Few studies to date have investigated the effects of ocean acidification on non-reef forming marine invertebrates with non-feeding larvae. Here, we exposed adults of the bryozoan Bugula neritina and their larvae to lowered pH. We monitored spawning, larval swimming, settlement, and post-settlement individual sizes at two pHs (7.9 vs. 7.6) and settlement dynamics alone over a broader pH range (8.0 down to 6.5). Our results show that spawning was not affected by adult exposure (48 h at pH 7.6), larvae swam 32% faster and the newly-settled individuals grew significantly larger (5%) at pH 7.6 than in the control. Although larvae required more time to settle when pH was lowered, reduced pH was not lethal, even down to pH 6.5. Overall, this fouling species appeared to be robust to acidification, and yet, indirect effects such as prolonging the pelagic larval duration could increase predation risk, and might negatively impact population dynamics.
Posts Tagged 'bryozoa'
Ocean acidification increases larval swimming speed and has limited effects on spawning and settlement of a robust fouling bryozoan, Bugula neritina
Published 27 March 2017 Science ClosedTags: adaptation, biological response, bryozoa, laboratory, morphology, North Pacific, otherprocess, performance, reproduction
Low pH conditions impair module capacity to regenerate in a calcified colonial invertebrate, the bryozoan Cryptosula pallasiana
Published 8 February 2017 Science ClosedTags: biological response, bryozoa, calcification, laboratory, physiology
Many 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.
Effects of ocean acidification on benthic organisms in the Mediterranean Sea under realistic climatic scenarios: A meta-analysis
Published 12 January 2017 Science ClosedTags: abundance, algae, biological response, bryozoa, calcification, cnidaria, corals, echinoderms, Mediterranean, methods, mollusks, morphology, mortality, otherprocess, photosynthesis, review
Ocean acidification is expected to cause significant changes in the marine environment over the coming century. The effects of acidification on organisms’ physiology have been studied over the past two decades. However, the experimental findings are not always easily comparable because of differences in experimental design, and comparable experiments do not always produce similar results. To rigorously integrate the current knowledge, we performed a meta-analysis of published studies focused on benthic organisms in the Mediterranean Sea, both in controlled manipulative experiments and in situ experiments near vent areas. In each experiment, the effect of acidification was calculated as the log-transformed response ratio (LnRR) of experimental versus control conditions. The quantitative results obtained by the meta-analysis highlight: (a) an increase in fleshy algae cover, which may lead to a competitive advantage over calcifying macroalgae; (b) a reduction of calcification by both algae and corals; (c) an increase in seagrass shoot density under low pH; and (d) a general increase in the photosynthetic activity of macrophytes.
Impacts of seawater saturation state (ΩA = 0.4 – 4.6) and temperature (10, 25 °C) on the dissolution kinetics of whole-shell biogenic carbonates
Published 19 July 2016 Science ClosedTags: algae, biological response, bryozoa, calcification, corals, crustaceans, dissolution, individualmodeling, laboratory, modeling, mollusks, multiple factors, North Atlantic, temperature
Anthropogenic increase of atmospheric pCO2 since the Industrial Revolution has caused seawater pH to decrease and seawater temperatures to increase—trends that are expected to continue into the foreseeable future. Myriad experimental studies have investigated the impacts of ocean acidification and warming on marine calcifiers’ ability to build protective shells and skeletons. No studies, however, have investigated the combined impacts of ocean acidification and warming on the whole-shell dissolution kinetics of biogenic carbonates. Here, we present the results of experiments designed to investigate the effects of seawater saturation state (ΩA = 0.4 – 4.6) and temperature (10, 25 °C) on gross rates of whole-shell dissolution for ten species of benthic marine calcifiers: the oyster Crassostrea virginicus, the ivory barnacle Balanus eburneus, the blue mussel Mytilus edulis, the conch Strombus alatus, the tropical coral Siderastrea siderea, the temperate coral Oculina arbuscula, the hard clam Mercenaria mercenaria, the soft clam Mya arenaria, the branching bryozoan Schizoporella errata, and the coralline red alga Neogoniolithon sp. These experiments confirm that dissolution rates of whole-shell biogenic carbonates decrease with calcium carbonate (CaCO3) saturation state, increase with temperature, and vary predictably with respect to the relative solubility of the calcifiers’ polymorph mineralogy [high-Mg calcite (mol% Mg > 4) > aragonite > low-Mg calcite (mol% Mg < 4)], consistent with prior studies on sedimentary and inorganic carbonates. Furthermore, the severity of the temperature effects on gross dissolution rates also varied with respect to carbonate polymorph solubility, with warming (10 – 25 °C) exerting the greatest effect on biogenic high-Mg calcite, an intermediate effect on biogenic aragonite, and the least effect on biogenic low-Mg calcite. These results indicate that both ocean acidification and warming will lead to increased dissolution of biogenic carbonates in future oceans, with shells/skeletons composed of the more soluble polymorphs of CaCO3 being the most vulnerable to these stressors. The effects of saturation state and temperature on gross shell dissolution rate were modelled with an exponential asymptotic function (y = B0 – B2· eB1·x) that appeals to the general Arrhenius-derived rate equation for mineral dissolution [r = (C · e-Ea/RT)(1-Ω)n]. Although the dissolution curves for the investigated biogenic CaCO3 exhibited exponential asymptotic trends similar to those of inorganic CaCO3, the observation that gross dissolution of whole-shell biogenic CaCO3 occurred (albeit at lower rates) even in treatments that were oversaturated (Ω > 1) with respect to both aragonite and calcite reveals fundamental differences between the dissolution kinetics of whole-shell CaCO3 and inorganic CaCO3. Thus, applying stoichiometric solubility products derived for inorganic CaCO3 to model gross dissolution of biogenic carbonates may substantially underestimate the impacts of ocean acidification on net calcification (gross calcification minus gross dissolution) of systems ranging in scale from individual organisms to entire ecosystems (i.e., net ecosystem calcification). Finally, these experiments permit rough estimation of the impact of CO2-induced ocean acidification on the gross calcification rates of various marine calcifiers, calculated as the difference between net calcification rates derived empirically in prior studies and gross dissolution rates derived from the present study. Organisms’ gross calcification responses to acidification were generally less severe than their net calcification response patterns, with aragonite mollusks (bivalves, gastropods) exhibiting the most negative gross calcification response to acidification, and photosynthesizing organisms, including corals and coralline red algae, exhibiting relative resilience.
Field-based experimental acidification alters fouling community structure and reduces diversity
Published 14 June 2016 Science ClosedTags: abundance, biological response, BRcommunity, bryozoa, community composition, crustaceans, field, mesocosms, mollusks, morphology, otherprocess, reproduction
1.Increasing levels of CO2 in the atmosphere are affecting ocean chemistry, leading to increased acidification (i.e., decreased pH) and reductions in calcium carbonate saturation state. 2.Many species are likely to respond to acidification, but the direction and magnitude of these responses will be based on interspecific and ontogenetic variation in physiology and the relative importance of calcification. Differential responses to ocean acidification among species will likely result in important changes in community structure and diversity. 3.To characterize potential impacts of ocean acidification on community composition and structure, we examined the response of a marine fouling community to experimental CO2 enrichment in field-deployed flow-through mesocosm systems. 4.Acidification significantly altered community structure by altering the relative abundances of species and reduced community variability, resulting in more homogenous biofouling communities from one experimental tile to the next both among and within the acidified mesocosms. Mussel (Mytilus trossulus) recruitment was reduced by over 30% in the elevated CO2 treatment compared to the ambient treatment by the end of the experiment. Strong differences in mussel cover (up to 40% lower in acidified conditions) developed over the second half of the 10-week experiment. Acidification did not appear to affect mussel growth, as average mussel sizes were similar between treatments at the end of the experiment. Hydroid (Obelia dichotoma) cover was significantly reduced in the elevated CO2 treatment after eight weeks. Conversely, the percent cover of bryozoan colonies (Mebranipora membranacea) was higher under acidified conditions with differences becoming apparent after six weeks. Neither recruitment nor final size of barnacles (Balanus crenatus) was affected by acidification. By the end of the experiment, diversity was 41% lower in the acidified treatment relative to ambient conditions. 5.Overall, our findings support the general expectation that OA will simplify marine communities by acting on important ecological processes that ultimately determine community structure and diversity.
