RESUMO
Climate change will lead to community shifts and increase the vulnerability of coastal marine ecosystems, but there is yet insufficient detail of how early life stages of marine populations are linked to oceanic-climate dynamics. This study aimed to investigate how ocean-climate variability is associated with spatial and temporal changes in benthic larval recruitment of tropical reef assemblages. Recruitment (abundance, richness, and diversity) of benthic invertebrates was monitored for one year on macroalgal beds in four rocky reefs in a marine protected region in the Eastern coast of Brazil, and compared to fluctuations in meteo-oceanographic conditions at multiple temporal scales (days, weeks, and months). Our results revealed that recruitment of benthic invertebrates varies widely (up to 15 orders of magnitude) among sampled reefs and in time, with wave height, wind speed, and sea temperature being significantly related to recruitment variability. We detected strong taxonomic variability in recruitment success and ocean-climate variables, which highlights the complexity of estimating community vulnerability to climate change in benthic communities. Given that macroalgal beds are key to recruitment of some species regionally (4-30â¯km), the protection of coastal nursery habitats may be critical for marine conservation and species adaptation in a climate change scenario. Considering the projected ocean-climate change in IPCC scenarios, our study suggests that recruitment of marine populations in coastal reefs could be highly sensitive to climate change in the tropical South Atlantic Ocean.
Assuntos
Biodiversidade , Mudança Climática , Recifes de Corais , Animais , Antozoários/embriologia , Oceano Atlântico , Biota , Brasil , Conservação dos Recursos Naturais , Larva , Biologia Marinha , Clima TropicalRESUMO
Crustose coralline algae (CCA) are important components of many marine ecosystems. They aid in reef accretion and stabilization, create habitat for other organisms, contribute to carbon sequestration and are important settlement substrata for a number of marine invertebrates. Despite their ecological importance, little is known about the bacterial communities associated with CCA or whether differences in bacterial assemblages may have ecological implications. This study examined the bacterial communities on four different species of CCA collected in Belize using bacterial tag-encoded FLX amplicon pyrosequencing of the V1-V3 region of the 16S rDNA. CCA were dominated by Alphaproteobacteria, Gammaproteobacteria and Actinomycetes. At the operational taxonomic unit (OTU) level, each CCA species had a unique bacterial community that was significantly different from all other CCA species. Hydrolithon boergesenii and Titanoderma prototypum, CCA species that facilitate larval settlement in multiple corals, had higher abundances of OTUs related to bacteria that inhibit the growth and/or biofilm formation of coral pathogens. Fewer coral larvae settle on the surfaces of Paragoniolithon solubile and Porolithon pachydermum. These CCA species had higher abundances of OTUs related to known coral pathogens and cyanobacteria. Coral larvae may be able to use the observed differences in bacterial community composition on CCA species to assess the suitability of these substrata for settlement and selectively settle on CCA species that contain beneficial bacteria.
Assuntos
Antozoários/microbiologia , Carbono/química , Recifes de Corais , Cianobactérias/classificação , Alga Marinha/microbiologia , Microbiologia da Água , Alphaproteobacteria/classificação , Animais , Antozoários/embriologia , Belize , Biodiversidade , DNA Ribossômico/genética , Gammaproteobacteria/classificação , Larva , RNA Ribossômico 16S/genética , Rodófitas/microbiologia , Análise de Sequência de DNA , Especificidade da Espécie , SimbioseRESUMO
In response to dramatic losses of reef-building corals and ongoing lack of recovery, a small-scale coral transplant project was initiated in the Caribbean (U.S. Virgin Islands) in 1999 and was followed for 12 years. The primary objectives were to (1) identify a source of coral colonies for transplantation that would not result in damage to reefs, (2) test the feasibility of transplanting storm-generated coral fragments, and (3) develop a simple, inexpensive method for transplanting fragments that could be conducted by the local community. The ultimate goal was to enhance abundance of threatened reef-building species on local reefs. Storm-produced coral fragments of two threatened reef-building species [Acropora palmata and A. cervicornis (Acroporidae)] and another fast-growing species [Porites porites (Poritidae)] were collected from environments hostile to coral fragment survival and transplanted to degraded reefs. Inert nylon cable ties were used to attach transplanted coral fragments to dead coral substrate. Survival of 75 reference colonies and 60 transplants was assessed over 12 years. Only 9% of colonies were alive after 12 years: no A. cervicornis; 3% of A. palmata transplants and 18% of reference colonies; and 13% of P. porites transplants and 7% of reference colonies. Mortality rates for all species were high and were similar for transplant and reference colonies. Physical dislodgement resulted in the loss of 56% of colonies, whereas 35% died in place. Only A. palmata showed a difference between transplant and reference colony survival and that was in the first year only. Location was a factor in survival only for A. palmata reference colonies and after year 10. Even though the tested methods and concepts were proven effective in the field over the 12-year study, they do not present a solution. No coral conservation strategy will be effective until underlying intrinsic and/or extrinsic factors driving high mortality rates are understood and mitigated or eliminated. Rev. Biol. Trop. 60 (Suppl. 1): 59-70. Epub 2012 March 01.
