Ship Ballast Water Research Articles

Application of a hydroxyl-radical-based disinfection system for ballast water

A hydroxyl radical (OH) ballast water treatment system (BWTS) was developed and applied to inactivate entrained organisms in a 10,000-ton oceanic ship, where OH was produced by a strong ionization discharge combined with a water jet cavitation effect. The calculated OH generation rate was 1373.4 μM min−1 in ballast water, which is much higher than that in other advanced oxidative processes such as photocatalysis. As a result, non-indigenous red tide algae were inactivated to meet the ballast water discharge standards (<10 cells mL−1) of the International Maritime Organization. The ratio of variable fluorescence to maximum fluorescence (Fv/Fm) for algal chlorophyll rapidly decreased to zero within a contact time of only 6 s, indicating complete inactivation of algae. Observation under a scanning electron microscope showed no cellular materials were released by algal cells upon OH inactivation. A risk assessment of the OH treatment system was conducted, and the ratios of predicted environmental concentrations to predicted no effect concentrations of all detected disinfection byproducts were less than 1, even at a worst-case oxidant concentration of 2.41 mg L−1. Ship ballast water treated using OH inactivation is safe for marine environments. Finally, the energy consumption and operational costs of the OH BWTS were found to be 0.033 kWh m−3 and CNY 0.03 m-3, respectively.

Simulation experiments to elucidate variable fluorescence as a potential proxy for bulk microalgal viability from natural water, sediments and biofilms: Implication in ships ballast water management

The variable fluorescence fluorometry measuring microalgal biomass (initial fluorescence - F0, a chl-a proxy) and photosynthetic efficiency (Fv/Fm) has been suggested as a potential tool in ballast-water assessment. In ballast tank, microalgae can be found in contiguous compartments i.e., in water, sediment, and biofilms. Therefore the utility of F0 and Fv/Fm depends upon proper background corrections, which is straightforward for water samples but not for sediment and biofilms. This study proposes procedures for correcting F0 values from sediment and biofilms. Irrespective of the saturation flash protocol used on any sample types the outcome of the results from viable and non-viable microalgae will remain same. Stress experiments (continuous darkness and biocide treatments) confirm that variable fluorescence (Fv) can be used as a potential proxy for viable cells as the values were negligible for non-viable cells and increased with an increase in abundance. Through this study, the utility of Fv and σPSII (functional-absorption-cross-section of photosystem II) along with F0 and Fv/Fm in providing additional information on cell-viability and algal-size group during assessment is discussed. The findings will have implications not only from the perspective of ballast water but also in testing/assays of specific interest (e.g. toxicity, water treatments, antifouling) and ecological studies involving microalgae.

Inactivation of marine heterotrophic bacteria in ballast water by an Electrochemical Advanced Oxidation Process

Seawater treatment is increasingly required due to industrial activities that use substantial volumes of seawater in their processes. The shipping industry and the associated management of a ship's ballast water are currently considered a global challenge for the seas. Related to that, the suitability of an Electrochemical Advanced Oxidation Process (EAOP) with Boron Doped Diamond (BDD) electrodes has been assessed on a laboratory scale for the disinfection of seawater. This technology can produce both reactive oxygen species and chlorine species (especially in seawater) that are responsible for inactivation. The EAOP was applied in a continuous-flow regime with real seawater. Natural marine heterotrophic bacteria (MHB) were used as an indicator of disinfection efficiency. A biphasic inactivation kinetic model was fitted on experimental points, achieving 4-Log reductions at 0.019 Ah L−1. By assessing regrowth after treatment, results suggest that higher bacterial damages result from the EAOP when it is compared to chlorination. Furthermore, several issues lacking fundamental understanding were investigated such as recolonization capacity or bacterial community dynamics. It was concluded that, despite disinfection processes being effective, there is not only a possibility for regrowth after treatment but also a change on bacterial population diversity produced by the treatment. Finally, energy consumption was estimated and indicated that 0.264 kWh·m−3 are needed for 4.8-Log reductions of MHB; otherwise, with 0.035 kWh·m−3, less disinfection efficiency can be obtained (2.2-Log red). However, with a residual oxidant in the solution, total inactivation can be achieved in three days.

