Temporal and Morphological Variations of Growth in a Natural Stand of Posidonia oceanica (L.) Delile*     

Karl J. Wittmann 《Marine Ecology》1984,5(4):301-316

Abstract. Growth of Posidonia oceanica (L.) DELILE was studied in a natural stand in 4 m depth at Ischia (Gulf of Naples). Renewal and growth of leaves was continuous throughout the year but showed strong seasonal modulation. The major factor for individual leaf growth as well as for the seasonal aspects of the entire foliage is seasonal modulation of leaf appearance rather than of leaf growth. Leaf area index varied between 2 nm² m^-2 in autumn and 6 m² m^-2 in late summer. Annual production is estimated to be 613 g dw m^-2 for leaf blades, 54 g dw m^-2 for leaf sheaths, and 27 g dw m^-2 for rhizomes. Rhizome production is highly different between the primary and the secondary growth axis (274 versus 30 mg dw -shoot^-1 y^-1 respectively) in plagiotrope growth. Both foliage and rhizome growth are positively correlated with leaf width.  相似文献   

Impact of fish farming facilities on Posidonia oceanica meadows: a review     

Christine Pergent-Martini  Charles-François Boudouresque  Vanina Pasqualini  & Gérard Pergent 《Marine Ecology》2006,27(4):310-319

The impact of fish farming facilities on Posidonia oceanica meadows was assessed from studies of intensive facilities carried out over the last few years. The disturbances caused by these fish farms were measured by means of both abiotic (light, sediment, interstitial water) and biotic variables (meadow density, leaf biometry, lepidochronology, primary production, epiphytes, reserve carbohydrates in the rhizomes), in function of increasing distance from cages and/or inside a geographically close reference site. The results showed significant degradation of these seagrass meadows in all the sectors investigated. When fish farming cages were placed above a P. oceanica bed, the meadow was severely degraded or disappeared and the sediment showed a strong increase in organic matter that could lead to anoxia phenomena. The irreversible impact of fish farming projects on P. oceanica meadows requires the application of the precautionary principle. Several recommendations (site selection, preliminary studies and monitoring over time) are suggested in order to enable piscicultural activities to be incorporated in a global process of Integrated Coastal Zone Management.  相似文献   

The use of fractal geometry to determine the impact of inlet migration on the dynamics of a seagrass landscape     

A.H. Cunha  R.P. Santos 《Estuarine, Coastal and Shelf Science》2009,84(4):584-590

The use of fractal geometry to evaluate seagrass scaling behavior and the persistence of seagrass landscape patterns in relation to a disturbance is presented in this paper.Ria Formosa is a dynamic barrier-island system with a migrating inlet that creates a cyclic disturbance in a seagrass landscape. Seagrass patches which develop in the intertidal and shallow subtidal areas of Ria Formosa were digitized from a temporal sequence of aerial photographs, from 1980 to 1998. The methodology used to evaluate seagrass scaling behavior was proposed by Meltzer and Hastings (1992), and relates the frequency distribution of patch size with the existence of patch size-related patterns. The Hurst exponent was calculated to assess the temporal persistence of the seagrass landscape. Univariate regression was used to investigate relations between temporal persistence and disturbance. The existence of patch size-related patterns was identified for all years suggesting shifts in generating processes occurring at different domains of scales in the seagrass landscape. The results enforces the idea that it is important to recognize the existence of diverse processes occurring at different domains of scales and, emphasizes the importance of evaluating issues of temporal and spatial scale while trying to understand changes in seagrass landscapes. The Hurst exponent estimates show that although the migration and relocation of the inlet affected this system the evolutionary trajectory of the seagrass landscape is persistent, i.e., the patch dynamics observed is stable. Furthermore, persistence values were different for differently sized patches, small patches having lower persistence then larger patches.  相似文献   

Carbon sources supporting a diverse fish community in a tropical coastal ecosystem (Gazi Bay,Kenya)     

J. Nyunja  M. Ntiba  J. Onyari  K. Mavuti  K. Soetaert  S. Bouillon 《Estuarine, Coastal and Shelf Science》2009

Interlinked mangrove–seagrass ecosystems are characteristic features of many tropical coastal areas, where they act as feeding and nursery grounds for a variety of fishes and invertebrates. The autotrophic carbon sources supporting fisheries in Gazi bay (Kenya) were studied in three sites, two located in the tidal creeks flowing through extensive mangrove forests, another site located in the subtidal seagrass meadows, approximately 2.5 km away from the forest. Carbon and nitrogen stable isotope composition of 42 fish species, 2 crustacean species and a range of potential primary food sources (e.g., mangroves, seagrasses and epiphytes, macroalgae) were analysed. There was considerable overlap in the δ¹³C signatures between fish (−16.1 ± 2.1‰), seagrasses (−15.1 ± 3.0‰), seagrass epiphytes (−13.6 ± 3.3‰), and macroalgae (−20.4 ± 3.1‰). Nevertheless, the signatures for most primary producers were sufficiently distinct to indicate that the dominant carbon sources for fish were mainly derived from the seagrass and their associated epiphytic community, and possibly macroalgae. Mangrove-derived organic matter contributes only marginally to the overall fish food web. Carbon supporting these fish communities was derived directly through grazing by herbivorous and some omnivorous fishes, or indirectly through the benthic food web. Fishes from the mangrove creeks had distinctly lower δ¹³C signatures (−16.8 ± 2.0‰) compared to those collected in the adjacent seagrass beds (−14.7 ± 1.7‰). This indicated that these habitats were used as distinct sheltering and feeding zones for the fishes collected, with minimal degree of exchange within the fish communities despite their regular movement pattern.  相似文献   