En respuesta a la dramática pérdida de corales constructores de arrecifes y la continua falta de recuperación, un proyecto de pequeña escala de transplante de corales, al cual se le dio seguimiento por 12 años, se inició en el Caribe (Islas Vírgenes de EUA) en 1999. Los principales objetivos fueron (1) identificar fuentes de colonias de coral para el trasplante, que no produjeran daños a los arrecifes, (2) evaluar la viabilidad del trasplante de fragmentos de coral generados por tormentas, y (3) desarrollar un método simple y barato para transplantar fragmentos que pudiera ser realizado por la comunidad local. La meta última era aumentar la abundancia de especies constructoras de arrecife amenazadas en los arrecifes locales. Fragmentos de coral producidos por tormenta de dos especies constructoras de arrecife amenazadas [Acropora palmata y A. cervicornis (Acroporidae)] y otras especies de crecimiento rápido [Porites porites (Poritidae)] fueron recolectadas en ambientes no adecuados para la supervivencia de fragmentos de coral y se trasplantaron a los arrecifes degradados. Fajitas de nylon inerte fueron utilizadas para unir los fragmentos de corales transplantados al sustrato de coral muerto. La sobrevivencia de 75 colonias de referencia y de 60 transplantadas fueron monitoreadas por más de 12 años. Sólo el 9% de las colonias estaban vivas tras 12 años, sin presencia de A. cervicornis, el 3% de los transplantes de A. palmata y el 18% de las colonias de referencia de Acropora. El 13% de los transplantes de P. porites y el 7% de las colonias de referencia sobrevivieron. El desprendimiento físico resultó en la pérdida del 56% de las colonias, mientras que el 35% murió en el lugar. Solamente A. palmata mostró una diferencia en sobrevivencia entre los trasplantes y las colonias de referencia, eso fue solo en el primer año. La ubicación fue un factor en la sobrevivencia sólo para las colonias de referencia de A. palmata y después de 10 años. A pesar de que los métodos y los conceptos fueron probados efectivamente en el campo por más de 12 años de estudio, no mostraron ser la solución. Ninguna estrategia de conservación va a ser efectiva hasta que se delimiten y sean entendidos, mitigados o eliminados los factores intrínsecos y/o extrínsecos que conducen a las altas tasas de mortalidad.
