Volume 62, Issue 4

Few studies have investigated the long-term temporal dynamics of seagrass beds, especially in Southeast Asia. Remote sensing is one of the best methods for observing these dynamic patterns, and the advent of deep learning technology has led to recent advances in this method. This study examined the feasibility of applying image classification methods to supervised classification and deep learning methods for monitoring seagrass beds. The study site was a relatively natural seagrass bed in Hat Chao Mai National Park, Trang Province, Thailand, for which aerial photographs from the 1970s were available. Although we achieved low accuracy in differentiating among various densities of vegetation coverage, classification related to the presence of seagrass was possible with an accuracy of 80% or more using both classification methods. Automatic classification of benthic cover using deep learning provided similar or better accuracy than that of the other methods even when grayscale images were used. The results also demonstrate that it is possible to monitor the temporal dynamics of an entire seagrass area, as well as variations within sub-regions, located in close proximity to a river mouth.

For the first time, distribution and abundances (cells per gram of fresh macrophyte weight) of potentially toxic benthic dinoflagellates were studied around Guadeloupe (20 sites) and Martinique (six sites) islands (Lesser Antilles, Caribbean Sea). Benthic dinoflagellates were identified at the genus level and cell counts were undertaken on different host species of macroalgae and seagrasses. Abundance values of potentially toxic benthic dinoflagellates were one order of magnitude higher in Guadeloupe than in Martinique. The highest abundances of benthic dinoflagellates were found in the northern part of Guadeloupe Island, while their distribution was more homogeneous in Martinique. Ostreopsis was the dominant genus in Guadeloupe and Martinique. Regarding biotic substrate preferences, Phaeophyceae hosted the highest total abundances of benthic dinoflagellates on both islands, while the lowest total abundances were observed on Ulvophyceae in Guadeloupe and Florideophyceae in Martinique. The genus Gambierdiscus , known as the causal agent of the ciguatera fish poisoning (CFP), developed on all macrophyte groups on both islands without showing any preferences towards biotic substrates. The presence of this potentially harmful dinoflagellate genus in both islands could explain the existence of local cases of CFP in Guadeloupe and Martinique islands.

Standing stocks of the calcifying algae, Halimeda and Penicillus , have remained stable over the 10 years surveyed (2007–2017) in Florida Bay (USA), a subtropical lagoon. The maximum contribution of calcium carbonate (CaCO 3 ; 779.75 g m −2 ) was lower compared to tropical lagoons. Halimeda was more abundant and had higher inorganic:organic carbon ratios compared to Penicillus . The abundance of Penicillus varied across the surveyed sites, Sprigger Bank, Bob Allen Keys, and Duck Key, while its inorganic:organic carbon ratios did not vary significantly. Our long-term study provides a critical baseline that can help understand fluctuations in carbonate sediment production by calcareous algae in subtropical coastal waters.

Halimeda is a genus of green seaweed showing high morphological plasticity. Studies using molecular markers for species delimitations and phylogenetics have revealed cryptic diversity and new species throughout the world. Seven species of Halimeda are currently recognized in Brazil. The present study describes the new species Halimeda soniae Ximenes, Oliveira-Carvalho, M. E. Bandeira-Pedrosa et Cassano sp. nov. to accommodate the taxon previously identified as Halimeda aff. gracilis for Brazil. Samples of H. soniae were collected in Espírito Santo State (southeastern Brazil), and plastid gene sequences of tuf A and rbc L were obtained. Phylogenetic analyses showed that H. soniae belongs to Section Pseudo-opuntia , together with Halimeda gracilis and Halimeda lacrimosa ; the three species have overlapping morpho-anatomical features. Phylogenetic analyses suggest that H. gracilis is restricted to the Indo-Pacific Ocean, whereas the other two species appear to be restricted to the Atlantic. Additional research on Caribbean specimens will be necessary to resolve the taxonomic position of the taxa named as H. lacrimosa and H. gracilis in that region. Based on our results, H. gracilis does not occur in the Brazilian marine flora.

Five species of benthic marine algae (Phaeophyceae: Lobophora littlerorum ; Rhodophyta: Meristotheca cylindrica, Naccaria corymbosa, Xiphosiphonia pinnulata and Dipterosiphonia reversa ) represent new distribution records from the coastal waters surrounding Puerto Rico in the northern Caribbean Sea. The latter two species are now reported for the first time from the western Atlantic Caribbean.

