Warm Coastal Waters Research Articles

Thermal tolerance, development, and physiological impacts of climate warming on zoea larvae of brachyuran crabs

Predicted effects of increasing ocean temperatures, due anthropogenic climate change, might be more challenging for early life history stages owing to reduced thermal tolerance. Thus, determining species responses to the projected climate warming conditions on marine ecosystems is essential to access their vulnerability. Here, we experimentally evaluated the effect of increased temperature on larval survival, development time and metabolic responses of two intertidal crab species (Menippe nodifrons and Ucides cordatus). The metabolic rate (measured as oxygen consumption), ammonia excretion and heartbeat rates were measured in standard fashion way, while the coefficient of temperature was obtained as a measure of organism's sensitivity to temperature increase. Critical thermal maximum and minimum, and thermal safety margins were also obtained. The results indicate a decrease in survival probability and development time for both species, from zoea I to zoea III stage, which was seen in higher extent to larvae of M. nodifrons. There is no significant effect of temperature increase on heartbeats and ammonia excretion rates to both species; however, increases in temperature had a differential effect on metabolic responses of two species. In addition, the critical thermal limits for the larval phase were described for the first time, suggesting that larvae of M. nodifrons are more vulnerable and have lower acclimation capacity to warming waters. Although a high sensitivity in metabolism was seen in U. cordatus, this species demonstrates higher thermal tolerance accompanied by a greater physiological plasticity. Our data emphasize that warming of coastal waters may reduce the larval survival and development time of both species, which can potentially impact its distribution and population size.

The surging cholera epidemic in Africa: a review of the current epidemiology, challenges and strategies for control

Africa, a known region with abundant warm coastal waters and a natural reservoir for Vibrio cholera, is known to bear the highest burden of cholera morbidity and mortality globally. Malawi is currently experiencing the deadliest cholera outbreak in two decades, and neighbouring countries, Mozambique and Zambia, have also reported significant numbers of cases. If the current trend of cholera transmission is sustained, the number of fatalities recorded in 2021, Africa’s deadliest year for cholera over the past decade, might be exceeded. This article aims to review the current epidemiology, prevention and control strategies, and treatment of cholera in Africa to highlight context-specific challenges and recommend possible solutions. The authors found out that cholera outbreaks in Africa are taking place in the midst of epidemics (measles, mumps, etc.) and natural disasters like cyclones and flooding (Mozambique, Malawi), drought (Kenya, and Ethiopia), and conflict (Cameroon, the DR Congo, Nigeria, and Ethiopia). The shortages of medical supplies like cholera kits and oral cholera vaccines in many countries due to constrained and limited resources and antibiotic resistance further make management and control difficult. The outbreak is spreading throughout the region because of poor sanitation, unsafe water supplies, and increased cross-border travel. Cholera in Africa follows a seasonal pattern, suggesting specific periods for heightened outbreak preparedness and response. The authors suggest a targeted multisectorial approach and a coordinated mechanism to respond to the epidemic through sustained political will, formidable partnerships, resource mobilisation, and the provision of technical support and advocacy at sub-national, national, and international levels.

Histological study of seventeen organs from dugong (Dugong dugon).

