1,721,041 research outputs found
Settlement pattern of Posidonia oceanica epibionts along a gradient of ocean acidification: An approach with mimics
No full textEffects of ocean acidification (OA on the colonization/settlement pattern of the epibiont community of the leaves and rhizomes of the Mediterranean seagrass, Posidonia oceanica, have been studied at volcanic CO2 vents off Ischia (Italy), using "mimics" as artificial substrates. The experiments were conducted in shallow Posidonia stands (2-3 m depth), in three stations on the north and three on the south sides of the study area, distributed along a pH gradient. At each station, 4 rhizome mimics and 6 artificial leaves were collected every three months (Sept 2009-Sept 2010). The epibionts on both leaf and rhizome mimics showed clear changes along the pH gradient; coralline algae and calcareous invertebrates (bryozoans, serpulid polychaetes and barnacles) were dominant at control stations but progressively disappeared at the most acidified stations. In these extremely low pH sites the assemblage was dominated by filamentous algae and non calcareous taxa such as hydroids and tunicates. Settlement pattern on the artificial leaves and rhizome mimics over time showed a consistent distribution pattern along the pH gradient and highlighted the peak of recruitment of the various organisms in different periods according to their life history. Posidonia mimics at the acidified station showed a poor and very simplified assemblage where calcifying epibionts seemed less competitive for space. This profound difference in epiphyte communities in low pH conditions suggests cascading effects on the food web of the meadow and, consequently, on the functioning of the system
Low pH conditions impair module capacity to regenerate in a calcified colonial invertebrate, the bryozoan Cryptosula pallasiana
No full textMany aquatic animals grow into colonies of repeated, genetically identical, modules (zooids). Zooid interconnections enable colonies to behave as integrated functional units, while plastic responses to environmental changes may affect individual zooids. Plasticity includes the variable partitioning of resources to sexual reproduction, colony growth and maintenance. Maintenance often involves regeneration, which is also a routine part of the life history in some organisms, such as bryozoans. Here we investigate changes in regenerative capacity in the encrusting bryozoan Cryptosula pallasiana when cultured at different seawater pCO2 levels. The proportion of active zooids showing polypide regeneration was highest at current oceanic pH (8.1), but decreased progressively as pH declined below that value, reaching a six-fold reduction at pH 7.0. The zone of budding of new zooids at the colony periphery declined in size below pH 7.7. Under elevated pCO2 conditions, already experienced sporadically in coastal areas, skeletal corrosion was accompanied by the proportional reallocation of resources from polypide regeneration in old zooids to the budding of new zooids at the edge of the colony. Thus, future ocean acidification can affect colonial organisms by changing how they allocate resources, with potentially profound impacts on life-history patterns and ecological interactions. © 2017 Elsevier Lt
Long-term trend in substratum occupation by a clonal, carbonate bryozoan in a temperate rocky reef in times of thermal anomalies
No full textStudies over time provide opportunities to detect variations in the spatial and temporal patterns of clonal organisms and measure changes on their population dynamics related to extreme events. We assessed population dynamics for a bryozoan species dominating a subtidal rocky reef at Tino Island, in the eastern Ligurian Sea (NW Mediterranean). Using 9 years of annual photosurveys (1997-2005), rapid decline in Pentapora fascialis colony cover was shown at 11 and 22 m depths following the anomalous warming events in 1999 and 2003. An 86 % reduction in live colony portion was found after the 1999 warming event (2.3 ᄚC higher than normal), with larger colonies being most affected. Effects from the 2003 event were delayed, and gradual cover decline occurred during the following 2 years. At the "Shallow" photostations, none of the larger colonies (>1,000 cm2) survived after the first cover decline. Availability of new substrate after the 1999 disturbance resulted in enhanced recovery through new colony production. At the "Deep" photostations, the population structure did not change over the duration of the monitoring period showing the same monomodal structure and same dominant size class (50-500 cm2). In the 4 years following the first cover decline, the deeper population regained colony cover to levels similar to pre-disturbance level, showing a good resilience. This 9-year monitoring analysis provided the temporal resolution needed to detect changes occurring in the P. fascialis population and will contribute to the assessment of long-term changes on benthic populations suffering during recent decades from dramatic increases in extreme events. ᄅ 2013 Springer-Verlag Berlin Heidelberg
Biomineralization in bryozoans: Present, past and future
No full textMany animal phyla have the physiological ability to produce biomineralized skeletons with functional roles that have been shaped by natural selection for more than 500 million years. Among these are bryozoans, a moderately diverse phylum of aquatic invertebrates with a rich fossil record and importance today as bioconstructors in some shallow-water marine habitats. Biomineralizational patterns and, especially, processes are poorly understood in bryozoans but are conventionally believed to be similar to those of the related lophotrochozoan phyla Brachiopoda and Mollusca. However, bryozoan skeletons are more intricate than those of these two phyla. Calcareous skeletons have been acquired independently in two bryozoan clades - Stenolaemata in the Ordovician and Cheilostomata in the Jurassic - providing an evolutionary replicate. This review aims to highlight the importance of biomineralization in bryozoans and focuses on their skeletal ultrastructures, mineralogy and