Last September, high phosphorous levels led to a sudden algae bloom in Lake Auburn that killed about 200 trout. It is likely that heavy rainfall and erosion washed the phosphorous into the lake, where higher-than-usual temperatures spurred the growth of the plant, which pulls oxygen from the water as it decays, suffocating the fish.

The event shows just how quickly lake water quality can deteriorate, and highlights the factors, along with development, that are threatening one of the state’s chief economic and environmental resources.

A report issued earlier this week by the Natural Resources Council of Maine criticizes the LePage administration and the Department of Environmental Protection for cuts in staffing and funding for lake protection. A spokeswoman for the department calls parts of the report “factually incorrect” and “out of context.”

It’s clear, however, that under LePage, the DEP has changed direction. The governor has characterized Maine regulations as skewing so far in favor of environmental concerns that they are unduly detrimental to business concerns.

In some cases, he is right, while in others the governor is just advancing a political agenda.

The health of Maine’s lakes should not be a partisan issue. Policy decisions should be based on science, and the science shows that the regulations designed to protect lakes work when they are enforced.

It also shows that even Maine’s largely pristine lakes are not immune to the mounting challenges facing them, and that diligent oversight is needed to slow their decline.

Starting with the implementation of shoreland zoning laws in the early 1970s, Maine held a solid record for protecting its lakes, especially when judged against its New England counterparts. In fact, a recent study by the Vermont Department of Environmental Conservation recommends that state adopt policies similar to Maine’s.

Our state has a high number of clear, healthy lakes, watched over by strong local associations, backed by the support and resources of the DEP. The rocky ocean shoreline may get more attention, but impact of the inland waters should not be discounted — lakes generate an estimated $3.5 billion per year and sustain 52,000 jobs.

But the challenges are immense. The housing boom of a decade ago took away natural protections and increased the amount of sediment and pollutants that gets washed into lakes. Erosion has increased, temperatures are rising, and storms are getting worse.

The impact can be measured. A study by the University of Maine showed that lake water clarity, particularly in the northeastern and western lake regions, decreased consistently from 2005 to 2010.

Likewise, the Bridgton-based Lakes Environmental Association said a quarter of the 38 lakes it monitors have declined in water quality in the last 10 years. The rest have stayed the same, the group said, while none has improved. The Belgrade Lakes Association reports a similar, slow decline.

Meanwhile, oversight of the kind of actions that contribute to the reduction in quality appears to be falling off under LePage. The council’s report says a number of vacant positions have gone unfilled, and the Lakes Environmental Association says the low staffing levels have hindered enforcement of shoreland zoning and stormwater regulations.

Water quality deteriorates slowly, but the most noticeable changes come all of a sudden, and often too late for quick fixes. In light of the report, the DEP needs to reaffirm its commitment to Maine’s lakes, and show how it will help reverse their decline.