Project Summary​

Ecosystems worldwide maintain equilibrium through a series of checks and balances. In

1960, a team of scientists sought to explain the verdancy of Earth, despite abundant herbivory.

They attributed greenness to trophic cascades ecosystem-wide, predicting top-down linear effects

between trophic levels. However, modern ecology has shown cascading effects across trophic

levels can be multidirectional. While most studies on trophic cascades are conducted locally, the

range of kelp species Macrocystis pyrifera spans continents, offering a unique opportunity to

track fluctuations in trophic cascades within kelp systems over vast latitudinal ranges.

Kelp forests create habitat structure in temperate seas circumglobally, hosting productive

and dynamic communities. These structurally significant brown algae thrive in mid-high

latitudes, where long photo periods facilitate rapid growth, and upwelling replenishes nutrientrich

seawater. Historically, a trophic cascade in NE Pacific kelp forests triggered by the removal

of sea otters results in significant increase of algal grazers (urchins, echinoid species), and

subsequent decrease in kelp. A slow increase in sea otter populations in these regions over the

last century, however, has resulted in fewer algivore urchins and more abundant kelp forests,

demonstrating effective top-down control. This paradigm has been described in Pacific kelp

systems, but while the sea otter’s range does not extend to South America, Macrocystis co-exists

with echinoid grazers throughout Patagonia.