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1.
Encrusting calcareous organisms such as bryozoans, crustose coralline algae (CCA), foraminiferans, and serpulid worms are
integral components of tropical framework-building reefs. They can contribute calcium carbonate to the reef framework, stabilise
the substrate, and promote larval recruitment of other framework-building species (e.g. coral recruits). The percentage cover
of encrusting organisms and their rates of carbonate production (g m −2 year −1) were assessed at four sites within a coastal embayment, along a gradient of riverine influence (high-low). As the orientation
and type of substrate is thought to influence recruitment of encrusting organisms, organisms recruiting to both natural (the
underside of platy corals) and experimental substrates were assessed. The effect of substrate exposure under different levels
of riverine influence was assessed by orientating experimental substrates to mimic cryptic and exposed reef habitats (downwards-facing
vs upwards-facing tiles) at each site. Cryptic experimental tiles supported similar encruster assemblages to those recruiting
to the underneath (cryptic side) of platy corals, suggesting that tiles can be used as an experimental substrate to assess
encruster recruitment in reef systems. Encruster cover, in particular CCA, and carbonate production was significantly higher
at low-impact (clear water), high wave energy sites when compared to highly riverine impacted (turbid water), low wave energy
sites. Cryptically orientated substrates supported a greater diversity of encrusting organisms, in particular serpulid worms
and bryozoans. The inverse relationships observed between riverine inputs and encrusters (total encruster cover and carbonate
production) have implications for both the current and future rates and styles of reefal framework production. 相似文献
2.
Summary Givetian to early Carboniferous sediments of South China are characterized by carbonates. Middle and Late Devonian strata
are best developed in the Guilin area. Reefs and organic shoals are recorded by various lithofacies types indicating the existence
of an extended carbonate platform and a change of the composition of reef communities in time. Starting in the late Devonian,
stromatoporoids and corals were replaced by algae that subsequently played an important role together with stromatoporoids,
receptaculitids and fasciculate rugose corals in reef communities. In Houshan, 5 km west of Guilin, a coral-bafflestone reef
occurs in the Frasnian strata, situated near an offshore algal-stromatoporoid reef. The coral reef was formed in a back-reef
area adjacent to the inner platform margin. The coral-bafflestone reef is unique among the late Devonian reefs of South China
with regard to the biotic composition. The reef is composed of fasciculate colonies of Smithiphyllum guilinense n. sp. embedded within in packstones and wackestones. The height of colonies reaches 1 m. The community is low-diverse. The
species of Smithiphyllum occurring in the Frasnian reef complexes of Guilin exhibit a distinct facies control: Smithiphyllum guilinense occurs in or near to margin facies and formed bafflestone, constituting a coral reef whereas Smithiphyllum occidentale
Sorauf, 1972 and Smithiphyllum sp.—characterized by small colonies with thin corallites—are restricted to the back-reef and marginal slope facies. The bush-like
coral colonies baffled sediments. Algae and stromatoporoids (mainly Stachyodes) are other reef biota. Reef-dwelling organisms are dominated by brachiopods.
The reefs are composed from base to top of five lithofacies types: 1) cryptalgal micrite, 2) peloidal packstone, 3) stromatactis
limestone, 4) coral-bafflestone, and 5) pseudopeloidal packstone. The reef complex can be subdivided into back-reef subfacies,
reef flat and marginal subfacies, and marginal fore-slope subfacies. The Houshan coral-bafflestone reef is not a barrier reef
but a coral patch reef located near the inner margin of a carbonate platform. 相似文献
3.
Summary The Carboniferous-Permian (Visean-Midian) Omi Limestone in the Akiyoshi Terrane, central Japan is a large carbonate unit developed
on a seamount in the Panthalassa Ocean. As the seamount subsided during Carboniferous and Permian time, the carbonate deposition
at the top of a seamount was almost continous. Terrigenous siliciclastic sediments are absent, because the seamount was situated
in an open-ocean setting. The lower part of this seamount-type limestone records a nearly continuous Carboniferous reef succession.
