Marine diversity patterns in Australia are filtered through biogeography

Latitudinal diversity gradients are among the most striking patterns in nature. Despite a large body of work investigating both geographic and environmental drivers, biogeographical provinces have not been included in statistical models of diversity patterns. Instead, spatial studies tend to focus on species–area and local–regional relationships. Here, we investigate correlates of a latitudinal diversity pattern in Australian coastal molluscs. We use an online database of greater than 300 000 specimens and quantify diversity using four methods to account for sampling variation. Additionally, we present a biogeographic scheme using factor analysis that allows for both gradients and sharp boundaries between clusters. The factors are defined on the basis of species composition and are independent of diversity. Regardless of the measure used, diversity is not directly explained by combinations of abiotic variables. Instead, transitions between regions better explain the observed patterns. Biogeographic gradients can in turn be explained by environmental variables, suggesting that environmental controls on diversity may be indirect. Faunas within provinces are homogeneous regardless of environmental variability. Thus, transitions between provinces explain most of the variation in diversity because small-scale factors are dampened. This explanation contrasts with the species-energy hypothesis. Future work should more carefully consider biogeographic gradients when investigating diversity patterns.

Marine diversity in the biosphere reserve of the most oceanic island in the Gulf of California: San Pedro Mártir

San Pedro Mártir island is of high biological, ecological, and fishery importance and was declared a biosphere reserve in 2002. This island is the most oceanic in the Gulf of California, and information on its rocky reefs is scarce. The present study aimed to generate the first list of conspicuous invertebrate and fish species based on in situ observations and to examine the community structure of the shallow rocky reefs of the reserve. In addition, we estimated the ecological indicators of richness, abundance, Shannon diversity, and Pielou evenness to evaluate the conservation status of the biosphere reserve. Data were collected annually from 2007 to 2017 through 2,192 underwater SCUBA transects. A total of 35 species of invertebrates and 73 species of fish were recorded. Most of the species are widely distributed along the eastern Pacific. Overall, 64% of the species found in this study are commercially important, and 11 species have been listed as protected. The abundance of commercially important invertebrate species (i.e., the sea cucumber Isostichopus fuscus and the spiny oyster Spondylus limbatus) is decreasing, while commercially important fish species have maintained their abundance with periods of increase. The ecological indicators and the abundance and size of the commercial species indicate that the reserve is in good condition while meeting its conservation objectives.

Combining Multiple Markers in Environmental DNA Metabarcoding to Assess Deep-Sea Benthic Biodiversity

Environmental DNA (eDNA) metabarcoding is an emerging tool to estimate diversity by combining DNA from the environmental samples and the high-throughput sequencing. Despite its wide use in estimating eukaryotic diversity, many factors may bias the results. Maker choice and reference databases are among the key issues in metabarcoding analyses. In the present study, we compared the performance of a novel 28S rRNA gene marker designed in this study and two commonly used 18S rRNA gene markers (V1-2 and V9) in estimating the eukaryotic diversity in the deep-sea sediments. The metabarcoding analyses based on the sediment surveys of the Okinawa Trough found that more eukaryotic taxa were discovered by 18S V9 than 28S and 18S V1-2, and that 18S V9 also performed better in metazoan recovery than the other two markers. Although a broad range of taxa were detected by the three metabarcoding markers, only a small proportion of taxa were shared between them even at the phylum level. The non-metric multidimensional scaling (NMDS) analysis also supported that communities detected by the three markers were distinct from each other. In addition, different communities were resolved by different reference databases (NCBI nt vs. SILVA) for the two 18S markers. Combining the three markers, annelids were found to be the most abundant (44.9%) and diverse [179 operational taxonomic units (OTUs)] metazoan group in the sediments of the Okinawa Trough. Therefore, multiple independent markers are recommended to be used in metabarcoding analyses during marine diversity surveys, especially for the poorly understood deep-sea sediments.

Climate Projections for the Southern Ocean Reveal Impacts in the Marine Microbial Communities Following Increases in Sea Surface Temperature

Anthropogenic global warming can have strong impacts on marine ecosystems, especially on climate-sensitive regions such as the Southern Ocean (SO). As key drivers of biogeochemical cycles, pelagic microbial communities are likely to respond to increases in sea surface temperature (SST). Thus, it is critical to understand how SST may change in future scenarios and how these changes will affect the composition and structure of microbial communities. By using a suite of Earth System Models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), machine learning, and 16S rRNA sequencing data, we investigated the long-term changes as projected by CMIP6 simulations in SST throughout the twenty first century and the microbial diversity responses in the SO. Four Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) were considered to assess the SO surface sensitivity to a warming climate. The SST changes across SSPs were ≈0.3, ≈0.7, ≈1.25, and ≈1.6oC between 2015 and 2100, respectively, and the high emissions scenarios projected a much sooner emergence of the human-induced temperature change throughout the SO. The impacts on Antarctic marine diversity of bacteria and archaea are expected to be significant and persistent by the late twenty first century, especially within the higher end of the range of future forcing pathways.

