The removal of dissolved organic matter by marine sponges is a function of its composition and concentration: An in situ seasonal study of four Mediterranean species.

Sponges are unique among metazoans in their ability to use dissolved organic matter (DOM), the largest pool of organic matter in the ocean, as a major food source. The effect of variations in DOM abundance and composition on its uptake by sponges has rarely been studied. We examined, in situ, the seasonal uptake of DOM by four sponges [2 species with high microbial abundance (HMA) and 2 with low microbial abundance (LMA)] in the northwestern Mediterranean. Dissolved organic carbon (DOC) showed a strong seasonality with 3-fold higher concentrations in fall-winter (256 ± 16 µmol L-1, mean ± SE) than in spring-summer (88 ± 3 µmol L-1). Dissolved organic nitrogen (DON) showed the opposite trend, with higher summer concentrations (8.9 ± 0.4 µmol L-1) and mean concentrations of 2.5-3.4 µmol L-1 in the other seasons. DOC removal by all sponge species increased linearly with its ambient concentration, but only above a DOC removal threshold that was threefold higher in fall-winter (198 µmol L-1) than in spring-summer (74 µmol L-1). All species showed a concentration-dependent DON removal, but LMA sponges removed more DON than HMA sponges. The DOC removal rate (normalized to sponge volume) was 2-3 times higher in fall-winter, when ambient DOC levels were high, than in spring-summer. Sponges efficiently removed clusters of the fluorescent DOM (FDOM) associated with protein-rich DOM, but not those associated with humic material. The clear threshold for DOC removal and the protein-like FDOM uptake pattern suggest that the quality and quantity of DOM control its removal and transformation by marine sponges. Our results indicate that marine sponges transform the composition of the coastal DOM pool, thereby affecting its fate. It is postulated that the DOM excreted by the sponges is more recalcitrant; consequently, sponge activity enhances carbon sequestration in benthic habitats in a similar fashion to that of the oceanic 'microbial pump'.

Regional and local environmental conditions do not shape the response to warming of a marine habitat-forming species.

The differential response of marine populations to climate change remains poorly understood. Here, we combine common garden thermotolerance experiments in aquaria and population genetics to disentangle the factors driving the population response to thermal stress in a temperate habitat-forming species: the octocoral Paramuricea clavata. Using eight populations separated from tens of meters to hundreds of kilometers, which were differentially impacted by recent mortality events, we identify 25 °C as a critical thermal threshold. After one week of exposure at this temperature, seven of the eight populations were affected by tissue necrosis and after 30 days of exposure at this temperature, the mean % of affected colonies increased gradually from 3 to 97%. We then demonstrate the weak relation between the observed differential phenotypic responses and the local temperature regimes experienced by each population. A significant correlation was observed between these responses and the extent of genetic drift impacting each population. Local adaptation may thus be hindered by genetic drift, which seems to be the main driver of the differential response. Accordingly, conservation measures should promote connectivity and control density erosion in order to limit the impact of genetic drift on marine populations facing climate change.

Restructuring of the sponge microbiome favors tolerance to ocean acidification.

Ocean acidification is increasing and affects many marine organisms. However, certain sponge species can withstand low-pH conditions. This may be related to their complex association with microbes. We hypothesized that species with greater microbial diversity may develop functional redundancy that could enable the holobiont to survive even if particular microbes are lost at low-pH conditions. We evaluated the effects of acidification on the growth and associated microbes of three ubiquitous Mediterranean sponges by exposing them to the present pH level and that predicted for the year 2100. We found marked differences among the species in the acquisition of new microbes, being high in Dysidea avara, moderate in Agelas oroides and null in Chondrosia reniformis; however, we did not observe variation in the overall microbiome abundance, richness or diversity. The relative abilities to alter the microbiomes contributes to survivorship in an OA scenario as demonstrated by lowered pH severely affecting the growth of C. reniformis, halving that of A. oroides, and unaffecting D. avara. Our results indicate that functional stability of the sponge holobiont to withstand future OA is species-specific and is linked to the species' ability to use horizontal transmission to modify the associated microbiome to adapt to environmental change.

Functional convergence of microbes associated with temperate marine sponges.