The monotypic red algal parasite genus Spyridiocolax was proposed from material from the coast of Espírito Santo to accommodate Spyridiocolax capixabus , endemic from Brazil. The species is rare, and we performed a morphological reappraisal and the first molecular characterization of S. capixabus . Parasite specimens growing on Spyridia clavata were collected in the type locality, Itaoca Beach, Espírito Santo. Spyridiocolax capixabus forms colorless warts on the branches of S. clavata , and the secondary pit connections were described for the first time. Male, female and tetrasporophytic structures were observed growing in the same host plant. The plastid rbc L sequences of parasite and host were identical. A divergence of one nucleotide was found to the nuclear SSU rRNA gene, suggesting that the parasite retains the chloroplast of its host. Both plastidial and nuclear phylogenies supported the close relationship of S. capixabus and S. clavata . The data obtained corroborate other studies with rhodophycean parasites, which show morphological and molecular similarities between parasites and hosts. To maintain the monophyly of the host genus, the transfer of S. capixabus to Spyridia is proposed here on the basis of morphological and molecular evidence. Our study constitutes a starting point for reinvestigating the red algal parasites in Brazil.

The fourth addendum to Schneider and Wynne’s 2007 “A synoptic review of the classification of red algal genera a half century after Kylin’s 1956 ‘ Die Gattungen der Rhodophyceen ’” is presented, covering the names of genus- and higher-level taxa added or modified since our third addendum ( Bot. Mar. 59: 397–404). Since that synopsis, we added 21 new genera in a first addendum, 27 in the second, and 40 in the third, demonstrating the increasing amount of genetic work over more than a decade. In this fourth addendum, we add 58 new genera to the list of red algae as well as many new taxa in the hierarchical framework over the past 3 years. Based upon molecular sequencing, other genera reinstated from synonymy studies are included.

The stoloniferous hydrozoan Obelia geniculata commonly colonizes macroalgae such as Saccharina japonica . Each Obelia colony consists of thread-like hydrorhizae attached to the seaweed thallus. The early signaling proteins of epiphytic contamination can be identified using proteomics. To isolate these early signals, parts of the thallus proximal to the hydrozoans were separated from beneath the colony front and from healthy tissue. From the proteomic profiles of S. japonica , we detected 110 protein spots from tissue proximal to hydrozoan colonies (56 increased, 53 decreased, and 1 unchanged in expression relative to healthy tissue) and 133 spots from tissue at the colony front (67 increased, 60 decreased, and 6 unchanged in expression). Of the proteins with increased and decreased expression, SIPA1L1 and actin increased strongly only in the proximal tissues, while NEK2 kinase decreased. CIPK20 and SIPA1L2 increased markedly in both the colony-front and proximal tissues, while CaMK2N2 and GK25369 decreased in both tissues. ATPase β, ADA, kinesin, and HECT domain proteins increased only in the colony-front tissues. Among them, SIPA1L2 increased strongly in both the thallus tissues proximal to the hydrozoans and those beneath the colony front, but was not expressed in response to bryozoan infection.

The phenolic content of Spartina maritima was investigated using chromatographic and spectroscopic techniques. Aqueous methanolic extracts were prepared from plant collected in different seasons in the Bay of Arcachon (French Atlantic coast). High performance liquid chromatography (HPLC) with diode array detection (DAD) coupled with mass spectrometry allowed identification of four major phenolics in the aerial tissue, all belonging to the C -glycosidic-flavonoid class. They were isolated from the crude extracts, and their structures were assigned to isovitexin, isoscoparin and their respective 2″- O -glucosides on the basis of NMR, mass and UV spectroscopies. The seasonal variation of the flavonoid content was quantified over the period January 2013 to May 2015. The total concentration found ranged from 1.73 to 4.60 mg g −1 dry wt for isovitexin derivatives, and 0.88–2.66 mg g −1 dry wt for isoscoparin derivatives. The phenolic content of the rhizomes was very low and mainly dominated by coumaric acid (0.03–0.08 mg g −1 ), along with ferulic acid (≤0.06 mg g −1 ). The lack of significant concentrations of flavonoids in the rhizome contrasts with the aerial tissue. This work constitutes the first phenolic profiling of S. maritima and should provide a foundation for further studies, considering the reported biological activities of C -glycosidic flavonoids, and the lack of knowledge of the phenolic chemistry of the genus Spartina .