The reproductive biology of a shallow water morid (Salilota australis Günther, 1878), around the Falkland Islands

The reproductive biology of a shelf morid, red cod (Salilota australis) was investigated in the Falkland Islands, in order to expand our knowledge of the reproductive strategy of this relatively unstudied family of fishes. Red cod spawn to the south and south-west of West Falkland between August and October. Length frequency and sex ratio data suggest that females arrive at the spawning grounds first. The greatest spawning activity occurred in early evening and this timing may be an adaptation to reduce predation on eggs. Ripe egg size varied from 0.95 to 1.26 mm and was not dependant on female size. There was no regulative atresia during maturation and the formation of fecundity and fecundity increased with increasing fish total length (L_T) from 300,000 (42-45 cm L_T) to 4.5-9.0 million eggs (75-83 cm L_T). The fecundity of most of the population was between 2 and 5 million eggs. Red cod releases small batches of eggs over the spawning period. Batch size ranged from 30,000-90,000 (39-42 cm L_T) in smaller animals to 400,000-800,000 (>75 cm L_T) in larger animals and the batch size of first spawners was significantly higher than for advanced spawners. The study allows us to discuss the evolutionary relationships between the Gadiformes.     

Resource partitioning by two large planktivorous fishes Micromesistius australis and Macruronus magellanicus in the Southwest Atlantic

The ontogenetic, seasonal, bathymetric and regional variations in the feeding spectrum of 922 specimens of southern blue whiting Micromesistius australis and 512 specimens of hoki Macruronus magellanicus were studied on the Falkland Islands’ shelf (Southwest Atlantic) between November 1999 and April 2003. A total of 49 different prey items were found in the stomach contents of the two species, with the hyperiid Themisto gaudichaudii and Euphausiacea being amongst the most important prey. Although the species composition did not change over fish size, the proportions of individual prey items in their diets did, with an increase in T. gaudichaudii and Euphausiacea with increasing fish size in southern blue whiting. The opposite occurred in hoki. Seasonal variations in the diet were found to mirror the seasonal abundance of prey around the Falkland Islands for the two species. Intra-specific differences in the diet of both predators reflected the distribution of prey, which in turn was determined by the water structure in the two regions sampled, leading to very different diets. In the limited time that the two species occupied the same space there was little or no competition resulting in almost total segregation of their trophic niches in space and time.     

In situ experimental study of reed leaf decomposition along a full salinity gradient

An experimental study on Phragmites australis leaf litter decomposition was conducted in the estuarine environment, Ria de Aveiro, Western Portugal, using the leaf-bag technique, with fine- (1 mm) and coarse-mesh (5 mm) bags. The leaf bags were placed in the field sites at day 0, covering a complete salinity gradient, and replicates were collected over time, at days 3 (leaching), 7, 15, 30 and 60. The biomass loss through the leaching phase, about 20% of the initial leaf mass, was independent of both the salinity and the bag mesh size. The biomass decay pattern along the salinity gradient varied through time and presented strong similarities between the two mesh sizes, with the remaining biomass always lower in the 5 mm mesh-size bags. At days 7 and 15, the lowest remaining biomass was observed at the head of the estuary, the preferential distribution area of P. australis. At day 30, the remaining biomass was higher in the marine area and diminished under a direct relationship with salinity, reaching the lowest value in the freshwater environment, with values ranging from 66% to 44% of the initial weight in 5 mm bags, and from 79% to 51% in 1 mm bags. The largest heterogeneity in the remaining biomass among the study areas positioned along the salinity gradient was found close to days 30 (5 mm) and 40 (1 mm). The overall results indicate that the relationship between leaf decay rate and salinity depends on the decay time considered (k₁₅, k₃₀ or k₆₀) and, for the later stages (k₆₀), also on the leaf-bag mesh size. This implies that the use of leaf litter decay rates as a functional indicator in transitional waters will need to take into consideration the factor location in the salinity gradient and leaf litter stage at which the decay rate is determined. The differences between the decay rates with the mesh size acted mainly at the level of the absolute k value and not at the level of the pattern along the salinity gradient. Even so, the data obtained at the mouth of the estuary, in the area closest to a fully marine environment, indicated that after the initial biomass loss through leaching, P. australis decayed either very slowly, in the 5 mm, or not at all, in the 1 mm mesh bags.     