Mesophotic fish communities of the ancient coastline in Western Australia

Marine diversity across the Australian continental shelf is shaped by characteristic benthic habitats which are determined by geomorphic features such as paleoshorelines. In north-western Australia there has been little attention on the fish communities that inhabit an ancient coastline at ~125 m depth (the designated AC125), which is specified as a key ecological feature (KEF) of the region and is thought to comprise hard substrate and support enhanced diversity. We investigated drivers of fish species richness and assemblage composition spanning six degrees of latitude along sections of the ancient coastline, categorised as ‘on’ and ‘off’ the AC125 based on depth, across a range of habitats and seafloor complexity (~60–180 m depth). While some surveyed sections of the AC125 had hard bottom substrate and supported enhanced fish diversity, including over half of the total species observed, species richness and abundance overall were not greater on the AC125 than immediately adjacent to the AC125. Instead, depth, seafloor complexity and habitat type explained patterns in richness and abundance, and structured fish assemblages at both local and broad spatial scales. Fewer fishes were associated with deep sites characterized by negligible complexity and soft-bottom habitats, in contrast to shallower depths that featured benthic biota and pockets of complex substrate. Drivers of abundance of common species were species-specific and primarily related to sampling Areas, depth and substrate. Fishes of the ancient coastline and adjacent habitats are representative of mesophotic fish communities of the region, included species important to fisheries and conservation, and several species were observed deeper than their currently known distribution. This study provides the first assessment of fish biodiversity associated with an ancient coastline feature, improving our understanding of the function it plays in regional spatial patterns in abundance of mesophotic fishes. Management decisions that incorporate the broader variety of depths and habitats surrounding the designated AC125 could enhance the ecological role of this KEF, contributing to effective conservation of fish biodiversity on Australia’s north west shelf.

Astronomically paced marine biological evolution during the Late Paleozoic icehouse-to-greenhouse transition

<p>Late Paleozoic deglaciation is the Earth’s first icehouse-to-greenhouse transition in a vegetated world, but the climatic and biological responses to this transition have not yet been fully addressed. We conducted cyclostratigraphic analysis on the magnetic susceptibility from a deep marine carbonate succession in South China, to reconstruct the astrochronology of the late Early Permian, and to decipher evolutionary responses to astronomically forced climate changes in a marine diversity time series. Our results indicates that the minima of ~1.8 m.y. short orbital eccentricity amplitude modulation cycles led to seasonally stable precipitation patterns and a constant input of nutrients, which spurred marine biodiversity during this deglaciation. Synchronizing global biotic and abiotic records reveals that peaks of marine biodiversity occurred during nodes of ~1.3 m.y. obliquity amplitude modulation cycles, when ice sheet expansion triggered enhanced precipitation and organic carbon burial during icehouse conditions (290−285.1 Ma). Starting at 285.1 Ma, the insolation-biodiversity relationship began to change, paced by glacial termination and tropical aridification. With the transition to greenhouse conditions (~279.1−272 Ma), obliquity nodes became associated instead with terrestrial aridity and marine anoxia, and suppression of marine speciation. Our results bring into focus a pattern of shifting dynamics involving Earth’s astronomical parameters, climate change and marine biodiversity for icehouse and greenhouse worlds in the late Paleozoic Era.</p>

Commercial fish abundance estimation in the Belgian part of the North Sea through eDNA ddPCR analyses

