Incidence and identity of photosynthetic symbionts in Caribbean coral reef sponge assemblages

Abstract

Marine sponges are abundant and diverse components of coral reefs and commonly harbour photosynthetic symbionts in these environments. The most prevalent symbiont is the cyanobacterium, Synechococcus spongiarum, isolated from taxonomically diverse hosts from geographically distant regions. We combined analyses of chlorophyll-a (chl-a) concentrations with line-intercept transect surveys to assess the abundance and diversity of reef sponges hosting photosymbionts on Caribbean coral reefs in the Bocas del Toro Archipelago, Panama. To identify symbionts, we designed PCR primers that specifically amplify a fragment of the 16S ribosomal RNA gene from S. spongiarum and used these primers to screen potential host sponges for the presence of this symbiont. Chlorophyll-a data divided the sponge community into two disparate groups, species with high (>125 Mg/g, N=20) and low (<50 Mg/g, N=38) chl-a concentrations. Only two species exhibited intermediate (50-125 (Jg/g) chl-a concentrations; these species represented hosts with reduced symbiont populations, including bleached Xestospongia muta and the mangrove form of Chondrilla nucula (C. nucula f. hermatypicd). Sponges with high and intermediate chl-a concentrations accounted for over one-third of the species diversity and abundance of sponges in these communities. Most (85%) of these sponges harboured S. spongiarum. Molecularphylogenies reveal that S. spongiarum represents a sponge-specific Synechococcus lineage, distinct from free-living cyanobacteria. The prevalence of sponge-photosymbiont associations and dominance of symbiont communities by S. spongiarum suggest a major role of this cyanobacterium in sponge ecology and primary productivity on coral reefs.

Complex interactions between marine sponges and their symbiotic microbial communities

“…The sponges A. fulva, N. subtriangularis, and N. erecta were collected at depths of 2-5 m near the Bocas Research Station of the Smithsonian Tropical Research Institute (STRI; Bocas del Toro, Panama). These sponge species are dominant members of the reef community at their respective locations (Olson et al 2006;Erwin and Thacker 2007) and all have a rope-like growth form that is ideal for attaching to artificial substrates. A shading experiment using A. cauliformis was conducted at Big Point, a 3-4-m-deep site north of CMRC in May 2009.…”

Bleaching of the giant barrel sponge Xestospongia muta in the Florida Keys

“…Populations constitute a significant amount of overall reef biomass (McMurray et al 2010), are an important component of habitat heterogeneity, and filter large volumes of seawater (Southwell et al 2008). Peripheral tissues harbor cyanobacteria of the genus Synechococcus that impart a reddish-brown coloration to unbleached individuals (Gó mez et al 2002;Erwin and Thacker 2007). During bleaching, sponges undergo a lightening of this characteristic coloration to the point that they may appear creamy-white or white in patches or spots (Vicente 1990;Cowart et al 2006).…”

Estructura de la comunidad de esponjas (Porifera) en tres arrecifes del Parque Nacional Morrocoy, Venezuela y su relación con algunas variables ambientales

“…Tal es el caso de las que no presentan endosimbiontes fotosintéticos que le aportan nutrientes y dependen totalmente de la filtración para obtener alimento (totalmente heterótrofas), las cuales son más favorecidas en ambientes de aguas turbias que aquellas que dependen más de sus simbiontes (Valderrama & Zea 2003). Según Erwin & Thacker (2007), estas especies presentan muy bajos contenidos de Clorofila a en sus tejidos, lo cual puede ser indicativo de ausencia o muy poca presencia de simbiontes fotosintetizadores, resultados confirmados para D. etheria, en la cual estos autores no reportaron presencia de cianobacterias por medio de análisis de reacción en cadena de la polimerasa (PCR, en inglés) específicos para ellas.…”