Transplantation as a method for restoring the seagrass Posidonia australis

Transplant trials of the seagrass Posidonia australis were carried out after loss of seagrasses following eutrophication and increased turbidity in two marine inlets on the south coast of Western Australia. A pilot study in Oyster Harbour measured survival and growth in situ for 4 years. Long-term survival rates were high (96–98%), providing plants were anchored into the sediment. All unanchored plants were lost in the first winter. Following the success of the pilot study, a more comprehensive program began 3 years later with over 500 transplant units collected from either actively growing edges of nearby patches (plagiotropic growth form) or within established meadows (orthotropic growth form). Transplant units from edges expanded at a faster rate compared to units from mid-meadow but increases in shoot numbers were similar. Growth rates in the first 2.5 years averaged 10–20 cm yr⁻¹ horizontal rhizome extension, depending on the source of the transplant units, and 4–12 shoots per initial shoot yr⁻¹, depending on the initial shoot number of the transplant unit. After 5 years, shoot numbers of individual transplants were similar to shoot densities recorded for natural meadows, >500 shoots m⁻². Approximately, 10% of transplants from mid-meadow flowered in the first year, whereas transplants from edges flowered only after 5 years.     

Influence of an altered salinity regime on the population structure of two infaunal bivalve species

Hydrological alterations in watersheds have changed the flows of freshwater to many nearshore marine environments. The ensuing alterations to the salinity environment of coastal waters may have implications for species distribution. This study describes the response of two common bivalves to a modified salinity environment imposed by freshwater inputs from a hydroelectric power station in Doubtful Sound, New Zealand. Populations of Austrovenus stutchburyi and Paphies australis inhabiting river deltas near the outflow of the power station in inner Doubtful Sound were more than an order of magnitude smaller in abundance than populations in neighbouring Bradshaw Sound where the salinity regime is unaltered. In addition, there was a lack of small size classes of both species in inner Doubtful Sound, suggesting that these populations are unsustainable over the long term (10–20 years). Laboratory experiments demonstrated that sustained exposure (>30 days) to low salinity (<10) significantly decreased bivalve survivorship; however, both species survived periods of exposure to freshwater up to at least 20 days in duration if followed by a period of return to normal seawater salinity. Examination of the extant salinity regime in light of these results indicates the current salinity environment in Doubtful Sound restricts bivalves to deeper waters (5–6 m depth). The observed discrepancy in the total biomass of these active suspension feeders between altered and control sites has potential implications for the flux of organic matter in the food webs of Fiordland's shallow soft sediment communities.     

Choice chamber experiments to test the attraction of postflexion Rhabdosargus holubi larvae to water of estuarine and riverine origin

Although the recruitment of larvae and juveniles of marine fishes into estuaries has been well documented, little is known about the factors governing the immigration of estuary-associated marine fishes into estuaries. Fishes have a well-developed sense of smell and it has been suggested by several workers that olfactory cues of freshwater or estuarine origin serve as stimuli, attracting larvae and juveniles of estuary-associated species into estuaries. Attraction of postflexion Rhabdosargus holubi larvae to estuary and river water from the Kowie estuarine system, South Africa, was measured using a rectangular choice chamber. In experiments, conducted during peak recruitment periods, larvae selected estuary and river water with a significantly higher frequency than sea water. This study, the first to assess the possible role of olfaction in the recruitment process of an estuary-associated marine fish species, demonstrates that larvae are able to recognise water from different origins, probably based on odour.     

CO2升高和阳光紫外辐射对坛紫菜生长和光合特性的耦合效应

大气CO₂持续升高,导致溶入海水中的CO₂增多,海水表层的H+浓度增加,从而引起海洋酸化。为了探讨近岸定生大型海藻对这种环境变化的响应,本文选择经济海藻坛紫菜为实验材料,研究海洋酸化与紫外辐射对藻体生长以及光合特性的影响。实验分两个CO₂处理,分别为正常空气水平(390 ppmv)和高CO₂水平(800 ppmv); 三种辐射处理,分别为全波长辐射(PAB)、滤除紫外线B(PA)和仅接受可见光处理(PAR)。研究结果表明,CO₂培养下的坛紫菜,在仅有可见光(P)或者同时有紫外线A(PA)存在的情况下,显著促进藻体的生长;但在全波长辐射处理下(PAB),这种作用不明显。高CO₂降低了藻体在P和PA处理下的光合作用速率,但对PAB处理作用不显著。高CO₂处理下的藻体,UV-B显著降低了全波长辐射下藻体紫外吸收物质的含量,但在正常CO₂水平下,紫外辐射的作用不显著。这表明高CO₂导致的生长优势被紫外辐射的负面效应所抵消,在全球变化的过程中,紫外辐射的进一步加强在海洋酸化的背景下甚至有可能降低坛紫菜的产量。     

