底质类型对热带海草海菖蒲种子萌发和幼苗生长的影响

近几十年来,受到人类活动和气候变化的影响,全球海草床呈现退化趋势,海草床的恢复备受关注.其中,海草种子或幼苗移植由于其对供体海草床破坏和影响较小,并能保证海草的遗传多样性而备受重视.移植区的底质类型是决定海草种子或幼苗移植存活率的重要因子,然而,目前关于热带海草种子萌发和幼苗生长对不同底质类型响应的研究很有限.本研究以...     

大叶藻种子育苗及移栽技术研究

大叶藻(Zostera marina L.)是全球分布最广泛的海草之一,曾在山东半岛沿海有广泛分布。然而,自1980年代开始,受自然因素和人类活动的影响,大叶藻场严重衰退,导致黄海近岸海洋生态系统恶化,渔业资源锐减。本研究以中国黄海海域(山东半岛)大叶藻为研究对象,研究不同温度、春化作用时间对大叶藻种子萌发和不同播种深度对种子成苗率的影响,进行了幼苗培育,研制开发幼苗移栽装置和技术。结果表明:春化处理温度对大叶藻种子萌发率具有显著影响(p0.01),4℃春化处理50d的大叶藻种子萌发率最高,平均达55.3%;埋植深度对大叶藻种子萌发率和幼苗成苗率有影响,埋植深度0.5~2.5cm时大叶藻幼苗的出苗率相似,但显著高于埋植深度3~4.5cm的成苗率(p0.01)。依据这些研究结果,成功培育大叶藻苗7.6万株,生长110d,平均幼苗长度达16.3cm,最大长度达22cm;研制了育苗杯大叶藻苗移栽装置,实现了从水面高效栽植大叶藻幼苗。     

海南岛新村湾营养负荷对海菖蒲的影响研究

对海南岛新村湾海草床的优势种——海菖蒲(Enhalus acoroides)的茎枝特征、茎枝密度、生物量和不同组织营养素含量进行了研究,并探讨了海水和沉积物间隙水营养负荷对其的影响。结果表明,(1)海菖蒲的茎枝特征(叶长、宽和枝重)、茎枝密度和地上生物量存在显著的空间差异,这些因子与海水和沉积物间隙水DIN含量呈负相关;(2)海菖蒲TN、TP质量分数随着样区的变化而产生显著差异,海菖蒲TN质量分数与其所在样区海水和沉积物间隙水DIN浓度呈显著正相关;(3)随着水体N负荷的增加,海菖蒲叶单位面积附着藻类生物量显著增加。本次研究的结果表明,网箱养殖引起的营养负荷是导致海草衰亡的潜在原因之一,引起了新村湾网箱养殖区海草床的退化。     

网箱养殖对海南新村澙湖海菖蒲生物学与生态学特征的影响

以海南新村澙湖海草床优势种之一的海菖蒲（Enhalus acoroides）为研究对象,于2005年4月至2006年1月间,分4个季节对海菖蒲的茎枝生物量、叶长、叶宽、叶单位面积附着藻类生物量、茎枝密度及生物量等进行了研究,初步探讨了网箱养殖对海菖蒲生物学和生态学特征的影响.其结果表明：（1）在春、夏、秋3个季节里,海菖蒲叶长、叶宽和茎枝生物量等均显示了与其所在样区海水和沉积物间隙水D IN含量呈负相关关系.（2）随着水体N负荷的增加,海菖蒲叶单位面积附着藻类生物量剧增.（3）网箱养殖区海菖蒲较小的地上生物量、茎枝密度及地上生物量与地下生物量比,均表明网箱养殖区海菖蒲受人为干扰的影响明显大于其他2个样区.     

