南极威德尔海陆缘固冰区叶绿素a及硅藻的分布

本文描述了1985年1月-2月联邦德国“极星”号极地考察船沿威德尔海陆缘固冰区调查期间所获得的冰柱状样内叶绿素a以及硅藻的分布,对三个不同区域柱状样的分析结果表明,底部10-30cm的海冰多呈褐色,其内由大量藻类,特别是由硅藻细胞的富集而形成,丰度变化大.在融化的底部冰样中,细胞数高达10⁸个/l,叶绿素a浓度高达2220mg/m³,中部常见到大量小型的失去色素乃至死亡的硅藻细胞.初步鉴定出26种硅藻,其多数隶属于茧形藻属(Amphiprora),斜纹,藻属(Pleurosigma),菱形藻属(Nitzschia),盒形藻属(Biddulphia),角刺藻属(Corethron),海毛藻属(Thalassiothrix),海链藻属(Thalassiosira),以及脆杆藻属(Fragilaria)等,本文还记录了两种不同的底部生态群落:寡种和多种集群的生态类型,并对硅藻的富集和分布成因作了一些讨论.     

不同湍流模式下钱塘江涌潮水流三维模拟

钱塘江涌潮具有动力作用强和流速变化快等特点。涌潮水流紊动复杂,流速的垂向分布和紊动强度息息相关。通过涌潮水流实测资料的分析可以发现,涌潮作用下流速垂向分布在底部和上层存在差异。为研究涌潮作用下流速垂向分布的特征,应用基于非结构网格下有限体积法模型FVCOM对钱塘江涌潮河段水流运动进行三维数值模拟。考虑到涌潮紊动作用复杂且对流速的垂向分布起着重要影响,采用不同的湍流模式对涌潮传播过程中水流的运动特征开展研究。通过与涌潮河段实测资料的验证,复演涌潮到达前后水流运动特征,给出涌潮水流湍动能的变化过程。研究成果有助于深入认识涌潮水流紊动特征和流速的分布规律,为涌潮作用下物质输运的研究提供基础。     

一株底栖硅藻——双眉藻的优化培养

双眉藻(Amphora sp.)是糙刺参(Stichopus horrens)喜食的优良饵料。本文采用光密度法分别测定了该藻在光照强度28～149 μmol/(m²·s)、温度20～35℃、盐度25~45 和氮质量浓度0～7 500 mg/L、磷质量浓度0～440 mg/L、硅质量浓度0～1 500 mg/L 以及氮磷硅多因子组合情况下的比生长速率, 探讨了光照、温度、盐度和不同质量浓度的氮、磷、硅单因子及多因子组合对该藻生长的影响, 以及该藻的最适生长条件。单因子试验结果表明, 该藻在光照范围为35～149 μmol/(m²·s)时都能良好生长, 最适光照为56～99 μmol/(m²·s), 低温时该藻生长缓慢, 最适生长温度为25～30℃。Amphora sp.为广盐性, 在盐度25～45 都能较好生长, 最适盐度为30～35。氮、磷、硅的最适质量浓度分别是750～7 500 mg/L、44 mg/L和150mg/L, 磷对该藻生长的影响比氮更显著。正交实验结果表明, 氮、磷、硅的最佳质量浓度分别为75 mg/L、44 mg/L 和150 mg/L, 最佳配比为2.4:1:3.4, 与其他底栖硅藻的相应指标存在一定的差异, 可能是物种和地域环境差异引起的, 反映出该藻适应高温、强光特殊栖息环境的特征。     

印尼贯穿流的诊断计算

利用全球大洋二维的自由表面诊断模型并采用气候态Levitus(2001)温盐资料及COADS风应力资料估算印尼贯穿流及其季节变化。结果表明,南海的Karimata海峡出流量对印尼贯穿流有显著的贡献,印尼贯穿流的平均流量为16.6Sv,流量在6月最大(18.5Sv),4月最小(12.7Sv)。与其它模式结果和观测结果一致的是,Makas-sar海峡流量在7月最大(13.8Sv),1月最小(0.2Sv),其年平均流量为6.7Sv;Karimata海峡是南海南部最大的出水口,年平均流量为2.6Sv,爪哇海水在5—9月之间流入南海,其它月份南海南部水流入爪哇海;Timor海峡是印尼贯穿流最大的出口;Lombok流量的季节变化表现为半年周期。通过模拟计算结果,结合动力计算,获取了Makassar海峡经向速度的垂向结构,结果显示Makassar海峡的经向速度有明显的垂向切变,100m层次的南向速度为30—35cm.s-1。     

