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1.
Abstract. Hermit crab shells are often encrusted with diverse communities of epibionts. To explore the effects of hermit crabs on the interactions of these encrusting species, two species of hydractiniid hydroids, Hydractinia symbiolongicarpus and Podocoryna carnea , were examined in the presence and absence of Pagurus longicarpus hermit crabs. Colonies growing on Littorina littorea snail shells with hermit crab hosts were compared to those growing on shells without crabs. These experiments suggest that hermit crabs variably affect colony polyp number, colony morphology and the outcome of interspecific competition, according to the size and number of crabs; other factors include water temperature, food availability and hydroid clonal genotype. In order to allow image analysis of perturbations of colony morphology, hydroids were grown on glass surfaces both exposed and unexposed to hermit crabs. Relative to colonies growing on unexposed surfaces, colonies growing on exposed surfaces exhibited larger within-colony patches, thus decreasing the total encrusted surface area and polyp number of colonies. Further, on glass surfaces, hermit crabs accelerated the time to the resolution of interspecific competition ( i.e. , the overgrowth of one colony by the other). While a number of factors may contribute to the relative abundance of these encrusting species, under most circumstances P. longicarpus have large effects on hydractiniid hydroids. Mechanisms underlying these effects likely include hydrodynamics and mechanical disturbance. 相似文献
2.
This study investigates the size, age and growth of Corallium rubrum which is a key species of the only large reef-like structure in the Mediterranean Sea, the coralligéne. Two populations were studied in the Ligurian Sea at a depth between 36 and 42 m. Basal diameter, colony height and numbers of branches of 230 colonies were measured, and age and growth rates were assessed from 25 colonies. Mean growth rate was 0.2 mm yr−1 of basal diameter growth, corresponding to a mean annual total branch length increase of 5 mm. These results point to a coral growth much slower than assumed in many earlier studies. Additionally, age and size at first reproduction were analysed. Male colonies were shown to become sexually mature at a minimum age of six years (1.2 mm of basal diameter), while female colonies reached maturity when at least 10 years old (2 mm of basal diameter). We further discuss the implications of slow growth and early sexual maturity for red coral management and conservation. 相似文献
3.
Janie L. Wulff 《Marine Ecology》2008,29(2):193-204
Caribbean sponge species typical of coral reefs are generally inhibited from living in seagrass meadows by their vulnerability to predation by the large starfish Oreaster reticulatus (Linnaeus 1758). Although readily consumed by Oreaster , the conspicuous coral reef sponge species Lissodendoryx colombiensis Zea & van Soest, 1986 has expanded its habitat distribution to include a seagrass ( Thalassia testudinum Banks ex König, 1805) meadow in Belize, where individuals grow to volumes of nearly 7 l. By simple observation, L. colombiensis appears to be an inferior competitor in this system, because portions of many individuals are overgrown by seagrass sponge species. However, experimentally clustering seagrass sponges around L. colombiensis individuals deterred starfish from feeding on them, suggesting an advantage to being overgrown. Sizes of individual L. colombiensis can fluctuate widely over short time intervals, reflecting both a relatively fast growth rate and the high rate at which starfish consume this species. At the population level these fluctuations are not evident, as losses of L. colombiensis due to Oreaster are balanced by a combination of efficient recruitment, rapid regeneration and growth, and protection of portions of many individuals by the overgrowth of seagrass sponge species that are unpalatable to Oreaster . In turn, the seagrass sponges acquire stable perches on L. colombiensis individuals in this sediment-dominated habitat. Community ecology theory relating to diversity patterns in sessile organisms has focused on competition between space-requiring neighbors as the underlying process that inevitably decreases diversity unless curtailed. Sponges, with their propensity for engaging in beneficial interactions with neighbors, demand expansion of the theory to acknowledge how collaboration can increase abundance and species diversity within a community. 相似文献
4.