Most marine sponges establish a persistent association with a wide array of phylogenetically and physiologically diverse microbes. To date, the role of these symbiotic microbial communities in the metabolism and nutrient cycles of the sponge-microbe consortium remains largely unknown. We identified and quantified the microbial communities associated with three common Mediterranean sponge species, Dysidea avara, Agelas oroides and Chondrosia reniformis (Demospongiae) that cohabitate coralligenous community. For each sponge we quantified the uptake and release of dissolved organic carbon (DOC) and nitrogen (DON), inorganic nitrogen and phosphate. Low microbial abundance and no evidence for DOC uptake or nitrification were found for D. avara. In contrast A. oroides and C. reniformis showed high microbial abundance (30% and 70% of their tissue occupied by microbes respectively) and both species exhibited high nitrification and high DOC and NH(4) (+) uptake. Surprisingly, these unique metabolic pathways were mediated in each sponge species by a different, and host specific, microbial community. The functional convergence of microbial consortia found in these two sympatric sponge species, suggest that these metabolic processes may be of special relevance to the success of the holobiont.

From global to local genetic structuring in the red gorgonian Paramuricea clavata: the interplay between oceanographic conditions and limited larval dispersal.

Defining the scale of connectivity among marine populations and identifying the barriers to gene flow are tasks of fundamental importance for understanding the genetic structure of populations and for the design of marine reserves. Here, we investigated the population genetic structure at three spatial scales of the red gorgonian Paramuricea clavata (Cnidaria, Octocorallia), a key species dwelling in the coralligenous assemblages of the Mediterranean Sea. Colonies of P. clavata were collected from 39 locations across the Mediterranean Sea from Morocco to Turkey and analysed using microsatellite loci. Within three regions (Medes, Marseille and North Corsica), sampling was obtained from multiple locations and at different depths. Three different approaches (measures of genetic differentiation, Bayesian clustering and spatially explicit maximum-difference algorithm) were used to determine the pattern of genetic structure. We identified genetic breaks in the spatial distribution of genetic diversity, which were concordant with oceanographic conditions in the Mediterranean Sea. We revealed a high level of genetic differentiation among populations and a pattern of isolation by distance across the studied area and within the three regions, underlining short effective larval dispersal in this species. We observed genetic differentiation among populations in the same locality dwelling at different depths, which may be explained by local oceanographic conditions and which may allow a process of local adaptation of the populations to their environment. We discuss the implications of our results for the conservation of the species, which is exposed to various threats.

Estimulación bicameral en una paciente con miocardiopatía hipertrófica obstructiva refractaria y mala tolerancia a la ultrafiltración extracorpórea / Dual-chamber pacing in a patient with refractory obstructive hypertrophic cardiomyopathy and intolerance to extracorporeal ultrafiltration

El tratamiento óptimo de los pacientes con miocardiopatía hipertrófica obstructiva refractaria al tratamiento médico convencional es motivo de controversia. Algunos autores han demostrado la eficacia, en cuanto a mejoría sintomática y reducción del gradiente dinámico, de la estimulación secuencial auriculoventricular en este tipo de pacientes. Se presenta el caso de una paciente trasplantada renal, con miocardiopatía hipertrófica obstructiva con gradiente subaórtico elevado, que ingresó en la unidad coronaria por insuficiencia cardíaca refractaria y deterioro de la función renal; precisó ultrafiltración extracorpórea que no toleraba de manera reiterada por episodios graves de bajo gasto. Se comentan los aspectos terapéuticos y se destaca la buena respuesta a la estimulación con marcapasos bicameral. La utilidad de la estimulación secuencial en pacientes con miocardiopatía hipertrófica obstructiva sometidos a ultrafiltración por presentar síntomas congestivos refractarios al tratamiento médico convencional no ha sido previamente comunicada (AU)

Seasonality in coastal benthic ecosystems.

For historical reasons, knowledge about seasonality in the dynamics of marine benthic suspension feeders from temperate areas comes mainly from studies of cold temperate seas. Recent surveys of Mediterranean taxa show different patterns from those observed in cold temperate seas, which are characterized by winter dormancy. In the Mediterranean, summer dormancy predominates among taxa and appears to be related to energetic constraints. Temperature and food availability are crucial to the dynamics of benthic suspension feeders. However, because these factors tend to be positively correlated in cold temperate seas, it is difficult to distinguish between their effects. Such correlation does not occur in Mediterranean ecosystems. The contrast between recent studies in the Mediterranean and in other areas can help to disentangle confounded environmental controls.

