guest post by Orlan Celestial
Ships are known as vectors of non-indigenous species. A ship is like a vehicle that can let you hitchhike when you are stranded in the middle of nowhere, offering a free ride going to a place where you want to be. But instead of sitting at the back seat of the vehicle, the non-indigenous species take the hull of the ship or the ballast tanks to hitchhike to a new environment where they can invade and dominate.
Invasive alien species (IAS) are organisms that are not native to an area that have been introduced either intentionally or accidentally. When we think about IAS, the ideas that commonly pop in our minds are large invasive organisms such as cane toads, golden apple snails, Burmese pythons, crown-of-thorns starfish, lionfish, mahogany trees, and other worse known invasive species found in every country. These organisms were introduced then eventually became invasive via different pathways such as the illegal pet trade, plant poaching, intentional introduction as biocontrol, and the underrated way of introduction of some alien species, through ships. Studies have confirmed that ships can transport and disperse non-indigenous species including marine microbes, plants, and animals, particularly biofouling organisms such as mussels and barnacles (Butrón et al., 2011; Sarinas et al., 2014; Nacorda et al., 2018). The problem of biofouling organisms can be easily solved by direct removal and cleaning of the ship hauls. But how about our tiny but potentially deadly problem? Now let’s magnify our discussion and focus on our microscopic dilemma before it becomes macroscopic and uncontrollable.
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| (Releasing of ballast water. Photo from Ocean Science and Technology) |
Taking in and discharging ballast waters is a common practice of ships to have proper stability during a voyage. This practice is perceived as a long-standing environmental concern that needs to be effectively addressed as soon as possible. Loaded seawater from the point of origin is transported to a specific destination around the globe. Along with this ballast water are the organisms who hitchhiked and set to invade new areas (Carney et al., 2017). What organisms are commonly transported by ballast waters and why it is considered a threat not just for the environment but as well as for the country’s economy and human health?
The species composition and diversity of organisms found in the ballast water of the ships have been determined through numerous studies. The composition includes microscopic plants or phytoplankton, microscopic animals or zooplankton, and bacteria. For instance, the recent study of Cabrini and colleagues (2018) identified the organisms found in ballast waters in the inter-islands and international ships docked in the Adriatic ports. They also determined the viability of these organisms when introduced to a new environment. They found out that the ship ballast waters contained a high abundance of viable organisms. The hitchhikers included 82 zooplankton taxa wherein 6 taxa are non-indigenous, 141 phytoplankton taxa wherein 6 taxa are potentially harmful and toxic (e.g. Alexandrium minutum, a species of dinoflagellates that can cause red tides), Escherichia coli, and suspected enterococci bacteria. They also noted that water salinity, temperature, and light availability can affect the survival of these organisms during the voyage. Their data provide evidence for the viability of the harmful hitchhikers despite changes in the environment, suggesting that these viable organisms could potentially survive, invade, and dominate the new areas after being discharged. Their presence can eventually affect or disrupt the present communities, especially if they can successfully reproduce. In addition, harmful bacteria or viruses that can be carried along can cause spread of diseases to aquaculture or even in humans.
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(Photomicrograph of potentially harmful phytoplankton Pseudo-nitzchia sp. |
The questions are: how can we prevent this invasion? Do we have existing actions or programs regarding the management of these ballast waters? Fortunately, there are existing programs in place, however, it seems that these are not effective enough to really prevent or stop the introduction of non-indigenous species. Ships, unlike human drivers, cannot just ignore the thumb-up hitchhiking gesture or the signage that says “anywhere but here” or “to the great beyond”. Ships really do need ballast water to operate and they have certain standards and procedures to follow. The International Convention for the Control and Management of Ship’s Ballast Water and Sediments was established as one of the global responses against the introduction of invasive species via ballast tanks adopted by the International Maritime Organization (IMO). Ballast Water Exchange (BWE) is one of the standards in the management program included in the treaty, where ships must exchange ballast water in deep seas and away from coastal areas and estuaries. Another standard includes the installation of an on-board ballast water treatment system which can determine the maximum allowed discharged volume of viable organisms, including specified indicator microbes harmful to human health. The BWE is presently the most commonly implemented standard, especially in older ships, however, it is expected that all new ships should comply with the latter standard that involves the installation of devices and equipment for biomonitoring and treatment of the ballast tanks (IMO, 2021).
Nonetheless, results from several studies show that BWE practice cannot really help prevent the spread of harmful hitchhikers. Although there are other proposed ballast water management strategies including mechanical treatments such as filtration and separation, sterilization methods, and chemical treatments (IMO, 2021), we should still keep planning and creating more effective strategies that would prevent the spread of IAS through ballast waters.
The Philippines as one of the maritime countries also follows the ballast water management program, however, only a few studies have been conducted to investigate the species present in the international and local ships as well as species released in the Philippine oceanic waters (Sarinas et al., 2014). Hence, it is highly encouraged to conduct studies to address this emerging environmental concern.
As the world economy continues to grow, seaborne trades also tend to intensify leading to more and intensified environmental concerns. Therefore, the protection and conservation of our environment, particularly our seas and its indigenous communities should be put on our top priority list. We should make plans and establish strategies that can prevent these hitchhikers from invading and dominating our seas, and exterminate these aliens once and for all!
About the author: Orlan “OG” Celestial is an MSc Biology student at the University of the Philippines Visayas. His research interest is mainly about plankton diversity and ecology. He is an outgoing person. He likes hiking and going outdoors with friends and meeting new people along with it. As a biologist, he likes animals more than plants. His ultimate dreams are to become a Veterinary Doctor, a licensed scuba diver, and a NatGeo Explorer.
Blog owner's note: As a culminating activity to my MS Biology class in Biogeography, I asked my students to write a blog post on a topic in biogeography. We welcome constructive comments on this student piece.
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