Biological controls on bacterial populations in ballast water during ocean transit

Bacteria (and viruses) numerically dominate ballast water communities, but what controls their population dynamics during transit is largely unexplored. Here, bacterial abundance, net and intrinsic growth rates, and grazing mortality were determined during a trans-Atlantic voyage. The effects of grazing pressure by microzooplankton on heterotrophic bacteria during transit were determined for source port, mid-ocean exchange (MOE), and six-day-old source port ballast water. When the grazer component was removed, bacterial abundances significantly increased. Additionally, we determined that the grazer-mediated mortality for ballast water originating from ports was greater than MOE water and that mortality decreased over time for the source port ballast water. This study shows that bacterial populations in transit are controlled by microzooplankton grazing. If these findings are representative of ballast water environments, they suggest that if the grazing component is selectively removed by various treatment methods, bacterial populations may increase; this could have environmental and human health consequences.     

Ballast water: A threat to the Amazon Basin

Ballast water exchange (BWE) is the most efficient measure to control the invasion of exotic species from ships. This procedure is being used for merchant ships in national and international voyages. The ballast water (BW) salinity is the main parameter to evaluate the efficacy of the mid-ocean ballast water exchange. The vessels must report to the Port State Control (PSC), via ballast water report (BWR), where and how the mid-ocean BWE was performed. This measure allows the PSC to analyze this information before the ship arrives at the port, and to decide whether or not it should berth.Ship BW reporting forms were collected from the Captaincy of Santana and some ships were visited near the Port of Santana, located in Macapá (Amazon River), to evaluate the BW quality onboard. We evaluated data submitted in these BWR forms and concluded that the BWE efficacy might be compromised, because data contained in these BWR indicate that some ships did not change their BW. We found mistakes in filling the BWR forms and lack of information. Moreover, these ships had discharged BW with high level of salinity, Escherichia coli and total coliforms into the Amazon River. We concluded that the authorities of the Amazon Region need to develop more efficient proceedings to evaluate the ballast water reporting forms and BW quality, as there is potential risk of future invasion of exotic species in Brazilian ports.     

Verification of mid-ocean ballast water exchange using naturally occurring coastal tracers

We examined methods for verifying whether or not ships have performed mid-ocean ballast water exchange (BWE) on four commercial vessels operating in the Pacific and Atlantic Oceans. During BWE, a ship replaces the coastal water in its ballast tanks with water drawn from the open ocean, which is considered to harbor fewer organisms capable of establishing in coastal environments. We measured concentrations of several naturally occurring chemical tracers (salinity, six trace elements, colored dissolved organic matter fluorescence and radium isotopes) along ocean transects and in ballast tanks subjected to varying degrees of BWE (0-99%). Many coastal tracers showed significant concentration changes due to BWE, and our ability to detect differences between exchanged and unexchanged ballast tanks was greatest under multivariate analysis. An expanded dataset, which includes additional geographic regions, is now needed to test the generality of our results.     

Changes in zooplankton abundance and diversity after ballast water exchange in regional seas

A study of the efficiency of ballast water exchange (BWE) in regional seas was carried out to assess this management method in reducing the risk of introducing non-native species. Zooplankton samples were taken before and after exchange on ten voyages where BWE took place (North Sea, English Channel, Irish Sea and Bay of Biscay). Zooplankton abundance was always reduced after exchange, but diversity increased on eight occasions. The greatest changes occurred when the source port water was of low salinity and when exchange took place in deeper waters further from land. However, it was clear that BWE did not remove all the source port taxa and this method is unlikely to provide a consistent and effective method of managing ballast water in regional seas.     

