Giant clams and rising CO2: light may ameliorate effects of ocean acidification on a solar-powered animal

Global climate change and ocean acidification pose a serious threat to marine life. Marine invertebrates are particularly susceptible to ocean acidification, especially highly calcareous taxa such as molluscs, echinoderms and corals. The largest of all bivalve molluscs, giant clams, are already threatened by a variety of local pressures, including overharvesting, and are in decline worldwide. Several giant clam species are listed as 'Vulnerable' on the IUCN Red List of Threatened Species and now climate change and ocean acidification pose an additional threat to their conservation. Unlike most other molluscs, giant clams are 'solar-powered' animals containing photosynthetic algal symbionts suggesting that light could influence the effects of ocean acidification on these vulnerable animals. In this study, juvenile fluted giant clams Tridacna squamosa were exposed to three levels of carbon dioxide (CO2) (control ~400, mid ~650 and high ~950 µatm) and light (photosynthetically active radiation 35, 65 and 304 µmol photons/m**2/s). Elevated CO2 projected for the end of this century (~650 and ~950 µatm) reduced giant clam survival and growth at mid-light levels. However, effects of CO2 on survival were absent at high-light, with 100% survival across all CO2 levels. Effects of CO2 on growth of surviving clams were lessened, but not removed, at high-light levels. Shell growth and total animal mass gain were still reduced at high-CO2. This study demonstrates the potential for light to alleviate effects of ocean acidification on survival and growth in a threatened calcareous marine invertebrate. Managing water quality (e.g. turbidity and sedimentation) in coastal areas to maintain water clarity may help ameliorate some negative effects of ocean acidification on giant clams and potentially other solar-powered calcifiers, such as hard corals.

Skeletal matrices, muci, and the origin of invertebrate calcification.

The sudden appearance of calcified skeletons among many different invertebrate taxa at the Precambrian-Cambrian transition may have required minor reorganization of preexisting secretory functions. In particular, features of the skeletal organic matrix responsible for regulating crystal growth by inhibition may be derived from mucous epithelial excretions. The latter would have prevented spontaneous calcium carbonate overcrusting of soft tissues exposed to the highly supersaturated Late Proterozoic ocean [Knoll, A. H., Fairchild, I. J. & Swett, K. (1993) Palaios 8, 512-525], a putative function for which we propose the term "anticalcification." We tested this hypothesis by comparing the serological properties of skeletal water-soluble matrices and mucous excretions of three invertebrates--the scleractinian coral Galaxea fascicularis and the bivalve molluscs Mytilus edulis and Mercenaria mercenaria. Crossreactivities recorded between muci and skeletal water-soluble matrices suggest that these different secretory products have a high degree of homology. Furthermore, freshly extracted muci of Mytilus were found to inhibit calcium carbonate precipitation in solution.

Isolamento de vibrios potencialmente patogênicos em moluscos bivalves

Neste estudo, 26 amostras de ostras (Crassostrea gigas) comercializadas na cidade de São Paulo e em alguns pontos do litoral de São Paulo, e 36 amostras de mexilhões (Perna perna) colhidas mensalmente em 3 pontos do litoral de Ubatuba - SP, foram submetidas à pesquisa de vibrios potencialmente patogênicos. As amostras desses moluscos eram submetidas a enriquecimento em água peptonada alcalina sem cloreto de sódio e com 1 por cento de cloreto de sódio, e GSTB. O isolamento foi realizado em ágar TCBS. Colônias sacarose positivas e negativas, sugestivas de espécies de Vibrio foram identificadas presuntivamente em meio de ágar ferro de Kligler, sendo confirmadas através de provas bioqufmicas complementares. Uma parte das amostras de vibrios potencialmente patogênicos isoladas foi submetida ao teste de Dean e teste de alça ligada em íleo de coelhos. Os vibrios potencialmente patogênicos encontrados em amostras de ostras foram V. alginolyticus (81 por cento ), V.parahaemolyticus (77 por cento ), V. cholerae não 0:1 (31 por cento ), V. fluvialis (27 por cento ), V. furnissii (19 por cento ), V. mimicus (12 por cento ) e V. vulnificus (12 por cento ) e em amostras de mexilhões foram V. alginolyticus(97 por cento ), V. parahaemolyticus(75 por cento ), V. fluvialis (47 por cento ), V. vulnificus (11 por cento ), V. cholerae não 0:1 (6 por cento ), V. furnissii (6 por cento ) e V. mimicus (6 por cento ). Observou-se acúmulo de fluido em alça ligada de íleo de coelho entre 0,25 e 0,49 ml/cm em 6,9 por cento das amostras, entre 0,5 e 0,99 ml/cm em 15,6 por cento e maior ou igual a 1 ml/cm em 15,1 por cento , e/ou intestino de camundongos lactentes (Teste de Dean) em 26,6 por cento das amostras testadas, confirmando o elevado potencial desses microrganismos em causar gastrenterite. Verificou-se ausência de variação sazonal e também, de correlação entre os vibrios potencialmente patogênicos isolados e os indicadores de contaminação fecal, confirmando que a presença desses microrganismos ocorre de forma autóctone e que, as condições climáticas foram favoráveis à sobrevivência dessas espécies em todas as épocas do ano. Considerando-se os resultados obtidos no presente estudo e o fato de que ostras e mexilhões são habitualmente ingeridos crus ou insuficientemente cozidos, pode-se concluir que sua ingestão constitui-se em um determinado grau de risco para a saúde do consumidor.

