桡足类种类较少;各月份之间的平均丰度差别大,由河口内往外呈增加趋势。盐度是影响珠江口桡足类种类组成和数量变化的主要因素。     

夏秋季南黄海冷水团小型底栖动物类群组成与分布

为研究黄海冷水团对小型底栖动物的影响,分别于2013年6和11月,搭载"东方红2号"科学考察船对南黄海冷水团海域8个站位的小型底栖动物的类群组成、丰度、生物量及其与环境因子的关系进行研究.结果表明:2个航次的小型底栖动物平均丰度分别为900.8和758.4 ind·10 cm-2,平均生物量分别为886.9和615.7μg·10 cm-2.方差分析表明,两个季节8个站位间小型底栖动物的丰度和生物量均无显著差异.两个航次共鉴定出17个小型底栖动物类群,其中自由生活海洋线虫为最优势的类群,在两个航次中分别占总丰度的88.5%和94.0%.其他数量上较重要的类群还有底栖桡足类、多毛类、动吻类和介形类等.两个航次中分别有92.5%和95.4%的小型底栖动物分布在0~5 cm的表层沉积物内,线虫和桡足类分布在0~2 cm的比例分别为59.1%和78.2%.对小型底栖动物丰度和生物量、线虫和桡足类丰度与其沉积环境因子的相关分析表明,小型底栖动物的丰度和生物量与底层水温度和粉砂-粘土含量呈负相关,主要类群线虫的丰度也显示出同样的结果,另一主要类群桡足类的丰度与底层水温度、粉砂-粘土含量呈负相关,与中值粒径呈正相关.小型底栖动物群落类群组成与环境因子的BIOENV相关分析表明,小型底栖动物群落受底层水温度、底层水盐度、沉积物含水量、沉积物叶绿素a和脱镁叶绿酸含量的综合影响.     

春季和秋季东海陆架区浮游纤毛虫的丰度和生物量

于2011年春季(5月)和秋季(11月)在东海陆架区进行浮游纤毛虫丰度和生物量的调查.春季和秋季纤毛虫的平均丰度分别为(614±861)和(934±809) ind·L^-1,平均生物量分别为(1.70±3.91)和(0.93±0.99) μg C·L^-1.表层纤毛虫丰度和生物量的高值区春季主要分布在近岸及远岸海区,秋季主要分布在远岸海区.春季纤毛虫的丰度和生物量在水体上层较高;秋季纤毛虫主要分布在水体上层,有时在水体底层也会出现丰度和生物量的高值.春季无壳纤毛虫群落的粒级较大,秋季较小.砂壳纤毛虫占纤毛虫丰度的平均比例春季和秋季分别为(26.9±34.3)%和(44.9±25.2)%.两个季节共鉴定出砂壳纤毛虫27属52种,春季丰度较大的种为原始筒壳虫、橄榄领细壳虫及筒状拟铃虫,秋季丰度较大的种为原始筒壳虫、小领细壳虫及矮小拟铃虫.纤毛虫丰度与温度、叶绿素a(Chl a)浓度呈显著正相关.砂壳纤毛虫丰度与盐度呈显著负相关,群落结构变化与温度显著相关.     

大兴安岭林区驯鹿夏季喜栖生境的生态特征

2012和2013年7—8月采用样线和样带调查结合的生境调查方法,对分布于我国大兴安岭西北麓的驯鹿的夏季偏好生境开展了对比研究,并对样地的海拔和乔木郁闭度等23个生境变量进行测量及比较.结果表明: 与对照样地相比,夏季驯鹿利用样地的海拔(926.9±0.8 m)、乔木郁闭度(17.9%±2.4%)、乔木胸径(35.5±2.1 cm)、乔木高度(8.2±0.5 m)、乔木密度(6.9±0.5 株·400 m^-2)及树桩数(1.3±0.2 个·400 m^-2)较大,但灌木均高(54.2±2.0 cm)较小(P<0.01).驯鹿夏季偏好选择坡度较缓的中坡生境,因其夏季喜栖生境的水源较多、隐蔽度和避风性较差,距人为干扰距离和牧民点距离均较远.主成分分析(PCA)表明,干扰强度(由距人为干扰距离及距牧民点距离变量组成)、乔木特征(由乔木的高度、密度、胸径和郁闭度变量组成)、地理特征(由坡位、坡向和土壤湿润度变量组成)、食物多度(地表植被盖度和灌木盖度变量构成)、开阔度(由隐蔽度和避风状况变量构成)和坡度是影驯鹿夏季生境选择的重要因素.这6个因子提供了70.7%的累积贡献率,主要反映了驯鹿夏季在喜栖生境选择中的食物资源、抗干扰性和反捕需求.从夏季喜栖生境的生态特征来看,驯鹿并没有被完全驯化.在保护和管理实践中,应使驯鹿种群及其核心栖息地免受高强度的人为干扰.     