Bacteriological examination of ballast water in Singapore Harbour by flow cytometry with FISH

In this study the concentrations of total bacteria, enterobacteria, Vibrio spp., and E. coli have been compared for ballast water samples taken from ships in Singapore Harbour. The cell concentrations were enumerated using FISH and flow cytometry. The data were highly variable, reflecting the many influences upon ballast water as it is utilized in the shipping industry. The concentration of bacterial species was determined as a proportion of the total concentration of cells for the ballast water sampled. For the ballast water sampled these concentrations were 0.67-39.55% for eubacteria, 0-2.46% for enterobacteria, 0.18-35.82% for Vibrio spp., and 0-2.46% for E. coli. Using FISH and flow cytometry, an informative determination of the bacterial hazards of ship ballast water can be made.     

Challenges in global ballast water management

Ballast water management is a complex issue raising the challenge of merging international regulations, ship's specific configurations along with ecological conservation. This complexity is illustrated in this paper by considering ballast water volume, discharge frequency, ship safety and operational issues aligned with regional characteristics to address ecological risk for selected routes. A re-estimation of ballast water volumes gives a global annual level of 3500 Mton. Global ballast water volume discharged into open sea originating from ballast water exchange operations is estimated to approximately 2800 Mton. Risk based decision support systems coupled to databases for different ports and invasive species characteristics and distributions can allow for differentiated treatment levels while maintaining low risk levels. On certain routes, the risk is estimated to be unacceptable and some kind of ballast water treatment or management should be applied.     

Ecosystem under pressure: ballast water discharge into Galveston Bay, Texas (USA) from 2005 to 2010

Ballast water exchange processes facilitate the dispersal and unnatural geographic expansion of phytoplankton, including harmful algal bloom species. From 2005 to 2010, over 45,000 vessels (≈ 8000 annually) travelled across Galveston Bay (Texas, USA) to the deep-water ports of Houston (10th largest in the world), Texas City and Galveston. These vessels (primarily tankers and bulkers) discharged ≈ 1.2 × 10(8) metrictons of ballast water; equivalent to ≈ 3.4% of the total volume of the Bay. Over half of the ballast water discharged had a coastwise origin, 96% being from US waters. Galveston Bay has fewer non-indigenous species but receives a higher volume of ballast water discharge, relative to the highly invaded Chesapeake and San Francisco Bays. Given the magnitude of shipping traffic, the role of Galveston Bay, both as a recipient and donor region of non-indigenous phytoplankton species is discussed here in terms of the invasibility risk to this system by way of ballast water.     

Changes of microbial populations in a ship's ballast water and sediments on a voyage from Japan to Qatar

Colony-forming eutrophic marine microorganisms in ballast water were counted in samples taken on board in 2002 and 2003. In the ballast water in Japan, viable cell numbers were highly variable but not by more than 10(5.1) colony-forming units (CFU)ml(-1) regardless of season. Even when ballast water was discharged offshore, values varied but not by more than 10(5.0) CFUml(-1). The effectiveness of the ballast water exchange was unconfirmed, except for the February 2003 voyage. No microbial colonies were counted in the reloaded ballast water in the high seas on that voyage, which contributed to the reduction of the total number of viable cells sampled in the discharged ballast water at the Ras Laffan port in Qatar. In sediment samples, the values of 10(5.2) - 10(6.0) CFUml(-1) were estimated for all seasons in which voyages took place. The maximum of the marine Vibrio species, 110 CFUml(-1), was observed in the ballast water sample taken in July 2003. The estimated total viable cell numbers in sediments were higher than those counted in the ballast water throughout the experiments, indicating the importance of sediment management as well as ballast water management on vessels traveling from Japan.     

