Sponges have traditionally been viewed as rather unselective filter feeders, and therefore as potential biofilters to remediate microbial water pollution. Here we show that the assumed connection between the ability of sponges to feed on microbes and the potential biotechnological use of such an ability to reduce microbial pollution is more complex than assumed. In a laboratory feeding experiment combined with a transmission electron microscopy study, we assessed the potential of the marine sponge Hymeniacidon perlevis to ingest and digest 3 common pathogenic microbes occurring in coastal waters: 2 bacteria (Escherichia coli and Vibrio anguillarum), and 1 marine yeast Rhodotorula sp. All 3 microbes were ingested by the sponge, but selectively, at different rates and following different cellular mechanisms. Yeast cells were processed very atypically by the sponge. Differences in the ingestion and digestion pathways led to large differences in the effectiveness of the sponge to remove the microbes. While sponge grazing reduced the concentration of E. coli and Rhodotorula sp. to levels far below the initial values, sponges were ineffective in abating concentrations of the most infective bacterium, V. anguillarum. This bacterium, which was digested more slowly than E. coli, proliferated in the experimental flasks at much higher rates than it was grazed. These findings raise the question whether sponges are suitable for bioremediation of microbial pollution, since selective or preferential ingestion of certain bacteria by sponges may end up fueling growth of those grazed less, such as Vibrio spp.

The aim of this article is to investigate the potential of using sponges as a bioremediator to remove pathogenic bacteria in integrated aquaculture ecosystems. Using the inter-tidal marine sponge Hymeniacidon perleve as a model system, the ability of removing the most common pathogens Escherichia coli and Vibrio anguillarum II in aquaculture waters was screened in laboratory tests. In sterilized natural seawater (SNSW) supplemented with E. coli at (7.0-8.3) x 10(6) cells/mL, H. perleve can remove an average 96% of E.coli within 10.5 h at a filter rate of ca. (7.53-8.03) x 10(7) cells/h x g of fresh sponge in two independent tests. Despite the removal efficiency and filter rate are similar; the clearance rates (CR) vary significantly among individual sponge specimens and between two batches. For the tests on V. anguillarum II in SNSW, about 1.5 g fresh sponges can keep the pathogen growth under control at a lower initial density 3.6 x 10(4) cells/mL of 200 mL water volume. Further tests were done for 24 h using about 12 g fresh sponge in 2-L actual seawater collected from two aquaculture sites that have ca. eightfold difference in pathogenic bacteria load. The concentrations of E. coli, Vibrio, and total bacteria at 24 h in treatment groups were markedly lower, at about 0.9%, 6.2%-34.5%, and 13.7%-22.5%, respectively, of those in the control. Using a fluoresce stain 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, E. coli, and V. anguillarum II cells were stained and fed to sponges in two independent tests. The confocal microscope observation confirmed that the sponges filtering-retained and digested these bacteria by phagocytosis.

Sessile filter-feeding marine sponges (Porifera) have been reported to possess high efficiency in removing bacteria pollution from natural or aquaculture seawater. However, no investigation has been carried out thus far in a true mariculture farm water system. Therefore this study sought to investigate the ability of the marine sponge Hymeniacidon perlevis to bioremediate the bacteria pollution in the intensive aquaculture water system of turbot Scophthalmus maximus. Sponge specimens were hung in fish culture effluent at different temperature to investigate the optimal temperature condition for bacteria removal by H. perlevis. Turbots S. maximus were co-cultured with sponge H. perlevis in 1.5 m(3) of water system at 15-18 degrees C for 6 weeks to control the growth of bacteria. It was found that H. perlevis was able to remove pathogenic bacteria efficiently at 10-20 degrees C, with a maximal removal of 71.4-78.8% of fecal coliform, 73.9-98.7% of pathogenic vibrio, and 75.0-83.7% of total culturable bacteria from fish-culture effluent at 15 degrees C; H. perlevis continuously showed good bioremediation of bacteria pollution in the S. maximus culture water system, achieving removal of 60.0-90.2% of fecal coliform, 37.6-81.6% of pathogenic vibrio, and 45.1-83.9% of total culturable bacteria. The results demonstrate that H. perlevis is an effective bioremediator of bacteria pollution in the turbot S. maximus culture farm water system.