Depth patterns in Antarctic bryozoan skeletal Mg-calcite: Can they provide an analogue for future environmental changes?
Published 9 December 2015 Science ClosedTags: Antarctic, biological response, bryozoa, field, morphology
Factors related to depth have the potential to provide an analogue for future changes in the skeletal mineralogy of calcifying marine organisms and communities, given that oceanic pH decreases with depth, with a minimum pH of <7.7, which corresponds to the predicted pH of shallow waters in the next 85 yr. Antarctic bryozoans are often characterized by surprisingly broad bathymetrical ranges, and thus have potential for the study of depth-related environmental changes. This study addressed depth-related changes in the levels of magnesium (Mg)-calcite in Antarctic bryozoan skeletons for the first time in order to facilitate predictions of ocean acidification effects. Specimens (n = 103) belonging to 4 bryozoan species (3 cheilostomes and 1 cyclostome) were collected at various depths in East Antarctica (Terre Adelie and George V Land) during the CEAMARC cruise (December 2007 to January 2008), and Mg-calcite contents from their calcareous skeletons were studied using X-ray diffraction. A dataset was compiled from existing environmental data for both sampling and neighboring sites. All 4 species were found to be entirely calcitic with low or intermediate Mg-levels. The predicted negative correlation between pH and Mg-calcite was not evident. Higher Mg levels were found in Fasciculipora ramosa from the George V Basin, suggesting that high salinity shelf water creates favorable conditions for this species, although alternative environmental and biological factors influencing Mg-calcite in skeletons are also discussed for this species.
Dissolution rates of biogenic carbonates in natural seawater at different pCO2 conditions: a laboratory study
Published 23 October 2015 Science ClosedTags: algae, biological response, bryozoa, crustaceans, dissolution, echinoderms, laboratory, North Atlantic, protists, sediment
The bulk dissolution rates of six biogenic carbonates (goose barnacle, benthic foraminifera, bryozoan, sea urchin, and two types of coralline algae) and a sample of mixed sediment from the Bermuda carbonate platform were measured in natural seawater at pCO2 values ranging from approximately 3000 to 5500 μatm. This range of pCO2 values encompassed values regularly observed in porewaters at a depth of a few cm in carbonate sediments at shallow water depths (<15 m) on the Bermuda carbonate platform. The biogenic carbonates included calcites of varying Mg content (2–17 mol%) and a range of specific surface areas (0.01–2.7 m2 g−1) as determined by BET gas adsorption. Measured rates of dissolution increased with increasing pCO2 treatment for all substrates and ranged from 2.5 to 18 μmol g−1 h−1. The highest rates of dissolution were observed for the bryozoans and the lowest rates for the goose barnacles. The relative ranking in dissolution rates between different substrates was consistent at all pCO2 levels, indicating that substrates dissolve sequentially and that some substrates will be more vulnerable than others to rising CO2 and ocean acidification. Furthermore, dissolution rates were found to increase with increasing Mg content, though the relative dissolution rates were observed to be a function of both Mg content and microstructure (surface area).
Bryozoans in climate and ocean acidification research: A reappraisal of an under-used tool
Published 20 August 2015 Science ClosedTags: biological response, bryozoa, methods, paleo, review
Bryozoans are colonial animals that are widely distributed in marine benthic environments and play an important role in temperate and cold-water oceanic shelves as habitat providers. Morphologically and mineralogically diverse, bryozoans are important carbonate producers with an extensive fossil record, which makes them good indicators in environmental and (paleo) environmental research. Existing data, though insufficient, suggests that bryozoans can become a valuable tool in investigating present-day climate change. This paper reviews the major characteristics of bryozoans, their function in shallow oceanic areas worldwide, and their potential as proxy organisms in climate and ocean acidification research.
