JournalTOCs

Frontiers in Marine Science
Journal Prestige (SJR): 1.225

Citation Impact (citeScore): 3
Number of Followers: 13

This is an Open Access Journal

Open Access journal
ISSN (Online) 2296-7745
Published by Frontiers Media

[96 journals]

Unprecedented Coral Mortality on Southwestern Atlantic Coral Reefs
Following Major Thermal Stress
- Authors: Pedro H. C. Pereira, Gislaine V. Lima, Antônio V. F. Pontes, Luis G. F. Côrtes, Erandy Gomes, Cláudio L. S. Sampaio, Taciana Kramer Pinto, Ricardo J. Miranda, Andrei Tiego Cunha Cardoso, Julia Caon Araujo, José Carlos Sícoli Seoane
  Abstract: Thermal stress is now considered the major recent cause of coral reef degradation; yet few studies have been conducted describing those effects on Southwestern Atlantic (SWA) reefs. The SWA represents a coral endemism hotspot with low-functional redundancy and therefore high extinction risk. Recent research has suggested a “thermal refuge” potential for SWA; however, evidence could suggest a different trend. We report herein an unprecedented coral mortality on the largest coastal Brazilian Marine Protected Area (MPA) following the worst thermal stress event since 1985. Degree Heating Week (DHW) values over 4.0 were observed for 107 days, averaging 8.70 for the period, with a maximum of 12.1. Average live coral cover was reduced by 18.1% while average turf algae cover increase by 19.3%. Mortality was highest for three coral species, with a mean mortality of 50.8% per transect for Millepora braziliensis, 32.6% for Mussismilia harttii and 16.6% for Millepora alcicornis. Our unique data for SWA indicates that the populations of two Brazilian endemic species (Millepora braziliensis and Mussismilia harttii) are under severe threat from global warming and that overall coral cover has been dramatically reduced. Hence, the idea of a possible “thermal” refugia within the SWA must be taken with caution for this coral endemism hotspot.
  PubDate: 2022-05-20T00:00:00Z
Ocean Acidification Alters the Predator – Prey Relationship Between
Hydrozoa and Fish Larvae
- Authors: Carsten Spisla, Jan Taucher, Michael Sswat, Hennrike Wunderow, Peter Kohnert, Catriona Clemmesen, Ulf Riebesell
  Abstract: Anthropogenic CO2 emissions cause a drop in seawater pH and shift the inorganic carbon speciation. Collectively, the term ocean acidification (OA) summarizes these changes. Few studies have examined OA effects on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities. Because Hydrozoa can seriously compete with and prey on other higher-level predators such as fish, changes in their abundances may have significant consequences for marine food webs and ecosystem services. To investigate the interaction between Hydrozoa and fish larvae influenced by OA, we enclosed a natural plankton community in Raunefjord, Norway, for 53 days in eight ≈ 58 m³ pelagic mesocosms. CO2 levels in four mesocosms were increased to ≈ 2000 µatm pCO2, whereas the other four served as untreated controls. We studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study. These results indicate that a decrease in predation pressure shortly after hatch likely shaped higher herring larvae survival, when hydromedusae abundance was lower in the OA treatment compared to control conditions. We conclude that indirect food-web mediated OA effects drove the observed changes in the Hydrozoa – fish relationship, based on significant changes in the phyto-, micro-, and mesoplankton community under high pCO2. Ultimately, the observed immediate consequences of these changes for fish larvae survival and the balance of the Hydrozoa – fish larvae predator – prey relationship has important implications for the functioning of oceanic food webs.
