Collapse of scallop Nodipecten nodosus production in the tropical Southeast Brazil as a possible consequence of global warming and water pollution.

Mollusc rearing is a relevant global socioeconomic activity. However, this activity has faced severe problems in the last years in southeast Brazil. The mariculture scallop production dropped from 51,2 tons in 2016 to 10,2 tons in 2022 in the Baia da Ilha Grande (BIG; Rio de Janeiro). However, the possible causes of this collapse are unknown. This study aimed to analyze decadal trends of water quality in Nodipecten nodosus spat and adult production in BIG. We also performed physical-chemical and biological water quality analyses of three scallop farms and two nearby locations at BIG in 2022 to evaluate possible environmental stressors and risks. Scallop spat production dropped drastically in the last five years (2018-2022: mean ± stdev: 0.47 ± 0.45 million). Spat production was higher in colder waters and during peaks of Chlorophyll a in the last 13 years. Reduction of Chlorophyll a coincided with decreasing spat production in the last five years. Warmer periods (>27 °C) of the year may hamper scallop development. Counts of potentially pathogenic bacteria (Vibrios) and Escherichia coli were significantly higher in warmer periods which may further reduce scallop productivity. Shotgun metagenomics of seawater samples from the five studied corroborated these culture-based counts. Vibrios and fecal indicator bacteria metagenomic sequences were abundant across the entire study area throughout 2022. The results of this study suggest the collapse of scallop mariculture is the result of a synergistic negative effect of global warming and poor seawater quality.

Machine learning sheds light on physical-chemical and biological parameters leading to Abrolhos coral reef microbialization.

Microbes play a central role in coral reef health. However, the relative importance of physical-chemical and biological processes in the control of microbial biomass are unknown. Here, we applied machine learning to analyze a large dataset of biological, physical, and chemical parameters (N = 665 coral reef seawater samples) to understand the factors that modulate microbial abundance in the water of Abrolhos reefs, the largest and richest coral reefs of the Southwest Atlantic. Random Forest (RF) and Boosted Regression Tree (BRT) models indicated that hydrodynamic forcing, Dissolved Organic Carbon (DOC), and Total Nitrogen (TN) were the most important predictors of microbial abundance. The possible cumulative effects of higher temperatures, longer seawater residence time, higher nutrient concentration, and lower coral and fish biomass observed in coastal reefs resulted in higher microbial abundance, potentially impacting coral resilience against stressors.

Microbiome diversity from sponges biogeographically distributed between South America and Antarctica.

Sponges from South America and Antarctica are evolutionarily closely related. Specific symbiont signatures that could differentiate these two geographic regions are unknown. This study aimed to investigate the microbiome diversity of sponges from South America and Antarctica. In total 71 sponge specimens were analyzed (Antarctica: N = 59, 13 different species; South America: N = 12, 6 different species). Illumina 16S rRNA sequences were generated (2.88 million sequences; 40K ± 29K/sample). The most abundant symbionts were heterotrophic (94.8 %) and belonged mainly to Proteobacteria and Bacteroidota. EC94 was the most abundant symbiont and dominated the microbiome of some species (70-87 %), comprising at least 10 phylogroups. Each of the EC94 phylogroups was specific to one genus or species of sponge. Furthermore, South America sponges had higher abundance of photosynthetic microorganisms (2.3 %) and sponges from Antarctica, the highest abundance of chemosynthetic (5.5 %). Sponge symbionts may contribute to the function of their hosts. The unique features from each of these two regions (e.g., light, temperature, and nutrients) possibly stimulate distinct microbiome diversity from sponges biogeographically distributed across continents.

Sponges present a core prokaryotic community stable across Tropical Western Atlantic.

Sponges are among the earliest lineages of metazoans, with first fossil records dated back to 890 million years ago. All sponge species present associations with microorganisms to some extension, which influence sponges' survival and adaptation. Sponge species can be divided into two categories, Low Microbial Abundance and High Microbial Abundance, depending on the abundance of the microbial community that they host. Monanchora arbuscula (a Low Microbial Abundance sponge species) and Xestospongia muta (a High Microbial Abundance sponge species) are sponges with widespread distribution in the Tropical Western Atlantic. Despite previous studies on the major features of these species, little is known whether M. arcuscula and X. muta prokaryotic communities are stable across vast geographic regions. We obtained a total of ~9.26 million 16S rRNA gene Illumina sequences for M. arbuscula samples collected at seven locations and for X. muta samples collected at three locations, corresponding to five ecoregions of the Caribbean and the Southwestern Atlantic (N = 105, 39 from M. arcuscula and 66 from X. muta). These samples reflected different ecological strategies for prokaryotic communities assembly, since the core prokaryotic communities of M. arbuscula are more heterotrophic and shared with different sources (corals, sponges, seawater, sediments), while X. muta has more significant photosynthetic prokaryotic communities, mainly outsourced from other sponges. Results of M. arbuscula and X. muta prokaryotic communities analysis demonstrate that both sponge species have core prokaryotic communities stable across a vast geographic area (> 8000 km), and the world's most notable coastal marine biogeographic filter, the Amazon River Mouth, in spite of the significant differences found among transient prokaryotic communities of both sponge species.