Presence and Composition of Planktons’ Organisms in Ships Ballast Water Discharged in Al-Mukalla Harbor, Gulf of Aden

This was the first study in Yemen, and Gulf of Aden aims to investigate the marine organisms in ballast water and sediments, and gives baseline information defines the zooplankton, phytoplankton and invertebrates, associated fuel tankers. Samples from Ballast water were taken from three ships that arrived at Mukalla Port, the Hadhramout coast from ports of Hamriyah port, U.A.E; ports of Taheri, Iran; and Bosaso Somalia (MT: Gulf Petroleum III, MT: Prime Royal, and M T: Breu) respectively. The marine organisms in samples were presented by three taxonomic groups, phytoplankton, zooplankton and benthos. Fifty-eight taxa were identified within this study; which consisted of 17 phytoplankton, 18 zooplanktons and 23 Benthos. The highest density of phytoplankton was 21 Ind/L, with the occurrence of 17 species found in ballast water, while 22 Ind/50cc of 2 species in sediment samples of the tanker Beru, and fewer densities were in Gulf Petroleum and Prim Royal. The most common phytoplankton observed were Coscinodiscus granii, Coscinodiscus jonesianus and Thalassiosira eccentric. The low Zooplankton density was 13 Ind/L with an occurrence of 18 species found in Prim Royal tanker. Copepods were the most dominant zooplankton among the three tankers. Paracalanus parvus had the highest value of dominance followed by Calanopia parathompsoni, Acrocalanus gracilis and Paracalanus denudatus had the lowest occurrence over three tankers. Seven taxa of Dinoflagellates were identified; two of them Ceratium fusus and polykrikos sp. are known to be harmful species.

Detection of viability of micro-algae cells by optofluidic hologram pattern.

A rapid detection of micro-algae activity is critical for analysis of ship ballast water. A new method for detecting micro-algae activity based on lens-free optofluidic holographic imaging is presented in this paper. A compact lens-free optofluidic holographic imaging device was developed. This device is mainly composed of a light source, a small through-hole, a light propagation module, a microfluidic chip, and an image acquisition and processing module. The excited light from the light source passes through a small hole to reach the surface of the micro-algae cells in the microfluidic chip, and a holographic image is formed by the diffraction light of surface of micro-algae cells. The relation between the characteristics in the hologram pattern and the activity of micro-algae cells was investigated by using this device. The characteristics of the hologram pattern were extracted to represent the activity of micro-algae cells. To demonstrate the accuracy of the presented method and device, four species of micro-algae cells were employed as the test samples and the comparison experiments between the alive and dead cells of four species of micro-algae were conducted. The results show that the developed method and device can determine live/dead microalgae cells accurately.

7. Examining the Impacts of Zebra Mussels as an Invasive Species in the Great Lakes Region and the Role of Stakeholders in Effective Mitigation Strategies

Zebra mussels were first introduced into the Great Lakes region in 1988, via the ballast water of international ships traveling through the St. Lawrence River. Since then, the aggressive colonization of zebra mussels have had devastating effects on the native aquatic biodiversity in the Great Lakes region. The continued proliferation of zebra mussels have led to increased filtering, high light transmittance through water and growth of benthic (lowest level of a body of water) plants. Due to the intensive filtration of zebra mussels, rapid bioaccumulation of botulinum toxin in their systems have caused high levels of mortality for waterfowl predators. As zebra mussels continue to dominate in predator-prey interactions and interspecies competition, a shift in the ecosystem equilibrium is occurring on varying trophic levels. These changes have not gone unnoticed. Zebra mussels have cost Canadian industries, businesses and communities over $5 billion in a single decade in clogged pipes and turbine damages. The associated economic repercussions from infrastructural damages and native species declines necessitate engagement from a multitude of stakeholders. Public awareness is absolutely vital in minimizing the impact of zebra mussels and preventing their distribution across freshwater in North America. In this presentation, I will discuss the ecological, economic and societal impacts of zebra mussels since their introduction to the Great Lakes region. In addition, I will examine a multitude of management strategies and recommendations to government, private sector and public stakeholders to reduce future impacts of mussels in the Great Lakes region.

