Zonation Of Organisms Research Articles

Variación espacial y temporal de los organismos de un intermareal rocoso: Bahía Panamá, Pacífico Norte, Costa Rica

<p>The intertidal rocky shore of Bahía Panama, within Bahía Culebra in the North Pacific coast of Costa Rica, was sampled to study the biodiversity and the spatial patterns (three sites with differences in wave exposure, and five strata, from low to high tide levels) and temporal variation (a single date in 2007 and 2013) in different microhabitats (over and under rock surface, and crevices). The epibenthic organisms were sampled with quadrats of 25 x 25 cm in each stratum, and cryptic fauna was accounted by both visual census and manual collecting. The general pattern of vertical zonation of organisms at each site showed an increase in variety toward the infralittoral level, as well as in the composition of assemblages or partially in identity of taxa in each stratum. The sheltered section of the rocky coast, with shallow sand bottom (< 1 m), low wave action and greater sedimentation rate, had lower diversity, cover and abundance that increased towards the wave-exposed section, with more abrupt slope in the edge of rocky platform, lower turbidity, and deeper sand bottom (2-3 m). The horizontal change was more evident in epibenthic organisms, followed by the under rock surface inhabitants and finally in crevices. For the epibenthic organisms, a temporal change in assemblages (cover and abundance) was found between the 2007 and 2013, at each site and level (possibly by seasonal upwelling influence), but the spatial structure (vertical and horizontal) of the rocky shore seems the main cause of change in the composition of species. The spatial pattern of change in the biota (sheltered to exposed gradient) could be expected in similar shores of the Central American Pacific. Finally, the 157 species found (16 autotrophic taxa, 22 fishes, and 119 invertebrates) indicate the high biodiversity of this habitat in the tropics, and the importance of their conservation. Rev. Biol. Trop. 62 (Suppl. 4): 85-97. Epub 2014 Diciembre 01.</p>

Parasitism can influence the intertidal zonation of non-host organisms

Zonation of organisms in soft-bottom intertidal habitats is mainly a consequence of the tidal sorting of the substrate and how benthic organisms respond to it, with predation and competition also playing a role. Although parasites are ubiquitous in these habitats and known agents of community structure, their impact on zonation is rarely considered. Here, using observational and experimental data, we show that parasitism of the cockle Austrovenus stutchburyi by echinostome trematodes has both direct and indirect effects on the zonation of four other animals associated with cockles on a New Zealand tidal flat. The trematodes encyst in the foot of cockles, leaving heavily infected cockles unable to bury and lying exposed on the sediment surface. Whereas cockle density peaks in the mid intertidal zone, both infection intensity by trematodes and density of surfaced cockles increase linearly towards the shore; this influences the vertical zonation of animals attaching to or feeding on cockles. First, the relative abundance of the whelk Cominella glandiformis increase exponentially shoreward, as does its rate of predation on cockles; the effect of the parasite on the cockles’ burying ability has thus shifted the peak abundance of whelk predators towards the upper tidal level, away from peak cockle densities. Second, the density of the anemone Anthopleura aureoradiata, corrected for the availability of its cockle substrate, peaks in the lower intertidal zone, although a transplantation experiment revealed that anemones can survive higher up the shore if attached to buried cockles. Anemones on exposed cockles are susceptible to desiccation, and thus again the parasite-induced surfacing of cockles at higher tidal levels plays a role by decreasing substrate availability for anemones. Third, densities of the limpet Notoacmea helmsi increase rapidly toward higher tidal levels, where limpets graze the surfaces of empty cockle shells or live surfaced cockles. The availability of both substrates used by limpets is influenced either directly (surfaced cockles) or indirectly (empty shells, via whelk predation) by parasitism. Fourth, the fish Notolabrus celidotus feeds on cockles by cropping their foot. Although the lower intertidal is submerged for longer and cockle densities peak in the mid intertidal, the frequency of foot-cropping by fish peaks in the upper tidal levels, where parasitism maintains a high density of surfaced cockles. Our results are the first demonstration that parasitism of a key species can influence the zonation of non-host organisms, a phenomenon likely to occur in other systems.

Zonation of Organisms on Rocky Shores of Northern Jeddah

Zonation of Organisms on Rocky Shores of Northern Jeddah

Middle Triassic carbonate margin development: Hochstaufen-Zwieselmassif, northern Calcareous Alps, Germany

The Middle Triassic carbonate series of the Hochstaufen-Zwieselmassif reflect the last stage of a northward progradation of a wide southern reef platform extending into the attached northern basin. Regional facies differentiation was caused by differences in the morphology of the basin. A massive central reef core, exhibiting clear ecological zonation, developed along the slope of the slightly deeper eastern part of the basin. The shallower western parts, however, were quickly filled up by forereef debris and overlain by sediments of the rapidly spreading lagoon. A typical grapestone facies includes intercalations of vadose pisolitic crusts, thus indicating a shallow marine platform environment, which was sporadically interrupted by areas of subaerial exposure. Various sediment types occurring along the platform margin reflect synsedimentary mass movements. These were induced by tectonic disturbances caused by different rates of subsidence between the rapidly subsiding platform and the slowly subsiding basin. Forereef rocks which have been entirely lithified were affected by various stages of internal brecciation during this process. In contrast, basinal sediments which were semilithified or patchily cemented exhibit plastic deformation (slumping) and subsequent disintegration into intraformational breccias and debris flows. Turbidites were induced in cases of higher pore water saturations. All these mass mobilisations took place on gentle slopes. This assumption is supported by the observation of initial reef growth flourishing on protected areas of the foreslope. Along a gentle slope, differential rates of subsidence can easily be balanced by plastic deformation and dislocation of basinal material. This is supported by the fact that no prominent synsedimentary fault system could be observed along the platform margin. The facies differentiation of the central reef core is substantiated by a clear eclogical zonation of organisms. The lower, more protected portions of the central reef belt were occupied by theTubiphytes zones. Along the reef front the Coral-Solenoporacean biocoenoses found favorable living conditions. The high energy sediments of the reef flat exhibit a highly diverse Calcisponge—Hydrozoan—Coral community. Towards backreef areas a small belt was inhabited by a typicalThecosmilia —Thaumatoporella biocenosis.

