Marine Biodiversity最新文献

The quantitative assessment of fish larvae is a key issue in determining the composition of marine food webs. However, there is still a gap in this field regarding how to efficiently sample larvae, particularly in warm and nutrient-poor waters. We evaluated the differences found in larvae caught with two mesh size nets (330 and 500 μm) sampled in the open ocean: shelf break and slope (equatorial SW Atlantic). In total, 792 larvae were sampled, representing 14 orders and 55 families. Overall, larval density was low, and no difference in density was detected between the two net sizes (ind.100 m⁻³). However, a greater number of taxa (46 families) were found in the smaller net (300 μm) than in the larger (500 μm) (37). Moreover, 30.2% of families were found only in the 330 μm net, whereas 9.4% were found only in the 500 μm net. A total of 60.4% of taxa were common to both nets. Gonostomatidae, Paralepididae, Scombridae, Carangidae, Phosichthyidae, and the reef-associated families Scaridae and Gobiidae were the most abundant taxa in the smaller net. In contrast, Myctophidae, Gobiidae, Gonostomatidae, and Stomiidae were the most abundant in the larger net. We highlight mesophotic reefs and seamounts in the South Atlantic for adult spawning and larval growth, emphasizing the need for conservation actions and appropriate fisheries management. Finally, our results also indicate that the combination of different mesh net sizes provides a better baseline of fish larval diversity in warm and oligotrophic oceans.

Abstract

Interest in deep-sea mining for polymetallic nodules as an alternative source to onshore mines for various high-technology metals has risen in recent years, as demands and costs have increased. The need for studies to assess its short- and long-term consequences on polymetallic nodule ecosystems is therefore also increasingly prescient. Recent image-based expedition studies have described the temporal impacts on epi-/megafauna seafloor communities across these ecosystems at particular points in time. However, these studies have failed to capture information on large infauna within the sediments or give information on potential transient and temporally limited users of these areas, such as mobile surface deposit feeders or fauna responding to bloom events or food fall depositions. This study uses data from the Peru Basin polymetallic nodule province, where the seafloor was previously disturbed with a plough harrow in 1989 and with an epibenthic sled (EBS) in 2015, to simulate two contrasting possible impact forms of mining disturbance. To try and address the shortfall on information on transient epifauna and infauna use of these various disturbed and undisturbed areas of nodule-rich seafloor, images collected 6 months after the 2015 disturbance event were inspected and all Lebensspuren, ‘traces of life’, were characterized by type (epi- or infauna tracemakers, as well as forming fauna species where possible), along with whether they occurred on undisturbed seafloor or regions disturbed in 1989 or 2015. The results show that epi- and endobenthic Lebensspuren were at least 50% less abundant across both the ploughed and EBS disturbed seafloors. This indicates that even 26 years after disturbance, sediment use by fauna may remain depressed across these areas.

Polychaetes are annelids predominantly marine and constitute an important part of marine communities. The genus Alitta, of the family Nereididae, comprises nine recognized species, including Alitta succinea, considered cosmopolitan. The species was first described from the Helgoland (Germany) and has been recorded on the Brazilian coast. However, evidence suggests that A. succinea might be a complex of cryptic species. The aim of this short communication is molecularly analyzing specimens of Alitta succinea to ascertain the status of the species in Brazil. The study encompassed molecular analyses of COI and 16S sequences using data obtained from eight specimens collected from three localities at Rio de Janeiro and seven specimens collected from Santa Catarina, in addition to available data from GenBank and BOLD Systems. Molecular analyses clustered specimens from Brazil, the type locality and other localities in the same clade, reinforcing the status of A. succinea as an invasive species. However, additional studies, including more extensive molecular and morphological analyses, are necessary to clarify the distribution of the Alitta succinea along the Brazilian coast.

Stony coral tissue loss disease (SCTLD) is a highly contagious disease, causing mass coral mortalities in the Atlantic/Caribbean since 2014. In Puerto Rico, SCTLD was first reported in 2019 off the east coast, spreading to the north-central region by early February 2021. Benthic surveys were conducted at Cueva del Indio (CI) and Peñón de Mera (PM) off Arecibo to (1) quantify coral species-specific SCTLD prevalence using four 10 × 1-m² belt transects and (2) acquire time-series photo and video surveys to illustrate the impact of SCTLD, to evaluate coral species-specific susceptibilities, and estimate the timing of onset in Arecibo. A total of 650 corals in six species (Pseudodiploria strigosa, P. clivosa, Montastraea cavernosa, Siderastrea siderea, Orbicella annularis, Porites astreoides) were recorded inside the belt transects at both sites. SCTLD prevalence varied between 54% (P. strigosa) and 35.5% (M. cavernosa) at CI, and between 87.5% (S. siderea) and 25% (O. faveolata) at PM. Photo/video surveys revealed that SCTLD caused partial mortality in 11 species and full mortality in P. strigosa, P. clivosa, S. siderea, M. cavernosa, and Dendrogyra cylindrus. The results are discussed in view of prior research and contribute to understanding the spread and impact of SCTLD around Puerto Rico, which can be applied to predict its spread to other regions in the Caribbean.