[Obstructive myocardiopathic hypertrophy and sequential atrioventricular stimulation. Immediate results and long term follow-up. Seven years experience]. / Miocardiopatía hipertrófica obstructiva y estimulación secuencial auriculoventricular. Resultados agudos y seguimiento a largo plazo. Siete años de experiencia.

BACKGROUND: Sequential pacing as a primary treatment for patients with severe hypertrophic obstructive cardiomyopathy is still under controversy. In this study we sought to evaluate the effects of pacing on left ventricular systolic and diastolic function, its repercussion on pathophysiology and the possible changes in clinical evolution and functional class in patients who didn't respond to medical therapy. PATIENTS AND METHODS: Thirty-four patients with severe hypertrophic obstructive cardiomyopathy in functional class III-IV underwent evaluation. The mean age was 64 +/- 11 years. Sixty-two per cent were over 65. The study protocol included Holter monitoring, baseline echo-Doppler, during pacing, at 6 months and at the end of follow-up, and a complete catheterization and coronary angiography. Mean follow-up time was 36 +/- 20 month (range 6-74). In four patients sequential pacing was ineffective and the protocol had to be discontinued. Thirty patients received a permanent dual-chamber pacemaker and systolic and diastolic function were evaluated by hemodynamic, angiographic and eco-Doppler studies. RESULTS: Long-term stimulation reduced the subaortic gradient from 95 +/- 38 to 39 +/- 28 mmHg (p < 0.001), left ventricular systolic pressure from 207 +/- 38 to 164 +/- 30 mmHg (p < 0.001) and left ventricular end-diastolic pressure from 23 +/- 7 to 14 +/- 5 mmHg (p < 0.001), pulmonary capillary wedge pressure from 19 +/- 7 to 14 +/- 5 mmHg (p < 0.001), ejection fraction from 79 +/- 6 to 71 +/- 6% (p < 0.001) and mitral insufficiency. Diastolic function improved with an increase in early filling from 39 +/- 11 to 52 +/- 10% (p < 0.001) and E/A relation from 0.93 +/- 0.4 to 1.6 +/- 0.8 (p < 0.001), and a reduction in late filling from the left ventricle from 36 +/- 10% to 24 +/- 10% (p < 0.001). The speed of the E wave increased from 0.83 +/- 0.3 to 0.92 +/- 0.3 (p < 0.001) and we observed a reduction of the A wave from 93 +/- 0.3 to 0.66 +/- 0.2 (p < 0.001), pressure-half time from 95 +/- 34 to 66 +/- 19 ms (p < 0.001) and we observed deceleration time from 320 +/- 90 to 221 +/- 57 (p < 0.01). All patients have improved their functional class, allowing a reduction in pharmacological therapy. Two exitus of cardiological origin occurred. CONCLUSIONS: Sequential AV pacing in selected patients with severe hypertrophic obstructive cardiomyopathy can reduce subaortic gradient, pulmonary capillary wedge, left ventricular filling pressures and the severity of mitral regurgitation, and improve the markedly altered diastolic function. The significant symptomatic improvement allows a reduction in medical treatment. Thus, it represents a viable alternative to open-heart surgery, particularly in elderly patients, with lower morbidity and mortality rates.

Benthic suspension feeders: their paramount role in littoral marine food webs.

In recent years, particular attention has been paid to coupling and energy transfer between benthos and plankton. Because of their abundance, certain benthic suspension feeders have been shown to have a major impact in marine ecosystems. They capture large quantities of particles and might directly regulate primary production and indirectly regulate secondary production in littoral food chains. Suspension feeders develop dense, three-dimensional communities whose structural complexity depends on flow speed. It has been postulated that these communities can self-organize to enhance food capture and thus establish boundary systems capable of successfully exploiting a less structured system, namely, the plankton.

Effects of Spatial Distribution and Reproductive Biology on in situ Fertilization Rates of a Broadcast-Spawning Invertebrate.