Sedimentary facies in the Carboniferous part of the Omi Limestone are generally highly diverse, but their diversity varies
in each age. The Upper Carboniferous part consists of highly diversified facies including fore reef, reef front, reef crest,
sand shoal, and lagoon facies, while a simple facies assemblage, composed only of fore reef, reef front, and sand shoal facies,
occurs in the Lower Carboniferous.
The Carboniferous reef succession consists of four phases characterized, in ascending order, by the coralbryozoan-crinoid
community, problematic skeletal organism-microencruster community, chaetetid-microencruster community, and calcareous algal
community. The first phase, comprising the coral-bryozoan-crinoid community, occurs in the Endothyra spp. Zone to the Eostaffella kanmerai Zone (Visean to Serpukhovian). This community acted only as sediment-bafflers and/or contributors. The second phase, represented
by the problematic skeletal organism-microencruster community, is developed in the Millerella sp. Zone to the Akiyoshiella ozawai Zone (Bashkirian to lowermost Moscovian), and the third phase, comprising the chaetetid-microencruster community, occurs
in the overlying Fusulinella biconica Zone (Lower Moscovian). These two communities are characterized by highly diversified reef-building organisms that had the
ability to build rigid frameworks. Calcareous algae and incertae sedis such as Hikorocodium, solenoporaceans and phylloid algae characterize the fourth phase, which occurs in the Beedeina sp. Zone (Upper Moscovian). The changes of the reef communities were sucessive for a long period of more than 40 m.y., and
each community was distributed in various environments. In addition, the continuous subsidence of the isolated seamount resulted
in environmental stability. These properties indicate that this succession represents the biotic evolution of reef-building
organisms.
The problematic skeletal organism-microencruster community and chaetetid-microencruster community of the Late Carboniferous
formed wave-resistant and rigid frameworks along with abundant submarine cements. The growth of these reef frameworks resulted
in the formation of highly diversified sedimentary facies comparable to those of a modern reef complex. Such reefs are also
recognized in the seamount-type Akiyoshi Limestone, but rare on Carboniferous Pangean shelves. Therefore, the formation of
these types of reefs appear to be characteristic of open-ocean seamount settings, which differed from epicontinental shelf
settings in having no siliciclastic input, being exposed to relatively strong openocean waves and swells, and probably more
environmental stability resulting from the relatively continuous subsidence of the seamount. 相似文献
4.
Many coral reef ecosystems experience shifts in benthic community composition from scleractinian corals to algae. However,
consequences of such phase shifts on O 2 availability, important for many reef organisms, are unresolved. This study therefore comparatively investigated potential
in situ effects of different benthic cover by reef macroalgae and scleractinian corals on water column O 2 concentrations in a Northern Red Sea fringing reef. Findings revealed that mean daily O 2 concentrations at algae-dominated sites were significantly lower compared to coral-dominated sites. Minimum O 2 concentrations were significantly negatively correlated, while diurnal variability in O 2 concentration was significantly positively correlated, with increasing benthic cover by algae. In contrast, no correlation
with coral cover was found. These results indicate that shifts from corals to benthic algae may likely affect both in situ
O 2 availability and variability. This may be particularly pronounced in reef systems with low water exchange (e.g. closed lagoons)
or under calm weather conditions and suggests potential O 2-mediated effects on reef organisms. 相似文献
5.
The effects of substratum on the growth of Terpios was demonstrated using experimental and observational data at Guam, Mariana Islands. Terpios growth was measured on live coral, reef rock, and red calcareous algae in the field. In addition, Terpios was transplanted onto live coral, air-blasted (clean) coral, reef rock, and plexiglass plates, and subsequent growth measured. Terpios grows fastest on clean substrata followed by live coral, reef rock and red calcareous algae in decreasing order. Terpios is sometimes overgrown by Montipora, Porites and red calcareous algae. Since Terpios grows fastest when living coral tissue is removed, it is not likely that Terpios ingests coral tissue as previously suggested in the literature. Instead, Terpios is probably an efficient competitor of corals for space. Terpios overgrows most hard, stable reef substrata, and the growth rate on all sample substrata is substantial. Therefore Terpios has a great potential for covering a reef and may be one of the most important causes of disturbance on some coral reefs.Contribution no. 206 from the University of Guam Marine Laboratory 相似文献
6.