  PubDate: 2022-05-20T00:00:00Z
Response Process of Coastal Hypoxia to a Passing Typhoon in the East China
Sea
- Authors: Qicheng Meng, Feng Zhou, Xiao Ma, Jiliang Xuan, Han Zhang, Shuai Wang, Xiaobo Ni, Wenyan Zhang, Bin Wang, Dewang Li, Di Tian, Jia Li, Jiangning Zeng, Jianfang Chen, Daji Huang
  Abstract: Details of the development of coastal hypoxia in response to the passage of Typhoon Bavi (2020) in the East China Sea were reconstructed by numerical modeling using a three-dimensional coupled physical–biogeochemical model. The model was validated via repeated surveys along a transect across a submerged river valley off the Changjiang Estuary before and after the passage of Typhoon Bavi. Before Bavi’s arrival, survey data indicated that the coastal hypoxia had formed off the Changjiang Estuary. However, the hypoxia was not eliminated but instead migrated and aggravated along the observed transect after the typhoon passage. This phenomenon cannot be attributed to the typhoon-induced mixing. Simulation results reveal that the observed development and spatial migration of hypoxia was mainly controlled by typhoon-induced oceanic advection. Results show that Bavi stimulated a regional quasi-barotropic cyclonic loop circulation and coastal downwelling reversing general summer circulation patterns. The onshore transport of the warmer shelf water and subsequent downwelling resulted in a warming of coastal water. The southward coastal current and downwelling induced by the typhoon also led to a migration of the hypoxic zone. Meanwhile, a massive transport of resuspended planktonic detritus from the steep inner shelf and the shallow Changjiang bank toward the submerged river valley occurred. This study reveals that the typhoon-driven currents can play an important role in the development of hypoxia and redistribution of deposited organic matter in coastal shelf seas, which may have both short- and long-term effects on the regional marine biogeochemical environment.
  PubDate: 2022-05-20T00:00:00Z
Numerical Simulation and Backscattering Characteristics of Freak Waves
Based on JONSWAP Spectrum
- Authors: Gengkun Wu, Lichen Han, Lihong Zhang
  Abstract: Based on the linear wave superposition model, we realize the numerical simulation of three-dimensional (3-D) surface waves combined with JONSWAP spectrum and stereo wave observation project (SWOP) directional function. According to the formation characteristics of freak waves to concentrate the wave energy at a specific location, the component waves are modulated. A complete numerical simulation model of time-invariant 3-D freak waves evolution is first proposed in this study. Then, the accuracy of the model is verified from the aspects of wave height distribution, frequency spectrum estimation, and freak wave parameters. The effectiveness of wave steepness as the discrimination condition of freak waves is discussed through experiments. In terms of the electromagnetic scattering characteristics of freak waves, we construct an electromagnetic scattering model, fitting the time-invariant 3-D freak wave, based on the two-scale method (TSM). By comparing and analysing the scattering characteristics D-value of synthetic aperture radar (SAR) image of the freak wave and the background wave, the rationality of the electromagnetic scattering characteristics of the freak wave as its feature identification is verified. Comparing the normalized radar cross section (NRCS) of freak waves and background sea waves, the experiment shows that the NRCS value of freak waves is the lowest, and the calculation results of the two have obvious differences. The research conclusions above can provide effective data support for the identification and detection of freak waves in practical offshore engineering.
  PubDate: 2022-05-20T00:00:00Z
Environmental Quality and Ecological Risk Assessment of Heavy Metals in
the Zhuhai Coast, China
- Authors: Jin Wu, Shaowei Rong, Miaowei Wang, Rong Lu, Jingchao Liu
  Abstract: The rapid urbanization and industrialization in the coastal Zhuhai have resulted in severe heavy metal contamination. Heavy metals are extensively used as indicators of coastal contamination, but the comparability among different geographic environments needs to be further explored and scrutinized. In this study, heavy metals (i.e., As, Zn, Cd, Cr, Hg, Cu, and Pb) in surface seawater (20 sites), sediments (10 sites), and organisms (13 sites, shellfish, algae, fish, and crustaceans) were analyzed to assess the distribution, enrichment, and ecological risk in the coastal regions of Zhuhai (2017 and 2018). The results showed that Cu, Zn, and Pb exceeded the standards of seawater, indicating the presence of anthropogenic pollution. Meanwhile, the ecological risk results showed that Cd and Cu indicated moderately high environmental risks. The quantity and quality of heavy metals in organisms showed different trends in the sea, which affected marine organisms in the northeastern area. The main factors contributing to the ecological risk of these two heavy metals are the emissions from chemical companies. Therefore, preserving the high biological diversity in this area is important to ensure the health and productivity of the seawater ecosystem in the coastal area. These results may play a key role in promoting decision makers to manage the sustainability of the Zhuhai coast.
