Outside a Brooklyn subway station, many stores were shuttered Tuesday during the normally bustling evening commute hour. Ben Popken / for NBC News

The lengthy shutdown of the New York City subways has drained the lifeblood from hundreds of small businesses that depend on the foot traffic of the 5 million passengers who use the system daily.

Outside the Newkirk Plaza subway stop in Brooklyn, nearly half the 29 shops were closed as the shutdown entered its fourth day, with lights off at a nail salon, hair stylists, 99-cent stores, laundromat, cell-phone store and other shops.

The only activity on the open-air tracks was a small crew walking along the rails noting the fallen branches. With the trains halted, an air of economic uncertainty pervaded, punctuated by the whine of chainsaws clearing the fallen branches and trunks cluttering the area's tree-lined streets.

Just four blocks away, a tree uprooted by the superstorm fell and killed a young couple walking their dog Monday.

At normally bustling Loduca Pizza, directly across from one of the station's two subway exits, a handful of customers ordered slices and traded storm stories.

"As you can see, it's pretty quiet here today," said Daniel Loduca, 20, one of the sons who help's run the family business.

The store didn't lose power and wasn't worried about getting supplies, but about 60 percent of his customers come from the subway, Loduca told NBC News. The shop was only open on Monday for about three hours before lack of business, and the impending storm, led them to shutter early.

Subway service has been halted since Sunday at Newkirk Plaza and hundreds of other subway stations. Ben Popken / for NBC News

Asked if he was worried about the effect of the transportation shutdown, Loduca said with a tight smile, "Any day the subway is closed is a day hurt." At least the situation here wasn't as bad as at the store's Somerset, N.J., location, which lost power and suffered from food spoilage. "Money down the drain," said Loduca.

It's a scene repeated at hundreds of subway stops across the city. The immediate area around subway stops is a prime retail location for the foot traffic it brings.

Several nearly identical bodegas can profitably exist side by side, competing for customers grabbing a snack before or after their train. With the spigot of customers turned off, the businesses suddenly become isolated.

As a result, sales, and spirits, can fall sharply. Some shops remain closed until the money train returns, others try to eke out a bit of revenue regardless.

The Metropolitan Transportation said limited service would resume Thursday -- but not at the Newkirk stop.

At Newkirk Station Wines & Liquors, Nick Correra, 62, bagged bottles and hesitated to put a number on the impact of the subway shutdown. Business was brisk Sunday as shoppers stocked up on supplies before the storm. After the storm it was slower.

"The subway is our lifeblood," he told NBC News. "Most of our business comes from people picking up a bottle of wine on their way home. Now people aren't going to be going to work for a while."

Having just made it through the storm and having managed to open his shop, Correra's focus was on serving his customers and making it through the day.

"Today, being the day after, hard to know what will and won't be. ... It's something we've never experienced before," he said.

Correra had no immediate plans to reduce hours or staffing.

"I don't usually change my setup once I get it going," said Correra, who has owned the store for 32 years. "Six days I can live through."

For others, the shutdown represented opportunity. Several livery cabs, normally only allowed to pick up passengers by arrangement, idled by the entrance to the plaza. A sandwich board for the Marlboro Car Service had materialized on the sidewalk to advertise fares to travelers seeking alternative transportation.

In one sign of the area's resilience, a homeless woman dressed in a patchwork quilt of sewn-together clothes, a regular fixture on the plaza, had already returned to her post atop an overturned milk carton. As darkness and a light rain fell, her cup clinked with coins from a passerby. Though customers might be in short supply at Newkirk Station, charity was not.