Length-weight relationships of eight fish from seagrass meadows in Wenchang,China

The length-weight relationships (LWRs) were studied for eight seagrass fish from Wenchang, China, using gill nets (150*1 m, mesh size 0.5 cm), including Gerres oblongus, Ambassis kopsii, Halichoeres nigrescens, Sillago aeolus, Yongeichthys criniger, Oxyurichthys tentacularis, Lethrinus haematopterus and Hypoatherina tsurugae, in November 2017, March and August 2018. Results suggest that mean LWR parameters b for these eight seagrass fish varied from 2.801 for L. haematopterus to 3.640 for A. kopsii, and r² valued from .950 for L. haematopterus to 0.993 for H. nigrescens. This study will help us to better understand the ecological parameters these seagrass fish.     

Field studies of seahorse population density,structure and habitat use in a semi-closed north-eastern Mediterranean marine area (Stratoni,North Aegean Sea)

The present study was carried out in the marine area of Stratoni, Greece, where two seahorse species are present (Hippocampus hippocampus and Hippocampus guttulatus). Two surveys were conducted (September 2016 and May 2019) to gather information regarding seahorse species' abundance, distribution and habitat characteristics. Four different seahorse natural and artificial habitat types were identified. The results revealed that the presence of H. hippocampus was relatively high, especially at sites with artificial structures, whereas the presence of H. guttulatus was rare. Data collected can provide baseline information for future population assessments.     

Evidence for matrotrophy in the viviparous sea cucumber Leptosynapta clarki: A role for the genital haemal sinus?

Summary

Viviparity, where the embryos develop in the female reproductive system, is a rare form of reproduction in marine invertebrates, being described in only 14 species of echinoderm. In the intraovarian brooding sea cucumber, Leptosynapta clarki Heding 1928 (cf., Sewell et al. 1995), we used direct evidence (changes in energetic content) to show that significant additional nutrients are provided to the embryos during viviparous development (matrotrophy). In the transition from a structure used to produce gametes to a long-term brooding structure there are visual, histological and transmission electron microscopy (TEM) changes in the structure of the ovarian wall. Changes occur primarily in the cells of the visceral peritoneum and involve an increase in size of the connective tissue/genital haemal sinus (CT/GHS). In the latter part of the brooding period the visceral peritoneum returns to a flattened form, and new oocytes develop along the tubule wall. Similar changes in the intraovarian brooding sea cucumber Oneirophanta mutabilis affinis lead us to suggest that there is a role for the genital haemal sinus in providing nutrition during the brooding period in viviparous echinoderms. Future research is suggested to focus on changes in the ovarian wall structure during the different phases of reproduction (gamete production/brooding) in these species.     

A simple method to evaluate the potential for degradation of antifouling biocides

A simple method to measure the degradation of antifouling biocides is described which measures the loss of biocidal activity from seawater by bioassay. The bioassay employs either the ship‐fouling diatom Amphora or the brine shrimp Anemia. Loss of bioaclivity from sterile seawater indicates abiotic degradation whilst loss of bioactivity from natural seawater indicates biodegradation. Results are presented for three biocides, viz. the trihalomethylthio compound, N‐dichlorofluoromethylthio‐N’,N'‐dimethyl‐N‐phenyl‐sulphamide (Preventol A4S), di‐n‐octylamine, and the isothiazolone compound 4,5‐dichloro‐2‐n‐octyl‐4‐isothiazolin‐3‐one (Sea‐Nine 211).     

Population recovery of the sea urchin Lytechinus variegatus in a seagrass flat (Araruama Lagoon,Brazil): the role of recruitment in a disturbed environment

Summary

The size, structure, and density of a population of Lytechinus variegatus were recorded from a shallow seagrass bed (Halodule wrightii) at 40-day intervals from April 1994 to April 1995. A local mass mortality was observed in May 1994. The density declined from 0.57±0.10 to 0.06±0.05 ind.m^?2, mean size declined from 37.6±0.49 to 16.2±2.14 mm and maximum size from 75 to 40 mm. Ten months after mortality, the maximum and mean sizes had returned to initialvalues, but density had not (0.10±0.03 ind.m^?2). A second, smaller mass mortality occurred in April 1995. High values of gonad index were recorded before mortality (9.40±5.97) and after population recovery (11.96±5.74). Recruitment was continuous throughout the year, but reached a peak from August to October. This can he related to the patterns of upwelling in the region. Mass mortality is probably an annual event in this population that can be correlated with the occurrence of low tides during daytime in the fell. The population can recover during the summer when low tides occur during the night. The massive input of recruits prevents extinction of the population during the season of high mortality. Population recovery depends on the magnitude of recruitment.     

