(WTNH) _ An invasive algae known as didymo has made it's way into the Connecticut River in Vermont and New Hampshire, and it's creeping south."It grows on the rocks and forms large colonies and in time can take over mile stretches of the river bottom," said Bill Hyatt, an environmentalist from the state Department of Environmental Protection. Hyatt says didymo, or Didymosphenia geminata, is native to Northern Europe, but it's been spreading over the last ten years."Typically it only likes cold clear water but for some reason it's spreading to other places," he said. Environmentalists say that this algae will eventually get to Connecticut, but large bodies of water, like the Connecticut River, aren't the biggest concern. The D.E.P. worries about it being transported from the river into smaller streams and lakes, where it can do the most harm. Didymo will "collect on large parts of the stream bottom and eliminate natural organisms, aquatic flies which is the bottom of the food chain and it'll go all the way up," Hyatt said.The only way to prevent it from spreading is for boaters and anglers to check, clean and dry their boats, weighters and all fishing equipment. It only takes a small amount of this algae to cause big problems."There are certainly people that trailer boats all the way up to Northern Vermont and New Hampshire to go fishing, and they could bring it here tomorrow," Hyatt said.If everyone does their part didymo could be kept at bay for some time.