Community structure and zonation of microalgae and hermatypic corals on a fringing reef flat of magnetic island (Queensland, Australia)

The community structure and zonation pattern of the two dominant benthic components (macroalgae and hermatypic corals) on a fringing reef flat at Geoffrey Bay (Magnetic Island, North Queensland) were investigated quantitatively, using a line transect intercept method. Data collected on species composition, distribution and abundance at three sampling locations on the reef flat were analysed and discussed in relation to the prevailing environmental factors.Two major communities are recognized: an Inner Sedimentary Accumulation community, and a Reef Flat community. Within the latter, several ecological units are distinguished in a seawards sequence: an Inner Reef Flat facies, a Middle Reef Flat facies and a Reef Flat-Reef Slope transition zone. Each of these units corresponds to particular morphological, sedimentological and hydrodynamic conditions which determine the distribution of species and species groups on the reef flat.Macroalgae are the dominant community component, by virtue of their widespread distribution and high abundance. In contrast, corals are restricted to the outer reef flat and seagrasses mainly to the inshore sedimentary substrates both being of relatively minor importance as structural elements in the communities. Macroalgal group analysis indicates that the low-growing turf forms are the most significant cover contributors on the reef flat. However, the large fleshy macroalgae, in particular tall Phaeophytes such as Sargassum spp., dominate community structure. The erect calcareous alga, Halimeda opuntia (Linnaeus) Lamouroux is an important component of the algal flora, particularly on the inner reef flat areas, notably contributing to reef sediments. Conversely encrustation on the reef by calcareous algal development is extremely limited.The zonation of organisms on the reef flat at Geoffrey Bay is discussed and compared with that of local (Great Barrier Reef) and other Indo-Pacific fringing reefs. The observed patterns appear typical of fringing reef flats associated with high islands in sheltered conditions.

“Migration” of blowouts in seagrass beds at Barbados and Carriacou, West Indies, and its ecological and geological implications

Blowouts are grass-free depressions within seagrass beds at Barbados and Carriacou and reported in the literature to be common elsewhere in the Caribbean region. They are typically crescent-shaped in plan view with the convex side seaward, and are characteristic of elevated seagrass beds in regions of moderate to strong wave action. The seaward edge is steep and exposes rhizomes of Thalassia while the leeward edge slopes gently upward onto the seagrass plateau and is usually colonized by Syringodium. The general morphology of the blowouts, the zonation of organisms across them, and the existence at some blowouts of a lag deposit of cobble-sized material at the scarp base continuous with a rubble layer below the seagrass carpet suggested the blowouts “migrate” seaward. Measurements of erosion at the scarp and of advance of Syringodium onto the blowout floor over a period of one year confirmed this. It is estimated that in the region of blowouts any one point will be recurrently eroded and restabilized at intervals of the order of 5–15 years. Such processes limit successional development of the seagrass beds, disrupt sedimentary structures, and may result in deposits much coarser than those characteristic of the sandy seagrass carpet.

The Ecology and Distribution of Intertidal Organisms on the Rocky Shores of the Queensland Mainland

This paper records investigations made on the ecology and biogeography of organisms found on rocky shores in eastern Queensland. Traverses were made at selected localities along a region of the coast bounded by the New South Wales-Queensland border (lat. 28� 15' S.) to the south and Whitecliffs (lat. 16� 39' S.) to the north. An account of general physiographic features and environmental factors in this region is given. It was found that the majority of typical Peronian organisms extended as far north as about lat. 25� S. North of lat. 25� S. tropical species occurred and the degree of overlapping of species from the two adjacent faunas was very small. However, the Moreton Bay-Caloundra region offered a refuge for some tropical forms. Zonation patterns on either side of the biogeographical boundary differed. In southern Queensland the zonation picture was similar to that in New South Wales as described by Dakin, Bennett , and Pope (1948); but in northern Queensland an oyster zone dominated the upper half of the intertidal region, whilst in the lower half a barnacle zone replaced the serpulid zone found in southern Queensland and New South Wales. The effects of various environmental factors on zonation on Queensland shores are discussed. It has been found that generalizations made by Evans (1947b) regarding zonation on British shores are only partially applicable to zonation in southern Queensland. Possible reasons for the differences noted are discussed. Also, the rate of change of percentage exposure to the air, which Doty (1946) has shown to be so potent a factor in determining the zonation of organisms at all levels in the intertidal region of the coasts of Oregon and northern California, apparently determines only the upper levels attained by organisms which extend above mean high water neap tide level on southern Queensland shores. Analyses of the effects of varying environmental factors, including gross environmental changes relating to latitude, on faunistic composition have been made. These have given much information on the general ecology of many common Queensland rocky shore species. Moreover, they have thrown much light on the reasons for the existence of a biogeographical boundary near latitude 25� S. In particular they have shown that such factors as the degree of wave action and salinity are possibly of more importance than temperature in determining the position of this boundary.