The existence of coral reef ecosystems critically relies on the reef carbonate framework produced by scleractinian corals and calcareous crusts (i.e., crustose coralline algae). While the Red Sea harbors one of the longest connected reef systems in the world, detailed calcification data are only available from the northernmost part. To fill this knowledge gap, we measured in situ calcification rates of primary and secondary reef builders in the central Red Sea. We collected data on the major habitat-forming coral genera Porites, Acropora, and Pocillopora and also on calcareous crusts (CC) in a spatio-seasonal framework. The scope of the study comprised sheltered and exposed sites of three reefs along a cross-shelf gradient and over four seasons of the year. Calcification of all coral genera was consistent across the shelf and highest in spring. In addition, Pocillopora showed increased calcification at exposed reef sites. In contrast, CC calcification increased from nearshore, sheltered to offshore, exposed reef sites, but also varied over seasons. Comparing our data to other reef locations, calcification in the Red Sea was in the range of data collected from reefs in the Caribbean and Indo-Pacific; however, Acropora calcification estimates were at the lower end of worldwide rates. Our study shows that the increasing coral cover from nearshore to offshore environments aligned with CC calcification but not coral calcification, highlighting the potentially important role of CC in structuring reef cover and habitats. While coral calcification maxima have been typically observed during summer in many reef locations worldwide, calcification maxima during spring in the central Red Sea indicate that summer temperatures exceed the optima of reef calcifiers in this region. This study provides a foundation for comparative efforts and sets a baseline to quantify impact of future environmental change in the central Red Sea. 相似文献
7.
Effective identification and mapping of coral reef benthic communities using high-spatial and -spectral resolution digital
imaging spectrometry requires that the different communities are distinguishable by their spectral reflectance characteristics.
In Kaneohe Bay, Oahu, Hawaii, USA, we collected in situ a total of 247 spectral reflectances of three coral species ( Montipora capitata, Porites compressa, Porites lobata), five algal species ( Dictyosphaeria cavernosa, Gracilaria salicornia, Halimeda sp., Porolithon sp., Sargassum echinocarpum) and three sand benthic communities (fine-grained carbonate sand, sand mixed with coral rubble, coral rubble). Major reflectance
features were identified by peaks in fourth derivative reflectance spectra of coral (at 573, 604, 652, 675 nm), algae (at
556, 601, 649 nm) and sand (at 416, 448, 585, 652, 696 nm). Stepwise wavelength selection and linear discriminant function
analysis revealed that spectral separation of the communities is possible with as few as four non-contiguous wavebands. These
linear discriminant functions were applied to an airborne hyperspectral image of a patch reef in Kaneohe Bay. The results
demonstrate the ability of spectral reflectance characteristics, determined in situ, to discriminate the three basic benthic
community types: coral, algae and sand.
Accepted: 12 January 2000 相似文献
8.
Summary The roles of Permian colonial corals in forming organic reefs have not been adequately assessed, although they are common
fossils in the Permian strata. It is now known that colonial corals were important contributors to reef framework during the
middle and late Permian such as those in South China, northeast Japan, Oman and Thailand. A coral reef occurs in Kanjia-ping,
Cili County, Hunan, South China. It is formed by erect and unscathed colonies of Waagenophyllum growing on top of one another in situ to form a baffle and framework. Paleontological data of the Cili coral reef indicates a middle to late Changhsing age (Late
Permian), corresponding to the Palaeofusulina zone. The coral reef exposure extends along the inner platform margin striking in E-S direction for nearly 4 km laterally
and generally 35 to 57 m thick. The Cili coral reef exhibits a lateral differentiation into three main reef facies; reef core
facies, fore-reef facies, and marginal slope facies. The major reef-core facies is well exposed in Shenxian-wan and Guanyin-an
sections where it rests on the marginal slope facies. Colonial corals are dispersed and preserved in non-living position easward.