米氏凯伦藻和东海原甲藻生长的光照强度生态幅研究

藻类生长的光照生态辐是指在一定光照强度范围内藻类能生长和繁殖的水平范围,由藻类生长的最适光照强度、光照强度适宜生长范围和光照强度耐受限度构成。为了定量获取藻类生长的光照生态幅,在室内培养条件下,分别研究了三个温度（18、22、25℃）条件下六个不同光照强度[28.32、55.15、75.06、96.59、111.66和135.75μmol/（m²·s）]对米氏凯伦藻和东海原甲藻细胞数和最大比生长率的影响,依据Shelford耐受性定律建立了米氏凯伦藻和东海原甲藻的光照耐受性模型,并得到了藻类生长的最适光强、光强适宜生长范围和光强耐受限度的定量表达。结果表明：无论是米氏凯伦藻还是东海原甲藻,在同一温度条件下,在实验设定的光照强度水平范围内,均分别存在一个适宜藻类生长的最适光强I_opt,且当光强I ≤ I_opt时,藻类细胞密度和比生长率均随着光强的升高而显著增大;而当I ≥ I_opt时,藻类细胞密度和比生长率随着光强的升高而显著减小。此外,随着培养温度的升高,藻类细胞密度和比生长率均呈现"先升后降"的变化趋势。建立的藻类生长光照耐受性模型与Shelford耐受定律较为吻合,并定量得到了米氏凯伦藻在18、22、25℃下的最适生长光强分别为81.48、80.15、79.27μmol/（m²·s）;光强适宜生长范围分别为33.11-162.96、32.57-160.3、32.03-158.54μmol/（m²·s）;东海原甲藻在18、22、25℃下的最适生长光强分别为79.39、78.19、76.69μmol/（m²·s）;光强适宜生长范围分别为31.89-158.78、31.77-156.38、31.18-153.38μmol/（m²·s）。     

神经毒素BMAA对球等鞭金藻(Isochrysis galbana)的生长抑制作用研究

神经毒素β-N-甲氨基-L-丙氨酸(β-N-methylamino-L-alanine,BMAA)主要来自淡水或海洋环境中的蓝藻和硅藻,在海洋生态系统中具有明显的生物放大作用,被认为是诱发阿尔茨海默症(Alzheimer''s Disease,AD)等多种神经退行性疾病的重要环境因子。近年,BMAA及其同分异构体2,4-二氨基丁酸(2,4-diaminobutyric acid,DAB)在我国及其他多个沿海国家和地区的贝类水产品中被普遍检出,潜在威胁消费者健康和海洋生态安全。但目前有关BMAA对海洋微藻的化学生态学作用尚不清楚。为此,通过向球等鞭金藻(Isochrysis galbana)培养基中分别添加不同浓度的BMAA及20种蛋白氨基酸,探究了BMAA单独及其与氨基酸联合作用96 h对球等鞭金藻比生长率和氨基酸含量的影响,并分析了微藻吸收外源BMAA的含量。结果表明,球等鞭金藻能吸收培养体系中的外源BMAA,吸收量与BMAA的添加浓度呈正相关,且进入细胞内的BMAA多半以溶解结合态形式存在;BMAA抑制批次培养的球等鞭金藻比生长率的96 h半效应浓度(96 h-EC₅₀)约为2 μmol/L;与对照组相比,暴露于BMAA 96 h后球等鞭金藻细胞内酪氨酸、丙氨酸、丝氨酸等15种氨基酸的合成量明显降低;除脯氨酸、苏氨酸、甘氨酸外,其他17种氨基酸与BMAA联合暴露实验均增强了BMAA对球等鞭金藻比生长率的抑制效应,这可能与培养体系中的氨基酸促进了微藻吸收外源BMAA的能力有关。因此,海洋生态系统中BMAA毒素的化学生态学作用应引起人们的关注。有关BMAA抑制球等鞭金藻有丝分裂的分子机制有待进一步研究。     

Savonius型转轮三角阵列减流性能研究

为了助力海洋牧场减流防护工程, 研究Savonius型转轮阵列减流性能。作者建立Savonius型转轮三角阵列尾流场数值模型, 并通过水池实验验证准确性, 基于可靠数值模型探究转轮阵列尾涡减流机理, 研究三角阵列结构参数L_X、L_Y, 以及动力参数TSR、初始流速、旋向对整体减流性能的影响规律。结果表明,下游转轮产生的涡流呈现非对称分布, 并且产生更多涡流的转轮拥有更好的减流效果。另外, L_X为3D和L_Y为2D时减流性能最佳。最后对比发现, 在叶尖速比为0.9~1.1减流效果更好; 初始流速大小不影响减流效果; 下游转子对称分布时, 随着上游转子改变旋转方向, 减流效果出现明显差异。     