海月水母与海蜇不同幼体阶段的种间短期竞争研究

近年来海蜇池塘养殖业的兴起,补充了传统海蜇渔业捕捞生产的不足,推动了海蜇产业的迅猛发展。海月水母常常在海蜇养殖池塘中泛滥成灾,对海蜇养殖业常常造成很大损失,但关于海蜇与海月水母的种间竞争关系尚缺乏研究。本文对海月水母与海蜇的螅状体、碟状体及水母体幼体相互之间的短期生存竞争关系进行了初步观察研究。结果表明:除海月水母碟状体可以被海蜇螅状体所捕食外,各种类型的海蜇幼体基本不能对海月水母幼体造成危害。但海月水母螅状体及其水母体幼体对海蜇幼体均存在一定的危害性,尤其是对海蜇碟状体的危害性最为严重,在饵料缺乏的情况下海蜇碟状体可以100%地被捕食。随着海蜇幼体的生长,其对于海月水母危害的抵抗力逐渐增强。本研究显示海月水母相对于海蜇而言,在幼体种间竞争关系中处于绝对优势,这是海月水母时常暴发成灾的一个重要因素。在海蜇池塘养殖生产及苗种培育过程中,应当严禁混入海月水母幼体,以避免对海蜇养殖生产造成损害。     

泥蚶、缢蛏和僧帽牡蛎呼吸与排泄的周年变化

于2005年5月至2006年3月对浙江沿岸重要的3种经济贝类泥蚶、缢蛏和僧帽牡蛎的呼吸率与排泄率进行了周年研究。结果表明:泥蚶、缢蛏和僧帽牡蛎耗氧率的变化范围分别为0.11~5.05 mg/（g·h）、0.77~5.97 mg/（g·h）和0.33~5.47 mg/（g·h）,排氨率的变化范围分别为21.51~1 078.63 μg/（g·h）,26.97~990.73 μg/（g·h）和32.12~1 378.67 μg/（g·h）;耗氧率与排氨率9月份最高,1月份最低。经单因素方差分析发现,3种实验贝类月际间的耗氧率与排氨率均存在极显著差异（p<0.01）,经配对T检验发现,缢蛏（SC）和僧帽牡蛎（SCA）之间的耗氧率存在着显著差异T_（SC-SCA）=3.184,p=0.024）,泥蚶（TG）与缢蛏、僧帽牡蛎的耗氧率之间都不存在差异（T_（TG-SC）=1.887,p=0.118;T_（TG-SCA）=0.246,p=0.815）,泥蚶、缢蛏和僧帽牡蛎之间的排氨率的差异均不显著（T_（TG-SC）=0.977,p=0.373;T_（TG-SCA）=2.369,p=0.064;T_（SC-SCA）=1.002,p=0.362）。3种贝类的耗氧率与排氨率均随温度的升高而升高,经回归分析发现,耗氧率和排氨率与温度的变化均呈较显著的幂指数性相关lnY=lna+blnT（Y=aebT）。泥蚶呼吸排泄O:N变化范围为4.69~28.55,缢蛏和僧帽牡蛎的O:N变化范围分别为:4.68~37.89和3.04~10.27。     

一株海洋微型硅藻的形态学和分子生物学鉴定

1 引言 微型浮游植物(粒径为2～20μm)是海洋环境中主要的初级生产者,在海洋初级生产力中占有很大比重,特别在寡营养水域,微型浮游植物可占初级生产力的80%以上[1],并且在粒级结构上微型浮游植物对初级生产力的贡献要比较大粒级的植物的贡献更大[2].     