  PubDate: 2022-05-20T00:00:00Z
Oil Spill and Socioeconomic Vulnerability in Marine Protected Areas
- Authors: Felipe Roberto da Silva, Alexandre Schiavetti, Ana Cláudia Mendes Malhado, Beatrice Ferreira, Caio Victor de Paula Sousa, Fábio Pessoa Vieira, Francisco Roberto Pinto, Gabriel Barros Gonçalves de Souza, George Olavo, Jéssica Borba Quintela dos Santos, Joao Vitor Campos-Silva, José Gilmar Cavalcante de Oliveira Júnior, Leonardo Tortoriello Messias, Márcio Luiz Vargas Barbosa Filho, Miguel da Costa Accioly, Nidia Noemi Fabré, Patrizia Raggi Abdallah, Priscila F. M. Lopes, Ruy Kenji Papa de Kikuchi, Samuel Façanha Câmara, Vandick da Silva Batista, Marcelo O. Soares
  Abstract: The extensive oil spill (> 2,900 km) that occurred in the southwestern Atlantic (2019/2020) increased the vulnerability of the Brazilian coast, affecting marine and coastal protected areas (MPAs). In addition to supporting conservation, MPAs are sustainably used by local populations to help maintain ocean-dependent livelihoods. In this sense, we aim to assess the socioeconomic vulnerability of human communities in MPAs affected by this major oil spill. Using digital mapping, we assessed the socioeconomic vulnerability of 68 human communities living in or near 60 MPAs of different categories that were impacted by this spill. This is the first assessment of the vulnerability status of human populations under significant levels of poverty and social inequality, which are particularly dependent on healthy and effective Brazilian MPAs. More than 6,500 enterprises and institutions were mapped, including trade activities, services, tourism, and leisure venues. Most enterprises (34.4%) were involved in the food sector, related to the ocean economy, and, therefore, highly vulnerable to oil spills. Furthermore, the majority (79.3%) of the vulnerable activities are concentrated in multiple-use MPAs, with extractive reserves coming second and accounting for 18%. This result shows the high vulnerability of this tropical coast to oil accidents and the risks to food security for traditional communities. We also found a heterogeneous vulnerability indicator along the coast, with the most vulnerable regions having an undiversified economic matrix heavily dependent on activities such as fishing, family farming, tourism, accommodation, and the food sector. Thus, this study provides a tool to help prevent and mitigate economic losses and increases the understanding of the weaknesses of MPAs in the face of large-scale disasters, thus helping to build socioeconomic and ecological resilience.
  PubDate: 2022-05-20T00:00:00Z
Spatial Analysis for Mariculture Site Selection: A Case Study of Kukup
Aquaculture Zones in the Peninsula of Malaysia
- Authors: Wei-Kang Chor, Teng-Yun Lai, Melissa Mary Mathews, Tony Chiffings, Chi-Wei Cheng, Victor Charlie Andin, Kok-Song Lai, Jiun-Yan Loh
  Abstract: Marine aquaculture sites at Kukup Strait in the peninsula of Malaysia are experiencing a decline in water quality in the last five years, resulting in high mortality rates (50 - 80%), seasonal massive fish mortalities and poor profitability. Currently, Kukup farmers are involved in intensive aquaculture within the existing aquaculture zone. This study explores the sustainability of a modern mariculture method, where fish farms are relocated to deeper waters with higher flushing rates, and high-density polyethylene (HDPE) are used to improve water quality. Several site selection criteria are utilised in identifying the proposed aquaculture industrial zone: 1) bathymetry depth (operational requirement: 10 m to 30 m), 2) located within the Kukup Port Limit, 3) does not interfere with the Kukup ferry navigation route, and 4) distance from Kukup mainland. Site feasibility analysis, including hydrodynamics, meteorology, water quality, sediment quality and macrobenthos assessment, was conducted to compare the proposed and existing aquaculture sites. It was found that the water quality at the existing site contained higher concentrations of fecal coliform and nutrients and salinity fluctuations. Tropical finfish can survive under these conditions with poorer fish health and higher fish mortality. Apart from that, the flushing capacity is higher in the proposed site, indicating the capacity to handle moderate-intensity aquaculture. Moderate-intensity aquaculture using HDPE cages could be profitable for the local fish farmers. Therefore, it is suggested that other locations within Kukup Straits with deeper waters (> 25 m) with possibly improved water quality and the ability for intensive aquaculture production should be explored for a larger depth and economics of scale.