Deep-sea ecosystems are fragile yet diverse habitats that are sensitive to disturbance. In the northern Gulf of Mexico deepwater extraction of hydrocarbons led to the accidental release of four million barrels of oil from the Macondo wellhead in 2010. The release of oil combined with the addition of dispersant at depth and the resulting delivery of oiled “marine snow” led to dramatic disruptions of diversity and ecosystem services within the near field deep-sea benthic communities. Analysis of the biological trait diversity of the surrounding megabenthos reveals notable loss of traits that may explain the stunted recovery of communities within 2 km of the wellhead. The present megafauna show complete loss of some traits relating to tier, motility, and feeding mechanisms. Functional evenness was higher than in surveyed unaffected sites, highlighting some loss of trait space, reflecting increasing abundances of scavengers and the loss of sessile invertebrates. Loss of biological traits that aid in ecosystem resilience has impeded recovery of benthic communities severely impacted by the Deepwater Horizon oil spill. 相似文献
5.
通过对13种藻不同组合后的集群进行室内一次性培养实验,探讨了浮游植物不同组合集群中物种丰富度及物种组成对其生物量及指数生长期比生长率的影响。实验结果表明,物种组成与物种丰富度均对集群生物量有一定的影响,其中物种组成的影响更大;且物种丰富度与生物量不具有线性相关性。随着物种丰富度增大,集群在指数生长期的比生长率有增加趋势。在本实验设定的营养盐条件下,营养盐水平高低对集群指数生长期的比生长率影响较小,但其对指数生长期的持续时间影响较大,进而对集群生物量产生影响。 相似文献
6.
João Canning-Clode Manfred Kaufmann Markus Molis Martin Wahl & Mark Lenz 《Marine Ecology》2008,29(1):115-124
Disturbance and productivity are often cited as the main factors determining temporal and spatial patterns in species distribution and the diversity of communities. A field experiment was conducted to test the role of these factors in the structuring of early successional fouling communities in a nutrient limited system at the south coast of Madeira Island. Macro‐benthic sessile communities, established on artificial settlement substrata, were manipulated and surveyed over a 9‐week period. We applied mechanical disturbances of four different frequencies crossed with three levels of inorganic nutrient enrichment. Fertilization enhanced community diversity by favouring the establishment and growth of macroalgae. Disturbance reduced diversity by eliminating species – but only at the highest nutrient level. This is explained by a multiple‐stressor model; species most sensitive to nutrient deficiency (only present in the highest enrichment treatment) were simultaneously the most sensitive to disturbance. 相似文献
7.
Sponges Inhabiting a Mediterranean Red Coral Population 总被引：2，自引：0，他引：2
Abstract. A coastal red coral [Corallium rubrum (L.)] population, whose age structure and demographic parameters have been previously analysed, harbours 10 species of endobiotic sponges. This sponge assemblage differs considerably from that inhabiting other calcareous substrata of the surrounding area, suggesting some selectivity for red coral. The two most common endobiotic species, Spiroxya heteroclita T opsent and Cliona sarai M elone , are described in detail. The percentage of infested coral colonies increases according with colony age, with a sharp increment at four years. An increase in coral colony mortality observed at this age may be related to the increment of endobiotic sponge infestation. 相似文献
8.
9.
《African Journal of Marine Science》2013,35(1):111-119
This paper reports on growth of the Boulders colony of African penguins Spheniscus demersus from inception in 1985 to the present. More than 900 pairs now breed there. Growth of the colony slowed in 1995 and 1996 and reversed in 1998, coinciding with periods of low abundance of Cape anchovy Engraulis capensis off South Africa. In December 1996, penguins were excluded from a portion of land where they had formerly bred. They responded by increasing the density of their nests in other areas and expanding their area of breeding longshore. These patterns indicate that food and not space are currently controlling colony growth rate. Much of the colony growth probably results from immigration of first-time breeders from other colonies. Of immigrants, 70–80% may be from Dyer Island to the south-east, where numbers of penguins have decreased. Boulders also is frequently visited by penguins from other colonies, and by rehabilitated birds. 相似文献
10.