Tracing the introduction history of the invasive swimming crab Charybdis hellerii (A. Milne-Edwards, 1867) in the Western Atlantic: evidences of high genetic diversity and multiple introductions

The swimming crab Charybdis hellerii is an invader with global distribution in warm waters. Native to the Indo-Pacific, this species invaded the eastern Mediterranean Sea after the Suez Canal opening. In 1987, it was first reported in the Western Atlantic, probably transported via ballast water of ships. Since then, it has been registered from many localities along the American coast from the USA to southern Brazil where it has rapidly established reproducing populations. Our main aim was to investigate the introduction history of this species along the American coast, using a phylogeographic approach. Additionally, we attempted to clarify the identity of this invasive species by molecular analyses and morphological assessment in order to provide a basis for our main investigation. C. hellerii was confirmed as a single species, but both cytochrome c oxidase subunit I and 16S rDNA revealed a genetic structure, splitting the potential source populations of American introductions into two groups: “western Indian Ocean and Mediterranean Sea” (WIO + MS) versus “eastern Indian + western Pacific oceans” (EIO + WPO). Most specimens from America clustered with the former group, supporting the hypothesis that the Mediterranean Sea represented the main source of Western Atlantic populations. However, the clustering of animals from southern Brazil with the latter group indicates that introductions from the eastern Indian or Pacific oceans must also have occurred. The existence of a third group, found exclusively within the American range and genetically related to EIO + WPO, also indicates an independent introduction from an unsampled locality from the native range. The haplotype and nucleotide diversities of American localities were comparable to those of source populations, contradicting a founder effect prediction. This finding might be related to the high propagule pressure associated with introductions via ballast water and the occurrence of multiple introductions from genetic distinct sources. The direct comparison of the haplotype numbers suggested no genetic bottleneck during introduction from the Mediterranean Sea, but a bottleneck might have occurred during introductions from the eastern Indian or Pacific oceans.

A Changeable Lab-on-a-Chip Detector for Marine Nonindigenous Microorganisms in Ship's Ballast Water.

The spread and invasion of many nonindigenous species in the ship’s ballast water around the world has been a hazard and threat to ecology, economy, and human health. The rapid and accurate detection of marine invasive species in ship’s ballast water is essential. This article is aimed at analysing ballast water quality by means of a changeable microfluidic chip detector thus comply with the D-2 standard of ship’s ballast water management and sediment convention. The detection system was designed through the integration of microfluidic chip technology, the impedance pulse sensing and LED light induced chlorophyll fluorescence (LED-LICF) detection. This system can measure the number, size, shape, and volume of targeted microorganisms, and it can also determine the chlorophyll fluorescence intensity, which is an important factor in analysing the activity of phytoplankton. The targeted samples were Chlorella volutis, Dunaliella salina, Platymonas subcordiformis, Chrysophytes, Escherichia coli, and Enterococci. The whole detection or operation can be accomplished through online detection in a few minutes with using micron volume of the sample solution. The valid data outputs are simultaneously displayed in terms of both impedance pulse amplitudes and fluorescent intensity signals. The detection system is designed for multi-sizes real time detection through changing the microchannel sizes on the microfluidic chip. Because it can successfully detect the label-free microorganisms, the system can be applicable to in-situ detections with some modifications to the system.