Top-down control of a meiobenthic community by two juvenile freshwater fish species

Top-down control of prey assemblages by fish predation has been clearly demonstrated for zooplankton and macroinvertebrates. However, in the benthic communities of freshwater ecosystems, the impact of fish predation on meiofaunal assemblages is nearly unknown. In this study, the predation effects of juvenile carp (Cyprinus carpio) and gudgeon (Gobio gobio) on meiofaunal abundance, biomass, community structure, and the diversity of nematodes were examined using microcosms that were sampled repeatedly over 64 days. Significant differences in abundance and biomass were found between the two fish treatments (carp and gudgeon) and their respective controls for nematodes, oligochaetes, and crustaceans (copepods, harpacticoids, ostracods, and cladocerans), but not for rotifers. These changes were consistent with top-down control of the freshwater meiofaunal assemblages in the microcosms over time. By contrast, small-bodied meiofauna was more abundant, suggesting indirect facilitation. Neither the species richness nor the diversity of the nematode community was affected by fish predation. The results indicate that predation by juvenile freshwater fish depresses the overall abundance and biomass of meiofaunal assemblages, except for rotifers, and alters the size structure of the meiofaunal community. Therefore, the meiofaunal assemblages of freshwater ecosystems may be influenced by bottom-feeding juvenile fish, e.g., carp and gudgeon, through top-down control of meiofaunal populations.     

Distribution and abundance of soft-sediment meiofauna and a predatory goby in a coral reef lagoon

Spatial patterns in the abundance of the softsediment meiofauna and a predatory goby, Valenciennia longipinnis, were examined in the lagoon of One Tree Reef (Great Barrier Reef). The study provided a quantitative framework to assess the importance of physical factors on and predator prey interactions between the meiofauna and V.longipinnis. Patterns of abundance were examined at two spatial scales: among four habitats (100's of m apart) and among sites (10's of m apart) within habitats. Of the four major constituents of the meiofauna (harpacticoid copepods, nematodes, polychaetes and oligochaetes), gut analyses showed that harpacticoid copepods were the primary prey of V.longipinnis. Spatial patterns of meiofaunal abundance in the lagoon were taxon specific. Polychaetes and harpacticoid copepods exhibited significant differences among habitats. Within habitats, however, polychaetes exhibited significant differences between sites whereas copepods were uniformly distributed. Abundances of nematodes and oligochaetes did not differ between habitats. Densities of nematodes differed significantly between sites while the number of oligochaetes were similar at both spatial scales. V.longipinnis was more abundant in shallow habitats than in deep ones. This study suggests that sediment type may be an important factor influencing the distribution of both the goby and the meiofauna. V.longipinnis and two of the four meiofaunal taxa (harpacticoid copepods and polychaetes) were more abundant in the shallow habitat with fine-grained sediments. There was no significant difference between abundances of meiofaunal taxa in sites where V.longipinnis was present or absent. Overall, more fish occurred in the habitat which had the highest densities of harpacticoid copepods.     

Benthic seasonality in an intertidal mud flat at Kerguelen Islands (Austral ocean). The relationships between meiofaunal abundance and their potential microbial food

Summary Samples were taken weekly for one year at an intertidal mudflat at the Halage des Swains, Morbihan Sound, Kerguelen Islands, for meiofauna, their suspected microbial food (bacteria and diatoms) and associated chemical and physical factors. Organic carbon and nitrogen content, bacterial abundance and biomass, pigment content and daily primary production, were significantly correlated (Spearman rank) to the temperature. Meiofauna exhibited very high abundances (up to 14 000 ind./10 cm^–2) without seasonal trend but with distinct short term oscillations of population densities. No direct correlation occurred between meiofauna (85.9% nematodes and 10.8% copepods) and temperature. Total meiofauna abundance was positively correlated to bacterial biomass in the oxidized layer, to organic content below redox potential discontinuity layer, and negatively correlated to the hourly primary production. The data suggest that nematodes are correlated to bacterial biomass and organic content in the sediment. Effect of ambient temperature on development time of nematofauna could be described by a Belehradek function. Even though some correlations existed, this study shows that peaks of meiofaunal abundance are not correlated to potential food abundance variability. Thus, the limitation of meiofauna community and its annual pattern is reasonably governed by the development time and reproductive strategy of the few co-dominant species of the main taxa.     