Dugongs are marine mammals with a crescent-shaped tail fluke and a concave trailing margin that belong to the family Dugongidae., They are distributed widely in the warm coastal waters of the Indo-Pacific region. Importantly, the population of dugongs has decreased over the past decades as they have been classified as rare marine mammals. Previous studies have investigated the habitat and genetic diversity of dugongs. However, a comprehensive histological investigation of their tissue has not yet been conducted. This study provides unique insight into the organs of dugongs and compares them with other mammal species. Tissue sections were stained with Harris's hematoxylin and eosin Y. The histological structure of 17 organ tissues obtained from eight systems was included in this study. Tissue sections were obtained from the urinary system (kidney), muscular system (striated skeletal muscle and smooth muscle), cardiovascular system (cardiac muscle (ventricle), coronary artery, and coronary vein), respiratory system (trachea and lung), gastrointestinal system (esophagus, stomach, small intestine, liver, and pancreas), reproductive system (testis), lymphatic system (spleen and thymus), and endocrine system (pancreas). While most structures were similar to those of other mammal species, there were some differences in the tissue sections of dugongs when compared with other mammalian species and manatees. These include the kidneys of dugongs, which were non-lobular and had a smooth, elongated exterior resulting in a long medullary crest, whereas the dugong pyloric epithelium did not have overlying stratified squamous cells and was noticably different from the Florida manatee. Histological information obtained from various organs of the dugong can serve as an essential foundation of basal data for future microanatomical studies. This information can also be used as high-value data in the diagnosis and pathogenesis of sick dugongs or those with an unknown cause of death.

Modeling the risk of Vibrio parahaemolyticus in oysters in Taiwan by considering seasonal variations, time periods, climate change scenarios, and post-harvest interventions

Vibrio parahaemolyticus is a halophilic gram-negative bacterium commonly found in marine environments, particularly in warm coastal waters. This pathogen has been reported as a common cause of foodborne illness associated with the consumption of raw or undercooked seafood. The presence and density of this bacterium in seafood are often associated with the climatological conditions of the marine environment. Herein, we developed the quantitative risk assessment model for Vibrio parahaemolyticus in oysters in Taiwan by considering seasonal variations, time periods, climate change scenarios, and post-harvest interventions. This study showed that season, time period, shared socioeconomic pathway (SSP), and post-harvest intervention significantly influenced the risk level of becoming ill from consuming oysters. The mean estimates of risk in winter, spring, summer, and fall were estimated to be 9.1 × 10−5, 2.0 × 10−3, 2.0 × 10−2, 6.9 × 10−3 per serving, respectively. Our models predict that, if global temperatures continue to increase in the coming decades due to climate change, the risk per serving of oysters is likely to increase by 18-145% by 2041-2060 and by 18-718% by 2081-2100, depending on the season and SSP. The application of thermal processing or high hydrostatic pressure processing was found to be the most effective approach in reducing risk, even under the threat of increasing global temperatures.

How does the Niger river warm coastal waters in the northern Gulf of Guinea?

To highlight the processes by which the Niger River warms the coastal waters in the eastern part of the northern Gulf of Guinea upwelling, two simulations of the NEMO model at high resolution were used over the period 2010 - 2017. The first simulation is realistic while the second is a simulation in which the effects of the Niger River are not taken into account. The first step was to evaluate the outputs of the models, using satellite products and in situ observations. The average states of the Sea Surface Temperature, Salinity, Height, zonal current and vertical profiles of temperature and salinity showed the ability of the model to reproduce correctly the physical characteristics of the study area. The analysis of the heat balance terms of the two simulations showed that vertical diffusion and meridional advection processes are the causes of the warming induced by the Niger River. The stratification and vertical shear of the horizontal currents reveal that the river acts by inhibiting the upwelling of cold water induced by vertical diffusion. The river reinforces the stratification and prevents vertical shearing of horizontal currents at the bottom of the mixed layer.

Tidal effects on periodical variations in the occurrence of singing humpback whales in coastal waters of Chichijima Island, Ogasawara, Japan

Marine organisms inhabiting coastal waters are known to be driven by periodic cycles such as diel, tidal, and seasonal changes. Humpback whales (Megaptera novaeangliae) breed in shallow and warm coastal waters, with males singing complex songs during the breeding season. To investigate periodic variations in humpback whale singing activities, we conducted fixed passive acoustic monitoring in the Ogasawara (Bonin) Islands, Japan, from winter to spring during 2016–2018. The singing activity and individual number of singers were observed throughout the day and night using a very long baseline passive acoustic array. The occurrence of singers peaked before sunrise and in the evening and was reduced during the daytime. The frequency of song reception depended on the tidal phase. A generalised additive model demonstrated that the occurrence of singers increased during the flood tide and decreased during the ebb tide in the waters west of Chichijima Island. These results suggest that the singing behaviour of humpback whales in breeding areas is affected by the diel and tidal cycles. Male humpback whales may change their behaviour or singing location depending on the strength and direction of the tidal current, considering that the selection of a stable location is beneficial for singing whales.