  PubDate: 2022-05-20T00:00:00Z
Effects of Algal Blooms on Phytoplankton Composition and Hypoxia in
Coastal Waters of the Northern Yellow Sea, China
- Authors: Xiaohong Sun, Zhao Li, Xueyan Ding, Guanglei Ji, Lei Wang, Xiaotong Gao, Qige Chang, Lixin Zhu
  Abstract: Summer hypoxia and harmful algal bloom occurred sometimes in the nearshore of the northern Yellow Sea in recent years. Based on seven multidisciplinary investigations conducted from March to November 2016, except for April and October, the phytoplankton community and its association with ambient seawater physicochemical parameters in coastal waters of the northern Yellow Sea were comprehensively examined. In total, 39 taxa belonging to 4 phyla and 24 genera were identified. Diatoms and dinoflagellates were the dominant groups, which accounted for 64.1% and 30.8% of total species, respectively. An algal blooming event dominated by the diatom (Thalassiosira pacifica) occurred in March, which affects the shifting of diatom–dinoflagellate dominance. A notable dinoflagellate dominance occurred especially in surface water throughout the whole summer but changed to diatom dominance again from September. Hypoxic zones (
  PubDate: 2022-05-20T00:00:00Z
Hydrological and Biogeochemical Patterns in the Sicily Channel: New
Insights From the Last Decade (2010-2020)
- Authors: Francesco Placenti, Marco Torri, Federica Pessini, Bernardo Patti, Vincenzo Tancredi, Angela Cuttitta, Luigi Giaramita, Giorgio Tranchida, Roberto Sorgente
  Abstract: The hydrological and biogeochemical time series from 2010 to 2020 have highlighted specific relationships and trends in oceanographic processes and nutrient patterns in the Sicily Channel. Specifically, temperature and salinity time series in the intermediate waters showed a sharp annual increase of about 0.06°C and 0.09 within the period 2010-2020, at rates that are about 50% higher than what observed within the previous decade. Similar trends were also present in deep waters, although with lower variations of both temperature and salinity. The time series in the intermediate water, also highlighted the presence of quasi cyclic fluctuations that can be associated with the alternation of the circulation modes (cyclonic and anticyclonic) of the Northern Ionian Gyre. Moreover, an opposite trend emerged by comparing the nutrients and salinity time series in intermediate waters, while similar patterns has been evidenced between nutrients and chlorophyll-a concentration. This latter finding is not consistently present in the Mediterranean area, suggesting the need of further studies on a wider scale.
  PubDate: 2022-05-20T00:00:00Z
Severe Deoxygenation Event Caused by the 2011 Eruption of the Submarine
Volcano Tagoro (El Hierro, Canary Islands)
- Authors: Alba González-Vega, Izar Callery, Jesús M. Arrieta, J. Magdalena Santana-Casiano, J. Francisco Domínguez-Yanes, Eugenio Fraile-Nuez
  Abstract: The shallow, near-shore submarine volcano Tagoro erupted in October 2011 at the Mar de las Calmas marine reserve, south of El Hierro island. The injection of lava into the ocean had its strongest episode during November 2011 and lasted until March 2012. During this time, in situ measurements of dissolved oxygen were carried out, using a continuous oxygen sensor constantly calibrated with water samples. A severe deoxygenation was observed in the area, particularly during October-November 2011, which was one of the main causes of the high mortality observed among the local marine ecosystem. The measured O2 concentrations were as low as 7.71 µmol kg-1, which represents a -96% decrease with respect to unaffected waters. The oxygen depletion was found in the first 250 m of the water column, with peaks between 70-120 m depth. The deoxygenated plume covered an area of at least 464 km2, distributed particularly south and south-west of the volcano, with occasional patches found north of the island. The oxygen levels were also monitored through the following years, during the degassing stage of the volcano, when oxygen depletion was no longer observed. Additionally, during the eruption, an island-generated anticyclonic eddy interacted with the volcanic plume and transported it for at least 80 km, where the O2 measurements still showed a -8% decrease after mixing and dilution. This feature draws attention to the permanence and transport of volcanic plumes far away from their source and long after the emission.