In situ fertilization was examined in the gorgonian Pseudoplexaura porosa during 1994 and 1995 spawning events in the San Blas Islands, Panama, to assess spatial and temporal variation in fertilization success and to determine whether in situ fertilization was sperm limited. Fertilization rates did not differ significantly between years (60% vs. 55%), but monthly means were significantly different, ranging from 22% to 66%. Fertilization rate varied among days, ranging from 0 to 85%; 80% of this variability was explained by daily variation in the number of colonies that spawned. A weighted average of in situ fertilization rates suggests that 67% or more of spawned eggs are fertilized in nature. Sperm limitation did not occur on the nights when most of the colonies synchronously spawned and when most of the eggs were released. Eggs collected downstream of the population often had higher fertilization rates than eggs collected either adjacent to their source colony or eggs collected in the middle of the population, which indicates that in dense populations, eggs may have multiple opportunities to be fertilized. Traits such as highly synchronous spawning, high fecundity, large egg size, large polyps, and large colonies directly and indirectly enhance P. porosa gamete production and fertilization. These life-history traits reduce the effects of gamete dilution during spawning events and thus decrease the importance of sperm limitation in the population dynamics of P. porosa.

In situ Rates of Fertilization Among Broadcast Spawning Gorgonian Corals.

Fertilization rates among marine benthic taxa have implicitly been assumed to be uniformly high in most analyses of life history evolution, but in situ fertilization rates during natural spawning events are rarely measured. Fertilization rates of the Caribbean gorgonians Plexaura kuna and Pseudoplexaura porosa were measured at a site in the San Blas Islands, Panama, by collecting eggs downstream of colonies during synchronous spawning events during the summer months in the years 1988-1994. Eggs collected by divers were incubated, and the proportion of eggs that developed was determined. Proportions of eggs developing suggest fertilization rates that vary from 0% to 100%. Monthly means ranged from 0% to 60.4%. Failure of gametes to develop can be attributed to sperm limitation, as eggs collected during spawning had higher fertilization rates if incubated with an excess of sperm. Plexaura kuna fertilization rates were highest during the July spawning events. Fertilization of Plexaura kuna eggs was usually lower during the first two nights of the 4-6 night spawning event. The proportion of eggs being fertilized when collected from a given place and time was highly variable, with one peak in the frequency distribution at or below 20% fertilization, and a second group of samples with greater fertilization rates. High variance in fertilization rates is evident at all levels of analysis: between replicate samples, times within nights, and among nights and months. This variance can be attributed to a combination of the effects of heterogeneity in the water column as gametes are diluted, spawning behavior of the gorgonians, and the current regime. Fertilization rates are often low and may represent a limiting step in recruitment during some years. Low fertilization rates may also be an important component of the life history evolution of these species.

[The treatment of hypertrophic obstructive cardiomyopathy refractory to medical treatment by DDD pacing]. / Tratamiento de la miocardiopatía hipertrófica obstructiva refractaria al tratamiento médico con estimulación DDD.

INTRODUCTION AND OBJECTIVES: In spite of medical treatment, 10% of patients with hypertrophic obstructive cardiomyopathy remain symptomatic, needing surgical treatment. Recent evidence suggests that sequential atrio-ventricular pacing may improve the hemodynamic and clinical situation. PATIENTS AND METHODS: We studied 10 patients with hypertropic obstructive cardiomyopathy (6 women), aged 37-76 years (X = 62 +/- 12) with dyspnea and/or angina, in functional class IV (7) or III (3) of the New York Heart Association. Hemodynamic study was performed basaly and during atrio-ventricular pacing with atrio-ventricular intervals ranging from 75% of basal PR to 50 ms. A DDD pacemaker was implanted in 9 cases, the remainder was treated surgically. RESULTS: The pressure gradient was reduced from 105 +/- 32 to 40 +/- 35 mmHg (p < 0.001); end-diastolic left ventricular pressure fell from 22 +/- 4 to 13 +/- 8 mmHg (p < 0.01), systolic aortic pressure rose from 107 +/- 24 to 125 +/- 13 mmHg (p < 0.05) and cardiac output increased from 3.6 +/- 1.1 to 4.1 +/- 0.81/m (p < 0.05). Mitral insufficiency decreased in 5 of 6 cases, notably in 2 improving from 4+ to 1+. After 1-20 months (X = 10 +/- 6) the 9 patients treated with a permanent DDD pacemaker are in functional class I (7 cases) or II (2 cases). CONCLUSIONS: Atrio-ventricular pacing hypertrophic obstructive cardiomyopathy reduces the systolic gradient and left ventricular end-diastolic pressure with an increase in cardiac output and aortic pressure and improves mitral insufficiency. Short-mid term follow up shows sustained clinical improvement. Optimal atrio-ventricular interval should be individualized.