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

Heterotrophy in marine animal forests in an era of climate change

Marine animal forests (MAFs) are benthic ecosystems characterised by biogenic three-dimensional structures formed by suspension feeders such as corals, gorgonians, sponges and bivalves. They comprise highly diversified communities among the most productive in the world's oceans. However, MAFs are in decline due to global and local stressors that threaten the survival and growth of their foundational species and associated biodiversity. Innovative and scalable interventions are needed to address the degradation of MAFs and increase their resilience under global change. Surprisingly, few studies have considered trophic interactions and heterotrophic feeding of MAF suspension feeders as an integral component of MAF conservation. Yet, trophic interactions are important for nutrient cycling, energy flow within the food web, biodiversity, carbon sequestration, and MAF stability. This comprehensive review describes trophic interactions at all levels of ecological organisation in tropical, temperate, and cold-water MAFs. It examines the strengths and weaknesses of available tools for estimating the heterotrophic capacities of the foundational species in MAFs. It then discusses the threats that climate change poses to heterotrophic processes. Finally, it presents strategies for improving trophic interactions and heterotrophy, which can help to maintain the health and resilience of MAFs.

Metallic trace elements in marine sponges living in a semi-enclosed tropical lagoon

The ability of marine filter feeders to accumulate metals could help monitor the health of the marine environment. This study examined the concentration of metallic trace elements (MTE) in two marine sponges, Rhabdastrella globostellata and Hyrtios erectus, from three sampling zones of the semi-enclosed Bouraké Lagoon (New Caledonia, South West Pacific). MTE in sponge tissues, seawater, and surrounding sediments was measured using inductively coupled plasma with optical emission spectroscopy. The variability in sponge MTE concentrations between species and sampling zones was visually discriminated using a principal component analysis (PCA). Sponges showed Fe, Mn, Cr, Ni, and Zn concentrations 2 to 10 times higher than in the surrounding sediments and seawater. Hyrtios erectus accumulated 3 to 20 times more MTE than R. globostellata, except for Zn. Average bioconcentration factors in sponge tissues were (in decreasing order) Zn > Ni > Mn > Fe > Cr relate to sediments and Fe > Ni > Mn > Cr > Zn relate to seawater. The PCA confirmed higher MTE concentrations in H. erectus compared to R. globostellata. Our results confirm that marine sponges can accumulate MTE to some extent and could be used as a tool for assessing metals contamination in lagoon ecosystems, particularly in New Caledonia, where 40% of the lagoon is classified as a UNESCO World Heritage Site.

Comparative Chemical Profiling and Antimicrobial/Anticancer Evaluation of Extracts from Farmed versus Wild Agelas oroides and Sarcotragus foetidus Sponges

Marine sponges are highly efficient in removing organic pollutants and their cultivation, adjacent to fish farms, is increasingly considered as a strategy for improving seawater quality. Moreover, these invertebrates produce a plethora of bioactive metabolites, which could translate into an extra profit for the aquaculture sector. Here, we investigated the chemical profile and bioactivity of two Mediterranean species (i.e., Agelas oroides and Sarcotragus foetidus) and we assessed whether cultivated sponges differed substantially from their wild counterparts. Metabolomic analysis of crude sponge extracts revealed species-specific chemical patterns, with A. oroides and S. foetidus dominated by alkaloids and lipids, respectively. More importantly, farmed and wild explants of each species demonstrated similar chemical fingerprints, with the majority of the metabolites showing modest differences on a sponge mass-normalized basis. Furthermore, farmed sponge extracts presented similar or slightly lower antibacterial activity against methicillin-resistant Staphylococcus aureus, compared to the extracts resulting from wild sponges. Anticancer assays against human colorectal carcinoma cells (HCT-116) revealed marginally active extracts from both wild and farmed S. foetidus populations. Our study highlights that, besides mitigating organic pollution in fish aquaculture, sponge farming can serve as a valuable resource of biomolecules, with promising potential in pharmaceutical and biomedical applications.

Uptake of aquaculture-related dissolved organic pollutants by marine sponges: Kinetics and mechanistic insights from a laboratory study

Besides the release of organic matter from uneaten feed and fish excreta, a considerable amount of deleterious chemicals may also end up into the marine environment from intensive aquaculture. A fraction of these pollutants remains freely dissolved and pose a threat to marine life due to increased bioavailability. Given the filter-feeding ability of sponges, we investigated the capacity of four ubiquitous Mediterranean species (Agelas oroides, Axinella cannabina, Chondrosia reniformis and Sarcotragus foetidus) in removing aquaculture-related dissolved organic pollutants. These included individual chemicals belonging to antibiotics (i.e., oxytetracycline), antifouling biocides (i.e., diuron and Irgarol 1051) and polycyclic aromatic hydrocarbons (i.e., 2,6-dimethylnapththalene, phenanthrene). The uptake of pollutants was assessed in vitro by exposing small sponge explants to each chemical for a period of 8 h. Additional "cleanup" experiments were performed for complex mixtures mimicking the dissolved organic material encountered in fish farms, such as filtrates of fish feed and excreta. All sponges exhibited a pronounced preference for lipophilic pollutants and a strong positive correlation was revealed between clearance rate and substrate hydrophobicity. Our best filter-feeder (i.e., A. oroides) was able to clear 10.0 ± 1.3 mL of seawater per hour and per gram of sponge, when exposed to 2,6-dimethylnapththalene. Active pumping was found to be the predominant mechanism dictating the assimilation of dissolved pollutants in all sponge species, as it was 3-10 times faster than pollutants' passive adsorption on sponges' pinacoderm. Additionally, the uptaken pollutants were shown to be strongly retained by sponges and they were hardly released back to seawater as a result of desorption or sponge excretory mechanisms. Our study corroborates that sponges are highly efficient in uptaking dissolved organic compounds and it offers new insights into the kinetics and mechanisms ruling this process.