《African Journal of Marine Science》2013,35(3-4):697-704
From 1987 to 2005, numbers of African penguins Spheniscus demersus breeding in South Africa's Western Cape Province increased by about 50%. Numbers decreased at the four northernmost colonies in the region: Lambert's Bay and the three colonies in Saldanha Bay, although at Jutten Island the decrease is inferred from an estimate for 1987, derived from interpolation. Numbers also decreased at Geyser Rock and Dyer Island on the South Coast. At five colonies between Saldanha Bay and Dyer Island there were large increases. At a sixth colony in that region, Seal Island, where Cape fur seals Arctocephalus pusillus pusillus limit breeding space, numbers remained stable. At two colonies that were initiated in the early 1980s, Robben Island and Boulders, increases were initially rapid (>20% per annum) and matched growth of the South African stock of sardine Sardinops sagax. Strong growth at Dassen and Vondeling islands, between Robben Island and Saldanha Bay, was observed from about 1996–2002, when there was a large increase in the biomass of pelagic fish off South Africa. Increases at colonies between Saldanha Bay and Boulders slowed after 2002, whereas the colony at Dyer Island stabilised at that time. In 2003, a new colony was initiated east of Dyer Island at De Hoop Nature Reserve. These latter trends followed an eastward shift in the distribution of sardine. Small penguin colonies may act as foci for growth in a period when the distribution of prey is changing. Hence, it is important that they be maintained, especially those that, if lost, would increase the isolation of regional populations. Some of the small colonies are less susceptible to oil spills than colonies in the proximity of harbours, and for that reason also are important. 相似文献
11.
Acropora coral colonies as microhabitats for sponges in Tayrona National Natural Park,Colombian Caribbean 
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下载免费PDF全文 Sponges are sessile organisms capable of colonizing diverse substrata. In the Caribbean, coral reefs have suffered a drastic decline, and branching corals of the genus Acropora have been widely decimated. On dead coral skeletons and around surviving tissue the settling of sessile organisms can be observed, sponges being common. In order to investigate whether or not sponges have a preference for a particular species of coral, or for specific microhabitats of the colonies, we evaluated species composition, cover, richness and diversity of sponges colonizing the dead parts of still live colonies of the branching corals Acropora palmata and Acropora cervicornis in five locations of the Tayrona National Natural Park in the Colombian Caribbean. Ten colonies of Ac. palmata were quantified in each of the five locations, and eight Ac. cervicornis colonies in each of two locations. Quantification was carried out using video taken within 0.625‐m2 photoquadrats. Seventeen sponge species were found, 13 of them associated with Ac. palmata and seven with Ac. cervicornis. Desmapsamma anchorata, Clathria venosa and Scopalina rutzleri were found to be common to all Ac. palmata locations, while De. anchorata occurred in the two Ac. cervicornis locations. On Ac. palmata, encrusting sponges dominated, while on Ac. cervicornis branched and lobed sponges predominated. Significant differences in sponge cover were not found among locations but were observed in the sponge species present. On Ac. palmata the species with highest cover were D. anchorata and Cla. venosa, while on Ac. cervicornis it was De. anchorata. The richness and diversity of sponges were low for both coral species, and their varying distribution can be attributed to the differences in available substrate for attachment, given coral colony morphology; for Ac. palmata, sponges predominated on the underside of the branches, semi‐cryptic areas and colony bases, whereas for Ac. cervicornis, they were located over the entire area of the cylindrical branches. Surviving colonies of Ac. palmata and Ac. cervicornis that are still erect offer additional microhabitats for reef sponges, some of which can be found directly interacting with live coral tissue, further threatening their recovery. 相似文献
12.
Abstract. Cladocora caespitosa is a relatively common, colonial, symbiotic, scleractinian coral in the Mediterranean Sea. It inhabits a wide ecological range: hard and soft bottoms, shallow waters or depths to about 50m, calm water or sites exposed to strong currents and wave action. The present study compares the distribution of this coral at two sites, one shallow (3m — wave exposed) and one deeper (12m — soft bottom).