Tecniche innovative microbiome-based per il recupero della vongola comune nelle aree ad alta mortalità nell’area FLAG dell’Emilia Romagna

Negli ultimi decenni sono state registrate preoccupati fenomeni di mortalità della vongola Chamelea gallina, in particolare nell’area costiera emiliano-romagnola e di cui non sono ancora state chiarite le cause. Il presente studio si è occupato di caratterizzare la comunità microbica associata alla vongola nella ghiandola digestiva, utilizzando il sequenziamento della regione ipervariabile V3-V4 del gene rRNA 16S, al fine di individuare fenomeni di disbiosi in aree ad elevata mortalità. Sono state quindi esplorate le variazioni stagionali (da luglio a novembre) nella struttura del microbiota della vongola e nell'ecosistema microbico dell'acqua di mare circostante, in quattro siti scelti ad hoc, secondo un gradiente di incidenza storica di mortalità, da Nord a Sud, tra le aree di Ravenna e Rimini. Lo stato di salute della vongola e del suo microbiota associato sono stati esplorati tramite, rispettivamente, l’indice di condizione e lo studio mediante NGS della composizione dell’ecosistema microbico intestinale. I nostri dati, sebbene preliminari, dimostrano come tra le aree Nord e Sud ci sia un comportamento differente e reciproco relativamente all’andamento stagionale dei valori di diversità interna (alfa) al microbiota della vongola, che si riduce dall’estate all’autunno nelle aree Nord (Ravenna e Lido di Savio), mentre aumenta - nello stesso periodo di tempo - nelle aree Sud (Rimini e Cesenatico). A conferma dei dati di alfa diversità, l’analisi mediante PCoA delle variazione del microbiota della vongola tra i quattro siti di indagine stratificate per stagione, dimostrano profonde differenze tra i due estremi nord-sud. In particolare, l’analisi integrata dei dati storici di produttività, indice di condizione e dinamica del microbiota della g.d. ci ha consentito di discriminare cinque famiglie microbiche come potenziali Growth Promoting Bacteria, poiché associate ad un picco di indice di condizione che si registra nelle aree a bassa mortalità, nel mese di settembre.

Analysis of marine bivalve shellfish from the fish market in Santos city, Sao Paulo state, Brazil, for Toxoplasma gondii