Heavy Metal Contents in Soft-Bottom Marine Macrophytes and Sediments Along the Mediterranean Coast of Spain     

Carles Sanchiz  Antonio M. García-Carrascosa  & Augustin Pastor 《Marine Ecology》2000,21(1):1-16

Abstract. Hg, Cd, Pb and Zn concentrations were determined in sediment and in tissues of five species of soft-bottom marine macrophytes ( Posidonia oceanica, Cymodocea nodosa, Zostera noltii, Ruppia cirrhosa and Caulerpa prolifera ) along the Spanish Mediterranean coast. Levels of metals were low in most of the sampling stations and similar to those found by other authors in uncontaminated zones. Certain locations, however, showed some degree of contamination (Cambrils, Almassora, Alacant, Mar Menor and El Portús). In Santa Pola we found high contents of metals in one sample of sediment due to the high proportion of the fine fraction (particules < 63µm) and organic matter, but not in the seagrass species. Mercury and zinc concentrations in the sediment are correlated to those in at least some anatomic fractions of Posidonia oceanica, Cymodocea nodosa and Caulerpa prolifera , suggesting that these species reflect the levels of these metals in the environment. Lead contents in the alga Caulerpa prolifera are also correlated to those in the sediment, while no significant correlations were obtained for cadmium. Among the species studied, Posidonia oceanica and Cymodocea nodosa seem to be better biomonitors than Caulerpa prolifera .  相似文献   

Temporal dynamics of subtidal Zostera marina and intertidal Zostera japonica on the southern coast of Korea     

Sang Yong Lee  Jeong Bae Kim  & Sung Mi Lee 《Marine Ecology》2006,27(2):133-144

The temporal dynamics of two seagrass species, Zostera marina and Z. japonica, were monitored monthly in Dadae Bay, Geoje Island, on the southern coast of Korea. Plant morphological characteristics, shoot density, biomass, leaf production, reproductive effort, and environmental characteristics were monitored from July 2001 to July 2002. Zostera japonica occurred in the intertidal zone and Z. marina occurred in the subtidal zone from 0.5 to 2.5 m below the mean low water level. Shoots and rhizomes were significantly larger in Z. marina than in Z. japonica, whereas the shoot density was greater in Z. japonica than in Z. marina. Despite differences in morphology and shoot density, biomass did not differ significantly between the species. Reproduction occurred from April to June in Z. marina and from May to July in Z. japonica. The proportion of reproductive shoots was approximately three times higher in Z. marina than in Z. japonica. Seasonal variation in the biomass of Z. japonica was caused by changes in both shoot size and density, whereas that of Z. marina was mainly caused by changes in shoot length. Leaf production in Z. marina and Z. japonica showed clear seasonal variation, and leaf production in Z. marina (2.6 ± 0.2 g DW·m⁻²·day⁻¹) was higher than that in Z. japonica (1.7 ± 0.2 g DW·m⁻²·day⁻¹). The mean plastochrone interval was not significantly different between the two species, whereas the leaf lifetime of Z. marina was longer (69 ± 7.8 days) than that of Z. japonica (59 ± 8.3 days). Our results indicated that seasonal leaf growth patterns in Z. japonica are correlated with irradiance and temperature, whereas those in Z. marina respond most to irradiance. Seasonal changes in irradiance appeared to control the temporal variation in above‐ground biomass in both species.  相似文献   

Temporal changes of mollusc populations from a Zostera marina bed in southern Spain (Alboran Sea), with biogeographic considerations     

María del Carmen Arroyo  Carmen Salas  José Luis Rueda  & Serge Gofas 《Marine Ecology》2006,27(4):417-430