  PubDate: 2022-05-20T00:00:00Z
Neocalanus cristatus (Copepoda) From a Deep Sediment-Trap: Abundance and
Implications for Ecological and Biogeochemical Studies
- Authors: Takahito Ikenoue, Shigeyoshi Otosaka, Makio C. Honda, Minoru Kitamura, Yoshihisa Mino, Hisashi Narita, Takuya Kobayashi
  Abstract: We studied seasonal variations of the mesozooplankton swimmer community collected by a sediment trap moored at 873 m in the Kuroshio–Oyashio Transition region off the east coast of Japan from 5 August 2011 to 23 June 2013, with sampling bottles rotating at 26-day intervals. The total flux of mesozooplankton swimmers varied between 0 and 11.1 individuals m–2 d–1, with a mean of 3.1 individuals m–2 d–1 during the sampling period. In total, 89 taxa were found in the trap material, of which copepods comprised 87.1% of all swimmers on average. Among the Copepoda, Neocalanus cristatus was the most dominant taxon (76.2% of copepods on average during the sampling period), and all of them were stage C5 copepodite to adult. The species composition of the swimmers closely reflected the mesopelagic mesozooplankton of the Oyashio region. Because all N. cristatus observed in the trap were stage C5 to adult, its flux represents a time series of variations in life history and response to environmental changes at the depth of the sediment trap. The fluxes of Neocalanus species (N. cristatus, N. flemingeri, and N. plumchrus) reflected ontogenetic vertical migration, but may have been overestimates of active fluxes if they included dormant individuals that accidentally entered the sediment trap. The apparent active carbon flux of Neocalanus species ranged from 0 to 22.3 mg C m–2 d–1 during the sampling period, with a mean value of 4.9 mg C m–2 d–1.
  PubDate: 2022-05-20T00:00:00Z
Growth and Reproduction of the Pacific Oyster Crassostrea gigas Cultured
on Tidal Flat in Hebei Spirit Oil Spill Area on the West Coast of Korea
Four Years After the Accident
- Authors: Hyun-Ki Hong, Heung-Sik Park, Kwang-Sik Choi
  Abstract: The Hebei Spirit oil spill (HSOS) accident in December 2007 on the west coast of Korea devastated the intertidal oyster farms along the Taean coast, resulting in the shut-down of the farming for three years. In 2010, two years after the accident, the level of residual oil in the water, sediment, and oyster tissue in the spilled area became similar to the level before the accident, although the fitness of the oysters in the spilled area remained unknown. In an attempt to resume the oyster culture in the spilled area, we monitored the growth and reproduction of the Pacific oyster Crassostrea gigas in an area the most heavily impacted. The oyster spats used in this study were harvested from the oil-damaged area in September 2011 and hardened for 9 months before being transplanted into the grow-out facilities in May 2012. The transplanted oysters demonstrated a fast shell growth for the first 5 months, reaching 53.9 mm in shell length (SL) in October 2011. At the end of the survey in November 2013, the oyster became 65 mm, suggesting an additional year of cultivation to reach the market size. Histology indicated that the annual gametogenesis was synchronous, as the males and females initiated the gametogenesis in January when the water temperature was 5.2°C. The female oysters spawned from July to September, as the water temperature ranged from 21.2 to 24.8°C. An indirect enzyme-linked immunosorbent assay (ELISA) applied in the reproductive effort measurement indicated that the fully ripe female oysters produced 20-23% of their body weight as eggs prior to spawning, which was comparable to the reproductive effort of oysters in oil-spill-free areas. The data suggested that off-bottom rack cultured Pacific oysters at the Euhangri beach successfully recovered from HSOS stresses 4 years after the accident.
  PubDate: 2022-05-20T00:00:00Z
Long-Term and Seasonal Variability of Wind and Wave Extremes in the Arctic
Ocean
- Authors: Isabela S. Cabral, Ian R. Young, Alessandro Toffoli
  Abstract: Over recent decades, the Arctic Ocean has experienced dramatic variations due to climate change. By retreating at a rate of 13% per decade, sea ice has opened up significant areas of ocean, enabling wind to blow over larger fetches and potentially enhancing wave climate. Considering the intense seasonality and the rapid changes to the Arctic Ocean, a non-stationary approach is applied to time-varying statistical properties to investigate historical trends of extreme values. The analysis is based on a 28-year wave hindcast (from 1991 to 2018) that was simulated using the WAVEWATCH III wave model forced by ERA5 winds. Despite a marginal increase in wind speed (up to about 5%), results demonstrate substantial seasonal differences and robust positive trends in extreme wave height, especially in the Beaufort and East Siberian seas, with increasing rates in areal average of the 100-year return period up to 60%. The reported variations in extreme wave height are directly associated with a more effective wind forcing in emerging open waters that drives waves to build up more energy, thus confirming the positive feedback of sea ice decline on wave climate.