Accumulation of Cu and Zn in discarded antifouling paint particles by the marine gastropod, Littorina littorea

The short-term (5 day) accumulation of Cu and Zn in different tissues of the marine gastropod, Littorina littorea, has been studied in the presence of 10 mg l⁻¹ of antifouling paint particles and pre- or simultaneously contaminated algal food (Ulva lactuca). Accumulation of Cu was observed in the head–foot, digestive gland–gonad complex and gills to extents dependent on how and when food was contaminated and administered. However, retention of Zn was only observed in the gills and only when L. littorea and U. lactuca were simultaneously exposed to paint particles. Relative to the alga, faecal material was highly enriched in Zn, suggesting that the animal is able to rapidly eliminate this metal, most likely through the formation and egestion of insoluble phosphate granules. Thus, L. littorea is a useful biomonitor of marine contamination by antifouling applications in respect of Cu but not Zn.     

Hitching a ride on a hermit crabs home: Movement of gastropod shells inhabited by hermit crabs

There is little information on the movement and connectivity patterns for many species. The movement by shells occupied by the hermit crab Pagurus bernhardus and the organisms encrusting these shells was investigated on the south coast of Wales (UK). Hermit crabs shells moved considerable distances along the shore over 1 month periods, moving a minimum mean distance (±SE) of 148 (±8) and 174 (±9) m from release sites in the January and August respectively. Hermit crab-inhabited shells were also found to travel across habitats (sandy areas) that are unsuitable for both hermit crabs and epibionts. Through the examination of 150 of the most abundant shells used by P. bernhardus (Nucella lapillus), twelve epibiont species were found (10 animal and 2 algal species) and choice experiments demonstrated that hermit crabs preferred epibiont covered shells (84%), compared with bare shells (16%). The distance that shells were moved and the preference of hermit crabs for epibiont encrusted shells, coupled with the ability for epibionts to cross unsuitable habitats, may provide a dispersal advantage for epibiont species.     

Ecological understanding for fishery management: Condition and growth of anchovy late larvae during different seasons in the Northwestern Mediterranean

The fishery of the European anchovy Engraulis encrasicolus in the Mediterranean needs several ecological approaches to be properly managed. As such, several surveys were carried out to study the ecology of larvae and juveniles of this species, which reproduces during the warmest period of the year (May through September) in the Gulf of Lions. In particular, we studied the late larvae (15 mm total length until metamorphosis), especially as other authors have focused on larvae below that size. Unexpectedly, we also collected anchovy late larvae during the December 2007 survey, whose range in size corresponded to a later spawning period than previously reported. Differences in the nutritional condition of these larvae were assessed by comparing indices of lipid composition and estimating growth rates from otolith measurements to provide information on the probability of survival between the two groups. The analysis of fatty acids, used as tracers of trophic relationships, indicates that these larvae fed mainly on zooplankton. Nutritional conditions of summer and late autumn larvae were very similar. In contrast, growth rates were higher for August larvae, probably due to the different temperatures in the two seasons. Our results are especially relevant in an ecological context where the increasing mean water temperatures in the Western Mediterranean could favor the extension of the anchovy spawning period up to late-Autumn months.     

一株分离自胶州湾的裸甲藻形态相似种的分子系统学研究

对一株分离自胶州湾的裸甲藻形态相似种(Gymnodinium sp.ZX)进行了分子水平的分类鉴定.提取基因组DNA后扩增核糖体小亚基和转录间隔区序列,经纯化、克隆并测序.将获得的序列分别进行Blastn同源性分析,并下载相关序列构建系统进化树,结果表明,该藻与共生藻(Symbiodinium)亲缘关系较近,而与裸甲藻...     

Ontogenetic habitat use by mangrove/seagrass-associated coral reef fishes shows flexibility in time and space

Tropical shallow-water habitats such as mangroves and seagrass beds are widely acknowledged as important juvenile habitats for various coral reef fish species, most of which are commercially important to fisheries. Spatio-temporal variability in ontogenetic habitat use by fish among these tropical coastal ecosystems has rarely been investigated, yet there are sufficient reasons to believe that this plays an important role. In the present study, we test the spatio-temporal variability in patterns of ontogenetic habitat use by some mangrove/seagrass-associated coral reef fishes (Lethrinus harak, Lethrinus lentjan, Lutjanus fulviflamma and Siganus sutor). Abundances of these four species were investigated during two years in Tanzanian coastal waters, using underwater visual census in mangrove, seagrass, shallow and deep mudflat, and shallow and deep coral reef habitats. The study covered four distinct seasons of the year and was done at two spatially separated (>40 km) locations. Averaged across locations, seasons and years, juveniles (≤10 cm length) of the four study species had significantly higher relative densities in shallow-water (mangroves and seagrass beds) than in deep-water habitats (deep mudflats or coral reefs), whereas the opposite pattern was found for the adults (>15 cm). These findings suggest a strong and general pattern of ontogenetic habitat shifts from shallow- to deep-water habitats. However, specific habitat-use patterns of juveniles as well as adults differed significantly in time and space. Various species showed subtle to considerable flexibility in juvenile as well as adult habitat use across seasons, years, or at different locations. Furthermore, for some species the data suggest presence of ontogenetic habitat shifts at one location but lack thereof at the other location. In summary, ontogenetic habitat use needs to be considered at various spatial and temporal scales for the interpretation of habitat utilization by fish during different life stages. This is important for conservation and management of these habitats, as essential habitats or seasons may be ignored or over-emphasized with respect to their importance for fish during different parts of their life cycle.     