海草土壤种子库：特征、影响因素、研究方法及其在受损海草场恢复中的作用

海草的土壤种子库具有巨大的时空异质性,不同种类密度差别可达5个数量级,同一种植被的土壤种子库,在不同环境、不同阶段亦相差甚大。种子具有休眠现象的海草可形成持久种子库(种子寿命≥1 a),例如喜盐草属(Halophila)、针叶草属(Syringodium)、川蔓草属(Ruppia)和丝粉草属(Cymodocea),或短暂种子库(种子寿命<1 a),例如鳗草属(Zostera)和虾形草属(Phyllospadix)。种子没有休眠现象,例如海菖蒲属(Enhalus)和泰来草属(Thalassia),或具有胎生现象的海草,例如全楔草属(Thalassodendron)和根枝草属(Amphibolis),则不形成土壤种子库。植被特性、环境条件、动物行为等影响海草的土壤种子库。海草土壤种子库密度的研究方法可分为直接计数法和幼苗萌发法两种,采用何种方法取决于种子的大小以及破除休眠的可控性。土壤种子库尤其是持久种子库是一年生海草场或受到较大干扰海草场恢复的关键。我国绝大部分的海草场面临巨大的人为威胁,且不少海草场由一年生海草组成,因此,保护好这些海草场的土壤种子库至关重要。     

红纤维虾形草(Phyllospadix iwatensis)种子形态及内部特征

海草床可以为海洋动物提供产卵、索饵、繁育等场所。目前, 海草床面积急剧下降, 其中我国关于虾形草属(Phyllospadix)海草的研究相对较少, 对于虾形草主要繁育载体种子的描述、显微观察和萌发过程方面存在较多空白。本研究以红纤维虾形草(Phyllospadix iwatensis)为研究对象, 对其生长环境、种子外部特征、内部结构、萌发过程等进行了定性定量描述。结果表明, 虾形草果实种子对于海洋环境有着外部形态与内部结构的适应性, 外部形态特点包括独特的果序和果实形状, 以及翅状结构和内侧鬃毛, 其中果序呈弯虾形, 平均长度3.4cm, 果实呈马掌形, 直径3~4mm, 内部结构特征包括胚乳占比大、果皮种皮解剖结构复杂等, 具有作为海岸带植被修复工具种的优势。本研究补充了目前对虾形草等海洋沉水植物种子的研究资料, 为虾形草海草种质库保护与海草床修复提供了建议和参考。     

海南黎安港海草床分布特征、健康状况及影响因素分析

通过对黎安港海草资源进行调查,并采用《近岸海洋生态健康评价指南》（HY∕T087-2005）对海草床生态系统健康进行评价。结果表明,黎安港海草种类主要有2科3亚科4属4种,分别为圆叶丝粉草、泰来草、海菖蒲及卵叶喜盐草;海菖蒲分布广泛,其次为圆叶丝粉草及泰来草,海草床分布面积约为0.93 km²,黎安南岸海草分布面积最大,西岸次之,东岸最小。海草平均覆盖度为37.80%。圆叶丝粉草平均密度872.00株/m²,平均生物量150.34 g/m²,泰来草平均密度405.00株/m²,平均生物量62.45 g/m²;海菖蒲平均密度251.00株/m²,平均生物量778.50 g/m²,卵叶喜盐草平均密度6 768.00株/m²,平均生物量70.63 g/m²,2015年黎安港海草床处于健康状态;2018年处于健康状态边缘;2016年、2017年及2019年均处于亚健康状态,主要体现在沉积物环境、栖息地健康以及生物指标存在亚健康,2015年至2019年期间,黎安港海草床的健康状况总体呈现为健康转为亚健康的趋势,主要影响因素有水体交换能力较差、水产养殖活动影响、沿岸围填海工程及其他人为活动影响等。     

中国海草资源分布现状、退化原因与保护对策

海草床是三大典型的近海海洋生态系统之一,具有极高的生态服务功能。然而,截至2015年我国近海海草资源分布现状尚不明晰,严重制约了我国海草床保护与修复工作的开展。2015～2021年,笔者通过实地调查,借助船只走航、声呐探测、遥感等技术手段,重点对我国近海海草资源的分布面积、种类及主要威胁进行了全面普查,并据此提出我国海草床管理与可持续利用对策。结果表明,我国近海海域海草床面积共为26 495.69hm²,可划分为:温带海域海草分布区和热带-亚热带海域海草分布区;我国现有海草4科9属16种。其中,温带海域海草床面积为17 095.01 hm2,主要分布在辽宁、河北、天津和山东沿海,分布有2科3属5种,以鳗草(Zosteramarina)和日本鳗草(Z.japonica)为优势种,其中唐山乐亭-曹妃甸海草床面积达9 025.56 hm2,是我国面积最大的海草床;热带-亚热带海域海草床面积为9 400.68 hm2,主要分布在福建、广东、广西和海南沿海,分布有4科8属12种,以泰来草(Thalassia hemprichii)、海菖蒲(Enhalus acoroides...     

