Husna, Amity University Kolkata
Marine biological invasion is the process by which a foreign species gets introduced to a new environment where it can negatively alter and invade the native species. One of the major challenges is to understand the cause of spatial variation in biological invasions across local-to-global scales. “What makes a successful invasion?”, “Is a particular geographic location more vulnerable to invasion than others?”are some of the questions we come across while discussing biological invasions. For over a century, the Panama Canal has connected water bodies that have different evolutionary histories. This greatly reduced the transit time for ships going between the Atlantic and Pacific oceans which created a global shipping hotspot. However, the opening of the canal increased invasion or the spread of introduced species, which can destroy the natural habitat of the area where they get introduced. The Canal between the Pacific and the Atlantic Ocean is fed by freshwater rivers that empty through the locks on each end which is a system that can prevent the fish and smaller marine invertebrates from hopping from ocean to ocean, but even then, some manage to get through, by clinging to the hulls of ships. Other invading species arrive from far-flung ports when the ships prepare for transit.
Are Marine invasions asymmetrical in tropical oceans?
Recently, a test was done between two tropical oceans at similar latitudes to detect asymmetry in the extent of marine invasions and predation effect which is a possible mechanism of biotic resistance. The marine biologists of Smithsonian Environmental Research Centre (SERC) tested predictions about biological invasions in Panama and their results are published in companion papers in the journal Ecology. The non-native species (NNS) richness was estimated using standardized field surveys, to examine whether invasions are asymmetrical when more non-native species are present in the less diverse Pacific compared to the more diverse Atlantic and to examine whether predation can limit the abundance and distribution of these invertebrates between oceans.
To find this out, they suspended PVC panels in the water at 10 different sites of the Panama Canal which worked as habitat patches for colonization. Then they waited for 3 months so that those marine invertebrates could colonize the panels. Lastly, they removed these standard collectors, photographed the results and identified the species by classifying them as either native, non-native, or species of unknown origin.
They found more non-native species in Pacific, there were 18 non-native species which comprised 30% of all the Pacific species, than in the Atlantic where there were 11 non-native species, 13% of all the Atlantic species. They found eight times more non-native species from the Pacific than from the Atlantic in this area. Also, there was a higher influx of invaders from the Atlantic to the Pacific. Along the way, they also reported 7 new non-native sessile invertebrates in the Atlantic and 9 in the Pacific, which were previously unknown from these areas. One of the most important contributions of this project was a collaboration with the Panama Canal Authority and the Panama Maritime Authority, they created an online database of non-native species as part of the National Estuarine and Marine Exotic Species Information System (NEMESIS) called Pan-NEMO.
How important are predators to keep a check on the marine invaders?
It was also experimentally tested to know if marine invaders are equally successful in all environments and how important predators are to keep them in check. Hence, they looked for evidence of biotic resistance following the idea that in biodiverse environments, it is harder for invaders to succeed because they have to compete with the natives and survive along with the native predators. After the test, they found out that predation substantially reduced biomass and changed the composition of non-native species in the Pacific, but not on the Atlantic coast. Some of the dominant non-native species were particularly susceptible to predation in the Pacific which supports the hypothesis that predation reduces the abundance of certain non-native species. Hence, predators are a critical component of marine ecosystems, particularly in the tropics as they can limit the abundance of introduced invader species. By protecting the predators, you can protect the world’s oceans from invasions by species that can alter the balance of marine ecosystems. Healthy ecosystems must resist invasions.
In conclusion, along with global efforts to reduce organism transfers by ships, conservation of native predator populations also plays a very critical role in biosecurity to prevent new invasions.
Also read: The invention of an improved Nanotech OLED electrode
Sources:
- Biologists discover that more intense predation in the tropics can limit marine invasions by Smithsonian Tropical Research Institute (2021, June 26) retrieved 28 June 2021 from https://phys.org/news/2021-06-biologists-intense-predation-tropics-limit.html
- Mark E Torchin, Amy L Freestone, Linda McCann, Kristen Larson, Carmen Schlöder, Brian P Steves, Paul Fofonoff, Michele Repetto, Gregory M Ruiz. Asymmetry of marine invasions across tropical oceans. (2021,06 11), doi:10.1002/ecy.3434
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