Different parameters including dry weight, volume, and skeletal growth rates were investigated. The polyp biomass, carbon content, and overall area of fully expanded polyps were also measured. Equations are given for the relationship of skeleton diameter to polyp tissue dry weight as well as skeleton diameter to the possible filter area of fully expanded polyps.
C. caespitosa harbors a rich community of vagile and sessile organisms within the skeleton. The cryptofauna was sorted to higher taxonomic levels and their biomass determined. Several highly significant linear relationship were found between skeleton dry weight, volume and cryptofauna biomass. Thus, the determination of colony volume allows the prediction of cryptofauna biomass.
The interstitial space is dominated by sponges - many of them borers - which erode the corallites close to the living tissue until they break off from the colony. At the deeper sampling site, 26% of all colonies are smaller than 2 cm and 48% are smaller than 5 cm. The fragmentation process is discussed with respect to reproduction. 相似文献
Different parameters including dry weight, volume, and skeletal growth rates were investigated. The polyp biomass, carbon content, and overall area of fully expanded polyps were also measured. Equations are given for the relationship of skeleton diameter to polyp tissue dry weight as well as skeleton diameter to the possible filter area of fully expanded polyps.
C. caespitosa harbors a rich community of vagile and sessile organisms within the skeleton. The cryptofauna was sorted to higher taxonomic levels and their biomass determined. Several highly significant linear relationship were found between skeleton dry weight, volume and cryptofauna biomass. Thus, the determination of colony volume allows the prediction of cryptofauna biomass.
The interstitial space is dominated by sponges - many of them borers - which erode the corallites close to the living tissue until they break off from the colony. At the deeper sampling site, 26% of all colonies are smaller than 2 cm and 48% are smaller than 5 cm. The fragmentation process is discussed with respect to reproduction. 相似文献
13.
MW Farthing AC Winkler K Anderson S Kerwath C Wilke WM Potts 《African Journal of Marine Science》2018,40(2):187-196
The hottentot seabream Pachymetopon blochii is a small-sized (maximum 2.67 kg) sparid endemic to southern Africa. It is an important target in South Africa's Western Cape traditional linefishery, particularly in the absence of more valuable pelagic species (such as Thyrsites atun and Seriola lalandi). In 2000, South Africa's linefishery was declared to be in a state of emergency, and commercial fishing effort was consequently reduced by 70%. A subsequent increase in stock biomass and intraspecific competition, coupled with environmental changes, were hypothesised to have thereafter altered the growth rate of hottentot, from 2000 to 2010. This study aimed to revise outdated age–growth models for the hottentot by using modern techniques (sectioned otoliths), and to compare age–growth relationships before and after the declared linefish state of emergency. The maximum age observed was 19 years, with no difference in the growth rate between sexes (p = 0.39–0.43) or time-periods (p = 0.96). Although the growth rate did not change, there is evidence that the age structure of the stock changed between time-periods as a result of changes in fishing pressure between 2000 and 2010. The enhanced recent growth model for hottentot, described as Lt = 418.063 (1 – e?0.104(t – [?4.709])) (pooled sexes; n = 206), indicates a considerably slower growth rate for this species than was proposed previously using whole otoliths and has major implications for effective stock management. 相似文献
14.
Abstract. The dependence of the vertical distribution of sessile macrobenthos upon environmental physical factors was studied in a community inhabiting rocky substrata at 2 to 15 m depth near the Rimsky‐Korsakov Islands (Peter the Great Bay, Sea of Japan). Three separate groups of species were distinguished within this community. The main dominant species are the anthozoan Metridium senile and the mussel Crenomytilus grayanus. Water movement, bottom inclination and topographic position of the studied sites in respect to prevailing water flows influence the spatial structure of sessile invertebrates. No vertical zonation in the scale of the studied sublittoral area below the 2 m depth level was observed. The studied factors are believed to condition the observed mosaic of patches characterized by specific composition, with a single species being dominant. 相似文献
15.
