What: Shares of Vanguard Natural Resources, LLC (NASDAQ:VNR) slumped 14.3% in September. This was despite the fact that the only two news items of note last month relating to the company were both positive. Instead, its units succumbed to another downdraft in the oil price as crude slumped 8.5% for the month.

So what: Instead of focusing on the crude oil negativity, let's focus on the positives. The first one is the fact that Vanguard Natural Resources was added to the Alerian MLP Index, which is the leading gauge of energy master limited partnerships as it tracks the top 50 in the sector. Being added to the index is not only a feather in its cap, but it tends to lead to increased buying as several funds and investors match the index's moves.

In addition to that, the company declared another monthly distribution. That's a big deal these days as several of its peers have recently cut or eliminated their payouts.

Furthermore, while the company didn't have any specific new updates, it has continued to move forward with its acquisitions of two smaller upstream MLPs. The transactions remain on pace to close soon, and would not only increase Vanguard Natural Resources overall scale and reduce its costs, but the transactions would actually improve its credit metrics.

Now what: Despite the overall good news, and clear lack of bad news, Vanguard Natural Resources unit price continues to rise and fall along with the oil price. That correlation isn't likely to cease until there's more clarity in the oil market. In other words, investors should brace themselves for a bumpy ride.

Matt DiLallo has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.