盐度对大叶藻种子萌发和幼苗发育的影响

大叶藻海草场是重要生境但在我国严重退化,亟需研究有效的修复方法。本文以桑沟湾的大叶藻种子为研究对象,探讨了盐度急变(0~30)对种子萌发、萌发后继续发育和存活及幼苗幼叶的光合与呼吸速率的影响,为以种子繁殖修复大叶藻海草场提供参考。结果表明:盐度降低促进种子萌发,盐度15及以下效果显著,盐度0时萌发率最高;盐度0~15中萌发的种子均可发育成幼苗,发育和衰亡的比例和速率受萌发盐度背景和萌发后培养盐度的双重影响——较高萌发盐度有利于种子萌发后的发育和存活,种子萌发后于盐度5~30中均可建成幼苗并存活、但在盐度0或1中发育至不同程度后全部死亡。盐度5~30范围内,幼苗幼叶均有净产氧,光合和呼吸作用及净产氧率具随盐度升高而增强趋势。于盐度0或5中萌发、盐度5~30中进一步培育的变盐育苗策略,最高实现了24%或12%的种子于2个月内建成幼苗并继续发育,可作为种子繁殖法修复大叶藻海草场的技术参考。     

大叶藻种子萌发环境条件研究

大叶藻海草床的退化和恢复受到国内外学者的广泛关注,而大叶藻种子萌发则是恢复实践中的一项关键技术。为了提高大叶藻种子萌发率,本研究在实验室可控条件下,采用正交实验对影响大叶藻种子萌发的环境因素(盐度、温度、N/P营养盐浓度及p H)进行了优化,并在优化条件下进一步探究了光质类型、UV-B辐射、低温层积和划破种皮对大叶藻种子萌发和平均萌发时间的影响。结果表明:盐度12、温度10°C、N/P营养盐浓度960/60μmol/L、p H 6.2是大叶藻种子相对适宜的萌发条件组合;黑暗条件下大叶藻种子萌发率最高,为92%,不同类型光质照射不促进大叶藻种子萌发率的提高,但红光照射可在短期内加速种子萌发;在一定强度范围内,种子萌发率随UV-B辐射时长的增加而升高,每日辐射8h,处理8周后种子萌发率可达93%。划破种皮和低温层积均可显著提高大叶藻种子的萌发率并缩短平均萌发时间,经划破种皮处理后,2周内种子萌发率可提高至91%。     

<Emphasis Type="Italic">Zostera marina</Emphasis> seed burial can be enhanced by Manila clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis>: A microcosm study

Seagrass seed bank plays a key role in the regeneration of new vegetation when seagrasses are removed by the natural or man-made disaster. Various factors may affect the development of sediment seed bank. We conducted a microcosm experiment to test the effects of burrowing and feeding activities of Manila clam, Ruditapes philippinarum on the burial of Zostera marina seeds in sediments. The effects of lasting time (3-hour, 1-day, 3-day, 7-day, 14-day and 28-day), clam density (0, 2, 4 and 8 clams with shell length of 3 cm in each microcosm) and clam size (shell length of 2, 3 and 4 cm at 4-clam density) on seed burial were examined in plastic microcosm cores (30 cm high × 10 in inner diameter) in a 28-day period. Results showed that the seed burial depth significantly increased with time, the density and the size of clams. No seeds were buried in the sediment in the cores without clams during the whole experiment period. For the 3-cm clams, about 91.61% of the seeds were buried in the sediment at the end of the experiment in the high-density treatment (8 clams at each core); while in the medium and low-density treatments (4 and 2 clams in each core, respectively), about 76.93% and 60.61% of the seeds were buried in the sediment, respectively. For the size treatments, large (4 cm) clams buried 89.56% of the seeds at the end of the experiment, much more than those of medium (3 cm, 76.93%) and small (2 cm, 61.50%) size clams. During the whole experiment period, nearly all of the buried seeds were at a depth of from 0 cm to 5 cm. These results suggested that Manila clam Ruditapes philippinarum may play an important positive role in seagrass seed bank dynamics in the field.     