Abstract. .The phosphate uptake kinetics of single cells and colonies of the haptophycean alga Phaeocystis pouchetii were investigated in short- and long-term experiments. In phosphate-deprived cultures, the highest nutrient uptake rate (Vmax ) of both growth forms appeared to be similar. However, the half-saturation constant for phosphate uptake of the cells embedded in a colony (Ks = 3.08 μM) was considerably higher than that of the single cells (Ks = 0.31 μM). This is consistent with the existence of a diffusion barrier formed by the colony membrane and colonial mucus. Over a 24 h light/dark cycle, the phosphate assimilation rate in moderately limited colonies and single cells was nearly identical during the light period. In the following dark phase, colony cells maintained this uptake rate, whereas the uptake of the single cells diminished by 70 %. The high dark uptake rate in colonies ran parallel with the absorption and degradation of intracolonial carbon compounds, suggesting that the dissimilation of these compounds covers the energy requirements for phosphate uptake in the dark. In Phaeocystis cultures during a transition to phosphate depletion, a significant amount of phosphate was found in the colonial mucus, isolated by selective filtration. The possible absorption of phosphate by the mucus and the role of mucus in the energy budget seem to be an essential feature of phosphate uptake of colonies. Short-term measurement of phosphate uptake in colony cells may therefore underestimate the phosphate uptake of the whole colony. 相似文献
16.
Using industry inspection video and ROV imaging, we examined Lophelia pertusa (Linnaeus 1758) on 10 artificial structures of known ages (9 to 100 years) in the northern Gulf of Mexico (GoM). Five different types deep-water energy installations with depths ranging from 320 to 995 m, and three shipwrecks with depths ranging from approximately 530 to 615 m, were examined. Density, depth ranges, and growth rates of L. pertusa colonies were calculated from video and image analysis. L. pertusa colonies were present on all structures examined. Minimum calculated growth rates for the largest colonies ranged from 0.32 to 3.23 cm/yr on the different structures. The shallowest depth at which L. pertusa was observed was 201 m and the deepest was 801 m, considerably expanding the known depth range of this species in the northern GoM. Colony density varied with structure type, age, and depth, with the highest density between 503 and 518 m on the single structure that spanned the entire depth range of occurrence of L. pertusa observed in this study. L. pertusa colonies growing on thinner and deeper installations appear to have higher colonization rates, i.e. to develop higher densities over a shorter time period, compared to those on shallower and more massive types of installations. However, on average, colonies have slower growth rates on these installations than colonies on more massive, shallower installations (compliant and solid installations). In general, the calculated minimum growth rates were higher on the installations than on the shipwrecks, which were substantially older. A continuum of colony sizes was documented on all installations, suggesting multiple settlement events. L. pertusa thickets were observed on the oldest anthropogenic structures, with most of the components of these structures covered by colonies of L. pertusa. Brown, orange, and mottled color-variants were documented for the first time in the GoM. All installations examined for this study were colonized by L. pertusa and it is likely that most artificial surfaces in appropriate depths in the GoM will be as well. 相似文献
17.
球形棕囊藻具有异型的生活史,能够在单细胞和囊体两种不同形态之间转换。球形棕囊藻藻华现场发现,囊体有时附着在角毛藻上。为研究角毛藻对囊体形成的影响和机制,进行球形棕囊藻和小角毛藻的共培养实验,观察球形棕囊藻囊体的形成和生长状况,研究小角毛藻对球形棕囊藻囊体形成的影响。结果证明:混合培养下,小角毛藻和球形棕囊藻的囊体附着在一起,在较短的生存周期内,囊体的密度明显高于单独培养时的密度;而单独培养体系下,棕囊藻单细胞密度和囊体体积均高于混合培养,囊体的存在时间较长。小角毛藻的存在对囊体的形成具有促进效应,这对于球形棕囊藻囊体具有重要的生态意义。硅藻的存在更能体现球形棕囊藻竞争优势。 相似文献
18.