Conserved rhodolith microbiomes across environmental gradients of the Great Amazon Reef.

The Great Amazon Reef System (GARS) covers an estimated area of 56,000 km2 off the mouth of the Amazon River. Living rhodolith holobionts are major benthic components of the GARS. However, it is unclear whether environmental conditions modulate the rhodolith microbiomes. Previous studies suggest that environmental parameters such as light, temperature, depth, and nutrients are drivers of rhodolith health. However, it is unclear whether rhodoliths from different sectors (northern, central, and southern) from the GARS have different microbiomes. We analysed metagenomes of rhodoliths (n = 10) and seawater (n = 6), obtained from the three sectors, by illumina shotgun sequencing (total read counts: 25.73 million). Suspended particulate material and isotopic composition of dissolved organic carbon (δ13C) indicated a strong influence of the Amazon river plume over the entire study area. However, photosynthetically active radiation at the bottom (PARb) was higher in the southern sector reefs, ranging from 10.1 to 14.3 E.m-2 day-1. The coralline calcareous red algae (CCA) Corallina caespitosa, Corallina officinalis, Lithophyllum cabiochiae, and Hapalidiales were present in the three sectors and in most rhodolith samples. Rhodolith microbiomes were very homogeneous across the studied area and differed significantly from seawater microbiomes. However, some subtle differences were found when comparing the rhodolith microbiomes from the northern and central sectors to the ones from the southern. Consistent with the higher light availability, two phyla were more abundant in rhodolith microbiomes from southern sites (Bacteroidetes, and Cyanobacteria). In addition, two functional categories were enhanced in southern rhodolith microbiomes (iron acquisition and metabolism, and photosynthesis). Phycobiliprotein-coding genes were also more abundant in southern locations, while the functional categories of respiration and sulfur metabolism were enhanced in northern and central rhodolith microbiomes, consistent with higher nutrient loads. The results confirm the conserved nature of rhodolith microbiomes even under pronounced environmental gradients. Subtle taxonomic and functional differences observed in rhodolith microbiomes may enable rhodoliths to thrive in changing environmental conditions.

Environmental modulation of the proteomic profiles from closely phylogenetically related populations of the red seaweed Plocamium brasiliense.

The genus Plocamium encompasses seaweeds that are widely distributed throughout the world's oceans, with Plocamium brasiliense found along the tropical and subtropical coasts of the Western Atlantic. This wide distribution can lead to structured populations due to environmental differences (e.g., light levels or temperature), restricted gene flow, and the presence of cryptic species. Abiotic variation can also affect gene expression, which consequently leads to differences in the seaweeds protein profile. This study aimed to analyze the genetic and proteomic profiles of P. brasiliense sampled in two geographically distinct sites on the coastline of Rio de Janeiro state, Brazil: Arraial do Cabo (P1) and Búzios (P2). The genetic profiles of macroalgal specimens from these two sites were indistinguishable as assessed by the markers UPA/23S, rbcL, and COI-5P; however, the protein profiles varied significantly between populations from the two sites. At both sites the ribulose-1,5-biphosphate carboxylase/oxygenase was the most abundant protein found in P. brasiliense specimens. The number of phycobiliproteins differed between both sites with the highest numbers being found at P1, possibly due to water depth. The differences in proteomic profiles of the two nearly identical populations of P. brasiliense suggest that environmental parameters such as light availability and desiccation might induce distinct protein expression, probably as a result of the phenotypic plasticity within this population of seaweed.

Remote sensing, isotopic composition and metagenomics analyses revealed Doce River ore plume reached the southern Abrolhos Bank Reefs.

On November 5th, 2015, the Fundão dam rupture released >50 million m3 of ore tailings into the Doce River, Minas Gerais State, Brazil. The huge volume of mud spread along the river and reached the sea, 17 days after the disaster, in Regência, Espírito Santo State (ES). In 2018, after three years of the disaster, the impacts of the ore tailings in the marine environment are still unclear. This study aims to investigate possible short-term impacts in marine biodiversity caused by the ore tailings' mud over the reef ecosystems that are closest to the disaster area: i.e. recently discovered reefs in the southern Abrolhos Bank. A remote sensing surveillance including winds, sea surface temperature, total suspended material and watercolor (MODIS Aqua data) indicated that the iron tailings plume reached the southern portion of Abrolhos Bank on June 16th, 2016. Subsequently, to obtain further evidence of the presence of the tailings in the coral reefs, water samples were collected in a gradient spanning from the river estuary to the reefs in southern Abrolhos Bank, we also analyzed the isotopic and microbial composition of the samples, as well as the reef benthic composition. Despite no clues of negative impact on benthic (coral) communities, isotopic analysis confirmed the presence of the plume over the reefs area. This study serves as a baseline for future long-term impact assessments of the health of coral reefs in the Abrolhos Bank.