源区黑潮季节变异及其动力机制的数值研究

应用POM2K模式对中国海黑潮区气候态平均环流进行了数值模拟。采用正交曲线网格, 模式区域为太平洋海盆, 特别的在中国海区域进行加密并较好的拟合了岸线; 垂向分为21层, 并在海表9层以上采用对数网格分布; 采用COADS气候态月平均的风应力, 并将模式的温度结果和MODIS月平均的SST数据进行同化, 然后将模式模拟出的流量、海表高度异常同实测数据和卫星观测数据进行了对比验证, 结果均显示模拟结果可信度较高。接着本文探讨了北赤道流分岔位置季节性的变化对源区黑潮流量的影响, 结果表明, 秋冬季节北赤道流分岔位置较靠北, 源区黑潮流量较大, 而春夏季节北赤道流分岔位置较靠南, 黑潮流量较小。在此基础上, 针对源区黑潮的动力机制进行了数值实验。实验中主要考虑了以下动力因子对源区黑潮季节性变化的影响: (1)风应力; (2)非线性; (3)黑潮的斜压敏感性, 然后通过与控制实验的对比, 讨论了不同的动力因素对吕宋海峡净流量和吕宋海峡上层环流场的影响。     

春季长江口北支邻近海域浮游植物群落及其影响因子

为了解长江口北支邻近海域浮游植物群落结构特征,于2014年5月对该海域进行采样调查,分析了调查区域内的浮游植物群落组成及环境影响因素,并对比了水采和网采两种采样方法所得样品的差异性。结果表明:水采浮游植物种类数(178种)和细胞平均丰度(270.32×103cells/L)均高于网采浮游植物种类数(154种)和细胞平均丰度(6.44×10~3cells/L)。骨条藻Skeletonema spp.、具槽帕拉藻Paralia sulcata和双角缝舟藻Rhaphoneis amphiceros为两种方法的共同优势种。水采样品优势种还包括线形海链藻Thalassiosira lineate、角海链藻Thalassiosira angulate、全沟藻Teleaulax spp.、锥状斯克里普藻Scrippsiella trochoidea、旋链海链藻Thalassiosira curviseriata,而网采样品优势种还有琼氏圆筛藻Coscinodiscus jonesianus。聚类分析结果显示水采浮游植物群落比网采浮游植物群落更聚集,相似性百分比分析进一步揭示两种采样方法群落格局间非相似性高达68.2%,造成两种采样方法差异的主要判别种为旋链海链藻、角海链藻和盾卵形藻Cocconeis scutellum。冗余分析表明,影响浮游植物群落分布的主要环境因子为悬浮物浓度、温度、透明度和盐度。     

渤海夏季环流和渤海海峡水体输运的数值诊断研究

建立了一个基于POM的涵盖渤、黄、东海的海洋环流诊断模式来研究渤海夏季环流。分别进行了风海流、密度流和总环流的模拟。从模拟结果得出:渤海海峡夏季与北黄海的水交换总的来说表现为北进南出特征,但与冬季相比,其流量较小(约5×103m3s 1)且不能深入渤海。辽东湾基本上受气旋式环流控制,黄河口外至渤海湾受反气旋式环流控制。数值实验表明,渤海夏季主要属密度流性质。在渤海海峡的北岸存在一支明显的上升流,而且北部的海水垂向运动比南部要强许多。在渤海中部的纬向断面上,东部的海水垂直交换要比西部活跃得多;渤海海水的垂向运动亦主要是密度流导致的。     

Distribution of phytoplankton in the East China Sea in the winter of 1993

Phytoplankton distribution and its relationship to water masses were investigated in the East China Sea from February 15 to March 10, 1993. Diatoms, dinoflagellates and coccolithophorids were examined by the Utermöhl method. Two distinct phytoplankton assemblages were identified: a shelf and oceanic assemblage. The shelf community was characterized by a high abundance of diatoms, particularly, a benthic diatomParalia sulcata, and the oceanic community by numerical dominance of coccolithophorids and occurrence of surface warm-water species of diatoms. A boundary of both communities was located at the shelf edge that coincided with the shelf side of a Kuroshio front.P. sulcata was the most dominant in the inner shelf area throughout the water column. The occurrence of this species near the surface was considered to be a good indicator of the enhanced vertical mixing driven by winter monsoon. The species survives under extremely low light intensity near the bottom during the stratified periods in summer. During the winter time when light condition at the bottom becomes most unfavorable, resuspension and upward traveling of the species due to enhanced vertical mixing seem to be advantageous to acquire suitable light condition. Because of its predominance, possible importance ofP. sulcata is suggested in material cycling on the shelf, particularly near the bottom.     

