基于种子法的海菖蒲海草床恢复

海草床有重要的生态服务功能, 与红树林、珊瑚礁并称为海洋三大典型生态系统。但由于人类活动的干扰及气候变化的影响, 其分布面积在全球范围内急剧下降, 海草床保护和恢复已成为海洋生态学的研究热点。研究首次尝试在野外用种子法对热带海草优势种海菖蒲进行生态恢复, 并探究影响种子萌发及幼苗生长的因素。结果表明, 埋藏深度及种子保护对海菖蒲种子的萌发率影响显著。埋藏深度为6cm时, 海菖蒲种子的萌发率仅为1.25%, 大部分种子腐烂失活。埋藏深度为2cm时, 网袋埋藏种子的萌发率高达96.10%, 但直接埋藏种子的萌发率远远低于用网袋保护的种子, 这可能是由于生物扰动或动物捕食增加了种子的流失。春季大型藻类和附着藻类的爆发是导致海菖蒲幼苗生长受阻、成活率降低的主要因素之一。     

海南高隆湾海草床修复成效及影响因素

为缓解海南岛东海岸海草床的持续退化,在高隆湾光滩区采用单株定距移植法移植泰来草(Thalassia hemprichii)及海菖蒲(Enhalus acoroides)进行海草床修复研究,修复面积约为1000 m2.结果表明,采用铁架加网的修复方式,泰来草1 a后平均成活率为56.39％,其成活率在移植7个月后下降比较...     

东楮岛海草组织碳氮含量特征及环境影响因素

海草组织碳氮含量可快速响应外界环境影响,已经广泛用于海草生态系统健康评估的指示因子。2011—2012年对东楮岛大叶藻海草床进行4次采样调查,研究了不同季节海草组织碳氮含量特征,分析了环境因素对大叶藻组织碳氮含量的影响。结果表明:海草组织碳、氮含量有明显季节性变化。海草叶碳含量最大值出现在5月,为36.4%,最小值出现在12月,为30.8%;而海草叶氮含量最大值和最小值分别出现在2和5月,为2.73%和2.02%。环境因素的相关性分析表明,海水温度对海草叶碳含量和根氮含量具有显著影响,海水及沉积物间隙水中的氮营养盐对海草茎、叶中的碳含量和根、叶中的氮含量有显著影响。调查表明东楮岛海域海草组织氮含量高于世界平均水平,营养盐增加可能对大叶藻产生负面影响,为了保护东楮岛海草床,应严格控制该海域养殖海带过程中营养盐的使用,加强对海草床健康状况的野外监测以及环境因素对海草影响的室内模拟实验研究。     

海草的卫星遥感研究进展

海草、沙滩、砾石以及淤泥等不同底质类型对光谱的反射率不同,通过卫星遥感检测反射率的变化可以鉴别海草等底质类型。由于海草体内含有叶绿素a、叶绿素b以及花青素和叶黄素等色素,通过检测这些色素的光谱可以对海草分布以及生存状态进行卫星遥感检测。主要从多光谱、高光谱等角度对近岸光学浅水中海草的卫星遥感以及国内对海草和水体生物光学研究状况等方面进行阐述,并对未来的研究趋势进行展望。     

虾海草的研究进展

虾海草属(Phyllospadix)共有五种,其中两种是西北太平洋沿岸的特有种,三种是东北太平洋沿岸的特有种。虾海草草床为鱼类提供产卵、育幼和索饵场所。然而,由于自然条件的变迁和人类活动的影响,几乎所有的虾海草草床都处于衰退状态,山东半岛沿岸曾经十分丰富的虾海草资源也几乎消失殆尽。目前,我国对虾海草的研究很少。以美国为主的学者对虾海草的三个美洲特有种进行了大量研究,而以日本和韩国为主的学者则对其中两个亚洲特有种进行了一些研究。本文通过查阅文献资料,对虾海草形态、生长、生理和繁殖等内容进行了综述,并对我国今后的研究方向进行了展望,旨在为我国今后开展虾海草的研究提供借鉴。     