Forever young… Colonization pattern of epibionts on Posidonia oceanica artificial leaves in relation to ocean acidification
Published 12 May 2015 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, bryozoa, community composition, field, Mediterranean, otherprocess
Ocean acidification (OA) is today considered one of the most pervasive stressors for marine biota at the level of species, communities and ecosystems. Naturally acidified systems, such as the CO2 vents, represent suitable laboratories to study the effects of OA on benthic organisms. An analysis of the colonization pattern of epibionts settled on artificial leaves (mimics) of Posidonia oceanica in relation to ocean acidification at the shallow CO2 vents off the island of Ischia, is here presented. Mimics of Posidonia oceanica artificial leaves (dark green flexible PVC stripes 1 cm wide x 36 cm long) were placed from September 2009 to September 2010 along a gradient of OA of the Ischia vent’s system at six stations (3 on the south and 3 on the north side of the study area), located at extreme low pH (mean pH 7.5), low pH (7.8), and control, normal pH conditions (8.12). Six artificial leaves per station were collected every three months and analysed for taxa identification and estimates of coverage (algae and sessile clonal invertebrates) and number of individuals (not clonal taxa). Patterns of colonization in control stations showed a progressive increase in time in coverage values of many organisms, mainly calcifying forms as coralline algae, which represent the dominant taxon, spirorbids and bryozoans. Colonization of artificial leaves located in low pH stations followed a similar temporal pattern as control conditions, but with lower coverage and higher patchiness of calcareous forms at 12 months of colonization. Epibionts in extreme low pH conditions were dominated by filamentous green/brown algae, with the occurrence of a few coralline algae, spirorbids and bryozoans, especially in the early months of colonization (3 and 6 months). Colonization at 9 and 12 months showed the disappearance of even these rare calcareous organisms and occurrence only of filamentous turf and fleshy algae, with a very simplified epibiont assemblage, remaining at an early, young colonization stage. These results indicate a strong selection of calcareous forms and the lack of successional stages in extreme low pH conditions, while the few calcifiers settled at short exposure time (3-6 months) do not seem to survive at longer exposure to critical values of OA.
Morphological plasticity in a calcifying modular organism: evidence from an in situ transplant experiment in a natural CO2 vent system
Published 12 February 2015 Science ClosedTags: biological response, bryozoa, field, growth, Mediterranean, morphology
Understanding 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.
Biomineralization in bryozoans: present, past and future
Published 12 November 2014 Science ClosedTags: biogeochemistry, biological response, bryozoa, calcification, chemistry, morphology, paleo, review
Many 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.
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Variability in the skeletal mineralogy of temperate bryozoans: the relative influence of environmental and biological factors
Published 27 October 2014 Science ClosedTags: biogeochemistry, biological response, bryozoa, chemistry, field, North Atlantic
Bryozoans exhibit a highly variable geochemistry within their calcium carbonate skeletons. Previous studies have predominantly attributed this variability to differences in seawater temperature influencing the relative deposition of aragonite and calcite, and the extent of magnesium incorporation into the calcite lattice. However, the patterns and scale of this variability have not been examined in detail. We conducted a high-replicate, multi-site study on the skeletal mineralogy of temperate Northern Hemisphere bryozoans to investigate the range of skeletal aragonite and Mg-calcite variability between species and the relative influence of environmental and biological factors on skeletal biogeochemistry. During a cruise in May 2012 in Scapa Flow, Orkney, Northeast Scotland, 480 specimens from 3 bryozoan species were collected by SCUBA diving. Samples were obtained from 5 study sites with similar depths and physical characteristics. All specimens were collected within the same week and were selected to be of similar size, age and breeding status. The results of X-ray diffraction analysis showed that wt% MgCO3 in calcite and wt% aragonite in total CaCO3 were statistically different between sites for all species. This may be explained by differential population connectivity between sites influenced by the tidal regimes of Scapa Flow. No temperate bryozoan species showed the expected positive trends of increasing wt% MgCO3 in calcite or wt% aragonite in total CaCO3 with seawater temperature. Based on the data generated in this study, we suggest that both environmental and biological factors are involved in the control of skeletal mineralogy in some temperate bryozoan species.