光照强度对孔石莼生长和藻体化学组成的影响

研究了光照强度2 500～20 000 lx对孔石莼(Ulva pertusa)生长和藻体生化组成的影响。研究结果表明,光照强度对孔石莼的生长率具有明显的影响(P0.05),孔石莼在光照强度为12 500 lx时有最大的生物量积累。光照强度低于12 500 lx时,孔石莼的生长率有随着光照强度的降低而减小的趋势;光照强度高于12 500 lx时,孔石莼的生长率随着光照强度的升高而降低(P0.05)。不同光照强度对孔石莼的叶绿素、可溶性糖和游离脯氨酸的含量具有明显的影响(P0.05)。随着光照强度的增加,孔石莼的叶绿素a和叶绿素b的含量逐渐变小;低光照条件也促进了孔石莼蛋白质的积累;当光照强度超过17 500 lx时,游离脯氨酸的含量明显增加。光照强度对孔石莼化学组成也具有明显的影响(P0.05)。随着光照强度的升高,藻体的N元素含量有所升高,但光强达到17 500 lx后,随着光强的增加,N元素含量反而降低;C元素的含量在光照强度达到17 500 lx后,含量也明显升高;H元素的含量在光照强度2 500~20 000 lx范围内,具有随着光照强度增加而增加的趋势。     

Observation and measurement of the bottom boundary layer flow in the prebreaking zone of shoaling waves

In this paper, the characteristics of the bottom boundary layer flow induced by nonlinear, asymmetric shoaling waves, propagating over a smooth bed of 1/15 uniform slope, is experimentally investigated. Flow visualization technique with thin-layered fluorescent dye was first used to observe the variation of the flow structure, and a laser Doppler velocimeter was then employed to measure the horizontal velocity, U.The bottom boundary layer flow is found to be laminar except within a small region near the breaking point. The vertical distribution of the phase-averaged velocity U at each phase is non-uniform, which is directly affected by the mean velocity, . The magnitude of increases from zero at the bottom to a local positive maximum at about z/δ2.02.5 (where z is the height above the sloping bottom and δ is the Stokes layer thickness), then decreases gradually to zero at z/δ6.07.0 approximately, and finally becomes negative as z/δ increases further. Moreover, as waves propagate towards shallower water, the rate of increase in the maximum onshore oscillating velocity component is greater than that of the offshore counterpart except near the breaking point. The free stream velocities in the profiles of the maximum onshore and offshore oscillating velocity components, and are found to appear at z/δ≥6.0. This implies that, if the Stokes layer thickness is used as a length scale, the non-dimensionalized boundary layer thickness remains constant in the pre-breaking zone. Although is greater than and the asymmetry of the maximum free stream velocities (i.e. ) increases with decrease of water depth, a universal similar profile can be established by plotting z/δ versus ( ) or ( ). The final non-dimensional profile is symmetric and unique for the distributions of the maximum onshore and offshore oscillating velocity components within the bottom boundary layer, which are induced by nonlinear, asymmetric shoaling waves crossing the pre-breaking zone.     

The effect of standing biomass on flow velocity and turbulence in Spartina alterniflora canopies

