The nation’s biggest business lobby, the U.S. Chamber of Commerce, was among the top spenders on Washington lobbying in the second quarter of the year. But the group’s $9 million was a sliver of the $71 million tab it had forked over in one quarter during the height of the health care debate.

From April through June, the chamber lobbied on a number of issues, including pressing for passage of three free-trade agreements and on the implementation of the Dodd-Frank Wall Street Reform and Consumer Protection Act, Internet gambling regulations and the Lawsuit Abuse Reduction Act, according to a recently filed report to Congress under the Lobbying Disclosure Act.

The business organization’s second-quarter number marks a 17 percent decrease from this year’s first quarter, when it reported spending $10.9 million on lobbying. A chamber spokesperson could not be reached for comment by press time.

The chamber wasn’t the second quarter’s only big spender on lobbying.

The chamber’s affiliate Institute for Legal Reform reported $5.6 million. The drug industry’s chief lobbying group, Pharmaceutical Research and Manufacturers of America, posted $4.7 million, up slightly from $4.5 million in the previous period. And AARP, the senior lobby that has been battling deficit reduction proposals to slice Medicare and Social Security, also reported $4.7 million for the quarter, a slight dip from its $5 million for the first quarter.

Some of the more obscure industry groups saw a significant jump in their lobby spending.

The Automotive Aftermarket Industry Association, which represents mechanics who are not affiliated with dealerships, reported spending almost $500,000, up about 150 percent from just less than $200,000 in the first quarter.

Aaron Lowe, the group’s vice president of government affairs, attributed the increase to a “right to repair” bill — legislation that would compel automakers to sell information and tools to repair their vehicles. The federal measure, which has about 23 co-sponsors, appears stalled as Members debate the fiscal crisis, but such a bill is gaining traction in Massachusetts.

“We’re working a lot more on the state level,” Lowe said.

The National Association of Manufacturers, a large K Street lobbying operation, reported a 60 percent downturn in its second-quarter filing. In the first quarter, NAM spent $2.7 million on lobbying, but that fell to $1.1 million for the most recent period. A NAM spokesman did not return a call seeking comment.

The filing deadline for all second-quarter reports was midnight Wednesday.

Alex Knott contributed to this report.