青藏高原湖泊沉积物与水体细菌群落共发生网络和群落构建过程差异解析

研究高原湖泊沉积物和水体细菌群落结构的差异对于水生态治理与保护具有重要的科学意义。本文选取青藏高原中东部共19个湖泊为研究对象,采集沉积物和水体样本,使用高通量测序技术和统计分析,解析湖泊沉积物和水体细菌群落结构、空间分布特征、共发生网络模式、群落构建过程的差异及其原因。研究结果表明沉积物细菌群落alpha多样性指数(Chao1指数、Shannon多样性指数、Faith’s系统发育指数和Pielou均匀度指数)均显著高于水体细菌群落。沉积物和水体细菌的优势门均为Proteobacteria(相对丰度为45.33%和41.77%),而水体细菌群落结构具有较强的空间异质性。主坐标分析和相似性分析结果表明沉积物和水体中细菌群落结构差异极显著,海拔和纬度分别是青藏高原湖泊沉积物和水体细菌群落结构变化最显著的驱动因子。沉积物和水体细菌群落均具有明显的距离衰减模式,而沉积物细菌比水体细菌群落在空间上的周转率小。采样湖泊沉积物细菌群落共发生网络复杂度和稳定性高于水体细菌。沉积物和水体细菌群落的平均归一化随机率值分别为0.24和0.72,表明确定性过程在沉积物细菌群落构建的过程中起到了重要的作用,而水...     

Response of the zooplankton community to extreme hydrological variations in a temporary lake in a neotropical floodplain system

Extreme events can cause species substitution or biodiversity losses. In floodplains, flood and drought phases are considered disturbances when their amplitude or intensity are atypical. These unpredictable events can affect the structure of aquatic communities. In this context, we evaluated the response of the zooplankton community to two extreme droughts that occurred from 2001−2002 and 2014−2016. We assessed species richness and composition on three occasions: before extreme drought (phase 1); during the phase after extreme drought (phase 2) characterized by floods, and lastly, after flood (phase 3), when the fluctuations in water levels in the lowlands stabilized. We hypothesized that (i) zooplankton composition in the lake is distinct in the phases before extreme drought and flood, as the extreme drought event causes changes in the community structure and (ii) after the flood (phase 3), the composition of species in the lake would be more similar to the phase 1, with a large number of species shared in these. Contrary to what we expected, similarity in the species composition of the lake was greater between the phase 1 and phase 2, which may indicate the resilience capacity of the community, through specialized adaptations capable of tolerating extreme. The lowest similarity was observed between the phase 1 and phase 3 and this difference may be a consequence of the dilution effect of the community in the flood (phase 2). Our results suggest that the community structure in the lake can be considered more resilient to extreme drought. We also highlight the importance of the hydrological dynamics of a floodplain for the structure of communities, considering atypical droughts in periods of different climatic events.     

The dilution and dispersion of ballast water discharged into Goderich Harbor

Observations are presented on dilution and dispersion rates of ballast water discharged under normal operational conditions at the semi-enclosed port of Goderich, Ontario. The ballast water was tagged with Rhodamine-WT dye and microscopic magnetically-attractive tracer particles. Maximum concentrations of dye immediately after discharge were diluted to 1-5% of initial ballast tank concentrations, and within 3 days had decreased to less than 0.1% of initial concentrations. Inside the harbor, there was 10-20% of the ballast water still present after 2 days, consistent with a flushing rate of 0.8-1.15 day⁻¹. Magnetic particles were collected up to 7.5 km outside the harbor after one day, consistent with a dilution factor of order 10⁵ outside the harbor. The results of this study are discussed in the context of ballast water discharge standards proposed by the International Maritime Organization to minimize the introduction of aquatic nonindigenous species through ships’ ballast water and sediments.     

Quantifying potential propagule pressure of aquatic invasive species from the commercial shipping industry in Canada

We quantify and compare different measures of potential propagule pressure (PPP) of aquatic invasive species (AIS) from commercial vessels in Canada. We used ship arrivals and ballast water discharge volumes as proxies for PPP from ballast water organisms, and wetted surface area (WSA) as a proxy for hull fouling PPP, to determine their relative contributions to total PPP. For three regions studied, PPP proxies correlated significantly across ports and some vessel categories. Relative contributions of ship arrivals, ballast discharge, and WSAs to PPP, evidenced by non-significant correlations across these measures, varied across regions, ports, vessel types, and seasons. Flow-through (dominant on east and west coasts) and empty-refill (in Great Lakes-St. Lawrence region) were the major ballast water exchange methods employed by the vessels surveyed. These methods have different biological efficacy for AIS removal, influencing PPP. Our study illustrates benefits and limitations of using different PPP proxies to estimate invasion risk.     