The MCF Toxin of the Extracellular Pathogen Vibrio vulnificus is Activated by and Targets Host GTPases

Vibrio vulnificus (Vv) is a Gram‐negative bacterial pathogen typically found in warm coastal waters. This pathogen causes severe life‐threatening gastrointestinal and wound infections, most commonly from the consumption of contaminated seafood or an exposed wound. Infections progress quickly to sepsis, and death; approximately 90% of patients are hospitalized and >50% die, often as fast as 48 hours after symptom onset. Of concern, the incidence of Vv is increasing, in part due to its expanding geographical distribution caused by climate change.Bacterial pathogens cause debilitating and lethal infections that are often difficult to treat. Understanding how to manage and control the infections they cause is immensely important for improving quality of life and preventing death. The toxins secreted by extracellular bacteria are frequently the primary virulence factors required to either establish colonization, promote maintenance, growth, and/or eventually dissemination. As such bacterial toxins are extremely important in pathogenesis, and they affect and manipulate many host cellular processes.The primary Vv virulence factor associated with sepsis and subsequent death is the composite MARTX toxin. The MARTX toxin is secreted as a single large polypeptide composed of glycine‐rich repeats at both the N‐ and C‐termini between which there are up to five variable effector domains and a cysteine protease domain (CPD). The repeat regions form a pore in the plasma membrane and the effectors and CPD are translocated across. Within the cell, the CPD auto‐cleaves at multiple sites to release each of the arrayed effectors individually into the host cytoplasm. The MARTX toxin thus serves as an effector delivery platform for translocation of multiple toxic virulence factors inside cells as a single bolus.The Makes Caterpillars Floppy‐like (MCF) effector domain is among the most commonly present Vv MARTX effector domains. MCF is unique from most other MARTX domains in that it utilizes its own autoproteolytic activity to activate itself once inside the host cell. MCF autoprocessing requires stimulation by host ARFs, small GTPases that cycle between GDP‐ or GTP‐bound forms and localize to specific subcellular locations. Once auto‐processed, MCF binds phosphatidylinositol‐5‐phosphate (PtdIns5P), a lipid enriched on Golgi membranes, and its exposed N‐terminal glycine is acetylated. Combined, this results in the generation of “active” MCF (aMCF). aMCF induces the intrinsic apoptotic pathway, causes cell rounding, and nuclear fragmentation. Furthermore, aMCF causes vesiculation of the Golgi apparatus, and destroys the mitochondria.Remarkably, while ARF stimulated autoprocessing results in aMCF, ARFs are not the direct target leading to the cytotoxic effects. The biochemical link between the activation of MCF and its cytotoxicity remains unknown. We explore how MCF activation leads to its disruption of host endocytic trafficking proteins. We examine how these proteins may be targeted and modified by MCF. Furthermore, we assess how the disruption of these host proteins ultimately leads to the dissolution of the endomembrane signaling network and the cytotoxicity we observe. This study begins to elucidate the biochemical activity of this important domain and gives insight into how it may promote disease progression. This work will be critical for advancing the understanding how these MARTX toxins function during Vv pathogenesis.

Sewage Promotes Vibrio vulnificus Growth and Alters Gene Transcription in Vibrio vulnificus CMCP6.