海南岛海湾与潟湖中海草的分布差异及影响分析

本文根据2002年至2016年调查数据,研究海南岛海湾与潟湖中海草的分布及其影响因素。结果表明:海南岛沿岸调查到海草共6属10种,优势种为泰来草与海菖蒲,种类数量呈现东部多、北部与南部少的特点;海草分布面积约53.7906km2,呈现北部大于南部、海湾大于潟湖的特点;覆盖度存在由北向南递增趋势。海南岛沿岸海草垂直分布呈现由陆向海梯度分布规律。海草在海湾分布宽度大,主要集中于礁坪内侧,呈现斑块状分布为主,局部区域零星分布的特征;在潟湖分布宽度较小,主要集中于受人为活动干扰较少区域,呈现斑块状或片状分布的特征。潮流、水深、盐度、光照、底质类型与人类活动等对海南岛沿岸海草分布的影响较大,同时藻类、贝类与鱼类等生物对海草存在一定的空间竞争。     

印尼混合海草床大型底栖生物丰度和多样性生态研究

海草床是海岸带最富生产力的生态系统之一,支撑着各种各样的伴生生物。热带的印度和太平洋地区被认为拥有海草植物种类多样性最高,且分布面积最广,然而,这个区域的海草床大型底栖生物我们知之甚少。为了填补认知的空白,我们在该区域开展了一项生态调查,旨在描述该区热带海草床大型底栖生物的丰度和多样性,以及确定大型底栖生物丰度、物种丰富度和群落结构是否明显存在断面内的站间变化和样地间变化。2014年5月和2015年10月我们分别在北苏拉威西省东海岸和西海岸开展野外工作,使用柱状取样器采集海草床大型底栖生物样品。所得样品共计鉴定14大类149种底栖生物,种类最为丰富的类别为多毛类（56种,占26%的总个体数）,十足类（20种,占9%的总个体数）和端足类（18种,占35%的总个体数）。东、西海岸海草床大型底栖生物表现出不同的空间分布模式。在东海岸,同一断面的大型底栖生物和端足类的丰度存在显著的站间差异;而在西海岸,大型底栖生物和多毛类的种类丰富度和丰度都表现出明显的站间变化,这可能归结于同一断面底质不均所造成。单因素ANOSIM以及MDS排序表明了北苏拉威西省东海岸和西海岸海草床大型底栖生物群落结构存在显著不同,正好对应于将海草床分成两大类型的栖息地,即西海岸的红树林-海草床-珊瑚连续体和东海岸的海草床-珊瑚连续体。与在热带海区开展的其他研究相比,本研究的大型底栖生物丰度和多样性处于中等水平。东、西海岸海草床大型底栖生物群落存在显著区别,其原因可能源于多方面,包括了沉积物模式,海草床结构和时间变化。     

海草床沉积物有机碳研究综述

海草床具有重要的生态系统服务功能,可以为海洋生物提供栖息地和食物来源,同时还具有重要的碳储存功能,海草床“蓝碳”功能日益受到学术界的重视,据研究全球每年海草床的碳埋藏量高达(2.7~4.4)×10⁷ MgC。近年来,由于人类活动的影响,世界范围内海草床衰退严重,导致海草床沉积物有机碳储量降低。本文综述了全球海草床沉积物有机碳的来源、组分、储量以及指示作用;从物理、化学和生物三方面讨论了影响海草床碳储量的环境因素。最后提出了未来主要研究方向,主要包括加强海草床碳通量普查,分析全球气候变化背景下海草床沉积物有机碳的变化机制,明确海草床碳储量流失速率,研究海岸带工程对海草床沉积物有机碳的影响。评估海草床沉积物有机碳储量及变化机制可以为全球海洋蓝碳研究提供科学依据。     

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。     

海南省海草床现状和生态系统修复与重建

文章评述了海南省海草床生态系统的分布、海草保护与管理、科学研究等各个方面的现状,以及生态系统修复与研究进展.指出海草生态系统具有特殊的资源价值和生态效益,对热带海岸社会经济可持续发展十分重要;另一方面对日益频繁的人类开发活动和自然环境变异十分敏感和脆弱,随着海南的开发建设,人口、资源环境压力加剧,海草资源已经受到开发活动的影响而急需保护.尽管政府采取了保护管理的各种措施,包括相关法律和海洋保护区、科学研究,但海草床生态系统仍然面临威胁.海草床生态系统在我国热带海洋生态环境变化和资源可持续利用研究中具有特别重要的意义.应当加强海草生态系统的调查、监测、评估、研究,以适应海草生态系统的保护、管理、恢复、重建和可持续发展的要求.     