Settlement pattern of Posidonia oceanica epibionts along a gradient of ocean acidification: an approach with mimics
Published 24 March 2014 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, bryozoa, chordata, cnidaria, community composition, crustaceans, field, Mediterranean, morphology, otherprocess, phanerogams, reproduction
Effects of ocean acidification (OA on the colonization/settlement pattern of the epibiont community of the leaves and rhizomesof the Mediterranean seagrass,Posidoniaoceanica, have been studied at volcanic CO2vents off Ischia (Italy), using “mimics”as artificial substrates. The experiments were conducted in shallowPosidoniastands (2-3 m depth), in three stations on the northand three on the south sides of the study area, distributed along a pH gradient. At each station, 4 rhizome mimics and 6 artificialleaves were collected every three months (Sept 2009-Sept 2010). The epibionts on both leaf and rhizome mimics showed clearchanges along the pH gradient; coralline algae and calcareous invertebrates (bryozoans, serpulid polychaetes and barnacles) weredominant at control stations but progressively disappeared at the most acidified stations. In these extremely low pH sites theassemblage was dominated by filamentous algae and non calcareous taxa such as hydroids and tunicates. Settlement pattern onthe artificial leaves and rhizome mimics over time showed a consistent distribution pattern along the pH gradient and highlightedthe peak of recruitment of the various organisms in different periods according to their life history.Posidoniamimics at theacidified station showed a poor and very simplified assemblage where calcifying epibionts seemed less competitive for space. Thisprofound 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.
Continue reading ‘Settlement pattern of Posidonia oceanica epibionts along a gradient of ocean acidification: an approach with mimics’
Differential responses of calcifying and non-calcifying epibionts of a brown macroalga to present-day and future upwelling pCO2
Published 5 August 2013 Science ClosedTags: algae, annelids, Baltic, biological response, bryozoa, growth, laboratory, morphology, reproduction
Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida) and Electra pilosa (Bryozoa) and the non-calcifier Alcyonidium hirsutum (Bryozoa) were maintained for 30 days under three pCO2 conditions: natural 460±59 µatm, present-day upwelling1193±166 µatm and future upwelling 3150±446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm) but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic. Only extreme future upwelling conditions impacted the tubeworm S. spirorbis, but not the bryozoans.
Patterns of magnesium content in Arctic bryozoan skeletons along a depth gradient
Published 22 February 2013 Science ClosedTags: Arctic, bryozoa, calcification, paleo
A growing body of evidence suggests that ocean acidification acting synergistically with ocean warming alters carbonate biomineralization in a variety of marine biota. Magnesium often substitutes for Ca in the calcite skeletons of marine invertebrates, increasing their solubility. The spatio-environmental distribution of Mg in marine invertebrates has seldom been studied, despite its importance for assessing vulnerabilities to ocean acidification. Because pH decreases with water depth, it is predicted that levels of Mg in calcite skeletons should also decrease to counteract dissolution. Such a pattern has been suggested by evidence from echinoderms. Data on magnesium content and depth in Arctic bryozoans (52 species, 103 individuals, 150 samples) are here used to test this prediction, aided by comparison with six conceptual models explaining all possible scenarios. Analyses were based on a uniform dataset spanning more than 200 m of coastal water depth. No significant relationship was found between depth and Mg content; indeed, the highest Mg content among the analyzed taxa (8.7 % mol MgCO3) was recorded from the deepest settings (>200 m). Our findings contrast with previously published results from echinoderms in which Mg was found to decrease with depth. The bryozoan results suggest that ocean acidification may have less impact on the studied bryozoans than is generally assumed. In the broad context, our study exemplifies quantitative testing of spatial patterns of skeletal geochemistry for predicting the biological effects of environmental change in the oceans.