ABSTRACTVibrio vulnificus is a naturally occurring, potentially lethal pathogen found in coastal waters, fish, and shellfish. Sewage spills in coastal waters occur when infrastructure fails due to severe storms or age, and may affect bacterial populations by altering nutrient levels. This study investigated effects of sewage on clonal and natural V. vulnificus populations in microcosms. Addition of 1% sewage to estuarine water caused the density of a pure culture of V. vulnificus CMCP6 and a natural V. vulnificus population to increase significantly, by two to three orders of magnitude, whether measured by quantitative PCR (qPCR) or culture and in batch and continuous cultures. Changes in the transcription of six virulence- and survival-associated genes in response to sewage were assessed using continuous culture. Exposure to sewage affected transcription of genes that may be associated with virulence, i.e., it modulated the oxidative stress response by altering superoxide dismutase transcription, significantly increasing sodB transcription while repressing sodA. Sewage also repressed transcription of nptA, which encodes a sodium-phosphate cotransporter. Sewage had no effect on sodC transcription or the putative virulence-associated genes hupA or wza. The effects of environmentally relevant levels of sewage on V. vulnificus populations and gene transcription suggest that sewage spills that impact warm coastal waters could lead to an increased risk of V. vulnificus infections.IMPORTANCE Vibrio vulnificus infections have profound impacts such as limb amputation and death for individuals with predisposing conditions. The warming climate is contributing to rising V. vulnificus prevalence in waters that were previously too cold to support high levels of the pathogen. Climate change is also expected to increase precipitation in many regions, which puts more pressure on wastewater infrastructure and will result in more frequent sewage spills. The finding that 1% wastewater in estuarine water leads to 100 to over 1,000-fold greater V. vulnificus concentrations suggests that human exposure to oysters and estuarine water could have greater health impacts in the future. Further, wastewater had a significant effect on gene transcription and has the potential to affect virulence during the initial environment-to-host transition.

Полихеты рода Pholoe (Polychaeta: Pholoidae) северо-восточной части Баренцева моря

The paper describes species composition, distribution and biology of the polychaeta genus Pholoe in the north-east region of the Barents Sea (between Franz Josef Land and north-west coast of Novaya Zemlya archipelago). One species of the genu s was identified based on the reviewed morphological descriptions – Pholoe assimilis. The highest values of population density (1130 specimens/m2) and biomass (570 mg/m2) were registered in comparatively warm coastal waters of Novaya Zemlya archipelago. Pholoe assimilis’ population size structure based on the dorsal width of the fifth chaetiger was investigated for the first time. Size-frequency histograms indicate presence of at least four size classes.

Prevalence, Genetic Diversity, Antimicrobial Resistance, and Toxigenic Profile of Vibrio vulnificus Isolated from Aquatic Environments in Taiwan.

Vibrio vulnificus is a gram-negative, opportunistic human pathogen associated with life-threatening wound infections and is commonly found in warm coastal marine water environments, globally. In this study, two fishing harbors and three tributaries of the river basin were analyzed for the prevalence of V. vulnificus in the water bodies and shellfish that are under the pressure of external pollutions. The average detection rate of V. vulnificus in the river basins and fishing harbors was 8.3% and 4.2%, respectively, in all seasons. A total of nine strains of V. vulnificus were isolated in pure cultures from 160 samples belonging to river basins and fishing harbors to analyze the antibiotic susceptibility, virulence gene profiles, and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) fingerprinting. All isolates were susceptible to 10 tested antibiotics. The genotypic characterization revealed that 11.1% (n = 1/9) strain was nonvirulent, whereas 88.9% (n = 8/9) isolates were virulent strains, which possessed the four most prevalent toxin genes such as vcgC (88.9%), 16S B (88.9%), vvhA (88.9%), and manIIA (88.9%), followed by nanA (77.8%), CPS1 (66.7), and PRXII (44.4%). Additionally, ERIC-PCR fingerprinting grouped these nine isolates into two main clusters, among which the river basin isolates showed genetically diverse profiles, suggesting multiple sources of V. vulnificus. Ultimately, this study highlighted the virulent strains of V. vulnificus in the coastal aquatic environments of Taiwan, harboring a potential risk of infection to human health through water-borne transmission.

