Scientists call them “SAV,” submerged aquatic vegetation, for short, but they include the elegant, slim-bladed eelgrass, the fluffy coontail grass, wild celery and horned pondweed.

Long-term compensation points in waterstargrass (Heteranthera dubia (Jacq.) Mac M), coontail (Ceratophyllum demersum L.), and duckweed (Lemna minor L.) were near 2-3% full sunlight during a 28-day ...