Meadow fragmentation and reproductive output of the SE Asian seagrass Enhalus acoroides

Flower and fruit production of the abundant, tall, long-lived, dioecious, surface-pollinating seagrass species Enhalus acoroides (L.) Royle were estimated at seven sites in the reef flats off Bolinao (NW Luzon, The Philippines) featuring different fragmentation of the seagrass meadows. Fragmentation of the seagrass meadow was quantified as cover of E. acoroides and all seagrass species present in 20×20 m plots. E. acoroides and overall seagrass cover were correlated positively. The proportion of female flowers of E. acoroides that developed a fruit increased sharply as overall seagrass cover was around 50%. Apparent sex ratio bore no relationship with overall seagrass cover. This threshold-type of relationship suggests that fragmentation of seagrass meadows can have a major effect on the reproductive output of this species. A possible mechanism underlying these results would be a non-linear increase of the efficiency of trapping the surface-dispersed pollen with increasing seagrass canopy density. This provides the first evidence based on real data that fragmentation can affect the population dynamics of seagrass species.     

Sediment deposition and production in SE-Asia seagrass meadows

Seagrass meadows play an important role in the trapping and binding of particles in coastal sediments. Yet seagrass may also contribute to sediment production directly, through the deposition of detritus and also the deposition of the associated mineral particles. This study aims at estimating the contribution of different seagrass species growing across an extensive range of deposition to inorganic (carbonate and non-carbonate) and organic sediment production. Total daily deposition measured with sediment traps varied from 18.8 (±2.0) g DW m⁻² d⁻¹ in Silaqui (Philippines) to 681.1 (±102) g DW m⁻² d⁻¹ in Bay Tien (Vietnam). These measurements correspond to a single sampling event and represent sedimentation conditions during the dry season in SE-Asia coastal areas. Enhalus acoroides was the most common species in the seagrass meadows visited and, together with Thalassia hemprichii, was present at sites from low to very high deposition. Halodule uninervis and Cymodocea species were present in sites from low to medium deposition. The mineral load in seagrass leaves increased with age, and was high in E. acoroides because it had the largest and long-lived leaves (up to 417 mg calcium carbonate per leaf and 507 mg non-carbonate minerals per leaf) and low in H. uninervis with short-lived leaves (4 mg calcium carbonate per leaf and 2 mg non-carbonate minerals per leaf). In SE-Asia seagrass meadows non-carbonate minerals accumulate at slower rates than the production of calcium carbonate by the epiphytic community, consequently the final loads supported by fully grown leaves were, as average, lower than calcium carbonate loads. Our results show that organic and inorganic production of the seagrasses in SE-Asia represents a small contribution (maximum of 15%) of the materials sedimented on a daily base by the water column during the sampling period. The contribution of the carbonate fraction can be locally significant (i.e. 34% in Silaqui) in areas where the depositional flux is low, but is minor (<1%) in sites were siltation is significant (i.e. Umalagan and all the visited sites in Vietnam).     

Enhalus acoroides responses to experimental shoot density reductions in Haad Chao Mai National Park,Trang Province,Thailand

The effect of self‐shading and competition for light in the seagrass Enhalus acoroides were investigated with a density reduction experiment in Haad Chao Mai National Park, Trang Province, Thailand. The study was carried out in a monospecific meadow with a natural density of 141.0 ± 8.7 shoots·m^?2. The intent was to determine the response of E. acoroides beds to loss of shoots and thinning, which often occur during typhoons and severe storm activity. Permanent quadrats were manipulated by clipping the seagrass shoots to 140, 72, 36 and 16 shoots·m^?2, to yield natural, 50%, 25% and 10% densities, respectively. Reducing shoot density in E. acoroides increased underwater light intensity below the canopy, generating increased leaf surface area and shoot weight. Seagrass leaf width, growth rate, and number of leaves per shoot also increased with greater light. The extent of flowering varied among treatments with no consistent trend. Our results demonstrate that increasing the available light to E. acoroides produces an increasing leaf size response as self‐shading in the bed is reduced.     