Assuntos
Transplante , Ilhas Virgens Americanas , Antozoários/embriologia , Recifes de Corais , Estados UnidosRESUMO
Projected elevation of seawater temperatures poses a threat to the reproductive success of Caribbean reef-building corals that have planktonic development during the warmest months of the year. This study examined the transcriptomic changes that occurred during embryonic and larval development of the elkhorn coral, Acropora palmata, at a non-stressful temperature (28°C) and further assessed the effects of two elevated temperatures (30°C and 31.5°C) on these expression patterns. Using cDNA microarrays, we compared expression levels of 2051 genes from early embryos and larvae at multiple developmental stages (including pre-blastula, blastula, gastrula, and planula stages) at each of the three temperatures. At 12h post-fertilization in 28°C treatments, genes involved in cell replication/cell division and transcription were up-regulated in A. palmata embryos, followed by a reduction in expression of these genes during later growth stages. From 24.5 to 131h post-fertilization at 28°C, A. palmata altered its transcriptome by up-regulating genes involved in protein synthesis and metabolism. Temperatures of 30°C and 31.5°C caused major changes to the A. palmata embryonic transcriptomes, particularly in the samples from 24.5hpf post-fertilization, characterized by down-regulation of numerous genes involved in cell replication/cell division, metabolism, cytoskeleton, and transcription, while heat shock genes were up-regulated compared to 28°C treatments. These results suggest that increased temperature may cause a breakdown in proper gene expression during development in A. palmata by down-regulation of genes involved in essential cellular processes, which may lead to the abnormal development and reduced survivorship documented in other studies.
Assuntos
Antozoários/embriologia , Antozoários/crescimento & desenvolvimento , Antozoários/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Resposta ao Choque Térmico/genética , Temperatura , Animais , Antozoários/genética , Biologia Computacional , Regulação da Expressão Gênica no Desenvolvimento/genética , Larva/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Porto RicoRESUMO
Sexual recruitment of the staghorn coral, Acropora cervicornis, is accepted to be very rare. Instead, these branching corals proliferate through fragmentation leading to dense mono-specific and possibly monoclonal stands. For acroporid corals, which have suffered drastic population declines, dominance of asexual reproduction results in low levels of genotypic diversity and limited ability to re-colonize extirpated areas. Small colonies with a single encrusting, symmetrical base, and few incipient branches are frequently presumed to be the result of a settled planula (i.e. sexual reproduction). Here, we show that colonies fitting this description (i.e., presumed sexual recruits) can result from asexual fragmentation. Acropora cervicornis colonies (~20 cm diameter) were tagged and observed over eighteen months. In several cases, colony offshoots fused with the adjacent substrate forming secondary disc-like attachment points. Following natural fragmentation, these discs of tissue became separated from the original colony, and were observed to heal and give rise to smaller colonies with striking similarity to the expected morphology of a sexual recruit. Thus, presuming a colony is a sexual recruit based on appearance is unreliable and may lead to inflated expectations of genetic diversity among populations. The accurate assessment of recruitment and genetic diversity is crucial to predicting the recovery potential of these imperiled and ecologically irreplaceable reef corals. Rev. Biol. Trop. 54 (Suppl. 3): 145-151. Epub 2007 Jan. 15.
Se ha aceptado que el reclutamiento sexual del coral asta de venado, Acropora cervicornis, es muy raro. Por el contrario, estos corales ramificados proliferan a través de fragmentación, generando densas bases monoespecíficas e incluso monoclonales. Para corales acropóridos, los cuales han sufrido disminuciones de población drásticas, la dominancia de reproducción asexual resulta en bajos niveles de diversidad genotípica y abilidad limitada para recolonizar áreas de donde han sido erradicados. Frecuentemente se presume que las colonias pequeñas con una sola base incrustante simétrica y unas pocas ramas incipientes, son el resultado del asentamiento de una plánula (reproducción sexual). Aquí, nosotros demostramos que algunas colonias que calzan con esta descripción (supuesta reproducción sexual) pueden resultar de fragmentación asexual. Se etiquetaron y observaron colonias de Acropora cervicornis (~20 cm de diámetro) durante 18 meses. En muchos casos, los retoños de la colonia se fusionaron con el sustrato adyacente formando puntos de acoplamiento con forma de disco. Siguiendo con la fragmentación natural, estos discos de tejido se separaron de la colonia original, cicatrizaron y dieron paso a pequeñas colonias con tremenda similitud a la morfología esperada para un recluta sexual. Por lo tanto, asumir que una colonia es un recluta de origen sexual basándose en apariencia es poco fiable y puede generar expectativas infladas de diversidad genética entre poblaciones. La evaluación certera del reclutamiento y la diversidad genética es crucial para predecir la recuperación potencial de estos arrecifes de coral, los cuales están en peligro y son irremplazables.