chemistry, the roles of organic components, the evolutionary history of bimineralization in bryozoans with respect to changes in seawater chemistry, and the impact of contemporary global changes, especially ocean acidification, on bryozoan skeletons. Bryozoan skeletons are constructed from three different wall types (exterior, interior and compound) differing in the presence/absence and location of organic cuticular layers. Skeletal ultrastructures can be classified into wall-parallel (i.e. laminated) and wall-perpendicular (i.e. prismatic) fabrics, the latter apparently found in only one of the two biomineralizing clades (Cheilostomata), which is also the only clade to biomineralize aragonite. A plethora of ultrastructural fabrics can be recognized and most occur in combination with other fabrics to constitute a fabric suite. The proportion of aragonitic and bimineralic bryozoans, as well as the Mg content of bryozoan skeletons, show a latitudinal increase into the warmer waters of the tropics. Responses of bryozoan mineralogy and skeletal thickness to oscillations between calcite and aragonite seas through geological time are equivocal. Field and laboratory studies of living bryozoans have shown that predicted future changes in pH (ocean acidification) combined with global warming are likely to have detrimental effects on calcification, growth rate and production of polymorphic zooids for defence and reproduction, although some species exhibit reasonable levels of resilience. Some key questions about bryozoan biomineralization that need to be addressed are identified. Biological Reviews © 2015 Cambridge Philosophical Society
Morphological plasticity in a calcifying modular organism: Evidence from an in situ transplant experiment in a natural CO2 vent system
No full textUnderstanding is currently limited of the biological processes underlying the responses of modular organisms to climate change and the potential to adapt through morphological plasticity related to their modularity. Here, we investigate the effects of ocean acidification and seawater warming on the growth, life history and morphological plasticity in the modular bryozoan Calpensia nobilis using transplantation experiments in a shallow Mediterranean volcanic CO2 vents system that simulates pH values expected for the year 2100. Colonies exposed at vent sites grew at approximately half the rate of those from the control site. Between days 34 and 48 of the experiment, they reached a possible ‘threshold’, due to the combined effects of exposure time and pH. Temperature did not affect zooid length, but longer zooids with wider primary orifices occurred in low pH conditions close to the vents. Growth models describing colony development under different environmental scenarios suggest that stressed colonies of C. nobilis reallocate metabolic energy to the consolidation and strengthening of existing zooids. This is interpreted as a change in life-history strategy to support persistence under unfavourable environmental conditions. Changes in the skeletal morphology of zooids evident in C. nobilis during short-time (87 days) exposure experiments reveal morphological plasticity that may indicate a potential to adapt to the more acidic Mediterranean predicted for the future. © 2015 The Authors
Fig. 2 in Growth of the bryozoan Pentapora fascialis (Cheilostomata, Ascophora) around submarine freshwater springs in the Adriatic Sea
No full textFig. 2: Area variations (cm 2) of living and necrotic parts of the five colonies of Pentapora fascialisPublished as part of Cocito, S., Novosel, M., Pasarić, Z. & Key, M.M., 2006, Growth of the bryozoan Pentapora fascialis (Cheilostomata, Ascophora) around submarine freshwater springs in the Adriatic Sea, pp. 15-24 in Linzer biologische Beiträge 38 (1) on page 22, DOI: 10.5281/zenodo.450705
Fig. 1 in Growth of the bryozoan Pentapora fascialis (Cheilostomata, Ascophora) around submarine freshwater springs in the Adriatic Sea
No full textFig. 1: The eastern Adriatic Sea with a detailed map of the study location.Published as part of Cocito, S., Novosel, M., Pasarić, Z. & Key, M.M., 2006, Growth of the bryozoan Pentapora fascialis (Cheilostomata, Ascophora) around submarine freshwater springs in the Adriatic Sea, pp. 15-24 in Linzer biologische Beiträge 38 (1) on page 21, DOI: 10.5281/zenodo.450705
Distribution pattern of the sublittoral epibenthic assemblages on a rocky shoal in the Ligurian Sea (NW Mediterranean)
No full textNutrient acquisition in four mediterranean gorgonian species
No full textCarbon and nitrogen isotope abundance values (d13C and d15N, respectively) were measured for the first time in the soft tissue, axial skeleton, and spicules of 4 Mediterranean gorgonians, 3 asymbiotic (Leptogorgia sarmentosa, Paramuricea clavata, and Eunicella verrucosa) and 1 symbiotic with autotrophic dinoflagellates (Eunicella singularis). The isotopic composition of their diet, i.e. zooplankton, particulate organic matter (POM), and sedimentary organic matter (SOM), was also measured to understand gorgonian feeding ecology. (1) Carbon and nitrogen signatures of the symbiotic E. singularis tissue in summer differed significantly from the signatures of the other species; (2) carbon and nitrogen signatures of the axial skeleton were similar to those of the tissue, because the skeleton is primarily made of gorgonin secreted by the tissue; and (3) spicules had a high d13C signature because they are made by a combination of 60 to 76% of respiratory CO2 and of external CO2, with a high d13C signature. Comparison of the isotopic signatures of the gorgonian tissues and the food sources indicated that E. singularis and P. clavata had the same diet in both winter and summer, either zooplankton for E. singularis or POM and SOM for P. clavata. Conversely, L. sarmentosa and E. verrucosa shifted from zooplankton in winter to SOM in summer. These results bring insights into the feeding ecology of temperate gorgonians and explain their distribution, abundance, and role in the flow of particulate matter between the water column and the benthos. © Inter-Research 2013
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