Monitoring of fish assemblages in the Belgian part of the North Sea (BPNS) mainly happens through trawling. While effective, this method is invasive and destructive as it disturbs bottom communities, catches non-target species and removes organisms from the environment. A more sustainable alternative for monitoring marine diversity is the use of environmental DNA (eDNA) which comprises intra- and extracellular genetic material that comes from the shedding of organic material, like scales and mucus in the case of fish. When applying metabarcoding on eDNA, community composition can be inferred simply by analysing a small volume of water. Therefore the technique does not disturb the environment, and the high sensitivity of eDNA allows the detection of rare and transient species that are frequently missed by traditional sampling methods. Next to determining community composition, the amount of eDNA copies in the water could potentially be used to quantify target fish species in the marine environment. Here, we investigate whether eDNA concentrations from marine water samples correlate with local fish abundance estimates obtained via traditional beam trawling. Species specific Droplet Digital Polymerase Chain Reaction (ddPCR) assays were designed and tested for three economically important species: common sole (Solea solea), plaice (Pleuronectes platessa) and whiting (Merlangius merlangus). In march 2020, 12 sites in the BPNS were selected based on absence, low and high abundances of the three target species as observed in epibenthos monitoring data from previous years. In each site, 2L of seawater was collected with a niskin bottle from ca 1m above the sea floor. Subsequently, beam trawl transects of 1 km were conducted and all epibenthos species caught in the trawling net were morphologically identified, counted and weighted. Our results indicate promising correlations between eDNA concentrations obtained with the ddPCR assays and the number of specimens in the net for all three species. Some “false” positive results were obtained with the ddPCR, but these may actually be “true” positive detections because the fish might be present in the area but were not caught in the trawling transects. This warrants further investigation to see how far eDNA signals can be detected in the North Sea system. Next, 50 water samples were collected in Autumn 2020, involving more locations with or without the three fishes. This time samples were taken at the beginning, middle and end of the 1 km transects to investigate small scale horizontal variation in eDNA concentrations. The autumn samples are currently being processed. In March 2021, samples will be taken at different depths (surface, middle of the water column and ca 1m above the seafloor) to investigate whether there are any vertical patterns in eDNA distribution in a very well mixed system such as the BPNS. A DNA shedding experiment will be performed as well to estimate the rate at which the three fishes shed DNA. This will provide important information on how quickly fishes can be detected when they swim by. The information obtained with the field sampling and experimental setting will help to strengthen the correlation to a point that reliable abundance estimations of our target species become possible and will allow us to evaluate the potential of eDNA as a sustainable alternative/addition to traditional monitoring methods.

Specimens of the Pacific longnose chimaera Harriotta raleighana Goode & Bean 1895 from the Mexican Pacific in scientific collections of Mexico and the world

Chimaeras are cartilaginous fish that live in waters more than 200 m deep. There are two species in the Rhinochimaeridae family, where only one, Harriotta raleighana, occurs in Mexican waters. It is considered a rare species for the country because of the number of observations and specimens collected in the Mexican Pacific, from Baja California to Colima, starting more than 100 years ago. This work integrates for the first time the published and unpublished information of this species for this region. Only seven specimens have been collected; they are deposited in different scientific collections of Mexico and the USA. Interestingly, none of these specimens were collected during surveys since all have been collected incidentally by fishermen. There is currently one specimen missing from a collection, a relevant issue due to its rareness. Samples must be deposited and preserved adequately for further studies about this rare and other deep-sea species, that improves the knowledge of the Mexican marine diversity.

Decapod crustaceans associated with macroinvertebrates in Pacific Costa Rica

Decapod crustaceans are a diverse group that exploits various types of habitats in Costa Rica, where they represent 8.1% of the marine diversity of the country. This group includes families containing species with strictly symbiotic behavior, e.g., the Palaemonidae and Pinnotheridae. Despite the high diversity of decapods and the importance of symbionts in marine ecosystems, very little research has been done regarding symbiosis in Costa Rica and the Central American region. The objective of the present study is to present a check list of the species of decapods that are associated with macroinvertebrates in Pacific Costa Rica. The research was carried out using different sources, including a literature review, the Crustaceans Collection of the Zoology Museum of the University of Costa Rica, and field surveys between 1970 and 2019 along the Pacific coast of Costa Rica, and Isla del Coco, 500 km offshore. One-hundred associations are reported, of 74 species of symbiotic decapods with six host phyla. Seventy-four associated with Cnidaria, 15 with Echinodermata, four each with Annelida and Mollusca, two with Chordata, and one with Porifera. In total, there were 14 new reports of decapods occurring on Isla del Coco and four new reports of decapods for Costa Rica: Pseudocoutierea elegans, Raytheres clavapedatus, Tuleariocaris holthuisi, and Calyptraeotheres pepeluisi. These results highlight the need to conduct more detailed studies to determine the real diversity and ecological importance of the associations between marine organisms.

Biological Effect of Posidonia oceanica Seaweed on Some Pathogenic Microbes

Compared to other coasts, Libyan coasts are characterized by low levels of pollution. This makes them a suitable environment for marine diversity, especially seaweeds, which may be considered a source of new compounds that are biologically active in their resistance to microbes. Therefore, the present study was conducted with the aim of testing the bioactivity of leave and rhizome extracts of Posidonia oceanica seaweed (aqueous, ethanol, and acetone) at concentrations (50, 100, and 150) mg/ml against three types of pathogenic bacteria (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa), and fungus (Candida spp.), by a sensitivity test in the form of a disk diffusion method. The results showed that Posidonia oceanica seaweed extracts have good inhibitory activity against S.aureus and Candida spp., and that the concentration of 150 mg/ml is the most effective for all extracts. The results also indicated that rhizome extracts are more efficient than leaf extracts, and the acetone extract is the best in inhibiting the tested microbes. Also, Escherichia coli and Pseudomonas aeruginosa are the most resistant to all extracts, regardless of type and concentration used.