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The ecological effect of CO2 on the brown algae Fucus serratus and its epibionts: from the habitat to the organismic scale
Published 18 December 2012 Science ClosedTags: algae, annelids, Baltic, biological response, bryozoa, chemistry, field, growth, laboratory, photosynthesis, reproduction
Carbon dioxide plays a central role in the functioning of organisms and ecosystems. For autotrophs, it is the substrate for photosynthesis while for heterotrophs it is a waste product of respiration. For two centuries Human activities, are responsible for an increase from 280 to 380 μatm of the atmospheric pCO2. A further increase up to 1000 μatm is predicted for the 21th century. The ocean surface and the atmosphere are at the equilibrium for CO2. The CO2 dissolving in seawater reduces the pH and increase of corrosiveness of water for shells and skeletons made of calcium carbonates. Thus, this process of ocean acidification is expected to have detrimental effects on calcifying organism. On the contrary, marine autotrophs are supposed to (slightly) benefit from this extra supply of CO2. In this thesis, we aimed at assessing the influence of CO2 on members of the nearshore macrophytes meadows of the Baltic Sea, an ecosystem naturally exposed to elevated water acidity. In a first part, we investigated the natural variations of the carbonate system in a meadow during three weeks of July, August, and September 2011 in a sheltered bay of the Western Baltic. We observed important day night dynamics together with wider scale variations (days to weeks) of magnitude exceeding future climate change predictions. We were able to explain the variations by the action of light and wind speed and direction. Light drives the uptake and release of carbon by photosynthesis and respiration of the meadow and wind influences the upwelling of offshore hypercapnic seawater. In a second part, we investigated the growth response to elevated pCO2 of one of the main primary producer of the meadows, the brown algae Fucus serratus, in laboratory experiments. The algae were incubated under ambient pCO2, actual upwelling pCO2 and future upwelling pCO2. We observed an increase of growth of 20 % at the pCO2 expected for the year 2100 and up to 50 % at pCO2 possibly occurring during future upwelling events (4000 μatm). However, the effect was transient and a limitation of growth by nutrients occurred after about 20 days. In the third part, we tested the effect of at the same three pCO2 on the growth and recruitment of the main members of the sessile associated communities of Fucus serratus: the calcifying and non-calcifying bryozoan Electra pilosa and Alcyonidium hirsutum and the calcifying tubeworm Spirorbis spirorbis. We tested the hypothesis of greater sensitivity of calcifyers to acidification and found a resistance of all the tested organisms to the future ambient pCO2. In contrast, at the highest pCO2 tested (future upwelling), we observed in Spirorbis severe shell corrosion, reduction of growth and collapse of recruitment. The growth rates of the worm settlings were assessed at light and dark under the three experimental pCO2. A 40 % enhancement of growth was observed at light at any pCO2, possibly due to the algal photosynthetic reduction of pCO2 / increase of pH in the boundary layer surrounding the algal thallus. Our study illustrates the possibility of facilitation between species to resist ocean acidification.
Benthic invertebrates in a high-CO2 world
Published 27 June 2012 Science ClosedTags: biological response, bryozoa, cnidaria, corals, crustaceans, echinoderms, mollusks, protists, review
Ocean acidification (OA), whereby increases in atmospheric carbon dioxide (cO2) over the past 200 years have led to a decline in the pH and carbonate ion availability of the oceans, has emerged as one of the major drivers of twenty- first century marine scientific research. Here we describe the current understanding of OA effects on benthic marine invertebrates, in particular the calcifiers thought to be most sensitive to altered carbonate chemistry. We describe the responses of benthic invertebrates to OA conditions predicted up to the end of the century, examining individual organism response through to ecosystem- level impacts. Research over the past decade has found great variability in the physiological and functional response of different species and communities to OA, with further variability evident between life stages. Over both geological and recent timescales, the presence and calcification rates of marine calcifiers have been inextricably linked to the carbon chemistry of the oceans. Under short-term experimentally enhanced cO2 conditions, many organisms have shown trade-offs in their physiological responses, such as reductions in calcification rate and reproductive output. In addition, carry-over effects from fertilization, larval and juvenile stages, such as enhanced development time and morphological changes, highlight the need for broad- scale studies over multiple life stages. These organism- level responses may propagate through to altered benthic communities under naturally enhanced cO2 conditions, evident in studies of upwelling regions and at shallow- water volcanic cO2 vents. Only by establishing which benthic invertebrates have the ability to acclimate or adapt, via natural selection, to changes from OA, in combination with other environmental stressors, can we begin to predict the consequences of future climate change for these communities.