Setting-up a billboard of marine invasive species in the ESENIAS area

In this study we present a list of invasive/potential invasive alien species in the East and South European Network for Invasive Alien Species (ESENIAS) countries with marine borders. The species were classified according to the existing literature and experts’ judgment, as established, casual, invasive and expected. Finally, factsheets were compiled for ten species of high importance based on their expanding/invading character. Of the 160 species comprising the list, 149 were already present in the ESENIAS countries, while eleven were invasive species either present in the Mediterranean or in other European Seas, likely to be recorded in the ESENIAS countries. The majority of the species were of Red Sea/IndoPacific origin (97 species; 60.6%). Italy, Turkey and Greece were the countries with the highest representation of species (159, 152 and 139 species respectively), due to their extended coastline and the number of scholars working on marine invasive species. The highest number of established species was recorded in Turkey (116 species), whereas in Italy and Greece the most numerous species were the “expected” ones (85 and 48 species, respectively). The eastern Adriatic Sea countries (i.e. Albania, Croatia, Montenegro and Slovenia) had generally low numbers of species in this list, many of which are still “expected” to arrive from the neighbouring countries of Greece and Italy. Finally, the most frequently potential pathway was transfer stowaways (ship ballast water: 41 cases; ship hull fouling: 55), whereas unaided spread of Lessepsian immigrants followed (95 cases). This list is intended to serve as an early warning system that through horizon scanning process would assist ESENIAS countries to prioritise invasive alien species, their pathways and the areas of higher likelihood to appear, in order to take management measures.

Introduction of a new Indo-Pacific marine cladoceran to the Mediterranean Sea

Pleopis schmackeri, a podonid cladoceran not previously recorded in the Mediterranean Sea, was found in the İskenderun Bay for the first time. The samples were collected seasonally during 2012–2015 in the coastal area of İskenderun Bay using a WP-2 zooplankton net (200 µm). Six cladoceran species were found in total, and Penilia avirostris, Pseudevadne tergestina and Evadne spinifera constituted the bulk of the population, while the contribution of P. schmackeri was very low. Although only a single individual was observed in July 2012, the abundance and frequency of P. schmackeri increased in the following years, attaining the abundance of 25.10 ind.m-3 in 2015. Thus, P. schmackeri could be considered as established in İskenderun Bay; however, it seems that it did not affect the distribution of other cladoceran species in the area up to now. P. schmackeri could have entered in İskenderun Bay either as Lessepsian migrant or by ballast waters of commercial ships.

INTERTIDAL BARNACLE COMMUNITY OF KETAPANG AND GILIMANUK PORTS THAT SEPARATED BY THE INDONESIAN THROUGHFLOW OF BALI STRAIT

Indonesian Throughflow (ITF) flows from the Pacific Ocean through the western route of Makassar Strait and exit directly to the Indian Ocean through Lombok Strait and Bali Strait or flows eastward through the Banda Sea. Bali Strait separates the Ketapang Ferry Port of Banyuwangi on the Jawa side and Gilimanuk Ferry Port of Bali. Ferries connect Jawa and Bali through those ports as the primary mean of transportation. Ship hull and ballast water of those ships act as a proxy for barnacle distribution in their larval stage from one harbor to another so that it could influence the barnacle community of those two ports. The environmental condition of each seaport defines the barnacle community based on the adaptation ability of barnacle. The purpose of this research was to determine the intertidal barnacle diversity on both Ketapang and Gilimanuk seaports and to compare the barnacle community between Ketapang and Gilimanuk seaports. This study was a survey, and simple random sampling technique was used to collect samples. Sample collection was conducted from July to August 2017, and the sample observation and identification were performed at the Faculty of Agriculture Laboratory at Banyuwangi PGRI University. The diversity indexes including Shannon, Brillouin, Simpson, and Evenness were calculated to determine the level of diversity, and Bray-Curtis similarity coefficient was used to compare the intertidal barnacle community. The result showed the intertidal barnacle diversity of Ketapang and Gilimanuk seaports were low, at the level of 0.89, 0.89, 0.41 and 0.27 at Ketapang Ferry Port and 0.81, 0.80, 0.43, and 0.28 at Gilimanuk Ferry Port based on Shannon, Brillouin, Simpson, and Evenness accordingly. The two ports were having a medium similarity of intertidal barnacle community indicated by the Bray-Curtis similarity coefficient analysis score of 0.58.

