Multiple Symbiodinium Strains Are Hosted by the Brazilian Endemic Corals Mussismilia spp.

Corals of genus Mussismilia (Mussidae) are one of the oldest extant clades of scleractinians. These Neogene relicts are endemic to the Brazilian coast and represent the main reef-building corals in the Southwest Atlantic Ocean (SAO). The relatively low-diversity/high-endemism SAO coralline systems are under rapid decline from emerging diseases and other local and global stressors, but have not been severely affected by coral bleaching. Despite the biogeographic significance and importance for understanding coral resilience, there is scant information about the diversity of Symbiodinium in this ocean basin. In this study, we established the first culture collections of Symbiodinium from Mussismilia hosts, comprising 11 isolates, four of them obtained by fluorescent-activated cell sorting (FACS). We also analyzed Symbiodinium diversity directly from Mussismilia tissue samples (N = 16) and characterized taxonomically the cultures and tissue samples by sequencing the dominant ITS2 region. Symbiodinium strains A4, B19, and C3 were detected. Symbiodinium C3 was predominant in the larger SAO reef system (Abrolhos), while Symbiodinium B19 was found only in deep samples from the oceanic Trindade Island. Symbiodinium strains A4 and C3 isolates were recovered from the same Mussismilia braziliensis coral colony. In face of increasing threats, these results indicate that Symbiodinium community dynamics shall have an important contribution for the resilience of Mussismilia spp. corals.

Effects of different biotic substrata on mussel attachment.

Surface colonization by invertebrates can be stimulated or inhibited by cues produced by biofilms, conspecifics or other macroorganisms. To study the effects of living substrata on the attachment of the brown mussel, Perna perna, two different approaches were employed: (1) mussels were distributed in sets of Petri dishes consisting of one sterile set (controls), three sets in which marine biofilms were allowed to develop in aquaria for 1, 7 or 15 days and another set that had been immersed in a natural marine environment for 1-day. There was no significant effect of biofilms on attachment, suggesting that neither age nor the source of the biofilm influenced attachment. (2) Mussels were suspended over PVC panels (controls) and over panels on which Balanus trigonus (Crustacea), Schizoporella errata (Bryozoa), Symplegma rubra or Didemnum speciosum (Ascidiacea) were present. Attachment was significantly higher on the controls and on B. trigonus than on colonial taxa such as S. rubra, S. errata and D. speciosum, probably due to antifouling defenses of these species. The results show that the composition of the biological substratum is an important factor affecting mussel behavior.

Latitudinal variation in phlorotannin contents from Southwestern Atlantic brown seaweeds.

Phlorotannins are primary and/or secondary metabolites found exclusively in brown seaweeds, but their geographic distribution and abundance dynamic are not very well understood. In this study we evaluated the phlorotannin concentrations among and within-species of brown seaweeds in a broad latitudinal context (range of 21°) along the Brazilian coast (Southwestern Atlantic), using the Folin-Ciocalteau colorimetric method. In almost all species (16 out of 17) very low phlorotannin concentrations were found (<2.0%, dry weight for the species), confirming reports of the typical amounts of these chemicals in tropical brown seaweeds, but with significantly distinct values among seven different and probably highly structured populations. In all 17 seaweed species (but a total of 25 populations) analyzed there were significant differences on the amount of phlorotannins in different individuals (t-test, p < 0.01), with coefficients of variation (CV) ranging from 5.2% to 65.3%. The CV, but not the total amount of phlorotannins, was significantly correlated with latitude, and higher values of both these variables were found in brown seaweeds collected at higher latitudes. These results suggest that brown seaweeds from higher latitudes can produce phlorotannins in a wider range of amounts and probably as response to environmental variables or stimuli, compared to low latitude algae.