Marina Carreiro-Silva

The role of inorganic nutrients and herbivory in controlling microbioerosion of carbonate substratum

The effect of herbivore abundance and nutrients on microborer communities and their rates of bioerosion of Strombus gigas shells was studied using herbivore-exclusion cages and inorganic fertilizers at Glovers Reef, Belize. Microborers colonizing shells in each treatment were identified and their colonization rates were calculated from scanning electron microscopy of the boring casts. In all treatments the dominant microborer was the green alga Phaeophila sp. Cyanobacteria were most abundant within fertilized and fungi in unfertilized treatments. The highest microbioerosion rates and most distinctive microborer community were found on the treatment with both reduced herbivores and fertilization. All fertilized treatments had significantly higher bioerosion rates than unfertilized treatments. Treatments with macrograzer access had microbioerosion rates less than half the fertilized cages. Bioerosion rates in unfertilized treatments were lowest and not different with and without macrograzers. Consequently, increased nutrient concentrations on reefs have the potential to increase rates of microbioerosion and macrograzers can modify the composition and density of the microborer community.

Bioerosion: the other ocean acidification problem

&NA; Bioerosion of calcium carbonate is the natural counterpart of biogenic calcification. Both are affected by ocean acidification (OA). We summarize definitions and concepts in bioerosion research and knowledge in the context of OA, providing case examples and meta‐analyses. Chemically mediated bioerosion relies on energy demanding, biologically controlled undersaturation or acid regulation and increases with simulated OA, as does passive dissolution. Through substrate weakening both processes can indirectly enhance mechanical bioerosion, which is not directly affected by OA. The low attention and expert knowledge on bioerosion produced some ambiguous views and approaches, and limitations to experimental studies restricted opportunities to generalize. Comparability of various bioerosion and calcification rates remains difficult. Physiological responses of bioeroders or interactions of environmental factors are insufficiently studied. We stress the importance to foster and advance high quality bioerosion research as global trends suggest the following: (i) growing environmental change (eutrophication, coral mortality, OA) is expected to elevate bioerosion in the near future; (ii) changes harmful to calcifiers may not be as severe for bioeroders (e.g. warming); and (iii) factors facilitating bioerosion often reduce calcification rates (e.g. OA). The combined result means that the natural process bioerosion has itself become a “stress factor” for reef health and resilience.

Carrying behavior in the deep-sea crab Paromola cuvieri (Northeast Atlantic)

Observations of deep-sea homolids are becoming more common, but good-resolution imagery of these crabs in the natural environment is still scarce. Sixteen new in situ observations of Paromola cuvieri from various locations within the central and eastern groups of the Azores Archipelago (Northeast Atlantic) are described here based on video footage collected by two submersible vehicles. Crabs were found on coral gardens and deep-sea sponge aggregations, which are priority habitats of conservation importance under OSPARCOM. Diverse sessile megafauna were recorded (>59 taxa), including sponges, hydroids, corals, brachiopods, crinoids and oysters. Overall, 75% of the crabs were carrying live specimens of sessile invertebrates, mainly sponges and cold-water corals. Object selection shows to be a more complex process than previously thought, in which factors such as morphology, size and weight of objects and also palatability seem to be more important in the process of object selection than their availability.

Phosphorus and nitrogen effects on microbial euendolithic communities and their bioerosion rates

Cages and fertilizers were used at Glovers Atoll, Belize to test the relative importance of nitrogen (N) and phosphorus (P) to microbial euendolithic communities (bacteria, algae and fungi) and their bioerosion rates of Strombus gigas shells after 56-days of exposure. By the end of the experiment, the abundance of green algae was higher than cyanobacteria and fungi in N and N+P treatments, although green algae did not increase proportionally with increasing N concentrations, suggesting that green algae were co-limited by P and N. In contrast, cyanobacteria abundance increased with increasing P concentration, suggesting that cyanobacteria were P-limited. Fungi were not significantly affected by the addition of nutrients. Microbioerosion rates in the N and N+P treatments were 2-times greater than rates in the P treatment and 15-times greater than the control treatment. Results demonstrate that increased nutrient concentrations on coral reefs may increase microbioerosion rates, and variations in nutrient ratios can modify microborers community composition.

An Eguchipsammia (Dendrophylliidae) topping on the cone

A reef formed by corals of the azooxanthellate scleractinian genus EguchipsammiaCairns, 1994 (Dendrophylliidae), identified following the morphological descriptions by Zibrowius (1980) and Cairns (2000), was discovered in July 2013 off the Faial-Pico Channel (Azores, Northeast Atlantic). This is the first record of such an extensive living Eguchipsammia framework and the first major discovery by the RebikoffNiggeler Foundation with its recently-inaugurated manned submersible Lula 1000. The recently located reef was found at 280–300 m depth, on the very top of a partially collapsed and rejuvenated volcanic cone (Fig. 1a). This dense framework covers an estimated 1,000 m, with the living bright yellow polyps standing out from the dead skeletons (Fig. 1b–d). The underlying substrate is partially visible, suggesting that the reef is less than 1 m thick. The distribution range of the genus Eguchipsammia in the Atlantic Ocean previously included multiple localities in the Gulf of Mexico and Caribbean, at depths between 9 and 300 m, and southwestern Europe, from the Coral Patch Seamount to the Celtic Sea at depths ranging between 330 to 960 m (Cairns 2000; Wienberg et al. 2013). The present record attests the presence of the genus in the central North Atlantic, filling the gap within its amphi-Atlantic distribution