Vibrio vulnificus: Review of Mild to Life-threatening Skin Infections.

Vibrio vulnificus is a motile, gram-negative, halophilic, aquatic bacterium that is part of the normal estuarine microbiome and typically is found in warm coastal waters. Infection with the pathogen typically is due to consumption of contaminated seafood or exposure to contaminated seawater. Vibrio vulnificus has a mortality rate of almost 33% in the United States and is responsible for more than 95% of seafood-related deaths in the United States. Vibrio vulnificus can cause a vast spectrum of diseases, such as gastroenteritis, cellulitis, necrotizing fasciitis, and sepsis. Gastroenteritis is self-limited, whereas septicemia often is fatal. Gastroenteritis and septicemia are caused by ingestion of contaminated shellfish, whereas wound infections and necrotizing fasciitis are caused by exposure to contaminated seawater or handling of contaminated seafood. Septicemia is the most common presentation of V vulnificus and accounts for the most fatalities from the bacteria. Prompt diagnosis and treatment are vital to prevent mortality. It is important to keep V vulnificus on the differential when a patient presents with bullae or cellulitis or has a history of raw seafood consumption or exposure to brackish water, as missing the diagnosis could lead to necrotizing fasciitis, sepsis, and death.

Impact of environmental changes on the fishery of motorized and non-motorized sub-sectors of the upwelling zone of Kerala, southeastern Arabian sea

The marine waters of Kerala state along the southwest coast of India are among the most productive upwelling regions in the southeastern Arabian Sea. Analyses were made to assess the impact of environmental changes on the marine fish catch using motorized and non-motorized craft operating off the coast. The catch per unit effort (CPUE) of total landings, OBGN (outboard gillnet), OBTN (outboard trawlnet), NM (non-motorized) crafts, as well as the catch of 5 major fish resources Indian mackerel, lesser sardines, Stolephorus spp., scads, and penaeid prawns were obtained. Sea surface temperature (SST), chlorophyll, salinity, rainfall, sea level anomaly, multivariate ENSO index, dipole mode index, local temperature anomaly, degree heating month (DHM), degree cooling month (DCM) and surface currents were used as variables to investigate the relationship between environment and fishery. Principal component analysis was used to select the minimum data set and GAM (Generalized additive model) was used to detect the influence of the environment on the fisheries. The adjusted R2 value of the GAM was 0.68, taking the CPUE of the total landings as the response variable. For the case of the selected fish resources, the adjusted R2 value of the GAM was 0.73 for penaeid prawns, followed by Stolephorus spp. (0.44), scads (0.33), lesser sardines (0.31), and Indian mackerel (0.25). Considering the CPUE as the response variable for the GAM also returned high adjusted R2 values for fishing method (OBGN = 0.59, OBTN = 0.53 and NM = 0.31). SST, chlorophyll, rainfall, salinity, yearly DCM and surface currents all had significant influences on the marine fisheries along the Kerala coast. Lower SST, high salinity and rainfall promote the fisheries of both small pelagics and large pelagic groups like scads. Along with the negative relationship between SST and fishery, the present analyses also indicate a positive relationship with yearly DCM, which clearly indicates that the warming of coastal waters has a negative impact on fisheries along the Kerala coast. From these results, we find that ocean currents can play a crucial role in fish recruitment in the coastal waters of Kerala. Primary production, the key factor for marine fishery production, was found to be controlled by environmental factors like SST and currents. These results point to the vulnerability of the small-scale fisheries sector of the tropical upwelling zone to increasing SST and climate change.

