Associated Press

Coral reef fish take note of what others are eating, a behavior that can affect sensitive reef environments. Scientists from the University of California-Davis and Princeton studied fish grazing around coral reefs in French Polynesia and found that fish decide to feed on algae if they see lots of other fish in the same place. But if there aren't any other fish nearby, they take it as a sign that predators are close and avoid that section of the reef.

Why it matters: Fish keep the growth of algae, which can harm coral reefs, in check. Overfishing threatens that balance not just because there are simply less fish consuming algae but because fish interpret the presence of fewer fish as a risk when there may not be one. The researchers suggest the newly-revealed link between the social interactions of fish and how food and energy flow through the reef should inform how these sensitive environments, distressed by climate change, are managed.

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5 mins ago - World

Trump announces new Iran sanctions in effort to maintain international arms embargo

Photo: Anna Moneymaker-Pool/Getty Images

President Trump signed an executive order on Monday that would impose sanctions on any person or entity that contributes to the supply, sale, or transfer of conventional arms to or from Iran or is engaged in providing training and financial support related to those weapons.

Why it matters: The executive order is the first step by the Trump administration to put teeth into its claim that international sanctions on Iran were restored over the weekend, one month after the U.S. initiated the "snapback" process under a United Nations Security Council resolution.

Exclusive: Conservative group launches $2M Supreme Court ad

Screengrab of ad, courtesy of Judicial Crisis Network.

The Judicial Crisis Network is launching a $2.2 million ad campaign to put pressure on vulnerable Senate Republicans in battleground states to support a quick confirmation when President Trump announces his Supreme Court nominee.

The big picture: "Follow Precedent," previewed by Axios, is one of the first national and cable television ads to run following Justice Ruth Bader Ginsberg's death Friday.

Updated 20 mins ago - Politics & Policy

CDC says it mistakenly published guidance about COVID-19 spreading through air

CDC Director Robert Redfield. Photo: Anna Moneymaker/Pool/Getty Images

The CDC has removed new guidance that acknowledged airborne transmission of the coronavirus, posting in a note on its website that the guidance was only a draft and had been published in error.

Why it matters: The initial update — which was little noticed until a CNN story was published Sunday — had come months after scientists pushed for the agency to acknowledge the disease was transmissible through the air. The CDC previously said that close person-to-person contact was the bigger concern, and the language has been changed back to erase the warning about airborne transmission.