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Growth rates, age determination and calcification levels in Flustra foliacea (L.) (Bryozoa: Cheilostomata): preliminary assessment – Morphology, growth and calcification levels in Flustra foliacea (L.)
Published 12 June 2012 Science ClosedTags: Baltic, biological response, bryozoa, growth, morphology, North Atlantic
Potential consequences for species distribution, abundances and diversity and their imprint in food chains and ecosystems call for more studies of the short and long term impacts of ocean acidification. Bryozoans have been overlooked in this respect even though they play an important role in benthic temperate ecosystems. Flustra foliacea colonies from the North and Baltic Seas were used to assess morphology, growth rates, wall structure and preservation aiming to build up a baseline to use this species as a ‘sentinel’ of acidification levels. Though no significant differences in mean zooid size among the studied basins were found, North Sea colonies show periodic oscillations across generations in mean frontal area index and zooid density. Preliminary geochemistry analyzes show: (1) similar carbon contents (TC, TIC, TOC) in both basins; (2) skeletal walls composed of IMC; (3) over 50% weight loss in dissolution experiments during the first hour. A winter growth stop marked by growth-check lines is postulated. Experimental data are needed to calibrate results and assess collections done over the last 200 years.
Being a bimineralic bryozoan in an acidifying ocean – Ocean acidification and bryozoans
Published 12 June 2012 Science ClosedTags: biological response, bryozoa, dissolution, morphology
Strongly controlled calcification by bryozoans means that some species maintain complex skeletons formed of more than one mineral. Whether they are mainly intermediate-Mg calcitic with up to 50% aragonite, mainly aragonitic with small amounts of high-Mg calcite (>8 wt.% MgCO3), or formed of both high- and low-Mg calcites, preservation of sediments formed of these bimineralic bryozoan skeletons may be more at risk from ocean acidification than the majority of bryozoan sediments formed of monomineralic skeletons. An acid-bath immersion experiment on seven species reveals that three (Adeonella sp., Adeonella patagonica, and Adeonellopsis sp.) are more resistant to dissolution than the other four. Skeletal carbonate mineralogy appears to influence dissolution history very little: the most soluble aragonite and high-Mg calcite species, Adeonellopsis sp., was more highly resistant to dissolution than species dominated by low-Mg calcite. In the context of ocean acidification, it is likely that bryozoan skeletons with high surface area and small delicate morphologies are at greatest risk of dissolution, irrespective of mineralogical composition.
Patterns of Magnesium-calcite distribution in the skeleton of some polar bryozoan species – Mineralogy of polar bryozoan skeletons
Published 12 June 2012 Science ClosedTags: Antarctic, Arctic, biological response, bryozoa, calcification, morphology
Polar marine environments are already starting to exhibit the effects of climate change. The Arctic is the most rapidly warming place on Earth, and changes of the seawater chemistry of polar oceans have been recorded. Calcifying Bryozoa have diverse skeletal mineralogies making them an ideal model for investigating differences caused by environmental change. The aim of this study is to quantify the skeletal mineralogical diversity of polar bryozoans using X-ray diffraction (XRD). Six species of erect Bryozoa were analysed, three Arctic and three Antarctic species. Within each of the three species from each region, one has a cemented attachment point, one has flexible growth and the third is attached by chitinous rootlets. The analysis shows no significant difference in Mg-calcite distribution along the length of the six species but does show species-specific variation in both the consistency of Mg-calcite distribution along the length of a colony and the relationship between concentration of Mg-calcite in the root and growing tip. Analysis shows a statistically significant trend of increasing Mg-calcite concentration with increasing temperature. This adds further data to a growing body of published evidence for this mineralogy trend. The results of this study suggest that if bryozoan species are to be used as indicators of environmental change then it will be critical to have robust, replicated data of species-specific profiles for Mg-calcite distribution. This data, viewed alongside published mineralogy trends, may allow the use of skeletal mineralogy as a register of environmental effects and may enable monitoring of future impacts of climate change in marine benthic ecosystems.