Long-term changes in the seasonality of selected diatoms related to grazers and environmental conditions

The decoupling of trophic interactions could be one of the severe consequences of climate warming in aquatic systems. The timing of phytoplankton blooms, in particular, can affect competition within the plankton community as well as food-web interactions with zooplankton and fish. Using long-term data from Helgoland Roads in the southern North Sea, we examine diatom seasonality, using three representative diatom species combined with environmental and copepod time series over the last four decades. The long-term annual abundances of Guinardia delicatula, Thalassionema nitzschioides and Odontella aurita exhibited interannual variations and dissimilar cyclic patterns during the time period under study (1962-2008). Of the three diatoms, G. delicatula showed a significant trend towards earlier bloom timings for 1962-2008 and a later decline of its abundance over time was found. Grazing and water transparency explained most of the bloom timing fluctuations of the diatoms considered. The annual timing of occurrences of each diatom species was correlated with their preceding concentrations. Earlier bloom timings occurred when autumn/winter concentrations were higher than average and later bloom timings occurred when autumn/winter concentrations were lower than average. Different environmental and predation variables related to the diatom bloom timings were found suggesting that climate warming might not affect the onset of the blooms of the three diatom species in the same manner. The results of the multiple linear regression analyses showed that the timings of decline of the three diatoms were mainly correlated with decreasing nutrient concentrations. Sunshine duration could prolong the duration of the blooms of T. nitzschioides and O. aurita provided that enough nutrients were available. In the case of G. delicatula, however, sunshine duration was negatively correlated with its end of the growth period. G. delicatula and T. nitzschioides showed later decreases in abundances under warmer spring and summer temperatures. Such species specific differences in the sensitivity to the forcing variables could lead to shifts in community structure and could ultimately have wider implications to the overall ecosystem health of the North Sea.     

真鲷、黑鲷及其杂交子代的染色体构成与AFLP分析

采用核型分析和AFLP技术对真鲷、黑鲷及其杂交子代进行遗传差异分析。结果显示真鲷、黑鲷和杂交子代均含有48条染色体,核型分别为2n=2st+46t,NF=48、2n=4m+4sm+2st+38t,NF=56和2n=30m+8sm+2st+8t=48,NF=86,杂交子代核型与其父、母本种均不一致。两对AFLP选扩引物组合在真鲷、黑鲷和杂交子代中共扩增到278个条带,其中黑鲷特异性条带93条、真鲷特异性条带108条;杂交子代中分别出现了21条父本种(黑鲷)特异条带和67条母本种(真鲷)特异条带,另出现了15条非双亲条带。杂交子代与真鲷、黑鲷的遗传相似系数和遗传距离分别为0.113、0.350和2.180、1.050,表明杂交子代总体上更偏向于母本种。染色体核型和AFLP条带分析结果表明真鲷(♀)×黑鲷(♂)所获得的杂交子代为含有48条染色体的异源二倍体,且父、母本遗传物质在杂交中发生了部分重组,杂交子代表现出一定的偏母系遗传特性。     