黑竹冲河小裳蜉(Leptophlebia sp.)和蜉蝣(Ephemera sp.)周年生产量

大型底栖动物在河流生态系统中发挥着重要作用。2003年6月至2004年6月间对汉江流域2级河流--黑竹冲河大型底栖动物群落优势种类的生产力进行了为期一周年的调查研究。结果表明,主要优势种小裳蜉(Leptophlebia sp.)和蜉蝣(Ephemera sp.)的生活史均为一年两代,蜉蝣的两个代之间界限比较明显;小裳蜉成虫羽化主要发生在秋季和冬季,而蜉蝣成虫羽化主要发生在夏季和冬季。小裳蜉和蜉蝣种群的生物量和多度均出现两次峰值。采用体长频率法(size-frequencymethod)测算的周年生产量分别为:小裳蜉,38.0362g·m^-2·a^-1,P/B为11.4;蜉蝣,76.0318g·m^-2·a^-1,P/B为11.8。     

Composition,distribution and biomass of meiobenthos in the Oosterschelde estuary (SW Netherlands)

Meiofauna composition, abundance, biomass, distribution and diversity were investigated for 31 stations in summer. The sampling covered the whole Oosterschelde and comparisons between the subtidal — intertidal and between the western-central — eastern compartment were made.Meiofauna had a community density ranging between 200 and 17 500 ind 10 cm^–2, corresponding to a dry weight of 0.2 and 8.4 gm^–2. Abundance ranged between 130 and 17 200 ind 10 cm^–2 for nematodes and between 10 and 1600 ind 10 cm^–2 for copepods. Dry weight biomass of these taxa was between 0.5–7.0 gm^–2 and 0.008–0.3 gm^–2 for nematodes and copepods respectively.The meiofauna was strongly dominated by the nematodes (36–99%), who's abundance, biomass and diversity were significantly higher intertidally than subtidally and significantly higher in the eastern part than in the western part. High numbers were positively correlated with the percentage silt and negatively with the median grain size of the sand fraction. The abundance and diversity of the copepods were highest in the subtidal, but their biomass showed an inverse trend being highest on the tidal flats.The taxa diversity of the meiofauna community and species diversity of both the nematodes and the copepods were higher in subtidal stations than on tidal flats. In the subtidal, the meiofauna and copepod diversity decreased from west to east, whereas nematode diversity increased.The vertical profile clearly reflected the sediment characteristics and could be explained by local hydrodynamic conditions.Seasonal variation was pronounced for the different taxa with peak abundance in spring, summer or autumn and minimum abundance in winter.Changes in tidal amplitude and current velocity enhanced by the storm-surge barrier will alter the meiofauna community structure. As a result meiofauna will become more important in terms of density and biomass, mainly due to increasing numbers of nematodes, increasing bioturbation, nutrient mineralisation and sustaining bacterial growth. A general decrease in meiofauna diversity is predicted. The number of copepods is expected to decrease and interstitial species will be replaced by epibenthic species, the latter being more important in terms of biomass and as food for the epibenthic macrofauna and fishes.     

Long-term nutrient enrichment elicits a weak density response by saltmarsh meiofauna

The effect of chronic nutrient enrichment on benthic meiofauna was examined in a whole-ecosystem experiment conducted in salt marshes in the Plum Island watershed of northeastern Massachusetts, USA. We compared abundances of total meiofauna, nematodes, copepods, ostracods, and annelids including Manayunkia aestuarina, in fertilized (where N and P was increased 15× in incoming tidal water throughout each growing season for 6 years) and reference marsh creeks to test for bottom-up responses. Although some responses to nutrient enrichment were evident, results did not match our expectations of strong increases in abundance. Variation in abundance between nutrient-enriched and reference creeks was detected in all three subhabitats but responses were inconsistent and variable over time, suggesting that natural variability was greater than variation induced by fertilization. Our results showed an overall weak negative correlation between meiofauna abundance and benthic microalgae (BMA) biomass partly because the BMA response to nutrient enrichment was relatively small and perhaps limited by grazing macrofauna and nekton. Our results suggest a better mechanistic understanding of the relationship between BMA and meiofaunal abundance is needed to fully understand how nutrient enrichment affects meiofauna.