Molluscs associated with a Zostera marina bed from Cantarriján bay (Southern Spain, Alboran Sea) at 14–16 m depth were sampled monthly from October 1996 to September 1997. A total of 44,819 individuals belonging to 80 species were identified. In spite of the high species richness, only seven species of gastropods showed a dominance value (D) higher than 1%. Jujubinus striatus was the dominant species of the assemblage with 70.8% of the total abundance. The other dominant species were Rissoa membranacea (9.8%), Nassarius pygmaeus (5.8%), Mitrella minor (4%), Smaragdia viridis (1.9%), Rissoa monodonta (1.4%), Bittium reticulatum (1.3%). The dynamic pattern of the mollusc populations showed a temporal trend with monthly values of species richness and abundance ranging between 10 and 25 species and between 178 and 4412 individuals·222 m⁻². The species richness and abundance were higher in the spring and summer months than in the autumn and winter ones. The diversity (Shannon–Wiener, H’) follows a similar trend, with increases from April to September and decreases from October to March. H’ values (ranging from 0.45 to 3.10) are more influenced by the evenness (J) than by the species richness. A multivariate analysis (Cluster, Multi-dimensional Scaling) based on both presence/absence and quantitative data has also pointed out a temporal trend, with spring–summer samples significantly different from autumn–winter samples. The temporal changes in abundance seem related with the species’ biology, such as recruitment events, as well as to the canopy features and shoot density variation in the Zostera meadow. From the biogeographical point of view, most of the molluscs (65%) found in the Cantarriján bed, have a Lusitanian–Mediterranean distribution (sensu Ekman 1953 ). The proximity to Africa is shown by the presence of four species with a mainly West African distribution. Only R. membranacea has a typical Atlantic distribution, driven by that of Z. marina in NW Europe.  相似文献   

中国海草的“藻”名更改   总被引：2，自引：0，他引：2  

黄小平  江志坚  范航清  陈小勇  周毅  张景平  李文涛  张沛东  郑凤英  韩秋影  邱广龙  方静威  林幸助  孙涛  于硕  刘松林  吴云超  张晓梅  赵鹏  林海英 《海洋与湖沼》2016,47(1):290-294

海草(Seagrasses)是地球上可完全生活在海水中的被子植物,是由陆地植物演化到适应海洋环境的高等植物。然而,高等植物海草在中国经常被冠以低等植物"藻"的名称。中国海草现有22种,隶属于4科10属,其中科名、属名和种名分别有3科、7属和16种是以"藻"命名的,易让人们把海草误以为是海藻(Seaweed),造成混乱,同时给中国海草的研究、保护和利用带来不利影响。值此"第十一次国际海草生物学研讨会"(The 11th International Seagrass Biology Workshop)首次在中国举行之际,国内众多的海草研究专家得以共聚,有机会共同探讨中国海草的"藻"名更改。经过研讨,专家们形成一致意见,建议将这些被命名为"藻"的海草统一命名为"草",以期促进我国海草研究与保护的全面推进。随着未来中国海草种类与分布的深入调查,以后新发现的海草种类名称建议也统一命名为"草"名。  相似文献   

Diel Changes in Assemblages of Fishes Associated with Shallow Seagrass and Bare Sand     

C.A. Gray  R.C. Chick  D.J. McElligott 《Estuarine, Coastal and Shelf Science》1998,46(6):849-859

The evaluation and management of fisheries resources requires knowledge of spatial and temporal changes in the habitat-associations of fishes. However, most studies concerning habitat associations of small fishes in the shallow regions of estuaries have been limited to daytime sampling strategies. Diel changes were investigated in assemblages of fishes associated with shallow seagrass (Zostera capricorni) and bare sand in two estuaries in south-eastern Australia. Habitat-related differences in assemblages were strong day and night, and were greater than diel changes in assemblages. The seagrass-associated assemblages remained similar day and night and consistently differed from those associated with bare sand. In contrast, the assemblages over sand varied on a diel basis as larger individuals of several species (e.g.Gerres subfasciatus,Platycephalus fuscus) that resided over other (deeper) habitats during the day were caught over shallow sand at night. Further, some species (e.g.Ambassis jacksoniensis) that resided in seagrass during the day occurred over sand at night. Both habitats were utilized by newly recruited juveniles of economically important species and the habitat-associations of these species generally did not differ on a diel basis. Therefore, both habitats are considered important to the fisheries resources of south-eastern Australia. Inclusion of night-time sampling provided a greater understanding and appreciation of the use of the unvegetated habitat by fishes than has previously been acknowledged from studies based solely on daytime sampling. This study indicates that greater consideration of temporal changes in habitat associations of fishes is required in other geographic regions.  相似文献   

海草场的生态功能   总被引：5，自引：0，他引：5  

李文涛  张秀梅 《中国海洋大学学报(自然科学版)》2009,39(5)

海草场作为特殊的海洋生态系统之一,尽管其面积占海洋总面积的比例很小,但其具有极高的初级生产力,在地球系统碳循环中起着不可忽视的作用。海草本身还可以作为其他附着生物的附着基,进一步提高了海草场的初级生产力,并为许多海洋动物提供了适宜的食物。海草场的存在,改变了海草场内的流体动力过程,加速了悬浮颗粒的沉降,对稳定海底底质和净化水质有着积极的作用,因此被称为"生态系统工程师"。海草本身可以作为一些海洋动物的食物,同时其复杂的地下和地上结构还为一些海洋动物提供了庇护和栖息场所。而海草植物体的大部分,将最终被微生物分解利用,所产生的营养盐可以满足其它初级生产者生长所需。本文通过总结世界范围内海草场生态学研究成果,旨在阐述海草场生态系统的特征及功能,以提高人们对海草场生态功能的认识,唤起人们对海草场的重视与保护意识。  相似文献