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。     

海草凋落叶的溶解有机物的释放及其生物地球化学意义

Dissolved organic matter(DOM) represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon(C), 70% nitrogen(N) and 38% phosphorus(P) of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon(DOC), dissolved organic nitrogen(DON) and dissolved organic phosphorus(DOP) of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides(MCHO), DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/(g·d). Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON: DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production(the Xincun Bay, South China Sea), the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter(POM)from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.     

Sedimentary iron inputs stimulate seagrass (Posidonia oceanica) population growth in carbonate sediments

The relationship between sedimentary Fe inputs and net seagrass population growth across a range of Posidonia oceanica meadows growing in carbonate Mediterranean sediments (Balearic Islands, Spain; SE Iberian Peninsula, Spain; Limassol, Cyprus; Sounion, Greece) was examined using comparative analysis. Sedimentary Fe inputs were measured using benthic sediment traps and the net population growth of P. oceanica meadows was assessed using direct census of tagged plants. The meadows examined ranged from meadows undergoing a severe decline to expanding meadows (specific net population growth, from −0.14 yr⁻¹ to 0.05 yr⁻¹). Similarly, Fe inputs to the meadows ranged almost an order of magnitude across meadows (8.6–69.1 mg Fe m⁻² d⁻¹). There was a significant, positive relationship between sedimentary iron inputs and seagrass net population growth, accounting for 36% of the variability in population growth across meadows. The relationship obtained suggested that seagrass meadows receiving Fe inputs below 43 mg Fe m⁻² d⁻¹ are vulnerable and in risk of decline, confirming the pivotal role of Fe in the control of growth and the stability of seagrass meadows in carbonate sediments.     

Stratigraphic framework of sediment-starved sand ridges on a mixed siliciclastic/carbonate inner shelf; west-central Florida

Seismic reflection profiles and vibracores have revealed that an inner shelf, sand-ridge field has developed over the past few thousand years situated on an elevated, broad bedrock terrace. This terrace extends seaward of a major headland associated with the modern barrier-island coastline of west-central Florida. The overall geologic setting is a low-energy, sediment-starved, mixed siliciclastic/carbonate inner continental shelf supporting a thin sedimentary veneer. This veneer is arranged in a series of subparallel, shore-oblique, and to a minor extent, shore-parallel sand ridges. Seven major facies are present beneath the ridges, including a basal Neogene limestone gravel facies and a blue-green clay facies indicative of dominantly authigenic sedimentation. A major sequence boundary separates these older units from Holocene age, organic-rich mud facies (marsh), which grades upward into a muddy sand facies (lagoon or shallow open shelf/seagrass meadows). Cores reveal that the muddy shelf facies is either in sharp contact or grades upward into a shelly sand facies (ravinement or sudden termination of seagrass meadows). The shelly sand facies grades upward to a mixed siliciclastic/carbonate facies, which forms the sand ridges themselves. This mixed siliciclastic/carbonate facies differs from the sediment on the beach and shoreface, suggesting insignificant sediment exchange between the offshore ridges and the modern coastline. Additionally, the lack of early Holocene, pre-ridge facies in the troughs between the ridges suggests that the ridges themselves do not migrate laterally extensively. Radiocarbon dating has indicated that these sand ridges can form relatively quickly (1.3 ka) on relatively low-energy inner shelves once open-marine conditions are available, and that frequent, high-energy, storm-dominated conditions are not necessarily required. We suggest that the two inner shelf depositional models presented (open-shelf vs. migrating barrier-island) may have co-existed spatially and/or temporally to explain the distribution of facies and vertical facies contacts.     

