• Energy Research

8 pages, 4 figures, 1 table Food availability strongly affects the ecology and physiology of coral and gorgonian species, as well as their resistance to stress factors. Since the resources available to these species must be allocated among the energy-costly processes of maintenance, regeneration, growth and reproduction, a reduction in food availability is expected to negatively influence these processes. Here, we show evidence that starvation induces a significant decrease in the gonadal volume produced by the Mediterranean asymbiotic gorgonian Paramuricea clavata, with a differential effect on male and female colonies. Fed and starved female colonies produced the same number of oocytes per polyp, but the oocytes were significantly smaller in the starved colonies. Conversely, the spermaries showed the same size in fed and starved male colonies, but fewer spermaries per polyp were produced in the starved colonies. The percentage of organic matter in the coenenchyme of the fed colonies did not change during the experiment, and its composition showed an increase in the relative amount of lipids. In contrast, the starved colonies showed a decrease in the percentage of organic matter, and a constant proportion of lipid. These results confirm a direct link between food availability and both reproductive output and biochemical composition in this organism, and underscore the potentially important role of food availability in explaining the spatial variability in the reproduction and energy storage of suspension feeders. © 2013 Elsevier B.V. This work was supported by the Consejo Superior de Investigaciones Cientificas (I3P-BPD2005 to A.G.); the Ministerio de Economía y Competitividad (RyC-2011-08134 to C.L. and RyC-2007-01327 to S.R.); the Agència de Gestió d'Ajuts Universitaris i de Recerca (FI-2010-03824 to N.V.); and the BENTOLARV project (CTM2009-10007) Peer Reviewed

We evaluated the effects of low pH on Corallium rubrum from aquaria experiments. Several colonies of C. rubrum were long-term maintained for 314 days in aquaria at two different pH levels (8.10 and 7.81, pHT). Calcification rate, spicule morphology, major biochemical constituents (protein, carbohydrates and lipids) and fatty acids composition were measured periodically. Exposure to lower pH conditions caused a significant decrease in the skeletal growth rate in comparison to the control treatment. Similarly, the spicule morphology clearly differed between both treatments at the end of the experiment, with aberrant shapes being observed only under the acidified conditions. On the other hand, while total organic matter was significantly higher under low pH conditions, no significant differences were detected between treatments regarding total carbohydrate, lipid, protein and fatty acid composition. However, the lower variability found among samples maintained in acidified conditions relative to controls, suggests a possible effect of pH decrease on the metabolism of the colonies. Our results show, for the first time, evidence of detrimental ocean acidification effects on this valuable and endangered coral species. Supplement to: Bramanti, Lorenzo; Movilla, Juancho; Guron, Maricel; Calvo, Eva; Gori, Andrea; Dominguez-Cariò, Carlos; Grinyó, Jordi; Lopez-Sanz, Angel; Martinez-Quintana, Angela; Pelejero, Carles; Ziveri, Patrizia; Rossi, Sergio (2013): Detrimental effects of ocean acidification on the economically important Mediterranean red coral (Corallium rubrum). Global Change Biology, 19(6), 1897-1908

AbstractSymbiotic scleractinian corals are particularly affected by climate change stress and respond by bleaching (losing their symbiotic dinoflagellate partners). Recently, the energetic status of corals is emerging as a particularly important factor that determines the corals’ vulnerability to heat stress. However, detailed studies of coral energetic that trace the flow of carbon from symbionts to host are still sparse. The present study thus investigates the impact of heat stress on the nutritional interactions between dinoflagellates and coral Stylophora pistillata maintained under auto- and heterotrophy. First, we demonstrated that the percentage of autotrophic carbon retained in the symbionts was significantly higher during heat stress than under non-stressful conditions, in both fed and unfed colonies. This higher photosynthate retention in symbionts translated into lower rates of carbon translocation, which required the coral host to use tissue energy reserves to sustain its respiratory needs. As calcification rates were positively correlated to carbon translocation, a significant decrease in skeletal growth was observed during heat stress. This study also provides evidence that heterotrophic nutrient supply enhances the re-establishment of normal nutritional exchanges between the two symbiotic partners in the coral S. pistillata, but it did not mitigate the effects of temperature stress on coral calcification.

ABSTRACTMarine 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.

17 pages, 12 figures, 3 tables The annual gonad development of a shallow (20 m depth) population of the Mediterranean gorgonian Eunicella singularis was found to be closely synchronized with that of a deep (60 m depth) population, but differences were observed in the gonadal output, with the shallow population producing more and larger sexual products. Lipid content in the shallow population showed a marked seasonality, peaking during summer. In contrast, lipid content remained persistently lower in the deep population. Fatty acids as well as C/N composition were also seasonal in the shallow population and more constant in the deep one. The isotopic composition (δ15N and δ13C) of the shallow colonies was similar to values observed for passive suspension feeders with symbiotic algae, whereas the deep colonies exhibited values similar to those of aposymbiotic passive suspension feeders that primarily feed on microzooplankton and particulate organic matter. These results highlight the importance of considering the depth-related variability among populations in order to achieve a better understanding of the ecology of sessile benthic suspension feeders A Gori was funded by a I3P contract of the Consejo Superior de Investigaciones Cientificas (Ref. I3P-BPD2005), N Viladrich was funded by a FI AGAUR research grant, L Bramanti was funded by Marie Curie IEF (Corgard, Project no. 221072), and S Rossi was funded by a Ramo´n y Cajal Contract (RyC-2007-01327). This work was supported by the BENTOLARV project (CTM2009-10007) Peer reviewed

AbstractClimate change threatens the structure and function of marine ecosystems, highlighting the importance of understanding the response of species to changing environmental conditions. However, thermal tolerance determining the vulnerability to warming of many abundant marine species is still poorly understood. In this study, we quantified in the field the effects of a temperature anomaly recorded in the Mediterranean Sea during the summer of 2015 on populations of two common sympatric bryozoans,Myriapora truncataandPentapora fascialis. Then, we experimentally assessed their thermal tolerances in aquaria as well as different sublethal responses to warming. Differences between species were found in survival patterns in natural populations,P.fascialisshowing significantly lower survival rates thanM.truncata. The thermotolerance experiments supported field observations:P.fascialisstarted to show signs of necrosis when the temperature was raised to 25–26 °C and completely died between 28–29 °C, coinciding with the temperature when we observed first signs of necrosis inM.truncata. The results from this study reflect different responses to warming between these two co-occurring species, highlighting the importance of combining multiple approaches to assess the vulnerability of benthic species in a changing climate world.