Sponges become major stabilizing organisms in the eastern part of Changhsing limestone outcrop in Kanjia-ping, but no read
sponge reefs were formed. Coral reefs at Cili County in Human are different distinctly from calcisponge reefs in South China
in their palaeogeography, lithofacies development, organic constitutuents, palaeoecology and diagenesis. The Cili coral reef
also shows differences in age, depositional facies association, reef organisms and diagenesis from coral reefs in South Kitakami
of Japan, Khorat Plateau of Thailand, and Saih Hatat of Oman. Although some sponge reefs and mounds can reach up to the unconformable
Permian/Triassic boundary, coral reef at Kanjia-ping, Cili County, is the latest Permian reef known. This reef appears to
had been formed in a palaeoenvironment that is different from that of the sponge reefs and provides an example of new and
unique Permian reef type in South China, and could help us to: 1) understand the significance of colonial corals in Permian
carbonate buildups; 2) evaluate the importance of coral community evolution prior to the collapse of reef ecosystems at the
Permian/Triassic boundary; 3) better understand the effects of the biotic extinction events in Palaeotethys realm; 4) look
for environmental factors that may have controlled reefs through time and space, and 5) provide valuable data for the study
of Permian palaeoclimate and global evolutionary changes of Permian reefs and reef community. 相似文献
9.
Numerous studies have documented declines in the abundance of reef-building corals over the last several decades and in some but not all cases, phase shifts to dominance by macroalgae have occurred. These assessments, however, often ignore the remainder of the benthos and thus provide limited information on the present-day structure and function of coral reef communities. Here, using an unprecedentedly large dataset collected within the last 10 years across 56 islands spanning five archipelagos in the central Pacific, we examine how benthic reef communities differ in the presence and absence of human populations. Using islands as replicates, we examine whether benthic community structure is associated with human habitation within and among archipelagos and across latitude. While there was no evidence for coral to macroalgal phase shifts across our dataset we did find that the majority of reefs on inhabited islands were dominated by fleshy non-reef-building organisms (turf algae, fleshy macroalgae and non-calcifying invertebrates). By contrast, benthic communities from uninhabited islands were more variable but in general supported more calcifiers and active reef builders (stony corals and crustose coralline algae). Our results suggest that cumulative human impacts across the central Pacific may be causing a reduction in the abundance of reef builders resulting in island scale phase shifts to dominance by fleshy organisms. 相似文献
11.
A quantitative survey of a submerged barrier reef was undertaken in Barbados, West Indies, over a two year period (1971–73). Photo-line transects were employed to obtain coverage data on corals and other benthic organisms. Light, sedimentation, currents, oxygen, temperature and salinity were also monitored. Results indicate corals cover about 30 per cent of the bottom with living colonies; another 7 per cent is contributed by other zoobenthos. The most abundant coral species are Montastrea annularis, M. cavernosa and Siderastrea siderea, each contributing between 4 and 5 per cent of bottom cover. Light is the only physical factor monitored that correlated significantly with biomass; sedimentation may have a secondary effect. Most of the barrier reef is composed of mixed coral associations forming a biologically accommodated community. Comparisons are made between the barrier reef in Barbados and deeper reefs in Jamaica and Curacao. Reefs are, in the main, similar but coral species and community structure differences do occur. 相似文献
12.