三角褐指藻与抑食金球藻的竞争及化感作用研究

为探明三角褐指藻（Phaeodactylum tricornutum）对抑食金球藻（Aureococcus anophagefferens）是否具有化感作用,本研究以三角褐指藻和抑食金球藻为实验材料,研究了抑食金球藻在单培养和共培养条件下的生长情况及三角褐指藻培养滤液对其生长和叶绿素荧光参数的影响。结果表明:三角褐指藻对抑食金球藻有明显的化感抑制作用。在单培养体系中,抑食金球藻的生长曲线可用逻辑斯谛增长模型拟合,随着起始密度的增加,环境容量（K）逐渐减小,而抑食金球藻的种群瞬间增长率（r）、进入拐点时间及稳定期细胞密度均较为接近;当三角褐指藻与抑食金球藻以不同起始密度比共同培养时,抑食金球藻的生长均受到了显著地抑制（P<0.05）,但其抑制作用并未与三角褐指藻的密度呈明显的线性关系;滤液培养实验发现,10 mL和15 mL三角褐指藻培养滤液的加入可对抑食金球藻的生长产生显著影响（P<0.05）,对其叶绿素荧光参数没有影响（P>0.05）,25 mL和35 mL三角褐指藻培养滤液的加入可对抑食金球藻的生长和叶绿素荧光参数均产生显著的抑制作用（P<0.05）,叶绿素荧光参数F_v/F_m、ΦPSⅡ、alpha的值降低,Ik的值增加,PSⅡ受到损害。     

福建沿海米氏凯伦藻赤潮对皱纹盘鲍鳃组织抗氧化酶活性的影响研究

本文初步研究了在较低赤潮密度(低于107个/m L)下,一株米氏凯伦藻(Karenia mikimotoi)对皱纹盘鲍(Haliotis discus hannai)鳃内几种抗氧化酶,如超氧化物歧化酶(Superoxide dismutase,SOD)、过氧化氢酶(Catalase,CAT)、谷胱甘肽过氧化物酶(Glutathione peroxidase,GSH-Px)的毒性效应,以期分析米氏凯伦藻对鲍鱼生命活动可能的胁迫方式。研究表明,米氏凯伦藻对SOD、CAT酶活性均造成不利影响,并未对GSH-Px酶造成不利影响,其酶活性显著高于对照组。米氏凯伦藻对SOD酶活性的影响表现为"先诱导后抑制"效应,24 h内,各处理组(0.1个/m L,0.5个/m L,1.0×104个/m L)中,酶活性急剧增高,分别是对照组的1.2,1.3,1.3倍,之后酶活性迅速下降,分别是对照组的77%,77%,73%。SOD能够清除机体体内多余的自由基,其活力变化反映了机体抵制自由基损伤能力已受到明显抑制。此外,米氏凯伦藻处理组中,CAT酶活性则处于"被抑制"状态,48 h内酶活性持续下降,分别降低至对照组的58%,51%,37%。CAT可以清除SOD歧化超氧阴离子自由基产生的H2O2,其活力的下降也可能造成机体内过氧化物的累积及氧化损伤。结果表明,即使未达到较高赤潮密度(不超过107个/m L)时,米氏凯伦藻短时间内仍可对鲍鱼鳃内关键抗氧化酶活性造成显著抑制效应,这极有可能导致鲍鱼机体抗氧化系统遭受严重损伤。     

Spatial variation patterns of subtidal seaweed assemblages along a subtropical oceanic archipelago: Thermal gradient vs herbivore pressure

The structure and composition of subtidal rocky seaweed assemblages were studied at 69 sites on the Canary Islands (northeastern Atlantic). This group of islands are situated at the southern boundary of the warm temperate region and adjacent to the cold waters from the northwest African coastal upwelling, which creates a difference of almost 2 °C in surface seawater temperature from the eastern to the western islands. This thermal variation allows an examination of the transition between the warm temperate and the tropical regions along this longitudinal gradient together with the hypothesised Fucales-dominated assemblages towards the eastern islands in contrast to the Dictyotales-dominated assemblages towards the western ones. Environmental and biological parameters were considered in order to investigate which were the main factors explaining spatial variation along the gradient in a multi-scaled approach. Although seventy-nine macroalgae were identified, 87.63% of the total mean cover was due to six taxa (Lobophora variegata, nongeniculate corallines, Canistrocarpus cervicornis, Jania adhaerens, Cystoseira abies-marina and Pseudolithoderma adriaticum). At a large scale, sea urchin density explained the highest variation in seaweed assemblages (26.94%), and its pattern of distribution across the islands. The expected pattern of distribution according to the upwelling distance only occurred in restricted areas of the Canarian Archipelago in absence of herbivore pressure and habitat degradation. Spatial variations within islands (medium scale) were mainly related to wave exposure, while at a small scale these were mostly due to the degree of sedimentation.