Molluscan assemblages of seagrass-covered and bare intertidal flats on the Banc d'Arguin, Mauritania, in relation to characteristics of sediment and organic matter

The Banc d'Arguin, a non-estuarine area of shallows and intertidal flats off the tropical Saharan coast of Mauritania, is characterised by extensive intertidal and subtidal seagrass beds. We examined the characteristics of intertidal seagrass (Zostera noltii) meadows and bare areas in terms of the presence and abundance of molluscs (gastropods and bivalves). To explain observed differences between molluscan assemblages in seagrass and bare patches, some aspects of the feeding habitat (top-5 mm of the sediment) and of food (organic materials) of molluscs were examined. The novelty of this study is that phytopigments were measured and identified to assess source and level of decay (freshness) of organic material in the sediment and to study their importance as an explanatory variable for the distribution of molluscs. Over an area of 36 km² of intertidal flats, at 12 sites, paired comparisons were made between seagrass-covered and nearby bare patches. Within seagrass meadows, dry mass of living seagrass was large and amounted to 180 ±10 g AFDM m^− 2 (range 75–240). Containing twice the amount of silt per unit dry sediment mass, seagrass sediments were muddier than bare areas; the relative amount of organic material was also larger. The total number of species of bivalves and gastropods amounted to 27, 14 of which were found only in seagrass areas, 4 only in bare and 9 in both types of habitat. Among the three numerically most abundant species, the bivalves Anadara senilis, Dosinia hepatica and Loripes lacteus, the first was numerically most abundant in bare and the other two in seagrass-covered areas. Bare intertidal areas had greater mean total biomass of molluscs (80.5 g AFDM m^− 2) than seagrass meadows (30.0 g AFDM m^− 2). In both habitats, the bulk of the biomass was made up by A. senilis. Excluding this species, bare mudflats contained on average only 3.1 g AFDM m^− 2 and seagrass meadows 6.9 g AFDM m^− 2. As compared to previous surveys in 1980–1986, the biomass of A. senilis had increased almost 10-fold and D. hepatica, previously found in very small numbers, had become the most numerous species. However, the total biomass excluding that of A. senilis was similar. Concentrations of phytopigments were similar to those observed at temperate mudflats, indicating that the Banc d'Arguin might not be as oligotrophic as previously thought. Per unit of dry sediment mass, smaller amounts of phytopigments were found in bare than in seagrass areas. Per unit of dry organic material, bare sediments contained most (fresh) phytopigments. This suggests that in seagrass-covered meadows the organic material is more degraded than in bare sediments. Overall, the composition of phytopigments, quite surprisingly, indicated a benthic-diatom-dominated trophic system. Multivariate statistics revealed that patterns of zoobenthic assemblages were correlated with patterns of a combination of four environmental parameters: grain size of the sediment, amount of fresh phytopigments and amounts of leaves and roots of seagrass.     

Redefining the trophic importance of seagrasses for fauna in tropical Indo-Pacific meadows

Fauna species living in seagrass meadows depend on different food sources, with seagrasses often being marginally important for higher trophic levels. To determine the food web of a mixed-species tropical seagrass meadow in Sulawesi, Indonesia, we analyzed the stable isotope (δ¹³C and δ¹⁵N) signatures of primary producers, particulate organic matter (POM) and fauna species. In addition invertebrates, both infauna and macrobenthic, and fish densities were examined to identify the important species in the meadow. The aims of this study were to identify the main food sources of fauna species by comparing isotopic signatures of different primary producers and fauna, and to estimate qualitatively the importance of seagrass material in the food web. Phytoplankton and water column POM were the most depleted primary food sources for δ¹³C (range −23.1 to −19.6‰), but no fauna species depended only on these sources for carbon. Epiphytes and Sargassum sp. had intermediate δ¹³C values (−14.2 to −11.9‰). Sea urchins, gastropods and certain fish species were the main species assimilating this material. Seagrasses and sedimentary POM had the least depleted values (−11.5 to −5.7‰). Between the five seagrass species significant differences in δ¹³C were measured. The small species Halophila ovalis and Halodule uninervis were most depleted, the largest species Enhalus acoroides was least depleted, while Thalassia hemprichii and Cymodocea rotundata had intermediate values. Fourteen fauna species, accounting for 10% of the total fauna density, were shown to assimilate predominantly (>50%) seagrass material, either directly or indirectly by feeding on seagrass consumers. These species ranged from amphipods up to the benthic top predator Taeniura lymma. Besides these species, about half of the 55 fauna species analyzed had δ¹³C values higher than the least depleted non-seagrass source, indicating they depended at least partly for their food on seagrass material. This study shows that seagrass material is consumed by a large number of fauna species and is important for a large portion of the food web in tropical seagrass meadows.