This ran in the NAFF June newsletter and addresses the current algae bloom on the White River in Arkansas.
A few weeks ago NAFF member Bob Waldeck queried Christy Graham, the AGFC Trout Biologist, about the green stuff that is currently making it difficult to fish the White River. Christy agreed to let us print her response.
The vegetation folks are observing on the White River right now is likely Cladophora, a common (native) filamentous green algae. Cladophora generally requires a hard substrate such as cobble or bedrock. It is usually found in water temperatures of 59 to 77 degrees F. It thrives in clear water where sun light can penetrate and we definitely have that here. Additional nutrient inputs (especially phosphorus in freshwater) can stimulate Cladophora production, but heavy blooms of Cladophora have been observed in the absence of additional inputs. With all the rain we have had this spring, it is not too surprising that we’ve had quite a bloom this year as a result of all of the additional nutrients being flushed into the river.
Although heavy flooding can scour Cladophora, somewhat higher sustained flows have been observed to result in increased production. Given this, we suspect that higher water that we have seen in the last couple of years may be part of the puzzle. Not only do the sustained flows continually provide the algae with the materials it needs for growth, it also allows it to establish in the channel margins that are dewatered less frequently.
As I’m sure you know, invertebrates will feed on the Cladophora and it can also serve as habitat for them. From our observations, the bugs and other food items for trout generally do well in the Cladophora, although it can make it more difficult for the trout (especially the rainbows) to get at them. However, your report is the second I have heard that sculpin seem to be trapped in the algae. It makes me curious as to what could be happening. I would think it has more to do with variability in flows recently and less to do with the algae itself.
Perhaps those areas became dewatered for a short time with the recent happenings of minimum flow. Regardless of why it happened, I’m afraid I don’t know if there is anything we can do to alleviate that issue. As you have experienced, the biggest impact so far is to the anglers, as the stuff can foul their lines.