Saturday, September 7, 2013

Deep ocean canyons around Hawai`i are hot spots for species diversity

Often science simply confirms what you’d suspect. Example: Life is more interesting in a complicated landscape than a simple one.

(Image: Some of the canyons off Kane`ohe Bay. Credit: UH Mānoa.)

Case in point: You get more life and more kinds of life in the wrinkled landscape of Hawaiian undersea canyons than on the broad flats. 
University of Hawai`i marine researchers determined that biodiversity is significantly higher in the submarine canyons around Hawai`i than on the flats, largely because the canyons provide so many more types of habitat, but also because they concentrate nutrients.

The researchers reported in the journal Deep Sea Research Part II after 34 dives with the submersibles Pisces IV and V up and down the archipelago, from the main Hawaiian Islands to the Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands. 

Their dives took them to study points at multiple depths, the deepest of them near a mile down. The principal researcher was UH oceanography professor Craig Smith.

In the canyons, they found both complexity of habit an increased biodiversity. 

 “Submarine canyons encompass myriad habitat types. This heterogeneity at the landscape-scale helps to enhance local biodiversity in canyon seafloor sediments,” said lead author Fabio C. De Leo, a doctoral graduate from UH Mānoa’s department of oceanography. Species diversity is considerably higher in canyons, he said.

In canyons, many things are happening. There are diverse physical habitats. Ocean currents are channeled. Sinking particles are captured. Too, a lot of the organic material washed off the islands ends up settling in canyons, where they decompose and add nutrients to a portion of the ocean normally limited in food availability. 

“When there’s more food, there’s more life,” De Leo said.

Says the University press release: “This series of dives was conducted on the Pisces IV and Pisces V manned submersibles operated by the Hawai‘i Undersea Research Laboratory (HURL).  The research was conducted in partnership with Hawai‘i Pacific University and the New Zealand National Institute of Water and Atmospheric Research.”

Here is the citation: Fabio C. De Leo, E.W. Vetter, C. R. Smith, A. R. Ashley, and M. McGranaghan.  Spatial scale-dependent habitat heterogeneity influences submarine canyon macrofaunal abundance and diversity off the Main and Northwest Hawaiian Islands.  Deep Sea Research Part II: Topical Studies in Oceanography.  11 July 2013.

© Jan TenBruggencate 2013

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