Arthur C. R. Gleason Diego Lirman Dana Williams Nuno R. Gracias Brooke E. Gintert Hossein Madjidi R. Pamela Reid G. Chris Boynton Shahriar Negahdaripour Margaret Miller & Philip Kramer 《Marine Ecology》2007,28(2):254-258
Four hurricanes impacted the reefs of Florida in 2005. In this study, we evaluate the combined impacts of hurricanes Dennis, Katrina, Rita, and Wilma on a population of Acropora palmata using a newly developed video‐mosaic methodology that provides a high‐resolution, spatially accurate landscape view of the reef benthos. Storm damage to A. palmata was surprisingly limited; only 2 out of 19 colonies were removed from the study plot at Molasses Reef. The net tissue losses for those colonies that remained were only 10% and mean diameter of colonies decreased slightly from 88.4 to 79.6 cm. In contrast, the damage to the reef framework was more severe, and a large section (6 m in diameter) was dislodged, overturned, and transported to the bottom of the reef spur. The data presented here show that two‐dimensional video‐mosaic technology is well‐suited to assess the impacts of physical disturbance on coral reefs and can be used to complement existing survey methodologies. 相似文献
19.
Heather Sugden Rafael Panusch Mark Lenz Martin Wahl & Jeremy C. Thomason 《Marine Ecology》2007,28(3):368-376
Natural communities are constantly changing due to a variety of interacting external processes and the temporal occurrence and intensity of these processes can have important implications for the diversity and structure of marine sessile assemblages. In this study, we investigated the effects of temporal variation in a disturbance regime, as well as the specific timing of events within different regimes, on the composition and diversity of marine subtidal fouling assemblages. We did this in a multi‐factorial experiment using artificial settlement tiles deployed at two sites on the North East coast of England. We found that although there were significant effects of disturbances on the composition of assemblages, there were no effects of either the variation in the disturbance regime or the specific timing of events on the diversity or assemblage composition at either site. In contrast to recent implications we conclude that in marine fouling assemblages, the variability in disturbance regimes (as a driving force) is unimportant, while disturbance itself is an important force for structuring robust ecosystems. 相似文献
20.
Sexual reproduction and early life‐history traits of the Mediterranean soft coral Alcyonium acaule 下载免费PDF全文
下载免费PDF全文 Núria Teixidó Nathaniel Bensoussan Andrea Gori Ida Fiorillo Núria Viladrich 《Marine Ecology》2016,37(1):134-144
Understanding processes that contribute to a better comprehension of the population dynamics of long‐lived species is critical for the maintenance and potential recovery of such species. Despite the abundance of soft corals in Mediterranean rocky reefs, little information exists on their life histories and reproductive patterns. In this study, we assessed the main reproductive characteristics and early life‐history traits of the long‐lived soft coral Alcyonium acaule. The sex ratio was 1:1; the smallest fertile colonies were one finger in size (2.1 ± 0.6 cm in height), and both colony and polyp fertility increased with colony size. Likewise, the number of eggs and spermary sacs per polyp increased significantly with colony size, whereas the diameter of the female and male sexual products did not. Over 6 years of observations (2007–2012), spawning occurred primarily in July, after the seawater reached 20 °C, in a single spawning episode per year. Approximately 80% of female colonies released eggs, which were retained on the surface of the mother colony by mucous strings for up to a few days. High fertilization rates were observed during spawning in 2008 and 2009 (94.9% and 87.0%, respectively). The timing of development was ~24 h for the blastulae, ~48–72 h for the planulae and 8–22 days for metamorphosis into primary polyps. Survivorship of planulae was relatively high (~50% at 45 days after release), but only 24% of larvae metamorphosed into primary polyps, and their survivorship was moderate after 2 months (65% in 2008 and 74% in 2009). Asexual reproduction was negligible, indicating that sexual reproduction is the main mechanism supporting the maintenance and recovery of populations. 相似文献