Impact of the future coastal water temperature scenarios on the risk of potential growth of pathogenic Vibrio marine bacteria

Vibrio (V) , a genus of marine bacteria, are common inhabitants of warm coastal waters and estuaries. Vibrio includes V. parahaemolyticus and V. vulnificus species that can cause human infections through the consumption of contaminated shellfish (as bivalve molluscs). The growth of pathogenic Vibrio is related to ambient water temperature and seems to increase at 15 °C and over. The expansion of Vibrio infection outbreak is increasing worldwide due to the increase of the sea surface temperature as a result of ocean warming. Canada's coast is not an exception to this worldwide Vibrio spread. Faced with this issue, this study focuses on modelling the future potential Vibrio growth risk along the coasts of the St. Lawrence Gulf and Estuary, where the shellfish industry is well developed. This is done using the adequate machine learning model with explanatory variables that include air temperature and wind speed for predicting future water temperatures. Based on the predicted future water temperature scenarios and a threshold of 15 °C to determine the conditions favorable to the growth of Vibrio bacteria, we modelled the Vibrio growth risk indicator, i.e. the number of days exceeding the minimum temperature for Vibrio pathogenic growth (15 °C), in the horizon 2040–2100. Simulations show that the number of days, where the minimum temperature (15 °C) will be reached, will increase spatially and even seasonally and all the shellfish beds would meet the temperature condition for Vibrio growth regardless of the climate scenario (optimistic and pessimistic). • The statistical modelling of the coastal water temperature from air temperature and wind speed. • Future coastal water temperature scenarios were produced under optimistic and pessimistic climate scenarios. • Maps of the future Vibrio growth risk indicator were produced, from the future water temperature scenarios. • Maps show that the Vibrio growth risk will increase spatially and seasonally regardless the climate change scenario.

Baffin Bay late Neogene palynostratigraphy at Ocean Drilling Program Site 645

Analyses of marine and terrestrial palynomorphs of Ocean Drilling Program (ODP) Site 645 in Baffin Bay led us to define a new biostratigraphical scheme covering the late Miocene to Pleistocene based on dinocyst and acritarch assemblages. Four biozones were defined. The first one, from 438.6 m below sea floor (mbsf) to 388 mbsf, can be assigned a late Miocene to early Pliocene age (>4.5 Ma), based on the common occurrence of Cristadinium diminutivum and Selenopemphix brevispinosa. Biozone 2, spanning from an erosional unconformity to a recovery hiatus, is marked by the highest occurrences (HOs) of Veriplicidium franklinii and Cristadinium diminutivum, which suggest an early Pliocene age >3.6 Ma (∼4.5 to ∼3.6 Ma). Biozone 3, above the recovery hiatus and up to 220.94 mbsf, corresponds to a late Pliocene or early Pleistocene age based on occurrences of Bitectatodinium readwaldii, Cymatiosphaera? icenorum, and Lavradosphaera canalis. Finally, between 266.4 and 120.56 mbsf, Biozone 4, marked by the HO of Filisphaera filifera, Filisphaera microornata, and Habibacysta tectata, has an early Pleistocene age (>1.4 Ma). Our biostratigraphy implies that horizon b1 of the Baffin Bay seismic stratigraphy corresponds to the recovery hiatus at ODP Site 645, which suggests a very thick Pliocene sequence along the Baffin Island slope. Dinocyst assemblages and terrestrial palynomorphs in our records indicate that the late Miocene and (or) early Pliocene were characterized by relatively warm coastal surface waters and boreal forest or forested tundra vegetation over adjacent lands. In contrast, the early Pleistocene dinocyst assemblages above the recovery hiatus indicate cold surface waters, while pollen data suggest reduced vegetation cover on adjacent lands.