Genetic diversity studies not only improve the understanding of the wild genetic resources of species but also provide a theoretical basis for the protection, development, and utilization of species and formulation of reasonable protection measures. Fishing pressure on the near threatened fish Harpadon nehereus has recently increased, leading to the aging and miniaturization of its population. We determined the gene sequences of mitochondrial cytochrome b (Cytb) and nuclear recombination-activating 1 (RAG1) in eight populations of H. nehereus in the Northwest Pacific, analyzed their genetic diversity levels, and compared the effectiveness of these two markers for analyzing genetic diversity and population structure. Sequence analysis of Cytb revealed that the eight populations showed low haplotype diversity (H_d = 0.110–0.356) and low nucleotide diversity (pi = 0.00015–0.00053). No significant genetic differentiation was observed among the populations (F_st = − 0.0197–0.000, P > 0.05). The haplotype network diagram did not exhibit evident geographical clustering or a pedigree structure. Molecular variance analysis revealed that variation primarily occurred within populations. Further comparative analysis of the RAG1 and Cytb sequences revealed two differences. RAG1 showed high haplotype diversity (H_d = 0.780–0.900) and low nucleotide diversity (pi = 0.00355–0.00463). The genetic differentiation index value revealed a significantly low level of genetic differentiation among some populations.

Marine karst ecosystems exist at the land-sea interface and are characterised by underwater formations sculpted over time by the action of seawater. Submerged caves and crevices of these ecosystems host a rich array of marine life of which sponges are among the most abundant and diverse components. In the present study, we describe elements of the sponge fauna sampled from a unique karst ecosystem at a remote island, Orchid Island, off the southeastern coast of Taiwan. The present study includes several understudied sponge taxa, including sclerosponges (Acanthochaetetes wellsi, and Astrosclera willeyana) and several lithistid species from dark, shallow-water caves. Prokaryotic communities were obtained from a total of 22 demosponge species, of which 11 are potentially new to science. The tetracladinid, lithistids harboured prokaryotic communities, which clustered separately from all other sponge species, contrasting with the non-tetracladinid, lithistid Vetulina incrustans. The tetracladinid, lithistids, furthermore, formed two distinct clusters with species of the Spirophorina suborder clustering apart from those of the Astrophorina suborder. The sclerosponge A. wellsi also harboured a distinct prokaryotic community in terms of composition including five unique, abundant OTUs with relatively low sequence similarities to organisms in GenBank. All cave sponges were enriched with SAR202 members, a group of bacteria known for their role in the degradation of recalcitrant compounds. The highest relative abundance of SAR202 was found in A. wellsi. We propose that the cave sponges of Orchid Island may play an as-yet uncharted role in nutrient dynamics at the land-sea interface.

The deep seafloor of the Northeastern Pacific Ocean between the Clarion and Clipperton Fracture Zones (CCZ) hosts large deposits of polymetallic nodules that are of great commercial interest as they are rich in valuable metals such as manganese, nickel, copper and cobalt. However, mining of these nodules has the potential to severely affect the benthic fauna, whose distribution and diversity are still poorly understood. The CCZ is characterized by strong gradients in sea surface productivity and hence changes in the amount of organic carbon reaching the seafloor, decreasing from mesotrophic conditions in the southeast to oligotrophic conditions in the northwest. Uncovering and understanding changes in community composition and structure along this productivity gradient are challenging but important, especially in the context of future mining impacts. Here, we summarize published data on benthic annelids (polychaetes), a major component of macrobenthic communities in the CCZ. Unlike previous studies, we attempt to explore all available data based on both morphology and genetics collected by box corer and epibenthic sledge. In this regard, we specifically aimed to (a) summarize and compare morphological and molecular data in relation to surface water nutrient conditions and (b) provide recommendations to advance the studies of polychaete biodiversity. Although initial studies on polychaetes in the CCZ were performed as far back as the 1970s, there are still large data gaps further explored in our review. For example, most of the current data are from the eastern CCZ, limiting understanding of species ranges across the region. An association between polychaete communities and the available food supply was generally observed in this study. Indeed, mesotrophic conditions supported higher abundance and species richness in polychaetes as a whole, but for certain groups of species, the patterns appear to be opposite — illustrating that relationships are likely more complex at lower taxonomic levels. A better understanding of biogeographical, ecological and evolutionary processes requires a concerted effort involving increased sampling and sharing of data and material to close existing knowledge gaps.