Plant-flow interactions on the surface of tidal wetlands result in flow characteristics that are profoundly different from non-vegetated flows. Reductions in mean flow velocity and turbulence, especially the vertical components, limit vertical mixing and may impact a wide range of processes including geochemical exchanges at the sediment water interface, larval recruitment and dispersion, and sediment deposition and retention. The goal of this paper is to quantify horizontal and vertical components of velocity, turbulence intensity and total turbulent kinetic energy in Spartina alterniflora canopies in southeastern North Carolina and to relate flow characteristics to particulate transport on the marsh surface. Another aim of this paper is to assess the extent to which the distribution of standing biomass affects mean flow and turbulence by comparing S. alterniflora data to other canopy types and through a series of canopy manipulations which altered canopy height and stem densities.The results of this study indicate that flow velocity, turbulence intensity, and total turbulent kinetic energy (TKE) are significantly reduced within the vegetated canopy and that this reduction is inversely related to the amount of biomass present in the water column. Within the canopy, approximately 50% of the initial mean velocity and TKE is reduced within 5 m of the canopy edge. Within the canopy, mean velocity and TKE_horiz usually exceeded vertical velocity or TKE_vert and the vertical components of flow were attenuated more strongly than the horizontal. These results suggest that within the vegetation, turbulence contributes more to lateral advection than to vertical mixing. As a result, total suspended solid concentrations were shown to decrease logarithmically with distance from the canopy edge and to decrease at a faster rate in more densely vegetated regions of the canopy (i.e. lower TKE_vert) as compared to areas of sparser vegetation (i.e. higher TKE_vert).     

光强和营养盐对伪矮海链藻昼夜节律变化的影响

于1989年1月 - 1989年8月采用连续培养和半连续培养方法进行了伪矮海链藻细胞分裂、叶绿素a含量和活体荧光特性与光、营养盐关系的研究。结果表明,细胞分裂、活体荧光、叶绿素a均呈现光照期的增长速率明显高于黑暗期的增长速率的日变化规律,荧光增强比则在光照期开始后或黑暗期结束时出现最高值;光强和营养盐不仅影响各指标日变化的幅度,而且还可改变荧光增强比峰值出现时间。因此,在研究细胞分裂、叶绿素a和荧光特性的昼夜节律时,必须考虑光和营养盐这两个重要因素。     

The distribution of chlorophyll a and its influencing factors in different regions of the Bering Sea

The distribution of chlorophyll a(Chl a) and its relationships with physical and chemical parameters in different regions of the Bering Sea were discussed in July 2010. The results showed the seawater column Chl a concentrations were 13.41–553.89 mg/m2 and the average value was 118.15 mg/m2 in the study areas. The horizontal distribution of Chl a varied remarkably from basin to shelf in the Bering Sea. The regional order of Chl a concentrations from low to high was basin, slope, outer shelf, inner shelf, and middle shelf. The vertical distribution of Chl a was grouped mainly from single-peak type in basin, slope, outer shelf, and middle shelf, where the deep Chl a maxima(DCM) layer was observed at 25–50 m, 30–35 m, 36–44 m, and 37–47 m, respectively. The vertical distribution of Chl a mainly had three basic patterns: standard single-peak type, surface maximum type, and bottom maximum type in the inner shelf. The analysis also showed that the transportation of ocean currents may control the distribution of Chl a, and the effects were not simple in the basin of the Bering Sea. There was a positive correlation between Chl a and temperature, but no significant correlation between Chl a and nutrients. The Bering Sea slope was an area deeply influenced by slope current. Silicate was the factor that controlled the distribution of Chl a within parts of the water in the slope. Light intensity was an important environmental factor in controlling seawater column Chl a in the shelf, where Chl a was limited by nitrate rather than phosphate within the upper water. Meanwhile, there was a positive relationship between Chl a and salinity. Algal blooms broke out at Sta. B6 of the southwestern St. Lawrence Island and Stas F6 and F11 in the middle of the Bering Strait.     

珠江八大口门2016年枯季盐度同步观测及咸淡水混合研究

通过分析2016年枯季在珠江三角洲8个口门测站的现场同步观测盐度资料,总结了枯季八大口门同步盐度垂向分布和盐淡水混合特征.结果表明:由于八大口门的水动力条件、河口走向等不同,各口门的盐水入侵强度、盐淡水混合程度存在时空差异.其中,在盐度分布上表现为以横门为中心,向东西两侧口门,盐度逐渐递增;在层化参数分布上,总体上由横...     

