Published on July 18th, 2011 | by Michael Ricciardi1
As Arctic Ice Shrinks, Pacific Species Invade Atlantic, Causing Ecological ‘Tumult’
The largest species invasion in over 2 million years is now underway as Arctic ice cover melts and shrinks, permitting a freer exchange of species between the Pacific and Atlantic Oceans; dire and dramatic consequences for Atlantic biodiversity are predicted.
From microscopic plants and jellyfish to predatory packs of Orcas and soon-to-be-arriving squid…The “alien” invasion of the Atlantic ocean by Pacific Ocean species is fully underway, all made possible by ever-decreasing Arctic sea ice cover.
It is now accepted that oceanic and atmospheric warming is causing the Arctic ice sheet to steadily shrink, accelerated by loss of ice albedo (reflectivity of light off ice); Arctic ice cover has become so fragmented and sparse in some areas that, for the first time in centuries, an “ice-free” Northwest Passage was possible during winter. This summer’s ice-cover is at it smallest extent in centuries, if not millennia.
But humans aren’t the only ones who like a short-cut and a new frontier; many native Pacific ocean species are making the trip across the pole and finding food and habitat in the Atlantic.
At-sea observations indicate that large numbers of Orca (“killer”) whales have been making the crossing since at least 2007. This invasion of highly-skilled, predatory whales is have a dramatic impact on populations and defensive behaviors of other trans-Arctic whale species, such as the Pacific gray, beluga and narwhal.
This blog writer reported on gray whales starting to cross the Arctic over a year ago. This new migratory behavior (gray whales would normally travel far south, around Cape Horn) was made possible by receding ice cover; loss of Arctic ice cover permits northern whale migration as there is plenty of open sea in which to surface and breath. At that time, the concern was about increased shipping posing a hazard to migrating gray whales. Now, it seems, the grays have to face a double threat: one from ship propellers and the other from their fellow “invaders”: groups of killer whales.
For other, smaller species like Arctic cod and char, the threat is in the form of competition over food, as east-moving schools of foraging capelin out-compete the char for the same types of food. Marine scientist warn of further threats to cod that come from warming waters, and, less saline water (due to ice melting into the sea) will generally result in fewer fish species overall.
And Humboldt squid — normally found off the coast of Chile – recently have been found in colder Alaskan waters, and they are predicted to make it across the Arctic into the Atlantic perhaps within another year.
News of this current “invasion” has been spreading since the publication of a report by the research project called CLAMER (Climate Change & European Marine Ecosystem Research). CLAMER is a collaboration of 17 marine institutes in 10 European countries.
Ocean ecosystems will surely be altered, over time, by all of this inter-mixing and struggling for survival. Food chains will reach critical points as, for example, copepods — tiny, nutritious crustaceans that are eaten by many smaller fish species — are out-competed and replaced by smaller, less nutritious invaders, altering the size and nutrient value of the fish that eat them. It is believed that such shifts in zooplanktonic nutrition can result in the collapse of larger fish stocks.
Such a case is currently happening with the copepod Calanus finmarchicus (a crucial source of oil for many fish) which is being replaced by Pacific varieties that are smaller and less nutritious. Copepods are a main food source for krill which are the primary food source for many marine animals, including emperor penguins and many whale species.
According to the Marine Board of the European Science Foundation:
“In the North Sea, seasonal changes in the timing of biological events for plankton as a response to warming are leading to a mismatch between phytoplankton and zooplankton, between zooplankton and fish, between bivalve larvae and shrimp, and between fish and seabirds.”
When a fish stock collapses, the result is a loss of an ecosystem service — and often the means of survival or livelihood of numerous humans who depend on it. The complete loss of such an ecosystem service could take many decades, or as short as a year of two.
As evolution proceeds in fits and starts, and in the meantime, invasive species also take a more immediate economic toll, proving very costly in unexpected ways. Recently, huge hordes of a poisonous jellyfish (Pelagia noctiluca) have clogged up the water intake valves of a sea-side nuclear power plants in Scotland and Israel.
An earlier warning sign of ecological trouble brewing occurred in November 21, 2007, when a 10-square-mile (26 km2) swarm of jellyfish (numbering billions of individuals) decimated a 100,000-fish salmon farm in Northern Ireland, with over a £1 million in losses.
The increase in jellyfish “swarms” has been attributed to a decrease in jellyfish competitors and predators. This decline, in turn, is linked to ocean acidification* (from excess CO2 forming carbonic acid in water) which prevents smaller creatures from forming their calcium-carbonate skeletons (a problem with many coral species in particular), critically damaging the food source for smaller prey fish that the big fish depend on. But most jellyfish are immune to acidification and move into areas that the bigger fish have left and quickly increase in numbers.
Ocean bio-chemistry and ecology is complex stuff.
One of the first clues that a massive invasion was underway was the discovery on the Atlantic east coast of a microscopic plant (phytoplankton) species named Neodenticula seminae, which was only found in the Pacific, and hadn’t inhabited the Atlantic for 800, 000 years, according to the fossil record.
This discovery represents “”the first evidence of a trans-Arctic migration in modern times” related to plankton, according to the UK-based Sir Alister Hardy Foundation for Ocean Science. The foundation also warns that “such a geographical shift could transform the biodiversity and functioning of the Arctic and North Atlantic marine ecosystems.” The foundation is documenting this current planktonic shift as part of its Continuous Plankton Recorder Survey, the longest and most geographically extensive marine biological survey in the world.
Of course, the invasion can work in both directions.
This massive, natural invasion is being described by some researchers as the “largest species invasion in the last 2 million years.” For the past 2 million years, the polar ice cap has been an effective barrier to Pacific-Atlantic species mixing. Now, as East-West/West-East shipping lanes across the Arctic expand, and ice-sheet extent continues to fluctuate generally downward, more species invasions will occur, as these same ships bring plankton and other hitch-hiker species along with them.
Another consequence of warming oceans is the diminishing of water-column mixing; as our seas grow more stratified (layered), less nutrient mixing occurs, and this can lead to large accumulations or “blobs” of marine “mucilage” (a mixture of living and dead organic matter) that serve as habitat for bacteria and viruses, but which can be fatal to fish. A similar phenomenon seems to be happening currently in the Mediterranean Sea.
As climate warming impacts continue to manifest most starkly at the planetary poles, and increasingly in our oceans, a massive West-meets-East, ecological experiment is being conducted…Just one of many ecological upheavals due to anthropogenic climate change.
Stay tuned, friends, it won’t be the last you’ll hear of this.
Some material for this article came from the National Post article ‘Pacific species migrating through warmer Northwest Passage’ by Tristan Hopper and the Telegraph (UK) article ‘Warming oceans cause largest movement of marine species in two million years’ by Richard Gray
photo: (copepod) Uwe Kils ; CC – By – SA 3.0