  PubDate: 2022-05-19T00:00:00Z
Pathway-Centric Analysis of Microbial Metabolic Potential and Expression
Along Nutrient and Energy Gradients in the Western Atlantic Ocean
- Authors: Maria A. Cavaco, Maya P. Bhatia, Alyse K. Hawley, Monica Torres-Beltrán, Winifred M. Johnson, Krista Longnecker, Kishori Konwar, Elizabeth B. Kujawinski, Steven J. Hallam
  Abstract: Microbial communities play integral roles in driving nutrient and energy transformations in the ocean, collectively contributing to fundamental biogeochemical cycles. Although it is well known that these communities are stratified within the water column, there remains limited knowledge of how metabolic pathways are distributed and expressed. Here, we investigate pathway distribution and expression patterns from surface (5 m) to deep dark ocean (4000 m) at three stations along a 2765 km transect in the western South Atlantic Ocean. This study is based on new data, consisting of 43 samples for 16S rRNA gene sequencing, 20 samples for metagenomics and 19 samples for metatranscriptomics. Consistent with previous observations, we observed vertical zonation of microbial community structure largely partitioned between light and dark ocean waters. The metabolic pathways inferred from genomic sequence information and gene expression stratified with depth. For example, expression of photosynthetic pathways increased in sunlit waters. Conversely, expression of pathways related to carbon conversion processes, particularly those involving recalcitrant and organic carbon degradation pathways (i.e., oxidation of formaldehyde) increased in dark ocean waters. We also observed correlations between indicator taxa for specific depths with the selective expression of metabolic pathways. For example, SAR202, prevalent in deep waters, was strongly correlated with expression of the methanol oxidation pathway. From a biogeographic perspective, microbial communities along the transect encoded similar metabolic potential with some latitudinal stratification in gene expression. For example, at a station influenced by input from the Amazon River, expression of pathways related to oxidative stress was increased. Finally, when pairing distinct correlations between specific particulate metabolites (e.g., DMSP, AMP and MTA) and both the taxonomic microbial community and metatranscriptomic pathways across depth and space, we were able to observe how changes in the marine metabolite pool may be influenced by microbial function and vice versa. Taken together, these results indicate that marine microbial communities encode a core repertoire of widely distributed metabolic pathways that are differentially regulated along nutrient and energy gradients. Such pathway distribution patterns are consistent with robustness in microbial food webs and indicate a high degree of functional redundancy.
  PubDate: 2022-05-19T00:00:00Z
Functionalization of Frustules of the Diatom Staurosirella pinnata for
Nickel (Ni) Adsorption From Contaminated Aqueous Solutions
- Authors: Saverio Savio, Serena Farrotti, Andrea Di Giulio, Serena De Santis, Neil Thomas William Ellwood, Simona Ceschin, Roberta Congestri
  Abstract: The structural characteristics of diatom cell walls (frustules) has led to their widespread use in diverse biotechnological applications, some of which can be further improved by surface chemical modification (functionalization). The use of coating agents can significantly increase surface binding capacity for target compounds. Frustules of the diatom Staurosirella pinnata used here were a by-product after applying a cascade-extraction process (for other products) to mass cultures. The protocol for the cleaning and functionalization of raw frustules using 3-Mercaptopropyl-trimethoxysilane and 3-Aminopropyl-trimethoxysilane was optimized and reported. Functionalization efficacy was observed using Electron Microscopy, Energy Dispersive X-ray Spectroscopy and Fourier-Transform Infrared Spectroscopy. Optimally functionalized frustules were evaluated for nickel removal from aqueous solutions. Incubations of 10 min, using 1 g/L of frustules, gave almost complete Ni removal with functionalized frustules compared to 3% removal by raw frustules. The proposed protocol represents a reproducible and efficient alternative for Ni removal from contaminated water.