Molecular data reveal cryptic lineages within the northeastern Atlantic and Mediterranean small mussel drills of the Ocinebrina edwardsii complex (Mollusca: Gastropoda: Muricidae)

We used a molecular phylogenetic approach to investigate species delimitations and diversification in the mussel drills of the Ocinebrina edwardsii complex by means of a combination of nuclear (internal transcribed spacer 2, ITS2) and mitochondrial [cytochrome oxidase subunit I (COI) and 16S] sequences. Our sample included 243 specimens ascribed to seven currently accepted species from 51 sites. Five of the samples were from either the type locality of a nominal species or a close nearby locality (O. edwardsii from Corsica, O. carmelae and O. piantonii from the Kerkennah Islands, O. hispidula from the Gulf of Gabès and O. leukos from the Canary Islands), one from the inferred original locality (O. ingloria from Venice Lagoon), and specimens assigned in the recent literature to O. nicolai. We used a combination of distance‐ and tree‐based species delimitation methods to identify Molecular Operational Taxonomic Units (MOTUs) to compare with the a priori species identifications. The consensus tree obtained by BEAST on the COI alignment allows the recognition of several distinct clades supported by the three species delimitation methods employed. The eight‐MOTUs scenario, shared by the Automatic Barcode Gap Discovery (ABGD) and Generalized Mixed Yule‐Coalescent (GMYC) methods, comprises the following major clades: clade A contains the south Tunisian species Ocinebrina piantonii Cecalupo, Buzzurro & Mariani from which the sympatric taxon O. carmelae Cecalupo, Buzzurro & Mariani (new synonym) cannot be separated; clades B and C bring together all populations from the Aegean Sea and some from the Ionian Sea, respectively; clade D groups, on the one hand, the south Tunisian samples morphologically assigned to O. hispidula Pallary and, on the other, Atlantic and Alboran Sea samples (including the Canarian taxon O. leukos Houart); clade E includes a sample from the type locality of O. edwardsii and several samples from the Tyrrhenian Sea; clades F and G correspond to a few samples from the Venice Lagoon and the Tyrrhenian Sea, respectively; clade H groups the bulk of samples from the Adriatic Sea, including samples from the Venice Lagoon morphologically identified as Ocinebrina ingloria (Crosse), and some from the Ionian Sea. No final conclusions could be reached to reconcile the currently recognized morphological taxa with the clades suggested by the COI data. The geographical structure proposed by the mitochondrial markers is similar to that found in other marine invertebrates and partially corresponds to the species defined by shell characters. We propose here a framework for the revision of the Ocinebrina edwardsii species complex, suggesting a geographical pattern for the diversification of this group in the studied area. © 2013 The Linnean Society of London     

Growth on Geological Time Scales in the Antarctic Cryptoendolithic Microbial Community

In the process of biogenous weathering of Beacon sandstone in the McMurdo Dry Valleys (Ross Desert), Antarctica, periods of microbial growth, on the time scale of 103-104 years, alternate with sudden exfoliation events. The present study addressed the question of whether microbial growth is continuous between exfoliation events or whether each exfoliation is followed by a period of comparatively rapid growth and then an extended period of steady state. The color intensity (Munsell lightness value) of the rock surface is an indicator of relative age of the crust within the exfoliation cycle, permitting measurement of changes in microbial biomass on a geological time scale. Results indicate that microbial growth is continuous and that exfoliation occurs when the microbial biomass reaches the carrying capacity of the cryptoendolithic habitat.     

Niche Separation of Methanotrophic Archaea (ANME-1 and -2) in Methane-Seep Sediments of the Eastern Japan Sea Offshore Joetsu

In this study, we investigated the diversity and spatial distribution of anaerobic methanotrophic archaea (ANMEs) in sediments of a gas hydrate field off Joetsu in the Japan Sea. Distribution of ANMEs in sediments was identified by targeting the gene for methyl coenzyme M reductase alpha subunit (mcrA), a phylogenetically conserved gene that occurs uniquely in methanotrophic and methanogenic archaea, in addition to 16S rRNA genes. Quantitative PCR analyses of mcrA genes in 14 piston core samples suggested that members of ANME-1 group would dominate AOM communities in sulfate-depleted sediments, even below the sulfate-methane interface, while ANME-2 archaea would prefer to populate in shallower sediments containing comparatively higher sulfate concentrations. These results suggest that, although the potential electron acceptors in sulfate-depleted habitats remain elusive, the niche separation of ANME-1 and -2 may be controlled by in situ concentration of sulfate and the availability in sediments.     

Lower Abundance of Ammonia-Oxidizing Archaea Than Ammonia-Oxidizing Bacteria Detected in the Subsurface Sediments of the Northern South China Sea

Diversity and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in samples of the northern South China Sea subsurface sediment were assessed by analyzing the amoA gene sequences retrieved from the samples. The microbial diversity was assessed using rarefaction and phylogenetic analyses. The deep-sea subsurface sediments harbored diverse and distinct AOA and AOB communities, but the abundance of AOA was lower than that of AOB, consistent with many other studies about bacteria and archaea in subsurface sediments. Diversity of AOA shown in the OTUs and Shannon index was correlated with the concentration of nitrite in the Pearson analysis, but no obvious relationships between the diversity or abundance of AOB and the physicochemical parameters could be identified in the present study, indicating the concentration of ammonium may not be an important factor to determine the diversity and abundance of ammonia-oxidizing prokaryotes in the subsurface sediments. Additionally, Nitrosomonas-like AOB was found to be dominant in subsurface sediments of the northern South China Sea showing a different adaption strategy comparing with some Nitrosospira-like AOB lineages. Concentration of nitrite was correlated with diversity of AOA, but no correlations between diversity and abundance of AOB and the physicochemical parameters were established in the study. Supplementary materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the free supplemental files.