Potential risk of harmful algae transport by ballast waters: the case of Bilbao Harbour

Ballast water exchange was measured for the first time in Bilbao Harbour, one of the most active of northern Spain. Between 1997 and 2006, 41,900,980.34 ballast water tn were loaded and 13,272,709 tn were discharged. Bilbao Harbour appears to be mainly a source of ballast water, 90% of which would be discharged in European harbours. We estimated that vessels carrying liquid and solid bulk have higher probabilities of exporting ballast water, whereas those with liquid bulk and containers are more likely to introduce it. From 30 potentially harmful phytoplankton species identified to date near harbour facilities, there would be a high risk of exporting at least Alexandrium minutum, Dinophysis sp., Heterosigma akashiwo, Karlodinium sp., Ostreopsis cf. siamensis, Pfiesteria-like and Prorocentrum minimum. Invasion risk by ballast water was tested by analyzing the response of six strains of H. akashiwo from different geographic areas to varying salinity. Results show that successful growth of foreign strains would be possible.     

Macroalgal survival in ballast water tanks

Despite a large amount of research into invasive species and their introductions, there have been no studies focused on macroalgal transport in ballast water. To address this, we collected replicate samples of ballast water from 12 ships in two Mediterranean harbours (Naples and Salerno). Filtered samples were kept in culture for a month at Mediterranean mean conditions (18 degrees C, 12:12h LD, 60micromol photons m(-2)s(-1)). Fifteen macroalgal taxa were cultured and differed according to the geographic origin of the ballast water. Most of the cultured algae were widely distributed species (e.g. Ulva spp. and Acinetospora-phase). However, Ulva ohnoi Hiraoka and Shimada, described from Japan, was hitherto unknown in the Mediterranean Sea. We show for the first time that ballast water can be an important vector for the transport of microscopic stages of macroalgae and that this can be a vector for the introduction of alien species.     

Phytoplankton distribution and productivity in a highly turbid, tropical coastal system (Bach Dang Estuary, Vietnam)

Phytoplankton diversity, primary and bacterial production, nutrients and metallic contaminants were measured during the wet season (July) and dry season (March) in the Bach Dang Estuary, a sub-estuary of the Red River system, Northern Vietnam. Using canonical correspondence analysis we show that phytoplankton community structure is potentially influenced by both organometallic species (Hg and Sn) and inorganic metal (Hg) concentrations. During March, dissolved methylmercury and inorganic mercury were important factors for determining phytoplankton community composition at most of the stations. In contrast, during July, low salinity phytoplankton community composition was associated with particulate methylmercury concentrations, whereas phytoplankton community composition in the higher salinity stations was more related to dissolved inorganic mercury and dissolved mono and tributyltin concentrations. These results highlight the importance of taking into account factors other than light and nutrients, such as eco-toxic heavy metals, in understanding phytoplankton diversity and activity in estuarine ecosystems.     

Results from the first ballast water sampling study in the Mediterranean Sea - the Port of Koper study

The ongoing transfer of harmful organisms by shipping, especially via ballast water transport, may result in a change of biodiversity, alteration of ecosystems, negative impacts on human health and economic loss. Species introductions which cause irreversible consequences to receiving environments and economies call for particular attention. One critical issue is a need to evaluate the quantities and processes of species introductions. Consequently ballast water was sampled on 15 ships calling at the Port of Koper, Slovenia. This was the first ballast water sampling study in the Mediterranean Sea. This paper summarises the sampling results. Samples were analysed for all types of aquatic organisms including bacteria. The results may be considered as background information for an initial risk assessment of future species introductions - an important tool for the implementation of ballast water management measures.     