The behavioral and antioxidant response of the bivalve Gomphina veneriformis to sediment burial effect

A laboratory-based microcosm experiment was carried out to examine both the behavioral and antioxidant response of the clam Gomphina veneriformis under the conditions of 3 types of burial material(sand,silt,silt-sand mixture) with 3 burial depths(5 cm,15 cm,30 cm).The concentration of dissolved oxygen decreased significantly after 3 d of burial in all experimental groups.In silt and sand-silt mixture groups,the interstitial water quality became worsened with lower pH,and higher NH_4~+-N concentration,where clam mortality occurred simultaneously.However,clam samples in all sand groups and 5 cm,15 cm sand-silt mixture groups survived well for 8 d.Obviously fewer individuals left in the bottom sand in the 15 cm,30 cm silt groups and 30 cm sand-silt mixture groups than in the 5 cm groups.Therefore,it suggests that adding silt and increasing burial depth could stimulate the vertical movement of organisms and cause lethal effects.It was found that the burial depth was the key factor that influenced the activities of antioxidant enzymes,such as superoxide dismutase(SOD) and catalase(CAT).The SOD and CAT activities in the gills and hepatopancreases of organisms both showed significant upregulation in 30 cm burial depth after buried for 8 d.Higher enzyme activities were found in gills than in hepatopancreases,which indicated that the gills of the bivalve G.veneriformis were more susceptible to burial effects than hepatopancreases.Overall,this study shows that sediment burial could cause effects on the biological behavior and antioxidant enzyme activities.     

Burial tolerances of reef-building Sabellariid worms from the east coast of Florida

Sabellariid worms, such as Phragmatopoma lapidosa, are sessile suspension feeders that attach to exposed hard bottom and serve as foundation species for worm reefs which are complex, multifaceted habitats. While worm reefs are adapted to dynamic sedimentary environments, burial of these habitats by beach nourishment projects is a concern. This study determined duration and depth of burial that can be tolerated by P. lapidosa without death. Worm rock samples were buried in sand at 1–10 cm (1-cm intervals), and at 15, 25 and 40 cm for the duration of 72, 144, and 216 h and then surveyed for initial mortality after burial and one week after removal of sediment (latent effects). Initial mortality was similar across all burial depths for the 72-h duration with values ranging from 8.3% (±0.8 SE) for 1 cm to 24.0% (±8.0 SE) for 10 cm of sediment. As burial duration increased to 144 h, mortality generally increased as burial depth increased with an average mortality for 2 cm of sediment of 23.5% (±5.3 SE) increasing to 96.0% (±14.3 SE) with 40 cm of sediment. The mean percent mortality for burial samples in the 216 h treatment varied from a low of 71.2% (±3.3 SE) for 1 cm depth to a high of 100% (±0 SE) for 10, 15, 25, and 40 cm depths. Mortality for most treatments also increased over time after removal of sediment indicating latent effects of burial stress.     

Burial and degradation of organic carbon in Louisiana shelf/slope sediments

The primary focus of this paper is to better understand carbon burial on the Louisiana continental margin using spatial scales that covered various shelf depositional areas far-field and near-field (sediment and organic carbon inputs relative to river mouth proximity) and covering a variety of sedimentation rates. Box-cores samples were collected in July 2003; cores were collected along two depositional transects extending westward and southward from the Southwest Pass (SW Pass). A key difference between the two transects sampled in this study was the greater occurrence of mobile muds derived from spillover from shallower regions along the westward 50 m isobaths. The dominant mechanism for mixing in the surface active zone (SAZ) on the inner Louisiana shelf was due to physical, not biological, forces. Burial efficiencies for organic carbon (57.2–91.5%) and total nitrogen (44.2–86.9%) ranged widely across all shelf stations. Lower burial efficiencies for bulk organic carbon, total nitrogen, and pigment biomarkers were associated with mobile muds west of Southwest Pass. Chlorophyll a concentrations were significantly higher than pheopigments at depth at the Mississippi River and Southwest Pass stations, making up 40.4 and 77.4% of total pigment concentrations in the (SAZ) and 46.2 and 63.2% in the accumulation zone (AZ), respectively. These results are in agreement with earlier plant pigment studies which showed that a large fraction of the phytodetritus delivered to the inner shelf was derived from coastal and river diatoms. The amount of lignin preserved with depth decreased with increasing residence time in the SAZ and diagenetic zone (DZ) along the canyon transect but not along the western transect. Trends for lignin concentration followed previously identified surface sediment trends indicating overall lower burial of refractory terrestrial material at depth with greater distance offshore.     