The global degradation of coral reefs is having profound effects on the structure and species richness of associated reef
fish assemblages. Historically, variation in the composition of fish communities has largely been attributed to factors affecting
settlement of reef fish larvae. However, the mechanisms that determine how fish settlers respond to different stages of coral
stress and the extent of coral loss on fish settlement are poorly understood. Here, we examined the effects of habitat degradation
on fish settlement using a two-stage experimental approach. First, we employed laboratory choice experiments to test how settlers
responded to early and terminal stages of coral degradation. We then quantified the settlement response of the whole reef
fish assemblage in a field perturbation experiment. The laboratory choice experiments tested how juveniles from nine common
Indo-Pacific fishes chose among live colonies, partially degraded colonies, and dead colonies with recent algal growth. Many
species did not distinguish between live and partially degraded colonies, suggesting settlement patterns are resilient to
the early stages of declining coral health. Several species preferred live or degraded corals, and none preferred to associate
with dead, algal-covered colonies. In the field experiment, fish recruitment to coral colonies was monitored before and after
the introduction of a coral predator (the crown-of-thorns starfish) and compared with undisturbed control colonies. Starfish
reduced live coral cover by 95–100%, causing persistent negative effects on the recruitment of coral-associated fishes. Rapid
reductions in new recruit abundance, greater numbers of unoccupied colonies and a shift in the recruit community structure
from one dominated by coral-associated fishes before degradation to one predominantly composed of algal-associated fish species
were observed. Our results suggest that while resistant to coral stress, coral death alters the process of replenishment of
coral reef fish communities. 相似文献
13.
Coral reefs are increasingly threatened by various disturbances, and a critical challenge is to determine their ability for
resistance and resilience. Coral assemblages in Moorea, French Polynesia, have been impacted by multiple disturbances (one
cyclone and four bleaching events between 1991 and 2006). The 1991 disturbances caused large declines in coral cover (~51%
to ~22%), and subsequent colonization by turf algae (~16% to ~49%), but this phase-shift from coral to algal dominance has
not persisted. Instead, the composition of the coral community changed following the disturbances, notably favoring an increased
cover of Porites, reduced cover of Montipora and Pocillopora, and a full return of Acropora; in this form, the reef returned to pre-disturbance coral cover within a decade. Thus, this coral assemblage is characterized
by resilience in terms of coral cover, but plasticity in terms of community composition. 相似文献
14.
Territorial damselfish are important herbivores on coral reefs because they can occupy a large proportion of the substratum
and modify the benthic community to promote the cover of food algae. However, on coastal coral reefs damselfish occupy habitats
that are often dominated by unpalatable macroalgae. The aim of this study was to examine whether damselfish can maintain distinctive
algal assemblages on a coastal reef that is seasonally dominated by Sargassum (Magnetic Island, Great Barrier Reef). Here, three abundant species ( Pomacentrus tripunctatus, P. wardi and Stegastes apicalis) occupied up to 60% of the reef substrata. All three species promoted the abundance of food algae in their territories. The
magnitudes of the effects varied among reef zones, but patterns were relatively stable over time. Damselfish appear to readily
co-exist with large unpalatable macroalgae as they can use it as a substratum for promoting the growth of palatable epiphytes.
Damselfish territories represent patches of increased epiphyte load on macroalgae, decreased sediment cover, and enhanced
cover of palatable algal turf. 相似文献
15.
The present study was conducted on Tamandaré reefs, northeast Brazil and aimed to analyse the importance of different factors (e.g. tourism activity, fishing activity, coral abundance and algal abundance) on reef fish abundance and species richness. Two distinct reef areas ( A ver o mar and Caieiras) with different levels of influence were studied. A total of 8239 reef fish individuals were registered, including 59 species. Site 1 ( A ver o mar) presented higher reef fish abundance and richness, with dominance of roving herbivores (29.9 %) and mobile invertebrate feeders (28.7 %). In contrast, at Site 2 ( Caieiras) territorial herbivores (40.9 %) predominated, followed by mobile invertebrate feeders (24.6 %). Concerning the benthic community, at Site 1 macroalgae were recorded as the main category (49.3 %); however, Site 2 was dominated by calcareous algae (36.0 %). The most important variable explaining more than 90 % of variance on reef fish abundance and species richness was macroalgae abundance, followed by fishing activity. Phase shifts on coral reefs are evident, resulting in the replacement of coral by macroalgae and greatly influencing reef fish communities. In this context, it is important to understand the burden of the factors that affect reef fish communities and, therefore, influence the extinction vulnerability of coral reef fishes. 相似文献
16.