  PubDate: 2022-05-19T00:00:00Z
Data-Driven Modeling of Dissolved Iron in the Global Ocean
- Authors: Yibin Huang, Alessandro Tagliabue, Nicolas Cassar
  Abstract: The importance of dissolved Fe (dFe) in regulating ocean primary production and the carbon cycle is well established. However, the large-scale distribution and temporal dynamics of dFe remain poorly constrained in part due to incomplete observational coverage. In this study, we use a compilation of published dFe observations (n=32,344) with paired environmental predictors from contemporaneous satellite observations and reanalysis products to build a data-driven surface-to-seafloor dFe climatology with 1°×1° resolution using three machine-learning approaches (random forest, supper vector machine and artificial neural network). Among the three approaches, random forest achieves the highest accuracy with overall R2 and root mean standard error of 0.8 and 0.3 nmol L-1, respectively. Using this data-driven climatology, we explore the possible mechanisms governing the dFe distribution at various depth horizons using statistical metrics such as Pearson correlation coefficients and the rank of predictors importance in the model construction. Our results are consistent with the critical role of aeolian iron supply in enriching surface dFe in the low latitude regions and suggest a far-reaching impact of this source at depth. Away from the surface layer, the strong correlation between dFe and apparent oxygen utilization implies that a combination of regeneration, scavenging and large-scale ocean circulation are controlling the interior distribution of dFe, with hydrothermal inputs important in some regions. Finally, our data-driven dFe climatology can be used as an alternative reference to evaluate the performance of ocean biogeochemical models. Overall, the new global scale climatology of dFe achieved in our study is an important step toward improved representation of dFe in the contemporary ocean and may also be used to guide future sampling strategies.
  PubDate: 2022-05-19T00:00:00Z
Temporal Variability of Co-Occurring Calanus finmarchicus and C.
helgolandicus in Skagerrak
- Authors: Tone Falkenhaug, Cecilie Broms, Espen Bagøien, Nikolaos Nikolioudakis
  Abstract: The congeneric copepods Calanus finmarchicus and C. helgolandicus co-occur in the northern North Sea and Skagerrak where they play important roles as prey for higher trophic levels. This study analyses a 26-year time series (1994-2019) with a ~ two-week temporal resolution for Calanus spp. at a fixed monitoring station in Skagerrak, off southern Norway. Seasonal variation, inter-annual variability and long-term trends for the two species were examined. Strong differences in the species-specific seasonality were revealed, with C. finmarchicus dominating in spring and C. helgolandicus in autumn. The seasonal peak of C. finmarchicus was associated with relatively low temperatures (6-8°C) and high chlorophyll a concentration, while C. helgolandicus displayed its seasonal maximum at higher temperatures (11-16°C). C. finmarchicus was found to produce one dominant annual generation (in spring), but two or more generations are considered likely. Contrasting long-term trends in abundances were found for the two species, suggesting that their population sizes were affected by different mechanisms. The abundance of C. helgolandicus showed an increasing trend over the time period studied, apart from the last years. The abundance of C. finmarchicus was more variable and displayed no unidirectional long-term trends over the time series. The study revealed a shift in the phenology of Calanus spp. over the last 25 years at this site. Since 1994 the timing of the annual peaks in both C. finmarchicus and C. helgolandicus have advanced by about one month. Moreover, the seasonal pattern of C. helgolandicus, switched from a unimodal to a bimodal pattern around 2002, with a small additional peak also appearing in spring. The results suggest that the proximity to the Norwegian Trench influences the demography and abundance of C. finmarchicus in this coastal area, both as a gateway for the advective supply, as well as a habitat for local overwintering.
  PubDate: 2022-05-19T00:00:00Z
The Identification of Fish Eggs From Four Economically Important Species
in Guanghai Bay (China)
- Authors: Yan-Jing Zheng, Xiao-Juan Peng, Wei-Xu Cai, Quan-Sheng Lou, Xiang-Li Lyv, Ying-Hua Huang
  Abstract: By far, very few studies have dealt with the ichthyoplankton diversity in Guanghai Bay (China), which is a potential spawning ground for many important fish species. In this study, fish eggs collected in Guanghai Bay were identified through molecular method combined with visual taxonomic method. We employed two mitochondrial gene regions of cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) as genetic markers for species identification. Through sequence identification at NCBI, 121 eggs with overlapping size range and easy to be confused were discriminated as four economically important species: seven as silver sillago Sillago sihama, 48 as black-banded sillago Sillago nigrofasciata, 38 as yellow drum Nibea albiflora, and 28 as Pacific seabream Acanthopagrus pacificus. Phylogenetic analyses showed that these 121 eggs clustered in four groups with strong support. To testify the validity of these identification results, species identification through five BarcodingR package methods was also carried out using sequences of 33 fish specimens as a reference library covering four target species. Finally, a highly consensus of species assignment results was achieved across different methods. Morphological characteristics and detailed photographs for eggs from these four species were supplied here. Eggs of each species are pelagic, round, have a smooth chorion and one single oil globule. Embryonic pigment patterns vary as eggs develop and can be used for species distinguishing. Eggs from S. nigrofasciata and A. pacificus were described for the first time in this study. One simple and accurate method for identifying N. albiflora eggs was additionally provided. Moreover, the morphological differences between two Sillago eggs offered supportive evidence for the recent separation of S. nigrofasciata as a new species from S. sihama. All these results would be critical for the discrimination of eggs from these four species and the estimation for their spawning areas. Meanwhile, our study would contribute to the stock assessment and fishery management in Guanghai Bay.