Heavy metal levels of ballast waters in commercial ships entering Bushehr port along the Persian Gulf

In this study we report the concentration levels of heavy metals (including Pb, Cd, Hg, Cr, Ni, Fe, Mn, Cu) in ballast water of commercial ships, entering Bushehr port for the first time in the region of the Persian Gulf. The concentration levels of Cu and Fe in all samples of the ballast water were higher compared with the coastal waters of Bushehr port. In the case of Cd, 76.47% of samples had higher concentration level compared with the coastal waters of Bushehr port. Results showed that in a long term the ballast water has the potential to change the chemical quality in marine environments and also may affect the human health and marine ecosystem where ships discharge their ballast water. Therefore, permanent monitoring as well as treatment of ballast water before discharging is crucial to keep the marine environment health.

Non-indigenous species (NIS) of polychaetes (Annelida: Polychaeta) from the Atlantic and Mediterranean coasts of the Iberian Peninsula: an annotated checklist

This study provides an updated catalogue of non-indigenous species (NIS) of polychaetes reported from the continental coasts of the Iberian Peninsula based on the available literature. A list of 23 introduced species were regarded as established and other 11 were reported as casual, with 11 established and nine casual NIS in the Atlantic coast of the studied area and 14 established species and seven casual ones in the Mediterranean side. The most frequent way of transport was shipping (ballast water or hull fouling), which according to literature likely accounted for the introductions of 14 established species and for the presence of another casual one. To a much lesser extent aquaculture (three established and two casual species) and bait importation (one established species) were also recorded, but for a large number of species the translocation pathway was unknown. About 25% of the reported NIS originated in the Warm Western Atlantic region, followed by the Tropical Indo West-Pacific region (18%) and the Warm Eastern Atlantic (12%). In the Mediterranean coast of the Iberian Peninsula, nearly all the reported NIS originated from warm or tropical regions, but less than half of the species recorded from the Atlantic side were native of these areas. The effects of these introductions in native marine fauna are largely unknown, except for one species (Ficopomatus enigmaticus) which was reported to cause serious environmental impacts. In other cases, the displacement of native species or economic damages are suspected.

Assessment of phytoplankton invasion risks in the ballast water of international ships in different growth conditions

The possibility of successful invasion by phytoplankton assemblages in the ballast water of twelve international commercial ships was investigated. Various scenarios of port water dilution rates with a time delay for the exponential growth of the plankton were considered. Most of the phytoplankton in the ballast water samples originated in countries such as Japan and China, and diatoms dominated (&amp;gt;90% abundance) these phytoplankton communities. To assess their survival after discharge in seawater under various conditions, the phytoplankton were reintroduced into ballast water, pier-side water, and nutrient-enriched f/2 medium and incubated at various water temperatures and salinities for 2 weeks. The growth of the invading phytoplankton was influenced by the time delay for regrowth when introduced in the new seawater conditions. The results also suggest that once introduced by ballast water, the growth of a phytoplankton community may depend more on the nutrient levels and the water temperature and less on the salinity. Although we did not consider parameters such as competition with native species and predation, both high nutrient concentrations and water temperatures may significantly shorten the period before exponential growth occurs, which increases the invasion potential.