Summary Analysis of the taxonomic composition, diversity and guild structure of five “typical” reef and mud mound communities ranging
in age from Late Devonian-Early Carboniferous indicates that each of these aspects of community organization changed dramatically
in relation to three extinction events. These events include a major or mass extinction at the end of the Frasnian; reef communities
were also effected by less drastic end-Givetian and mid-late Famennian extinctions of reef-building higher taxa.
Peak Paleozoic generic diversities for reef-building stromatoporoids and rugose corals occurred in the Eifelian-Givetian;
reef-building calcareous algal taxa were longranging with peak diversity in the Devonian. These three higher taxa dominated
all reef-building guilds (Constructor, Binder, Baffler) in the Frasnian and formed fossil reef communities with balanced guild
structures. The extinction of nearly all reef-building stromatoporoids and rugose corals at the end of the Frasnian and the
survival of nearly all calcareous algac produced mid-late Famennian reef communities dominated by the Binder Guild. Despite
the survival of most calcareous algae and tabulate corals, the mid-late Famennian extinction of all remaining Paleozoic stromatoporoids
and nearly all shelf-dwelling Rugosa brought the already diminished Devonian reef-building to a halt. These Devonian extinctions
differ from mass extinctions by the absence of a statistically significant drop in taxonomic diversity and by their successional
and cumulative effects on reef communities.
Tournaisian mud mounds contain communities markedly different from the frame-building communities in Late Devonian and Visean
reefs. Mound-building biotas consist of an unusual association dominated by erect, weakly skeletonized members of the Baffler
Guild (chiefly fenestrate Bryozoa; Pelmatozoa) and laterally expanded, mud-binding algae/stromatolites and reptant Bryozoa.
The initial recovery to reefs with skeletal frameworks in the Visean was largely due to the re-appearance of new species of
abundant colonial rugose corals (Constructor Guild) and fenestrate Bryozoa.
This Frasnian-Visean evolution in the taxonomic composition and structure of the reef-building guilds is also expressed by
abrupt changes in biofacies and petrology of the reef limestones they produced. Thus, “typical” Frasnian reef limestones with
balanced guild structures are framestones-boundstones-bafflestones, Famennian reefs are predominantly boundstones, Tournaisian
mud mounds are bafflestones and Visean reefs are bafflestones-framestones. 相似文献
17.
Along the northwestern margin of Safaga Island (Northern Bay of Safaga, Red Sea, Egypt) a small fringing reef (several hundred meters long, up to 2 m high) and small patch reefs are developed due to the local current regime which is favorable for coral growth. Corals and reef rock are encrusted by coralline algae, predominantly by branched Lithophyllum kotschyanum. Owing to destructional processes dominated by sea urchin activities, fragmentation of (1) corals, (2) reef rock, and (3) coralline algae takes place resulting in the formation of almost mono-specific, branched Lithophyllum kotschyanum rhodoliths. Rhodolith formation takes place in various reef environments: (1) in depressions on the reef flat where ellipsoidal rhodoliths develop, with interlocking and fusing branches leading to a coralline algal framework; (2) in discharge channels where smaller elongated rhodoliths occur; (3) in leeward positions between reef flat and seagrass meadows, where a dense belt of spheroidal to ellipsoidal rhodoliths is formed; scattered rhodoliths occur in adjacent seagrass beds. The formation and preservation of rhodoliths requires a complex interplay of destruction, growth, transportation, movement, and stabilization. 相似文献
18.
Summary The Upper Rhaetian coral limestone of Adnet, southeast of Salzburg Austria has been repeatedly referred to as one of the most
spectacular examples of an ancient ‘autochthonous’ coral reef structure. The ‘Tropfbruch’ quarry is probably the best outcrop
for interpreting the distributional patterns of biotic successions and communities of a late Triassic patch reef. Our study
is based on the interpretation of a) outcrop photographs, b) reef maps resulting from quadrat transects, and c) the analysis
of quantitative data describing the distribution and frequency of reef organisms and sediment. A new methodological approach
(combination of reef mapping and photo-transects) is used to obtain quantitative field data which can be compared in greater
detail with data from modern coral reefs investigated by corresponding quantitative surveys.
