![]() In this study, we quantified OA-induced changes in early life history patterns (larval mortality and condition, settlement rate, recruit survival, and size) in the non-calcifying breadcrumb sponge Halichondria panicea collected from a temperate intertidal site in the California Current Large Marine Ecosystem. In particular, we know relatively little about how OA will impact temperate sponges, which will experience more extreme low pH conditions than tropical species. Ocean acidification (OA) is predicted to result in reduced survival, growth, reproduction, and overall biodiversity of marine invertebrates, and yet we lack information about the response to OA of some major groups of marine organisms. Continue reading ‘Sponge organic matter recycling: reduced detritus production under extreme environmental conditions’ Our findings provide new insights into how important trophic pathways may be affected by changing ocean conditions. ![]() We found that while sponges experienced acidification and low dissolved oxygen at low tide in both sampling years, a change in organic carbon recycling whereby sponges stopped producing detritus (i.e., the sponge loop) was only found when sponges also experienced higher temperature in 2020. During two years (20), we measured the organic carbon, nutrient recycling, and photosynthetic activity of the massive HMA, photosymbiotic sponge Rhabdastrella globostellata at the natural laboratory of Bouraké in New Caledonia, where the physical and chemical composition of seawater regularly change according to the tide. Despite the importance of this loop, little is known about how these cycles will be impacted by future environmental conditions. Many sponges are known to consume dissolved organic carbon and transform this into detritus, which moves through detrital food chains and eventually to higher trophic levels via what is known as the sponge loop. Sponges are a key component of coral reef ecosystems and play an important role in carbon and nutrient cycles. The sponge loop pathway was disrupted during low tide, which correlated with extreme acidification, deoxygenation and warming seawater.Photosynthetic activity of sponge symbionts was negatively affected during extreme environmental conditions.The photosymbiotic HMA sponge Rhabdastrella globostellata was able to cope with extreme acidification and deoxygenation seawater.Sponge metabolism was measured at the natural laboratory of Bouraké where sponges are naturally exposed to extreme conditions associated with tidal phase.Continue reading ‘Future ocean conditions induce necrosis, microbial dysbiosis and nutrient cycling imbalance in the reef sponge Stylissa flabelliformis’ flabelliformis is unlikely to be disrupted by future OA but will be deeply impacted by temperatures predicted for 2100 under a “business-as-usual” carbon emission scenario. Putative defence against reactive oxygen species was greater at 31.5 ☌, perhaps as microorganisms capable of resisting temperature-driven oxidative stress were favoured. Crucially, the dysbiosis annihilated the potential for ammonia detoxification, possibly leading to accumulation of toxic ammonia, nutrient imbalance, and host tissue necrosis. The potential for microbially-driven nitrogen and sulphur cycling was reduced, as was amino acid metabolism. OW weakened sponge-microbe interactions, with a reduced capacity for nutrient exchange and phagocytosis evasion, indicating lower representations of stable symbionts. Major taxonomic shifts included a complete loss of archaea, reduced proportions of Gammaproteobacteria and elevated relative abundances of Alphaproteobacteria. Furthermore, OA (pH 7.6 versus pH 8.0) had no impact, while OW (31.5 ☌ versus 28.5 ☌) caused tissue necrosis, as well as dysbiosis and shifts in microbial functions in healthy tissue of necrotic sponges. We found no interactive effect on the host health or microbiome. Here we present a comprehensive view of the consequences of simultaneous OW and OA for the tropical sponge Stylissa flabelliformis. Ocean warming (OW) and ocean acidification (OA) can impact host health and associated microbiome, but few studies have investigated these effects, which are generally studied in isolation, on a specific component of the holobiont. Oceans are rapidly warming and acidifying in the context of climate change, threatening sensitive marine biota including coral reef sponges.
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