Study of effectiveness of UV irradiation of single-cellular organisms transported with ballast waters of ships

The technology of seawater decontamination from single-celled organisms with the use of ultraviolet (UV) radiation was investigated to prevent the introduction of alien organisms into local aquatic ecosystems with ballast water (BW) of ships. Experiments were carried out on the effects of low-pressure (LPL) and medium-pressure (MPL) mercury arc lamps on single-celled green algae, halophilic alga Dunaliella terricola and euryhaline alga Asteromonas gracilis, and also on the salt-resistant bacterium Nocardia sp. Doses of UV irradiation were determined for a tenfold decrease in the number of mobile algal cells and colony-forming units of the bacterium. For the first time, differences in the degree of damage with irradiation of LPL and MPL were found by example of the phytoplankton representatives. It was found that, during MPL irradiation, in contrast to LPL, except the cross-linking of the nitrogenous bases of DNA, other mechanisms are involved in the inactivation of microorganisms.

The recent colonization of south Brazil by the Azores chromis Chromis limbata.

The damselfish Chromis limbata is native to the Macaronesian Archipelagos (Azores, Madeira and Canaries) and the western coast of Africa between Senegal and Angola. During the austral summers of 2008 and 2009 the species was recorded for the first time in the south-western Atlantic Ocean around Campeche and Xavier Islands, in Florianópolis, Santa Catarina State, Brazil. Here, the progression of C. limbata in southern Brazilian waters is described using visual counts and genetic surveys and changes in the density of the native congener Chromis multilineata were also investigated. Underwater visual censuses of both Chromis species were carried out from 2009 to 2014. Chromis limbata tissue samples were collected and the mtDNA control region was sequenced and compared with mtDNA haplotypes from the natural range to confirm species identity, compare genetic diversity and to infer connectivity between newly established Brazilian populations. The Brazilian population of C. limbata increased significantly over the past 5 years and the effect on C. multilineata is still an open question, longer time-series data will be necessary to clarify possible interactions. The molecular analyses confirmed species identity, revealed strong haplotype connectivity among Brazilian study sites and showed a low genetic diversity in Brazil when compared with the native populations, suggesting few individuals started the invasion. Four hypotheses could explain this colonizing event: C. limbata was released by aquarium fish keepers; larvae or juveniles were transported via ship ballast water; the species has rafted alongside oil rigs; they crossed the Atlantic Ocean through normal larval dispersal or naturally rafting alongside drifting objects. The rafting hypotheses are favoured, but all four possibilities are plausible and could have happened in combination.

The effects of chemical additives on the production of disinfection byproducts and ecotoxicity in simulated ballast water

The management of ship ballast water is essential to stemming the introduction of non-indigenous species. Approval for onboard installation of a system to treat ballast water requires rigorous land-based testing as dictated in the G8 guideline by the International Maritime Organization. However, this testing lacks standardization—most notably augmentation of organic carbon for influent water by adding chemical additives. Electrochlorination is a popular treatment method for ballast water, in which chlorinated oxidants react with organisms and organic matter in water. The additives could thus affect the treatment efficacy of the ballast water. Here, we examined the effects of several candidates of organic carbon additives on the consumption of total residual oxidant (TRO), the production of disinfection byproducts (DBPs), plankton survival, and ecotoxicity. The TRO consumption over five days of storage was higher in electrochlorinated seawater amended with lignin and Metamucil when compared with seawaters with other organic carbon compounds. DBP production varied by almost two orders of magnitude as a function of the various additives. This was largely attributed to the production of tribromomethane and dibromoacetic acid. The survival of Artemia franciscana was significantly different across waters of different organic carbon additives. Algal toxicity testing with the marine haptophyte Isochrysis galbana significantly reduced growth in lignin- and Metamucil-treated seawaters, but not with other organic carbon compounds. Bioluminescence in Vibrio fischeri sharply declined in electrochlorinated seawaters with all types of organic carbon compounds, but no toxicity was manifested once the electrochlorinated seawaters were neutralized with sodium thiosulfate. The varying degrees of outcome suggest that it might be better to eliminate the requirements of adding organic carbon to test water as long as natural water was used for land-based testing of BWMS. If needed, the additives could be used in proportion to the composition of the organic matter in water being tested.