Distribution of breeding humpback whale habitats and overlap with cumulative anthropogenic impacts in the Eastern Tropical Atlantic

AbstractAimSpecies distribution modelling is a useful tool for determining important habitats. By accounting for specific animal behaviour in the model, it is possible to identify finer‐scale patterns of habitat use. Together with spatially explicit data on anthropogenic activities, models can be used to assess human impacts and inform conservation management. This study used observations of breeding behaviour to identify fine‐scale breeding habitats of humpback whales (Megaptera novaeangliae), as well as potential overlap of these habitats with cumulative anthropogenic impacts.LocationEastern Tropical Atlantic, West Africa.MethodsMaxent was used to model humpback distribution using pertinent environmental predictors and an integrated dataset of humpback whale occurrences filtered for breeding‐specific behaviours. In conjunction with multiple anthropogenic activities, a subsequent cumulative utilization and impact analysis assessed the degree of overlap between predicted breeding habitat and potential anthropogenic impacts.ResultsGreatest habitat suitability occurred in warm coastal waters of Gabon, and other highly suitable areas occurred off Equatorial Guinea (Bioko Island), Cameroon and Angola. Sea surface temperature and height contributed most to the model. Highest overlap between humpback whales and potential impacts from anthropogenic activities occurred off Gabon, Equatorial Guinea (Bioko Island), Cameroon and Angola. Impacts associated with oil and gas development (where oil and gas platforms serve as an indicator for industry activity) appeared to contribute most to potential cumulative impact.Main ConclusionsDepth and sea surface temperature of predicted breeding habitats were consistent with previous studies. However, lesser known characteristics such as sea surface height and wind speed, resulting in potentially more sheltered areas for breeding whales, may also be important in delineating finer‐scale habitat suitability. Identified areas of high potential cumulative impact occurred within exclusive economic zones of multiple countries and likely represent the minimum level of impact to humpback whales in the region, highlighting the need for additional research and effective management throughout the area.

An Updated View on Water Masses on the pan‐West Greenland Continental Shelf and Their Link to Proglacial Fjords

AbstractThe accelerated melt of the Greenland Ice Sheet has been linked to a sudden increase in the presence of warm subsurface coastal water in west Greenland. Yet pathways of warm coastal water along the entire west Greenland coast have remained largely unstudied. Here we present the first, near‐synoptic hydrographic observations at both the continental slope and fjord entrances of the west Greenland coastal system from Cape Farewell (59°N) to Melville Bay (75°N) in summer 2016. We observed a distinct north‐south division in the water mass distribution in west Greenland, approximately partitioned by the northern part of Davis Strait, and a division between the continental slope and fjord entrances. Waters from the regional southern freshwater source with origin in the East Greenland Current that rounds Cape Farewell are not observed to enter Baffin Bay. The regional heat source transported by the West Greenland Current is blocked by Southwest Greenland Coastal Water in the south but the deep connections in the north allow warm deep Subpolar Mode Water to enter fjords. Furthermore, we observed cold and relative saline Baffin Bay Polar Water over the inner part of the banks, periodically reaching as far south as 64°N, suggesting the presence of an undescribed southward current at the Southwest Greenland continental shelf.

Regional differences in kelp forest interaction chains are influenced by both diffuse and localized stressors

AbstractOn temperate rocky reefs, overexploitation of high‐trophic‐level omnivores can result in the decimation of kelp forest habitats by releasing sea urchin population networks from top‐down control. However, the local dynamics of the resulting trophic cascades are context‐dependent. Here, we investigate the community‐wide patterns associated with both diffuse stressors and localized protection of high‐trophic‐level omnivores in kelp forest ecosystems by comparing communities among marine reserves and fished areas in two contrasting regions in terms of fishing intensity and land‐based stressors, Fiordland and the Marlborough Sounds, New Zealand. We find higher densities of the potential sea urchin predators, red rock lobsters (Jasus edwardsii) and banded wrasse (Notolabrus fucicola), in the Fiordland region, and larger effect sizes of fishing on the exploited fish communities in the Marlborough Sounds. Patterns in sea urchin density were consistent with the idea that high‐trophic‐level species, such as large fish and rock lobsters, regulate sea urchin population density, with lower densities of Evechinus chloroticus observed inside marine reserves, in both regions. Nevertheless, densities of E. chloroticus were generally high (>3 m2) in the Marlborough Sounds, likely above a grazing threshold in both fished and reserve sites. The proportion of habitat where sea urchins were absent was 29% in Marlborough Sounds and 90% in Fiordland. Consequently, we observe 49% barren habitat in Fiordland vs. 70%, and a larger effect of fishing on kelp community structure, in the Marlborough Sounds, where fishing effect sizes and land‐based stressors were more severe. We propose that a combination of diffuse stressors including regional overexploitation of important sea urchin predators, sedimentation, and warming of coastal waters likely contributed to regional differences in the responses of trophic interaction chains to localized reductions in fishing within marine reserves. The present study highlights how physiologically stressed and modified kelp forest ecosystems are more susceptible to detrimental phase shifts at a regional spatial scale.