Self-Burial of Short Cylinders Under Oscillatory Flows and Combined Waves Plus Currents

Self-burial processes of finite-length cylinders under oscillatory flows and waves plus currents were examined with the following two different experimental facilities: a large oscillating water-sediment tunnel (LOWST) and a large wave-current tank. More than 130 experiments, with different model cylinders, were conducted within both facilities. The burial mechanisms studied include burial due to local scour and bedform migration. Burial due to fluidization in the tunnel was also explored, but only in a qualitative way. In the case of experiments with LOWST, the equilibrium burial depth was found to be a power function of the shields parameter (thetas). In the wave-current tank, the equilibrium burial depth was also found to be a function of the Shields parameter, albeit with larger scatter. The experimental observations made in both facilities have similar trends but different magnitudes. For equivalent values of the Shields parameter, smaller equilibrium burial depths were observed in the wave flume when compared to the ones in LOWST. After burial induced by local scour takes place, bedform (ripples and sandwaves) formation and evolution play a strong and, in some cases, dominant role on the equilibrium burial depth of the cylinders. Depending on how the vertical dimensions of bedforms compare to the specimen's diameter, cyclical covering and uncovering of the object may take place due to the passage of the migrating sandwaves. In such case, burial depth B_d no longer coincides with the vertical displacement (V_d) of the object as in the case when the burial process is dominated by local scour.     

Reproduction of the eelgrass Zostera marina at the species southern distributional limit in the Eastern Atlantic

The plant reproductive effort, the seed germination rate and the seedling survival and development of Zostera marina (eelgrass) were assessed in four populations (Fuzeta, Culatra, Barrinha and Armona) at the species’ southern distribution limit in the Eastern Atlantic, the Ria Formosa lagoon. Germinated seeds were individually placed in Petri dishes with natural sandy sediments and kept in a culture chamber at the same temperature and salinity conditions as the natural environment. In addition, seeds from three different depths of Fuzeta population were cultivated in outdoor mesocosms. The populations of Fuzeta and Barrinha showed higher seed production and the seeds produced were heavier than the other populations. The germination of the seeds both in the laboratory and in the outdoor tanks began c. 8–12 weeks after the collection of the flowering shoots at a water temperature of 22 °C. The spontaneous germination in the laboratory (2.4–5.3%) and in the mesocosm experiment (5.6–8.9%) was low and from all the germinated seeds (n = 20) only three reached the seedling stage. The spontaneously germinated seeds from Fuzeta survived for a longer period than those from Barrinha, but only the germinated seeds of Barrinha reached the seedling stage (one‐leaf seedling stage). In outdoor tanks, higher seed germination and earlier seedling emergence (2 weeks after seeding) and survival (for 208 days) occurred for the seeds obtained from the shallow meadow. The reproductive effort of Z. marina populations of Ria Formosa showed that flowering shoots and seed traits are site‐specific. The low reproductive success indicated by the low germination and seedling survival suggests a bottleneck in the species’ reproductive cycle that may account for the scarce presence of the species in Ria Formosa lagoon. The high water temperatures of Ria Formosa in winter may partly explain this bottleneck. Increased temperatures due to climate change may reduce even further the sexual reproduction of Z. marina in its southern distributional limit in the Eastern Atlantic.     