Only half of the truth: Managing invasive alien species by rapid assessment

Marine environments are threatened by biological invaders that are transported via ship hulls or ballast water at increasing rates around the globe. Most management strategies that should prevent or reduce the impact of alien species include prevention and eradication programs that both rely on an early detection of introduced species. Early detection requires an up to date inventory of present species and efficient monitoring programs to identify newly arrived species. This study surveyed potential invasion ‘hot spots’ in the coastal waters of the central Wadden Sea, including commercial ports (‘port’ stations) as well as fairways, roads, groynes and oyster reefs (‘Wadden Sea’ stations) to establish lists of macrobenthic species as baseline for future monitoring. In the ports we applied simultaneously the HELCOM/OSPAR protocol (H/O) and a regional established rapid assessment (RA) to enable the evaluation of the effectiveness and comprehensiveness of both methods. While the RA is mainly based on the visual screening of species in easy accessible habitats in the field, the H/O includes an extensive sampling by operation of scientific divers boat times and a 4-times higher time effort for sample processing. We identified among all sites 273 species including 37 alien species. The fauna was composed of 210 native and 32 alien species, while the flora was composed of 26 native and 5 alien species. The ports were a diverse habitat with species numbers from 65 to 109. At the Wadden Sea stations, exclusively monitored by the less extensive RA, only half of the species numbers (36–66 species) were detected. However, on the oyster reefs the relative occurrence of alien species compared to natives was similar to the ports and one oyster reef (Nordland) even had the highest ratio (25%, 14 species) of alien species of all investigated sites. The H/O protocol identified 179 species compared to 114 species identified by the RA. Regarding alien species, the H/O provided 85% of alien species, the RA only 67%. Especially with regard to the actual discussion on harmonized monitoring protocols within the Northeast Atlantic and Baltic regions, we recommend that future port surveys should apply the more extensive H/O protocol, since restrictions to the RA decrease drastically the chance of an early detection of alien species. We also recommend complementing the survey of ports with natural invasion ‘hot spots’ like the oyster reefs by rapid assessment. This combined monitoring design secures a significant increase in the early detection of alien species as demonstrated in our study.

Correction to 'A hypervariable mitochondrial protein coding sequence associated with geographical origin in a cosmopolitan bloom-forming alga, Heterosigma akashiwo'.

Geographical distributions of phytoplankton species can be defined by events on both evolutionary time and shorter scales, e.g. recent climate changes. Additionally, modern industrial activity, including the transport of live fish and spat for aquaculture and aquatic microorganisms in ship ballast water, may aid the spread of phytoplankton. Obtaining a reliable marker is key to gaining insight into the phylogeographic history of a species. Here, we report a hypervariable mitochondrial gene in the cosmopolitan bloom-forming alga, Heterosigma akashiwo . We compared the entire mitochondrial genome sequences of seven H. akashiwo strains from Japanese and North American coastal waters and identified a hypervariable segment. The region codes for a hypothetical protein with no defined function, and its variations between Japanese and North American isolates were prominent, while the sequences were more conserved among Japanese strains and North American isolates. Comparison of the sequence in isolates obtained from different geographical points in the Northern Hemisphere revealed that the sequence variations largely correlated with latitude and longitude (i.e. Pacific/Atlantic oceans). Our results demonstrate the usefulness of the sequence in determining the phylogeographic history of H. akashiwo .

Evonik exits ship-water treatment

Evonik Industries will no longer sell peracetic acid-based ship ballast water treatment chemicals. Its dispensing equipment partner TeamTec is withdrawing from the market too. Long-term storage tests under marine conditions raised doubts about the stability of the chemical, sold as Peraclean Ocean, Evonik says. An international treaty ratified in 2016 requires oceangoing vessels to install systems that prevent invasive species from hitching a ride in their ballast water. Other treatment systems rely on onboard sodium hypochlorite generators and ultraviolet light disinfection.