Three unconformities and three well-defined ‘reef growth stages’ reflecting the vertical and lateral development of the reef
structure were differrentiated using transects:
Stage 1, representing the reef growth optimum, is characterized by laterally differentiated coral reef knobs with corals in
growth position. Criteria supporting this interpretation are the extraordinary size of the corals, their preservation in situ
and the great thickness of this interval. The massive coral Pamiroseris grew under higher energy conditions at the rim of the reef knob, whereas branching Retiophyllia colonies preferred less agitated water in the center. Vertical changes are reflected by an increase in frequency of the dasycladacean
alga Diplopora adnetensis and by the decreasing size of Retiophyllia. These sedimentological and biological criteria together with the unconformity above indicate a fall in the sea level as
a major control mechanism.
Stage 2, separated from stage 1 by an unconformity caused by partial subaerial exposure and karstification, is characterized
by vertically stacked coral successions with diverse reef debris. Facies heterogeneity is reflected by differences in the
diversity, taphonomy and packing density of reef-building organisms as well as by differences in sediment input from the platform.
Water depths and accommodation space were lower, therefore minor sea level fluctuations had a stronger effect on the biotic
composition. The high percentage of coral debris and corals reworked by storms and the increase in the input of platform sediment
led to a reduction of reef growth.
Stage 3, again separated at the base by an unconformity associated with karstification, is characterized by bioclastic sediments
with isolated reefbuilders forming a level-bottom community. The distribution of different coral morphotypes suggests that
sea level fluctuations were not the only controlling factor. Variations in the substrate were caused by differences in the
input of platform sediment.
The three-step development seen in Adnet documents the response of low-diverse coral associations to variations caused by
small-scale sea level changes, storm activity and sedimentation. The vertical changes in reef community structures correspond
to a sequence of ‘allogenic replacements’.
The Adnet reef structure should not be regarded as a general model of Alpine Upper Rhaetian reefs, because of the particular
setting of the patch reef. Only the ‘capping beds’ of the Upper Rhaetian Reef Limestone of the Steinplatte exhibit criteria
similar to Adnet.
Potential modern analogues of features seen in the coral communities of Adnet are the internal structure of the Retiophyllia thickets, the key role of branching corals within the communities, the scattered distribution and low and even diversity
of corals subsequent to breaks in settlement, segration patterns of corals indicating ‘contact avoidance’, toppling of large
coral colonies by intensive boring, and decreasing coral coverage from deeper and sheltered settings to more shallower water
depths. 相似文献
19.
Summary The hermit crab Paguritta harmsi does not live in mobile shells, but occupies the calcareous tubes of the coral epibiont Spirobranchus giganteus (Polychaeta). Feathered (second) antennae are an unique adaptation to this sessile mode of life enabling the crab to utilize plankton carried by the water. The mode of filter feeding depends on the speed of water current: during stagnation of water the antennae are continuously moved fore- and backwards, during flowing water they are kept perpendicularly to the current forming a sieve. P. harmsi represents one more example to establish a specialized ecological niche in the highly complex ecosystem coral reef. 相似文献
20.
珊瑚藻是海洋红藻中的大型钙化藻类,全球分布623种,中国现有记录共77种。随着生态科学研究的广泛展开,人们越来越认识到,珊瑚藻在海洋生态系统中,尤其在维持珊瑚礁生态系统的生物多样性及生态功能中发挥着重要作用。目前,科研人员对有关珊瑚藻的初级生产力、钙化作用以及在诱导底栖无脊椎动物幼虫的附着与变态等方面已有多方面的研究和探索。然而,有关珊瑚藻生态功能的深层次机理问题有待进一步深入研究。文章着重围绕目前珊瑚藻研究中的一些热点问题,从近年来珊瑚藻在珊瑚礁生态系统中的生态功能方面的研究概况进行综述,以期加深人们对珊瑚藻的认识,并促进对珊瑚藻生态功能的进一步深入研究。 相似文献
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