Calcium-dependent site-switching regulates expression of the atypical iam pilus locus in Vibrio vulnificus.

The opportunistic human pathogen Vibrio vulnificus inhabits warm coastal waters and asymptomatically colonizes seafood, most commonly oysters. We previously characterized an isolate that exhibited greater biofilm formation, aggregation and oyster colonization than its parent. This was due, in part, to the production of a Type IV Tad pilus (Iam). However, the locus lacked key processing and regulatory genes required for pilus production. Here, we identify a pilin peptidase iamP, and LysR-type regulator (LRTR) iamR, that fulfil these roles and show that environmental calcium, which oysters enrich for shell repair and growth, regulates iam expression. The architecture of the iam locus differs from the classical LRTR paradigm and requires an additional promoter to be integrated into the regulatory network. IamR specifically recognized the iamR promoter (PiamR ) and the intergenic iamP-iamA region (PiamP-A ). PiamR exhibited classical negative auto-regulation but, strikingly, IamR inversely regulated the divergent iamP and iamA promoters in a calcium-dependent manner. Moreover, expression of the c-di-GMP and calcium-regulated, biofilm-promoting brp exopolysaccharide was IamA-dependent. These results support a scenario in which the calcium-enriched oyster environment triggers IamP-mediated processing of prepilin amassed in the periplasm for rapid pilin elaboration and subsequent BRP production to promote colonization.

Recent mixing of Vibrio parahaemolyticus populations.

Humans have profoundly affected the ocean environment but little is known about anthropogenic effects on the distribution of microbes. Vibrio parahaemolyticus is found in warm coastal waters and causes gastroenteritis in humans and economically significant disease in shrimps. Based on data from 1103 genomes of environmental and clinical isolates, we show that V. parahaemolyticus is divided into four diverse populations, VppUS1, VppUS2, VppX and VppAsia. The first two are largely restricted to the US and Northern Europe, while the others are found worldwide, with VppAsia making up the great majority of isolates in the seas around Asia. Patterns of diversity within and between the populations are consistent with them having arisen by progressive divergence via genetic drift during geographical isolation. However, we find that there is substantial overlap in their current distribution. These observations can be reconciled without requiring genetic barriers to exchange between populations if long-range dispersal has increased dramatically in the recent past. We found that VppAsia isolates from the US have an average of 1.01% more shared ancestry with VppUS1 and VppUS2 isolates than VppAsia isolates from Asia itself. Based on time calibrated trees of divergence within epidemic lineages, we estimate that recombination affects about 0.017% of the genome per year, implying that the genetic mixture has taken place within the last few decades. These results suggest that human activity, such as shipping, aquatic products trade and increased human migration between continents, are responsible for the change of distribution pattern of this species.

New record of the Critically Endangered striped smooth-hound, Mustelus fasciatus (Garman, 1913) (Chondrichthyes, Triakidae), in the Southwest Atlantic

We report the southernmost known occurrence in the Atlantic Ocean of the striped smooth-hound, Mustelus fasciatus (Garman, 1913). The shark, a female measuring 106 cm TL, was fished in warm coastal waters, with a salinity of 33,189 PSU, of central Argentina (40°52ʹ13ʺ S, 062°18ʹ42ʺ W). This report increases by 205 km southward the known range of this endemic and Critically Endangered species.