Multibeam Observations of Mine Burial Near Clearwater, FL, Including Comparisons to Predictions of Wave-Induced Burial

A Kongsberg Simrad EM 3000 multibeam sonar (Kongsberg Simrad, Kongsberg, Norway) was used to conduct a set of six repeat high-resolution bathymetric surveys west of Indian Rocks Beach (IRB), just to the south of Clearwater, FL, between January and March 2003, to observe in situ scour and burial of instrumented inert mines and mine-like cylinders. Three closely located study sites were chosen: two fine-sand sites, a shallow one located in 13 m of water depth and a deep site located in 14 m of water depth; and a coarse-sand site in 13 m. Results from these surveys indicate that mines deployed in fine sand are nearly buried within two months of deployment (i.e., they sunk 74.5% or more below the ambient seafloor depth). Mines deployed in coarse sand showed a lesser amount of scour, burying until they present roughly the same hydrodynamic roughness as the surrounding rippled bedforms. These data were also used to test the validity of the Virginia Institute of Marine Science (VIMS, Gloucester Point, VA) 2-D burial model. The model worked well in areas of fine sand, sufficiently predicting burial over the course of the experiment. In the area of coarse sand, the model greatly overpredicted the amount of burial. This is believed to be due to the presence of rippled bedforms around the mines, which affect local bottom morphodynamics and are not accounted for in the model, an issue currently being addressed by the modelers. This paper focuses specifically on two instrumented mines: an acoustic mine located in fine sand and an optical instrumented mine located in coarse sand.     

Vertical migration and mortality of benthos in dredged material—part I: Mollusca

Benthic invertebrates have many characteristics which make them prime candidates for burial studies in dredged material. A major concern in dredging and disposal projects is the effect of burial on the survival of benthic invertebrates. The purpose of the research reported in this paper was to determine the ability of estuarine benthos—in particular three species of molluscs (Mercenaria mercenaria, Nucula proxima and Ilyanassa obsoleta)—to migrate vertically in natural and exotic sediments and to determine the survival of benthos when exposed to particular amounts of simulated dredged material.Mortalities generally increased with increased sediment depth, with increased burial time and with overlying sediments whose particle size distribution differed from that of the species native sediment. Temperature affected mortalities and vertical migration. It was concluded that vertical migration is a viable process which can significantly affect rehabilitation of a dredged disposal area. Under certain conditions, vertical migration should be considered, together with larval settling and immigration from outside impacted areas, as a mechanism of recruiting a dredgedump site.     

Sediment burial stimulates the growth and propagule production of Spartina alterniflora Loisel.

Spartina alterniflora Loisel., an extensively invasive species on the Chinese coast, is a focus of increasing management concern due to its high expansion rate in estuaries and tidal zone, and the significant damage it causes to native ecosystems. In order to understand the processes and mechanisms of invasion of S. alterniflora in China, the impact of three sediment types (sand, sand–loam mixture and loam) and five buried patterns (unburied, 50% burial of initial plant height, 75% burial of initial plant height, complete burial and repeated burial) on the growth of seedlings or ramets was investigated. Results showed that each of the three factors (sediment types, burial pattern and plant materials) and interactions between/among them, significantly affected height and clonal growth, and biomass accumulation and allocation. Plant height, total biomass and number of new vegetative propagules significantly increased with progressive burial treatments. However, the complete burial treatment resulted in the death of all plant materials, and the maximum values of three parameters were found in the 50% burial or repeated burial treatments. Plant responses were determined by the instantaneous thickness of sediment of each time burial rather than by the total quantity of repeated burial. The growth of S. alterniflora was not shown to be dependent on specific types of sediment in sedimentation environment. In contrast to the unburied control, the proportion of primary tillers produced directly from initial individuals and the ratio between the aboveground and belowground biomass were greater under burial treatments. Seedlings produced more new vegetative propagules than vegetative offspring in all experimental treatments, and the former were apt to produce ramets from rhizomes rather than primary tillers. It is concluded that under various sedimentation environments, the clonal spread efficiency of seedlings was higher than that of vegetative offspring, and there is a positive feedback relationship between sedimentation and the growth of S. alterniflora. Thus, moderate sedimentation may stimulate the invasion of exotic species, S. alterniflora in coastal China.