Management and environmental risk study of the physicochemical parameters of ballast water

Shipping is a vital industry for the global economy. Stability of ships, provided by ballast water, is a crucial factor for cargo loading and unloading processes. Ballast water treatment has practical significance in terms of environmental issues, ecosystem, and human health, because ships discharge this water into the environment before loading their cargos. This study reviews the common methods for ballast water management – exchange, heating, filtration, ultrasonic treatment, ultraviolet irradiation, chemicals, and gas supersaturation – to select the best one. This study compares water temperature, salinity, dissolved oxygen, polycyclic aromatic hydrocarbons (PAHs), and heavy metals (Co, Cr, Ni, Pb) for ballast tanks of selected ships with the recipient port environment in the Persian Gulf as a case study. The exchange of ballast water in the ocean and/or its treatment on board to prevent inadvertent effects on the environment's physicochemical conditions is related to vessel characteristics, legislation, and the environmental condition. Ecological risk study showed that the salt content in ballast water is close to that of seawater, but the values of Cr (2.1 mg/l) and Ni (0.029 mg/l) in ballast water are higher than those in seawater (1 and 0.004 mg/l, respectively).     

岱海水体及沉积物细菌多样性及群落组成特征

采用高通量测序技术,研究了内蒙古岱海流域入湖河流、湖水及沉积物细菌多样性及群落组成.结果显示,细菌多样性从高到低依次为：沉积物>河流>湖泊.聚类分析表明入湖河流、湖水和沉积物细菌群落可分为明显不同的3支,说明这3种生境中细菌群落结构有较大差异.物种注释结果表明,河流中优势细菌菌群为髌骨细菌(Patescibacteria)、变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteria);湖水中优势细菌菌群为放线菌门(Actinobacteria);而沉积物中优势细菌菌群为变形菌门和绿弯菌门(Chloroflexi).典范对应分析及Monte Carlo检验表明,电导率和悬浮物含量对水体中(河流与湖泊)细菌群落影响显著,二者共解释了细菌群落变化的86.5%;而冗余分析及Monte Carlo检验表明,泥深、磁化率和总有机碳对沉积物中细菌群落影响显著,三者共解释了细菌群落变化的47.9%.近30年来,岱海地区气候变化和人类活动导致湖水咸化,沉积物碳氮指标显著增长.岱海水体及沉积物细菌多样性及群落组成的差异及其主要驱动因...     

Potential microbial bioinvasions via ships' ballast water, sediment, and biofilm

A prominent vector of aquatic invasive species to coastal regions is the discharge of water, sediments, and biofilm from ships' ballast-water tanks. During eight years of studying ships arriving to the lower Chesapeake Bay, we developed an understanding of the mechanisms by which invasive microorganisms might arrive to the region via ships. Within a given ship, habitats included ballast water, unpumpable water and sediment (collectively known as residuals), and biofilms formed on internal surfaces of ballast-water tanks. We sampled 69 vessels arriving from foreign and domestic ports, largely from Western Europe, the Mediterranean region, and the US East and Gulf coasts. All habitats contained bacteria and viruses. By extrapolating the measured concentration of a microbial metric to the estimated volume of ballast water, biofilm, or residual sediment and water within an average vessel, we calculated the potential total number of microorganisms contained by each habitat, thus creating a hierarchy of risk of delivery. The estimated concentration of microorganisms was greatest in ballast water>sediment and water residuals>biofilms. From these results, it is clear microorganisms may be transported within ships in a variety of ways. Using temperature tolerance as a measure of survivability and the temperature difference between ballast-water samples and the water into which the ballast water was discharged, we estimated 56% of microorganisms could survive in the lower Bay. Extrapolated delivery and survival of microorganisms to the Port of Hampton Roads in lower Chesapeake Bay shows on the order of 10(20) microorganisms (6.8 x 10(19) viruses and 3.9 x 10(18) bacteria cells) are discharged annually to the region.