围填海对伶仃洋水流动力的短期影响模拟研究

利用已经过验证的高分辨率三维海洋动力模型FVCOM,根据1984—2014年内伶仃洋的围填海变化情况,结合情景模拟案例,研究分析围填海对伶仃洋水流动力的影响,探究截流式和顺流式围填海对伶仃洋不同季节的水平余流场、垂向环流结构以及潮汐变化过程的影响。研究结果表明,围填海对伶仃洋的余流流向没有明显影响,但对余流速有较大的影响。在水平方向上,截流式围填海使得周边海域的余流速明显增大,增幅在0.02～0.25 m/s不等,其中口门区域受到的影响最大;相较于底层流场,表层流场受围填海的影响相对更大,围填海以南的较远海域在表层出现一条强度逐渐减弱的流速减小带,减幅在0.02～0.15 m/s不等,且影响范围与流场的分布密切相关,在夏季向南延伸,在冬季向西南延伸。顺流式围填海的影响则主要分布在伶仃洋两侧沿岸,并且不同季节的影响特点有一定区别,在夏季使得内伶仃洋东岸海域流速增大,但在冬季使其流速减小,变化幅度均在0.02 m/s以上。在垂直方向上,围填海使口门区域余流的纵向流速梯度增加,并且改变了伶仃洋余流的垂向分布情况,总体表现为远离围填海的海域表、底层余流的流速减小,中上层余流的流速增大;与此同时,围填海大幅度改变了周边海域的横向流速,并且在伶仃水道、矾石水道等区域产生了新的横向环流。围填海使得河口至围填海的余水位明显上升,使得伶仃洋海域的余水位下降,余水位梯度的增大是围填海周边余流速增大的主要原因。另外,围填海影响了伶仃洋的潮汐变化过程。在大潮期间,围填海改变了伶仃洋海域涨落潮时的潮流流速,使得周边海域落急流速增加,较远海域落急流速减小,而涨急流速都减小;同时,围填海使得海域涨落潮时的潮位受到一定影响。围填海最终使得伶仃洋的潮汐相位提前了20～35 min。     

Laboratory observation of boundary layer flow under spilling breakers in surf zone using particle image velocimetry

A boundary layer flow under spilling breakers in a laboratory surf zone with a smooth bottom is investigated using a high resolution particle image velocimetry (PIV) technique. By cross-correlating the images, oscillatory velocity profiles within a viscous boundary layer of O(1) mm in thickness are resolved over ten points. Using PIV measurements taken for an earlier study and the present study, flow properties in the wave bottom boundary layer (WBBL) over the laboratory surf zone are obtained, including the mean velocities, turbulence intensity, Reynolds stresses, and intermittency of coherent events. The data are then used to estimate the boundary layer thickness, phase variation, and bottom shear stress. It is found that while the time averaged mass transport inside the WBBL is onshore in the outer surf zone, it changes to offshore in the inner surf zone. The zero Eulerian mass transport occurs at h/h_b ≈ 0.92 in the outer surf zone. The maximum overshoot of the streamwise velocity and boundary layer thickness are not constant across the surf zone. The bottom shear stress is mainly contributed by the viscous stress through mean velocity gradient while the Reynolds stress is small and negligible. The turbulence level is higher in the inner surf zone than that in the outer surf zone, although only a slight increase of turbulent intensity is observed inside the WBBL from the outer surf zone to the inner surf zone. The variation of phase inside and outside the WBBL was examined through the spatial velocity distribution. It is found the phase lead is not constant and its value is significantly smaller than previous thought. By analyzing instantaneous velocity and vorticity fields, a remarkable number of intermittent turbulent eddies are observed to penetrate into the WBBL in the inner surf zone. The size of the observed large eddies is about 0.11 to 0.16 times the local water depth. Its energy spectra follow the − 5/3 slope in the inertial subrange and decay exponentially in the dissipation subrange.     

Vertical structure of larval fish assemblages during diel cycles in summer and winter in the southern part of Bahía de La Paz, México

The effect of environmental variables on the vertical structure of larval fish assemblages in a tropical coastal lagoon was analyzed. Ichthyoplankton samples were collected from the near-bottom and surface strata near the mouth of a subtropical lagoon during contrasting seasonal conditions of temperature, photoperiod, light intensity, and tidal heights. During summer, larval fish assemblages had high species richness (R) and were dominated by tropical species. During winter, assemblages had lower R values and were dominated by subtropical and temperate species. Vertical distribution patterns of the taxa were determined by the interaction of environmental variables and behavior of each species to maintain their position in a stratum in the water column, or to achieve vertical migrations induced by environmental stimuli that, in this case, were thermal gradient, column water stratification, and intensity of light. Depth position and vertical migration of fish larvae, coupled with the flood and ebb tide conditions, played an important role in their retention and displacement toward the lagoon. Fish larvae with distribution restricted to the inner part of the inlet, such as Achirus mazatlanus, Etropus sp., and several gobies, were more abundant in the near-bottom stratum during the ebb tide, allowing them to avoid exportation, whereas those that could spawn outside, but depended on the inlet as a nursery area, were more abundant near the surface during flood tide, such as Abudefduf troschelii and Stegastes rectifraenum.