  PubDate: 2022-05-19T00:00:00Z
Cyclone Impacts on Coral Reef Communities in Southwest Madagascar
- Authors: Amber L. Carter, Hannah Gilchrist, Kyle G. Dexter, Charlie J. Gardner, Charlotte Gough, Steve Rocliffe, A. Meriwether W. Wilson
  Abstract: Tropical cyclones can cause severe destruction of coral reefs with ecological consequences for reef fish communities. Ocean warming is predicted to shorten the return interval for strong tropical cyclones. Understanding the consequences of cyclone impacts on coral reefs is critical to inform local-scale management to support reef resilience and the livelihood security of small-scale fishing communities. Here, we present the first analysis of a tropical cyclone disturbance on coral reefs in Madagascar. We investigate the impact of Cyclone Haruna (category 3 Saffir-Simpson scale) in February 2013 on coral communities, both adults and recruits, and explore the relationship between the severity of cyclone impact with cyclone parameters (wind speed, duration of storm impact and distance from cyclone track) and environmental variables (reef type and reef depth). We use survey data collected as part of a long-term citizen science monitoring programme at 21 coral reef sites between 2012 and 2015 in the Velondriake Locally Managed Marine Area along Madagascar’s southwest coast. Coral cover declined at 19 sites, however damage was spatially heterogeneous ranging from a decrease in coral cover of 1.4% to 45.8%. We found the severity of cyclone damage related to: distance from the cyclone track, duration of cyclone impact and reef depth. The taxonomic and morphological composition of coral communities was significantly different after the cyclone. Notably, there was a decrease in the dominance of branching morphologies, and an increase in the relative abundance of encrusting and massive morphologies. Two years after Cyclone Haruna, mean coral cover had increased and the density of coral recruits increased to above pre-cyclone levels indicating the potential recovery of coral populations. However, recovery to pre-disturbance community composition will likely be hindered by the increasing occurrence of acute and chronic disturbance events.
  PubDate: 2022-05-19T00:00:00Z
Two New Species and One New Genus of Glass Sponges (Hexactinellida:
Euplectellidae and Euretidae), From a Transect on a Seamount in the
Northwestern Pacific Ocean
- Authors: Chengcheng Shen, Hong Cheng, Dongsheng Zhang, Chunsheng Wang
  Abstract: Hexactinellid sponges often form structural habitats for other organisms and thus support high biodiversity. Two representative morphotypes of hexactinellid sponges were sampled by a remotely operated vehicle along a transect (depths of 2377–2758 m) on the Ko-Hakucho Guyot in the northwestern Pacific Ocean, both new to science. One new species, Flavovirens hemiglobus gen. et sp. nov., which is pedunculate and bears the main choanosomal spicules of diactins, is clearly attributed to the euplectellid subfamily Bolosominae. Its set of microscleres present (namely, predominating oxyhexasters and discasters, and rare discohexasters and staurodiscs) characterizes it as a new genus. The other new species, Chonelasma tyloscopulatum sp. nov., which is funnel in form without dichotomous branching tubes or lateral oscula and has firm body walls supported by a three-layered dictyonal framework, is clearly attributed to the euretid genus Chonelasma (subfamily Chonelasmatinae). Its presence of surface pentactins, two types of scopules, and both oxy- and disco-tipped hexasters or hemihexasters as common microscleres, characterizes it as a new species. The placements are also supported by molecular phylogenetic evidence from nuclear 18S rDNA and 28S rDNA, and mitochondrial 16S rDNA and cytochrome c oxidase subunit I (COI) gene. More sampling efforts should be conducted to improve the understanding of the biodiversity of deep-sea seamount sponges.
  PubDate: 2022-05-19T00:00:00Z