Zoantharians (Hexacorallia: Zoantharia) associated with cold-water corals in the azores region: New species and associations in the deep sea

Zoantharians are a group of cnidarians that are often found in association with marine invertebrates, including corals, in shallow and deep-sea environments. However, little is known about deep-sea zoantharian taxonomy, specificity and nature of their associations with their coral hosts. In this study, analyses of molecular data (mtDNA COI, 16S and 12S rDNA) coupled with ecological and morphological characteristics were used to examine zoantharian specimens associated with cold-water corals at depths between 110 and 800 m from seamounts and island slopes in the Azores region. The zoantharians examined were found living in association with stylasterids, antipatharians and octocorals. From the collected specimens, four new species were identified: (1) Epizoanthus martinsae sp. n. associated with the antipatharian Leiopathes sp.; (2) Parazoanthus aliceae sp. n. associated with the stylasterid Errina dabneyi (Pourtales, 1871); (3) Zibrowius alberti sp. n. associated with octocorals of the family Primnoidae (Paracalyptrophora josephinae (Lindstrom, 1877)) and the family Plexauridae (Dentomuricea aff. meteor Grasshoff, 1977); (4) Hurlizoanthus hirondelleae sp. n. associated with the primnoid octocoral Candidella imbricata (Johnson, 1862). In addition, based on newly collected material, morphological and molecular data and phylogenic reconstruction, the zoantharian Isozoanthus primnoidus Carreiro-Silva, Braga-Henriques, Sampaio, de Matos, Porteiro & Ocana, 2011, associated with the primnoid octocoral Callogorgia verticillata (Pallas, 1766), was reclassified of as Zibrowius primnoidus comb. nov. The zoantharians, Z. primnoidus comb. nov., Z. alberti sp. n. and H. hirondelleae sp. n. associated with octocorals showed evidence of a parasitic relationship, where the zoantharian progressively eliminates gorgonian tissue and uses the gorgonian axis for structure and support, and coral sclerites for protection. In contrast, the zoantharian P. aliceae sp. n. associated with the stylasterid E. dabneyi and the zoantharian E. martinsae sp. n. associated with the antipatharian Leiopathes sp., appear to use the coral host only as support with no visible damage to the host. The monophyly of octocoral-associated zoantharians suggests that substrate specificity is tightly linked to the evolution of zoantharians.

Assessment of Cu sub-lethal toxicity (LC50) in the cold-water gorgonian Dentomuricea meteor under a deep-sea mining activity scenario

Previous aquaria-based experiments have shown dissolution and leaching of metals, especially copper (Cu), from the simulated sediment plumes generated during mining activities resulting in a pronounced increase of Cu contamination in the surrounding seawater. Metals are bioavailable to corals with food, through ingestion (particulate phase) and through tissue-facilitated transport (passive diffusion). With corals being particularly vulnerable to metal contamination, resuspension of metal-bearing sediments during mining activities represents an important ecological threat. This study was undertaken to evaluate the impact of acute copper exposure (LC50;96 h) on the survival of the cold-water octocoral Dentomuricea aff. meteor. The experimental design was divided in two stages. In stage one, a Cu range-finding toxicity test was performed using Cu dilutions in filtered seawater with concentrations of 0 (control); 60; 150; 250; 450; 600 μg/L. Coral mortality was investigated visually based on the percent surface area of tissue changing from natural yellow colour to black colour indicative of tissue necrosis and death. In stage two, we used the results obtained in the range-finding experiment, to define sub-lethal Cu exposure treatments and exposed D. meteor to Cu concentration of 0 (control); 50; 100; 150; 200; 250 μg/L for 96 h. The corals physical conditions were inspected daily and seawater conditions recorded. Corals were considered dead when all of their tissue turned black. The LC50 value was calculated with regression analysis following Probits methodology. Our results indicate that Cu LC50;96 h for the octocoral D. meteor is 137 μg/L.

Viewpoints in bioerosion research—are we really disagreeing? A reply to the comment by Silbiger and DeCarlo (2017)

A recent literature review by Schönberg et al. (2017) on bioerosion under ocean acidification and global change led to a detailed comment by Silbiger and DeCarlo (2017). We use the opportunity to reply to this comment, to correct misinterpreted data and to further stimulate the discussion in bioerosion science. We still believe that our paper and the included method discussion were timely. Most discussed studies captured only a partial bioeroder community, for which upscaling and generalization remains difficult. However, after re-visiting Silbiger et al. (2014) we would like to propose a new interpretation: Their net bioerosion/accretion did not change along a natural gradient, but may have responded to localized pH “anomalies”. In general, we encourage future authors to more often consider that biological responses can be non-linear and discuss this in the context of bathymetry-related variables. We agree with Silbiger and DeCarlo (2017) in that conclusions should be reached by methods and data relevant to that particular situation and by sufficient sample sizes, all being strongly influenced by the research design and the targeted bioeroder taxa. We further agree that field studies are not automatically flawed, but needed to confirm controlled aquarium experiments and to assess multiple factor interactions in natural settings.