How warming west coast waters have altered the marine ecosystem



And so “the Blob”, as oceanographers have dubbed this immense expanse of warm water, was born.

This fall 2014 satellite image shows the early days of the Blob, where the red colors represent unusually warm water temperatures. [Image: NOAA/Wikimedia Commons]

Interestingly, a number of species have moved north to places along the west coast of the United States where the water was previously too cold for them.

We are a marine evolutionary biologist and one marine ecologist, and are currently studying these recent arrivals on the northern California coast. Through our work, we hope to understand what made it possible for species not only to move with the Blob, but to persist after the water cooled.

Many species have established new populations far north of their historical limits, as shown in this graph where light colored bars show previous range limits and darker colors show new range extensions. distribution. [Image: Erica Nielsen/Sam Walkes: CC BY-ND]

Cooling temperatures

Many species that arrived with the Blob did not stay in the colder northern waters after the heat wave passed. For example, open water species like the common dolphin followed the warm waters of the north, then migrated south after the waters cooled. But many coastal species are sessile, which means they are stuck to rocks for their entire adult life. But these species are not attached to rocks when they are young. During the early larval stages, they straddle ocean currents and can travel tens of kilometers to find new coasts to live on.

The warm waters and changing currents of the Blob have allowed the larvae of many species to move well beyond their northern limits while remaining within their environmental comfort zone. However, when the sea heat wave ended, the real test of survival began.

Our team followed these northern coastal populations to see which species persisted after the Blob. Each year our team returns to the cold, wave-battered coasts of northern California to monitor existing populations and search for new recruits, young individuals who have survived their larval stage and successfully settled on the rocks. .

Every year we are delighted to find new recruits of barnacles, snails and slugs. Of 37 coastal species our team followed, at least five maintained small but stable northern populations after the warm waters of the Blob disappeared.

Who goes from the tourist from the north to the local?

In addition to monitoring populations, our team also collects ecological and evolutionary information on these species. The giant owl’s limpet is one of the species that has persisted, and we want to identify the traits that helped it survive after the Blob ended.

In general, traits that help a species settle into a new environment include the ability to grow and reproduce faster, choose suitable habitats, defend territories, or have more offspring. To test some of these ideas, our team is conducting ecological experiments along the California coast, and we are recording the growth of over 2,500 individual limpets each year. We also experimentally contrast juvenile limpets with larger adults and other competing limpet species. We hope this work will reveal whether the new limpets on the block can grow quickly while competing with the rest.

Owl limpets [Photo: Flickr user Jerry Kirkhart]

But ecology is only half the story of extending the range. Along with ecological experiments, our laboratory is the sequencing of owl limpet genomes to identify genes that potentially code for traits like faster growth or competitive prowess. It is possible to understand at the genetic level what allows certain species to survive.

Conserve Changing Species in a Changing Ocean

Given the effects of ongoing climate change, it’s good news that species can move to follow their preferred climate. It is important to note that while species that move due to climate change are not invasive, these changes can modify existing ecosystems. For example, the Hilton Nudibranch, a predatory sea slug, expanded north during the Blob, resulting in a decline of local nudibranchs.

Research shows that marine heat waves are more and more frequent thanks to climate change. By understanding the ecological and evolutionary attributes that allowed certain species to survive and even thrive during and after the Blob, we may be able to predict what will allow species to develop further in future marine heatwaves.



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