Seamounts are thought to function as hotspots of megafauna diversity due to their topology and environmental characteristics. However, assessments of megafauna communities inhabiting seamounts, including diversity and density, are scarce. In this study, we provide megafauna diversity and density estimates for a recently discovered, not yet characterized seamount region (Boetius seamounts) west of Cape Verde (N17° 16′, W29° 26′). We investigated the distribution of epibenthic megafauna over a large depth gradient from the seamount’s summit at 1400 m down to 3200 m water depth and provided qualitative and quantitative analyses based on quantified video data. In utilizing an ocean floor observation system (OFOS), calibrated videos were taken as a horizontal transect from the north-eastern flank of the seamount, differentiating between an upper, coral-rich region (−1354/−2358 m) and a deeper, sponge-rich region (−2358/−3218 m). Taxa were morphologically distinguished, and their diversity and densities were estimated and related to substrate types. Both the upper and deeper seamount region hosted unique communities with significantly higher megafauna richness at the seamount’s summit. Megafauna densities differed significantly between the upper (0.297 ± 0.167 Ind./m²) and deeper community (0.112 ± 0.114 Ind./m). The seamount showed a vertical zonation with dense aggregations of deep-sea corals dominating the seamount’s upper region and colonies of the glass sponges Poliopogon amadou dominating the deeper region. The results are discussed in light of detected substrate preferences and co-occurrence of species and are compared with findings from other Atlantic seamounts.

Traditionally, the apparent paucity of biogeographic barriers in marine environments when compared to terrestrial and freshwater habitats has been associated with high gene flow rates among geographically distant populations. However, physical traits such as tide currents, temperature, and salinity levels may serve as ecological boundaries thus leading to restricted-range phylogeographic patterns (e.g., the outflow plume from the Amazonas-Orinoco rivers between the Caribbean and the Brazilian Province) according to adaptive features of coastal organisms. To assess the degree of cohesiveness among populations and species of marine and estuarine fishes along a latitudinal gradient from Western South Atlantic, we carried out comparative phylogenetic and species delimitation analyses based on Cytochrome C Oxidase I (COI) sequences of 34 fish taxa from the Caribbean and Brazilian coasts. Distinct values of genetic diversity were revealed for both Provinces, ranging from moderate (1 to 2%) to high (≥ 2%) in 11.76% and 20.59% of the analyzed taxa, respectively. Furthermore, a significant genetic differentiation was observed within the nominal taxa Diapterus auratus, Citharichthys spilopterus, and Scorpaena plumieri from the Caribbean, as well as for Haemulon plumierii between the Caribbean and Brazilian Provinces. Such divergence is likely to result from temporal isolation among local populations during sea-level fluctuations during the Pliocene-Pleistocene period. The present findings demonstrate that similar biogeographic boundaries may result in species-specific patterns of genetic connectivity, possibly associated with ecological constraints. Since molecular operational taxonomic units (MOTUs) were identified in certain formal taxa from both Provinces, a systematic revision of these groups is highly recommended. At last, multispecies COI data proved to be helpful to phylogeographic inferences and to support appropriate policies for the conservation of natural resources.

The study of biogenic structures (e.g., lebensspuren) produced by benthic fauna on the seafloor provides invaluable information about the behavior of their tracemakers. In the case of sea stars, most of the previous research has been focused on shallow-marine environments due to the extreme scarcity of data from deep-sea lebensspurens. Here, we examined sea star traces from six deep-sea stations (deeper than 4500 m) near the Aleutian Trench (North Pacific). A total of six families were identified from still images. The majority of them were not observed producing any lebensspuren or just pentameral impressions related to resting and feeding activities. Two members of the families Pterasteridae and Porcellanasteridae could be clearly characterized by a composite behavior resulting in contrasting lebensspuren morphotypes. A morphotype belonging to the genus Hymenaster undet. produced pentameral impressions (related to predation) and punctuated trails (related to podia locomotion). Members of the family Porcellanasteridae produced oval to circular impressions (that may be related to burrowing trails for the detection of organic matter), flat-shallow trails (related to podia locomotion), and irregular M-ridged trails (related to locomotion while feeding through the sediment interface). There is a severe scarcity of data related to the locomotion of past deep-sea Asteroidea (i.e., trace fossils) and their ichnotaxonomical classification. We discuss the implications of our results for the ichnofamily Biformitidae, as well as the importance of considering other features (e.g., podia impressions) rather than just hook-shaped traces related to arm locomotion.