We studied the removal of dissolved organic carbon (DOC) and bacterioplankton by the encrusting sponges Halisarca caerulea, Mycale microsigmatosa and Merlia normani in coral reefs along Curaçao, Netherlands Antilles. Sponge specimens were collected from coral reef cavities and incubations were done on the fore-reef slope at 12 m depth. The concentrations of DOC and bacterioplankton carbon (BC) were monitored in situ, using incubation chambers with sponges and without sponges (incubations with coral rock or ambient reef water only). Average (± SD) DOC removal rates (in μmol C cm -3 sponge h -1 ) amounted to 13.1 ± 2.5, 15.2 ± 0.9 and 13.6 ± 2.4 for H. caerula, M. microsigmatosa and M. normani, respectively. The DOC removal rates by the 3 sponges were on average 2 orders of magnitude higher than BC removal rates and accounted for more than 90% of the total organic carbon removal. Total organic carbon removal rates presented here were the highest ever reported for sponges. In an additional experiment with H. caerulea, the fate of organic carbon was reconstructed by measuring dissolved oxygen (O 2 ) removal and dissolved inorganic carbon (DIC) release in a laminar flow chamber. H. caerulea respired 39 to 45% of the organic carbon removed. The remaining 55 to 61% of carbon is expected to be assimilated. We argue that H. caerulea may have a rapid turnover of matter. All 3 sponge species contained associated bacteria, but it is unclear to what extent the associated bacteria are involved in the nutrition of the sponge. We conclude that the 3 sponge-microbe associations are (related to the availability of dissolved and particulate carbon sources in the ambient water) 'dissolved organic matter (DOM)-feeders' and encrusting sponges are of quantitative importance in the removal of DOC in coral reef cavities.KEY WORDS: DOC · Sponges · Nutrition · Carbon budget · Nutrient cycling · Coral reef · Reef framework cavities · Caribbean · Curaçao Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 357: [139][140][141][142][143][144][145][146][147][148][149][150][151] 2008 organic carbon by sponges (Reiswig 1971) and the vast volumes of water sponges can process over time (Reiswig 1974b). He found a discrepancy between the supply and demand of carbon in benthic suspension feeders, and DOM was proposed to be the missing link (Reiswig 1981). It is generally assumed that only sponges with sponge-associated bacteria, sometimes comprising up to half of the total biomass of the sponge, are capable of utilizing DOM (Frost 1987, Ribes et al. 1999. Sponges have been demonstrated to take up the amino acid glycine (Stephens & Schinske 1961), 0.1 μm beads (Leys & Eerkes-Medrano 2006), as well as virus particles (Hadas et al. 2006) from ambient water. Both viral particles and 0.1 μm beads easily pass a 0.2 μm filter and are therefore operationally defined as 'dissolved '. Yahel et al. (2003) were the first to show extensive removal of bulk dissolved organic carbon (DOC) by the sponge Theone...

Oomycetes in the class Saprolegniomycetidae of the Eukaryotic kingdom Stramenopila have evolved as severe pathogens of amphibians, crustaceans, fish and insects, resulting in major losses in aquaculture and damage to aquatic ecosystems. We have sequenced the 63 Mb genome of the fresh water fish pathogen, Saprolegnia parasitica. Approximately 1/3 of the assembled genome exhibits loss of heterozygosity, indicating an efficient mechanism for revealing new variation. Comparison of S. parasitica with plant pathogenic oomycetes suggests that during evolution the host cellular environment has driven distinct patterns of gene expansion and loss in the genomes of plant and animal pathogens. S. parasitica possesses one of the largest repertoires of proteases (270) among eukaryotes that are deployed in waves at different points during infection as determined from RNA-Seq data. In contrast, despite being capable of living saprotrophically, parasitism has led to loss of inorganic nitrogen and sulfur assimilation pathways, strikingly similar to losses in obligate plant pathogenic oomycetes and fungi. The large gene families that are hallmarks of plant pathogenic oomycetes such as Phytophthora appear to be lacking in S. parasitica, including those encoding RXLR effectors, Crinkler's, and Necrosis Inducing-Like Proteins (NLP). S. parasitica also has a very large kinome of 543 kinases, 10% of which is induced upon infection. Moreover, S. parasitica encodes several genes typical of animals or animal-pathogens and lacking from other oomycetes, including disintegrins and galactose-binding lectins, whose expression and evolutionary origins implicate horizontal gene transfer in the evolution of animal pathogenesis in S. parasitica.