The aim of this study was to determine if Toxoplasma gondii are present in oysters (Crassostrea rhizophorae) and mussels (Mytella guyanensis) under natural conditions using a bioassay in mice and molecular detection methods. We first compared two standard protocols for DNA extraction, phenol-chloroform (PC) and guanidine-thiocyanate (GT), for both molluscs. A total of 300 oysters and 300 mussels were then acquired from the fish market in Santos city, Sao Paulo state, Brazil, between March and August of 2008 and divided into 60 groups of 5 oysters and 20 groups of 15 mussels. To isolate the parasite, five mice were orally inoculated with sieved tissue homogenates from each group of oysters or mussels. For molecular detection of T. gondii, DNA from mussels was extracted using the PC method and DNA from oysters was extracted using the GT method. A nested-PCR (Polymerase Chain Reaction) based on the amplification of a 155 bp fragment from the B1 gene of T. gondii was then performed. Eleven PCR-RFLP (Restriction Fragment Length Polymorphism) markers, SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, CS3 and Apico, were used to genotype positive samples. There was no isolation of the parasite by bioassay in mice. T. gondii was not detected in any of the groups of mussels by nested-PCR. DNA of T. gondii was apparently detected by nested-PCR in 2 groups of oysters (3.3%). Genotyping of these two positive samples was not successful. The results suggest that oysters of the species C. rhizophorae, the most common species from the coast of Sao Paulo, can filter and retain T. gondii oocysts from the marine environment. Ingestion of raw oysters as a potential transmission source of T. gondii to humans and marine mammals should be further investigated. (C) 2010 Elsevier B.V. All rights reserved.

Fertilisation and larval development in an Antarctic bivalve, Laternula elliptica, under reduced pH and elevated temperatures

Elevated temperatures associated with ocean warming and acidification can influence development and, ultimately, success of larval molluscs. The effect of projected oceanic changes on fertilisation and larval development in an Antarctic bivalve, Laternula elliptica, was investigated through successive larval stages at ambient temperature and pH conditions (-1.6°C and pH 7.98) and conditions representative of projections through to 2100 (-0.5°C to +0.4°C and pH 7.80 to pH 7.65). Where significant effects were detected, increased temperature had a consistently positive influence on larval development, regardless of pH level, while effects of reduced pH varied with larval stage and incubation temperature. Fertilisation was high and largely independent of stressors, with no loss of gamete viability. Mortality was unaffected at all development stages under experimental conditions. Elevated temperatures reduced occurrences of abnormalities in D-larvae and accelerated larval development through late veliger and D-larval stages, with D-larvae occurring 5 d sooner at 0.4°C compared to ambient temperature. Reduced pH did not affect occurrences of abnormalities in larvae, but it slowed the development of calcifying stages. More work is required to investigate the effects of developmental delays of the magnitude seen here in order to better determine the ecological relevance of these changes on longer term larval and juvenile success.

Determination of thresholds in marine molluscs as an alternative to the Environmental Quality Standards in marine water defined in the Water Framework Directive

The Water Framework Directive (WFD) establishes Environmental Quality Standards (EQS) in marine water for 34 priority substances. Among these substances, 25 are hydrophobic and bioaccumulable (2 metals and 23 organic compounds). For these 25 substances, monitoring in water matrix is not appropriate and an alternative matrix should be developed. Bivalve mollusks, particularly mussels (Mytilus edulis, Mytilus galloprovincialis), are used by Ifremer as a quantitative biological indicator since 1979 in France, to assess the marine water quality. This study has been carried out in order to determine thresholds in mussels at least as protective as EQS in marine water laid down by the WFD. Three steps are defined: - Provide an overview of knowledges about the relations between the concentrations of contaminants in the marine water and mussels through bioaccumulation factor (BAF) and bioconcentration factor (BCF). This allows to examine how a BCF or a BAF can be determined: BCF can be determined experimentally (according to US EPA or ASTM standards), or by Quantitative Activity-Structure Relationship models (QSAR): four equations can be used for mussels. BAF can be determined by field experiment; but none standards exists. It could be determined by using QSAR but this method is considered as invalid for mussels, or by using existing model: Dynamic Budget Model, but this is complex to use. - Collect concentrations data in marine water (Cwater) in bibliography for those 25 substances; and compare them with concentration in mussels (Cmussels) obtained through French monitoring network of chemicals contaminants (ROCCH) and biological integrator network RINBIO. According to available data, this leads to determine the BAF or the BCF (Cmussels /Cwater) with field data. - Compare BAF and BCF values (when available) obtained with various methods for these substances: BCF (stemming from the bibliography, using experimental process), BCF calculated by QSAR and BAF determined using field data. This study points out that experimental BCF data are available for 3 substances (Chlorpyrifos, HCH, Pentachlorobenzene). BCF by QSAR can be calculated for 20 substances. The use of field data allows to evaluate 4 BAF for organic compounds and 2 BAF for metals. Using these BAF or BCF value, thresholds in shellfish can be determined as an alternative to EQS in marine water.